Abstract
This study aimed to determine the prevalence and diversity of extended-spectrum β-lactamase (ESBL)-producing and multidrug-resistant (MDR) Escherichia coli and Klebsiella pneumoniae isolates from 136 broiler livers randomly purchased in 136 retail markets in Djelfa (Algeria). Isolation was performed on Hektoen agar and bacterial identification was carried out by API20E system and Maldi-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry). Antimicrobial susceptibility was tested by the disk diffusion and agar dilution methods. Detection of ESBLs and other resistance and integron genes, phylogenetic grouping, and molecular typing was performed by PCR and sequencing. Seventy-eight isolates (one per positive sample) were recovered: 73 E. coli and 5 K. pneumoniae. Among E. coli, 86.3% of isolates were MDR. ESBL activity was revealed in eight E. coli and five K. pneumoniae isolates (rates of 5.9% and 3.7% in analyzed samples, respectively). ESBL genes detected among E. coli were as follows (number of isolates): blaCTX-M-15 (3), blaCTX-M-1 (3), blaCTX-M-55 (1), and blaSHV-12 (1); all ESBL-producing K. pneumoniae isolates carried the blaCTX-M-15 gene. ESBL-producing E. coli isolates were assigned to lineages (phylogroup/sequence type and number of isolates in parenthesis): A/ST48 (1), B1/ST6448 (1), B1/ST5087 (3), B1/ST23 (1), and B2/ST131 (two blaCTX-M-15 E. coli isolates). K. pneumoniae isolates were ascribed to sequence types ST2010 and ST3483. Regarding the 65 non-ESBL E. coli isolates, the most observed resistance genes were as follows: tet(A) (75%), blaTEM (57.1%), and sul2 (43.5%). Class1 integrons were revealed in seven non-ESBL E. coli isolates (10.7%) and two gene-cassette arrays were identified: dfrA1 and aadA1+dfrA1. Our study provides evidence that broiler-derived food from Center of Algeria constitutes a source of ESBL and/or MDR-producing Enterobacteriaceae, with detection of relevant ESBL genes and epidemic clones.
Introduction
During the last decades, the emergence of antimicrobial-resistant bacteria has been enormously announced worldwide. In relation to an extensive use of β-lactam antibiotics in both clinical and nonclinical settings, a great diversity of β-lactamase types have disseminated. 1 In this context, extended-spectrum β-lactamase (ESBL)-producing bacteria constitute a mechanism of resistance of great clinical relevance that is spreading not only in humans but also among domestic animals. 2 ESBL-producing Enterobacteriaceae have been recognized as highly prevalent in food-producing animals and derived food, in the Mediterranean Basin countries.3–7 In the African continent, despite the different surveillances published, mainly in northern countries, regarding antimicrobial resistance among food-producing animals, information is still scarce. 2 In some previous studies, poultry and derivative products have been shown with the highest contamination level of ESBL-producing bacteria compared with other food sources.8,9
Regarding ESBL-encoding genes, the blaCTX-M is supposed to be the most often disseminated in poultry sector in North Africa.3,10 The blaSHV and the blaTEM ESBL-encoding genes have also been reported, with remarkable variation between countries.5,11,12 On the other hand, it has been mentioned that ESBL gene transmission is supported by epidemic plasmids (such as IncI1, IncK, and B/O plasmids, among others), some of which are similar in isolates from human and animal environments.6,13
Clinical multidrug-resistant (MDR) Escherichia coli isolates belonging to pathogenic clones have also been found to carry relevant ESBL genes. 1 Accordingly, not only antibiotic resistance genes encountered in clinical isolates are pertinent, but rather, all commensal strains from humans and animals, and their mobile genetic elements, constitute a probable reservoir from which, pathogenic bacteria can acquire resistance by horizontal gene transfer.14,15
To our knowledge, a very few number of studies have been performed in Algeria on the occurrence of ESBL-producing Enterobacteriaceae in food of animal origin commercialized in retails. In the Algerian society, broiler liver has become largely consumed by adult people and widely used in preparation of sandwiches in fast foods and restaurants. Once undercooked, this liver can be the origin of a risk of food poisoning. Therefore, this study was launched to investigate the prevalence of ESBL-producing Enterobacteriaceae (E. coli and Klebsiella pneumoniae) recovered from broiler liver in chicken markets of Djelfa area and analyze their phenotypic and genotypic characteristics.
