Carbapenem-resistant Pseudomonas aeruginosa outbreak in an intensive care unit of a teaching hospital

The genetic similarity of carbapenem-resistant Pseudomonas aeruginosa strains isolated in the Hospital Universitário São Francisco, Bragança Paulista, São Paulo, Brasil, was evaluated by pulsed field gel electrophoresis (PFGE). A unique clone was detected among 5 of 7 isolates, suggesting that cross-contamination might have played a role in the spread of carbapenem-resistant P. aeruginosa strains. Interestingly, a similar PFGE pattern was encountered in a P. aeruginosa strain isolated from Hospital São Paulo that was used as a PFGE control.

Antimicrobial susceptibility of Quinupristin/Dalfopristin tested against Gram-positive Cocci from Latin America: results from the global SMART (GSMART) surveillance study

Gram-positive cocci are important causes of both nosocomial and community-acquired infections, and antimicrobial resistance among these pathogens has become an important problem worldwide. Since resistance among these organisms can vary substantially by geographic location, we conducted a multicenter surveillance study with isolates from live Latin American countries (15 medical centers). Quinupristin/dalfopristin (formerly RP-59500) is a novel streptogramin combination with focused activity against Gram-positive cocci, many exhibiting emerging resistance. The in vitro activity of quinupristin/dalfopristin and 12 other antimicrobial agents were evaluated against 1,948 strains including Staphycoccus aureus (747 strains), coagulase-negative staphylococci (CoNS;446 strains), enterococci (429 strains), and various Streptococcus spp.(326 strains). Oxacillin resistance was observed in 41 percent of S. aureus (MIC,<2µg/ml or >13mm) and 40 percent of CoNS (MIC,<0.25µg/ml or >18mm). Vancomycin, teicoplanin, and quinupristin/dalfopristin (MIC90,,0.25-1µg/ml remained effective against all strains, but cross-resistance was high among other tested drugs. The quinupristin/dalfopristin MIC50 for Streptococcus pneumoniae and other streptococci was only 0.5µg/ml (13 percent to 28 percent were penicillin-resistant; 12 percent to 22 percent were macrolide-resistant). Enterococci demostrated variable inhibition by quinupristin/dalfopristin depending upon identification and the susceptibility testing method used. The demonstrated quinupristin/dalfopristin activity against Enterococcus faecium was confirmed, but potential species identification errors with various commercial systems continue to confuse susceptibility statistics, even though some strains of E. faecium confirmed by PCR-based or other molecular identification technique did have quinupristin/dalfopristin MICs of>4µg/mL. Most important, glycopeptide-resistant enterococci are rapidly emerging in Latin America, and quinupristin/dalfopristin appears active against many of these isolates as well as having potency against nearly all staphylococci and streptococci tested at<2µg/ml or having a zone diameter of>116mm. Comparisons to GSMART results from other continents show nerly identifical quinupristin/dalfopristin activity for each Gram-positive species tested. These results define the role of quinupristin/dalfopristin in Latin American medical centers and provide a bechmark for future in vitro comparisons.

Enterococcus faecalis resistant to vancomycin and teicoplanin (VanA Phenotype) isolated from a bone marrow transplanted patient in Brazil

We report for the first time in Brazil, patient from whom an Enterococcus faecalis VanA phenotype was isolated. Glycopeptide resistance is not commonly observed in Enterococcus faecalis, so this finding is of great concern since this species is responsible for 90 percent of enterococcal infections in Brazil. The isole was recovered from a surveillance rectal swab culture from a patient with acute lymphocytic (ALL). Identification to the species level was performed by conventional biomechanical tests and vitek GPI cards. Antimicrobial susceptibility testing was evaluated by use of broth microdilution and Etest (AB BIODISK, Solna, Sweden) methods. The isolate was identified as E. faecalis and was considered resistant to both vancomycin(MIC,>256µg/mL) and teicoplanin (MIC, 256 µg/mL). The isolate also showed high level resistance to gentamicin and streptomycin (MICs,>1024µg/mL), but was considered susceptible to ampicillin (MIC, 4µg/mL). Although the frequency of enterococcal infections is very low in most Latin American countries, the finding of glycopeptide (VanA) resistance in E. faecalis increases concern about apreading antimicrobial resistance in this region.

