Prevalence and Antimicrobial Resistance of Salmonella Isolated from Meat and Meat Products in Algiers (Algeria)

Abstract

This study was conducted in order to estimate the proportion of raw meat and processed meat products contaminated by Salmonella in the region of Algiers, Algeria, to identify serovars and to determine the antimicrobial resistance patterns of isolates. Out of the total 314 samples (144 of raw red meat and meat products, 128 of raw poultry meat and poultry products, and 42 of processed meat products) collected from various retail outlets, 61 (19.43%) were tested positive for Salmonella. The most significant occurrences were recorded for the categories of red meat (23.61%, n=34) and poultry (17.97%, n=23). Among the 64 isolates recovered, 21 different serovars were identified and two strains were nontypable. The most prevalent serovars were Salmonella Anatum (14.6%, n=9), Salmonella Altona (12.50%, n=8), Salmonella Corvallis (7.81%, n=5), Salmonella Enteritidis (7.81%, n=5), and Salmonella Typhimurium (7.81%, n=5). Sixty-two Salmonella isolates were tested for their susceptibility to 32 selected antimicrobial agents. Fifty-six (90.32%) isolates were resistant to at least one antimicrobial, of which 20 (32.26%) showed multidrug resistance. Resistance to sulphonamides (87.10%, n=54) was the most common. Resistance rates were lower to nalidixic acid (16.13%, n=10), streptomycin (16.13%, n=10), and tetracycline (12.90%, n=8), while resistance to pefloxacin was estimated at 4.84% (n=3). Fourteen different resistance patterns were observed. The “ACSSuT” pentaresistance pattern was observed in three of the Salmonella Typhimurium strains. The obtained results show that these foodstuffs are a potential source of antimicrobial-resistant Salmonella for human infections.

Introduction

N on-typhoidal Salmonella is the leading cause of foodborne diseases, which pose a great problem for agribusiness and medicine in both developing and industrialized countries (Stevens et al., 2006; EFSA, 2007). Human salmonellosis generates huge social and economic losses (Miko et al., 2005). Salmonella is responsible for over 1 billion cases of infection worldwide each year (Humphrey and Jørgensen, 2006). According to the Centers for Disease Control and Prevention (CDC) in United States, there are 1.34 million of cases of disease, 16.430 hospitalizations, and 582 deaths each year. The total annual cost resulting from foodborne Salmonella infections is estimated to be approximately $3.5 billion (Oliveira et al., 2006). According to Humphrey and Jørgensen (2006), an estimated 100,000 cases of Salmonella infection in the United Kingdom every year are indicative of much of Western Europe. The true incidence of salmonellosis in both humans and animals is difficult to evaluate in developing countries because of the lack of epidemiological surveillance systems (Ejeta et al., 2004; Stevens et al., 2006).

The ubiquity of Salmonella isolates makes them a persistent contamination hazard to all raw foods (Bell and Kyriakides, 2002). Those of animal origin, primarily meat and meat products, are often implicated in sporadic cases and outbreaks of human salmonellosis (Zhao et al., 2003; Miko et al., 2005). Salmonella serovars responsible for most reported cases do change over the years and vary by countries (Bell and Kyriakides, 2002).

The most common clinical presentation of Salmonella infection is gastroenteritis with nausea, vomiting, headache, abdominal cramps, diarrhea, and sometimes fever. It is characterized by high morbidity and low mortality except for individuals at risk. In fact, approximately 5–10% of patients develop invasive Salmonella infections, which may progress to bacteremia and serious extragastrointestinal diseases (Yan et al., 2003; Su and Chiu, 2007).

Antimicrobial therapy is usually not indicated; it does not reduce the duration or severity of gastroenteritis, and instead may result in prolonged carriage and emergence of Salmonella-resistant strains. Nevertheless, antimicrobial therapy is used for invasive salmonellosis (Yan et al., 2003, Su and Chiu, 2007) or when immunocompromised persons are affected (Cruchaga et al., 2001).

The widespread use of antimicrobial agents in humans and in intensive animal husbandry would exert a selective pressure and contribute to the emergence of multidrug-resistant strains. This phenomenon of antimicrobial resistance represents a worldwide problem both for veterinary and public health sectors by transfer of resistant strains to humans through the food chain (Cruchaga et al., 2001; Zhao et al., 2003; Bada-Alambedji et al., 2006; Little et al., 2008).

No data on prevalence, distribution of serovars, and antimicrobial resistance of Salmonella in foods of animal origin are yet available at this time in Algeria; only superficial Salmonella contamination in ovine and bovine carcasses sampled from the slaughterhouse has been reported (Nouichi and Hamdi, 2009). The few works undertaken providing data on Salmonella focused on the isolates from clinical or animal sources, particularly from broiler and/or laying-hen flocks (Boudilmi and Chalabi, 1997; Aboun et al., 2003; Elgroud et al., 2009; Ammar et al., 2010; Bouzidi et al., 2012). In other African countries, the prevalence and antimicrobial resistance of Salmonella in various foodstuffs are well documented (Guellouz and Ben Aissa, 1995; Nyeleti et al., 2000; Molla and Mesfin, 2003; Molla et al., 2003; Ejeta et al., 2004; Van Nierop et al., 2005; Bada-Alambedji et al., 2006; Stevens et al., 2006; Ben Aissa et al., 2007).

The main objectives of our study are to (i) assess the status of hygiene in the city's retail outlets by determining the extent of Salmonella contamination in meat and meat products, (ii) identify the most frequently isolated serovars, and (iii) determine resistance patterns that diffuse through these outlets by testing the antimicrobial susceptibility of Salmonella isolates.

