Bacterial Pathogens Isolated from Patients with Bloodstream Infections in Latin America, 1997: Frequency of Occurrence and Antimicrobial Susceptibility Patterns from the SENTRY Antimicrobial Surveillance Program.

We report the antimicrobial susceptibility of 736 organisms isolated from bloodstream infections in 10 Latin American medical centers during the first six months of 1997. The data presented here is from the SENTRY Antimicrobial Surveillance Program, a comprehensive surveillance study involving 72 medical centers worldwide. The isolates ivere tested for in in vitro susceptibility to 35 antimicrobial agents by the broth microdilution method. The five most frequently isolated species were (n/%): Staphylococcus aureus (1 65/22.4%), Escherichia coli(118/16.0%), coagulase-negative staphylococci (CoNS - 115/15.6%), Pseudomonas aeruginosa (51/6.9%), Klebsiella spp. (46/ 6.3%). Susceptibility to oxacillin was 70.9% for S. aureus and only 33.9% for CoNS. Vancomycin was active against all of staphylococci, while teicoplanin was active against 99.4% of S. aureus and only 90.4% of CoNS. The new fluoroquinolones sparfloxacin, gatifloxacin, and trovafloxacin, and the streptogramin, quinupristin/dalfopristin, were very active against these species. Only one vancomycin-resistant enterococcus was detected; however, high-level aminoglycoside resistance rates were common (66.7%). E. coli and Klebsiella spp. showed low susceptibilities for cefotaxime (90.7% and 41.3%) and for cefoxitin (85.6% and 78.3% respectively), indicating a high frequency of isolates that produce ESBL and/or stably derepressed ampC enzymes. These strains, phenotypically consistent with extended-spectrum beta-lactamase (ESBL) production, were typed using ribotyping and pulsed-field gel electrophoresis. The most active compounds (M IC90 in µg/mL /% susceptibility) against P. aeruginosa were meropenem (2 /94.1%), followed by amikacin (>32 / 86.3%), and piperacillin alone or with tazobactam (128/84.3%). Ceftazidime and cefepime showed similar activity (70.6% susceptibility) and levofloxacin was the most active fluoroquinolone (MI C50 <e; 0.5; 76.5% susceptibility) against this gram-negative species. These results show the unique pattern of bloodstream isolates for Latin America and they demonstrate the present utility of several classes of compounds against emerging antimicrobial-resistant species in this region.

Piperacillin/Tazobactam: Evaluation of Its In vitro Activity against Bacteria Isolated in Two Brazilian Hospitals and an Overview of Its Antibacterial Activity, Pharmacokinetic Properties and Therapeutic Potential.

Piperacillin/tazobactam is a highly active antibiotic against most clinically important species of Gram-negative and positive bacteria, including anaerobes. It has never been used or tested against bacteria isolated in Brazil. In this article we report the in vitro activity of piperacillin/tazobactam against clinical isolates from two tertiary hospitals in São Paulo and Rio de Janeiro and review the evolving clinical literature. The study was performed before its commercialization in Brazil. Its activity was compared to that of several broad-spectrum antimicrobial agents commercially available in Brazil. Piperacillin/tazobactam was active against 83% of the isolates tested, while imipenem was active against 91%, cefepime 77%, and ciprofloxacin 73%. Against Enterobacteriaceae (n=398), cefepime was more active than piperacillin/tazobactam (92% versus 88%). Klebsiella pneumoniae strains (n=95) presented low susceptibility to piperacillin/tazobactam (79%), ceftazidime (67%), and to cefepime (82%) indicating a high percentage of ESBL-producing strains. The most active compounds against this species were imipenem (100%) and ciprofloxacin (93%). Piperacillin/tazobactam was the most active compound against Gram-positive cocci (n=238; percentage of susceptibility rank order: piperacillin/tazobactam = imipenem > ciprofloxacin > cefepime) and the second most active against nonenteric Gram-negative bacilli (n=250, rank order: imipenem [72%] > piperacillin/tazobactam [60%] > cefepime [56%] > ceftazidime [52%] > gentamicin [45%] > ciprofloxacin = aztreonam [42%]). Cefepime was the most active compound against P. aeruginosa (n=128, only 67%), followed by ceftazidime (64%), piperacillin/tazobactam (63%) and imipenem (59%). Only imipenem (91%) was active against more than 50% of the A. baumannii isolates (n=79) tested. Piperacillin/tazobactam was the second most active compound against A. baumannii (49%) and the most active against B. cepacia (91%). Our results demonstrated a high level of antimicrobial resistance in the hospitals evaluated, especially among nonenteric Gram-negative bacilli; and clonal dissemination of multiresistant strains. Piperacillin/tazobactam may contribute to the treatment of nosocomial infections in Brazil, however, some degree of resistance was detected in some species in the instance of frequent multiresistant bacteria in the tertiary level hospitals where the drug was evaluated.

