An outbreak of meticillin-resistant Staphylococcus aureus colonization in a neonatal intensive care unit: use of a case-control study to investigate and control it and lessons learnt.

AIM: To describe the investigation and management of a meticillin-resistant Staphylococcus aureus (MRSA) outbreak on a neonatal intensive care unit (NICU) and the lessons learnt. METHODS: This was an outbreak report and case-control study conducted in a 40-cot NICU in a tertiary referral hospital and included all infants colonized/infected with gentamicin-resistant MRSA. INTERVENTION: Standard infection-control measures including segregation of infants, barrier precautions, enhanced cleaning, assessment of staff practice including hand hygiene, and increased MRSA screening of infants were implemented. Continued MRSA acquisitions led to screening of all NICU staff. A case-control study was performed to assess staff contact with colonized babies and inform the management of the outbreak. FINDINGS: Eight infants were colonized with MRSA (spa type t2068), one of whom subsequently developed an MRSA bacteraemia. MRSA colonization was significantly associated with lower gestational age; lower birthweight and with being a twin. Three nurses were MRSA colonized but only one nurse (45) was colonized with MRSA spa type t2068. Multivariable logistic regression analysis identified being cared for by nurse 45 as an independent risk factor for MRSA colonization. CONCLUSIONS: Lack of accurate recording of which nurses looked after which infants (and when) made identification of the risk posed by being cared for by particular nurses difficult. If this had been clearer, it may have enabled earlier identification of the colonized nurse, avoiding subsequent cases. This study highlights the benefit of using a case-control study, which showed that most nurses had no association with colonized infants.

Whole-genome sequencing in the investigation of recurrent invasive group A streptococcus outbreaks in a maternity unit.

BACKGROUND: The clinical manifestations of group A streptococcus (GAS) (Streptococcus pyogenes) are diverse, ranging from asymptomatic colonization to devastating invasive disease. Maternity-related clusters of invasive GAS (iGAS) infection are complex to investigate and control, especially if recurrent. AIM: To investigate three episodes of emm 75 GAS/iGAS infection in maternity patients at one hospital site over a four-year period (two with monophyletic ancestry). METHODS: The episodes are described, together with whole-genome sequence (WGS) isolate analyses. Single nucleotide polymorphism differences were compared with contemporaneous emm 75 genomes. FINDINGS: Over the four-year study period, seven mothers had emm 75 GAS/iGAS and one mother had emm 3 iGAS (in year 4) (subsequently discounted as linked). Three (clinical/screening samples) of the seven babies of emm-75-positive mothers and three screened healthcare workers were positive for emm 75 GAS. WGS similarity suggested a shared ancestral lineage and a common source transmission, but directionality of transmission cannot be inferred. However, the findings indicate that persistence of a particular clone in a given setting may be long term. CONCLUSIONS: Occupational health procedures were enhanced, staff were screened, and antibiotic therapy was provided to GAS-positive staff and patients. The definitive source of infection could not be identified, although staff-patient transmission was the most likely route. The pattern of clonal GAS transmission over the four-year study period suggests that long-term persistence of GAS may have occurred.

Use of linked electronic health records to assess mortality and length of stay associated with pandemic influenza A(H1N1)pdm09 at a UK teaching hospital.

Effective use of data linkage is becoming an increasingly important focus in the new healthcare system in England. We linked data from the results of a multiplex PCR assay for respiratory viruses for a population of 230 inpatients at a UK teaching hospital with their patient administrative system records in order to compare the mortality and length of stay of patients who tested positive for influenza A(H1N1)pdm09 with those positive for another influenza A virus. The results indicated a reduced risk of death among influenza A(H1N1)pdm09 patients compared to other influenza A strains, with an adjusted risk ratio of 0·25 (95% confidence interval 0·08-0·75, P = 0·01), while no significant differences were found between the lengths of stay in the hospital for these two groups. Further development of such methods to link hospital data in a routine fashion could provide a rapid means of gaining epidemiological insights into emerging infectious diseases.

Service evaluation of selected risk factors for extended-spectrum beta-lactamase Escherichia coli urinary tract infections: a case-control study.