Evaluation of the in vitro activity of two fourth-generation cephalosporins against bacterial samples isolated from patients in several Brazilian Hospitals

Cefpirome and cefepime are two fourth-generation cephalosporins recently introduced in Brazil. They have a very similar range of in vitro antimicrobial activity, but some differences have been noticed. The goal of this study was to compare the in vitro activity of cefpirome and cefepime against bacterial samples isolated in Brazilian hospitals. We studied 931 samples taken from hospitalized patients between April and June, 1998. The minimum inhibitory concentration (MIC) was determined by the Etest method. The potency of cefpirome was similar to that of cefepime, except against enterococci and coagulase-negative staphylococci, where cefpirome proved 2-fold more potent. The MICs90 for cefepime were inferior to cefpirome in response to Klebsiella pneumoniae (MICs90, 24 and 96µg/mL, respectively), Pseudomonas aeruginosa (MICs90, 48 and 128µg/mL, respectively), and other Gram-negative organisms (MICs90, 64 and 256µg/mL, respectively). Despite the fact that cefpirome presented a slightly broader range of action against Gram-positive bacteria(90 percent sensitive vs. 78 percent sensitive to cefepime), and that cefepime presented an equally broad range against Gram-negative bacteria (74 percent sensitive vs. 65 percent sensitive to cefpirome), these differences were not considered clinically significant because the sensitivity differed in MIC by less than 2 dilutions. Only 16 (1.7 percent) of the 931 samples tested showed a significant difference in sensitivity. This study suggests that, except for Acinetobacter sp. and P. aeruginosa, laboratories may routinely test only cefpirome and apply the same category result to cefepime. Since category discrepancies are very rare and cefpirome is slightly less active than cefepime against Enterobacteriaceae, isolates susceptible to cefepime will certanly also be susceptible to cefpirome. To optimize the treatment of severely infected patients, especially where species such as Acinetobacter sp and P. aeruginosa are involved, we recommend that both cephalosporins be tested by using the same susceptibility test method to determine the MIC.

Avaliaçäo do sistema semi-automatizado microscan para identificaçäo de testes de sensibilidade de amostras de enterococos / Evaluation of the microscan semi-automated system for species identification and susceptibility testing of enterococci

O objetivo deste estudo foi avaliar a acurácia de um sistema semi-automatizados, os painéis convencionais MicroScan Positive Breakpoint Combo Type 6 (Dade MicroScan Inc., West Sacramento, CA), para identificaçäo de espécie, avaliaçäo da sensibilidade à vancomicina e à ampicilina e detecçäo de alto grau de resistência à gentamicina (HLRGN) e à estreptomicina (HLRST). Esse método foi comparado com a identificaçäo bioquímica convencional e com o método de diluiçäo em ágar (DA) para avaliaçäo de sensibilidade a antimicrobianos. Dentre as 211 amostras testadas (184 E.faecalis, 21 E.faecium e 6 näo-faecalis-näo-faecium), 95 por cento dos E.faecalis e 67 por cento dos E.faecium foram idetificados corretamente pelo MicroScan. O microScan apresentou 99,5 por cento de concordância com o método de DA para testes de sensibilidade à vancomicina e o HLRGN e o HLRST foi detectado em 92 por cento (33/36) e 84 por cento (31/37) das amostras, respectivamente. Os resultados do presente estudo mostram que este método semi-automatizado apresenta dificuldades na identificaçäo de espécies diferentes de E.faecalis, além de elevadas taxas de erros muito graves para ampicilina (11 por cento), gentamicina (8 por cento) e estreptomicina (16 por cento)