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

Methicillin-resistant Staphylococcus aureus: an evolving pathogen

The horizontal transmission of methicillin resistance to Staphylococcus aureus (MRSA) in hospital and community settings, and growing prevalence of these strains, presents a significant clinical challenge to the management of serious infections worldwide. While infection control initiatives have stemmed the rising prevalence, MRSA remains a significant pathogen. More recently, evidence that MRSA is becoming resistant to glycopeptides and newer therapies raises concern about the use of these therapies in clinical practice. Vancomycin resistance has become evident in select clinical settings through rising MICs, growing awareness of heteroresistance, and emergence of intermediate-resistant and fully resistant strains. While resistance to linezolid and daptomycin remains low overall, point mutations leading to resistance have been described for linezolid, and horizontal transmission of cfr-mediated resistance to linezolid has been reported in clinical isolates. These resistance trends for newer therapies highlight the ongoing need for new and more potent antimicrobial therapies.

Surveillance and control of methicillin-resistant Staphylococcus aureus infections in French hospitals

OBJECTIVE

To assess the way French hospitals conduct surveillance for, and control infections caused by, methicillin-resistant Staphylococcus aureus (MRSA), and to evaluate the incidence of these infections.

DESIGN

Retrospective analysis of sample surveillance data.

SETTING

Representative sample of French hospitals.

PARTICIPANTS

Representative sample of 38 French public hospitals.

METHODS

Hospitals were selected randomly in 1996, taking into account their location and number of beds. Administrative data, surveillance denominators used, antimicrobial resistance rates, and infection control practices were analyzed for the period 1990 to 1995. The same 38 centers were contacted 3 years later, in 1998, to reassess their surveillance and control activities.

RESULTS

French hospitals were slow to implement MRSA surveillance programs; only 5% had such programs in 1990, when the median incidence per admission (0.37%) and per patient-days (0.04%) of MRSA infections was already high. Despite the implementation of surveillance programs in 66% of French hospitals in 1995 and 87% in 1998, the MRSA infection rates remained stable from 1990 to 1995 and increased from 1995 to 1998. The proportion of French hospitals having a policy for the transfer of MRSA-infected patients to other hospitals increased from 47% in 1995 to 61% in 1998, whereas screening for MRSA colonization (42%-53%) and isolation for colonized or infected patients (87%-89%) remained stable.

CONCLUSIONS

This first national survey showed that French hospitals probably were not optimally prepared to control and prevent MRSA infections, since they were slow to respond to the growing problem.

Antibiotic resistance among clinically important gram-positive bacteria in the UK

The resistance of bacteria to antibiotics, particularly those used for first-line therapy, is an increasing cause for concern. In the UK, the prevalence of resistance to methicillin and mupirocin in Staphylococcus aureus, and to penicillin and macrolides in Streptococcus pneumoniae, appear to be increasing. There has also been an increase in the number of hospitals where glycopeptide-resistant enterococci are known to have been isolated. The increases in methicillin-resistant S. aureus and glycopeptide-resistant enterococci are due, in part, to the inter-hospital spread of epidemic strains. Although new quinolones and streptogramins with activity against Gram-positive bacteria (including strains resistant to currently available agents) are under development, there is no reason to believe that resistance to these agents will not emerge. The control of resistance in Gram-positive bacteria will require a multi-faceted approach, including continued and improved surveillance, a reduction in the unnecessary use of antibiotics, and the application of other strategies such as vaccination.

Trying to control MRSA causes more problems than it solves

Despite occasional reports of local success, the steadily increasing prevalence of strains of Staphylococcus aureus resistant to methicillin (MRSA) shows that attempts to limit their spread do not work. In this commentary we suggest that efforts to control the spread of methicillin-resistance are counterproductive, and that energies should instead be directed towards the control of outbreaks of disease and preventing the emergence of antibiotic resistance.

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.

Methicillin-resistant Staphylococcus aureus in wound care

A discussion detailing the development of antibiotic-resistant strains of Staphylococcus aureus and offering guidelines for infection control procedures.