In the context of the increasing incidence of extended-spectrum beta-lactamase (ESBL) Escherichia coli infection, this prospective frequency-matched case-control study aimed to identify risk factors that would provide information and guidance for local clinical practice. One hundred and twelve participants were recruited: 54 cases and 58 controls. Univariate analysis indicated that isolation of an ESBL-producing E. coli in the previous 12 months and diabetes were significantly associated with the outcome. This study demonstrates the utility of service evaluation studies for producing epidemiological information to inform clinical practice.

Campylobacteriosis outbreak associated with consumption of undercooked chicken liver pâté in the East of England, September 2011: identification of a dose-response risk.

A foodborne outbreak with 49 cases (22 culture positive for Campylobacter sp.) following a wedding party in the East of England was investigated. A retrospective cohort study identified an association between consumption of chicken liver pâté and infection with Campylobacter jejuni/coli. There was a statistically significant association between dose (amount of chicken liver pâté eaten) and the risk of disease ['tasted': odds ratio (OR) 1·5, 95% confidence interval (CI) 0·04-∞; 'partly eaten': OR 8·4, 95% CI 1·4-87·5; 'most or all eaten': OR 36·1, 95% CI 3·3-2119). The local authority found evidence that the preparation of chicken livers breached Food Standards Agency's guidelines. This epidemiological investigation established a clear dose-response relationship between consumption of chicken liver pâté and the risk of infection with Campylobacter. The continuing need to raise public awareness of the risk to human health posed by undercooked chicken liver is evident.

Risk exposures for human ornithosis in a poultry processing plant modified by use of personal protective equipment: an analytical outbreak study.

Ornithosis outbreaks in poultry processing plants are well-described, but evidence for preventive measures is currently lacking. This study describes a case-control study into an outbreak of ornithosis at a poultry processing plant in the East of England, identified following three employees being admitted to hospital. Workers at the affected plant were recruited via their employer, with exposures assessed using a self-completed questionnaire. Cases were ascertained using serological methods or direct antigen detection in sputum. 63/225 (28%) staff participated, with 10% of participants showing evidence of recent infection. Exposure to the killing/defeathering and automated evisceration areas, and contact with viscera or blood were the main risk factors for infection. Personal protective equipment (goggles and FFP3 masks) reduced the effect of exposure to risk areas and to self-contamination with potentially infectious material. Our study provides some evidence of effectiveness for respiratory protective equipment in poultry processing plants where there is a known and current risk of ornithosis. Further studies are required to confirm this tentative finding, but in the meantime respiratory protective equipment is recommended as a precautionary measure in plants where outbreaks of ornithosis occur.

Large outbreak of verocytotoxin-producing Escherichia coli O157 infection in visitors to a petting farm in South East England, 2009.

In the summer of 2009, an outbreak of verocytotoxigenic Escherichia coli O157 (VTEC O157) was identified in visitors to a large petting farm in South East England. The peak attack rate was 6/1000 visitors, and highest in those aged <2 years (16/1000). We conducted a case-control study with associated microbiological investigations, on human, animal and environmental samples. We identified 93 cases; 65 primary, 13 secondary and 15 asymptomatic. Cases were more likely to have visited a specific barn, stayed for prolonged periods and be infrequent farm visitors. The causative organism was identified as VTEC O157 PT21/28 with the same VNTR profile as that isolated in faecal specimens from farm animals and the physical environment, mostly in the same barn. Contact with farm livestock, especially ruminants, should be urgently reviewed at the earliest suspicion of a farm-related VTEC O157 outbreak and appropriate risk management procedures implemented without delay.

Programme to vaccinate poultry workers against seasonal influenza: options for delivery in the East of England.

Avian influenza A (H5N1) has spread to the UK causing outbreaks in commercial poultry. Vaccination of poultry workers with seasonal influenza has been advised to prevent a viral mutation that could facilitate human-to-human transmission, causing a new pandemic strain. This project aimed to determine delivery options and costs of a vaccination programme targeted at poultry workers. Data from the Great Britain Poultry Register were used to understand the distribution of the target population. A stakeholders group in the East of England (EoE) discussed delivery options. An options appraisal is used to prioritize these options. There are over 10,000 poultry workers distributed throughout the EoE. Five delivery options were considered (industry's occupational health services, via general practitioners as a Directed or Locally Enhanced Services, via other community healthcare providers and a commercial provider). Delivery is likely to cost between £35,414 and £182,899 (or £10.18-£48.93 per person vaccinated) in the EoE, depending on delivery mechanism, target threshold and level of uptake. Delivering through a commercial provider was the preferred option. Whichever way the programme is delivered it should be cost-neutral to the Primary Care Trust (PCT). Otherwise PCTs may see themselves having to prioritize between vaccinating poultry workers against other pressing programmes.

