Multi-resistant Staphylococcus aureus--a suitable case for inactivity?

Should We Vigorously Try to Contain and Control Methicillin-Resistant Staphylococcus aureus?

Objective:

To review practices currently used to control transmission of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, determine the frequency of their use, and discuss the indications for implementing such measures.

Design:

A questionnaire survey to determine how commonly selected control practices are used, and a literature review of the efficacy of control practices.

Participants:

Two hundred fifty-six of 360 hospital-based members fo the Society for Hospital Epidemiology of America, Inc. (SHEA) completed the survey questionnaire.

Result:

Many different combinations of surveillance and control measures are used by hospitals with MRSA. Nine percent of hospitals stated that no special measures were used to control MRSA. The efficacy of commonly used control measures has not been established by controlled trials.

Conclusions:

Implementing control measures is warranted when MRSA causes a high incidence of serious nosocomial infections, and is desirable when MRSA has been newly introduced into a hospital or into an intensive care unit, or when MRSA accounts for more than 10% of nosocomial staphylococcal isolates. While the value of some practices is well established, measures such as routinely attempting to eradicate carriage of MRSA by colonized patients and personnel require further evaluation.

The uses and abuses of rapid bioluminescence-based ATP assays

Bioluminescence-based ATP testing of solid surfaces has become well established in the food processing industry as part of general hazard analysis and critical control points (HACCP) measures. The rise in healthcare associated infections (HAIs) at the turn of the century focussed attention on the environment as a potential reservoir of the agents responsible for such infections. In response to the need for objective methods of assessing the efficiency of cleaning in healthcare establishments and for rapid methods for detecting the presence of the pathogens responsible for HAIs, it was proposed that ATP testing of environmental surfaces be introduced. We examine the basis behind the assumptions inherent in these proposals. Intracellular ATP levels are shown to vary between microbial taxa and according to environmental conditions. Good correlations between microbial numbers and ATP levels have been obtained under certain specific conditions, but never within healthcare settings. Notwithstanding, ATP testing may still have a role in providing reassurance that cleaning regimes are being carried out satisfactorily. However, ATP results should not be interpreted as surrogate indicators for the presence of microbial pathogens.

Methicillin-resistant Staphylococcus aureus: A public health issue with economic consequences

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has become endemic worldwide in hospitals, and community-associated MRSA is spreading into the community at large.

OBJECTIVES

To estimate the current cost of MRSA in Canada and to assess the magnitude of this public health issue.

METHODS

An extensive review of the literature was conducted to gather epidemiology, health care resource utilization and cost data for MRSA in Canadian settings. The current MRSA burden was estimated using available cost data and the most recent epidemiology data.

RESULTS

The rate of MRSA in Canadian hospitals increased from 0.46 to 5.90 per 1000 admissions between 1995 and 2004, while community-associated MRSA continued to spread into the community. Patients harbouring MRSA required prolonged hospitalization (average 26 days of isolation per patient), special control measures, expensive treatments and extensive surveillance. Total cost per infected MRSA patient averaged $12,216, with hospitalization being the major cost driver (81%), followed by barrier precautions (13%), antimicrobial therapy (4%) and laboratory investigations (2%). The most recent epidemiological data, combined with available cost data, suggest that direct health care cost attributable to MRSA in Canada, including cost for management of MRSA-infected and-colonized patients and MRSA infrastructure, averaged $82 million in 2004 and could reach $129 million in 2010.

CONCLUSION

MRSA is a costly public health issue that needs to be tackled if the growing burden of this disease in Canadian hospitals and in the community is to be limited.

Costs of hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) and its control

For most countries badly affected by methicillin-resistant Staphylococcus aureus (MRSA) there have been many years of debate about its relative virulence compared with methicillin-susceptible S. aureus (MSSA) and whether it could be controlled. Now that it is endemic in the majority of hospitals around the world, it is clear that it is at least as virulent as MSSA and is an additional burden of healthcare-acquired infection. There is increasing evidence that, despite this endemicity, control efforts can be successful, although they are often perceived as expensive. In reality, there is a large body of consistent evidence that control is highly cost effective, particularly in the context of the huge societal costs of MRSA and the future ever-greater threats that it poses.

