Ability of Latin America laboratories to detect antimicrobial resistance patterns: experience of the SENTRY antimicrobial surveillance program (1997-2000)

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 percent of the antimicrobial agent-organism combinations. "Very major" (false-susceptible results) and "major errors" (false-resistant results) were observed in 12 percent and 6 percent of the cases, respectively. The highest disagreements were observed for coagulase-negative Staphylococcus - oxacillin (20 percent - very major error) and Burkholderia cepacia - imipenem (21 percent - very major error). The susceptibility method with the highest agreement rate was Etest« (92 percent) > PASCO« (91 percent) > agar dilution (91 percent) > MicroScan« (90 percent) > Vitek« (87 percent). 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.

Comparação das atividades antimicrobianas de meropenem e imipenem/cilastatina: o laboratório necessita testar rotineiramente os dois antimicrobianos? / Comparative antimicrobial activity between meropenem and imipenem/cilastatina: does the clinical laboratory need to test both imipenem and meropenem routinely?

O meropenem e o imipenem representam os ßðlactâmicos 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 gramðnegativos, enquanto que o imipenem é discretamente mais ativo contra gramðpositivos. Os objetivos deste estudo são comparar as atividade in vitro destes dois carbapenêmicos e avaliar a necessidade de o laboratório clínico testáðlos em sua rotina. Os resultados da avaliação dos padrões de sensibilidade de 2.144 bacilos gramðnegativos 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 1 µg/ml) também apresentou atividade superior à do imipenem (CIM50 de 1 µg/ml para ambos). Somente 2,7 por cento das amostras avaliadas apresentaram resultados discordantes entre os dois carbapenêmicos em termos de categoria de sensibilidade ð isto é, foram sensíveis a um e resistentes ao outro. Quarenta e seis amostras (2,14 por cento) foram sensíveis ao meropenem e resistentes ao imipenem, enquanto que somente 12 amostras (0,55 por centro) apresentaram sensibilidade ao imipenem e resistência ao meropenem. A grande maioria dos resultados discordantes (91,4 por centro) ocorreu entre as amostras de bacilos gramðnegativos nãoðfermentadores da glicose (BGNðNF). Entre as 1.350 enterobactérias testadas houve apenas cinco resultados discordantes (0,37 por cento), enquanto que entre os BGNðNF ocorreram 53 (6,67 por cento). Além disso, em cerca de 80 por cento, 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 BGNðNF, o laboratório deve realizar o teste de sensibilidade com os dois carbapenêmicos separadamente

Patogen frequency and resistance patterns in brazilian hospitals: summary of results from three years of the sentry antimicrobial surveillance program

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 occurence and antimicrobial susceptibility to patogenic 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 conclusiones: 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 patogen in general (22.8 percent-852 isolates), followed by E. coli (13.8 percent - 516 cases) and pseudomonas aeruginosa (13.3 percent - 496 cases). Staphylococcus aureus was also the most common species isolated from BSI (23.6 percent) and WSSTI (45.8 percent), and P.aeruginosa was the most frequent species isolated from patients with LRTI (29.4 percent). The main bacterial resistance problems found in this study were: imipenem resistance among P.aeruginosa (69.8 percent susceptibility) and Acinetobacter spp. (88.1 percent susceptibility): ESBL production among K. pneumoniae (48.4 percent) and E. coli (8.9 percent); resistance to third generation cephalosporin among Enterobacter spp. (68.1 percent susceptible to ceftazidime) and oxacillin resistance among S. aureus (34.0 percent) and coagulase negative staphylococci (80.1 percent). Only the carbapenems (88.1 percent to 89.3 percent susceptibility) showed reasonable activity against the Acinetobacter spp. isolates evaluated.