Monitoring tuberculosis treatment outcome: analysis of national surveillance data from a clinical perspective.

BACKGROUND: In 1998, the World Health Organization (WHO) and the International Union Against Tuberculosis and Lung Disease (IUATLD) published recommendations standardising the evaluation of tuberculosis treatment outcome in Europe. These guidelines fail to account for clinically appropriate alterations in the management of patients. OBJECTIVES: To evaluate tuberculosis treatment outcome in England, Wales and Northern Ireland by redefining the outcome criteria and investigate factors associated with unsuccessful treatment outcome 12 months after notification. METHODS: This was a prospective analysis of a cohort of patients diagnosed in England, Wales and Northern Ireland and reported to the Enhanced Tuberculosis Surveillance system in 2001 and 2002. Proportions of success and failure were calculated based on a new set of criteria following discussion with clinicians treating tuberculosis cases. Logistic regression was used to study risk factors for unsuccessful treatment outcome. RESULTS: 13 048 cases were notified in the study period. Of the 2676 that were identified as new sputum smear positive pulmonary cases, 2209 (82.5%) had treatment outcome data reported. Using the WHO/IUATLD criteria, 76.8% were classified as successful. In contrast, applying the new criteria, the success rate was 87.5%. This rate exceeds the 85% success target set by the WHO. Risk factors for unsuccessful treatment outcome included male sex (OR 1.27; 95% CI 1.08 to 1.49), being elderly (p trend < 0.001), having pulmonary tuberculosis (OR 1.28; 95% CI 1.08 to 1.53) and having resistance to any antituberculosis drug (OR 1.90; 95% CI 1.44 to 2.52). CONCLUSION: The proportion of tuberculosis cases with a successful treatment outcome exceeded the target of 85% success rate based on the modified outcome categories. Although the tuberculosis treatment outcome criteria set by WHO/IUATLD appear to be clear, they mix measures of process and outcome. Further refinement may be necessary in low incidence high income countries, especially those with a high mortality among the elderly.

Exposures and reported symptoms associated with occupational deployment to the Buncefield fuel depot fire, England 2005.

OBJECTIVES: An explosion at the Buncefield fuel depot outside London occurred on 11 December 2005. We conducted a retrospective cohort study of airborne exposures and health status for workers deployed. METHODS: Deployed individuals were identified through their occupational health departments. We sent a self-completion questionnaire asking about health symptoms during the burn and post-burn phases. The prevalence of health symptoms in workers was compared to symptoms in local residents not under the smoke plume. RESULTS: Of 1949 eligible individuals, 815 returned questionnaires (response rate 44%). Respiratory protection was used by 39%. Symptoms were reported by 41% of individuals during the burn phase compared with 26% in the post-burn phase. In a final multivariable model, reporting of any symptoms was associated with deployment inside the inner fire cordon during the burn phase (OR 2.07, 95% CI 1.24 to 3.47) and wearing a face mask (OR 2.33, 95% CI 1.67 to 3.26). Compared with the general public, eye irritation (prevalence ratio (PR) 2.1, 95% CI 1.5 to 3.0), coughing (PR 1.3, 95% CI 1.0 to 1.8) and headaches (PR 1.7, 95% CI 1.2 to 2.5) were more common in workers deployed during the burn phase but not the post-burn phase. CONCLUSIONS: Increased reporting of symptoms close to the fire during the burn phase was consistent with increased exposure to products of combustion, although no major acute illness was reported. That only a minority of individuals used face masks, which were not protective for symptoms, raises questions about the availability of adequate respiratory protection for such incidents.

Outbreaks of waterborne infectious intestinal disease in England and Wales, 1992-2003.

