Recovery of susceptibility to penicillin G in clinical isolates of Streptococcus pneumoniae despite increased accumulation of pbp gene alterations.

Two hundred consecutive clinical isolates of Streptococcus pneumoniae isolated in 2005 and 2006 were analysed for susceptibility to various antimicrobials, pbp gene alterations and macrolide resistance gene expression (2007 analysis) and the results were compared with previous data (2003 analysis). The average minimum inhibitory concentration (MIC) of penicillin G in isolates with 1a(m)/2x(m)/2b(m) decreased from 1.135+/-0.503 mg/L in the 2003 analysis to 0.872+/-0.540 mg/L in the 2007 analysis (P=0.0046). The prevalence of isolates with 1a(m)/2x(m)/2b(m) increased from 30.5% to 32.3%, but the difference was not statistically significant (P=0.6979). The prevalence of isolates with a clarithromycin MIC > or = 1.0mg/L increased from 65.9% to 80.0% (P=0.0005). Isolates expressing ermB increased from 46.6% to 62.6% (P=0.0004). We conclude that the decrease in penicillin resistance of S. pneumoniae does not correlate with a decrease in pbp mutations; on the contrary, the prevalence of isolates with pbp mutations increased. A decrease in penicillin resistance in S. pneumoniae with pbp mutations appears to explain the present results regarding the recovery of penicillin susceptibility. Our results suggest that the spread of mutated pbp genes among S. pneumoniae itself is not responsible for acquisition of the penicillin-resistant phenotype. Use of beta-lactams, especially oral cephalosporins, appears to be responsible for the acquisition of penicillin resistance.

Undetected Bacillus pseudo-outbreak after renovation work in a teaching hospital.

A 602-bed capacity hospital underwent complete renovation from 1999 to 2004. In April 2005, the Infection Control Team was informed of the occurrence of three consecutive cases of Bacillus cereus bacteremia in a ward for patients with hematologic malignancies. A retrospective analysis of patients with Bacillus isolates was initiated. We found more Bacillus cereus isolates from blood samples in 2004 compare to the preceding years. Swab samples were collected in the particular ward from the surface of a working desk, filter unit of the air-conditioners, entrance of air inlet ducts, exit of the air outlet ducts and three-way valves of the particular ward under the consideration of iatrogenic contamination. Towels and gowns used in the ward were examined. Dens dust was noted in the filter of the air-conditioner and inlets/outlets of the air-ventilation system of the ward. Bacillus cereus was isolated from the dust, and from cleaned towels and gowns. PFGE fingerprinting differed among four patients' sample. We considered the present case as an undetected Bacillus cereus pseudo-outbreak that lasted for about one year after the renovation work of the hospital. We also considered that filters of the HVAC-system and towels and gowns were probable sources of the outbreak.