First Detection of the Antiseptic Resistance GeneqacA/B inEnterococcus faecalis

Abstract

Resistance to disinfectants is well investigated in staphylococci and pseudomonads but nearly unexplored in bacteria of the genus Enterococcus, despite their rising significance as nosocomial pathogens. In this study, Enterococcus faecalis (n=585) from blood (n=42) and stool (n=109) of hospitalized humans, from faeces of farm animals (n=226), and from food (milk and dairy products, n=96; meat and meat products, n=112) were screened for the presence of qac-genes (qacA, qacB, qacC, smr [qacC+qacD], qacEΔ1, qacG, qacH, qacJ) via PCR. The isolates' susceptibility to a quaternary ammonium compound (didecyldimethylammoniumchloride, DDAC) and antibiotics was assessed by microdilution. Four E. faecalis strains were positive for qac-genes: qacA/B was found in one isolate from cattle and one isolate from human blood; smr (qacC+qacD) was detected in one isolate from human stool and in one isolate from cheese ("Camembert"). The sequences of the qacA/B-amplicons differed in two basepairs. DDAC had an elevated minimum inhibitory concentration (MIC) of 2.45-3.5 mg/L in one qacA/B-positive strain from human blood, whereas the other qac-gene carriers had wild-type MIC-values for DDAC (1.05 mg/L). This is the first detection of qacA/B in the genus Enterococcus.

Insusceptibility to disinfectants in bacteria from animals, food and humans—is there a link to antimicrobial resistance?

“…All Enterococcus strains ( n = 954) were collected and identified in the frame of the second Bavarian antimicrobial resistance monitoring project (BAVMAP II, Bischoff et al, 2012) by species-specific PCR as previously described (Bischoff et al, 2012). Isolates from disinfectant boot bath were taken in three different ways:…”

Emergence of resistance to antibacterial agents: the role of quaternary ammonium compounds—a critical review

“…In S. aureus, biocide exporters are typically MFS proteins such as QacA/B [39,40], or SMR proteins such as QacC/D, Ebr [39,40], QacG [41], QacH [42], QacE 1 [43] and QacJ [36]. Recently, Enterococcus faecalis was found to express the antiseptic resistance gene qacA/B [44] in addition to SMR [45] and QacE 1 [43] determinants. These genes were plasmid-encoded with resistance attributable to plasmid acquisition.…”

Chlorhexidine bathing for the prevention of colonization and infection with multidrug-resistant microorganisms in a hematopoietic stem cell transplantation unit over a 9-year period

“…Indeed, cases of CHG minimum inhibitory concentration (MIC) increase have been reported mainly for Staphylococcus aureus [13] and Enterococci spp. [14] isolates. Efflux-pump genes ( cepA , qacAE , and qacE ) have been identified and associated with gram-negative bacterial strains with high CHG MICs.…”