Prevalence of bacterial pathogens in infected wounds in a tertiary hospital, 1995-2001: any change in trend?

Wound care is a very important aspect of surgical care. Knowledge of the epidemiology of bacterial pathogens associated with infected wounds is critical in formulating policies on infection control.

To determine the prevalence of bacterial pathogens in wounds from various units of a Nigerian tertiary hospital orthopedics and traumatology department, as well as changes over time, if any, in the prevalence rates.

A retrospective study was conducted using laboratory records from 1995 to 2001.

670 bacterial isolates from 629 patients were studied. The most common isolates were Pseudomonas spp.-29.9%, and Staphylococcus aureus (S. aureus)--27.5%. Others were Klebsiella spp.-18.5%, Proteus spp.--15.1%, and Escherichia coli (E. coli)--7%. The least common were Streptococci--2%, and Enterococci--0.3%. Pseudomonas spp. accounted for 33% of isolates in the adult wards, while S. aureus was 21% and E. coli 8%. The pattem is similar in the pediatric ward (33.9%, 23.7%, and 8.5%, respectively) and Intensive Care Unit (ICU) (40%, 6.7%, and zero, respectively). S. aureus was the most common isolate from the orthopedic clinics (OPD) 40%, and the A&E (35%), followed by pseudomonas spp.-25.4% and 19%, respectively. The odds of a wound being infected with Gram-negative bacilli among inpatients compared with outpatients is 2.44 (95% CL = 1.72-3.47; P = 0.0000003) Between 1995 and 2001, the prevalence of Gram-positive bacteria decreased, while that of Gram-negative bacilli increased. The prevalence of Pseudomonas spp. and S. aureus also increased.

Wounds from patients in the orthopedics and trauma services are more frequently infected with Gram-negative bacilli than by Gram-positive bacteria. The prevalence of the former is higher in the ICU and least in the OPD. Pseudomonas spp. was the most common isolate. It was more common among inpatients, while S. aureus was more common among outpatients. The prevalence of Pseudomonas spp. in particular and Gram-negative bacilli in general is increasing.