Carbapenemase-producing Enterobacteriaceae in hospital wastewater: a reservoir that may be unrelated to clinical isolates.

BACKGROUND: Carbapenemase-producing Enterobacteriaceae (CPE) are an emerging infection control problem in hospitals worldwide. Identifying carriers may help reduce potential spread and infections. AIM: To assess whether testing hospital wastewater for CPE can supplement patient-based screening for infection prevention purposes in a hospital without a recognized endemic CPE problem. METHODS: Wastewater collected from hospital pipework on 16 occasions during February to March 2014 was screened for CPE using chromID(®) CARBA agar and chromID(®) CPS agar with a 10µg ertapenem disc and combination disc testing. Minimum inhibitory concentrations were determined using British Society for Antimicrobial Chemotherapy methodology and carbapenemase genes detected by polymerase chain reaction or whole-genome sequencing. Selected isolates were typed by pulsed-field gel electrophoresis. FINDINGS: Suspected CPE were recovered from all 16 wastewater samples. Of 17 isolates sent to the Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, six (four Citrobacter freundii and two Enterobacter cloacae complex) were New Delhi metallo-ß-lactamase (NDM) producers and the remaining 11 (six Klebsiella oxytoca and five Enterobacter cloacae complex) were Guiana-Extended-Spectrum-5 (GES-5) producers, the first to be described among Enterobacteriaceae in the UK. The four NDM-producing C. freundii, two NDM-producing E. cloacae complex, and four out of five GES-5-producing E. cloacae complex were each indistinguishable isolates of the same three strains, whereas the six GES-5-producing K. oxytoca overall shared 79% similarity. CONCLUSION: CPE are readily isolated from hospital wastewater using simple culture methods. There are either undetected carriers of CPE excreting into the wastewater, or these CPE represent colonization of the pipework from other sources. Surveillance of hospital wastewater for CPE does not appear helpful for infection control purposes within acute hospitals.

Giardiasis in North West England: faecal specimen requesting rates by GP practice.

Many cases of giardiasis in the UK are undiagnosed and among other things, diagnosis is dependent upon the readiness of GPs to request a specimen. The aim of this study is to assess the rate of specimens requested per GP practice in Central Lancashire, to examine the differences between GP practices and to estimate the pattern of unexplained spatial variation in the practice rate of specimens after adjustment for deprivation. To achieve this, we fitted a set of binomial and Poisson regression models, with random effects for GP practice. Our analysis suggests that there were differences in the rate of specimens by GP practices (P < 0·001) for a single year, but no difference in the proportion of positive tests per specimen submitted or in the rate of positive specimens per practice population. There was a difference in the cumulative rate of positive specimens per practice population over a 9-year period (P < 0·001). Neither the specimen rate per practice for a single year nor the cumulative rate of positive specimens over multiple years demonstrated significant spatial correlation. Hence, spatial variation in the incidence of giardiasis is unlikely to be confounded by variation in GP rate of specimens.

Barrow-in-Furness: a large community legionellosis outbreak in the UK.

A community outbreak of legionellosis occurred in Barrow-in-Furness, Cumbria, during July and August 2002. A descriptive study and active case-finding were instigated and all known wet cooling systems and other potential sources were investigated. Genotypic and phenotypic analysis, and amplified fragment length polymorphism of clinical human and environmental isolates confirmed the air-conditioning unit of a council-owned arts and leisure centre to be the source of infection. Subsequent sequence-based typing confirmed this link. One hundred and seventy-nine cases, including seven deaths [case fatality rate (CFR) 3·9%] were attributed to the outbreak. Timely recognition and management of the incident very likely led to the low CFR compared to other outbreaks. The outbreak highlights the responsibility associated with managing an aerosol-producing system, with the potential to expose and infect a large proportion of the local population and the consequent legal ramifications and human cost.

Is closure of entire wards necessary to control norovirus outbreaks in hospital? Comparing the effectiveness of two infection control strategies.

