Transferring inpatients between wards drives large nosocomial COVID-19 outbreaks, Wales, 2020-22: a matched case-control study using routine and enhanced surveillance data.

BACKGROUND: The role of the hospital environment in the spread of COVID-19 is unclear. AIM: To measure associations between ward characteristics and outbreak size to inform mitigations. METHODS: Wards with large (case wards) and small (control wards) outbreaks in three acute hospitals were compared. Cases were healthcare-associated COVID-19 inpatients (positive polymerase chain reaction test ≥8 days post admission). Case wards were adult medical/surgical wards with ≥10 cases within rolling 14-day periods, between April 1st, 2020 and April 30th, 2022. Control wards were equivalents with 2-9 cases. Demographic and laboratory data were extracted from routine surveillance systems. Continuous data were aggregated fortnightly and analysed as binary variables according to median values. Each case ward was compared with two control wards matched on outbreak start date (±14 days) to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs) using univariable and conditional multivariable logistic regression. FINDINGS: From 170 outbreaks (median: 5 cases; interquartile range: 2-9), 35 case wards were identified. Community admissions were lower in case wards vs control wards (5 vs 10 median admissions; P<0.01, respectively), whereas transfers between wards within the same hospital were higher (58 vs 29 median transfers; P<0.01, respectively). Wards with more transfers in the preceding fortnight were significantly more likely to experience a large outbreak (≥35 vs <35 transfers; adjusted OR: 9.08; 95% CI: 2.5-33). CONCLUSION: We recommend safely minimizing patient movements, such as by asking clinicians to record the rationale for transfer, to reduce the likelihood of disease transmission.

Association between post-craniotomy Propionibacterium acnes infection and dural implants: a case-control study.

BACKGROUND: In 2011, 15 deep-seated Propionibacterium acnes infections were identified in patients following craniotomies in a hospital in the UK. AIM: To describe the outbreak and report findings from the investigation undertaken in order to identify the source and risk factors and inform control measures. METHODS: Data were obtained from hospital clinical records and included patient and surgical variables. Cases were defined as patients with microbiologically confirmed deep or organ space surgical site infection (SSI) caused by P. acnes following craniotomy undertaken in 2011. Four controls per case were randomly selected from patients who had a craniotomy in 2011 but who did not develop any SSI. The relationship between infection and putative exposures was examined using multivariate regression techniques. Infection prevention procedures and the theatre environment were reviewed to assess compliance with existing standards. FINDINGS: Fifteen cases and 65 controls were recruited. Odds of infection were higher for those who had a dural implant inserted during their operation [adjusted odds ratio (aOR): 14.6; 95% confidence interval (CI): 0.95-∞] and for those who had alcohol/Betadine®/chlorhexidine mix as a disinfectant (aOR: 7.9; 95% CI: 0.8-∞). Environmental investigations suggested that theatre ventilation systems delivered air exchange rates below the recommended standard. CONCLUSION: There was a positive association between using dural implants and P. acnes infection. Infection may have been facilitated by inefficient use of skin disinfectant and environmental factors. Recommendations included ongoing surveillance, the use of chlorhexidine skin disinfectant, ensuring adequate air exchanges and appropriate use of doors in theatre to minimize air turbulence.