Quantitative microbiology of the scalp in non-dandruff, dandruff, and seborrheic dermatitis.

The composition of the scalp microflora was assessed quantitatively in normal individuals and in patients with dandruff and seborrheic dermatitis, disorders characterized by increasing scaling. Three organisms were constantly found: (1) Pityrosporum, (2) aerobic cocci, and (3) Corynebacterium acnes. Pityrosporum (mainly Pityrosporum ovale) made up 46% of the total microflora in normals, 74% in dandruff, and 83% in seborvheic dermatitis. The geometric mean number of organisms per cm-2 in non-dandruff subjects was 5.04 times 10-5; 9.22 times 10-5 in dandruff subjects; and 6.45 times 10-5 in those with seborrheic dermatitis. The cocci were dominantly Baird-Parker type SII and no quantitative or qualitative change occurred in the scaling disorders. C. acnes comprised 26% of the flora on the normal scalp, 6% in dandruff, and only 1% in seborrheic dermatitis. These results differ significantly from previous reports which describe a much more complex microflora and suggest an etiologic role for microorganisms in dandruff.

Coagulase production by strains of Staphylococcus aureus of differing resistance characters: a comparison of two traditional methods with a latex agglutination system detecting both clumping factor and protein A.

Five groups of strains of Staphylococcus aureus (54 in total) were tested by slide and tube coagulase methods with rabbit and human plasma, and the results were compared with a latex test for both clumping factor and Protein A (Staphaurex, Wellcome Foundation). The five groups comprised: epidemic methicillin resistant S aureus (group 1); other methicillin resistant S aureus (group 2); other resistant S aureus (group 3); other S aureus (group 4); and a group of reference strains, not all true S aureus (group 5). Groups 1, 3, and 4 gave consistently strong positive results with the tube test and the latex test and less strong positive results with the slide test. Group 2 strains sometimes gave weak or negative results in slide and latex tests, but tube tests with both types of plasma were strongly positive. Only within group 5 strains were negative results in the tube test found. Group 1 strains showed no diminution in expression of free coagulase or of clumping factor. The latex test was more sensitive than the slide test but less sensitive than the tube test. Doubtful or negative slide test or latex test results, particularly with strains resistant to methicillin, should be checked by a tube coagulase test.

Evaluation of a micromethod gallery (API Staph) for the identification of staphylococci and micrococci.

A collection of 300 well-characterised strains of staphylococci and micrococci was examined by a commercially available gallery micromethod (API Staph). The results were compared with biotyping by conventional methods. The gallery micromethod broadly agreed with the biotyping scheme used but gave an identification from the index supplied in less than 30% of the trials. Reproducibility was better after 48 h incubation than after 24 h but was poor for the tests for phosphatase and acetoin. When compared with the results of conventional tests, the tests for acetoin, phosphatase and urea were unsatisfactory.

International quality control of phage typing of Staphylococcus aureus. International Union of Microbial Societies Subcommittee.

A questionnaire was sent to the 48 national typing centres for Staphylococcus aureus and 31 replies were received. Methods of phage typing varied and molecular methods were not universally available, although pulsed-field gel electrophoresis was offered by 13 centres. Results for a quality control phage typing exercise were received from 25 centres. Increased standardisation of methods and definitions are indicated. Differences from the consensus patterns were mainly due to typing at an inappropriate dilution of phage, but five strains caused difficulties in many centres. Overall reproducibility was good. Phage typing remains a cost-effective method for epidemiological studies, particularly on a large scale. The strains selected for the quality control exercise included many strains suitable for controlling molecular methods as well as testing phage typing. Molecular methods help in the validation of the conclusions which may be drawn from phage typing.

Changing resistance to antimicrobial drugs, and resistance typing in clinically significant strains of Staphylococcus epidermidis.

Resistance to 11 antimicrobial drugs was assessed in 532 clinically significant strains of Staphylococcus epidermidis received in the years 1978, 1979 and 1980 and compared with that of strains collected in 1976 and 1977 for an international study. Only 14% of strains were sensitive to all the drugs tested. Resistance to gentamicin increased significantly from 7% to 33% during the study period. The degree of association between pairs of drugs was assessed. There was strong association between resistance to methicillin, aminoglycosides and macrolide antibiotics and only weak association between resistance to novobiocin, tetracycline, chloramphenicol and penicillin. Patterns of resistance were complex and may be useful as an accessory typing system.

