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.

Transmission dynamics and associated mortality of nosocomial COVID-19 throughout 2021: a retrospective study at a large teaching hospital in London.

BACKGROUND: The impact of nosocomial SARS-CoV-2 infections has changed significantly since 2020. However, there is a lack of up-to-date evidence of the epidemiology of these infections which is essential in order to appropriately guide infection control policy. AIMS: To identify the secondary attack rate of SARS-CoV-2 infection and associated mortality across different variants of concern. METHODS: A single-centre retrospective study of all nosocomial SARS-CoV-2 exposure events was conducted between 31st December 2020 and 31st December 2021. A secondary attack rate was calculated for nosocomial acquisition of SARS-CoV-2 infection and time to positivity. Positive contacts were assessed for all-cause 30-day mortality. RESULTS: A total of 346 sequential index exposure events were examined, and 1378 susceptible contacts identified. Two hundred susceptible contacts developed SARS-CoV-2 infection (secondary attack rate of 15.5%). The majority of index cases (59%) did not result in any secondary SARS-CoV-2 infection. Where close contacts developed SARS-CoV-2 infection, 80% were detected within the first five days since last contact with the index case. The overall associated mortality among positive contacts across 2021 was 9%, with an estimated reduction of 68% when comparing periods of high Omicron versus Alpha transmission. CONCLUSION: Our findings describe that most SARS-CoV-2 infections are detected within five days of contact with an index case; we have also demonstrated a considerably lower mortality rate with the Omicron variant in comparison to previous variants. These findings have important implications for informing and supporting infection control protocols to allow movement through the hospital, and ensure patients access care safely.

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.

Prevalence and clinical correlations of genetic subtypes of Giardia lamblia in an urban setting.

The clinical significance of different genetic subtypes or assemblages of Giardia lamblia is uncertain. Cases of giardiasis in south-west London between 1999 and 2005 were studied, comparing molecular-typing results with clinical and epidemiological findings from routine surveillance. We identified 819 cases, of whom 389 returned surveillance questionnaires. A subset of 267 faecal samples was submitted for typing by sequencing of the triose phosphate isomerase (tpi) and ribosomal RNA genes, and/or a separate duplex PCR of the tpi gene. Typing was successful in 199 (75%) samples by at least one of the molecular methods. Assemblage A accounted for 48 (24%) samples and Assemblage B for 145 (73%); six (3%) were mixed. Both assemblages had similar seasonality, age distribution and association with travel. Clinical features were available for 59 successfully typed cases: both assemblages caused similar illness, but Assemblage A was significantly more frequently associated with fever than Assemblage B.

Telephoning of interim blood culture results: a regional survey.

AIMS: Most staphylococci grown from blood cultures are contaminants. Since they are microscopically indistinguishable from non-contaminants, considerable time and resources may be spent following up all patients with positive blood cultures before the identification is made the following day. Since there is no formal guidance or standard available in this area, this report surveyed practice in our region. METHODS: An interview was conducted by telephone, using a standardised questionnaire. Results were analysed using descriptive techniques. RESULTS: The majority of microbiologists did not communicate all presumptive staphylococci but waited for identification in some cases. CONCLUSION: There is a range of practice in laboratories due to conflicting pressures: limited time, fear of criticism if results are not phoned, fear of causing confusion with provisional information and lack of clarity concerning what is "good practice." This survey concludes that a decision not to telephone every presumptive Staphylococcus in blood cultures on Day 1 is reasonable.

An outbreak of wound infection in cardiac surgery patients caused by Enterobacter cloacae arising from cardioplegia ice.