Antimicrobial resistance in clinical isolates of Staphylococcus aureus from hospital and community sources in southern Jamaica

OBJECTIVES

In this study, we assessed the antimicrobial susceptibility patterns and prevalence of methicillin resistance among Staphylococcus aureus isolates from hospital and community sources in southern Jamaica.

METHODS

Eighty isolates of S. aureus obtained from hospital and community-based patients with staphylococcal infections were collected, and antimicrobial susceptibilities were determined by disk diffusion.

RESULTS

While all specimens yielded isolates, multidrug-resistant isolates were obtained only from urine, high vaginal swab, abscess aspirate, and catheter tip samples. The overall prevalence of methicillin-resistant S. aureus (MRSA) was 23%. The proportions of MRSA isolated from hospital sources (18/39) and community sources were 46% and 0%, respectively (p<0.05). The pattern of antibiotic susceptibility of S. aureus differed significantly between MRSA and methicillin-susceptible (MSSA) isolates. For MRSA isolates, multiple-drug resistance was common and only few antibiotics were active against these isolates. However, no MRSA was resistant to vancomycin. Except for penicillin and to some extent co-trimoxazole (trimethoprim-sulfamethoxazole), most MSSA isolates were susceptible to nearly all antimicrobial agents used in this study.

CONCLUSIONS

This is the first report of MRSA from this region of Jamaica. Because methicillin resistance is associated with multiple-drug resistance in S. aureus, it is imperative that surveillance initiatives be focused on both the hospital and community in order to monitor and limit the spread of this organism.

Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities

Meticillin-resistant Staphylococcus aureus (MRSA) remains endemic in many UK hospitals. Specific guidelines for control and prevention are justified because MRSA causes serious illness and results in significant additional healthcare costs. Guidelines were drafted by a multi-disciplinary group and these have been finalised following extensive consultation. The recommendations have been graded according to the strength of evidence. Surveillance of MRSA should be undertaken in a systematic way and should be fed back routinely to healthcare staff. The inappropriate or unnecessary use of antibiotics should be avoided, and this will also reduce the likelihood of the emergence and spread of strains with reduced susceptibility to glycopeptides, i.e. vancomycin-intermediate S. aureus/glycopeptide-intermediate S. aureus (VISA/GISA) and vancomycin-resistant S. aureus (VRSA). Screening for MRSA carriage in selected patients and clinical areas should be performed according to locally agreed criteria based upon assessment of the risks and consequences of transmission and infection. Nasal and skin decolonization should be considered in certain categories of patients. The general principles of infection control should be adopted for patients with MRSA, including patient isolation and the appropriate cleaning and decontamination of clinical areas. Inadequate staffing, especially amongst nurses, contributes to the increased prevalence of MRSA. Laboratories should notify the relevant national authorities if VISA/GISA or VRSA isolates are identified.

MRSA-retrospective analysis of an outbreak in the burn centre Aachen

The growing interest in methicillin-resistant Staphylococcus aureus (MRSA) has been caused by its increased appearance in hospital and community populations. In our burn centre, an outbreak of MRSA was noticed during an 8-month period. We were able to isolate MRSA in eight patients. DNA analysis by pulsed-field gel electrophoresis (PFGE) demonstrated the development of five different strains during this period. Only two patients developed an infection caused by MRSA colonisation. The infections were proven by positive blood culture or catheter colonisation. One patient developed a clinical vancomycin-resistant sepsis which was treated successfully with the additional application of Quinupristin/Dalfopristin. THIS ANALYSIS SHOWS THAT: (1) the development of MRSA in a burn unit is often created in a single patient by long-term antibiotic therapy and not a result of cross-infection, (2) manifest MRSA infection seldom occurs even in colonised burn patients, and (3) a clinically vancomycin-resistant MRSA infection in burn patients can be treated sufficiently with Quinupristin/Dalfopristin.

