R.R. Marples

Resistance to methicillin and other antibiotics in isolates of Staphylococcus aureus from blood and cerebrospinal fluid, England and Wales, 1989-95

BACKGROUND Methicillin-resistant Staphylococcus aureus (MRSA) strains are colonising hospital patients in most areas of England and Wales, UK. The extent to which they cause invasive infection can be gauged from their presence in isolates from blood or cerebrospinal fluid. METHODS About 200 clinical laboratories reported the results of susceptibility testing of between 4501 and 6370 isolates of S aureus from blood or cerebrospinal fluid in each of the years 1989-95. We assessed the rate of resistance to methicillin and other antibiotics for each of these years. FINDINGS Resistance to methicillin was stable at about 1.5% of isolates during 1989-91, but increased thereafter to 13.2% in 1995 (p < 0.001). At the same time there was a significant increase in the percentage of isolates resistant to erythromycin, clindamycin, ciprofloxacin, gentamicin, trimethoprim, and rifampicin (p < 0.001 for each)-resistance characteristics often seen in MRSA. Resistance to benzylpenicillin increased slightly but significantly (p < 0.001); resistance to fusidic acid was stable (p > 0.05); resistance to tetracycline decreased significantly (p < 0.001). INTERPRETATION Among cases of S aureus bacteraemia, the proportion due to MRSA has increased significantly. Bacteraemia due to MRSA has a poor prognosis, especially if not treated with suitable antibiotics. Therefore, these findings are important, especially for management of patients and the development of antibiotic policies.

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.

Current problems with methicillin-resistant Staphylococcus aureus

A meeting organized jointly by the Association of Medical Microbiologists and the Public Health Laboratory Service was held at the Central Public Health Laboratory (CPHL) on 10 April 1987 to discuss methicillin-resistant Staphylococcus aureus (MRSA). The morning was devoted to the international aspects of the problem with formal presentations describing the characters of MRSA worldwide, in France, in Australia and in England and Wales. In the afternoon attention focused on the local problems posed by the epidemic MRSA, (EMRSA-l), found in the London and South-East areas of England.

Bacteriological characters of strains of Staphylococcus aureus submitted to a reference laboratory related to methicillin resistance.

Methicillin-resistant Staphylococcus aureus (MRSA) strains present an increasing clinical problem. Analysis of 2679 strains submitted to a reference laboratory in the first quarter of 1983 and 3050 strains submitted in summer 1984 showed 479 and 593 multi-resistant strains. The proportion of methicillin-resistant strains classified as epidemic rose from 5.9 to 10.2%. Other methicillin-resistant strains continued to occur but other methicillin-sensitive multi-resistant strains appeared to fall. A strain with defined characters could be recognized in the Thames regions.

Beta-lactamase-negative, methicillin-resistant Staphylococcus aureus in a newborn nursery: report of an outbreak and laboratory investigations

An outbreak of skin infection caused by a beta-lactamase-negative strain of methicillin-resistant Staphylococcus aureus (MRSA) occurred during a five-week period in a newborn nursery. Twelve babies, two mothers and two members of staff were involved. One baby had a diagnosis of staphylococcal scalded skin syndrome and two others required treatment with antibiotics. The infecting strain produced exfoliative toxin A. It was thought that it had been introduced from a different maternity unit by a nasal carrier. Laboratory investigations tended to support this hypothesis.

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.

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.

Sex, constancy, and skin bacteria

SummaryQuantitative studies of the aerobic flora of seven skin sites in 16 volunteers were repeated after 3 months. The total aerobic densities of the sites differed, male carried more organisms than females and also more biotypes. Qualitative differences in the flora could be detected.ZusammenfassungDie aerobe Bakterienflora der Haut wurde quantitativ an sieben verschiedenen Hautregionen bei 16 Probanden im Abstand von 3 Monaten untersucht. Die Gesamtbakterienzahl war in den einzelnen Regionen unterschiedlich; Männer wiesen mehr Bakterien als Frauen und auch mehr Bakterientypen auf. Auch qualitative Unterschiede der Bakterienflora waren feststellbar.

International collaborative evaluation of the ATB 32 staph gallery for identification of the Staphylococcus species.

This international collaborative study evaluates a new system (ATB 32 Staph) for the identification of staphylococci taking into account the new novobiocin-sensitive and -resistant species reported. This study involved eight laboratories and 792 strains were tested. The reproducibility obtained for the cumulative results of the inter- and intra-laboratory tests was more than 90%. For 713 strains relevant of a species 95.5% were correctly identified by the system. Eight strains (1.2%) were misidentified and 24 strains (3.3%) were not identified. For 79 strains initially considered as not-classified, 62% were identified at the species level by the new system. The newer ATB 32 Staph gallery is a performant and useful method for routine identification of the currently described staphylococci species from clinical and animal origin.

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.