Antimicrobial Susceptibility of Klebsiella pneumoniae Producing Extended-Spectrum beta-lactamase (ESBL) Isolated in Hospitals in Brazil.

The prevalence of klebsiella pneumoniae producing extended-spectrum beta-lactamase (ESBL) has been increasing all over the world. Infections caused by ESBL producing isolates are difficult to detect with current susceptibility tests, and are difficult to treat. ESBLs confer resistance to all currently available beta-lactam, except carbapenems. In addition, ESBL production is usually associated with resistance to other classes of antimicrobial agents such as aminoglycosides and quinolones. The objective of this study was to evaluate the in vitro susceptibility patterns of ESBL producing K pneumoniae isolated in Brazil. Seventy-two strains were tested using E test against 30 antimicrobial agents, including carbapenems, second and third generation cephalosporins, aminoglycosides, quinolones, and some new compounds. The most active compounds (i.e. 100% susceptibility) were meropenem (MIC90, 0.125µg/mL), imipenem (MIC90, 0.25µg/mL), and cefotetan (MIC90, 2µg/mL). Ciprofloxacin (MIC90, 1µg/mL, 94% susceptibility) and cefepime (MIC90, 6µg/mL, 92% susceptibility), were also very active against our collection of ESBL producing K pneumoniae. None of the six aminoglycosides showed good activity against these strains (16% to 41% susceptibility) and only 39% of the isolates were susceptible to piperacillin/tazobactam. The results of our study indicated that the carbapenems are the most active compounds against ESBL producing L pneumoniae in Brazil, and ciprofloxacin remains very active against these strains. Cefotetan and cefepime were also very active against ESBL producing K.pneumoniaein Brazil; however, further studies are necessary to evaluate the role of these cephalosporins in the treatment of infections due to ESBL producing strains.

Comparative in vitro Activity of Meropenem Versus Other Extended-Spectrum Antimicrobial Agents Against 2,085 Clinical Isolates Tested in 13 Brazilian Centers.

Meropenem is a parenteral carbapenem antibacterial agent with a very broad spectrum of antibacterial activity. It is the second agent of its class to become available in Brazil. The in vitro antibacterial activity of meropenem was compared with imipenem and four other antimicrobial agents in a multicenter study. This study involved 13 clinical microbiology laboratories, 10 of which came from 8 Brazilian states. A total of 2,085 clinical isolates consecutively collected between December 1995 and March 1996 were susceptibility tested using the Etest and following the NCCLS procedures. Meropenem inhibited more than 90% of isolates of Enterobacteriaceae at 0.5 µg/mL, except for Citrobacter sp. (1 µg/ml). Generally, meropenem was slightly more active than imipenem against Gram-negative organisms and its spectrum of antimicrobial activity was broader than those of all other drugs tested. Against Pseudomonas aeruginosa, meropenem (MIC50, 0.38 µg/ml) was approximately 8-fold more active than imipenem (MIC 50,3 µg/mL). Imipenem was two-to eight-fold more active than meropenem against some Gram-positive specees oxacillin, including Enterococcus faecalis (MIC 50 of 0.75 µg/mL and 2 µg/mL respectively), oxacillin-susceptible Staphylococcus aureus (MIC 50 of 0.47 &mul;g/mL and 0.094 µg/mL), oxacillin-susceptible Staphylococcus epidermidis (MIC 50 of 0.064 µg/mL and 0.5mg/mL). Against Streptococcus sp. meropenem was slightly more active than imipenem (MIC 50, 0.016 µg/mL). The results of this study may be used to guide empiric therapy in Brazil and indicates that meropenem may have an important role in the treatment of infections caused by multiresistant strains of bacteria.