This paper describes an outbreak of postoperative sternal wound infections. A cardiac surgeon noted a cluster of serious infections leading to wound dehiscence, despite the fact that none of his colleagues had noticed a rise in infection rates. The infections were predominantly with Enterobacter cloacae, and molecular typing and serotyping showed these isolates to be indistinguishable. Observation of the surgeon's practice revealed nothing untoward, and there were no infections among his patients operated on in another hospital. There appeared to be no significant difference between the modes of operation of the different surgeons. The operating theatres were screened to exclude an environmental source, with samples cultured on CHROMagar Orientation, a selective/differential medium designed for urine samples. Further questioning revealed one difference between the practices of the different surgeons; this surgeon used semi-frozen Hartmann's solution to achieve cardioplegia. The freezer used for this was swabbed and yielded E. cloacae, indistinguishable from the clinical isolates. It is hypothesized that this organism contaminated the freezer, and that the contamination was passed on to the ice/slush solution, thus infecting the patients. There have been no more cases since the freezer was replaced, a rigorous cleaning schedule instituted, and steps taken to reduce the possibility of any further contamination.

Molecular technique identifies the pathogen responsible for culture negative infective endocarditis.

A case of culture negative endocarditis complicated by immune complex glomerulonephritis and severe aortic regurgitation necessitated aortic valve replacement. Empirical treatment with penicillin and gentamicin according to UK guidelines was started. The pathogen, Streptococcus sanguis, was later identified by polymerase chain reaction amplification and sequencing of bacterial 16S ribosomal RNA. This molecular technique is likely to be of increasing importance in determining the aetiology of culture negative infective endocarditis, thus providing essential treatment and epidemiological information.

Treatment of infections due to resistant organisms.

Antibiotic resistance remains rare in paediatric community-acquired pneumonia in the UK, but is more common in hospital-acquired pneumonia and in patients with chronic lung diseases. It should also be considered in children arriving from countries with a high prevalence of antibiotic resistance, children with previous heavy antibiotic exposure, those who are immunosuppressed, and those who are not responding to conventional therapy. The most frequent bacterial cause of paediatric pneumonia is Streptococcus pneumoniae and globally there are major concerns about the increasing resistance of this organism to penicillin. Intermediate resistance may be overcome with conventional doses of parenteral penicillin and there is as yet no convincing evidence that intermediate/high level resistance is associated with a worse clinical outcome. Continued vigilance and research is required. The recently introduced pneumococcal conjugate vaccines offer great promise as they are likely to prevent cases of disease due to penicillin-resistant serotypes.

Documentation of positive blood culture results in a London teaching hospital.

OBJECTIVES: Our current practice is that initial (day 1) positive blood culture results are communicated to clinical teams; the task of recording those results in the notes is left to the clinical team. Microbiological information may be of crucial importance to an on-call doctor asked to review an unwell patient. We therefore sought to establish the extent to which day 1 positive blood culture information is available in patients' notes and its accuracy. METHODS: There were 51 positive blood cultures over a 14-day period. Patient notes of 39 of these were available for examination for evidence of the day 1 culture report, the accuracy of that report and evidence of clinical interpretation. RESULTS: The proportion of notes with a record was disappointingly low (54%), although the record was almost always accurate. Results reported at the weekend were as likely to be recorded in the notes as those given during the week. CONCLUSION: On-call doctors, not previously acquainted with a patient, will find that important information about day 1 positive blood culture results is not available to them in patient notes in around half of all cases. This adds weight to the view that medical microbiologists should give greater priority to ward visits and documentation of significant results, thus ensuring continuity of care from the laboratory bench to the bedside.

Azelaic acid: potential as a general antitumoural agent.

