Comparison of the effect of detergent versus hypochlorite cleaning on environmental contamination and incidence of Clostridium difficile infection

To determine how best to decontaminate the hospital environment of Clostridium difficile, we carried out a cross-over study on two elderly medicine wards to determine whether cleaning with a hypochlorite disinfectant was better than using neutral detergent in reducing the incidence of C. difficile infection (CDI). We examined 1128 environmental samples in two years, 35% of which grew C. difficile. There was a significant decrease of CDI incidence on ward X, from 8.9 to 5.3 cases per 100 admissions (P<0.05) using hypochlorite, but there was no significant effect on ward Y. On ward X the incidence of CDI was significantly associated with the proportion of culture-positive environmental sites (P<0.05). On ward Y the only significant correlation between CDI and C. difficile culture-positive environmental sites was in patient side-rooms (r=0.41, P<0.05). The total daily defined doses of cefotaxime, cephradine and aminopenicillins were similar throughout the trial. These results provide some evidence that use of hypochlorite for environmental cleaning may significantly reduce incidence of CDI, but emphasize the potential for confounding factors.     

Acquisition of Clostridium difficile from the hospital environment

An outbreak of antibiotic-associated colitis that occurred on a ward of a Michigan hospital during February-April, 1984, was studied by bacteriophage-bacteriocin typing. Stools from the seven involved patients yielded Clostridium difficile isolates of types B1537 or Cld7;B1537. C. difficile was recovered from 31.4% of environmental cultures obtained on the ward, and the majority of isolates were types B1537 or Cld7;B1537. When the ward was disinfected with unbuffered hypochlorite (500 parts per million (ppm) available chlorine), surface contamination decreased to 21% of initial levels and the outbreak subsequently ended. Phosphate buffered hypochlorite (1,600 ppm available chlorine, pH 7.6) was even more effective; its use resulted in a 98% reduction in surface contamination. These findings suggest that environmental contamination with C. difficile is important in the epidemiology of antibiotic-associated colitis, and that hypochlorite is effective in eliminating C. difficile from the hospital environment.     

Prospective evaluation of environmental contamination by Clostridium difficile in isolation side rooms.

We determined prospectively the frequency, persistence and molecular epidemiology of Clostridium difficile environmental contamination after detergent-based cleaning in side rooms used to isolate patients with C. difficile diarrhoea. Approximately one-quarter of all environmental sites in side rooms sampled over four-week periods were contaminated with C. difficile. The overall side room prevalence of environmental C. difficile declined from 35% initially, to 24% in week 2, 18% in week 3, and 16% in week 4. The bed frame was the most common site from which C. difficile was recovered, although the floor was the most contaminated site in terms of total numbers of colonies. C. difficile was recovered significantly more frequently from swabs plated directly on to C. difficile selective media containing lysozyme than from enrichment broth (P< 0.001), emphasizing the benefit of lysozyme supplementation. The great majority of C. difficile isolates (87% of all isolates, 84% of patient isolates) was indistinguishable from the UK epidemic strain (PCR ribotype 1). It thus could not be determined whether environmental contamination was a cause or a consequence of diarrhoea. Our findings highlight the need for improved approaches to hospital environmental hygiene, and call into question current UK guidelines that recommend detergent-based cleaning to remove environmental C. difficile. In particular, improved cleaning of frequently touched sites in the immediate bed space area is required.     

Activity of a dry mist hydrogen peroxide system against environmental Clostridium difficile contamination in elderly care wards

Clostridium difficile causes serious healthcare-associated infections. Infection control is difficult, due in part to environmental contamination with C. difficile spores. These spores are relatively resistant to cleaning and disinfection. The activity of a dry mist hydrogen peroxide decontamination system (Sterinis((R))) against environmental C. difficile contamination was assessed in three elderly care wards. Initial sampling for C. difficile was performed in 16 rooms across a variety of wards and specialties, using Brazier's CCEY (cycloserine-cefoxitin-egg yolk) agar. Ten rooms for elderly patients (eight isolation and two sluice rooms) were then resampled following dry mist hydrogen peroxide decontamination. Representative isolates of C. difficile were typed by polymerase chain reaction ribotyping. C. difficile was recovered from 3%, 11% and 26% of samples from low, medium and high risk rooms, respectively. In 10 high risk elderly care rooms, 24% (48/203) of samples were positive for C. difficile, with a mean of 6.8 colony-forming units (cfu) per 10 samples prior to hydrogen peroxide decontamination. Ribotyping identified the presence of the three main UK epidemic strains (ribotypes 001, 027 and 106) and four rooms contained mixed strains. After a single cycle of hydrogen peroxide decontamination, only 3% (7/203) of samples were positive (P<0.001), with a mean of 0.4 cfu per 10 samples ( approximately 94% reduction). The Sterinis((R)) hydrogen peroxide system significantly reduced the extent of environmental contamination with C. difficile in these elderly care rooms. This relatively quick and user-friendly technology might be a more reliable method of terminally disinfecting isolation rooms, following detergent cleaning, compared to the manual application of other disinfectants.     