Materials and Methods
Sampling and bacterial isolation
A total of 136 samples of broiler livers destined for human consumption, were randomly purchased during 2016–2018 from retail markets situated in six districts of Djelfa area, collecting one sample per market. The number of markets sampled from each district was as follows: 85 from Djelfa, 14 from Aïn Ouessara (100 km north of Djelfa), 12 from Hassi Bahbah (50 km north of Djelfa), 11 from Messaâd (75 km south of Djelfa), 8 from Znina (110 km southwest of Djelfa), and 6 from Aïn Maâbad (20 km north of Djelfa). Samples were accurately transported to the laboratory in sterile jars under cold storage and were processed for analysis on the same day.
At arrival, the surface of each liver sample was flamed using a Bunsen burner to eliminate any superficial contamination. Then, livers were cut aseptically into small pieces, and two to three of them were enriched on BHI broth (Pasteur Institute of Algeria), and incubated aerobically at 37°C for 24 h; after that, the enriched culture was inoculated on Hektoen agar plates (Pasteur Institute of Algeria) being incubated at 37°C for 24 h. Presumptive E. coli and K. pneumoniae colonies (lactose positive and H2S negative) were purified and identified, using Gram staining, oxidase test, TSI media (Pasteur Institute of Algeria), and API 20E system (BioMérieux, France). Furthermore, E. coli and K. pneumoniae identification was double checked by the Maldi-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) technique.
Antimicrobial susceptibility and ESBL phenotypic tests
Antimicrobial susceptibility was tested by disk-diffusion method on Mueller–Hinton medium (MH) (Pasteur Institute of Algeria) as previously recommended by CLSI (2018). 16 The antibiotics tested were as follows: β-lactams (ampicillin, amoxicillin/clavulanic acid, cefotaxime, ceftazidime, and imipenem), quinolones (nalidixic acid and enrofloxacin), aminoglycosides (neomycin and gentamicin), trimethoprim–sulfamethoxazole, chloramphenicol, and tetracycline. In parallel, synergy and complementary double-disk tests, using third-generation cephalosporins (cefotaxime and ceftazidime) and a β-lactamase inhibitor (amoxicillin–clavulanic acid), were applied for the detection of ESBL activity. E. coli ATCC 25922 and K. pneumoniae ATCC 700603 (ESBL-producing strain) were adopted as control strains. All the strains were conserved for subsequent genotypic characterization. The minimum inhibitory concentration (MIC) for colistin was tested in ESBL-positive isolates by the agar dilution method, and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used in this study. 17 Isolates that showed resistance to at least three families of antimicrobial agents were classified as MDR.
Characterization of β-lactamase genes
Bacterial DNA extraction was carried out by boiling three to five colonies in 1 mL of sterile Milli-Q water for 8 min. The isolates that have shown an ESBL-producing activity were analyzed by simplex PCR using universal (blaCTX−M, blaTEM, and blaSHV) and specific primers (blaCTX-M-1 and blaCTX-M-9 groups, and blaOXA-1). 18 Positive amplicons were sequenced to identify the corresponding subtypes of β-lactamases.
