A comparison of the antimicrobial resistance patterns of gram-negative bacilli isolated from community-private and university-affiliated hospitals from Puerto Rico

Few studies have been performed in Puerto Rico concerning the antimicrobial resistance pattern of clinically significant Gram-negative bacilli. The antimicrobial resistance patterns of 5,590 Gram-negative bacteria obtained from three Community-Private Hospitals (CPH) and three University-Affiliated Hospitals (UAH) were evaluated utilizing the institutions' antimicrobial susceptibility reports for the year 2000. The objectives of this study were: to retrospectively evaluate the reported in vitro resistance of clinical isolates of E. coli, K. pneumoniae, E. cloacae, S. marcescens, P. aeruginosa and A. baumannii to selected standard antibiotics and to compare the antimicrobial resistance patterns between Community-Private (CPH) and University Affiliated hospitals (UAH). E. coli was the most common Gram-negative enteric bacilli in both CPH and UAH. In UAH, E. coli demonstrated a statistically significant higher resistance to the selected beta lactams and amikacin antibiotics but not to ciprofloxacin or gentamicin. For K. pneumoniae, the antimicrobial resistant pattern showed that UAH isolates were significantly more resistant to the tested antibiotics with the exception of ceftriaxone. In CPH, E. cloacae isolates were significantly more resistant to piperacillin-tazobactam, ciprofloxacin and gentamicin, while in UAH this organism was more resistant to amikacin. In UAH, S. marcescens isolates demonstrated a statistically significant higher resistance to all tested antibiotics with the exception of imipenem, which was similar in both hospitals group. Pseudomonas aeruginosa demonstrated a statistically significant higher resistance in UAH to all selected antibiotics with the exception of ciprofloxacin and gentamicin, which was similar in both hospitals group. Acinetobacter baumannii was the most resistant organisms in both hospitals group. UAH isolates were significantly more resistant than CPH isolates for all tested antibiotics. When compare with other large-scale antimicrobial resistance studies, the present study results suggest an apparent higher resistance in the Puerto Rican isolates. The high numbers of antimicrobial resistant Gram-negative bacilli in our study strongly suggest multiple mechanisms of antimicrobial resistance including the presence of extended spectrum and chromosomally derepressed beta-lactamases.