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Summary Background Repeated outbreaks of salmonellosis caused by Salmonella enterica serovar Infantis at a rehabilitation clinic in Germany were investigated microbiologically from August 2002 to August 2009. Aim To identify the sources of transmission and characterize the S. enterica serovar Infantis isolates. Methods Associated with these outbreaks, isolates from 98 patients, two kitchen staff, five food samples, four swabs of kitchen facilities, three samples of chicken faeces and one sample of sewage water were evaluated by phage typing. All S. enterica serovar Infantis isolates investigated (N=113) were related to phage type (PT) 29. Additionally, 44 of the 113 isolates were selected at random for typing by XbaI macrorestriction and pulsed-field gel electrophoresis (PFGE). Findings Typing of the 44 isolates showed that the recurrent infections were caused by the single clone PT 29/XB27+44 (42/44, 95.5%). The most likely route of transmission was only identified in the last outbreak in 2009 within the present study. It was found to be cross-contamination in the kitchen facilities (emanating from a contaminated wooden panel), in combination with carriers among the kitchen staff. Conclusions This study demonstrated important details of hospital-specific epidemiological processes, and alludes to a long-term reservoir of an epidemic clone of S. enterica serovar Infantis either in a backyard flock of poultry or in an inanimate kitchen reservoir.

Summary Background Meticillin-sensitive Staphylococcus aureus (MSSA) is a frequent cause of surgical site infection (SSI), but point-source outbreaks are rarely recognized. Aim To describe an outbreak of MSSA SSI in a thoracic surgical unit. Methods An outbreak investigation was started following two postoperative bacteraemias with MSSA resistant to fusidic acid (MSSA FusR). Patients with MSSA FusR were identified from microbiology records and through prospective case finding. Healthcare workers (HCWs) were screened. Isolates were characterized by phage typing, spa typing, pulsed-field gel electrophoresis and toxin gene profiling. A case–control study examined the association between one HCW with MSSA FusR and the patients involved in the outbreak. Findings Nineteen patients were identified with MSSA FusR over 16 months. Four isolates were available for typing and all belonged to the same lineage. Seventy-six HCWs were screened. One was a carrier of the outbreak strain (a nurse with psoriasis). All 19 cases were exposed to this HCW compared with only 40/66 controls ( P = 0.003) and cases had a greater duration of exposure ( P = 0.00001, chi-squared for trend). Direct patient contact was documented in 15 cases. The outbreak was halted by thorough cleaning of the ward and removal of the HCW from clinical duty. Conclusion The HCW with psoriasis was the source of this outbreak. MSSA FusR may be a marker for strains associated with skin conditions. HCWs with significant skin conditions may pose an infection risk in surgical settings. Recommendations are made for occupational health teams regarding screening of HCWs with dermatitis.

Summary Since 1998, an increasing number of meticillin-resistant Staphylococcus aureus (MRSA) isolates with one of two characteristic phage patterns have been referred to the authors' laboratory from Northern Ireland. These strains were designated ‘Irish-1' and ‘Irish-2'. Analysis of 956 submitted isolates classified as Irish-1 or Irish-2 showed that 97% of the former and 95% of the latter were from Northern Ireland. Only 0.2% and 3%, respectively, were from England. Eleven Irish-2 isolates had been referred from Western Australia as representatives of an epidemic strain originally isolated there in 1994. Ninety isolates with the Irish-1 phage pattern and 91 isolates with the Irish-2 phage pattern, from numerous hospitals, were characterized by Sma I pulsed-field gel electrophoresis (PFGE), toxin gene carriage and antibiotic susceptibility. PFGE showed that, within each collection, a few isolates represented unrelated strains, but the majority were within six band differences of the most common profiles. Half of the Irish-1 isolates were homogeneous, with 22 DNA profiles among the remainder. Irish-2 isolates had two common profiles, D1 and D2, equally divided between one-third of the isolates and differing from each other by two bands; the remaining isolates shared 31 DNA profiles. Cluster analysis showed some overlap in DNA profiles between the Irish-1 and Irish-2 strains, but clear separation from other epidemic MRSA strains. There was no obvious correlation between PFGE profile and either antibiotic resistance pattern or toxin gene possession. All but three Irish-1 isolates possessed only the staphylococcal enterotoxin A ( sea ) gene, whereas almost all Irish-2 isolates were negative for all 12 enterotoxin genes. Sixty-nine percent of Irish-2 isolates were resistant to ciprofloxacin, erythromycin, kanamycin, neomycin and streptomycin, while 90% of Irish-1 isolates were resistant to all these plus gentamicin and mupirocin. All isolates were sensitive to quinupristin/dalfopristin, teicoplanin and vancomycin. Urease production was negative in both strains. The results suggest that Irish-1 and Irish-2 are distinct epidemic strains, identifiable by phage typing, DNA profiles, antibiotic resistance and toxin gene carriage.

