Air dispersal of meticillin-resistant Staphylococcus aureus in residential care homes for the elderly: implications for transmission during the COVID-19 pandemic.

BACKGROUND: Meticillin-resistant Staphylococcus aureus (MRSA) infections are rampant in hospitals and residential care homes for the elderly (RCHEs). AIM: To analyse the prevalence of MRSA colonization among residents and staff, and degree of environmental contamination and air dispersal of MRSA in RCHEs. METHODS: Epidemiological and genetic analysis by whole-genome sequencing (WGS) in 12 RCHEs in Hong Kong. FINDINGS: During the COVID-19 pandemic (from September to October 2021), 48.7% (380/781) of RCHE residents were found to harbour MRSA at any body site, and 8.5% (8/213) of staff were nasal MRSA carriers. Among 239 environmental samples, MRSA was found in 39.0% (16/41) of randomly selected resident rooms and 31.3% (62/198) of common areas. The common areas accessible by residents had significantly higher MRSA contamination rates than those that were not accessible by residents (37.2%, 46/121 vs. 22.1%, 17/177, P=0.028). Of 124 air samples, nine (7.3%) were MRSA-positive from four RCHEs. Air dispersal of MRSA was significantly associated with operating indoor fans in RCHEs (100%, 4/4 vs. 0%, 0/8, P=0.002). WGS of MRSA isolates collected from residents, staff and environmental and air samples showed that ST 1047 (CC1) lineage 1 constituted 43.1% (66/153) of all MRSA isolates. A distinctive predominant genetic lineage of MRSA in each RCHE was observed, suggestive of intra-RCHE transmission rather than clonal acquisition from the catchment hospital. CONCLUSION: MRSA control in RCHEs is no less important than in hospitals. Air dispersal of MRSA may be an important mechanism of dissemination in RCHEs with operating indoor fans.

Evaluation of replacing the existing diagnostic strategy for Neisseria gonorrhoeae and Chlamydia trachomatis infections with sole molecular testing of urine specimens in a sexually transmitted infection clinic setting.

OBJECTIVES: To evaluate nucleic acid testing of urine specimens against conventional Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) tests in genital swab specimens in a sexually transmitted infection (STI) clinic setting. METHODS: Genital swab and urine samples were collected from attendees of public STI clinics in Hong Kong from May to June 2007. Swab specimens were subjected to on-site Gram stained microscopy and inoculation onto modified Thayer-Martin medium for NG culture before laboratory processing. CT PCR on genital swabs was performed by the Roche Cobas Amplicor test. Urine samples were tested for CT and NG by the Aptima Combo 2 (AC2) assay. RESULTS: Data from 414 patients were analysed. The sensitivity and specificity of AC2 for NG were 100% (35/35) and 98.4% (373/379), respectively, with culture of genital swab specimens as standard. On-site microscopy provided timely results for empirical antimicrobial therapy, whereas culture yielded bacterial isolates for susceptibility testing and typing studies. Regarding CT, using Amplicor on genital swab specimens as reference, the sensitivity and specificity of AC2 were 98.7% (78/79) and 97.5% (313/321), respectively. Amplicor yielded uninterpretable results in 14 specimens due to PCR inhibitors. CONCLUSIONS: The current STI clinic and laboratory practices were practical and useful for clinical management, even though favourable results were obtained with the AC2 assay, which had streamlined laboratory workflow. The use of a molecular testing strategy may be cost-effective with microscopy and culture being targetted for patient groups with the highest expected yield of positive results.