Antimicrobial Susceptibility Survey: MATERIALS AND METHODS
Background and Collection of Isolates
From January 1, 2001 to December 31, 2002, R aeruginosa isolates were recovered from patients seen at various centers in Trinidad. Isolates were collected from community sources, (privately operated microbiology laboratories, general practitioners offices, outpatients clinics) and hospitals (specimens from the ICUs, surgical services, nursery, adult and pediatric medical wards, and the obstetric and gynecology wards) [See Acknowledgements], and then submitted to the Eric Williams Medical Sciences Complex Microbiology Laboratory (EWMSC). All isolates from community sources and other hospitals were received on Mueller-Hinton agar plates. Data obtained for each isolate were the patient’s age, sex, the source of the isolate, whether the patient was nonhospitalized or hospitalized in an ICU, surgical ward, or on a neonatal unit. Specimens with incomplete data were few and therefore were excluded from the study. The EWMSC is a fee-for-service, 560-bed tertiary hospital complex located in the northwestern part of Trinidad. Trinidad is about 4,828 km2 in area and is the larger of the twin-island republic, Trinidad and Tobago, located about 11 km off the northern coast of Venezuela in South America. The population of the republic is about 1.25 million people.
Bacteriologic Methods
R aeruginosa were identified by colonial morphology, a positive oxidase reaction, pyocyanin production on Mueller-Hinton agar (BBL Microbiology Systems, Cockeysville, MD), motility, growth at 42°C on cetrimide agar and biochemical tests. О serotyping was not done. Antimicrobial susceptibility testing was done on Mueller-Hinton agar following recommendations of the National Committee for Clinical Laboratory Standards, using: drug ciprofloxacin 5 mg, amikacin 30 ng, ceftazidime 30 ng (Oxoid, UK), imipenem 10 mg, generic gentamicin 10 mg, tobramycin 10 ng, aztreonam 30 mg, generic piperacillin 100 mg, and cefepime 30 mg (Becton Dickinson, USA. Mueller-Hinton broth was used as the growth medium. The final bacterial inoculum concentration was approximately 1.5 x 108 colony-forming units (CFU)/ml. Before the antibiotic discs were placed, the Mueller-Hinton plates were inoculated with swabs that were submerged in the final inoculum concentration and streaked over the entire surface of the plates. Plates were incubated aerobically at 35-37°C for 18-24 hours.
The control organism was R aeruginosa ATCC strain 27853, obtained from the Caribbean Epidemiology Center, a local branch of the Pan American Health Organization/World Health Organization. Information on the amount and cost of antimicrobials consumed by each service in the hospital was obtained from the pharmacy department and the Ministry of Health.
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