A hospital outbreak of antibiotic-resistant Acinetobacter anitratus: epidemiology and control

Between 23 January and 18 June, 1979 an epidemic strain of Acinetobacter anitratus, recognizable by its characteristic biotype and non-transferable resistance to 18 antibiotics, was isolated from 40 patients in six wards. Most isolates were from the urine of catheterized male patients in a urological ward, some of whom had skin but not rectal colonization. Elimination of environmental contamination did not alter the course of the outbreak, and respirators were not implicated. Transmission of the epidemic strain from patients' skin to staff hands was demonstrated experimentally, and of 38 staff working in affected wards, 11 had positive hand cultures. Two microbiologists investigating the outbreak also became hand carriers. Following prompt identification of new cases and closer attention to staff hand washing no further cases were seen.     

Environmental contamination with an epidemic strain of Pseudomonas aeruginosa in a Liverpool cystic fibrosis centre, and study of its survival on dry surfaces

We conducted an environmental survey in the Liverpool adult cystic fibrosis (CF) centre in order to determine the extent of environmental contamination with an epidemic strain of Pseudomonas aeruginosa that colonizes most CF patients in Liverpool, and to identify possible reservoirs and routes of cross-infection. In addition, we studied the survival of this strain on dry surfaces, compared with that of other CF P. aeruginosa strains, to explore factors that might contribute to its high transmissibility. Samples were collected from staff, patients and the environment (drains, bath tubs, showers, dry surfaces, respiratory equipment and air) in the inpatient ward and outpatient clinic. P. aeruginosa strains were tested using a new polymerase chain reaction amplification assay specific for the Liverpool epidemic strain (LES). LES was isolated from patients' hands, clothes and bed linen. Environmental contamination with LES was only detected in close proximity to colonized patients (external surfaces of their respiratory equipment, and spirometry machine tubing and chair) and was short-lived. No persistent environmental reservoirs were found. LES was detected in the majority of air samples from inside patients' rooms, the ward corridor and the outpatient clinic. Survival of LES on dry surfaces was significantly longer than that for some other strains tested, but not compared with other strains shown not to be transmissible. Improved environmental survival on its own, therefore, cannot explain the high transmissibility of this epidemic strain. Our study suggests that airborne dissemination plays a significant role in patient-to-patient spread of LES, and confirms the need to segregate those patients colonized by epidemic P. aeruginosa strains from all other CF patients.     

Environmental survey to assess viral contamination of air and surfaces in hospital settings

This report describes an outbreak of Clostridium difficile infection (CDI) in a vascular surgery ward in 2009 caused by a high-level clindamycin-resistant ribotype 106. A case of CDI was defined as a patient with diarrhoea, positive for C. difficile toxin and negative for other enteric pathogens. Cultures were sent to the Scottish Salmonella Shigella and Clostridium difficile Reference Laboratory (SSSCDRL) for PCR ribotyping, antibiotic susceptibility testing and PCR detection of ermB. The mean age of the nine patients was 73 years (range: 38–90 years). All had received clindamycin and ciprofloxacin. All cases were typed as PCR ribotype 106 and they showed high-level resistance to clindamycin. Five of these isolates were tested by PCR for the presence of the ermB gene and no amplification was detected. This strain has rarely been isolated from patients on this ward. The outbreak was controlled successfully by closure of the ward with terminal cleaning, reinforcement of infection control precautions and the introduction of a new antibiotic policy. It is notable that this outbreak was caused by a strain with high-level clindamycin resistance not mediated by ermB. It also re-emphasizes that outbreaks of CDI can be caused by C. difficile PCR ribotypes other than 027. The outbreak was most likely associated with the use of clindamycin and ciprofloxacin cross-infection with spores in this environment. Implementation of strict infection control precautions, antimicrobial stewardship and enhanced environmental cleaning are key components in managing such an outbreak successfully. The number of meticillin-resistant Staphylococcus aureus acquisitions also fell substantially after these interventions.     