Cost-effectiveness of active surveillance cultures and contact/droplet precautions for control of methicillin-resistant Staphylococcus aureus

Some have reported that adopting Centers for Disease Control and Prevention guidelines requiring contact precautions for methicillin-resistant Staphylococcus aureus (MRSA) had no impact on rates of nosocomial spread or infection, and may therefore waste money. The objective of the present study was to evaluate the cost-effectiveness of active surveillance cultures and barrier precautions for controlling MRSA. Estimated costs of surveillance cultures and isolation measures used during an MRSA outbreak at this hospital were compared with the estimated attributable excess costs of methicillin resistance (i.e., the difference between MRSA and methicillin-sensitive S. aureus costs) for bacteraemias occurring during an MRSA outbreak not promptly controlled at another hospital. The study was set in the neonatal intensive care units of two tertiary care hospitals. Estimated costs of controlling the 10.5-month outbreak in this neonatal intensive care unit that resulted in 18 colonized and four infected infants ranged from $48 617 to $68 637. The estimated attributable excess cost of 75 MRSA bacteraemias in a second neonatal intensive care unit outbreak that resulted in 14 deaths and lasted 51 months was $1 306 600. Weekly active surveillance cultures and isolation of patients with MRSA halted an outbreak at this hospital, and cost 19- to 27-fold less than the attributable costs of MRSA bacteraemias in another outbreak that was not promptly controlled. The costs of infections at other body sites and the human cost of deaths from infection were not estimated but would further help to justify the cost of identifying colonized patients and implementing effective preventive measures.

Screening for methicillin-resistant Staphylococcus aureus in the endemic hospital: what have we learned?

Control of methicillin-resistant Staphylococcus aureus (MRSA) still generates controversy among infection control practitioners. Opponents claim that once MRSA becomes endemic in an institution, control efforts are no longer justified. This review examines the usefulness, feasibility and cost-effectiveness of control programmes in acute-care hospitals where eradication of MRSA has either failed or has never been attempted; hence, the pathogen has become endemic. High endemicity is associated with increased hospital-acquired infection rates, increased use of glycopeptides and subsequent risk of emergence of antibiotic-resistant Gram-positive bacteria, and additional healthcare costs. Thus, MRSA control has many advantages. Indeed, in many institutions the actual benefit of containment efforts was manifested through the resultant decrease in the incidence of hospital-acquired MRSA infections. Successful programmes are based on an early identification of the MRSA reservoir and prompt implementation of contact precautions. The most efficacious strategy to detect occult MRSA carriage is via the screening of high-risk patients on admission to the hospital which has proven to be cost-effective in varied acute-care endemic settings.

Tea tree oil as an alternative topical decolonization agent for methicillin-resistant Staphylococcus aureus

The combination of a 4% tea tree oil nasal ointment and 5% tea tree oil body wash was compared with a standard 2% mupirocin nasal ointment and triclosan body wash for the eradication of methicillin-resistant Staphylococcus aureus carriage. The tea tree oil combination appeared to perform better than the standard combination, although the difference was not statistically significant due to the small number of patients.

Antibiotic resistance in staphylococci

When penicillin was introduced in 1944 over 94% of Staphylococcus aureus isolates were susceptible; by 1950 half were resistant. By 1960 many hospitals had outbreaks of virulent multi-resistant S. aureus. These were overcome with penicillinase-stable penicillins, but victory was brief; methicillin-resistant S. aureus (MRSA) were recorded in the year of the drug's launch. MRSA owe their behaviour to an additional, penicillin-resistant peptidoglycan transpeptidase, PBP-2', encoded by mecA. Their spread is clonal, with transfer of mecA being extremely rare. MRSA accumulated and then declined in the 1960s and 1970s, but became re-established in the early 1980s. Some early MRSA strains were colonists rather than invaders and the proportion of MRSA among S. aureus bacteraemias in England remained under 3% until 1992. However, this proportion rose to 34-37% by 1998-1999, reflecting the dissemination of two new epidemic strains, EMRSA 15 and 16. These may be more virulent than earlier MRSA, or their success may reflect changing hospital practice. Until 1996, glycopeptides were universally active against S. aureus; then glycopeptide-intermediate S. aureus (GISA) were found in Japan, France, and the USA. This resistance is associated with increased wall synthesis. Coagulase-negative staphylococci (CNS) are less pathogenic than S. aureus but are important in line-associated bacteraemias and prosthetic device infections. They are even more often resistant than S. aureus, notably to teicoplanin. Few anti-staphylococcal agents were launched from 1970 to 1995, but the situation is now improving. Dalfopristin/quinupristin inhibits virtually all S. aureus, although its bactericidal activity is impaired against strains with constitutive MLSB-type resistance; other new agents are in advanced development. New agents give a renewed opportunity for control, but S. aureus is a resilient foe, able to regain its importance if drugs are used profligately or if hygiene is slackened.

