The accuracy of antimicrobial susceptibility tests is a crucial step for the clinical management of patients with serious infections. They must be reliable and precise because they will guide antimicrobial therapy. Our main objective was to compare the results of susceptibility testing performed by the SENTRY coordinator laboratory with those reported by the participating Latin American medical centers. A total of 10,277 bacterial isolates were tested by the reference broth microdilution method at the coordinator laboratory in the United States. The tests were performed and interpreted following the National Committee for Clinical Laboratory Standards (NCCLS) recommendations. Ten antimicrobial agent-organism combinations were analyzed. The susceptibility methods utilized in each of the medical centers were also evaluated. Total agreement of the results was obtained in nearly 88% of the antimicrobial agent-organism combinations. "Very major" (false-susceptible results) and "major errors" (false-resistant results) were observed in 12% and 6% of the cases, respectively. The highest disagreements were observed for coagulase-negative Staphylococcus - oxacillin (20% - very major error) and Burkholderia cepacia - imipenem (21% - very major error). The susceptibility method with the highest agreement rate was Etest® (92%) > PASCO® (91%) > agar dilution (91%) > MicroScan® (90%) > Vitek® (87%). External quality assurance data obtained by surveillance programs such as the SENTRY Antimicrobial Surveillance Program are not only helpful for detecting the emergence of patterns of antimicrobial resistance, but also to monitor the performance of the participating microbiology laboratories.

O meropenem e o imipenem representam os ß-lactâmicos com maior espectro e potência antimicrobiana, e são os únicos carbapenêmicos disponíveis para uso clínico no Brasil, nos Estados Unidos e na Europa. O meropenem apresenta atividade in vitro superior contra gram-negativos, enquanto que o imipenem é discretamente mais ativo contra gram-positivos. Os objetivos deste estudo são comparar as atividades in vitro destes dois carbapenêmicos e avaliar a necessidade de o laboratório clínico testá-los em sua rotina. Os resultados da avaliação dos padrões de sensibilidade de 2.144 bacilos gram-negativos pela técnica de microdiluição em caldo foram analisados. Contra enterobactérias, o meropenem apresentou atividade pelo menos oito vezes maior que o imipenem. Contra Pseudomonas aeruginosa, o meropenem (CIM50 de 1mig/ml) também apresentou atividade superior à do imipenem (CIM50 de 2mig/ml), e contra Acinetobacter baumannii, a ação dos dois é equivalente (CIM50 de 1mig/ml para ambos). Somente 2,7% das amostras avaliadas apresentaram resultados discordantes entre os dois carbapenêmicos em termos de categoria de sensibilidade - isto é, foram sensíveis a um e resistentes ao outro. Quarenta e seis amostras (2,14%) foram sensíveis ao meropenem e resistentes ao imipenem, enquanto que somente 12 amostras (0,55%) apresentaram sensibilidade ao imipenem e resistência ao meropenem. A grande maioria dos resultados discordantes (91,4%) ocorreu entre as amostras de bacilos gram-negativos não-fermentadores da glicose (BGN-NF). Entre as 1.350 enterobactérias testadas houve apenas cinco resultados discordantes (0,37%), enquanto que entre os BGN-NF ocorreram 53 (6,67%). Além disso, em cerca de 80%, as amostras foram sensíveis ao meropenem e resistentes ao imipenem. Os resultados deste estudo indicam que o laboratório de microbiologia pode testar apenas um dos carbapenêmicos contra enterobactérias, considerando para o outro o mesmo resultado. É importante que os resultados dos dois carbapenêmicos sejam colocados no relatório, para que o médico possa escolher aquele que achar mais adequado. Por outro lado, para os BGN-NF, o laboratório deve realizar o teste de sensibilidade com os dois carbapenêmicos separadamente.