Gradual changes have been observed in the phage-types of methicillin-resistant Staphylococcus aureus (MRSA) isolates from Belgian hospitals. A total of 6551 isolates, collected in 93 Belgian hospitals over 10 years (1992-2001), was examined. A decreasing incidence of the main early Belgian epidemic phage-types ([A], [B], [H]*, Jo*) was observed. Since 1997 and 2000, a new series of phage-types ([Hv]*, [J]*, [O]*), which were likely related to the previous group [H]*, have been noted. The general trends were confirmed in two particular hospitals. Local epidemic and/or endemic phage-types were also encountered.

The aim of this study was to optimize the epidemiological monitoring of strains of Staphylococcus aureus, a major cause of hospital-acquired infections. From September to December 1998 47 S. aureus strains isolated from swabs taken from orthopaedic and trauma patients were in studied. Thirty-five isolates were sensitive to methicillin (MSSA) and 12 were methicillin-resistant (MRSA). Ten of the 47 isolates could not be phage-typed using the international set of typing phages: five of these isolates were MSSA and five were MRSA. These MRSA isolates, which were also not typeable by the phages currently recommended for phage-typing MRSA, were lysed by locally isolated experimental phages 584 and 1814. Phage 1814 lysed the gentamicin-resistant MRSA and phage 584 acted on the gentamicin-sensitive MRSA. Both new phages were inactive against the methicillin-sensitive isolates. Cloning of certain isolates was confirmed by macrorestriction genomic profiles obtained by pulsed-field gel electrophoresis analysis (PFGE). The results showed good discriminatory ability of antibiotic-resistance pattern phenotyping and phage-typing when the phages used were adapted to epidemic-associated MRSA strains.

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.

Preventing cross-infection with epidemic strains of methicillin-resistant Staphylococcus aureus (MRSA) requires effective control measures. These call for simple, rapid, discriminatory and reproducible methods for typing this pathogen. In this study 140 isolates/strains from 105 hospitals in England and Wales, representing 72 diverse phage types, were analysed by bacteriophage typing and PCR coagulase (coa) gene restriction fragment length polymorphism (RFLP). Isolates gave a coa gene PCR product that was either 660 base pairs (bp), 603 bp or 547 pb in size. The PCR products were digested with Alu I and Cfo I, and the fragments separated by gel electrophoresis. Eight coa gene RFLP patterns, numbered 1 to 8, were observed. Pattern 3 was most common (N = 25 isolates), followed by patterns 2 and 5 (18 isolates each), pattern 1 (14 isolates), pattern 4 (11 isolates), pattern 7 (10 isolates), pattern 8 (eight isolates) and pattern 6 (six isolates). Isolates of the same phage type often gave different coa gene RFLP patterns, and the patterns within the epidemic types EMRSA-03, EMRSA-15 and EMRSA-16 were heterogeneous. Thus, representatives of EMRSA-03 were subtyped to coa RFLP patterns 1 and 2, those of EMRSA-05 to coa RFLP patterns 1, 2, 7 and 8, and those for EMRSA-16 to coa RFLP patterns 2, 3, 4, 5 and 6. The range of patterns within single phage types of S. aureus could help to discriminate between isolates/strains, and in a hierarchical approach coa gene RFLP could occupy an intermediate position between phage typing and pulsed-field gel electrophoresis (PFGE).

Methicillin-resistant Staphylococcus aureus (MRSA) infection in a cystic fibrosis (CF) unit was investigated. Two typing methods, phage-typing and restriction fragment length polymorphism (RFLP) by pulsed-field gel electrophoresis (PFGE) and phylogenetic analysis, showed that nonsocomial transmission of MRSA from the general hospital population had occurred. One instance of possible transmission between two patients was identified. However, transmission between two family members did not occur indicating a minimal risk of MRSA acquisition from social contact compared with hospital admission. This study supports policies for limiting CF-patient admission to hospital but transmission of MRSA does not appear to be a reason for limiting social contact with other CF patients.