Methods

Sample collection

This operation was performed throughout the majority of municipalities in Algiers, in cooperation with the municipal health offices. Between June 2007 and June 2008, 314 samples of raw meat and processed meat products were randomly collected from various retail outlets into sterile collection bags previously labeled. Samples were transported in portable coolers immediately to the laboratory and processed on the same day.

Initially, samples are separated into three categories: (i) raw red meat and meat products samples (45.86%, n=144), i.e., cut bovine meats, cut ovine meats, ground bovine meats, and merguez (traditional Algerian sausage) and merguez fillers; (ii) raw poultry meat and poultry product samples (40.76%, n=128), i.e., preparations for shawarma (sliced turkey meat mounted on a spear), giblets, merguez and merguez fillers, chicken parts, turkey cutlets, and ground turkey meats; and (iii) ready-to-eat processed meat products samples (13.37%, n=42), i.e., delicatessen meats that have undergone heat treatment and delicatessen meats that have undergone processing other than heat treatment (e.g., maturation, desiccation).

Isolation and biochemical identification of Salmonella

Samples were examined according to the NF V08-052 routine method (French Normalization Association) at the Hurbal (Algiers Urban Hygiene) Microbiological Analysis Laboratory. Briefly, 225 mL of buffered peptone water (Institut Pasteur d'Algérie [IPA], Algiers, Algeria) was added to 25 g of sample weighed into a stomacher bag. The whole was homogenized on a stomacher for 2 min and incubated for 16–20 h at 37°C. From this nonselective pre-enrichment, 0.1 mL and 1 mL were, respectively, transferred into 10 mL of Rappaport-Vassiliadis broth (IPA) and 10 mL of selenite cystine broth (IPA), and incubated for 18–24 h at 42°C (Rappaport-Vassiliadis) and at 37°C (selenite cystine). A drop from each selective enrichment broth was streaked onto selective xylose-lysine-deoxycholate and Hektoen agar plates (IPA) and incubated for 24–48 h at 37°C. After purification on nutrient agar (IPA), suspect colonies were further characterized by biochemical tests using, first, traditional galleries (IPA) following standard methods and, then, miniaturized API 20E strips (bioMérieux, Marcy-L'étoile, France) for the only presumptive colonies that exhibited positive reactions to Salmonella on biochemical testing.

Serotyping

Serovar determination was carried out at the Enterobacteria Department of the IPA, by a method based on slide agglutination of pure Salmonella strains, using O-group [OMA, OMB] and H-group antigen-specific antisera (Bio-Rad, Marnes la Coquette, France). All isolates were subjected to a self-agglutination test. Once the antigenic formulae were obtained, the Kauffmann-White scheme was used to name the serovars.

Antimicrobial susceptibility testing

Antimicrobial susceptibility testing, as well as quality control and strains storage were performed at the Enterobacteria Department of the IPA according to the techniques recommended by the World Health Organization (WHO) and adopted as of 1999 by the Algerian Antimicrobial Resistance Network (AARN).

Antimicrobial susceptibility was determined by the disk diffusion method on Muller-Hinton agar (IPA), as described by Kirby-Bauer, in accordance with the guidelines of the Clinical and Laboratory Standards Institute (CLSI).

The 32 antimicrobials listed below were those usually tested under the supervision of the AARN: amoxicillin (25 μg), ampicillin (10 μg), ticarcillin (75 μg), piperacillin (100 μg), mecillinam (10 μg), cefazolin (30 μg), cefoxitin (30 μg), cefuroxime (30 μg), ceftazidime (30 μg), cefotaxime (30 μg), latamoxef (30 μg), cefepime (30 μg), amoxicillin/clavulanate (20 μg/10 μg), aztreonam (30 μg), imipenem (10 μg), kanamycin (30 μg), gentamicin (10 μg), amikacin (30 μg), netilmicin (30 μg), streptomycin (10 μg), nalidixic acid (30 μg), pefloxacin (5 μg), ofloxacin (5 μg), ciprofloxacin (5 μg), sulphonamides (300 μg), trimethoprim (5 μg), trimethoprim/sulfamethoxazole (1.25 μg/23.75 μg), furans (300 μg), chloramphenicol (30 μg), tetracycline (30 μg), colistin (10 μg), and fosfomycin (50 μg; Oxoid, Hampshire, United Kingdom). The inhibition zone diameters were measured after incubation at 37°C for 18–24 h. By comparing our results to critical points, each Salmonella isolate could be presented as being “resistant,” having “intermediate susceptibility,” or being “sensitive” according to the CLSI criteria. Escherichia coli American Type Culture Collection (ATCC) 25922 (Institut Pasteur Paris, France) was used as a reference strain for antimicrobial disk control.

Results

Salmonella prevalence

Contamination rates of meat and meat products with Salmonella are shown in Table 1. Out of the 314 samples analyzed, 64 Salmonella spp. strains were isolated. Sixty-one (19.43%) samples were contaminated by one or more Salmonella. Furthermore, two different serovars were isolated from one sample, while three different serovars were isolated from one other sample. Raw red meat and meat products had the highest prevalence (23.61%), followed by raw poultry meat and poultry products (17.97%) and processed meat products (9.52%).

Table 1.

