Bacterial isolates in community-acquired complicated intra-abdominal infections and their antimicrobial susceptibility patterns at Mulago Hospital

Abstract

Background: Intra-abdominal Infections (IAIs) are generally the result of invasion and multiplication of enteric bacteria in the wall of a hollow viscus or beyond. Complicated Intra-abdominal Infection (CIAI) refers to infection of an intra-abdominal hollow viscus with extension of the infectious process into the peritoneal cavity. CIAI consumes substantial hospital resources in terms of emergency services, imaging services, operating room time, laboratory services, antibiotic therapy and in-hospital care of variable intensity. The management of CIAI includes a surgical procedure for source control and antimicrobial therapy to eliminate the causative bacterial pathogens. The threat of antimicrobial resistance is one of the major challenges associated with antimicrobial management of CIAIs. If there is significant resistance (10 to 20% resistance) of a common community isolate to an antimicrobial agent in widespread local use, that agent should be avoided for initial empiric therapy. In most sub Saharan African settings, data on causative bacterial pathogens and their antimicrobial sensitivity pattern are scarce. This study isolated causative bacterial pathogens in CIAI patients at Mulago Hospital and tested for their antimicrobial sensitivity pattern.

Methods: Patients with acute abdomen admitted to the Emergency Surgical ward (3BES) were evaluated using the CIAI diagnostic criteria (Appendix 1). Those who satisfied the criteria and who were destined for emergency laparotomy received appropriate resuscitation and pre-operative work up and were followed up to the operating theatre. If intra-operative findings confirmed a CIAI, then 1 - 10 mLs of intra-peritoneal contaminant; pus, enteric spillage, peri-appendiceal collections etc. was collected in an aseptic manner using a syringe and transferred into a sterile sample container. This was sent to the laboratory where it was centrifuged and the sediment was inoculated onto Blood Agar, Chocolate Agar and MacConkey Agar, incubated at 35-37° C and under 5% carbondioxide and monitored for growth. Isolated bacteria was identified and then inoculated onto the Muller-Hinton Agar for drug susceptibility testing using the disc diffusion method and following the CLSI guidelines. Only aerobic culture was performed. Fungal growth if present was detected on Chocolate Agar.

Results: Perforated PUD and appendicular pathology were the commonest sources of intra-abdominal infection, each comprising 32.1%. E. coli was the predominant bacterial isolate, comprising 51.2% of all isolates, followed by Klebsiella pneumonia (17.1%). E. coli isolates were up to 50% resistant to Ceftriaxone and up to 62% resistant to Levofloxacin, but they were 70% sensitive to Chloramphenicol and 80% sensitive to Gentamycin. All bacterial isolates were 100% sensitive to Imipenem.