Evolution of antimicrobial resistance among Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumonide in Brooklyn, NY

Objectives: To document resistance patterns of three important nosocomial pathogens, Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae, present in hospitals in Brooklyn, NY. Methods: Susceptibility profiles of pathogens gathered during a surveillance study in 2006 were analysed and compared with similar surveys performed in 1999 and 2001. MICs were determined according to CLSI standards, and selected isolates were screened by PCR for the presence of VIM, IMP and KPC P-lactamases. Results: For A aeruginosa, susceptibility to most antimicrobials fell in 2001 and then reached a plateau. However, there was a progressive decrease in the number of patients with A. aeruginosa during the three surveys. While the total number of isolates of A. baumannii remained steady, there was a progressive decrease in susceptibility to most classes of antimicrobial agents, and approximately one-third had combined resistance to carbapenems, fluoroquinolones and aminoglycosides. There was a noticeable rise in the number of isolates of K. pneumoniae over the surveillance periods, suggesting that this has become the predominant pathogen in many medical centres. Over one-third of K. pneurnoniae collected in 2006 carried the carbapenemase KPC, and 22% were resistant to all three classes of antimicrobial agents. Conclusions: Hospitals in our region have been beset with antimicrobial-resistant Gram-negative bacteria. K. pneumoniae has rapidly emerged as the most common multidrug-resistant pathogen. Improved therapeutic agents and methods of detection are needed to reduce transmission of these bacteria.