Clostridium difficile infection in patients with haematological malignant disease. Risk factors, faecal toxins and pathogenic strains

Two hundred and forty-eight patients from shared oncology and general medical wards were prospectively studied over a 6-month period for carriage of Clostridium difficile during an outbreak of clinical disease with an epidemic strain of the organism. Risk factors for infection were assessed. Acute leukaemia and/or its treatment were identified as significantly increasing the risk of infection. The relationship between the type of C. difficile isolated (as defined by a typing system based on the incorporation of [35S]methionine into bacterial proteins followed by gel electrophoresis), the presence of faecal toxins A and B and clinical symptoms were analysed. Carriage of the epidemic strain, type X, had a significant association with symptoms amongst oncology patients, with two thirds of these patients having detectable faecal toxin A and one third detectable faecal toxin B. During an outbreak of C. difficile-associated disease, typing the organism and assaying for both faecal toxins in symptomatic patients may be of benefit in determining which patients require specific, urgent treatment.     

Epidemiological study of invasive pulmonary aspergillosis in a haematology unit by molecular typing of environmental and patient isolates of Aspergillus fumigatus

In order to determine the possible relationship between environmental contamination by Aspergillus fumigatus and occurrence of invasive aspergillosis, a one-year prospective study was carried out in the haematology ward of Hautepierre Hospital, Strasbourg, France. During the study period, 21 environmental isolates and 26 clinical isolates of A. fumigatus were collected. Each was genotyped using a random amplification of polymorphic DNA (RAPD) technique. Thirty-four distinct profiles were identified by RAPD analysis, indicating the great genetic diversity of A. fumigatus isolated from infected patients and from the environment. For two patients, RAPD analysis demonstrated concurrent infection by at least two different strains. In two cases, a genetic similarity was noted between isolates obtained from a patient and from the environment.     

A molecular characterization of Clostridium difficile isolates from humans, animals and their environments.

It is generally accepted that most patients with Clostridium difficile-associated diarrhoea acquire the organism from the environment. Recently we demonstrated that household pets may constitute a significant reservoir of C. difficile through gastrointestinal carriage in up to 39% of cats and dogs. These findings suggested that direct transmission from household pets, or contamination of the environment by them, may be a factor in the pathogenesis of C. difficile-associated diarrhoea. To investigate this possibility, we examined isolates of C. difficile from humans, pets and the environment by restriction enzyme analysis (REA) and restriction fragment length polymorphism (RFLP) typing using enhanced chemiluminescence. Both REA and RFLP typing methods used Hind III digests of chromosomal DNA. A total of 116 isolates of C. difficile from pets (26), veterinary clinic environmental sites (33), humans (37) and hospital environmental sites (20) was examined. REA was far more discriminatory than RFLP typing and for all isolates there were 34 REA types versus 6 RFLP types. There was good correlation between the REA types found in isolates from pets and from the veterinary clinic environment, and between isolates from humans and from those found in the hospital environment. There was, however, no correlation between REA type of C. difficile found in pets and isolates of human origin. We conclude that there may still be a risk of humans acquiring C. difficile from domestic pets as these findings may be the result of geographical variation.     

A modified pulsed-field gel electrophoresis (PFGE) protocol for subtyping previously non-PFGE typeable isolates of Clostridium difficile polymerase chain reaction ribotype 001

A modified pulsed-field gel electrophoresis (PFGE) protocol was developed and applied to 50 isolates of the UK epidemic strain of Clostridium difficile, polymerase chain reaction (PCR) ribotype 001, to develop a PFGE-based subtyping scheme. This protocol overcame the inherent DNA degradation problems associated with typing this strain of C. difficile by this method, and whole genomic digestion with SmaI restriction enzyme yielded seven distinct and reproducible PFGE banding patterns. Modified PFGE is an appropriate method for subtyping C. difficile PCR ribotype 001 that could be used to improve epidemiological investigations.     

The epidemiology of glycopeptide-resistant enterococci on a haematology unit--analysis by pulsed-field gel electrophoresis