Characterization of other resistance encoding genes and integrons
Based on the obtained antimicrobial resistance phenotypes, isolates were checked for genes encoding resistance to tetracycline (tet(A) and tet(B)), sulfonamides (sul1, sul2, and sul3), chloramphenicol (cmlA and catA), colistin (mcr-1), or gentamicin (aac(3)-I and aac(3)-II). Ultimately, the presence of integrons was carried out by amplification of the class 1 integrase (intl1), and the amplified variable regions were characterized by sequencing. 19
Phylogenetic grouping and molecular typing
The phylogenetic group (A, B1, B2, or D) of ESBL-producing E. coli isolates was determined by a specific triplex PCR (chuA, yjaA, and TspE4.C2). Multilocus sequence typing (MLST) of seven housekeeping loci was performed for ESBL-producing E. coli isolates (adk, fumC, gyrB, icd, mdh, purA, and recA) and K. pneumoniae isolates (rpoB, gapA, mdh, pgi, phoE, infB, and tonB), to determine the sequence type (ST) and clonal complex (CC), as previously recommended.
Plasmid characterization and conjugal transfer
Transferability of the ESBL-encoding genes was checked through conjugation experiments. A plasmid-free, rifampicin-resistant, and lactose-negative E. coli CSH26 strain, showing sensitivity to all antimicrobial agents under study, was used as a recipient bacterium. MacConkey agar plates (Difco, Le Pont de Claix, France) supplemented with rifampicin (50 μg/mL) and cefotaxime (4 μg/mL) were used for transconjugant selection. Moreover, donors and transconjugants were subjected to PCR-based replicon-typing method to analyze the presence of IncI1, IncN, IncFIA, IncFIB, IncFIC, IncK, and IncL/M replicons. 21
Results
Antimicrobial resistance phenotype in E. coli/K. pneumoniae isolates
Among the 136 liver samples tested, 78 contained E. coli or K. pneumoniae (57.5%), and 73 E. coli and 5 K. pneumoniae isolates were recovered (1 isolate per positive sample).
High resistance rates were detected in E. coli isolates against tetracycline (98.6%), nalidixic acid (86.3%), trimethoprim/sulfamethoxazole (72.6%), ampicillin (71.2%), enrofloxacin (60.2%), and amoxicillin/clavulanic acid (57.5%). Resistance levels for other antimicrobial agents in E. coli isolates were as follows: cefotaxime (10.9%), ceftazidime (2.7%), imipenem (0%), neomycin (26%), gentamicin (6.8%), and chloramphenicol (16.4%). A multidrug resistance phenotype was detected in 86.3% of E. coli isolates and in all of the K. pneumoniae isolates (Table 1).
Antimicrobial Resistance Phenotype, Genetic Characteristics and Conjugal Transfer in Extended-Spectrum-β-Lactamase -Producing Escherichia coli and Klebsiella pneumoniae Isolates of Food Liver Samples
AMP, ampicillin; AMC, amoxicillin/clavulanic acid, CTX, cefotaxime; CAZ, ceftazidime; NAL, nalidixic acid; ENR, enrofloxacin; GEN, gentamicin; NEO, neomicin; SXT, trimethoprim/sulfamethoxazole; CHL, chloramphenicol; TET, tetracycline; MIC, minimum inhibitory concentration; ESBL, extended-spectrum β-lactamase.
+, ESBL transferred by conjugation; −, ESBL not transferred by conjugation; NP, not performed.
Prevalence and genetic characteristics of ESBL-producing E. coli and K. pneumoniae isolates
Eight E. coli and the five K. pneumoniae isolates were ESBL producers (rates of 5.9% and 3.7% in analyzed samples, respectively). All five ESBL-producing K. pneumoniae carried the blaCTX-M-15 gene. Genes-encoding ESBL detected in eight E. coli were as follows: blaCTX-M-1 (three isolates), blaCTX-M-15 (three isolates), blaCTX-M-55 (one isolate), and blaSHV-12 (one isolate). Other β-lactamase genes (blaSHV-1 and/or blaTEM-1) were present in six ESBL-positive isolates, in association either with the blaCTX-M-15 gene (one E. coli and four K. pneumoniae isolates) or the blaSHV-12 gene (one E. coli isolate) (Table 1).