The standard approach for norovirus control in hospitals in the UK, as outlined by the Health Protection Agency guidance and implemented previously by Lancashire Teaching Hospitals, involves the early closure of affected wards. However, this has a major impact on bed-days lost and cancelled admissions. In 2008, a new strategy was introduced in the study hospital, key elements of which included closure of affected ward bays (rather than wards), installation of bay doors, enhanced cleaning, a rapid in-house molecular test and an enlarged infection control team. The impact of these changes was assessed by comparing two norovirus seasons (2007-08 and 2009-10) before and after implementation of the new strategy, expressing the contrast between seasons as a ratio (r) of expected counts in the two seasons. There was a significant decrease in the ratio of confirmed hospital outbreaks to community outbreaks (r = 0.317, P = 0.025), the number of days of restricted admissions on hospital wards per outbreak (r = 0.742, P = 0.041), and the number of hospital bed-days lost per outbreak (r = 0.344, P <0.001). However, there was no significant change in the number of patients affected per hospital outbreak (r = 1.080, P = 0.517), or the number of hospital staff affected per outbreak (r = 0.651, P = 0.105). Closure of entire wards during norovirus outbreaks is not always necessary. The changes implemented at the study hospital resulted in a significant reduction in the number of bed-days lost per outbreak, and this, together with a reduction in outbreak frequency, resulted in considerable cost savings.

Impact of a blood culture collection kit on the quality of blood culture sampling: fear and the law of unintended consequences.

Blood culture is a vital investigation and can be the first step in obtaining a definitive diagnosis in a patient with presumed sepsis, but can also have serious adverse consequences for the patient. The aim of this study was to evaluate the extent of the blood culture contamination problem at the Lancashire Teaching Hospitals (LTH) and to assess the impact of the introduction of a new blood culture collection kit on the contamination rate. Blood culture contamination rate at the LTH before the introduction of the blood culture collection kit was 9.2%. A fall in contamination rate was observed after kit introduction, to 3.8%, a proportion approaching the American Society of Microbiologists' recommended standard of ≤3%. The reduction in contamination was associated with an unintended, yet sustained, reduction in the total number of blood culture sets collected and an unwanted reduction in the number of genuine Gram-negative bacteraemias. This reduction may reflect education and training issues at the time of the introduction. In the era of 'route cause analyses', it may also reflect fears by junior colleagues of the consequences of being found responsible for a blood culture contaminant. The study recommended continuing with the blood culture kit, but ensuring regular training and education sessions, carried out in a non-blame manner.

Spatio-temporal epidemiology of Campylobacter jejuni enteritis, in an area of Northwest England, 2000-2002.

A total of 969 isolates of Campylobacter jejuni originating in the Preston, Lancashire postcode district over a 3-year period were characterized using multi-locus sequence typing. Recently developed statistical methods and a genetic model were used to investigate temporal, spatial, spatio-temporal and genetic variation in human C. jejuni infections. The analysis of the data showed statistically significant seasonal variation, spatial clustering, small-scale spatio-temporal clustering and spatio-temporal interaction in the overall pattern of incidence, and spatial segregation in cases classified according to their most likely species-of-origin.

Surveillance of giardiasis in Northwest England 1996-2006: impact of an enzyme immunoassay test.

The incidence of giardiasis in Central Lancashire increased following the introduction of a sensitive enzyme immunoassay diagnostic test in November 2002. We compared the epidemiological trends for 1996-2006 in Central Lancashire with a control area which used a standard wet preparation diagnostic method throughout. Poisson regression modelling was used to investigate trends in giardiasis before and after the introduction of the test. In the control area, incidence of giardiasis was four per 100,000 in 2005. In contrast, in Central Lancashire, the rates increased in temporal association with the introduction of the enzyme immunoassay test from 10.1 per 100,000 population in 2002 to 33.6 per 100,000 in 2006. The increase in giardiasis was unexplained by local factors including travel, outbreaks or sampling trends. The increase in giardiasis occurred in all age groups except for males aged 0-14 years and was most marked in males aged 25-44 years. The relative risk for trend post-test introduction in Central Lancashire was 1.11 (95% CI, 1.01-1.23). This suggests that the increase in giardiasis following the introduction of the sensitive enzyme immunoassay test was at least in part due to improved detection. There appears to be considerable under-diagnosis of giardiasis, particularly in adults. Additional research is required to evaluate the enzyme immunoassay test more widely. The test may assist in standardisation of diagnostic methods for giardiasis and enable more accurate estimation of disease burden and transmission routes.

Specific detection of Campylobacter jejuni from faeces using single nucleotide polymorphisms.

