Susceptibility to chlorhexidine amongst multidrug-resistant clinical isolates of Staphylococcus epidermidis from bloodstream infections

Abstract

12Emergence of Staphylococcus isolates with reduced susceptibility to chlorhexidine is being 13 increasingly reported. We present an update to a previous report showing continuing efficacy 14 of chlorhexidine-based infection control measures against Staphylococcus aureus over six 15 years. We screened qacA/B genes in Staphylococcus isolates collected over another six 16 years in the same intensive therapy unit in Scotland where chlorhexidine baths form an 17 essential component of long-term control of nosocomial infections. Consistent with our 18 previous study we report minimal presence of qacA/B in S. aureus strains from screening 19 samples and bacteraemia patients but the new finding of a high proportion of qacA/B 20 carriage in Staphylococcus epidermidis associated to reduced susceptibility to chlorhexidine. potentially associated with resistance. Qac genes encode for proton-dependent efflux pumps 48 which are known to bind a variety of lipophilic cations including quaternary ammonium 49 compounds such as chlorhexidine. Of the genes known to be associated with biocide 50 resistance, qacA has been more strongly associated with decreased susceptibility to 51 chlorhexidine in Staphylococcus (8, 12). The QacB efflux pump carries amino acid 52 differences compared with QacA including a substitution from Asp to Ala which determines 53 inability to bind divalent cations (13). QacA/B genes are located on mobile genetic elements 54and their co-presence on plasmids with antibiotic resistance genes has pointed to the 55 possibility of cross-resistance between biocides and antibiotics in Staphylococcus (10, 14). 56However, it is yet unclear whether or not the presence of qac genes selects for the presence 57 of antibiotic resistance genes. 58Another medically important Staphylococcus species is Staphylococcus epidermidis. While 59 previously considered to be a non-pathogenic skin commensal, it is now recognized a key 60 opportunistic pathogen associated with nosocomial infections including bacteraemias. selected from patients screened at multiple body sites on admission over the whole period of 78 the study. Forty-one strains were obtained from blood cultures and comprised sixteen strains 79 of S. aureus and twenty-five strains of S. epidermidis. This was a random collection of strains 80 representing 12% and 32% of the total number of bacteraemias related to S. aureus and S. 81 epidermidis, respectively, that occurred over the study time period. For both screening 82 samples and blood cultures one isolate per patient was included in the study. The MRSA 83 infection control measures following screening have already been described (17). Bacterial 84 isolation and characterisation was carried out as previously described (17). 85 2.2DNA extraction: Genomic DNA was extracted from overnight pure cultures of the 86 Staphylococcus isolates using the High Pure PCR template preparation kit (Roche 87 Diagnostics, Germany) following the manufacturer's instructions. Samples were pre-treated 88 with 5µl of Lysozyme (Sigma,...

Disinfect Porphyromonas gingivalis Biofilm on Titanium Surface with Combined Application of Chlorhexidine and Antimicrobial Photodynamic Therapy

“…In addition, resistance to CHX is increasing and although cross‐resistance to antibiotics remains controversial, some studies indicate that the overall exposure to CHX increases the risk for resistance to some antibiotics . Furthermore, the resistance to CHX has resulted in some outbreaks and healthcare‐associated infections . In our study, CHX+ aPDT demonstrated better bactericidal effect than CHX alone against P. gingivalis on titanium surfaces.…”

Current and Emerging Topical Antibacterials and Antiseptics: Agents, Action, and Resistance Patterns

“…A more recent Scottish study included 25 S. epidermidis isolates obtained between 2007 and 2014 from a single hospital intensive care unit, and it showed a chlorhexidine tolerance rate of 12% by agar dilution assay. In both studies, there was an association between increased chlorhexidine tolerance and the carriage of qacA/B genes (231,232).…”

A novelqacAallele results in an elevated chlorhexidine glu conate minimum inhibitory concentration in cutaneousStaphylococcus epidermidisisolates

“…Previous studies have characterized three alleles of qacA : qacA1 , qacA2 , and qacA3 (18, 21). Additional studies, however, have suggested clinical and environmental Staphylococcus isolates may carry novel alleles of qacA (30, 31). Our identification of multiple novel qacA alleles supports this suggestion that considerably more qacA allelic variation exists within human staphylococcal populations than previously appreciated.…”