ESBL-producing E. coli isolates were ascribed to the following lineages [phylogroup/sequence type/ESBL type (number of isolates)]: A/ST48/SHV-12 (1), B1/ST6448/CTX-M-55 (1), B1/ST5087/CTX-M-1 (3), B1/ST23/CTX-M-15 (1), and B2/ST131/CTX-M-15 (2). In addition, K. pneumoniae isolates were ascribed to sequence types ST2010 (three isolates) and ST3483 (two isolates) (Table 1).
Regarding other resistance genes, most of ESBL-producing isolates (seven E. coli and all five K. pneumoniae) harbored the tet(A) gene, and the remaining E. coli isolate contained the tet(B) gene. Resistance to sulfonamides was caused by the sul2 gene in K. pneumoniae isolates, whereas E. coli isolates carried the sul1, sul2, or sul3 genes. In one B1/ST5087 E. coli isolate, resistance to sulfonamides occurred by both sul1 and sul2 genes. All ESBL-producing isolates showed a colistin MIC of ≤2 μg/mL (in the susceptibility category) and were negative for mcr-1 gene (Table 1).
Moreover, 9 of the 13 ESBL-producing Enterobacteriaceae contained class 1 integrons, and the aadA1 gene cassette was found in the variable region of 3 E. coli isolates (Table 1).
The four ESBL variants were successfully transferred in seven of the nine ESBL producer strains tested by conjugation. Transconjugants carrying the blaCTX-M genes also acquired the IncK and IncI1 plasmids in three E. coli and one K. pneumoniae isolates, respectively. However, transfer of blaSHV-12 gene occurred in association with the acquisition of both IncFIB and IncI1 plasmids, and of tetracycline and sulfonamide resistance. In the remaining two transconjugants, all PCRs with tested replicons were negative (Table 1).
Genotype of antimicrobial resistance in non-ESBL-producing E. coli isolates
Focusing on the 65 non-ESBL-producing E. coli isolates from liver samples, a variety of resistance genes was detected (Table 2). The most frequent genes associated with tetracycline resistance were tet(A) (75%) and tet(B) (10.9%). Resistance to ampicillin was mainly mediated by the blaTEM gene (57.1%), whereas the blaSHV and blaOXA genes were absent. The sul2, sul1, and sul3 genes were detected in 43.5%, 21.7%, and 8.7% of sulfonamide-resistant isolates, respectively. The cmlA gene, which encodes a putative chloramphenicol efflux pump, was revealed in seven isolates, whereas the catA gene, which encodes a chloramphenicol acetyltransferase, was spotted in the remaining three chloramphenicol-resistant isolates. Interestingly, resistance to gentamicin was associated with the presence of the aac-(3)-II gene in all cases. Class 1 integrons were revealed in seven isolates (10.7%) and two gene cassettes were identified in the variable region of four of them: dfrA1 (three isolates) and dfrA1+aadA1 (one isolate).
Genetic Characteristics in the 65 Non-Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolates of Food Liver Samples
Discussion
More than half of liver samples destined for human consumption tested in this study were contaminated with E. coli or K. pneumoniae isolates and most of them showed a multidrug resistance phenotype. Moreover, ∼10% of the liver samples contained ESBL-producing E. coli or K. pneumoniae isolates, with diversity of bacterial genetic lineages and of ESBL genes. This situation is worrying, given that, these bacteria could be transmitted to humans through the food chain.
Enterobacteriaceae, notably E. coli strains, are known to be primary indicators of fecal contamination in food products. The heavy contamination recorded in this study could be mostly explained by the lack of hygiene that could occur during one of the stages of liver production: rearing, processing, transport, or distribution. Of all these stages, slaughter and evisceration remain the most critical points in contaminating livers. In our case, no information is available about the rearing system in the farms. Then, livers were either processed in the slaughterhouses of Djelfa region (sellers receive eviscerated carcasses) or in the markets (sellers receive partially eviscerated carcasses). Concerning distribution, we have noticed that the transport trucks were deprived of any refrigeration system in several cases (data not shown).