Prevalence of Salmonella spp. in Meat and Meat Products in Algiers

Food category	No. analyzed	No. positive	Prevalence (%)
Raw red meat and meat products	144	34	23.61
Cut bovine meat	18	1	5.56
Cut ovine meat	7	0	—
Ground bovine meat	48	2	4.17
Merguez^a	62	29	46.77
Merguez fillers	9	2	22.22
Raw poultry meat and poultry products	128	23	17.97
Preparations for shawarma^b	6	2	33.33
Giblets (mainly livers)	7	2	28.57
Merguez^a and merguez fillers	17	4	23.53
Chicken parts (breasts, legs, wings)	35	6	17.14
Turkey cutlets	56	8	14.28
Ground turkey meat	7	1	14.28
Processed meat products	42	4	9.52
Delicatessen which have undergone heat treatment (cahir^c, chicken pâté, corned beef, mortadella)	27	4	14.81
Delicatessen which have undergone other treatments than heat: maturation, desiccation (cured sausage, salami)	15	0	—
Total	314	61	19.43

Algerian sausage, which can be prepared either with ovine, bovine, or poultry meat.

Sliced turkey meat mounted on a spear.

Local pâté prepared mainly with bovine meat.

No., number of samples.

Serovars distribution

Out of the 64 Salmonella strains obtained, 21 different serovars were identified and listed in Table 2. However, two strains isolated from poultry samples and biochemically confirmed Salmonella spp. were nontypable.

Table 2.

Prevalence and Distribution of Salmonella Serovars According to the Different Meat and Meat Products Categories

	Food category
Serovar	Raw red meat: no. (%)	Raw poultry meat: no. (%)	Processed meat products: no. (%)	Total (%)
Salmonella Agona	1 (2.70)	—	—	1 (1.56)
Salmonella Albany	2 (5.40)	—	3 (75)	2 (3.12)
Salmonella Altona	3 (8.11)	2 (8.69)	—	8 (12.50)
Salmonella Anatum	9 (24.32)	—	—	9 (14.06)
Salmonella Corvallis	3 (8.11)	2 (8.69)	—	5 (7.81)
Salmonella Enteritidis	—	5 (21.74)	—	5 (7.81)
Salmonella Hadar	—	1 (4.35)	—	1 (1.56)
Salmonella Heidelberg	—	3 (13.04)	1 (25)	3 (4.69)
Salmonella Indiana	1 (2.70)	1 (4.35)	—	3 (4.69)
Salmonella Infantis	—	1 (4.35)	—	1 (1.56)
Salmonella Kedougou	1 (2.70)	—	—	1 (1.56)
Salmonella Lexington	1 (2.70)	—	—	1 (1.56)
Salmonella Liverpool	—	1 (4.35)	—	1 (1.56)
Salmonella Mbandaka	3 (8.11)	—	—	3 (4.69)
Salmonella Montevideo	4 (10.81)	—	—	4 (6.25)
Salmonella Muenster	3 (8.11)	—	—	3 (4.69)
Salmonella Newport	1 (2.70)	—	—	1 (1.56)
Salmonella Ohio	1 (2.70)	2 (8.69)	—	3 (4.69)
Salmonella Panama	—	1 (4.35)	—	1 (1.56)
Salmonella Typhimurium	4 (10.81)	1 (4.35)	—	5 (7.81)
Salmonella Virchow	—	1 (4.35)	—	1 (1.56)
Nontypable strains	—	2 (8.69)	—	2 (3.12)
Total (%)	37 (57.81)	23 (35.94)	4 (6.25)	64

No., number of Salmonella isolates/serovar.

The predominant serovar over the categories was Salmonella Anatum (14.6%, n=9), followed by Salmonella Altona (12.5%, n=8). Salmonella Anatum isolates were recovered only from red meat samples. This serovar was the most prevalent one (24.32%, n=9) among the 14 identified in this category, followed by Salmonella Montevideo (10.81%, n=4) and Salmonella Typhimurium (10.81%, n=4).

Twelve distinct serovars were identified in poultry samples and their products. The predominant two serovars were Salmonella Enteritidis (21.74%, n=5) and Salmonella Heidelberg (13.04%, n=3). Furthermore, Salmonella Enteritidis, Salmonella Heidelberg, and Salmonella Hadar were often associated with poultry meat category.

In processed meat products, Salmonella was isolated only from delicatessen samples that had undergone heat treatment. Two serovars were found in these ready-to-eat products: Salmonella Altona (75%, n=3) and Salmonella Indiana (25%, n=1).

Antimicrobial resistance patterns

From the total of 62 Salmonella isolates evaluated for resistance against a panel of 32 selected antimicrobial agents, 56 (90.32%) were resistant to at least one antimicrobial. The 20 (32.26%) multidrug-resistant Salmonella isolates (defined as isolates that were resistant to two or more antimicrobial agents) could be assigned to 11 different serovars (Table 3).

Table 3.