As part of an interventional study to determine glycopeptide-resistant enterococci (GRE) acquisition on a three-ward haematology unit, rectal swabs were taken weekly from 293 patients recruited to the study between June 1995 and December 1996. The GRE isolates obtained from the first positive rectal swab from 120 colonized patients, the isolates from 7 patients with clinical infection and 43 isolates obtained from the ward environment were compared by pulsed-field gel electrophoresis (PFGE). Sixty-three of 120 patients were colonized by one of strains A-H, while 49 were colonized by unique strains. The first 18 weeks were associated with the highest prevalence of GRE by rectal swab, with a single strain A responsible for 52% of acquisitions on ward 2, 22% on ward 3 and 36% on ward 4. Other smaller ward associated clusters were evident. Environmental sampling of ward 2 during this time showed that all but 2 of 30 isolates were indistinguishable from strain A. As the GRE prevalence fell, rectal swab and environmental isolates became more heterogeneous, and strain A disappeared after week 55. GRE prevalence rose again in the final 15 weeks of the study, and a new predominant strain B emerged on ward 2 responsible for 50% of new acquisitions. In the seven patients with clinical infection with GRE, the clinical isolates were compared with the contemporaneous rectal swab isolate, and were found to be the same in only two cases. An analysis of five long-term carriers colonized for a median of 19 weeks (range 11-34) showed colonization with at least two and in one case six distinct strains, raising the question of how many strains may be colonizing a patient at any one time, and suggesting that multiple colonies should be analysed. These data suggest that cross-infection was an important factor in the spread of GRE when the colonization rate was high.     

Spatial and temporal analysis of Clostridium difficile infection in patients at a pediatric hospital in California.

OBJECTIVE: To examine the usefulness of temporal and spatial analysis in identifying nosocomial transmission of Clostridium difficile among pediatric patients hospitalized on four wards at The Children's Hospital of Central California from September 8, 1998, to January 16, 1999. DESIGN: Stool specimens obtained from the clinical microbiology laboratory during the study period were tested by culture and latex agglutination for C. difficile. Polymerase chain reaction was used to identify toxin genes. Isolates obtained were mapped to a grid for each ward and were analyzed using the Knox test. Results were compared with DNA fingerprints generated by arbitrarily primed polymerase chain reaction. RESULTS: Total occupancy of these 4 wards was 438 during the study period. Stool specimens were available for 256 (58%) of these patients, yielding 67 C. difficile isolates and generating 2,211 case pairs for analysis by the Knox test. After stratification by toxin status, 5 clustered pairs of toxigenic isolates were identified on 1 of the wards by this method. Fingerprint analysis identified 4 clusters with indistinguishable banding patterns on 2 of the 4 wards. Two of the identified clusters were toxigenic and 2 were nontoxigenic. None of these clusters corresponded to clusters identified by the Knox test. CONCLUSIONS: The Knox test is an ineffective method for identifying cases resulting from nosocomial transmission of C. difficile in a pediatric setting due to the persistence of C. difficile spores and the unique environment of a pediatric hospital. Molecular analysis remains the most effective method.     

Epidemiology and susceptibility of serratia marcescens in a large general hospital over an 8-year period

Over the 8 year period 1988-1995, 1367 isolates of Serratia marcescens were isolated from 582 patients on 12 different wards of a large Dublin hospital and were particularly associated with the surgical intensive care unit. The annual incidence was over 200 isolates from 1990 to 1992 but fell to below 100 following the opening in April 1992 of a replacement surgical hospital incorporating a new intensive care unit on the same site. The most common source of S. marcescens was sputum from patients. Strain identities were determined by serotyping and phage typing at least one isolate from each of 311 of the 582 patients. The results showed that a single epidemic strain of serotype O14:K14 was present in 69% of these patients, and persisted throughout the hospital for the whole of the eight-year period. This strain was recovered from a variety of clinical specimens, including blood cultures. A minor outbreak involving a serotype O16:K28 strain also occurred and this strain also persisted from at least 1989 to 1994. Extensive surveillance failed to reveal an environmental source or faecal carriage. The likely mode of transmission appears to have been via staff hands from both symptomatic and asymptomatic patients acting as reservoirs of the organism, as has commonly been reported for this species.     

Norovirus in the hospital setting: virus introduction and spread within the hospital environment

Norovirus (NoV) strains were collected over a four-month period during 2009-2010 from hospitalised patients with symptoms of gastroenteritis. These were characterised in order to estimate how many strains were introduced into the hospital from the community. In addition, environmental swabbing was performed after clinical cleaning of bays or wards accommodating infected patients. This was performed in order to assess the efficiency of cleaning and identify any NoV contamination in the environment. A total of eight distinct genetic clusters of NoV GII-4 genotype were identified during the four-month period, with some wards experiencing multiple outbreaks with different GII-4 strains during the season. NoV was detected from 31.4% of environmental swabs post cleaning. Notes trolleys, computer keyboards, soap and alcohol dispensers, blood pressure equipment, pulse oximeters and tympanic thermometers were identified as NoV reservoirs but contamination was also found on surfaces around the bedside environment, and furniture, fixtures and fittings associated with toilets and shower rooms. The combination of detailed virus characterisation and environmental swabbing is a powerful tool for infection control audits to determine the size and scope of an outbreak and to monitor the efficiency of clinical cleaning.     

