Antimicrobial Susceptibility Survey
INTRODUCTION
Pseudomonas aeruginosa is a ubiquitous organism frequently isolated from clinical specimens. Because these organisms are usually inherently resistant to many antimicrobial agents, treatment of pseudomonal infections is usually difficult, and mortality is usually high. This intrinsic resistance is mainly a result of the diffusion barrier of the bacterial outer membrane; amino-acid substitution in the target molecules, such as Gyr A and/or Par C, via point mutation in each genetic determinant; and antimicrobial inactivating enzymes. In most hospital environments, this inherent resistance is further complicated by mutations mediated via chromosomes and the acquisition of resistant genes from plasmids and transposons. One type of mutation simultaneously comprises, and enhances resistance to chloramphenicol and tetracyclines by accelerating multidrug efflux. Other mutations involve loss of the D2 porins that mediate carbapenem resistance, reduce uptake of aminoglycosides across the outer or cytoplasmic membrane, and inactivation by aminoglyco-sides-modifying enzymes. Recently, strains of P aeruginosa resistant to all antimicrobials except polymyxin В were reported. Genetic analyses of these strains identified two unique extended-spectrum beta-lactamase genes. One—bla (VIM-7)— encoded a metallo-beta-lactamase, and the other— bla (OXA-45)—encoded a class-D extended-spectrum beta-lactamase.
P aeruginosa resistance is not restricted to the hospital environment but has also been seen in community-acquired infections, such as otitis externa, folliculitis, osteomyelitis, outpatients with chronic indwelling urethral catheters, and endocarditis in intravenous drug users. The prevalence of resistance among P aeruginosa strains has been extensively reported, especially with the expansion in the number of (3-lactam agents with improved antipseudomonal activity. Resistance may not be as widespread as reported, and there may be considerable geographic variation. Recently, several deaths due to septicemia with multiresistant R aeruginosa were reported at a neonatal intensive-care unit (ICU) in a southern hospital in Trinidad. No data on the susceptibility patterns among R aeruginosa strains have been documented in Trinidad.
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The purpose of this study, therefore, was to evaluate the current level of resistance among R aeruginosa isolates from various centers throughout Trinidad to the currently available antipseudomonal antimicrobial agents.
Category: Main
Tags: antimicrobial resistance, antipseudomonal drugs, community-acquired infections, nosocomial infections, Pseudomonas aeruginosa