Antimicrobial Resistance of Salmonella Isolates from Meat and Meat Products

		Antimicrobial agents ^a															MDR
Serovar	No.	AML	AMP	TIC	PRL	S	NA	PEF	Su	W	SXT	F	C	TE	0	1	2–5	+5
Agona	1	0	0	0	0	0	0	0	1	0	0	0	0	0	0	1	0	0
Albany	2	0	0	0	0	2	2	0	2	0	0	0	0	0	0	0	2	0
Altona	8	0	0	0	0	0	1	0	8	0	0	0	0	0	0	7	1	0
Anatum	9	0	0	0	0	3	0	0	7	1	1	1	0	0	2	4	3	0
Corvallis	5	0	0	0	0	0	0	0	4	0	0	0	0	0	1	4	0	0
Enteritidis	5	0	0	0	0	0	0	0	4	0	0	1	0	0	0	5	0	0
Hadar	1	0	0	0	0	1	1	0	0	0	0	0	0	1	0	0	1	0
Heidelberg	3	0	0	0	0	0	3	2	3	0	0	0	0	1	0	0	3	0
Indiana	3	0	0	0	0	0	0	0	2	2	2	0	0	2	1	0	2	0
Infantis	1	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0	0	0
Kedougou	1	0	0	0	0	0	0	0	1	0	0	0	0	0	0	1	0	0
Lexington	1	0	0	0	0	0	0	0	1	0	0	0	0	0	0	1	0	0
Liverpool	1	0	0	0	0	0	0	0	1	0	0	0	0	0	0	1	0	0
Mbandaka	3	0	0	0	0	0	0	0	3	0	0	0	0	1	0	2	1	0
Montevideo	4	0	0	0	0	0	0	0	4	0	0	0	0	0	0	4	0	0
Muenster	3	0	0	0	0	0	0	0	2	0	0	0	0	0	1	2	0	0
Newport	1	0	0	0	0	0	1	1	1	0	0	0	0	0	0	0	1	0
Ohio	3	0	0	0	0	0	1	0	3	0	0	0	0	0	0	2	1	0
Panama	1	0	0	0	0	1	0	0	1	0	0	0	0	0	0	0	1	0
Typhimurium	5	3	3	3	3	3	1	0	5	0	0	0	3	3	0	1	1	3
Virchow	1	0	0	0	0	0	0	0	1	0	0	0	0	0	0	1	0	0
Total	62	3	3	3	3	10	10	3	54	3	3	2	3	8	6	36	17	3
%		4.84	4.84	4.84	4.84	16.13	16.13	4.84	87.10	4.84	4.84	3.22	4.84	12.90

Only antimicrobials against which Salmonella strains have become resistant are listed.

MDR, multidrug resistance; AML, amoxicillin; AMP, ampicillin; TIC, ticarcillin; PRL, piperacillin; S, streptomycin; NA, nalidixic acid; PEF, pefloxacine; SU, sulphonamides; W, trimethoprim; SXT, trimethoprim/sulfamethoxazole (cotrimoxazole); F, furans; C, chloramphenicol; TE, tetracycline; no., number of Salmonella isolates.

0, Susceptibility; 1, resistance to one antimicrobial; 2–5, resistance to two to five antimicrobials; +5, resistance to more than five antimicrobials.

Most of the isolates (90.32%, n=54) exhibited resistance to sulphonamides, 16.13% (n=10) exhibited resistance to nalidixic acid, 16.13% (n=10) to streptomycin, and 12.90% (n=8) to tetracycline. Less than or equal to levels of resistance (4.48%) were observed for penicillins, pefloxacin, trimethoprim, cotrimoxazole, and chloramphenicol. Only two isolates (n=3.22%) were resistant to furans. All isolates were found to be susceptible to cephalosporins and ciprofloxacin, and six (9.68%) to all tested antimicrobials (Table 3).

Antimicrobial susceptibility test results showed a total of 14 resistance patterns as summarized in Table 4. Multidrug resistance was not solely associated with particular Salmonella serovars as the 20 multidrug-resistant isolates represented 11 different serotypes. One Salmonella Anatum isolate was resistant to four antimicrobials, while Salmonella Enteritidis showed resistance only to sulphonamides. Salmonella Newport and two Salmonella Heidelberg isolates were resistant to pefloxacin. Three Salmonella Typhimurium strains expressed resistance to more than five antimicrobials tested, including the “ACSSuT” pentaresistance pattern. One of these isolates displayed additional resistance to nalidixic acid.

Table 4.

Antimicrobial Resistance Patterns of Isolated Salmonella Serovars

Resistance patterns	No.	Serovar (no.)
Susceptible	6	Salmonella Anatum (2), Salmonella Corvallis (1), Salmonella Indiana (1), Salmonella Infantis (1), Salmonella Muenster (1)
F	1	Salmonella Enteritidis (1)
Su	35	Salmonella Agona (1), Salmonella Altona (7), Salmonella Anatum (4), Salmonella Corvallis (4), Salmonella Enteritidis (4), Salmonella Kedougou (1), Salmonella Lexington (1), Salmonella Liverpool (1), Salmonella Mbandaka (2), Salmonella Montevideo (4), Salmonella Muenster (2), Salmonella Ohio (2), Salmonella Typhimurium (1), Salmonella Virchow (1)
Su TE	1	Salmonella Mbandaka (1)
NA Su	2	Salmonella Altona (1), Salmonella Ohio (1)
S Su	3	Salmonella Anatum (1), Salmonella Panama (1), Salmonella Typhimurium (1)
S NA Su	2	Salmonella Albany (2)
S Su F	1	Salmonella Anatum (1)
S NA TE	1	Salmonella Hadar (1)
NA Su TE	1	Salmonella Heidelberg (1)
NA PEF Su	3	Salmonella Heidelberg (2), Salmonella Newport (1)
S Su W SXT	1	Salmonella Anatum (1)
Su W SXT TE	2	Salmonella Indiana (2)
AML AMP TIC PRL S Su C TE	2	Salmonella Typhimurium (2)
AML AMP TIC PRL S NA Su C TE	1	Salmonella Typhimurium (1)

No., number of isolates; AML, amoxicillin; AMP, ampicillin; TIC, ticarcillin; PRL, piperacillin; S, streptomycin; NA, nalidixic acid; PEF, pefloxacine; SU, sulphonamides; W, trimethoprim; SXT, trimethoprim/sulfamethoxazole (cotrimoxazole); F, furans; C, chloramphenicol; TE, tetracycline.

Discussion

Isolated Salmonella prevalence

Meat processing and production systems facilitate the presence of Salmonella in the final product. The overall prevalence of Salmonella contamination of raw meat and processed meat products (19.43%) observed in this study is significantly high. Contamination rates of 1% and 50.55% were, respectively, reported in Ireland by Jordan et al. (2006) and in Vietnam by Van et al. (2007). The important variations in the prevalence could be due to differences in sample type, sampling procedures, and the detection methods employed (Uyttendaele et al., 1998; Molla and Mesfin, 2003; Goncagül et al., 2005; Stevens et al., 2006; Van et al., 2007). Thus, our results should be interpreted with caution, because of the small number of certain samples.