Moreover, there are several bacterial avian diseases (caused by Enterobacteriaceae) where the liver is affected, and so, the isolation of Enterobacteriaceae from the inside of liver samples might also be related to the occurrence of eventual bacterial diseases, mainly the avian colibacillosis caused by avian pathogenic E. coli strains. 4
The poultry farming system in Algeria ranges from small family farms to intensive industrial large-scale capacities. Small poultry units are made of plastic houses where the ambient conditions are difficult to manage (humidity, ventilation, and temperature), 22 which lead to the occurrence of diseases in livestock. Broilers are then distributed to either legal slaughterhouses where sanitary poultry inspection is carried out and distribution to butchers is performed in refrigerated trucks, or to clandestine slaughterhouses where chickens are slaughtered and sold illegally in bad hygienic conditions, and the risk of the nonseizure of carcasses affected could be high.
Among the 136 samples, 8 E. coli and 5 K. pneumoniae were carriers of ESBL-encoding genes (5.9% and 3.7%, respectively). The occurrence of ESBL-producing Enterobacteriaceae in animal and food settings vary within continents and countries, depending on many variables, including sampling conditions and isolation methods, which makes comparisons difficult to perform. Carriage rates of ESBL producers in food and healthy food-producing animals, ranged from 13% to 35% in Tunisia.6,10,18 In Algeria, frequencies of 1.6% and 26.2% of ESBL-producing E. coli recovered from broiler with colibacillosis and healthy broilers, respectively, were reported.5,23 Likewise, a rate of 12% was communicated from ready-to-eat sandwiches containing meat from different regions of Béjaia city, and 27.5% of ground beef samples were found to contain ESBL-producing E. coli in Algiers.13,24 Our study provides an additional evidence that broiler–derived food in Algeria continues to constitute a worrying source of ESBL and/or MDR-producing Gram-negative bacilli, with E. coli and K. pneumoniae being the most common hosts.
One of the major reasons for the appearance of ESBL strains in Algerian poultry production is the high rate of resistance levels recorded against the majority of authorized antibiotics, and therapeutic failures. Accordingly, many poultry farmers use third-generation cephalosporins (ceftiofur), which is indicated for cattle and is not allowed to be marketed in Algeria as an injectable agent, to compensate for the lack of effectiveness of the other failed antibiotics. In fact, the range of cephalosporins available for use in veterinary medicine is supposed to be limited compared with humans. Ceftiofur has been developed strictly for veterinary use, for the treatment of respiratory infections. 25 However, it has been demonstrated that third-generation cephalosporins, such as ceftiofur, in food animals is leading to resistance to other extended-spectrum cephalosporins, and could be hugely associated with the short-term increase of ESBL-producing E. coli in the gut of chicks. 26
As expected, the blaCTX-M variants were the most prevalent ESBL genes reported in this study. These results reinforce the previous background about the global expansion of the blaCTX-M in poultry and other food-producing animals worldwide.2,9,27–30 The blaCTX-M-15, which remains the most worldwide disseminated genotype, was detected in three E. coli and in all the K. pneumoniae isolates. This finding matches perfectly other studies showing that the contribution of this enzyme has awfully emerged in clinical and nonclinical settings, both in the developing and developed worlds. The horizontal transfer of blaCTX-M genes on conjugative plasmids and their location on mobile genetic elements are the major causes to their evolution and global spread.31,32 In Algeria, the first report of the blaCTX-M-15 goes back to 2006. 33 Furthermore, high frequencies were described from distinct environments: in hospitals,1,34 livestock animals,4,24 companion animals, 35 wild animals, 36 seawater, 37 and wild fish. 38 Recently, a 2019 study announced the occurrence of this genotype in K. pneumoniae isolates from Algerian fresh fruits and vegetables. 39 E. coli with blaCTX-M-1 and blaSHV-12 genes have been identified among our isolates with lower frequencies. On the other hand, the blaCTX-M-1 was known to be the most prevailing ESBL in livestock animals, mainly in Mediterranean countries.7,28 This verdict suggests the possibility of interspecies dissemination of ESBL genes, mainly the blaCTX-M-15. 40