Methicillin-resistant Staphylococcus aureus (MRSA) isolates were collected during two eight-month periods in 1991 and 1994, respectively. In order to study the epidemiology, all 74 strains were characterized by phage-typing, antibiotic resistance patterns and DNA-restriction map after cleavage with SmaI enzyme, and pulsed-filed gel electrophoresis (PFGE). These investigations confirmed that MRSA in the hospital, 1991 and 1994, was not due to the spread of one or two clones, but by the simultaneous occurrence of a few well characterized strains and sporadic, occurring strains of different phage-types. Some of these might have developed from the more commonly occurring strains. Isolates from 1994 were more resistant to antibiotics in vitro, than the 1991 isolates. The typing results also indicated that whilst most of the MRSA strains in 1994 were different compared with those of 1991, some of the strains might have been present in both years. The PFGE-typing was more discriminatory and gave a higher typability than the phage-typing, especially among the multiply resistant isolates of MRSA from 1994. Among the less resistant strains the phage-typability was high and with only few exceptions, there was a good correlation between PFGE-type and phage-type.

After years of decline, infections due to Mycobacterium tuberculosis appear to be increasing in the developed world. This has led to a search for improved methods of typing strains in order to answer new questions concerning the epidemiology of tuberculosis. Owing to the phenotypic and genotypic homogeneity of the species, classical fingerprinting methods, including phage typing, serotyping and multilocus enzyme electrophoresis, have proven ineffective. However, new methods based on the analysis of repetitive DNA sequences have been introduced and are now being used to elucidate the emerging pattern of disease.

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection caused by a novel phage-type (now designated EMRSA-16) occurred in three hospitals in East Northamptonshire over a 21-month period (April 1991--December 1992). Four hundred patients were colonized or infected. Seven patients died as a direct result of infection. Chest infections were significantly associated with the outbreak strain when compared with methicillin-sensitive S. aureus. Twenty-seven staff and two relatives who cared for patients were also colonized. A 'search and destroy' strategy, as advocated in the current UK guidelines for control of epidemic MRSA was implemented after detection of the first case. Despite extensive screening of staff and patients and isolation of colonized and infected patients, the outbreak strain spread to all wards of the three hospitals except paediatrics and maternity. A high incidence of throat colonization (51%) was observed. Failure to recognize the importance of this until late in the outbreak contributed to the delay in containing its spread. Key parts of the strategy which eventually contained the local outbreak were the establishment of isolation wards in two hospitals, treatment of all colonized patients and staff to eradicate carriage and screening of all patients upon discharge from wards where MRSA had ever been detected. EMRSA-16 spread to neighbouring hospitals by early 1992 and to London and the South of England by 1993. It is distinguished from other epidemic strains by its characteristic phage-type, antibiogram (susceptibility to tetracycline and resistance to ciprofloxacin), and in the pattern given on pulse field electrophoresis.

This study was undertaken to determine the characteristics of 202 isolates of coagulase-negative staphylococci (CNS) isolated from 78 patients (two-seven per patient) using biochemical identification, bacteriophage susceptibility patterns, reverse-typing, plasmid profiles, antimicrobial susceptibility testing and slime production. All the strains could be typed by using the six markers consecutively. In addition, we have been able to deduce the similarity of 58 strains from 24 patients by means of one marker or another (these are similar or different strains within one patient but not between one patient and another). The use of a combination of markers is the ideal method for typing the strains; thus making it possible to confirm if two or more isolates from the same patient are similar or not and if they produce infection or are simple contaminants.

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA) is an important nosocomial pathogen. A problem encountered in the control of staphylococcal nosocomial infection is the difficulty correlating data available from antimicrobial susceptibility patterns (usually available locally) with phage typing patterns which are generally determined in a reference laboratory. Data problems are exaggerated because many patients have numerous samples taken over long periods of time. This paper describes the use of a database, 'DataEase', on a personal computer to correlate available data with patient demographics and to present the resulting information in whatever format is required. The information might be presented as the phage pattern of each isolate from patients in a particular unit per month or as a combination of the phage types and antimicrobial susceptibility patterns of isolates from a particular unit. The system can be used to generate a list of all isolates for phage typing in a format that allows the phage typing pattern to be recorded directly onto the list worksheet. In addition to providing clinically relevant reports, the system simplifies the collation of epidemiological information, data from which showed that since 1987 the incidence of MRSA has been rising in the group of hospitals served by this laboratory; MRSA of phage type 83A became a problem during 1990 and 1991; the incidence of gentamicin-sensitive phage type non-typable MRSA increased fourfold between 1988 and 1991; and the incidence of gentamicin-resistant MRSA rose sharply in 1992.