Micrococcus in the blood.

Eight isolates of micrococci from the bloodstream of six patients obtained under circumstances suggesting a pathogenic role were studied in detail. The organisms were remarkably uniform in cultural, biochemical and antibiotic-susceptibility characters. All strains showed high resistance to methicillin and hydrolysed arginine. The characters found did not correspond with those of any hitherto described species, but were closest to Micrococcus lylae.

Supplementary phages for the investigation of strains of methicillin-resistant Staphylococcus aureus.

Nineteen experimental phages were derived by mitomycin-C induction from methicillin-resistant strains of Staphylococcus aureus collected world-wide. They were assessed for their ability to distinguish isolates of a methicillin-resistant strain of S. aureus epidemic in the London area from other British strains, both sensitive and resistant to methicillin. The experimental phages were most active against strains of phage groups III and I + III. One phage was related to the phages of lytic group I. A typing pattern common to isolates of the epidemic strain was identified and used as an aid in the recognition of this strain. Ten of the phages were retained for further study.

The evaluation of a typing scheme for coagulase-negative staphylococci suitable for epidemiological studies.

A typing scheme was devised for an epidemiological study of infection with coagulase-negative staphylococci in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The scheme was constructed in four stages suitable for the screening of large numbers of isolates: antibiogram, biotype, phage type, and plasmid profile. The discrimination and reproducibility of the scheme was established by the examination of 50 isolates from 33 consecutive episodes of peritonitis affecting 18 patients. The discrimination of the scheme was 76%, with a reproducibility of 86%. Indistinguishable strains occurred in individual patients only, demonstrating that no cross-infection between patients occurred during the 10-month period of collection of strains, and suggesting that the discriminating power of the scheme was, in fact, much higher. The antibiogram, selected as the first stage of the scheme because it was the simplest and cheapest test, proved to be the most discriminatory stage, providing 60% of the final discriminatory power.

Lectin typing of methicillin-resistant Staphylococcus aureus from Singapore, England and Wales, and Denmark.

Methicillin-resistant Staphylococcus aureus (MRSA) isolates from a possible outbreak in Singapore (84) were examined together with all MRSA isolated in Denmark in 1986-1990 (58) and 14 distinct epidemic and 10 distinct single hospital strains from England and Wales. All 84 Singapore isolates were phage typed routinely and 52 isolates were further analysed together with the Danish isolates with an additional set of experimental phages and by lectin typing. The British strains, previously phage typed in the same way, were lectin typed. The following lectins were used: wheat-term agglutinin, soy-bean agglutinin, tomato lectin and Concanavalin-A. Routine phage typing of the Danish isolates showed that 41 isolates belonged to 19 different types; 17 isolates were non-typable (NT). Addition of experimental phage typing and lectin typing enhanced discrimination to 47 types. The 24 British strains could be divided into eight [corrected] "lectin types". Sixty-one of the isolates from Singapore were non-typable by phage typing; the remaining 23 strains belonged to five types. Further examination of 52 isolates with the experimental set of phages and by lectin typing gave 14 closely related types; 48% of these isolates belonged to only two types.

The epidemiology of peritonitis caused by coagulase-negative staphylococci in continuous ambulatory peritoneal dialysis.

The epidemiology of 10 episodes of CAPD peritonitis caused by coagulase-negative staphylococci was studied. The infecting micro-organism was found in prospective skin swabs in six episodes, widely distributed and as the predominant, or equally predominant, organism at each site but was not detected in swabs taken more than 12 weeks before the episode of peritonitis; this suggests recent acquisition. Infecting strains were no more likely to be adherent or to produce slime than non-infecting strains, nor had they any other characteristic detected in our typing scheme that might lead to their detection before peritonitis developed.

Evaluation of electrophoretic methods for typing methicillin-resistant Staphylococcus aureus.

