Quantum phase retrieval of a Rydberg wave packet using a half-cycle pulse.

A terahertz half-cycle pulse was used to retrieve information stored as quantum phase in an N-state Rydberg atom data register. The register was prepared as a wave packet with one state phase reversed from the others (the "marked bit"). A half-cycle pulse then drove a significant portion of the electron probability into the flipped state via multimode interference.

Associations between heat-stable (O) and heat-labile (HL) serogroup antigens of Campylobacter jejuni: evidence for interstrain relationships within three O/HL serovars.

A comparative examination of the heat-stable (O) and heat-labile (HL) serogrouping results for 9,024 sporadic human isolates of Campylobacter jejuni revealed conserved associations between specific O and HL antigens (O/HL serovars). Forty-nine percent of the isolates which grouped for both O and HL antigens belonged to one of three serovars: O 4 complex/HL 1 (17.9%), O 1/HL 2 (16.8%), or O 50/HL 7 (14.5%). Other common serovars were O 2/HL 4 (8.3%), O 6/HL 6 (8.1%), O 53/HL 11 (4.5%), O 19/HL 17 (3.3%), O 5/HL 9 (3.3%), O 9/HL 9 (3.2%), and O 23/HL 5 (3.1%). These 10 serovars accounted for 83.1% of the serogroupable isolates. A large number of strains (41.3%) could be typed by only one of the two methods or could not be serogrouped (11%). Strains belonging to three serovars, O 2/HL 4, O 50/HL 7, and O 23/HL 5, were further characterized by combining data from expressed features (O/HL serogroups, phage groups, and biotypes) with restriction fragment length polymorphism genotypes. These polyphasic data demonstrated that within each serovar, individual isolates showed substantial conservation of both genomic and phenotypic characteristics. The essentially clonal nature of the three serovars confirmed the potential of combined O and HL serogrouping as a practical and phylogenetically valid method for investigating the epidemiology of sporadic C. jejuni infection.

The application of genotyping techniques to the epidemiological analysis of Campylobacter jejuni.

Campylobacter jejuni serogroup reference strains and collections of sporadic and outbreak-associated isolates were examined for restriction fragment length polymorphisms (RFLPs), using C. jejuni random chromosomal and 16S rRNA gene probes. A collection of 48 Penner (HS) and 14 Lior (HL) serogroup reference strains, plus 10 clinical isolates, generated 35 RFLP and 26 ribotype patterns. In combination the two loci generated 48 distinct genotypes. Both probes were able to differentiate between certain random isolates of the same HS/HL serogroups but greater discrimination was obtained with RFLP than with ribotyping. Genotyping distinguished accurately between related and unrelated strains when applied to several outbreaks. Genotypic analysis of C. jejuni by restriction fragment length polymorphisms is a valuable technique for epidemiological typing. Chromosomal variation detected by the two unlinked probe loci provides some information about the genetic relationship between isolates.

A comparison of a new campylobacter selective medium (CAT) with membrane filtration for the isolation of thermophilic campylobacters including Campylobacter upsaliensis.

The newly developed CAT campylobacter selective medium employing the blood-free charcoal-based agar containing cefoperazone (8 mg l-1), amphotericin (10 mg l-1) and teicoplanin (4 mg l-1) was compared with the membrane filtration culture technique for isolation of Campylobacter spp. including Camp. upsaliensis. Nine hundred and fifty human, 275 dog and 65 cat faeces (in which modified CCDA medium was also compared) were tested. In addition, the recovery of Camp. upsaliensis from pure cultures and from spiked human faeces was examined after membrane filtration. A 50-fold reduction in recovery after filtration using the 0.65 micron filters and a 150-fold reduction using the 0.45 micron filters was found. Recovery of Camp. upsaliensis from spiked faeces was considerably improved using the CAT medium compared with filtration, especially with the lower concentration of organisms (approx. 10(4) cfu mL-1). Campylobacter upsaliensis was recovered from 91 specimens of animal faeces, with CCDA recovering 26 isolates (29%), CAT recovering 76 isolates (84%) and membrane filtration (0.65 microns) recovering 82 isolates (90%). CAT selective agar was found to be a suitable medium for the isolation of thermophilic campylobacters including Camp. upsaliensis from faecal samples.

How to produce a hospital disinfection policy.