Azelaic acid is a naturally occurring straight-chained 9-carbon atom dicarboxylic acid which is non-toxic, non-teratogenic, and non-mutagenic. Its antiproliferative and cytotoxic effect on a variety of tumoural cell lines in culture, due to inhibition of mitochondrial oxidoreductases of the respiratory chain and of enzymes concerned with DNA synthesis is well established; normal cells are unaffected at similar dosages and times of exposure. Human melanoma cells xenotransplanted onto athymic nude mice are significantly affected by administration of azelaic acid. Clinically, in humans, it has already been shown to cause regression of melanoma in situ and primary invasive malignant melanoma. These results rank azelaic acid as a potential general antitumoural agent. It can be administered topically, focally, orally, intravenously, intra-arterially, and intralymphatically, all without local or general ill-effects, and is metabolized without harmful side-products. Simultaneous administration by different routes can ensure delivery of high concentrations at lesional sites and for sustained periods. Courses can be repeated. In addition to melanoma, cutaneous and bronchial squamous cell carcinoma, bladder and breast cancers, and leukaemia would seem to be ideal candidates for further clinical investigation and trial of the anti-cancer potential of azelaic acid, as prime, adjuvant, and palliative therapy, and for disseminated disease.

An outbreak of multi-drug-resistant tuberculosis in a London teaching hospital.

We describe the epidemiology and control of a hospital outbreak of multi-drug-resistant tuberculosis (MDR-TB). A human immunodeficiency virus (HIV)-negative patient with drug-sensitive tuberculosis developed MDR-TB during a period of unsupervised therapy. She was admitted to an isolation room in a ward with HIV-positive patients, but the room, unbeknown to hospital staff, was at positive-pressure relative to the main ward. Seven HIV-positive contacts developed MDR-TB. The diagnosis in the second patient was delayed, partly because acid-fast bacilli in his sputum were assumed to be Mycobacterium avium-intracellulare. All the available Mycobacterium tuberculosis isolates were indistinguishable by molecular typing. Nearly 1400 staff and patient contacts were offered screening, but the screening programme detected only one of the cases. Despite therapy, the index patient and two of the contacts died. HIV-positive patients are more likely than others to develop tuberculosis after exposure, and the disease may progress more rapidly. In these patients the possibility that acid-fast bacilli may represent M. tuberculosis must always be considered. Patients with tuberculosis (suspected or proven) should not be nursed in the same wards as immunosuppressed patients, and should be isolated. MDR-TB cases must be isolated in negative-pressure rooms. Hospital side-rooms may be positive-pressure as a fire safety measure; infection control teams must be aware of the airflows in all isolation rooms, and must be consulted during the design of hospital buildings. Good communication between infection control teams and clinicians is important, and all medical and nursing staff must be aware of the principles of management of patients with proven or suspected tuberculosis and MDR-TB.

Approaches to the diagnosis and prevention of intravascular catheter-related infection.

Intravascular catheter-related infections remain a significant cause of morbidity and mortality despite clear guidelines on insertion and care, which should aid in their prevention. New approaches in the diagnosis of these infections, which do not require removal of the catheter, and novel technologies, including the application of antimicrobial agents to the catheter, have demonstrated some degree of success in prevention.

Culture-negative endocarditis: contribution of bartonella infections.

Two cases of bartonella endocarditis are described: one in a 55 year old homeless alcoholic man, caused by Bartonella quintana; the other in a 41 year old male with a history of exposure to cat fleas, caused by B henselae. Serological testing and polymerase chain reaction of the excised valves were used to identify the organisms. False positive serology for chlamydia was detected in one case.

Streptococcus pyogenes bacteraemia: a 27-year study in a London teaching hospital.

The clinical and epidemiological features of 120 episodes of Streptococcus pyogenes bacteraemia in St. Thomas' Hospital between 1970 and 1997 were analysed. One-third of episodes were nosocomial. M1 was the most common serotype, and 29% of strains were non-typable. There was a variety of presenting features, but nearly half of the patients had cellulitis, 15% were shocked, and 6% had necrotic infections. There was no focus of infection in 13%. 54% of patients had an underlying disease, and 23% of infections were associated with a medical procedure or device. The mortality rate was 19%, and was associated with shock, coma, no focus of infection, and underlying disease. Since 1989, the annual incidence has more than doubled, and M1 strains and necrotic infections have increased, but the mortality rate and the proportion of patients presenting with shock have decreased, and the increase in cases involved many different M-types.