Prevalence of wound-associated biofilm-forming bacteria and antibiotic resistance in patients admitted at Muhimbili National Hospital, Tanzania

Abstract

Antibiotics are used to treat infectious diseases, particularly those caused by pathogenic bacteria. However, sometimes these antibiotics  fail to completely eradicate the pathogenic bacteria. Wounds are prone to bacterial infections as a result of breached protective barriers,  allowing easy access into the human body. Such disruption of the normal anatomical tissues due to accidents or medical procedures may  lead to infections. The presence of bacteria on infected wounds may cause the formation of biofilm, which is usually more difficult to treat  with conventional antibiotics. The aim of this study was to determine the prevalence of antibiotic resistance in wound-associated  pathogenic bacteria and their biofilm-forming capacity after isolation from wounds in patients admitted at Muhimbili National Hospital (MNH), Tanzania. It was a cross-sectional laboratory-based study, conducted between January 2022 and August 2022, involving the  collection of wound swabs from 65 patients. Each swab was cleaned off using sterile normal saline and plated onto both selective and  non-selective agar plates. Congo red agar (CRA) biofilm detection method was employed for identification of biofilm forming capacity of  each resultant colony. Antibiotic sensitivity testing (AST) was performed on both the biofilm-forming and non-biofilm forming bacteria  against widely used antibiotics. The multiple antibiotic resistance index (MARI) was calculated. A total of 71 isolates belonging to eleven  different species of pathogenic bacteria were discovered. Ninety percent (n = 64) of the wounds had bacterial infections. The predominantly isolated bacteria were Pseudomonas aeruginosa and Escherichia coli. The majority (69%) of the isolates were biofilm  formers, while over 59% of the isolated pathogens were resistant to tested antibiotics. Over 70% of the bacterial isolates exhibited MARI  greater than 0.2, an indication of multiple antibiotic resistance (MAR). Conclusively, the prevalence of wound infections was high. Biofilm  formers were predominantly isolated and were more resistant to the tested antibiotics. The majority of the isolated bacteria had MARI  greater than 0.3, suggestive of MAR.