Methicillin-resistant Staphylococcus aureus (MRSA) isolated in clinics and hospitals in the Fukuoka city area

Bacteriological and clinical studies were carried out on 280 strains of Staphylococcus aureus isolated in clinics and hospitals in the Fukuoka city area from September 1990 to March 1991. The percentage of methicillin-resistant S. aureus (MRSA) strains studied was 41.4% (116 of 280). Of 116 MRSA strains, 48 (41.3%) produced coagulase VII and 21 (18.1%) produced coagulase II. The mean age of the patients who harboured MRSA, 70.5 +/- 16.9 years, was significantly higher than that of patients with methicillin-sensitive S. aureus (MSSA), 44.2 +/- 29.3 years (P < 0.001). MRSA was detected more frequently than MSSA in sputum (P < 0.01), while MSSA was detected more frequently than MRSA in pus (P < 0.01). Ninety (89.1%) of 101 strains of MRSA were isolated from inpatients and 98 (71.0%) of 130 strains of MSSA were isolated from outpatients. Similar number of MRSA strains were recovered in a variety of hospitals, indicating that there was no relationship between hospital size (number of beds) and the incidence of MRSA. As for drug susceptibility, coagulase VII-producing MRSA strains were more sensitive to clidamycin (P < 0.01) and more resistant to minocycline (P < 0.01) than were other MRSA strains.

Methicillin-resistant Staphylococcus aureus: do we just have to live with it?

Infection with methicillin-resistant Staphylococcus aureus is a familiar problem in hospital patients and has been a global issue since the 1960s. Control of this organism is expensive both financially and in terms of human resources. This article is an attempt to review the epidemiological evolution and our understanding of the organism and bring together possible solutions.

Methicillin-resistant Staphylococcus aureus in Europe

In order to obtain pan-European data on methicillin-resistant Staphylococcus aureus (MRSA), 43 laboratories from ten European countries each screened 200 consecutive Staphylococcus aureus isolates for methicillin resistance. Only one isolate per patient was permitted. All participants used a uniform oxacillin-supplemented screening plate. MRSA isolates were sent to Munich for reconfirmation and further susceptibility testing. Phage typing of the MRSA strains was performed in Denmark. Of the 7,333 Staphylococcus aureus strains screened, 936 (12.8%) were methicillin resistant. The proportion of MRSA in the various European countries ranged from < 1% in Scandinavia to > 30% in Spain, France and Italy. Rates of resistance to the non-glycopeptide antibiotics were lowest for rifampin and highest for ciprofloxacin. Sixty percent of the methicillin-resistant strains originated from patients in surgical and medical departments, with wounds being the most common isolation source. MRSA was found more frequently in intensive care patients. Only 13% of the strains were non-typable, and 76% of the isolates belonged to phage group III. For each area phage typing detected one or a few dominating (epidemic) types, but 46% of the strains did not belong to these types; the MRSA population is thus a mixture of epidemic and non-epidemic strains. MRSA seems to be a growing problem, especially in southern Europe, where incidence and rates of antibiotic resistance are alarmingly high.

Characterization of a strain of methicillin-resistant Staphylococcus aureus (EMRSA-15) by conventional and molecular methods

A strain of methicillin-resistant Staphylococcus aureus (MRSA), EMRSA-15, was isolated in both the Midlands and south-east of England. This strain could be distinguished from another, very similar strain, found in the north of England, by both conventional and molecular typing. Conventional typing allowed distinction between the Midlands and southern variants of EMRSA-15, while molecular typing (pulse-field gel electrophoresis) allowed recognition of local variants in the south. In this investigation conventional and molecular typing methods were complementary.

Methicillin resistant Staphylococcus aureus in three adjacent health districts of south-east England 1986-91

The experiences with methicillin-resistant Staphylococcus aureus (MRSA) of two contiguous Health Districts during 1986-91 and of a third mutually adjacent District in south-east England during 1989-91 were compared. Although the three Districts were in many ways similar, the nature of the problems posed by MRSA differed. The Districts had dealt with MRSA independently but had evolved similar strategies for coping with the organism. In two Districts a gradual relaxation of case-finding and of infection control precautions applied to individual patients and outbreaks, was followed by a reduction in the number of new patient-isolates identified from routine bacteriology specimens. Standardization of MRSA isolation rates for patient throughput and for length of hospital stay showed the examination of crude total isolates to provide misleading comparisons of relative risks of acquiring MRSA in different specialties. It was also found that patients discharged from specialties with short inpatient stays were more likely to have MRSA detected after discharge by their physicians working in the local community served by the hospitals but there was no evidence of spread outside hospital. It is suggested that good all-round standards of infection control practice are more important than specific radical policies in dealing with endemic MRSA.