In the category of raw red meat and meat products, Salmonella was found in 23.61% of investigated samples. This result is higher than that obtained by Little et al. in 2008 (2.4%) and might be related to several risk factors.

No Salmonella was isolated from ovine meat samples, while bovine meat samples showed a contamination rate of 5.56%. Our results are in accordance with those of other studies carried out in Italy (Busani et al., 2005), Senegal (Stevens et al., 2006), Vietnam (Van et al., 2007), and Algeria, where Nouichi and Hamdi (2009) have reported a prevalence of 1.11% and 10% in ovine and bovine carcasses, respectively, using a wet-dry double swab sampling technique.

Salmonella prevalence in ground bovine meat that we recorded (4.17%) is lower than that reported by Gashe and Mpuchane in 2000 (20%), Molla et al. in 2003 (12.1%), and Ejeta et al. in 2004 (14.4%). This contamination likely occurs during meat processing at the retail level. Indeed, when meat is deboned, cut into pieces, and minced, more surfaces are exposed (Ejeta et al., 2004).

The highest rates of contamination recorded in merguez and merguez fillers (46.77% and 22.22%, respectively) can be explained either by contamination of raw material or by improper handling of guts and ground meat used for preparation. These raw meat products, which producers expect to be heated sufficiently before consumption, thus destroying the pathogen, are considered a risk to consumers because of the new undercooking trends now followed in Algeria.

Poultry meat is generally considered to be at a higher risk for Salmonella contamination than other meats (Jordan et al., 2006). In the category of raw poultry and meat products, we recorded a contamination rate of 17.97%. Various contamination levels were reported by numerous studies worldwide: 9.9% in Italy (Busani et al., 2005), 19.4–36.7% in Belgium (Uyttendaele et al., 1998), and 60% in Portugal (Antunes et al., 2002). This contamination originates from the poultry flock and increases throughout the poultry chain by cross-contamination during slaughtering (scalding, plucking, evisceration), cutting, and further processing (Uyttendaele et al., 1998; Molla and Mesfin, 2003; Bada-Alambedji et al., 2006). Salmonella often reach the carcasses from (i) the giblets, (ii) the intestinal tracts or fecal materials on feathers or feet, and (iii) the hands of slaughter workers or food handlers, working equipment, and utensils (Molla and Mesfin, 2003).

According to Uyttendaele et al. (1998), chicken parts are more often contaminated with Salmonella than are turkey parts; this probably relates to a higher contamination of the livestock of broiler chickens than turkey. Conversely, Jordan et al. (2006) reported that turkey was more contaminated with Salmonella than chicken. As displayed in Table 1, chicken meat samples showed comparable Salmonella contamination level (17.14%) to those of turkey meat samples (14.28% both for turkey cutlets and ground turkey meat), which may reflect the failure of measures for prevention of Salmonella contamination in the poultry holdings in Algeria.

Preparations for shawarma showed the highest contamination rate (33.33%). This could be due to poor hygiene practices in preparation at the retail level. The contamination observed in processed meat products that have undergone heat treatment can be related either to a contamination of ground meat used for their preparation or to a post–heat treatment cross-contamination at the retail level. These ready-to-eat products undergo subsequent handling and are often sold unpacked and sliced. According to Uyttendaele et al. (1998), most countries require that Salmonella be absent from ready-to-eat food products that require no additional cooking.

Distribution of Salmonella serovars

The serovars involved in salmonellosis vary geographically (Uyttendaele et al., 1998). The international trade of agricultural, aquacultural, and manufactured food products has greatly facilitated the introduction of new Salmonella serovars within the geographical boundaries of importing countries. While some serovars maintain their dominant role over many years, such as Typhimurium, others emerge and decrease over time (D'aoust, 1994; Uyttendaele et al., 1998; Molla et al., 2003).

The number of Salmonella serovars identified is high, with 64 isolates belonging to 21 different serovars. This would likely reflect cross-contamination from multiple sources and poor hygiene conditions at the retail level. Thus, meat processing must be better controlled.

Salmonella Anatum was the most prevalent serovar isolated (n=9) as observed in other studies carried out in North Africa: in Tunisia from foods (Ben Aissa et al., 2007) and in Algeria from slaughter ovine and bovine carcasses (Nouichi and Hamdi, 2009). In Europe and the United States, Salmonella Typhimurium was reported to be the most frequent isolate (Yan et al., 2003; Busani et al., 2005; Brisabois et al., 2006; Jordan et al., 2006; Little et al., 2008).

The distribution of Salmonella serovars identified in the present study was heterogeneous. However, Salmonella Anatum was solely associated with raw red meat. This exclusivity does not always appear to be checked. While some authors are in accordance with this observation (Nyeleti et al., 2000; Molla et al., 2003; Yan et al., 2003; Busani et al., 2005; Brisabois et al., 2006; Humphrey and Jørgensen, 2006; Ben Aissa et al., 2007), Angkititrakul et al. (2005) reported that Salmonella Anatum could be also associated with poultry (33.3%).

Salmonella Agona and Salmonella Newport were also associated with red meat category. According to Guellouz and Ben Aissa (1995), Salmonella Agona would be more frequent in bovine or equine meats, while Salmonella Newport would be closely associated with livestock (Brands et al., 2005) and the consumption of horsemeat (Egorova et al., 2008).