We reviewed the epidemiological and microbiological characteristics of 89 reported outbreaks of waterborne infectious intestinal disease affecting 4321 people in England and Wales over the period 1992-2003. Public water supplies were implicated in 24 outbreaks (27%), private water supplies in 25 (28%), swimming pools in 35 (39%) and other sources in five outbreaks (6%). Cryptosporidium was implicated in 69% of outbreaks, Campylobacter sp. in 14%, Giardia in 2%, E. coli O157 in 3% and Astrovirus in 1%. From 2000, there was a consistent decline in the number of outbreaks of waterborne disease associated with public water supplies. The incidence rate of outbreaks in recipients of private water supplies may be as high as 35 times the rate in those receiving public water supplies (1830 vs. 53 per million population). Private water suppliers need to be aware of the importance of adequate treatment and the prevention of faecal contamination of storage water. Swimming-pool operators need to ensure chlorination and in particular adequate filtration measures are in place.

Legionnaires' disease: when an 'outbreak' is not an outbreak.

During August 2006, there was a large increase in non-travel related legionella cases throughout England and in the Netherlands.

Institutional risk factors for outbreaks of nosocomial gastroenteritis: survival analysis of a cohort of hospital units in South-west England, 2002-2003.

Nosocomial outbreaks of gastroenteritis are a major burden on hospital inpatient services, costing an estimated pound115 million annually to the English National Health Service. We actively followed-up 171 inpatient units from four major acute hospitals and 11 community hospitals in South-west England for one year. Outbreaks of gastroenteritis were ascertained through an active surveillance network using standard clinical definitions. Survival analysis Cox regression models using an outbreak of gastroenteritis as the endpoint were fitted to identify institutional and operational attributes related to increased outbreak rates at the level of the care unit. Greater number of beds in unit [hazard ratio (HR) 1.22 (per 10 additional beds), 95% confidence intervals (CI) 0.96-1.55] was associated with increased hazard, as were geriatric (HR 2.6, 95%CI 1.6-4.3) and general medical (HR 1.7, 95%CI 1.1-2.6) care units. The average length of stay on a unit was inversely associated with outbreak incidence [HR=0.89 (per additional week of stay), 95%CI 0.80-0.99]. Larger care units and those with higher throughput have increased rates of gastroenteritis outbreaks. These results should guide infection control policy and support the design of hospitals with smaller care units.

Health impacts of flooding in Lewes: a comparison of reported gastrointestinal and other illness and mental health in flooded and non-flooded households.

Severe flooding may become more frequent due to global warming. A historical cohort study was conducted by telephone interview for new episodes of illness in all age groups, and for psychological distress in adults, following severe river flooding on 12 October 2000 in the town of Lewes in Southern England. Two hundred and twenty-seven residents of 103 flooded households and 240 residents of 104 non-flooded households in the same postal district were recruited by random selection of addresses from a post flooding survey and a commercial database respectively. Having been flooded was associated with earache (RR 2.2 [1.1,4.1] p = 0.02), and a significant increase in risk of gastroenteritis with depth of flooding (RR 1.7 [0.9,3.0] p = 0.09, p for trend by flood depth = 0.04). Adults had a four-times higher risk of psychological distress defined as a score of > or = 4 in response to the 12-item General Health Questionnaire (GHQ-12) (RR 4.1 [2.6, 6.4] p < 0.0005, p for trend by flood depth = 0.01). Associations between flooding and new episodes of physical illness in adults diminished after adjustment for psychological distress. Flooding remained highly significantly associated with psychological distress after adjustment for physical illnesses. Psychological distress may explain some of the excess physical illness reported by flooded adults and possibly by children as well. Policies to promote population resilience to flooding where flood prevention has failed must include practical support for flood victims and provision of appropriate psychological support. Associations with physical illnesses affirm the need for advice and assistance with individual, household and environmental hygiene and access to medical services.

Outbreaks of infectious disease associated with private drinking water supplies in England and Wales 1970-2000.

