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.

A comparison of the antimicrobial resistance patterns of gram-positive cocci isolated from community-private and university-affiliated hospitals from Puerto Rico.

The antimicrobial resistance patterns of 2,462 selected Gram-positive cocci 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: 1) to evaluate the in vitro resistance to selected standard antibiotics of Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae clinical isolates, and 2) to compare the antimicrobial resistance patterns between community-private (CPH) and university-affiliated hospitals (UAH). Staphylococcus aureus was the most common Gram-positive isolated organism in CPH (63.3%) followed by E. faecalis (31.0%). In UAH, the most prevalent cocci were E. faecalis (51.7%) followed by S. aureus (43.9%). Enterococcus faecium represented 2.3% and 4.4% of CPH and UAH isolates, respectively. Streptococcus pneumoniae represented 3.4% of the total Gram-positive isolates from CPH, no S. pneumoniae was reported in UAH. The antimicrobial susceptibility results showed that for Staphylococcus aureus there was a statistically significant higher resistance to methicillin and thrimethoprim sulfamethoxazole in UAH, while resistance to erythromycin was significantly higher in CPH. There was no difference in the resistance of S. aureus to other antimicrobial agents between hospitals groups. A statistically significant resistant to vancomycin was found between enterococcal isolates from UAH (43%) and CPH (12.7%). High-level aminoglycoside resistance (HLAR) was observed among UAH enterococcal isolates with E. faecium showing a higher resistance than E. faecalis, no data for HLAR in CPH could be obtained. For pneumococci 46% of CPH isolates were resistant to penicillin. In summary, there are important differences in the prevalence and antimicrobial resistance between the Gram-positive bacteria isolated from community and teaching hospitals.

Prospective study using standardized methodology for antimicrobial susceptibility of gram-positive cocci isolated from the Puerto Rico Medical Center.

The Gram-positive cocci (GPC), Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis and Enterococcus faecium, have become important causes of community and nosocomial-acquired infections. The prevalence of multiple resistant isolates to standard antimicrobial drugs has significantly increased over the past decades. Few prospective studies have been performed in Puerto Rico (PR) concerning the GPC antimicrobial susceptibilities pattern. The purpose of this study was to evaluate the in vitro susceptibility of GPC clinical isolates from PR to selected standard antibiotics and to the new antimicrobial agents, linezolid (LZ), quinupristin/dalfopristin (Q/D) and gemifloxacin (GM). The in vitro susceptibility utilizing disk diffusion and Etest methods to selected antibiotics was determined for a total of 429 isolates obtained during a period of 5 months from the Puerto Rico Medical Center Bacteriology Laboratory. The distribution of GPC collected was as follows: 213 S. aureus isolates, 162 E. faecalis, 16 E. faecium and 38 S. pneumoniae. The results of the susceptibility test demonstrated: 1) that in S. aureus, 100% of the isolates were susceptible to vancomycin (VAN), LZ and Q/D; 93% to GM; and 61% to methicillin/oxacillin; 2) in S. pneumoniae, 100% were susceptible to LN and GM; 87% to Q/D; and 53% to penicillin; 3) in E. faecalis, 99% were susceptible to ampicillin; 93% to LZ; 79% to GM; 78.6% to VAN; and 0% to Q/D. Sixty eight and 66% of the E. faecalis isolates were susceptible to gentamicin and streptomycin respectively; and 4) in E. faecium, 100% were susceptible to LZ; 94% to Q/D; 69% to GM; 37.5% to VAN and 20% to ampicillin. In E. faecium isolates, 50% and 31% were susceptible to gentamicin and streptomycin, respectively. Of the vancomycin resistant enterococci, 88.9% and 21% of E. faecium and faecalis showed VanA phenotypic resistance, respectively. These results show that there is a significant degree of antimicrobial resistance in GPC, including 38% methicillin resistance in S. aureus, a near 50% penicillin resistant S. pneumoniae, and a significant resistance of enterococcal species to VAN. The new agents, LZ, Q/D and GM, proved to be effective against both, S. aureus and S. pneumoniae. For E. faecium, both, LZ and Q/D were active, while for E. faecalis, only LZ showed consistent activity.