Major teaching hospitals in each state of Australia participated in five annual surveys (1986 to 1990) of clinically significant isolates of Staphylococcus aureus . All isolates of methicillin-resistant S. aureus (MRSA) were phage typed with the Basic International Set and an Australian experimental set of typing phages. One or two predominant strains were isolated in individual states during each of the survey periods. Less than 3% (33 of 1243) of MRSA isolates were not typable and more than 86% (1070 of 1243) belonged to strains that were isolated on at least five occasions during a single survey period. Strains of phage types 83A/85/95/90/88//47T/90A/87M/13M and 85/90/88//47T/90A/87A were the most prevalent, but each was identified in only four of the five surveys. Isolates of phage type (83A/85/95) weak/88// 87M persisted throughout the survey period.

The spread of Staphylococcus aureus strains of phage-type 95 was traced retrospectively in Denmark by the review of more than 15,000 S. aureus bacteraemia isolates (1957-88) and from data collected by phage-typing of c. 260,000 isolates from all body sites (1977-89). The first two type 95 strains had been isolated from blood in 1968, and after an interval of 3 years there was a steady increase of bacteraemia strains all over Denmark. From 1977 to 1989 the incidence of type 95 strains among isolates from all body sites increased from 3.8 to 18.8%. Different patterns of increase were recorded in 13 major hospitals and in various clinical departments of two hospitals and these were further analysed. Conjunctival swabs gave the highest percentage of type 95 strains and those from abscesses gave the lowest percentage. Of the type 95 bacteraemia strains 90.4% were resistant to penicillin, but neither methicillin nor gentamicin resistance was recorded.

In an attempt to characterize erythromycin-resistant Staphylococcus aureus we present the intricate relationships between the following factors: phage type, period of isolation, antibiogram, minimum inhibitory concentration (MIC) to erythromycin, inducible or constitutive resistance, spectinomycin susceptibility, hospital- or community-acquired infection, and mortality rate. We studied 718 cases of bacteraemia with erythromycin-resistant S. aureus, occurring between 1959 and 1988. Central factors were phage type pattern, period of isolation, and antibiogram. Between 1959 and 1973 the majority of the erythromycin-resistant strains were multiresistant and belonged to the 83A complex and the related group III. They were mainly inducibly resistant, spectinomycin resistant, and had intermediate MICs (1-4 mg l-1) to erythromycin. The majority of these strains came from hospital-acquired infections and still exist today, although in decreased numbers. By contrast, erythromycin-resistant S. aureus isolated in recent years are usually co-resistant only to penicillin and more rarely also to tetracycline. These strains have inducible resistance, are spectinomycin susceptible, and have a high erythromycin MIC. They are isolated both from hospital- and community-acquired infections. Strains with constitutive resistance to macrolides occurred at a stable low level (13%) during the whole observation period and always had high MICs to erythromycin. The mortality rate among patients with S. aureus bacteraemia due to an erythromycin-resistant strain was only associated with the year of infection and decreased from 61% in the first 15-year period to 40% in the subsequent 15 years.

Klebsiella was first described in 1882 as the causative organism of Friedlander’s pneumonia. Today this form of pneumonia is extremely rare but members of the genus are frequently associated with endemic and epidemic infections in hospitals. Klebsiella is carried in the intestinal tract of 30-40% of humans (Bagley & Seidler, 1977) and is also often isolated from food in hospital kitchens (Cooke et al., 1980) which, when consumed on the ward, may lead to colonization of patients. In the National Survey of Infections in Hospitals, klebsiellae accounted for approximately 5% of all bacterial isolates recovered from 3433 patients and over half of them were isolated from the urinary tract (Marples, Mackintosh & Meers, 1984). Bacteraemia is a common complication of Klebsiella infection in hospital patients and in 1982 accounted for nearly 6% of all bacteraemias reported to the CDSC in the UK (Young, 1982). A n association between ankylosing spondylitis and faecal carriage of Klebsiella spp. has been postulated (Prendergast et al., 1984) and some workers suggest that molecular mimicry between HLA-B27 and klebsiella antigens is involved in the pathogenesis of reactive arthritis (Schwimmbeck, Yu & Oldstone, 1987). A high proportion of strains sent to the Central Public Health Laboratory (CPHL) for typing come from Special Care Baby Units (SCBU) and it has been suggested that this is related to feeding methods (Riser, Noone & Howard, 1980). The extensive use of antibiotics in SCBUs may also contribute to the selection and colonization of the neonatal bowel with Klebsiella. In these units the spread of a single strain may result in serious illness including septicaemia and meningitis (Hill, Hunt & Matsen, 1974).

The heat shock technique (heating a culture at 55 °C for 3 min immediately before phage typing) has been used in our laboratory as an adjunct to routine phage typing for 2 years. This has enabled phage typing patterns to be determined on isolates otherwise recorded as untypable. The method is easily performed and standardized. Phage patterns were found to be reproducible and adequate discrimination was achieved. We found the technique provided significant information which was not available by conventional typing.

