Prevalence of Extended Spectrum Beta-Lactamase Producing Bacteria in Patients with Wound Infections Attending Tertiary Hospitals in Enugu, Nigeria

Abstract

Background: The problem of antibiotics usage against bacterial infection is the modifications of such antibiotics by the bacteria thereby rendering them ineffective. Extended spectrum β-lactamase (ESBL) producing bacteria invading wound infections may lead to long term hospitalization, financial burden and limited antibiotics for therapy. The goals of this study were to determine the prevalence of ESBL-producing bacteria colonization of wound infections among individuals with non-healing wounds and the antibiotic susceptibility pattern of the ESBL isolates. Methodology: The study adopted a cross-sectional research design.  A total of 266 samples were collected from different wound infections which included diabetic foot ulcers, burn wounds, post-surgical wounds, non-diabetic foot ulcers, pressure ulcers, accident and open cancer wounds that met the inclusion criteria. The patients were consecutively selected. That is, any individual that has a wound and was willing to participate was selected. A structured questionnaire was administered to the patients to obtain information on demographic characteristics, antibiotic usage, and duration of infection, herbal medication, type and site of wound. Identification of bacterial isolates was done using colony/ microscopic morphology, gram stain reaction and standard biochemical tests. Antibiotic susceptibility testing was done using modified Kirby - Bauer disc diffusion method. ESBL detection was done following the recommendations by the Clinical and Laboratory Standard Institute (CLSI) which involves a 2-step approach of initially screening for ESBL producers and phenotypic confirmatory test using a combination disc test method. Molecular screening of the genes encoding for ESBLs was done at the Central Science Laboratory, University of Nigeria, Nsukka. Results: A total of 196 isolates were recovered from the wound swabs.  Pseudomonas aeruginosa 56 (28.6%) was the leading organism causing wound infection followed by Staphylococcus aureus 24 (12.2%). The bacteria isolates showed that 157 (80.1%) were gram negatives as against 39 (19.9%) that were gram positive bacteria. Among the gram-negative bacteria isolates, 21.7% (34/157) were confirmed as ESBL producers. The ESBL- producers were Pseudomonas aeruginosa, Esherichia coli, Proteus vulgaris, Proteus mirabilis, Klebsiella oxytoca, Klebsiella pneumonia and Klebsiella granulomatis at frequencies of 41.2%, 20.6%,14.7%,11.8%,5.9%,2.9% and 2.9% respectively. This showed that these isolates have the ability to resist penicillins and cephalosporins of the first, second and third generations. The ESBL-producing bacteria isolated exhibited high degree of multidrug resistance especially to tetracyclines, cefuroxime, ceftriaxone, cefotaxime and ceftazidime. The antibiotics amikacin was sensitive to most of the ESBL-producing bacteria isolated. The assessment of the risk factors showed that none of the variables was statistically significant, though those risk factors were still important in evaluating wound infections.  Both hospital and community acquired infections showed no statistical significance (P= 0.072) which means that both had the same degree of pathogenicity. Among the 10 samples screened for ESBLs genes namely bla SHV, bla TEM, bla CTX-M, bla GES, and bla OXA-50, only bla OXA- 50 was detected in 8 out of the ten samples. Thus, the persistent gene circulating in this region is bla OXA-50, which confers high rate of infection and persistence. Conclusion: The presence of ESBL-producing bacteria in wounds remains a challenging issue, as the majority of the patients may suffer from long term infected wounds due to treatment failure.