hVISA bacteremia was significantly associated with prolonged bacteremia duration, greater rates of complications, and emergence of rifampin resistance, compared with MRSA bacteremia. However, no significant difference in mortality existed between patients with hVISA bacteremia and those with MRSA bacteremia.

Hashomer, Israel, were assessed for hVISA by using the Etest macromethod. A total of 16 patients (6%) were positive for hVISA. Resistance to teicoplanin alone and to vancomycin alone using the Etest macromethod was found in 14 and 10 patients, respectively. Standard MICs to vancomycin were between 1 to 4 mg/ml. Most of these isolates (12 of 16 [75%]) would have been missed without specific testing. The median number of bacteremic days was 4. Seven patients had positive blood cultures for more than 5 days. Twelve patients died, and for eight of these the deaths were directly related to hVISA sepsis. We found that hVISA bacteremia was prevalent in our institution, and we suggest seeking hVISA in patients with persistent S. aureus bacteremia.Infections due to methicillin-resistant Staphylococcus aureus (MRSA) are responsible for 50% of hospital acquired S. aureus infections with increasing morbidity and mortality (13). A recent meta-analysis demonstrated increased mortality in bacteremia associated with MRSA compared to methicillin-susceptible S. aureus (MSSA) (5). Glycopeptides are considered the drug of choice for treating MRSA bacteremia and sepsis. S. aureus strains with reduced vancomycin susceptibility were first reported in 1997 (9). S. aureus strains with reduced vancomycin susceptibility include vancomycin-resistant S. aureus strains (VRSA; MIC Ն 16 g/ml) and vancomycin-intermediate S. aureus strains (VISA; MIC ϭ 4 to 8 g/ml). Until 2006, the MIC for VISA was defined as 8 to 16 g/ml by the Clinical and Laboratory Standards Institute (CLSI; formerly the National Committee for Clinical Laboratory Standards), and these guidelines are still the ones approved by the U.S. Food and Drug Administration for vancomycin; the MIC for heterogeneous VISA (hVISA) strains was defined by the presence of subpopulations of VISA at a rate of 1 organism per 10 5 to 10 6 organisms (14,15,20,23). Up till April 2006 only four cases with infections due to VRSA have been reported, which exhibit the vanA gene complex found in vancomycin-resistant enterococci (2, 3, 12). A few dozen VISA strains have been reported in recent years, which have slower growth rates, thickened cell walls, and reduced levels of PBP4. The underlying genetic and biochemical mechanism by which this occurred is not known. The majority of these cases with VISA have occurred in patients who were treated with vancomycin for prolonged periods of time (7,11,19). hVISA seems to be the stage that precedes the development of VISA, and it is believed that vancomycin creates a selective pressure for these resistant strains (21).The best method for detecting hVISA is controversial. Methods are not standardized, and no clear guidelines have been issued. Population analysis profiling (PAP) is considered the gold standard, but this approach is labor-intensive and expensive. Thus, it is not realistic to use such a method for a routine service in a busy hospital setup. Various other methods used to detect hVISA were described and compared by Walsh et al. (22). Of the numerou...

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Rapid detection of drug-resistant bacteria in clinical samples plays an instrumental role in patients'infection management and in implementing effective infection control policies. In the study described in this report, we validated a multiplex TaqMan real-time quantitative PCR (qPCR) assay for the detection of bla KPC genes and the human RNase P gene in Bactec blood culture bottles. The MagNA Pure LC (version 2.0) instrument was utilized to extract nucleic acids from the inoculated broth, while bovine serum albumin (BSA) was utilized as the PCR inhibitor reliever. The multiplex assay, which was specific for the detection of bla KPC genes, had a limit of detection of 19 CFU per reaction mixture with human blood-spiked Bactec bottles. Of the 323 Bactec blood culture sets evaluated, the same 55 (17%) blood cultures positive for carbapenem-resistant bacteria by culture were also positive by the validated qPCR assay. Thus, the sensitivity, specificity, positive predictive value, and negative predictive value of the qPCR assay compared to the results of culture were all 100%. bla KPC genes were also detected from the same Bactec bottle broth after manual extraction with a QIAamp DNA minikit; however, there was an average 3-threshold-cycle delay in the qPCR readings. With the limited therapeutic options available, the accurate and rapid detection of bla KPC -possessing bacteria by the described bla KPC /RNase P assay will be a crucial first step in ensuring optimal clinical outcomes and infection control.