Specimens of human faeces were tested by a rapid strategy for detection of Campylobacter jejuni lineages by the presence of specific single nucleotide polymorphisms (SNPs) based on the C. jejuni multi locus sequence typing (MLST) scheme. This strategy was derived from analysis of the MLST databases to identify clonal complex specific SNPs followed by the design of real-time PCR assays to enable identification of six major C. jejuni clonal complexes associated with cases of human infection. The objective was to use the MLST SNP-based assays for the direct detection of C. jejuni by clonal complex from specimens of human faeces, and then confirm the accuracy of the clonal complex designation from the SNP-based assays by performing MLST on the cultured faecal material, this targeted at determining the validity of direct molecular specimen identification. Results showed it was possible to identify 38% of the isolates to one of the six major MLST clonal complexes using a rapid DNA extraction method directly from faeces in under 3 h. This method provides a novel strategy for the use of real-time PCR for detection and characterization beyond species level, supplying real-time epidemiological data, which is comparable with MLST results.

Blood pressure cuffs: friend or foe?

A study to assess the level of bacterial contamination of blood pressure cuffs in use on hospital wards was performed. Viable organisms were recovered from all the 24 cuffs sampled at a density of between 1000 and >25 000 colony-forming units/100 cm2. Potential pathogens were isolated from 14 cuffs (58%). Eleven cuffs grew a single pathogen and three cuffs grew a mixture, yielding a total of 18 isolates. Meticillin-susceptible Staphylococcus aureus was isolated from eight (33%) cuffs, meticillin-resistant S. aureus was isolated from two (8%) cuffs and Clostridium difficile was isolated from eight (33%) cuffs. This study serves as a reminder that hands are not the only fomite to go from patient to patient on hospital wards, and that measures should be taken to reduce the risks posed by blood pressure cuffs.

Severe sepsis following wound infection by an unusual organism--Clostridium novyi.

We present a case of post-operative wound infection with Clostridium novyi in a non-intravenous drug user. Clinical features included progressive cellulitis despite being on antibiotics, accompanied by hypotension, marked leucocytosis and oedema but minimal fever. While established infection with this organism is associated with high mortality, our patient survived. The administration of clindamycin and intravenous immunoglobulin in addition to early surgical assessment and aggressive debridement of affected tissue may have contributed to this successful outcome. To our knowledge, this is the only reported post-operative wound infection due to this pathogen.

Impact of changes in antibiotic policy on Clostridium difficile-associated diarrhoea (CDAD) over a five-year period in a district general hospital.

The impact of changes in antibiotic policy on Clostridium difficile-associated diarrhoea (CDAD), over a five-year period between 1995 and 2000, were studied in the Preston Acute Hospitals Trust. In 1996 the policy was changed in the Preston Acute Hospitals Trust from cefotaxime to ceftriaxone for initial treatment of severe sepsis or pneumonia in medical patients. Over the next nine months the average number of patients with C. difficile toxin-positive stools per quarter increased from 16 to 39. The predicted use of ceftriaxone exceeded by 65% an estimate based on prior use of cefotaxime. A policy of restricted duration of ceftriaxone was introduced, and although this reduced usage by over 50%, CDAD continued at an average of 9.2 cases per month, despite withdrawal of oral cephalosporins in December 1998. In August 1999 levofloxacin was substituted for ceftriaxone in the policy. The incidence of CDAD fell progressively to five cases per month by 2000. It would appear that a short (typically three dose) course of third-generation cephalosporin poses a similar risk for CDAD as a more prolonged course. The six-month delay in the decline of CDAD after virtual withdrawal of cephalosporins may reflect a slowly diminishing environmental reservoir.

Large outbreak of infection with Escherichia coli O157 PT21/28 in Eccleston, Lancashire, due to cross contamination at a butcher's counter.

An outbreak of infection with Escherichia coli O157 Phage Type 21/28 occurred between the 23rd November 2001 and the 7th December 2001 in Eccleston, Lancashire. There were 30 confirmed cases (23 with positive faecal isolates and seven serologically positive). Eccleston is a village of approximately 5,000 inhabitants with a single medical practice where many of the cases were patients. Initial investigations identified the suspected source as a butcher's counter, operated as a franchise, in a supermarket in Eccleston. The butcher closed voluntarily on the 24th November. The median age of cases was 60 with a mean of 56 and a range of 2-91 years. Of the 30 confirmed cases, 22 were admitted to hospital. Two patients developed serious complications but all 30 made a full recovery. Microbiological investigations confirmed the butcher's counter as the source of the outbreak. The epidemiological evidence implicated cooked meats and microbiological evidence confirmed that contamination had occurred between raw and cooked meats. The deficiencies in meat hygiene practice that were identified could have led to the cross contamination. This outbreak illustrates the risk associated with the handling of raw and cooked meats in the same shop. Complete physical separation of raw and cooked meat operations reduces the risk of such outbreaks.

