Impact of removing the healthcare mask mandate on hospital-acquired COVID-19 rates.

BACKGROUND: Mandatory mask-wearing policies were one of several measures employed to reduce hospital-acquired SARS-CoV-2 infection throughout the pandemic. Many nations have removed healthcare mask mandates, but there remains a risk of new SARS-CoV-2 variants or epidemics of other respiratory viruses. AIM: To demonstrate the impact of removing the healthcare mask mandate. METHODS: SARS-CoV-2 infections were analysed in a large teaching hospital for 40 weeks in 2022 using a controlled interrupted time-series design. The intervention was the removal of a staff/visitor surgical mask-wearing policy for the most wards at week 26 (intervention group) with a subset of specific wards retaining the mask policy (control group). The hospital-acquired SARS-CoV-2 infection rate was adjusted by the underlying community infection rate. FINDINGS: In the context of a surge in SARS-CoV-2 infection, removal of the mask mandate for staff/visitors was not associated with a statistically significant change in the rate of nosocomial SARS-CoV-2 infection in the intervention group (incidence rate ratio: 1.105; 95% confidence interval: 0.523-2.334; P = 0.79) and there was no post-intervention trend (1.013; 0.932-1.100; P = 0.76) to suggest a delayed effect. The control group also showed no immediate or delayed change in infection rate. CONCLUSION: No evidence was found that removal of a staff/visitor mask-wearing policy had a significant effect on the rate of hospital-acquired SARS-CoV-2 infection. This does not demonstrate that masks were ineffective through the pandemic, but provides some objective evidence to justify the removal of healthcare mask mandates once there was widespread immunity and reduced disease severity.

Genome sequencing and characterization of an extensively drug-resistant sequence type 111 serotype O12 hospital outbreak strain of Pseudomonas aeruginosa.

A series of extensively drug-resistant isolates of Pseudomonas aeruginosa from two outbreaks in UK hospitals were characterized by whole genome sequencing (WGS). Although these isolates were resistant to antibiotics other than colistin, we confirmed that they are still sensitive to disinfectants. The sequencing confirmed that isolates in the larger outbreak were serotype O12, and also revealed that they belonged to sequence type ST111, which is a major epidemic strain of P. aeruginosa throughout Europe. As this is the first reported sequence of an ST111 strain, the genome was examined in depth, focusing particularly on antibiotic resistance and potential virulence genes, and on the reported regions of genome plasticity. High degrees of sequence similarity were discovered between outbreak isolates collected from recently infected patients, isolates from sinks, an isolate from the sewer, and a historical isolate, suggesting that the ST111 strain has been endemic in the hospital for many years. The ability to translate easily from outbreak investigation to detailed genome biology by use of the same data demonstrates the flexibility of WGS application in a clinical setting.

Multidrug-resistant Pseudomonas aeruginosa outbreaks in two hospitals: association with contaminated hospital waste-water systems.

BACKGROUND: Multidrug-resistant Pseudomonas aeruginosa (MDR-P) expressing VIM-metallo-beta-lactamase is an emerging infection control problem. The source of many such infections is unclear, though there are reports of hospital outbreaks of P. aeruginosa related to environmental contamination, including tap water. AIM: We describe two outbreaks of MDR-P, sensitive only to colistin, in order to highlight the potential for hospital waste-water systems to harbour this organism. METHODS: The outbreaks were investigated by a combination of descriptive epidemiology, inspection and microbiological sampling of the environment, and molecular strain typing. FINDINGS: The outbreaks occurred in two English hospitals; each involved a distinct genotype of MDR-P. One outbreak was hospital-wide, involving 85 patients, and the other was limited to four cases in one specialized medical unit. Extensive environmental sampling in each outbreak yielded MDR-P only from the waste-water systems. Inspection of the environment and estates records revealed many factors that may have contributed to contamination of clinical areas, including faulty sink, shower and toilet design, clean items stored near sluices, and frequent blockages and leaks from waste pipes. Blockages were due to paper towels, patient wipes, or improper use of bedpan macerators. Control measures included replacing sinks and toilets with easier-to-clean models less prone to splashback, educating staff to reduce blockages and inappropriate storage, reviewing cleaning protocols, and reducing shower flow rates to reduce flooding. These measures were followed by significant reductions in cases. CONCLUSION: The outbreaks highlight the potential of hospital waste systems to act as a reservoir of MDR-P and other nosocomial pathogens.