Octenidine exposure was not associated with reduced octenidine susceptibility of meticillin-resistant Staphylococcus aureus in an extended-care facility in Singapore.

OBJECTIVES: Antiseptics such as chlorhexidine gluconate (CHG) and octenidine dihydrochloride (OCT) are frequently used in hospitals to prevent and control the transmission of meticillin-resistant Staphylococcus aureus (MRSA). Given the increasing prevalence of reduced CHG susceptibility of MRSA, there are concerns about the possibility of reduced OCT susceptibility. This study evaluated the prevalence of reduced CHG and OCT susceptibility over 3 years, and assessed the association between OCT exposure and reduced OCT susceptibility in MRSA. METHODS: MRSA isolates from inpatients who acquired MRSA in an extended-care facility between 2019 and 2021 were included in antiseptic susceptibility testing. Inpatients were exposed to universal daily CHG bathing from January to September 2019, and universal daily OCT bathing after October 2019. The minimum inhibitory concentrations (MICs) of CHG and OCT were determined using the broth microdilution method. Multi-variable logistic regression was used to assess if OCT exposure was independently associated with reduced OCT susceptibility. RESULTS: Of 186 isolates, 179 (96%) had reduced CHG susceptibility (MIC ≥4 mg/L) and 46 (25%) had reduced OCT susceptibility (MIC ≥2 mg/L). Reduced OCT susceptibility rates were 26.9%, 13.8% and 14.3% in 2019, 2020 and 2021, respectively. Reduced CHG susceptibility rates were 95.4%, 100% and 95.9% in 2019, 2020 and 2021, respectively. OCT exposure was not associated with reduced OCT susceptibility (adjusted odds ratio 0.23, 95% confidence interval 0.08-0.75; P=0.014), after adjusting for age, gender, race, year of sample collection, days at risk in facility, hospitalization in preceding year, and MRSA colonization/infection in preceding year. CONCLUSION: The prevalence of reduced OCT susceptibility has remained low, despite universal OCT bathing for extended inpatient care. However, the rate of reduced CHG susceptibility was high. OCT exposure was not associated with reduced OCT susceptibility in MRSA.

Chlorhexidine and octenidine use, carriage of qac genes, and reduced antiseptic susceptibility in methicillin-resistant Staphylococcus aureus isolates from a healthcare network.

OBJECTIVES: With the widespread use of antiseptics in healthcare facilities for the prevention of methicillin-resistant Staphylococcus aureus (MRSA) transmission, there are concerns for antiseptic tolerance and resistance. We sought to understand the use of chlorhexidine and octenidine, carriage of qac genes, and reduced antiseptic susceptibilities. METHODS: A serial cross-sectional study was conducted in an acute care hospital and three extended-care facilities of a healthcare network in June-July, 2014-2016. Two of the extended-care facilities were exposed to intranasal octenidine and universal daily chlorhexidine/octenidine bathing. The minimum inhibitory concentration (MIC) levels and qac genes were determined by broth microdilution tests and whole genome sequencing respectively. Multivariable logistic regression was used to assess for the independent associations between antiseptic exposures, qac genes, and reduced antiseptic susceptibilities. RESULTS: A total of 878 MRSA isolates were obtained. There were associations between qacA/B carriage and chlorhexidine (adjusted odds ratio (aOR) 7.80; 95% confidence interval (CI) 3.25-18.71) and octenidine (aOR 11.79; 95% CI 5.14-27.04) exposures. Chlorhexidine exposure was associated with reduced chlorhexidine susceptibility (MIC ≥4 mg/L) (aOR 3.15; 95% CI 1.14-8.74). Carriage of qacA/B (aOR 10.65; 95% CI 4.14-27.40) or qacC (aOR 2.55; 95% CI 1.22-5.32) had an association with reduced chlorhexidine susceptibility; while MRSA sequence type modified the association. However, we found no direct association between (i) antiseptics use and qacC carriage, (ii) octenidine exposure and reduced susceptibility, and (iii) reduced octenidine susceptibility and qacA/B or qacC carriage. CONCLUSIONS: Antiseptic exposures were associated with carriage of qac genes. Chlorhexidine exposure was associated with reduced chlorhexidine susceptibility, requiring continued surveillance for the emergence of resistance.

Intranasal octenidine and universal antiseptic bathing reduce methicillin-resistant Staphylococcus aureus (MRSA) prevalence in extended care facilities.

Intranasal octenidine, an antiseptic alternative to mupirocin, can be used for methicillin-resistant Staphylococcus aureus (MRSA) decolonisation in the prevention of nosocomial transmission. A controlled before-after study was conducted in three extended-care hospitals in Singapore. All inpatients with >48 h stay were screened for MRSA colonisation in mid-2015(pre-intervention) and mid-2016(post-intervention). Hospital A: universal daily chlorhexidine bathing throughout 2015 and 2016, with intranasal octenidine for MRSA-colonisers in 2016. Hospital B: universal daily octenidine bathing and intranasal octenidine for MRSA-colonisers in 2016. Hospital C: no intervention. In 2015, MRSA prevalence was similar among the hospitals (Hospital A: 38.5%, Hospital B: 48.1%, Hospital C: 43.4%, P = 0.288). From 2015 to 2016, MRSA prevalence reduced by 58% in Hospital A (Adj OR 0.42, 95% CI 0.20-0.89) and 43% in Hospital B (Adj OR 0.57, 95% CI 0.39-0.84), but remained similar in Hospital C (Adj OR 1.19, 95% CI 0.60-2.33), after adjusting for age, gender, comorbidities, prior MRSA carriage, prior antibiotics exposure and length of hospital stay. Compared with the change in MRSA prevalence from 2015 to 2016 in Hospital C, MRSA prevalence declined substantially in Hospital A (Adj OR 0.35, 95% CI 0.13-0.97) and Hospital B (Adj OR 0.48, 95% CI 0.22-1.03). Topical intranasal octenidine, coupled with universal daily antiseptic bathing, can reduce MRSA colonisation in extended-care facilities.

ST22 and ST239 MRSA duopoly in Singaporean hospitals: 2006-2010.

Surveillance is integral for the monitoring and control of infectious diseases. We conducted prospective laboratory surveillance of methicillin-resistant Staphylococcus aureus (MRSA) in five Singaporean public-sector hospitals from 2006 to 2010, using WHONET 5.6 for data compilation and analysis. Molecular profiling using multilocus variable-number tandem-repeat analysis, staphylococcal cassette chromosome mec classification and multilocus sequence typing was performed for a random selection of isolates. Our results showed overall stable rates of infection and bacteraemia, although there was significant variance among the individual hospitals, with MRSA rates increasing in two smaller hospitals and showing a trend towards decreasing in the two largest hospitals. The proportion of blood isolates that are EMRSA-15 (ST22-IV) continued to increase over time, slowly replacing the multi-resistant ST239-III. A new MRSA clone - ST45-IV - is now responsible for a small subset of hospital infections locally. More effort is required in Singaporean hospitals in order to reduce the rates of MRSA infection significantly.