Three electrophoretic methods of typing methicillin-resistant Staphylococcus aureus (MRSA) strains--plasmid profiles (PP), whole-cell protein profiles (WCPP) and immunoblotting profiles (IP)--were evaluated and compared with phage typing. The results obtained with isolates from 12 outbreaks were compared both within the outbreaks, to determine the consistency of results, and between outbreaks. There was generally good agreement between the typing methods but in only six outbreaks did all four methods indicate the same relationship between isolates. WCPP comprised more than 50 bands; when differences occurred, they were seen in only a few bands. In contrast, IP comprised only one or two major bands and the differences were much easier to interpret. The PPs of many of the isolates were similar; many isolates contained a plasmid of mol. wt (18-25) x 10(6). In several outbreaks both WCPP and IP showed minor differences between isolates that were not apparent with phage typing. When comparisons were made between the 12 index strains and an isolate representing the London epidemic MRSA strain, phage typing and WCPP were the most discriminatory methods; both gave nine distinct patterns, whereas there were eight IPs and only six PPs amongst the 13 strains. It was concluded that both WCPP and IP could provide valuable epidemiological data on MRSA and that IP was the easiest of the three methods to interpret.

Evaluation of methods for typing coagulase-negative staphylococci.

One hundred and forty-two coagulase-negative staphylococci (CNS) isolated from dialysate effluent or skin of patients receiving continuous ambulatory peritoneal dialysis (CAPD) were typed by extended antibiogram (16 antibiotics) and biotype (26 reactions). These isolates were then typed by supplementary methods to determine the most suitable typing method for an epidemiological study of antibiotic resistance. These included phage typing, reverse phage typing, plasmid typing, whole-cell protein typing by SDS-PAGE with analysis by densitometry, and immunoblotting. The percentage of isolates typed successfully by the supplementary methods were: phage typing 20%, reverse phage typing 0%, plasmid typing 66%, SDS-PAGE 100%, immunoblotting 100%. The discrimination of each method was: phage typing 20%, plasmid typing 37%, SDS-PAGE 69%, immunoblotting 57%. Reproducibility was 88% for phage typing and 97% for plasmid typing. The reproducibility of the whole-cell protein typing was 83% if the same extracts were used but only 43% when separate protein extracts were analysed on separate occasions. However, strain relatedness was highly reproducible. The determination of an antibiogram-biotype profile was not a sufficiently accurate typing method for an epidemiological study of antibiotic resistance. Whole-cell protein typing by SDS-PAGE or immunoblotting was technically demanding but was the most effective of the supplementary methods for detecting erroneous discrimination and false matching produced by antibiogram-biotype combinations.

The role of typing of coagulase-negative staphylococci in hospital-acquired infection.

Coagulase-negative staphylococcal infections of prosthetic heart valves, orthopaedic implants, shunts for drainage of hydrocephalus and of the peritoneum for dialysis are increasingly diagnosed. The problems of strain characterization are discussed.

A survey of methicillin-resistant Staphylococcus aureus affecting patients in England and Wales.

For a six-month period between October 1987 and March 1988, 660 isolates of methicillin-resistant Staphylococcus aureus (MRSA) from 570 patients were sent to the Staphylococcus Reference Laboratory at Colindale to supplement the National reporting survey of MRSA in England and Wales. The isolates were characterized by phage typing, antibiotic susceptibility and by selected biochemical tests. Patient details were also surveyed. Fourteen strains affected more than one hospital and were called multi-hospital epidemic strains. One strain, EMRSA-1, accounted for more than 40% of isolates and of patients. Other epidemic strains were defined. Ten additional strains were restricted to single hospitals. Only 25 primary isolates were non-typable but 67 sporadic typable strains occurred. The patients affected were approximately equally either infected or colonized. The sexes were represented equally. Orthopaedic and geriatric wards were over-represented. Epidemic strains were clumping factor positive while some sporadic strains were weak producers. Urea alkalinization and protein A production could supplement phage typing and antibiotic resistance in strain recognition.

A major outbreak of methicillin-resistant Staphylococcus aureus caused by a new phage-type (EMRSA-16)

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.