In England and Wales over the last 30 years there have been 25 reported outbreaks of infection, associated with private water supplies (PWS). The majority (16 outbreaks) were reported after the introduction of enhanced surveillance. Although PWS only serve 0.5% of the population, 36% of drinking water outbreaks are associated with PWS. The main pathogen, campylobacter, was implicated in 13 (52%) outbreaks. Most reported outbreaks (88%) occurred in commercial or Category Two supplies, which potentially affect larger populations. The main factors implicated in these outbreaks are temporary or transient populations, treatment (lack or failure), the presence of animals and heavy rains. The public health problem associated with PWS could be prevented by the identification and understanding of risk factors, by the proper protection of water sources and adequate treatment and maintenance. This could be facilitated through the introduction of a risk assessment as part of a scheme for PWS.

A national outbreak of multi-resistant Salmonella enterica serovar Typhimurium definitive phage type (DT) 104 associated with consumption of lettuce.

Between 1 August and 15 September 2000, 361 cases of Salmonella enterica serotype Typhimurium definitive phage type (DT) 104, resistant to ampicillin, chloramphenicol, streptomycin, sulphonamides, spectinomycin and tetracycline (R-type ACSSuSpT), were identified in England and Wales residents. Molecular typing of 258 isolates of S. Typhimurium DT104 R-type ACSSuSpT showed that, although isolates were indistinguishable by pulsed-field gel electrophoresis, 67% (174/258) were characterized by a particular plasmid profile. A statistically significant association between illness and consumption of lettuce away from home was demonstrated (OR = 7.28; 95% CI=2.25-23.57; P=0.0006) in an unmatched case-control study. Environmental investigations revealed that a number of food outlets implicated in the outbreak had common suppliers of salad vegetables. No implicated foods were available for microbiological testing. An environmental audit of three farms that might have supplied salad vegetables to the implicated outlets did not reveal any unsafe agricultural practices. The complexity of the food supply chain and the lack of identifying markers on salad stuffs made tracking salad vegetables back to their origin extremely difficult in most instances. This has implications for public health since food hazard warnings and product withdrawal are contingent on accurate identification of the suspect product.

Enhancing surveillance of cryptosporidiosis: test all faecal specimens from children.

The heightened risk of waterborne cryptosporidiosis, associated with heavy rainfall in autumn 2000, prompted us to survey laboratory practice in the South East Region of England in testing faecal specimens for Cryptosporidium spp. oocysts and reporting to the Public Health Laboratory Service Communicable Disease Surveillance Centre (PHLS CDSC). Varied practices were found. Ideally, all faecal specimens should be tested, but where laboratories are unable to do so, screening all faecal specimens from children age 15 years or younger would improve surveillance and could probably be accomplished with minimal additional resources.

Causes of morbilliform rash in a highly immunised English population.

AIMS: To determine the causes of morbilliform rash and fever in a population with high vaccination coverage for measles and rubella. METHODS: Comprehensive laboratory investigation additional to routine oral fluid testing of children presenting to primary care physicians in East Anglia, England. RESULTS: Laboratory confirmation of infection was obtained in 93 (48%) of 195 children: parvovirus B19 in 34 (17%); group A streptococcus in 30 (15%); human herpesvirus type 6 in 11 (6%); enterovirus in nine (5%); adenovirus in seven (4%); and group C streptococcus in six (3%) (four individuals tested positive for two agents). None had measles or rubella. CONCLUSIONS: Oral fluid testing to cover infections additional to measles and rubella aids clinical management and is likely to maintain uptake of testing, which is essential for measles and rubella surveillance in highly immunised low incidence populations.

Laboratory capability in Europe for foodborne viruses.

This report describes a survey of national laboratory capabilities of diagnostics and surveillance databases for foodborne viruses among the "Foodborne Viruses in Europe" consortium. All the countries have laboratories that can test for HAV antibody in human serum. Eight of the ten surveyed European countries maintain a national database of HAV cases. Food can be tested for the presence of HAV in Finland, Italy, Spain, France and Denmark. All surveyed countries have at least one laboratory that tests for Norwalk-like virus (NLV) by reverse transcriptase-polymerase chain reaction and all also have the capability to use electron microscopy. Five countries maintain a national database of NLV cases and nine maintain a national database of NLV outbreaks. Almost all participant countries have laboratories that can test for NLV in food items including shellfish.