The steps required to produce and implement a hospital disinfection policy are discussed including: the formation of the team responsible for the policy; the investigation and compilation of current methods of decontamination; assessment of these methods and selection of the best options by reference to model disinfection policies; planning and producing the policy; choosing the best format; implementation of the policy and staff training; and auditing and updating the policy. Guidance is given on the selection of suitable procedures for decontamination of the environment, the skin and mucous membranes, and endoscopes and other items.

The problems of tracing a geographically widespread outbreak of salmonellosis from a commonly eaten food: Salmonella typhimurium DT193 in north west England and north Wales in 1991.

Geographically widespread outbreaks involving commonly isolated organisms and where the vehicles of infection are commonly eaten foodstuffs pose particular difficulties at a technical and organizational level. An outbreak of Salmonella typhimurium infection, affecting 39 people, spread over a wide area in North West England and North Wales in April and May 1991, was detected thanks to the practice of sending specimens to the national reference laboratory where phage typing and characterizing of antibiotic resistance patterns enabled the identification of a cluster of distinctive isolates (S. typhimurium DT193 resistant to sulphonamides, trimethoprim and furazolidone). An investigation, involving twenty environmental health departments in addition to health authorities and the Public Health Laboratory Service, showed an association between the illness and eating loose sliced cooked ham (P = 0.004). Detailed tracing of the chain of supply of the ham showed this to be particularly cooked ham originating from a single small local producer (P = 0.00003). Further investigation of that producer revealed that a batch of ham distributed on one day in early April was undercooked due to a malfunction in cooking equipment.

Verotoxin producing Escherichia coli O 157 infections associated with the consumption of yoghurt.

Sixteen cases of verotoxin producing Escherichia coli (VTEC) O 157:H7 Phage Type 49 infection were identified in the North West of England from 1 September to 1 November 1991, eight of whom lived in or around the same large town. Eleven of the cases were aged 10 years or less, and five of the affected children developed haemolytic uraemic syndrome. A case control study demonstrated a strong association between VTEC O 157:H7 PT 49 infection and the consumption of a locally produced live yoghurt. This is the first time that an outbreak of VTEC O 157 infection has been linked to the consumption of yoghurt and this vehicle of infection should be considered when investigating such outbreaks in future.

Selective medium for thermophilic campylobacters including Campylobacter upsaliensis.

AIMS: To develop a selective supplement for the recovery of thermophilic Campylobacter spp, including Campylobacter upsaliensis from faeces, using campylobacter blood free selective agar base as the growth medium. METHODS: Minimum inhibitory concentrations (MICs) of cefoperazone and of teicoplanin were determined for 51 strains of C upsaliensis, 159 strains of other thermophilic Campylobacter spp, and for 66 Enterobacteriaceae (cefoperazone only). From these results a medium using campylobacter blood free selective agar base incorporating cefoperazone (8 mg/l), amphotericin (10 mg/l), and teicoplanin (4 mg/l)--CAT medium--was formulated and compared with the commercially available campylobacter blood free selective medium (modified CCDA) for isolation of Campylobacter spp from 7000 human faecal specimens. The two media were also compared for the recovery of C upsaliensis from 45 spiked human faeces. RESULTS: Isolation rates of Campylobacter spp other than C upsaliensis were similar for both media, but the CAT medium alone recovered four of the five strains of C upsaliensis from the faecal samples examined. From the spiked faeces specimens, recovery of C upsaliensis was increased by between 35% and over 200-fold on the CAT medium compared with the modified CCDA. CONCLUSIONS: CAT selective agar was a suitable alternative medium to modified CCDA for the growth of thermophilic Campylobacter spp, including C upsaliensis from faeces.

Legionnaires' disease in elderly people: the first sign of an outbreak in the community?

Legionella pneumophila is responsible for up to 5% of cases of community-acquired pneumonia and mainly affects people aged over 50 years. The confirmation of legionellosis in two elderly patients living close to each other prompted a search for other cases. A total of eleven subjects with legionnaires' disease was recognized. The clinical findings are described and the diagnosis of legionellosis is discussed. Environmental investigations pointed to a cooling tower in the local town centre as the probable source of infection.

Improved isolation of salmonellae from faeces using a semisolid Rappaport-Vassiliadis medium.

A modified semisolid Rappaport-Vassiliadis (MSRV) enrichment medium was evaluated as an alternative to Rappaport-Vassiliadis (RV) broth for culture of salmonellae from faeces. Faeces from 1544 subjects were cultured using MSRV medium, selective agars, and RV and selenite F enrichment broths. Of the 183 strains of Salmonella spp. isolated, 88% were recovered on MSRV medium, whilst only 59% were recovered using RV broth. When MSRV medium was combined with direct culture and selenite enrichment, 98.9% of salmonellae were recovered. The MSRV culture was found to be easy to read, and in most cases confirmation of organisms as Salmonella spp. could be made 24 hours after receipt of the faecal specimen.

