Epidemiology and etiology of nosocomial infections in a surgical intensive care unit

Objectives

To assess the epidemiology and etiology of nosocomial infections (NI) and to identify patterns of antibiotic resistance in a surgical ICU.

Setting

The ICU of 1st Clinic Hospital, Clinic of Surgery, Moscow.

Methods

From September 2002 to December 2004 we conducted a prospective study and detected the most frequent NI in patients admitted for more than 48 hours to the ICU. The diagnosis of NI was defined according to CDC criteria. We also evaluated antimicrobial resistance of isolated microorganisms. The identification and susceptibility to antibiotics has been performed in automated system MIC/ID panels as described by the NCCLS.

Results

During the study 2083 patients were admitted to the ICU, 1379 patients stayed more than 48 hours in the ICU. A total of 242 infection episodes were diagnosed in 149 patients with nosocomial infection (7.2%), 84 (56.4%) had a single infection, 48 (32.2%) had two infections, and 17 (11.4%) had three or more infections. Pneumonia were the most frequently reported type of infection (119 episodes, 49.1% of all cases of infection), followed by intra-abdominal infections (68 episodes, 28.1%), wound infections (28 episodes, 11.6%), laboratory confirmed bloodstream infections (14 episodes, 5.8%), urinary tract infections (eight episodes, 3%). About 43.0% infections were associated with sepsis, 43.8% with severe sepsis and 4.5% with septic shock, and 8.7% were not classified. The mortality rate for the ICU-acquired infections after 6 weeks of follow-up was 45.6%. Age ≥ 65 years (odds ratio [OR]: 4.08; 95% confidence interval [CI]: 2.05–8.11; P < 0.001), APACHE II score > 20 (OR: 10.70; 95% CI: 4.74–24.50; P < 0.001), SOFA > 5(OR: 15.6; 95% CI: 6.50–37.86; P < 0.001) were independently associated with mortality. The 246 isolated pathogens were represented by 92 Gram-positive cocci, 154 Gram-negative bacilli and 2% Candida species. Staphylococcus aureus (20.3%) was the most frequently isolated bacteria, followed by Acinetobacter spp. (18.3%), Pseudomonas aeruginosa (14.6%), Klebsiella spp. (13.4%), Enterococcus spp. (13.2%), Escherichia coli (8.1%). Resistance to oxacillin was observed for 94% of S. aureus isolates, all isolates were susceptible to vancomycin. The most active antimicrobial agents: against Acinetobacter spp. were imipenem (91.1%), ampicillin/sulbactam (64.4%); against P. aeruginosa were imipenem (88.9%), ceftazidime (69.4%), amikacin (58.3%); against Klebsiella spp. were imipenem (97%), amikacin (91%); against E. coli were imipenem (90%), amikacin (95%), ciprofloxacin (50%).

Conclusions

The NI rate during the period was 7.2%. The mortality of the patients with a NI is 45.6%. Pneumonia were the predominant type of infection. Staphylococci were the most frequently isolated pathogens, with very high levels of MR.