Clinical and Molecular Characteristics of qacA - and qacB -Positive Methicillin-Resistant Staphylococcus aureus Causing Bloodstream Infections

Abstract

The increasing use of chlorhexidine for methicillin-resistant Staphylococcus aureus (MRSA) decolonization has raised concerns about the emergence of resistance to these agents. However, the clinical significance of MRSA positive for the qacA and qacB chlorhexidine tolerance genes has not been established. We investigated the clinical features and predictive factors of MRSA bloodstream infection (BSI) isolates, caused by qacA-and qacB-positive MRSA, from 2010 to 2016 at a tertiary hospital in South Korea. A total of 246 MRSA BSI isolates were included; 71 (28.9%) isolates carried qacA/B. The annual frequency of qacA-and qacB-positive MRSA bacteremia did not change significantly over the study period. Patients infected with qacA-and qacB-positive MRSA had common risk factors for health care-associated infections, including prior antibiotic use, central venous catheterization in situ, intensive care unit-acquired bacteremia, and nosocomial infection. The qacA-and qacBpositive isolates were also associated with an increasing chlorhexidine MIC and resistance to non-␤-lactam antibiotics. The qacA-and qacB-positive isolates were more likely to belong to sequence type 5 (ST5), which is a common health care-associated MRSA strain in South Korea. In multivariable analyses, qacA-and qacB-positive MRSA isolates were found to be associated with agr dysfunction (adjusted odds ratio [aOR], 6.45; 95% confidence interval [CI], 2.59 to 16.10), ST5 MRSA strain (aOR, 4.96; 95% CI, 1.85 to 13.26), nosocomial infection (aOR, 4.88; 95% CI, 2.20 to 10.83), and antibiotic use within the previous 3 months (aOR, 2.59; 95% CI, 1.20 to 5.59). These findings suggest that the microbiological features of qacA and qacB carriage provide a selective advantage for specific MRSA strains in hospital environments.

Decreased Incidence of Methicillin-Resistant Staphylococcus aureus Bacteremia in Intensive Care Units: a 10-Year Clinical, Microbiological, and Genotypic Analysis in a Tertiary Hospital

“…Interestingly, the t2460 spa type has been identified mostly in Asia (24)(25)(26), and t2460 isolates reported from China carried qacA or qacB genes (22,27). In South Korea, both t2460 and t9353 are the major spa types of MRSA (28)(29)(30), and t2460 was reported to be associated with qacA or qacB genes (29). In addition, there was an increase in the proportion of low-level mupirocin resistance.…”

Stress response modulation: the key to survival of pathogenic and spoilage bacteria during poultry processing

“…It has been found that clinical S. aureus isolates carrying the qacA and qacB QAC resistance genes require an increased minimum inhibitory concentration of chlorhexidine and display increased resistance to β-lactam antibiotics [112]. These pumps are a common effective means of increasing cell tolerance to antimicrobial substances [52, 76].…”

“…The Gram-positive QacA efflux pump family is activated by a broad range of antimicrobial agents (such as QAC-containing compounds), and is capable of extruding a wide variety of cationic substances from the cell cytoplasm [37]. It has been found that clinical S. aureus isolates carrying the qacA and qacB QAC resistance genes require an increased minimum inhibitory concentration of chlorhexidine and display increased resistance to β-lactam antibiotics [112]. These pumps are a common effective means of increasing cell tolerance to antimicrobial substances [52,76].…”

Bacterial Targets of Antibiotics in Methicillin-Resistant Staphylococcus aureus

“…The QacA/B, NorA, and Smr multidrug efflux proteins are present on the S. aureus cell membrane [ 29 , 30 ]. MRSA harboring qacA and qacB genes has been found to be associated with increased resistance to non-β-lactam antibiotics and chlorhexidine tolerance [ 31 ].…”