Perfil de sensibilidade a antimicrobianos de bactérias isoladas do trato respiratório baixo de pacientes internados em hospital brasileiros - Resultados do Programa SENTRY, 1997 e 1998 / Antimicrobial suspeceptibility of bacteria isolated from the lower respiratory tract of impatients with pneumonia in Brazilian hospital - Results from the SENTRY surveillance program, 1997 and 1998

INTRODUÇÄO: Pneumonia hospitalar é a mais fatal das infecçöes hospitalares, com taxas de mortalidade de 30 a 60 por cento. Estima-se que 15 por cento de todas as mortes associadas à hospitalizaçäo estejam diretamente relacionadas a pneumonia hospitalar. 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 hospital brasileiro. MATERIAL E MÉTODOS: Foram avaliadas 525 amostras bacterianas de 11 hospitais brasileiros, como parte do programa SENTRY. Os isolados foram testados por microdiluiçäo em caldo contra um grande número de antimicrobianos. RESULTADOS: As cinco espécies mais freqüentes foram (n/por cento): Pseudomonas aeruginosa (158/30,1 por cento), Staphylococcus aureus (103/19,6 por cento), acinetobacter spp. (68/13,0 por cento), Klebsiella spp. (50/9,5 por cento), e Enterobacter spp. (44/8,4 por cento). Essas cinco espécie representam mais de 80 por cento 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 por cento) e meropenem (69,0 por cento). Os compostos com maior atividade in vitro contra Acinetobacter spp. foram imipenem e meropenem (80,9 por cento de sensibiliade) seguido pela tetraciclina (63,2 porcento). A sensibilidade das amostras de Klebsiella spp. foi muito baixa. MIC = ug/mL para ceftriaxona ou ceftazidima, indicando produçäo de ESBL, foram os cabapenens (100 por cento de sensibilidade) e as quinolonas (92,0 por cento de sensibilidade). Ceftrixona foi ativa contra somente 56,8 por cento da amostras de Enterobacter spp. (MIC50, ó 1ug/mL), enquanto a cefapima foi detectada em 43,7 por cento dos isolados de S. aureus. As drogas mais ativas contra essa espécie foram: vancomicina, teicoplanina, quinupristin-dalfopristin e linezolida. CONCLUSÄO: 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

In vitro antimicrobial activity of piperacillin/tazobactam in comparison with other broad-spectrum ß-Lactams

Combinig tazobactam, a ß-lactamase inhibitor, with the ureidopenicillin, piperacillin, successfully restores the activity of piperacillin against ß-lactamase producing bacteria. Thus, piperacillin/tazobactam is highly active against most clinically important species of Gram-negative and Gram-positive bacteria, including anaerobes. We evaluated the in vitro activity of piperacillin/tazobactam against clinical isolates from a tertiary university hospital located in Säo Paulo, Brazil. Its activity was compared to the ticarcillin/ clavulanic acid, ampicillin/sulbactam, ceftazidimeceftriaxone, cefotaxime, cefoxitin, aztreonam and imipenem against 820 isolates (608 Gram-negative and 212 Gram-positive) collected from hospitalized patients in 1999. The most frequent species tested were Pseudomonas aeruginosa (168/20 por cento), Escherichia coli (139/17 por cento), Acinetobacter spp (131/16 porcento), and Staphylococcus aureus (76/9 por cento). Of the isolates studied, 30 por cento were from the blodstream, 16 porcento from the lower respiratory tract, and 11 por cento from surgical wounds or soft tissue. The isolates were susceptibility tested by the broth microdilution method according to NCCLS procedures. The isolates tested were highly resistant to most antimicrobial agents evaluated. Imipenem resistance was not verified among Enterobacteriaceae, and piperacillin/tazobactam was the second most active ß-lactam against this group of bacteria (80.0 por cento susceptibility). Extended-spectrum ß-lactamase production was very high among E. coli (approximately 20 por cento) and KLebsiella pneumoniae (approximately 40 por cento). Imipenem was uniformly active against these species (100 por cento susceptibility) and piperacillin/tazobactam was the second most active compound inhibiting 84.4 por cento of isolates. Pseudomonas aeruginosa was highly resistant to all ß-lactams evaluated and piperacillin/tazobactam was the most active compound against this species. Our results demonstrate an extremely high level of antimicrobial resistance in the hospital evaluated, especially among non-enteric Gram-negative bacilli. Due to this high level of resistence, piperacillin/tazobactam represents an important ciontribution to the treatment of nosocomial infections...