We undertook a retrospective, longitudinal survey to monitor the changing incidence, phage types and patterns of antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) in St Laurence's Hospital (SLH), Dublin over the last 10 years. Following a peak in 1979, the incidence of MRSA has gradually decreased to around 17% of S. aureus isolates in 1986, almost identical to its incidence 10 years before. However, the spectrum of antibiotic resistance among these organisms remains broad and this seems to be at least partially related to antibiotic usage. Many strains could not be phage typed and others were typable only by the additional phage 90. This has severely limited the usefulness of phage typing in the tracing of sources of outbreaks. Thus, there is a need for a more specific method of typing as well as a rational antibiotic policy, to successfully monitor and curtail the hospital spread of MRSA.

Strains of coagulase-negative staphylococci and micrococci submitted to a reference laboratory from 137 cases of endocarditis over a 5 year period were reviewed. Staphylococcus epidermidis biotype 1 (SII) was the commonest biotype in all groups of patients but exceeded 80 per cent in the 61 patients who had undergone prosthetic valve surgery and the 16 patients who had undergone other forms of surgery. Biotype 4 (SVI) was recovered from 10 of the 34 patients without surgery. Strains from prosthetic valve endocarditis were frequently resistant to many antibiotics while strains from natural valve endocarditis were frequently sensitive to all, or resistant only to penicillin. The value of bacteriophage typing was confirmed.

Clinical microbiologists normally identify important isolates to the level of species and determine their susceptibility to antibiotics. These activities generate a species identification and provide some differentiation below the level of species in the form of a biotype and an antibiogram. Most other typing methods should be reserved for special studies or to investigate possible infection problems or outbreaks. Specialized techniques should usually be done in reference laboratories. These include serotyping, (complete antigenic analysis), bacteriophage susceptibility, and bacteriocin production or susceptibility.

For over 40 years we have had a means of ‘fingerprinting’ Staphylococcus aureus (Williams, Rippon & Dowsett, 1953). This method, depending on the susceptibility of the organism to bacteriophages, has been invaluable in helping us to understand the organism and more particularly, its epidemiology. This naturally precipitated a considerable interest in the development of suitable techniques for the epidemiological typing of other organisms as they became recognized as causes of hospital-acquired infection, resulting in a proliferation of interested, personnel (Gardner et al., 1962). Infection control teams were established and their demands facilitated the development of typing methods. There is now a wealth of literature concerning typing methods, and those for some important organisms have been reviewed in this journal (Pitt, 1980; Pitt, 1982; Warnock, 1984). Because of the technological revolution it is now possible to examine organisms at the molecular level using simple and rapid techniques which are practicable even in small routine laboratories. Established methods of typing are beginning to appear unattractive either because they are elaborate and time-consuming or because the organisms themselves are changing; e.g. multiply antibiotic-resistant S. aweus (MRSA) strains have been observed to be non-typable with the international set of phages or are typable only with experimental phages (Cafferkey et al., 1983) or react weakly with a few routine phages (Vickery, Beard-Pegler & Stubbs, 1986) resulting in a lack of discrimination. Due to these limitations phage typing of these resistant organism is at best unhelpful. In any case, our increased understanding of the epidemiology of many of the organisms encountered obviates the demand for detailed fingerprinting. The first hint of an outbreak is usually the appearance of an organism from epidemiologically related sources noticed by the clinician, laboratory or infection control team. The organism may be an uncommon species or if it is a commonly occurring hospital pathogen it might be marked by an unusual biotype or characteristic antibiotic susceptibility pattern. This information stimulates infection control investigation, and the machinery in most hospitals nowadays is such that the outbreak may be swiftly controlled. Detailed fingerprinting of the organism may by then be solely of academic interest. For these reasons and because of the severe financial constraints we now face, the motives for devoting precious resources to epidemiological typing should be considered carefully.

Enterobacter spp. are not primary human pathogens; however, like most Enterobacteriaceae they are capable of causing opportunistic infections in hospitalized or debilitated patients. These organisms, especially E. cloacae and E. aerogenes, have an intrinsic resistance to ampicillin and firstgeneration cephalosporins and exhibit a high frequency of mutation to resistance to secondand third-generation cephalosporins. They are likely to become an increasing problem in hospitals as a result of the more frequent use of broad-spectrum beta-lactam antibiotics. Clinical awareness of the potential of Enterobacter strains to cause infection has been reflected in the increasing number of published studies on the genus. Several typing schemes have been described in the last 5 years and we are now in a position to document accurately the hospital epidemiology of some species of the genus. In this article I review the biology, typing and epidemiology of the genus, with particular reference to E. cloacae.