In Algeria, the blaSHV-12 has been already reported from humans and animals.1,5,41 The low rate of blaSHV mentioned in this study joins other data, in which these genes have been described to not undergo the explosive spread that blaCTX-M variants have expressed.32,42 This result supports the hypothesis that blaSHV genes are particularly associated to health care infections. Moreover, our results indicate, interestingly, the isolation of a blaCTX-M-55-harboring E. coli isolate. Very recently, Hassen et al. (2019) 19 have communicated the first detection of blaCTX-M-55 from chicken feces and raw meat in Tunisia. To the best of our knowledge, this would be the first report of this genotype from Algeria. These two new reports, both from poultry, could be regarded as an alarming sign of the eventual dissemination of an unusual group 1 blaCTX-M variant in North Africa.
The detection of blaCTX-M-55 could be explained by the evolutionary potential of the CTX-M enzymes by a mutation in the blaCTX-M-15 gene by a single amino acid substitution (valine for alanine at position 80). 43 This mutation was first encountered in clinical E. coli and K. pneumoniae isolates from hospitalized patients in Thailand. 43 Thereafter, the large dissemination of this variant throughout Asian countries has been demonstrated.44–47
Phylogenetic grouping and MLST have shown a great genetic diversity among ESBL-producing E. coli isolates in this study (five different sequence types). Most of our ESBL-producing E. coli isolates belonged to phylogroups B1 and A (four and two isolates, respectively), which demonstrates the dominance of commensal strains among our isolates. 28 Among the phylogenetic group A, ST23 and ST48 were identified in two E. coli isolates, carrying, respectively, the blaCTX-M-15 and the blaSHV-12 genes. Previous reports have indicated the dissemination of these clones in chicken retail meat and poultry farms, but with different ESBL types.48,49 This concept suggests that horizontal gene transfer of various ESBL types can occur among the same lineage of E. coli isolates. Concerning those assigned to B1 phylogroup, ST5087 and ST6448 were detected in blaCTX-M-1 and blaCTX-M-55-containing strains, respectively. No data are currently available in the literature on the epidemiology of these two clonal lineages, which requires further complementary studies.
Worryingly, the presence of the epidemic B2/ST131 E. coli clone, which is classified as one of the most relevant extra-intestinal pathogenic lineages, 50 was also highlighted in our study among two ESBL-producing E. coli isolates. The fact that both ST131 strains were CTX-M-15 producers, demonstrates that pathogenic E. coli have developed resistance to extended-spectrum beta-lactams relevant to therapeutic in humans and animals. Indeed, many authors have clarified a lot about the epidemiology of this lineage and have hypothesized that ST131 may now be contributing importantly to antimicrobial-resistant E. coli infections worldwide.40,51 However, African investigations remain scarce. In Algeria, the blaCTX-M-15-harboring B2/ST131 clone was reported in uropathogenic E. coli from nonhospitalized patients, 52 and from wild fish in Mediterranean Sea. 38 This study could be the first report of blaCTX-M-15-containing clone B2/ST131 from food in Algeria.
In ESBL-producing K. pneumoniae isolates, the lineage ST2010 was identified in three isolates. This ST2010 clone seems to play an epidemiological role, given that it was revealed in a carbapenem-resistant K. pneumoniae isolate from children's hospital in China. 53 Furthermore, two CTX-M-15-producing K. pneumoniae isolates from two different zones were clustered into the same sequence type (ST3483).
