Analysis of 5 years of bacteraemias: importance of stratification of microbial susceptibilities by source of patients.

Many factors need to be considered when selecting empiric antimicrobial treatment for infections; foremost are the principal pathogens causing the diagnosed infection and their antimicrobial susceptibility patterns. These susceptibilities are location specific. This study analyses blood cultures of a 5-year period (1990-94) at a 550 bed community hospital and stratifies antimicrobial susceptibilities by source of patients. Data included: date of culture, patient location, number of positive bottles with the same organism over a period of 2 weeks and results of susceptibility testing. Positive cultures from patients in the Emergency Department were deemed to reflect community-acquired strains: positive cultures from patients in the Intensive Care Unit were considered nosocomial organisms. During the study period 52055 blood cultures were drawn; 5652 (11%) from 2742 patients grew at least one organism, excluding skin contaminants. Organisms cultured most frequently were: Enterobacteriaceae: 1162 patients (42%); Staphylococcus aureus: 442 (16%); Enterococcus; 429 (16%); and Pseudomonas: 196 (7%). Antimicrobial susceptibility percentages of Enterobacteriaceae from Emergency Room patients (n = 370) were significantly greater to all tested antimicrobials than from ICC patients (n = 161) (P < 0.001). Overall, 143 isolates of S. aureus from 442 patients (32%) were methicillin resistant (MR); stratification by department revealed a range of 20/142 (14%) MR in community acquired strains to 49/67 (73%) from ICU patients (P < 0.001). Detailed tables with antimicrobial susceptibilities according to strains, and stratified by source of patients are presented. When selecting empiric antimicrobial therapy for patients with bacterial infections, it is crucially important to physicians to have access to antimicrobial susceptibility percentages, stratified by source of patients.