Tracing the spread of methicillin-resistant Staphylococcus aureus by Southern blot hybridization using gene-specific probes of mec and Tn554

In a community hospital in Brooklyn, New York, over a 3-year period, 79 methicillin-resistant Staphylococcus aureus (MRSA) isolates from five different case clusters were subtyped by Southern blot hybridization with two previously characterized gene probes, mec and Tn554. Together, the genotyping enabled the hospital infection control team to differentiate simultaneous MRSA clusters in the surgical intensive care unit (type I:A) and the open heart unit (type II:J), document the spread of one strain (type I:A) between roommates, identify an endemic strain (type II:J) from cardiac monitors and medical personnel, and identify an unrelated outbreak strain (type II:NH) in the labor and delivery unit. On the basis of this investigation it is clear that the routine DNA fingerprinting of MRSA in health care facilities, to monitor their spread and identify cases of nosocomial infections, is an important infection control measure.

Pathogenic significance of methicillin resistance for patients with Staphylococcus aureus bacteremia

To assess whether methicillin resistance is a microbial characteristic associated with deleterious clinical outcome, we performed a cohort study on 908 consecutive episodes of Staphylococcus aureus bacteremia and a case-control study involving 163 pairs of patients matched for preexisting comorbidities, prognosis of the underlying disease, length of hospitalization, and age. Of 908 bacteremic episodes, 225 (24.8%) were due to methicillin-resistant S. aureus (MRSA). Multivariate analysis did not reveal that methicillin resistance was an independent predictor for mortality when shock, source of bacteremia, presence of an ultimately or rapidly fatal underlying disease, acquisition of the infection in an intensive care unit (ICU), inappropriate empirical therapy, female sex, and age were taken into account. Nonetheless, methicillin resistance was an independent predictor for shock. The case-control study could not confirm that shock was linked to MRSA when prior antimicrobial therapy, inappropriate treatment, ICU residence, and female sex were considered. Our data suggest that cohort studies tend to magnify the relationship of MRSA with clinical markers of microbial pathogenicity and that this effect is a shortcoming of these kind of studies that is caused by inadequate control for underlying diseases.

Methicillin-resistant Staphylococcus aureus in burns patients--why all the fuss?

Procedures designed to limit spread of methicillin-resistant Staphylococcus aureus (MRSA) in burns units demand time and resources. To assess the significance of MRSA in burns patients we performed a retrospective review of MRSA colonization in in-patients over a 41-month period at the North Trent Sub-regional Burns Unit. Patients were compared with MRSA free controls, matched for age and percentage body surface area (BSA) burn and admitted during the same time period. Length of stay, number of operations and deaths were outcome indicators. All patients managed non-operatively were excluded, leaving 40 MRSA patients and 46 controls. There was no statistical difference between the two groups with regard to number of operations (p= 0.07), duration of admission (p = 0.12) or mortality (p = 0.09). Of the control group, 83% had wound swabs positive for methicillin-sensitive Staphylococcus aureus (MSSA). there was no statistical difference in any outcome variables between this sub-group of controls and MRSA patients. Colonization with S. aureus (both MRSA and MSSA) was associated with larger burns (p<0.05), twice as many operative procedures (p<0.05) and prolonged admissions (p<0.01). Mortality was unaltered by staphylococcal colonization (p = 0.8). Although our study lacks power, we would suggest that methicillin resistance per se is not associated with increased morbidity or mortality in burns patients.