Management of an outbreak of Clostridium difficile-associated disease among geriatric patients.

OBJECTIVE: To describe a nosocomial outbreak of Clostridium difficile-associated disease (CDAD). DESIGN: A traditional outbreak investigation. SETTING: Geriatric department of a tertiary care teaching hospital from March through April 2003. METHODS: The outbreak was detected by the C. difficile surveillance program of the infection control unit. CDAD was diagnosed by stool culture and fecal toxin A detection with a qualitative rapid immunoassay. Isolates of C. difficile were serotyped and genotyped using pulsed-field gel electrophoresis. RESULTS: The incidence of CDAD increased from 27 cases per 100,000 patient-days in the 6-month period before the outbreak to 99 cases per 100,000 patient-days during the outbreak. This outbreak involved 21 of 92 patients in 4 geriatric wards, which were located at 2 geographically distinct sites and staffed by the same medical team. The mean age of patients was 83 years (range, 71-100 years). Five (24%) of the 21 patients had community-acquired diarrhea, and secondary hospital transmission resulted in 3 clusters involving 16 patients. Serotyping and genotyping were performed on isolates in stool specimens from 19 different patients; 16 of these isolates were serotype A1, whereas 3 displayed profiles different from the outbreak strain. Management of this outbreak consisted in reinforcement of contact isolation precautions for patients with diarrhea, cohorting of infected patients in the same ward, and promotion of hand hygiene. Relapses occurred in 6 (29%) of 21 patients. CONCLUSION: Control of this rapidly developing outbreak of CDAD was obtained with early implementation of cohorting and ward closure and reinforcement of environmental disinfection, hand hygiene, and enteric isolation precautions.     

耐亚胺培南铜绿假单胞菌的耐药性及分子流行病学研究

目的了解广州市某医院烧伤科病房亚胺培南耐药铜绿假单胞菌的耐药谱特点及分子流行病学情况。方法采用Kirby-Bauer法进行药物敏感性试验,应用随机扩增DNA多态性分析(RAPD)技术,对从不同患者连续分离到的48株耐药菌进行DNA分型。结果48株亚胺培南耐药菌株均为多重耐药菌,对临床常用的多种抗菌药物耐药,敏感率由高到低依次为CIP、TOB、AMK、GEN和FEP;RAPD图谱显示48株菌分别属于A、B、C、D 4个不同克隆,其中A型、B型是主要流行克隆。结论该院烧伤科病房亚胺培南耐药铜绿假单胞菌的流行主要是医院感染所致,流行株呈多重耐药。     

Relapse versus reinfection with Clostridium difficile.

Relapse of Clostridium difficile-associated diarrhoea occurs in 15-20% of patients; however, whether relapse is due to an endogenous source of the organism or reinfection from the environment remains unclear. Restriction enzyme analysis (REA) of chromosomal DNA was used to type multiple isolates from ten patients who had experienced apparent relapses. More than half the relapses were due to infection with a new strain of C. difficile. The remaining patients were infected with the same strain, but whether this strain was acquired from the environment or from endogenous sources could not be determined. Relapses with a different strain of C. difficile could occur if an individual harboured more than one strain in their gastrointestinal tract. To investigate this possibility ten other patients were assessed for carriage of multiple strains. Ten colonies from a primary culture plate from each patient were typed by REA and tested for their ability to produce cytotoxin. All isolates from the same patient were identical by both methods, indicating that multiple carriage of strains may be a rare event.     

The use of the PhP-KE biochemical fingerprinting system in epidemiological studies of faecal Enterobacter cloacae strains from infants in Swedish neonatal wards

The PhenePlate (PhP) biochemical fingerprinting system is an automated method for typing of bacteria, based on the evaluation of the kinetics of biochemical reactions, performed in microtitre plates. In the present study the PhP-Klebsiella/Enterobacter (KE) system was evaluated for typing of Enterobacter cloacae and employed to study the epidemiology of faecal E. cloacae strains isolated from infants in 22 Swedish neonatal wards. The PhP-KE system showed a high reproducibility and discrimination for E. cloacae isolates. Among 64 epidemiologically unrelated E. cloacae strains, 49 distinct phenotypes were found, and the diversity index was 0.985. E. cloacae was found as a part of the dominating Gram-negative aerobic bacterial flora in 83 out of 953 infants studied. The incidences of E. cloacae colonization varied between 0 and 35% in different wards, but in contrast to previous data for Klebsiella spp. and Escherichia coli, there was little evidence of spread of particular strains in the wards. We also discuss two different measures of nosocomial transmission of bacterial strains: transmissible strains and epidemic index.