New selective medium for isolating Clostridium difficile from faeces.

AIMS: To compare CCFA (cycloserine, cefoxitin fructose agar) with a new selective medium CDMN (containing cysteine hydrochloride, norfloxacin, and moxalactam) for the isolation of Clostridium difficile after direct faecal culture. METHODS: The minimum inhibitory concentration (MIC) of norfloxacin was determined for 64 strains of C difficile, 17 strains of other Clostridium sp, and 66 various isolates of faecal origin, together with MIC determinations of moxalactam against the 81 strains of Clostridium sp and 15 isolates of Bacteroides sp. Using C difficile agar base with 0.5 g/l of cysteine hydrochloride, norfloxacin and moxalactam were incorporated into the medium and compared with CCFA for the isolation of C difficile after direct faecal culture. RESULTS: Norfloxacin (12 mg/l) inhibited the growth of enterobacteriaceae and faecal streptococci; moxalactam (32 mg/l) inhibited the growth of most strains of Bacteroides sp tested, together with Clostridium sp other than C difficile. Using the antibiotics in combination (CDMN), the growth and colonial morphology of 64 strains of C difficile were unaffected. When CDMN medium was compared with CCFA for the isolation of C difficile from 832 faeces from inpatients with diarrhoea, the CDMN agar isolated 20% more strains and reduced the number of contaminating colonies by 30%. CONCLUSIONS: CDMN both improves the isolation rate of C difficile from faecal specimens and reduces the growth of other organisms compared with CCFA.

Detection of Clostridium perfringens and its enterotoxin in cases of sporadic diarrhoea.

AIMS: To determine the incidence of sporadic and apparently non-food related diarrhoea associated with Clostridium perfringens enterotoxin. METHODS: Enzyme linked immunosorbent assay (ELISA) and reversed phase latex agglutination (RPLA) were used to detect C perfringens enterotoxin in faecal specimens from 818 sporadic cases of diarrhoea. RESULTS: C perfringens enterotoxin was identified as a cause of sporadic diarrhoea in 56 of 818 (6.8%) cases. Diarrhoea was prolonged (three days or more) in most cases. Ages ranged from 3 months to 89 years, although most patients were over 60 years of age. CONCLUSIONS: These results suggest that C perfringens may be a cause of sporadic cases of diarrhoea when causes such as food consumption or cross-infection are absent, particularly in the elderly.

Application of a new phagetyping scheme to campylobacters isolated during outbreaks.

A new scheme for phagetyping campylobacters has been evaluated using strains isolated from five outbreaks. The phagetyping results have been compared with the results of Penner serotyping, Lior serotyping and Preston biotyping. Phagetyping recognized the causative strains in all of the incidents and also differentiated these strains from animal and environmental strains isolated during these investigations. In some outbreaks phagetyping proved to be more discriminatory than serotyping or biotyping, e.g. strains of Penner serotype 2, and serogroup 4, 13, 16, 50 were subdivided by this method. Phagetyping is to be recommended for typing strains from outbreaks and although the results indicate that it may be used alone we advocate that it should be used in conjunction with one of the established typing methods.

The Stafford outbreak of Legionnaires' disease.

A large outbreak of Legionnaires' disease was associated with Stafford District General Hospital. A total of 68 confirmed cases was treated in hospital and 22 of these patients died. A further 35 patients, 14 of whom were treated at home, were suspected cases of Legionnaires' disease. All these patients had visited the hospital during April 1985. Epidemiological investigations demonstrated that there had been a high risk of acquiring the disease in the out patient department (OPD), but no risk in other parts of the hospital. The epidemic strain of Legionella pneumophila, serogroup 1, subgroup Pontiac 1a was isolated from the cooling water system of one of the air conditioning plants. This plant served several departments of the hospital including the OPD. The water in the cooling tower and a chiller unit which cooled the air entering the OPD were contaminated with legionellae. Bacteriological and engineering investigations showed how the chiller unit could have been contaminated and how an aerosol containing legionellae could have been generated in the U-trap below the chiller unit. These results, together with the epidemiological evidence, suggest that the chiller unit was most likely to have been the major source of the outbreak. Nearly one third of hospital staff had legionella antibodies. These staff were likely to have worked in areas of the hospital ventilated by the contaminated air conditioning plant, but not necessarily the OPD. There was evidence that a small proportion of these staff had a mild legionellosis and that these 'influenza-like' illnesses had been spread over a 5-month period. A possible explanation of this finding is that small amounts of aerosol from cooling tower sources could have entered the air-intake and been distributed throughout the areas of the hospital served by this ventilation system. Legionellae, subsequently found to be of the epidemic strain, had been found in the cooling tower pond in November 1984 and thus it is possible that staff were exposed to low doses of contaminated aerosol over several months. Control measures are described, but it was later apparent that the outbreak had ended before these interventions were introduced. The investigations revealed faults in the design of the ventilation system.