Meropenem and imipenem are the most active and potent ß-lactams against gram-negative bacteria and the only carbapenems commercially available in Brazil, USA, and Europe. Meropenem has higher in vitro activity against gram-negative bacteria, while imipenem has slightly higher in vitro activity against gram-positive. The objectives of this study are to compare the in vitro activities of these carbapenems and to evaluate the necessity of susceptibility testing both compounds at the routine of the microbiology laboratory. The broth microdilution results of 2,144 gram-negative bacilli were analyzed. Against Enterobacteriaceae meropenem was at least eight-fold more potent than imipenem. Against Pseudomonas aeruginosa meropenem (MIC50, 1mug/ml) was also more potent than imipenem (MIC50, 2mug/ml), and against Acinetobacter baumannii both carbapenems presented similar in vitro activities (MIC50, 1mug/ml for both). Only 2.7% of the isolates presented discrepant category results between the carbapenems; i.e. susceptible to one and resistant to the other. Forty-six isolates (2.14%) were susceptible to meropenem and resistant to imipenem; while only 12 isolates (0.55%) were susceptible to imipenem and resistant to meropenem. The vast majority of discordant results (91.4%) occur among non-fermentative bacilli (NF-BGN). Five discordant results were detected among 1,350 Enterobacteriaceae evaluated (0.37%); while 53 discrepant results were detected among 794 NF-BGN (6.64%). Isolates showing susceptibility to meropenem and resistance to imipenem account for 80% of the discrepant results. The results of this study indicate that the microbiology laboratory may susceptibility test only one of the carbapenems for Enterobacteriaceae and use the same category result for the other one. It is important that the results for both carbapenems are sent to the physicians in order for them to be able to choose the most appropriated for the case. On the other hand, for NF-BGN the laboratory should susceptibility test both carbapenems.

BACKGROUND: Pathogen frequency and resistance patterns may vary significantly from country to country and also in different hospitals within a country. Thus, regional surveillance programs are essential to guide empirical therapy and infection control measures. METHODS: Rank order of occurrence and antimicrobial susceptibility of pathogenic species causing bloodstream infections (BSI), lower respiratory tract infections (LRTI), wound or skin and soft tissue infections (WSSTI), and urinary tract infections (UTI) in hospitalized patients were determined by collecting consecutive isolates over a specified period of time, as part of the SENTRY Antimicrobial Resistance Surveillance Program (SENTRY). All isolates were tested by reference broth microdilution. RESULTS AND CONCLUSIONS: A total of 3,728 bacterial strains were obtained from January, 1997, to December, 1999, from 12 Brazilian hospitals located in 4 states. The largest number of isolates were obtained from patients with BSI (2,008), followed by LRTI (822 cases), UTI (468 cases), and WSSTI (430 cases). Staphylococcus aureus was the most frequently isolated pathogen in general (22.8% - 852 isolates), followed by E. coli (13.8% - 516 cases) and Pseudomonas aeruginosa (13.3% - 496 cases). Staphylococcus aureus was also the most common species isolated from BSI (23.6%) and WSSTI (45.8%), and P. aeruginosa was the most frequent species isolated from patients with LRTI (29.4%). The main bacterial resistance problems found in this study were: imipenem resistance among P. aeruginosa (69.8% susceptibility) and Acinetobacter spp. (88.1% susceptibility); ESBL production among K. pneumoniae (48.4%) and E. coli (8.9%); resistance to third generation cephalosporins among Enterobacter spp. (68.1% susceptible to ceftazidime) and oxacillin resistance among S. aureus (34.0%) and coagulase negative staphylococci (80.1%). Only the carbapenems (88.1% to 89.3% susceptibility) showed reasonable activity against the Acinetobacter spp. isolates evaluated.