The distribution of serovars in the poultry meat category showed a predominance of Salmonella Enteritidis (n=5). This is supported by previous data from around the world (Uyttendaele et al., 1998; Dominguez et al., 2002; Goncagül et al., 2005; Oliveira et al., 2006). The presence of Salmonella Enteritidis in poultry meat is a significant contamination risk, as many authors report that this serovar represents the main source of foodborne diseases (Humphrey and Jørgensen, 2006; Oliveira et al., 2006). In Algeria, Salmonella Enteritidis was the most frequently isolated from various poultry farm samples (Aboun et al., 2003) and particularly from laying-hen samples (Bouzidi et al., 2012). In poultry feces and litter, only two serovars were identified: Salmonella Typhimurium and Salmonella Livingstone, with a detection rate of 12% and 1.6%, respectively, while no Salmonella was found in spleen or liver (Ammar et al., 2010).

In breeder farms and slaughterhouses, Salmonella Hadar was the most commonly identified (Elgroud et al., 2009). This serovar was also the most prevalent in poultry in Senegal (Cardinale et al., 2005) and the second most frequently reported serovar in Belgium (Uyttendaele et al., 1998) and in Spain (Dominguez et al., 2002).

Salmonella Heidelberg, another serovar common in poultry, was found to be predominant in retail chicken (Berrang et al., 2006; Zhao et al., 2008).

In the category of processed meat products, two serovars were identified: Salmonella Altona and Salmonella Indiana. These serovars were also associated in the current study with raw red meat and poultry meat categories. From this, contamination recorded in meat products is likely to originate from contaminated ground meat used for their preparation. Furthermore, the heat treatment that these products undergo seems insufficient to kill off Salmonella that contaminate the core of raw material.

Antimicrobial resistance

The increase and spread of antimicrobial-resistant Salmonella has been associated with extensive use of antimicrobial agents, not only in human and veterinary medicine, but also in livestock production for disease prevention or as growth promoters (Cruchaga et al., 2001; Antunes et al., 2003; Angkititrakul et al., 2005; Bada-Alambedji et al., 2006; Van et al., 2007; Little et al., 2008). This phenomenon can limit the therapeutic options for clinical cases that require antimicrobial treatment (Cruchaga et al., 2001).

In the current study, the number of isolates resistant to at least one antimicrobial is high (56/62) and could indicate that the use of antibiotics in animal husbandry is widespread. This is in accordance with previous results recorded in Algeria (80% [Elgroud et al., 2009]; 68.42% [Bouzidi et al., 2012]), in Senegal (60% [Stevens et al., 2006]), and in Vietnam (50.5% [Van et al., 2007]).

Resistance to sulphonamides was significant and could be the result of extensive use of these drugs in animal husbandry. Cotrimoxazole resistance was demonstrated in three isolates. In human medicine, this molecule (Bactrim^®) is often used to treat intestine infections; therefore, the existence of Salmonella resistant to this type of antibiotic has a potentially negative impact on human health. Ten and eight isolates were found to be resistant to streptomycin and tetracycline, respectively. Resistance to these antimicrobials is common in Salmonella isolates and has been observed previously in Algeria (Elgroud et al., 2009; Bouzidi et al., 2012) and Germany (Miko et al., 2005). In the present study, 10 isolates were resistant to nalidixic acid. Increasing resistance to this antimicrobial has been reported by several studies (Miko et al., 2005; Van et al., 2007; Elgroud et al., 2009; Bouzidi et al., 2012). The number of isolates resistant to furans is small (one isolate of Salmonella Anatum and one isolate of Salmonella Enteritidis) and could indicate that the use of these drugs remains moderate.

Resistance to pefloxacin was detected in one Salmonella Newport and two Salmonella Heidelberg isolates. According to AFSSA and AARN, this is a antimicrobial pattern that is troubling, as fluoroquinolones are essential in the treatment of invasive human salmonellosis (Antunes et al., 2003; Yan et al., 2003). Unfortunately, Salmonella isolates were found to be resistant to other fluoroquinolones in Algerian studies (ofloxacin and enrofloxacin [Elgroud et al., 2009] and ciprofloxacin [Bouzidi et al., 2012]). This may be related to uncontrolled use of these expensive molecules in our animal farms. Fortunately, no resistance to third generation cephalosporins has been reported.

Multidrug resistance was not solely associated with particular Salmonella serovars, as the 20 multidrug-resistant isolates belong to 11 different serotypes. Salmonella Anatum isolates, the predominant serovar in this current study, exhibited multidrug resistance, including resistance to streptomycin, sulphonamides, trimethoprim, and cotrimoxazole. By contrast, the isolates of Salmonella Enteritidis, the predominant serovar identified in poultry meat, were found to be resistant only to sulphonamides.

Three Salmonella Typhimurium isolates displayed “ACSSuT” pentaresistance pattern, which is another worrying antimicrobial pattern evidenced during this study. To our knowledge, this is the first report in Algeria of “ACSSuT”-resistant Salmonella Typhimurium isolates from raw meat. In Spain, resistance to “ACSSuT” was the most common multidrug-resistant pattern found among the multidrug-resistant Salmonella Typhimurium isolates from human and food sources (Cruchaga et al., 2001).

Conclusion

In the present study, the high rates of Salmonella contamination of a wide variety of raw meat and processed meat products and the detection of multiple serovars highlight a lack of hygiene at the retail level in Algiers (Algeria).

It is true that contamination of raw meat with Salmonella is not considered as a major risk to the consumer because the food is expected to be cooked thoroughly before consumption. The significant risk factor for human health is represented by new trends of cooking meat in Algeria and the presence of Salmonella in ready-to-eat processed meat products. Thus, to ensure the safety of meat and meat products for human consumption, surveillance of foodborne Salmonella through a continuous farm-to-fork system should be adopted.