An outbreak of foodborne botulism associated with contaminated hazelnut yoghurt.

The largest recorded outbreak of foodborne botulism in the United Kingdom occurred in June 1989. A total of 27 patients was affected; one patient died. Twenty-five of the patients had eaten one brand of hazelnut yoghurt in the week before the onset of symptoms. This yoghurt contained hazelnut conserve sweetened with aspartame rather than sugar. Clostridium botulinum type B toxin was detected in a blown can of hazelnut conserve, opened and unopened cartons of hazelnut yoghurt, and one faecal specimen. Cl. botulinum type B was subsequently cultured from both opened and unopened cartons of the hazelnut yoghurt and from one faecal specimen. Investigations indicated that the processing of the conserve was inadequate to destroy Cl. botulinum spores. Control measures included the cessation of all yoghurt production by the implicated producer, the withdrawal of the firm's yoghurts from sale, the recall of cans of the hazelnut conserve, and advice to the general public to avoid the consumption of all hazelnut yoghurts.

Evaluation of three Campylobacter pylori antigen preparations for screening sera from patients undergoing endoscopy.

A surface antigen (SA), acid glycine extract (AGE), and urease preparation (UP) were evaluated using sera from patients undergoing endoscopy and from subjects with gastric or duodenal ulcers. Sera were tested for the presence of IgG and IgA antibodies by a conventional indirect enzyme linked immunosorbent assay (ELISA). In patients with confirmed Campylobacter pylori associated gastritis, raised IgG antibody titres were indicated by absorbance values of greater than or equal to 500, greater than or equal to 500, and greater than or equal to 1500 for the SA, AGE, and UP, respectively. Corresponding values for the IgA assay were greater than or equal to 500, greater than or equal to 500, and greater than or equal to 1000. The specificity of the IgG assays were 94%, 92%, and 90% for the AGE, SA, and UP, respectively. In contrast, the UP was the most sensitive (97%); the other two antigen preparations gave values of 82%. In the IgA assay the UP showed the greatest specificity (90%) and sensitivity (90%). The predictive value for a true positive for the IgG assay was the same for all antigens (93%), whereas the UP gave a predictive value for a true negative of 96% compared with 79% for the other two antigen preparations. Of the patients with gastric or duodenal ulcers, raised antibody titres to SA were found in 72% (IgG) and 73% (IgA), to AGE in 75% (IgG) and 63% (IgA), and to UP in 77% (IgG) and 75% (IgA). The use of a urease antigen preparation to determine IgG antibody is recommended for screening patients undergoing endoscopy.

Campylobacter pylori: clinical, histological, and serological studies.

The presence of Campylobacter pylori, histologically diagnosed gastritis, and antibodies to C pylori were determined in a series of 113 patients undergoing endoscopy. Paired biopsy specimens from the fundus, body, and antrum were collected from 59 patients and from the antrum of 54 patients. The presence of C pylori was confirmed by either culture or silver stain in 30 of 59, 31 of 59, and 54 of 103 biopsy specimens from the fundus, body, and antrum, respectively. Of the specimens which contained C pylori 20 of 30 (66%) from the fundus, 25 of 31 (80%) from the body, and 54 (100%) from the antrum showed gastritis. C pylori and gastritis were shown in seven of nine (78.1%) of patients with gastric ulcers and in nine of 11 (82%) of patients with duodenal ulcers. Using an enzyme linked immunosorbent assay (ELISA) technique to detect IgG antibody to C pylori, all patients with histologically diagnosed gastritis and organisms present had titres of greater than or equal to 640; eight of 39 (21%) of patients without gastritis and without organisms gave similar titres. Hence the presence of C pylori was associated with gastritis and with raised titres of IgG antibody.