Beta-lactams susceptibility testing of penicillin-resistant, ampicillin-susceptible Enterococcus faecalis isolates: a comparative assessment of Etest and disk diffusion methods against broth dilution.

This study aimed to evaluate the accuracy of disk diffusion and Etest methods, compared to that of the broth dilution reference method for identifying beta-lactam susceptibilities of Penicillin-Resistant, Ampicillin-Susceptible Enterococcus faecalis (PRASEF) isolates. Fifty-nine PRASEF and 15 Penicillin-Susceptible, Ampicillin-Susceptible E. faecalis (PSASEF) clinical nonrepetitive isolates were evaluated. The effectiveness of five beta-lactams (ampicillin, amoxicillin, imipenem, penicillin, and piperacillin) was tested. All antimicrobial susceptibility tests were performed and interpreted according to the Clinical and Laboratory Standards Institute guidelines. Interpretative discrepancies, such as essential agreement, categorical agreement, and errors, were assessed. The acceptability was ≥ 90% for both categorical agreement and essential agreement. Etest proved to be an accurate method for testing beta-lactam susceptibilities of the emerging PRASEF isolates, disk diffusion presented poor performance, particularly for imipenem and piperacillin.

Penicillin-resistant, ampicillin-susceptible Enterococcus faecalis of hospital origin: pbp4 gene polymorphism and genetic diversity.

Despite the spread of penicillin-resistant, ampicillin-susceptible Enterococcus faecalis (PRASEF) isolates in diverse countries, the mechanisms leading to this unusual resistance phenotype have not yet been investigated. The aim of this study was to evaluate whether polymorphism in the pbp4 gene is associated with penicillin resistance in PRASEF isolates and to determine their genetic diversity. E. faecalis isolates were recovered from different clinical specimens of hospitalized patients from February 2006 to June 2010. The ß-lactam minimal inhibitory concentrations (MICs) were determined by E-test®. The PCR-amplified pbp4 gene was sequenced with an automated sequencer. The genetic diversities of the isolates were established by PFGE (pulsed-field gel electrophoresis) and MLST (multilocus sequencing typing). Seventeen non-producing ß-lactamase PRASEF and 10 penicillin-susceptible, ampicillin-susceptible E. faecalis (PSASEF) strains were analyzed. A single-amino-acid substitution (Asp-573→Glu) in the penicillin-binding domain was significantly found in all PRASEF isolates by sequencing of the pbp4 gene but not in the penicillin-susceptible isolates. In contrast to the PSASEF isolates, a majority of the PRASEFs had similar PFGE profiles. Six representative PRASEF isolates were resolved by MLST into ST9 and ST524 and belong to the globally dispersed clonal complex 9 (CC9). In conclusion, it appears quite likely that the amino acid alteration (Asp-573→Glu) found in the PBP4 of the Brazilian PRASEF isolates may account for their reduced susceptibility to penicillin, although other resistance mechanisms remain to be investigated.

Ampicillin susceptibility can predict in vitro susceptibility of penicillin-resistant, ampicillin-susceptible Enterococcus faecalis Isolates to amoxicillin but not to imipenem and piperacillin.

Our findings demonstrated that the results obtained for ampicillin may accurately predict the in vitro susceptibility to amoxicillin but not to imipenem and piperacillin among isolates of Enterococcus faecalis resistant to penicillin but susceptible to ampicillin, which have emerged recently, in contrast to penicillin- and ampicillin-susceptible isolates.

Analysis of the -398C/T polymorphism in the perforin gene in oncohematological patients.

BACKGROUND: Recently, single nucleotide polymorphisms (SNPs) were identified in the promoter region of the perforin gene (PRF1) and it was found that the -398T mutant allele is correlated with lower amounts of protein in circulating CD8(+) cytotoxic T lymphocytes. OBJECTIVE: The aim of this study was to investigate the presence of the -398C/T polymorphism in the perforin gene in oncohematological patients. METHODS: Sixty-two patients with hematological malignancies treated at the teaching hospital of the Universidade Federal do Triângulo Mineiro were invited to participate in this study. The identification of the polymorphism was achieved by amplification using polymerase chain reaction, digestion using the TaqI enzyme and electrophoresis in 1% agarose gel. RESULTS: The heterozygous -398C/T polymorphism was identified in 16.7% patients with acute lymphoblastic leukemia, 40% with multiple myeloma, 50% with essential thrombocythemia, 14.3% with Hodgkin's disease, 7.7% with non-Hodgkin lymphoma and 33.3% with chronic lymphocytic leukemia. The homozygous mutant allele was identified in one mulatto individual (25%) with myelodysplastic syndrome. When Afro-Brazilian and Whites were analyzed together, there was a higher frequency of the -398T allele in patients than in healthy individuals (p-value = 0.0291). CONCLUSION: ne patient was homozygous for the -398T allele. Based on these findings, further studies should be conducted to assess whether the presence of this polymorphism may be a risk factor for the development of hematologic malignancies.