Furthermore, our results indicate the widespread presence of resistant Salmonella strains with two worrying antimicrobial patterns: pefloxacin resistance and Salmonella Typhimurium “ACSSuT” resistance. It is essential that antimicrobials be appropriately used in food animals in order (i) to preserve the efficacy of existing drugs, (ii) to prevent the increase of resistance to recent molecules, and (iii) to limit the risk of transfer resistant pathogens to humans.

Detailed national epidemiological and microbiological studies must be undertaken to evaluate the prevalence of Salmonella spp. in each food of animal origin, and to determine the different serovars and the relationship between food production and outbreaks of human salmonellosis.

Footnotes

Acknowledgments

We gratefully thank the technical staff of the Hurbal Laboratory for assistance in isolation and biochemical identification of Salmonella. We also acknowledge the Enterobacteria Department, IPA, for serotyping and antimicrobial resistance testing the Salmonella isolates.

Disclosure Statement

No competing financial interests exist.

References

Aboun

, Benelmouffok

, Bougueddour

et al. Les salmonelloses aviaires diagnostiquées à l'institut Pasteur d'Algérie de 1988 à 2002: Sérotypes rencontrés, leurs antibiorésistances et les aspects réglementaires. Archives de l'institut Pasteur d'Algérie 2000/2003, Volume 64. ANDS (ed.) Alger: ANDS, 2003; 93–114.

Ammar

, Alloui

, Bennoune

, Kassah-Laouar

. Survey of Salmonella serovars in broilers and laying breeding reproducers in East of Algeria. J Infect Dev Ctries, 2010; 4:103–106.

Angkititrakul

, Chomvarin

, Chaita

, Kanistanon

, Waethewutajarn

. Epidemiology of antimicrobial resistance in Salmonella isolated from pork, chicken meat and humans in Thailand. Southeast Asian J Trop Med Public Health, 2005; 36:1510–1515.

Antunes

, Réu

, Sousa

, Peixe

, Pestana

. Incidence of Salmonella from poultry products and their susceptibility to antimicrobial agent. Int J Food Microbiol, 2003; 2:97–103.

Bada-Alambedji

, Fofana

, Seydi

, Akakpo

. Antimicrobial resistance of Salmonella isolated from poultry carcasses in Dakar (Senegal) Braz J Microbiol, 2006; 37:510–515.

Bell

, Kyriakides

. Salmonella: A Practical Approach to the Organism and Its Control in Foods. Wiley-Blackwell: Oxford, 2002.

Ben Aissa

, Al-Gallas

, Troudi

, Belhadj

. Trends in Salmonella enterica serotypes isolated from human, food, animal, and environment in Tunisia, 1994–2004. J Infect, 2007; 55:324–339.

Berrang

, Ladely

, Simmons

et al. Antimicrobial resistance patterns of Salmonella from retail chicken. Int J Poult Sci, 2006; 5:351–354.

Boudilmi

, Chalabi

. Les salmonelloses aviaries en Algérie: Incidence en santé publique. International Symposium on Salmonella and Salmonellosis (I3S) Proceedings, Ploufragan, France, 1997; 365–366.

10.

Bouzidi

, Aoun

, Zeghdoudi

, Bensouilah

, Elgroud

, Oucief

, Granier

, Brisabois

, Desquilbet

, Millemann

. Salmonella contamination of laying-hen flocks in two regions of Algeria. Food Res Int, 2012; 45:897–904.

11.

Brands

, Inman

, Gerba

, Maré

, Billington

, Saif

, Levine

, Joens

. Prevalence of Salmonella spp. in oysters in the United States. Appl Environ Microbiol, 2005; 71:893–897.

12.

Brisabois

, Danan

, Fremy

et al. Inventaire du Réseau Salmonella, Sérotypage et Sensibilité aux Antibiotiques de 2004. Maisons-Alfort, France: AFSSA, 2006.

13.

Busani

, Cigliano

, Taioli

, Caligiuri

, Chiavacci

, Di Bella

, Battisti

, Duranti

, Gianfranceschi

, Nardella

, Ricci

, Rolesu

, Tamba

, Marabelli

, Caprioli

. Italian Group of Veterinary Epidemiology. Prevalence of Salmonella enterica and Listeria monocytogenes contamination in foods of animal origin in Italy. J Food Prot, 2005; 68:1729–1733.

14.

Cardinale

, Perrier Gros-Claude

, Rivoal

, Rose

, Tall

, Mead

, Salvat

. Epidemiological analysis of Salmonella enterica subsp. enterica serovars Hadar, Brancaster and Enteritidis from humans and broiler chickens in Senegal using pulsed-field gel electrophoresis and antibiotic susceptibility. J Appl Microbiol, 2005; 99:968–977.

15.

Cruchaga

, Echeita

, Aladueña

, García-Peña

, Frias

, Usera

. Antimicrobial resistance in Salmonellae from humans, food and animals in Spain in 1998. J Antimicrob Chemother, 2001; 47:315–321.

16.

D'aoust

. Salmonella and the international trade. Int J Food Microbiol, 1994; 24:11–31.

17.

Domínguez

, Gómez

, Zumalacárregui

. Prevalence of Salmonella and Campylobacter in retail chicken meat in Spain. Int J Food Microbiol, 2002; 72:165–168.

18.

Egorova

, Timinouni

, Demartin

, Granier

, Whichard

, Sangal

, Fabre

, Delauné

, Pardos

, Millemann

, Espié

, Achtman

, Grimont

, Weill

. Ceftriaxone-resistant Salmonella enterica serotype Newport, France. Emerg Infect Dis, 2008; 14:954–957.

19.