Transferability of the blaCTX-M genes from our ESBL-producing isolates was associated with the acquisition of IncK and IncI1 plasmids, whereas the blaSHV-12 transconjugant acquired the IncFIB and the IncI1 replicon plasmids. These findings illustrate the diversity of plasmid incompatibility groups that potentially might harbor ESBL genes in Enterobacteriaceae from chicken in Algeria, and demonstrate the role of the foodborne pathway in ESBL-gene transmission by horizontal gene transfer, mediating the mobilization of genetic material from one bacterium to another. 54 Furthermore, in agreement with other studies on food and food-producing animals,13,28 class 1 integrons were present among ESBL and non-ESBL isolates, with the presence of streptomycin (aadA1) and trimethoprim (dfrA1) resistance genes inside their variable regions. These mobilizable genetic elements are known to be major contributors of the emergence, recombination, and expansion of multidrug resistance among bacteria. 55
Finally, our study reports an extremely high rate of MDR among E. coli/K. pneumoniae isolates from broiler liver commercialized in Djelfa area (86.3% in E. coli and all K. pneumoniae isolates). Similarly, in poultry, elevated phenotypic resistance levels were communicated in Eastern and Western Algeria.56,57 This is not surprising, given that, most of isolates exhibited a co-resistance to old drug agents used in poultry house, such as tetracycline, sulfonamides, and ampicillin, with tet(A), sul2, and blaTEM being the most common corresponding genotypes, respectively. In general, in Algerian poultry houses, we notice the high use of one or more antibiotics, sold at very affordable prices: fluoroquinolones (enrofloxacin), beta-lactam agents (ampicillin and amoxicillin), and tetracycline. This use is excessive because of the frequent presence, in the Algerian poultry farms, of many viral health problems that lead to inevitable bacterial secondary infections, mainly colibacillosis caused by E. coli. In addition, several authors have mentioned that antimicrobials are excessively administered by breeders from day 1 to slaughter, in Algerian chicken farms, for therapeutic purpose (e.g., β-lactams and fluoroquinolones for respiratory infections), preventive purpose (e.g., sulfonamides against salmonellosis and coccidiosis), or both, therapeutically and prophylactically.23,56 All these practices may lead to the emergence of resistance in commensal bacteria, which represents an impressive sign of selection pressure. 58 Co-selection could be another way of selection of MDR bacteria, including ESBL-producers.
Conclusion
Relevant ESBL genes (blaCTX-M-1, blaCTX-M-15, blaCTX-M-55, and blaSHV-12) in E. coli or K. pneumoniae, and blaCTX-M-15-containing clone B2/ST131 in E. coli isolates were detected in Algerian retail chicken liver. These findings reveal a serious public health concern, given that, such strains could be transmitted to human consumers through the food chain, generating an eventual public health risk. Complementary studies about the impact on human health should be further designed.
Footnotes
Acknowledgment
The authors thank students from Life and Natural Sciences Institute (University of Djelfa, Algeria) for their contribution in sampling and strains isolation.
Disclosure Statement
No competing financial interests exist.
Funding Information
N.S.C. was awarded a grant for the year 2018, from the Algerian Ministry of Higher Education and Scientific Research (The PNE Program), under the direction of Pr. Carmen Torres. Molecular characterization of the strains achieved in the University of La Rioja (Spain) was supported by project SAF2016-76571-R from the Agencia Estatal de Investigación (AEI) of Spain and the Fondo Europeo de Desarrollo Regional (FEDER) of EU. I.C. has financial support of “Fundação para a Ciência e Tecnologia” (FCT – Portugal), through the reference SFRH/BD/133266/2017 (Medicina Clínica e Ciências da Saúde). L.R.-R. has a predoctoral fellowship from the Universidad de La Rioja (Spain). O.M.M. has a predoctoral fellowship from Mujeres por Africa/Universidad de La Rioja (Spain).