Antimicrobial susceptibility of Gram-negative bacteria in Brazilian hospitals: the MYSTIC Program Brazil 2003

Establish the susceptibility pattern of Gram-negative bacteria causing infections in ICU patients, MYSTIC Program Brazil 2003. Gram-negative bacteria (n = 1,550) causing nosocomial infections were collected at 20 Brazilian centers. The central laboratory confirmed the identification and performed the susceptibility tests by Etest methodology (AB Biodisk, Solna, Sweden) for meropenem, imipenem, ciprofloxacin, ceftazidime, cefepime, cefotaxime, piperacillin/tazobactam, gentamicin, and tobramycin. Interpretation criteria used were according to National Committee for Clinical Laboratory Standards (NCCLS). Pseudomonas aeruginosa (30.3 percent) was the most frequent isolate, followed by E. coli (18.6 percent), Klebsiella pneumoniae (16.9 percent), Acitenobacter baumannii (8.8 percent), and Enterobacter cloacae (7.1 percent). Pseudomonas aeruginosa (n=470) isolates presented susceptibility rates of 64 percent to meropenem, 63.8 percent to piperacillin/tazobactam, 63.4 percent to amikacin, 58.7 percent to imipenem. Acitenobacter baumannii presented susceptibility rates to meropenem of 97.1 percent, and 73 percent to tobramycin. E. coli and K. pneumoniae were highly susceptible to both carbapenems.Carbapenem resistance among the Enterobacteriaceae is still rare in the region. Acitenobacter baumannii and P. aeruginosa presented elevated resistance rates to all antimicrobials. Since they play an important role in nosocomial infections in this environment, the use of empirical combination therapy to treat these pathogens may be justified.

Antimicrobial susceptibility in intensive care units: MYSTIC Program Brazil 2002

OBJECTIVE: Establish the susceptibility pattern of Gram-negative bacteria causing infections in ICU patients, MYSTIC Program Brazil 2002. MATERIAL AND METHODS: Gram-negative bacteria (n = 503) causing nosocomial infections were collected at seven Brazilian centers. The central laboratory confirmed the identification and performed the susceptibility tests by E-test methodology (AB Biodisk, Solna, Sweden) for meropenem, imipenem, ciprofloxacin, ceftazidime, cefepime, cefotaxime, piperacillin/tazobactam, gentamicin, and tobramycin. Interpretation criteria used were according to National Committee for Clinical Laboratory Standards (NCCLS). RESULTS: Pseudomonas aeruginosa (33 percent) was the most frequently isolated, followed by A. baumannii (17.1 percent), K. pneumoniae (12.1 percent), E. coli (10.5 percent), and E. cloacae (7.9 percent). Pseudomonas aeruginosa isolates had susceptibility rates of 67.5 percent to piperacillin/tazobactam, 59.8 percent to meropenem, 57.3 percent to imipenem. A. baumannii presented susceptibility rates to meropenem of 89.5 percent, 88.4 percent to imipenem, and 74.4 percent to tobramycin. E. coli and K. pneumoniae were fully susceptible to both carbapenems. CONCLUSIONS: Carbapenem resistance among Enterobacteriaceae is still rare in this region. A. baumannii and P. aeruginosa presented elevated resistance rates to all antimicrobials. Since these two bacterial species play an important role in nosocomial infections, the use of empirical combination therapy to treat these pathogens may be justified.

Klebsiella pneumoniae with multiple antimicrobial resistance

A Klebsiella pneumoniae strain was isolated from the urine of a patient at one of the centers participating in the 2001 edition of the MYSTIC program in Brazil. The initial phenotypic findings of the isolated K. pneumoniae presented an unusual MIC of 8 ìg/mL to meropenem, 2 ìg/mL to imipenem, elevated MICs to broad spectrum cephalosporins (ceftazidime/cefotaxime/cefepime MIC > 256 ìg/mL), aminoglycosides (gentamycin > 256 ìg/mL and tobramycin = 48 ìg/mL), piperacillin/tazobactam (MIC > 256 ìg/mL) and susceptibility to ciprofloxacin (MIC = 0.25 ìg/mL). The strain also tested positive for ESBL production with double-disk and E-test methodologies. More detailed investigation revealed that the strain produced a SHV-4 type enzyme and also lacked a 36 kDa outer membrane porin.