Hospital MRSA outbreaks: Multiplex PCR-reverse line blot binary typing as a screening method for WGS, and the role of the environment in transmission

Meticillin-resistant Staphylococcus aureus transmission among healthcare workers, patients and the environment in a large acute hospital under non-outbreak conditions investigated using whole-genome sequencing

BACKGROUND

The role of meticillin-resistant Staphylococcus aureus (MRSA) colonization of healthcare workers (HCWs), patients and the hospital environment in MRSA transmission in non-outbreak settings is poorly understood.

AIMS

To investigate transmission events (TEs) involving HCWs, patients and the environment under non-outbreak conditions in a hospital with a history of endemic MRSA using whole-genome sequencing (WGS).

METHODS

HCW (N = 326) and patient (N = 388) volunteers on nine wards were tested for nasal and oral MRSA colonization over two years. Near-patient environment (N = 1164), high-frequency touch sites (N = 810) and air (N = 445) samples were screened for MRSA. Representative MRSA and clinical isolates were analysed by WGS and core-genome multi-locus sequence typing (cgMLST). Closely related isolates (≤24 allelic differences) were segregated into related isolated groups (RIGs).

FINDINGS

In total, 155 MRSA were recovered: clinical isolates (N = 41), HCWs (N = 22), patients (N = 37), environmental isolates (N = 55). Nine clonal complexes (CCs) were identified among 110/155 MRSA sequenced with 77/110 assigned to CC22. Seventy-nine MRSA segregated into 17 RIGs. Numerous potential TEs were associated with CC22-MRSA (RIGs 1-15), CC45-MRSA (RIG-16) and CC8-MRSA (RIG-17). RIG-1, (the largest RIG) contained 24 ST22-MRSA-IVh from six HCWs, six patients, four clinical and eight environmental samples recovered over 17 months involving 7/9 wards. TEs involving HCW-to-patient, HCW-to-HCW, patient-to-patient and environmental contamination by HCW/patient isolates were evident. HCW, patient, clinical and environmental isolates were identified in four, nine, seven and 13 RIGs, respectively, with 12/13 of these containing isolates closely related to HCW and/or patient isolates.

CONCLUSIONS

WGS detected numerous potential hospital MRSA TEs involving HCWs, patients and the environment under non-outbreak conditions.

Efficacy of aerosolized hydrogen peroxide (Deprox) cleaning compared to physical cleaning in a Burns Unit

BACKGROUND

The performance of Deprox aerosolized hydrogen peroxide (aHP) has not been extensively studied in real-world clinical settings. A comparative study of aHP terminal disinfection was conducted in a Burns Unit and its performance compared to physical cleaning alone.

METHODS

Environmental surfaces were sampled pre-cleaning, post-cleaning and post-aHP disinfection. Samples were cultured for MRSA, VRE, Gram-negative multi-resistant organisms and other Gram-negative bacilli.

RESULTS

310 sites were sampled. There was a reduction in the rates of contaminated surfaces post-aHP, though pathogens were still recoverable in most cases, except for VRE. There was a marked reduction in MRSA contamination of soft surfaces (12% post-clean vs 6% post-aHP), and patient room surfaces (8.3% post-clean vs 2.8% post-aHP). It does not work as well for MRSA in bathrooms: 7% of surfaces were positive post-clean, and 9% post-aHP. There was a reduction in multiresistant Gram-negative bacteria (7%-3%), mostly due to drains (33%-13%).

CONCLUSION

aHP is a useful method of environmental disinfection, especially for Gram-negative pathogens in drains and MRSA on hard and soft surfaces. Where ongoing acquisition of MRSA is a problem, an adjunctive method of terminal disinfection in bathrooms could be considered.