Abstract
Surgical site infection (SSI) remains one of the most common complications of perforation peritonitis, contributing not only to morbidity but also mortality. We studied the culture and sensitivity of intra-peritoneal fluid and post-operative laparotomy wounds, and found consistency in pathogen and sensitivity between the intra and post-operative samples in 25 cases (80.6%). Therefore, routine culture and sensitivity of peritoneal fluid and subsequently switching the empirical anti-microbial therapy accordingly is justified.
Keywords
Introduction
Rupture of a hollow viscus causing peritonitis usually demands a subsequent exploratory laparotomy. Surgical site infection (SSI) is not unusual and broad spectrum antibiotics are recommended for prophylaxis on an empirical basis. SSI has an incidence of 15–25% varying with the degree of contamination, impacting all aspects of recovery.1–4
The spectrum of microbes causing secondary bacterial peritonitis following bowel perforation is well known, and so are the microbes causing surgical site infections following abdominal surgery.5–7 However, it is not known if any correlation exists between the two; our objective was to determine this.
Patients and methods
Our descriptive cross-sectional study was conducted in the department of Surgery and Microbiology, Maulana Azad Medical College, and associated Lok Nayak Hospital, New Delhi. We included 37 patients presenting with perforation peritonitis between January and December 2019 in one surgical unit. Patients undergoing elective surgery, those receiving antibiotics at the time of surgery, or those who died within 48 h of surgery were excluded. Ethical clearance was obtained from the institution's ethical review committee. A written, informed and voluntary consent was obtained from each patient.
At laparotomy, 10 mL of peritoneal fluid was initially collected in sterile culture bottles which yielded no growth for a number of cases, so subsequently we started sending the samples in blood culture bottles that were incubated at 37°C in BacT/ALERT 3D automated blood culture system, which increased the culture positivity rates. All patients were managed post-operatively by delayed primary closure of the skin 72 h after initial surgery. Two surgical site pus swabs were collected in each case from the surgical site at 48 h post-operatively and before closure of the wound at 72 h. Blood culture bottles were incubated at 37°C in an automated blood culture system (BacT/ALERT 3D, BioMιrieux, Durham, North Carolina, United States) for up to 5 days or till the time period growth was indicated, whichever was earlier. Positive culture bottle broths were further subcultured on Sheep Blood agar (enriched medium) and MacConkey agar (differential media). Collected pus swabs samples were also aerobically processed according to standard procedure. If growth was observed on plates, then further processing was performed. If growth was not observed after 24 h then plates were further re-incubated for an additional 24 h.
Cultured bacterial isolates were further identified by conventional microbiological methods and the VITEK-2 compact system (BioMιrieux, Durham, North Carolina, United States). Antimicrobial Susceptibility Testing (AST) of isolates was performed by the disc diffusion method following the CLSI (Clinical & Laboratory Standards Institute) guidelines and the automated VITEK-2 compact system by using AST N281 and AST P628 card according to the manufacturer's instructions. Coagulase-negative Staphylococcus (CoNS), Corynebacterium spp., Bacillus spp. (except anthracis), Micrococcus spp., Streptococcus viridans (α haemolytic streptococci), and Propionibacterium acnes were considered as skin contaminants.
Results
Out of all 37 patients, the commonest anatomical site of perforation was the small bowel (ileum and jejunum) (19, 51.3%), followed by duodenum (9, 24.3%) and caecum (4, 10.8%). [Table 1].
Anatomical site and site wise aerobic culture.
Staphylococcus aureus was the most common organism found in the intra-operative samples and post-operative swabs in cases of duodenal perforation. A majority of intra-operative samples and post-operative swabs obtained from patients with appendicular perforation were found to be culture negative. E. coli was the most common isolate from intra-operative samples and post-operative swabs in patients having small bowel, appendicular and rectal perforation.
Among culture positive cases, aerobic cultures were consistent with respect to the organism isolated and its antibiotic sensitivity between the intra-operative samples and the post-operative swabs in 3/5 patients with duodenal perforation peritonitis, 17/19 patients with small bowel perforation peritonitis, and a single patient with appendicular and rectal perforation peritonitis each, and 2/4 patients with caecal perforation peritonitis. One case of colon perforation did not show concordance.
The antibiotic sensitivity profile in our hospital for cases with perforation peritonitis showed highest sensitivity to meropenem for the common pathogen E. coli isolated in cases of small bowel perforation. [Table 2].
Antibiotic sensitivity profile.
Discussion
The mean age of patients in this study was 32.54 years, similar to other studies done in India.5–8 Here, perforation peritonitis mostly affects middle aged adults, probably owing to a higher incidence of enteric perforation and abdominal tuberculosis affecting the productive active age.9–11 Our study identified the most common site of perforation to be the small bowel, parallel to other studies from Northern India,6,8,12,13 whilst in Southern India, more gastroduodenal perforations seem to be found.14,15
Staphylococcus aureus was a surprise pathogen isolated and probably arises from normal skin flora. 17 Obviously, the upper gastro-intestinal tract has a lower bacterial load than the lower; E. coli appears to be common.6,16
Concordance between peritoneal fluid and wound culture appears to be frequent, as expected, the more so in small bowel perforation. Discordance was observed in a small minority of samples, and was possibly due to infection of the surgical site by exogenous bacteria from surgical instruments, caregiver contact, hospital environment or the air. Thus culture of the peritoneal fluid allows prior identification of likely surgical site infection after emergency laparotomy, and can guide antibiotic choice. Resistant organisms, particularly E. coli, the most common organism isolated, is worrying.
Initially, we observed that large proportion (10/12) of our peritoneal fluid samples were labelled culture negative when sent to the laboratory in sterile culture bottles. After, blood culture bottles that were incubated at 37°C in BacT/ALERT 3D in an automated blood culture system, the culture positivity rate increased from 16.7% to 86.3%, as found in other studies .18,19
We, therefore, suggest routine culture and sensitivity of peritoneal fluid collected during surgery and subsequently switching any empirical anti-microbial to specific organism-targeted therapy once results are obtained.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
