Bacterial causes and antibiotic susceptibility patterns of aerobic isolates from burn wound infections in Dar es salaam, Tanzania

Abstract

Background: Burn wound is one of the most common, devastating and painful trauma. Infection remains the most common cause of morbidity and mortality in burn patients. Information on local pathogens and sensitivity to antimicrobial agents is crucial for successful treatment of these infections. Aim: To determine bacterial causes of BWI and antibiotic susceptibility patterns of aerobic isolates from burn patients at tertiary and regional hospitals in Dar es Salaam, Tanzania. Methods: This was a cross-sectional study that was conducted between May and July 2017. Burn wound swabs were collected from patients with signs of wound infection. Swabs were cultured on blood agar and MacConkey agar and incubated aerobically at 37°C for 18–24 hours. In addition, a blood sample was collected from patients with a history of fever and/or temperature of ≥ 38º C. Bacterial identification was done using conventional method and API20E. Antimicrobial susceptibility was determined by Kirby-Bauer disk diffusion method. Results: A total of the 70 patients with clinically diagnosed burn wound infections had their wound cultured. Sixty six (94%) had positive bacterial growth after overnight incubation. A total of 131 pathogenic bacteria were isolated, with gram negative organisms 91(69.5%) being more prevalent. The most frequently isolated bacteria were Pseudomonas aeruginosa (26%), followed by Acinetobacter spp (22%) and Coagulase negative staphylococci (CoNS) (18%), Klebsiella spp (11%) and Staphylococcus aureus (9.9%). CoNS were most common in BSI. Proportion of BSI among patients with BWI was 37.5%. Chloramphenicol was found to be most effective drugs towards gram positive bacteria and Klebsiella, while imipenem was effective against Acinetobacter spp. Up to 73% Enterobacteriaceae were extended spectrum beta-lactamase producers, while 61% of Staphylococci spp were resistant to methicillin. Proportion of MDR among all isolates was 73.5%. Two (2/70, 2.9%) paediatric patients died during the period of the study. Conclusions and recommendations: P. aeruginosa was the most common isolate in BWI while CoNS were common in BSI. Most of the organisms isolated were resistant to commonly prescribed antibiotics. High proportion of infections were due to ESBL producers and methicillin resistance staphylococci spp. Routine culture and antimicrobial susceptibility testing should be performed before the start of therapy; including MRSA and ESBL screening