Characters of coagulase-negative staphylococci and micrococci from cases of endocarditis.

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.

Microbiological aspects of the 1980 national prevalence survey of infections in hospitals.

The records of the 1980 national prevalence survey of infection in hospitals were re-assessed from a microbiological point of view. Of 407 records of Escherichia coli, 71 per cent came from the urinary tract while the commonest source of Staphylococcus aureus was from skin infections. These yielded only 41 per cent of the 303 records. Proteus spp. were recorded 166 times, Pseudomonas spp. 115 times and Klebsiella spp. 101 times. These came mainly from the urinary tract but other sources were important. Streptococcus pneumoniae, Haemophilus influenzae, Mycobacterium tuberculosis and the viruses were associated with community infections while E. coli, Proteus spp., Pseudomonas spp., Klebsiella spp., Str. faecalis and non-aureus staphylococci were associated with hospital-acquired infections. The prevalence of bacteraemia was re-assessed.

Surveillance of methicillin-resistant Staphylococcus aureus in England and Wales, 1986-1990.

The incidence of methicillin-resistant Staphylococcus aureus in England and Wales was monitored by a weekly reporting scheme from early 1986 to March 1990. Potential coverage was approximately two-thirds of hospital beds. Reporting centres fell from a peak of 210 in 1986 to a low of 101 centres early in 1989 with later recovery. There were 2367 positive reports in 1986, 2174 in 1987, 1700 in 1988, 1701 in 1989 and 632 in the first quarter of 1990. Colonizations outnumbered infections by 2:1. There were marked regional differences: North-East Thames was dominant in 1986 and 1987, and then declined; South-East Thames showed a dramatic increase in 1988 which continued. Other regions showed less significant changes but there were continuing problems in the South-Western Region and in the West Midlands. Some of these changes were related to the decline of EMRSA-1, possibly due to the introduction of effective control measures, and to the emergence of EMRSA-3 in South-East Thames and its spread to Wessex.

Colonization by gentamicin-resistant Staphylococcus epidermidis in a special care baby unit.

Babies entering a special care baby unit during a 3-month period were studied prospectively for colonization by gentamicin-sensitive and -resistant coagulase-negative staphylococci (CNS). Gentamicin-resistant isolates were characterized by biotyping, antibiotic sensitivity pattern and phage-typing. All the babies studied became colonized with gentamicin-resistant CNS and often with multiple strains. Gentamicin-sensitive CNS usually appeared first and predominated, but gentamicin-resistant staphylococci could be detected by enrichment culture at a median time of 1 day, and, by direct culture at a median time of 4 days. Similar strains were found in the environment and nasal carriage was detected in 60% of the staff of the unit by enrichment culture. The gentamicin-resistant strains were all resistant to benzylpenicillin and other antibiotics. No particular pathogenic strain could be identified, but clusters of colonizations by distinguishable strains were noted. Biotype SVI was frequently encountered, particularly among clinically significant isolates.

A laboratory-confirmed outbreak of rifampicin-methicillin resistant Staphylococcus aureus (RMRSA) in a newborn nursery.

The routine laboratory monitoring of methicillin-resistant strains of Staphylococcus aureus (MRSA) at a large teaching hospital led to the detection of a new, multiply-resistant strain of MRSA, which was resistant not only to penicillin, oxacillin, methicillin, cephamandole, erythromycin, tetracycline, kanamycin and gentamicin but also to rifampicin and sulphamethoxazole-trimethoprim. The rifampicin-methicillin resistant strain of S. aureus (RMRSA) was first detected in blood cultures of babies from the newborn nursery. A bacteriological investigation of the nursery revealed the source to be a paediatric medical officer who was colonised with the resistant strain, and who at the time was receiving rifampicin for pulmonary tuberculosis. The rifampicin resistance was presumably acquired during rifampicin therapy. The outbreak in the nursery was brought to an abrupt end by treatment of the colonised medical officer with mupirocin, applied nasally twice a day for a week, and by the introduction of standard infection-control measures. Reference laboratory assistance was needed to confirm the initial assumption that the outbreak was caused by a single strain.