The serodiagnosis of infection with Salmonella typhi.

BACKGROUND/AIMS: The serodiagnosis of infection with Salmonella typhi, using the Widal agglutination assay, relies on patients' antibodies to the O = 9,12 lipopolysaccharide (LPS) antigens, H = d flagellar antigens, and the Vi capsular antigens. A Vi agglutination titre of > 1/40 has traditionally been regarded as indicative of recent infection with S typhi. In this study, 91 sera were used to assess the reliability of the Widal agglutination assay based on antibodies to the Vi antigens. METHODS: The Widal agglutination assay was carried out using protocols established by the Central Public Health Laboratory, Colindale. Antibodies to the Vi capsular antigen were detected using a standard preparation of S typhi, ViI Bhatnagar variant strain (S typhi, ViI). Sera used in the study comprised 73 from patients who were culture positive for S typhi, 10 from patients who were culture positive for other species of Salmonella not expressing a Vi antigen (namely, S javiana, S enteritidis, S typhimurium, S stanley, S saint paul, S bareilly, or S mbandaka), and eight from healthy blood donors. RESULTS: Agglutination titres of > or = 1/40 were detected to S typhi ViI in 69 of 73 sera from patients with typhoid, although 27 of these also agglutinated an unrelated control antigen. The Widal assay also detected significant amounts of agglutinating antibodies to S. typhi ViI in all eight control sera and seven sera from patients infected with S bareilly, S enteritidis, S javiana, S mbandaka, S saint paul, and S stanley. CONCLUSIONS: Agglutinating antibodies to the Vi antigen can be detected by the Widal assay, but even with the appropriate control antigens the results were unreliable. The serodiagnosis of infections with S typhi should be based on the detection of antibodies to both the O = 9,12 LPS antigen and the H = d flagellar antigen by immunoblotting, and should not use the Vi antigen-based Widal assay. Conclusions should be made in the light of patients' clinical details and any knowledge of previous immunisation for typhoid.

Widespread environmental contamination with Norwalk-like viruses (NLV) detected in a prolonged hotel outbreak of gastroenteritis.

A protracted outbreak of Norwalk-like virus (NLV)-associated gastroenteritis occurred in a large hotel in North-West England between January and May 1996. We investigated the pattern of environmental contamination with NLV in the hotel during and after the outbreak. In the ninth week, 144 environmental swabs taken from around the hotel were tested for NLV by nested RT-PCR. The sites were categorized according to the likelihood of direct contamination with vomit/faeces. The highest proportion of positive samples were detected in directly contaminated carpets, but amplicons were detected in sites above 1.5 m which are unlikely to have been contaminated directly. The trend in positivity of different sites paralleled the diminishing likelihood of direct contamination. A second environmental investigation of the same sites 5 months after the outbreak had finished were all negative by RT-PCR. This study demonstrates for the first time the extent of environmental contamination that may occur during a large NLV outbreak.

Management of hospital outbreaks of gastro-enteritis due to small roundstructured viruses.

Small round structured viruses (SRSVs, Norwalk-like viruses, NLVs) are the most common cause of outbreaks of gastro-enteritis in hospitals and also cause outbreaks in other settings such as schools, hotels, nursing homes and cruise ships. Hospital outbreaks often lead to ward closure and major disruption in hospital activity. Outbreaks usually affect both patients and staff, sometimes with attack rates in excess of 50%. For this reason, staff shortages can be severe, particularly if several wards are involved at the same time. SRSVs may be spread by several routes: faecal-oral; vomiting/aerosols; food and water. Viruses may be introduced into the ward environment by any of these routes and then propagated by person-to-person spread. In an outbreak setting, the diagnosis can usually be made rapidly and confidently on clinical and epidemiological grounds, particularly if vomiting is a prominent symptom. By the time an SRSV outbreak has been recognized at ward level, most susceptible individuals will have been exposed to the virus and infection control efforts must prioritize the prevention of spread of infection to other clinical areas bycontainment of infected/exposed individuals (especially the prevention of patient and staff movements to other areas), hand-hygiene and effective environmental decontamination. This report of the Public Health Laboratory Service Viral Gastro-enteritis Working Group reviews the epidemiology of outbreaks of infection due to SRSVs and makes recommendations for their management in the hospital setting. The basic principles which underpin these recommendations will also be applicable to the management of some community-based institutional outbreaks.