Introdução: Pneumonia hospitalar é a mais fatal das infecções hospitalares, com taxas de mortalidade de 30 a 60%. Estima-se que 15% de todas as mortes associadas à hospitalização estejam diretamente relacionadas a pneumonias hospitalares. O SENTRY é um estudo de vigilância de resistência a antimicrobianos envolvendo centros médicos em todo o mundo. Objetivo: Avaliar a sensibilidade a antimicrobianos de bactérias isoladas no trato respiratório baixo de pacientes com pneumonia internados em hospitais brasileiros. Material e métodos: Foram avaliadas 525 amostras bacterianas de 11 hospitais brasileiros, como parte do programa SENTRY. Os isolados foram testados por microdiluição em caldo contra um grande número de antimicrobianos. Resultados: As cinco espécies mais freqüentes foram (n/%): Pseudomonas aeruginosa (158/30,1%), Staphylococcus aureus (103/19,6%), Acinetobacter spp. (68/13,0%), Klebsiella spp. (50/9,5%), e Enterobacter spp. (44/8,4%). Essas cinco espécies representam mais de 80% de toda a amostragem. A P. aeruginosa apresentou altas taxas de resistência à maioria dos antimicrobianos testados. As maiores taxas de sensibilidade foram apresentadas por piperacilina/tazobactam (71,5%) e meropenem (69,0%). Os compostos com maior atividade in vitro contra Acinetobacter spp. foram imipenem e meropenem (80,9% de sensibilidade) seguido pela tetraciclina (63,2%). A sensibilidade das amostras de Klebsiella spp. foi muito baixa. MICs > ou = 2mig/mL para ceftriaxona ou ceftazidima, indicando produção de ESBL, foram encontrados em 36,0% das amostras. Os antimicrobianos mais ativos contra Klebsiella spp. foram os carbapenens (100% de sensibilidade) e as quinolonas (92,0% de sensibilidade). Ceftriaxona foi ativa contra somente 56,8% das amostras de Enterobacter spp. (MIC50, 1mig/mL), enquanto a cefepima foi ativa contra 88,6% destes isolados (MIC50, <= 0,12mig/mL). A resistência à oxacilina foi detectada em 43,7% dos isolados de S. aureus. As drogas mais ativas contra essa espécie foram: vancomicina, teicoplanina, quinupristin-dalfopristin e linezolida. Conclusões: Os resultados do presente estudo mostraram alta prevalência de Acinetobacter spp. e altas taxas de resistência entre bacilos gram-negativos quando comparados com resultados de estudos norte-americanos e europeus.

Background: Nosocomial pneumonia is the most common fatal nosocomial infection with attributable mortality rates ranging from 30 to 60% and a rapid initiation of optimal antimicrobial therapy is important to obtain treatment success. SENTRY is a comprehensive antimicrobial surveillance study involving a great number of medical centers distributed worldwide. Objective: To evaluate the antimicrobial susceptibility of bacterial isolates collected from the lower respiratory tract of inpatients with pneumonia. Material & methods: The authors report the antimicrobial susceptibility of 525 isolates collected in 11 Brazilian hospitals, as part of the SENTRY program. The isolates were tested for susceptibility by broth micro-dilution against a large number of drugs. Results: The five most frequently isolated species were (n/%): Pseudomonas aeruginosa (158/30.1%), Staphylococcus aureus (103/19.6%), Acinetobacter spp. (68/13.0%), Klebsiella spp. (50/9.5%), and Enterobacter spp. (44/8.4%). These five species represented more than 80% of all isolates. P. aeruginosa demonstrated high rates of resistance to most antimicrobial agents tested. The highest susceptibility rates were shown by piperacillin/tazobactam (71.5%) and meropenem (69.0%). Acinetobacter spp. also showed very high rates of resistance. The most active compounds against this species were imipenem and meropenem (80.9% susceptibility) followed by tetracycline (63.2% susceptibility). Cephalosporin susceptibilities among Klebsiella spp were very low and 36.0% of isolates were considered ESBL producers based on increased MICs, > 2 mug/mL) to ceftriaxone or ceftazidime or aztreonam. Ceftriaxone was active against only 56.8% of Enterobacter spp. isolates (MIC50 1 mug/mL), while cefepime was active against 88.6% of these isolates (MIC, < 0.12 mg/mL). Oxacillin-resistance was detected in 43.7% of S. aureus isolates. The most active drugs against this species were vancomycin, teicoplanin, quinupristin/dalfopristin, and linezolid. Conclusion: The results of this study demonstrated a higher prevalence of Acinetobacter spp. and higher resistance rates among Gram-negative rods when compared with results from North American and European studies.