Ejeta

, Molla

, Alemayehu

, Muckle

. Salmonella serotypes isolated from minced meat beef, mutton and pork in Addis Ababa, Ethiopia. Revue Med Vet, 2004; 155:547–551.

20.

Elgroud

, Zerdoumi

, Benazzouz

, Bouzitouna-Bentchouala

, Granier

, Frémy

, Brisabois

, Dufour

, Millemann

. Characteristics of Salmonella contamination of broilers and slaughterhouses in the region of Constantine (Algeria) Zoonoses Public Health J, 2009; 56:84–93.

21.

[EFSA] European Food Safety Authority. The community summary report on trends and sources of zoonoses, zoonotic agent and foodborne outbreaks in the European Union in 2006. EFSA J, 2007; 130:352.

22.

Gashe

, Mpuchane

. Prevalence of Salmonellae on beef products at butcheries and their antibiotic resistance profiles. J Food Sci, 2000; 65:880–883.

23.

Goncagül

, Günaydin

, Carli

. Prevalence of Salmonella serogroups in chicken meat. Turk J Vet Anim Sci, 2005; 29:103–106.

24.

Guellouz

, Ben Aissa

. Salmonelles isolées de denrées alimentaires d'origine animale entre 1989 et 1993 dans la ville de Tunis. Bull Soc Pathol Exot, 1995; 88:270–279(In French.)

25.

Humphrey

, Jørgensen

. Pathogens on meat and infection in animals—Establishing a relationship using Campylobacter and Salmonella as examples. Meat Sci, 2006; 74:89–97.

26.

Jordan

, Egan

, Dullea

, Ward

, McGillicuddy

, Murray

, Murphy

, Bradshaw

, Leonard

, Rafter

, McDowell

. Salmonella surveillance in raw and cooked meat and meat products in the republic of Ireland from 2002 to 2004. Int J Food Microbiol, 2006; 112:66–70.

27.

Little

, Richardson

, Owen

, de Pinna

, Threlfall

. Campylobacter and Salmonella in raw red meats in the United Kingdom: Prevalence, characterization and antimicrobial resistance pattern, 2003–2005. Food Microbiol, 2008; 25:538–543.

28.

Miko

, Pries

, Schroeter

, Helmuth

. Molecular mechanisms of resistance in multidrug-resistant serovars of Salmonella enterica isolated from foods in Germany. J Antimicrob Chemother, 2005; 56:1025–1033.

29.

Molla

, Mesfin

. A survey of Salmonella contamination in chicken carcass and giblets in central Ethiopia. Rev Med Vet, 2003; 154:267–270.

30.

Molla

, Alemayehu

, Salah

. Sources and distribution of Salmonella serotypes isolated from food animals, slaughterhouse personnel and retail meat products in Ethiopia: 1997–2002. Ethiop J Health Dev, 2003; 17:63–70.

31.

Mulvey

, Boyd

, Olson

, Doublet

, Cloeckaert

. The genetics of Salmonella genomic island 1. Microbes Infect, 2006; 8:1915–1922.

32.

Nouichi

, Hamdi

. Superficial bacterial contamination of ovine and bovine carcasses at El-Harrach slaughterhouse (Algeria) Eur J Sci Res, 2009; 38:474–485.

33.

Nyeleti

, Molla

, Hildebrandt

et al.

The prevalence and distribution of Salmonellae in slaughter cattle, slaughterhouse personnel and minced beef in Addis Ababa (Ethiopia)

Bull Anim Health Prod Afr, 2000; 48:19–24.

34.

Oliveira

, Cardoso

, Salles

RPR

, Romão

, Teixeira

RSC

, Câmara

, Siqueira

, Marques

LCL

. Initial identification and sensitivity to antimicrobial agents of Salmonella sp. isolated from poultry products in the state of Ceara, Brazil. Braz J Poult Sci, 2006; 8:193–199.

35.

Stevens

, Kaboré

, Perrier-Gros-Claude

, Millemann

, Brisabois

, Catteau

, Cavin

, Dufour

. Prevalence and antibiotic-resistance of Salmonella isolated from beef sampled from the slaughterhouse and from retailers in Dakar (Senegal) Int J Food Microbiol, 2006; 110:178–186.

36.

, Chiu

. Salmonella: Clinical importance and evolution of nomenclature. Med J, 2007; 30:210–219.

37.

Uyttendaele

, Debevere

, Lips

, Neyts

. Prevalence of Salmonella in poultry carcasses and their products in Belgium. Int J Food Microbiol, 1998; 40:1–8.

38.

Van

, Moutafis

, Istivan

, Tran

, Coloe

. Detection of Salmonella spp. in retail raw food samples from Vietnam and characterization of their antibiotic resistance. Appl Environ Microbiol, 2007; 73:6885–6890.

39.

Van Nierop

, Dusé

, Marais

, Aithma

, Thothobolo

, Kassel

, Stewart

, Potgieter

, Fernandes

, Galpin

, Bloomfield

. Bloomfield contamination of chicken carcasses in Gauteng, South Africa, by Salmonella, Listeria monocytogenes and Campylobacter. Int J Food Microbiol, 2005; 99:1–6.

40.

Yan

, Pendrak

, Abela-Rider

, Punderson

, Fedorko

, Foley

. An overview of Salmonella typing: Public health perspectives. Clin Appl Immunol Rev, 2003; 4:189–204.

41.

Zhao

, White

, Friedman

, Glenn

, Blickenstaff

, Ayers

, Abbott

, Hall-Robinson

, McDermott

. Antimicrobial resistance in Salmonella enterica serovar Heidelberg isolates from retail meats, including poultry, from 2002 to 2006. Clin Appl Immunol Rev, 2008; 74:6656–6662.