Microbiological surveillance and parenteral antibiotic use in a critical care unit

To evaluate parenteral antibiotic utilization and bacterial resistance patterns in a critical care unit (CrCU).

Descriptive, prospective audit of infection site, culture and antimicrobial susceptibility test results, parenteral antibiotic usage and duration, total antibiotic acquisition costs, and length of stay.

A 17-bed medical-surgical CrCU in a tertiary care teaching hospital in Metropolitan Toronto.

Two hundred and fifty-eight patients admitted to the CrCU between May 1995 and April 1996 who received antimicrobial therapy.

The most frequently prescribed antibiotics were cefazolin (47%, 1098 g), gentamicin (33%,141 g) and ceftriaxone (20%, 255 g). The most common indications for antimicrobial therapy included surgical prophylaxis (34%) and pneumonia (35%). The following organisms were isolated from patients treated with antibiotics: Staphylococcus aureus (26%), Pseudomonas aeruginosa (13%), enterococci (12%), Haemophilus influenzae (11%), Escherichia coli (11%), Enterobacter cloacae (8%) and other Gram-negative bacilli (19%). Only 9% of Gram-negative bacilli were resistant to aminoglycosides, 3% were resistant to ciprofloxacin and no extended-spectrum beta-lactamases or imipenem-resistance were detected. No vancomycin-resistant enterococci and only two methicillin-resistant Staphylococcus aureus isolates were identified.

Antibiotic use during the audit appeared appropriate for the specific clinical indications. Low levels of bacterial resistance were detected during the audit.