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.

Methicillin-resistant Staphylococcus aureus versus the burn patient

Methicillin-resistant Staphylococcus aureus (MRSA) has become a frequent cause of nosocomial infection, its increasing prevalence posing serious therapeutic and infection control problems within the hospital environment. MRSA is a major challenge to the burn patient, with potential to cause significant morbidity and mortality. Burn patients have been shown to become colonised and infected more readily than other patient groups. Extensive burn injuries are particularly susceptible to infection as a result of the disruption of the normal skin barrier and accompanying depression of immune responses. Extended hospitalisation and antibiotic therapy have been identified as additional risk factors for MRSA carriage and infection. Microbial surveillance, epidemiological studies and the introduction of strict infection control regimes can reduce the prevalence of MRSA but may be insufficient for eradication or prevention of outbreak situations. Recognition of the clinical importance of MRSA to the burn patient highlights the need to take appropriate measures to minimise transmission and infection in this vulnerable group of patients.

Enterotoxin and toxic shock syndrome toxin-1 production of methicillin resistant and methicillin sensitive Staphylococcus aureus strains

In this study the production of enterotoxin A-D and toxic shock syndrome toxin-1 (TSST-1) of 181 methicillin resistant (MRSA) and 100 methicillin sensitive (MSSA) Staphylococcus aureus first isolates from different patients was investigated. All the MRSA- and MSSA isolates in the study were collected in a period between 1993 and 1995 from specimens sent from 11 different acute care hospitals in the greater Düsseldorf area. As far as possible the isolates were matched according to ward and hospital. The isolates were collected in the same time period and matched for specimen from which isolated. Furthermore, only first isolates were analysed in both groups. No significant difference in the production of toxin of any type between MRSA and MSSA could be detected (51 and 40% respectively). When the individual toxins were analysed, again no significant difference between MRSA and MSSA was demonstrable (enterotoxin production by MRSA 40% and MSSA 36%, and TSST-1 16% and 8% respectively). Despite this, a slight tendency for MRSA to produce enterotoxin A and B and for MSSA to produce enterotoxin C was observed. In addition, generation of TSST-1 by both groups was independent of enterotoxin A-D production. Interestingly, no increase in the proportion of TSST-1- or enterotoxin-producing MRSA and MSSA isolates was observed in strains isolated from blood cultures from patients with a clinical diagnosis of sepsis. Genotypical pulsed-field-gel-electrophoresis (PFGE) and phenotypical (bacteriophage typing, lysotyping) characterization of the 181 MRSA isolates resulted in 28 different PFGE patterns (of which 19 were toxin producers) and 22 lysotyping groups (18 of which produced toxin). In summary, the investigated clinical S. aureus isolates showed no difference in their ability to produce toxin and this was independent of their sensitivity to methicillin.

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.

Rapid genotypic confirmation of methicillin resistance

Detection of phenotypic methicillin resistance in Staphylococcus aureus clinical strains by conventional disk diffusion testing is fraught with problems. We used gene amplification of the mecA locus by polymerase chain reaction (PCR), in conjunction with a capillary/air thermal cycler, to overcome both the inaccuracy of phenotypic methods and the lengthy processing times required for previous genotypic methods. The rapid PCR method correctly identified methicillin resistance in a consecutive series of 30 S. aureus isolates when compared with routine and reference phenotypic methods. The shorter processing time and smaller reagent volumes required for the air thermal cycler make same-day determination of methicillin resistance in clinical isolates feasible for diagnostic laboratories.

New threats to the control of methicillin-resistant Staphylococcus aureus

Several countries have achieved considerable success in the control of epidemic methicillin-resistant Staphylococcus aureus (MRSA). However, in several hospitals in the UK, MRSA strains of enhanced epidemicity, notably EMRSA-16, are becoming endemic. Our inability to eliminate the cause of a single-strain outbreak is unfamiliar and unnerving. Factors in 'market-led' health care delivery that hinder control of MRSA include a shortage of inpatient beds, patients moving from ward to ward, and more mixed-specialty wards. Increasing use of day treatments leaves an inpatient hospital population with more risk factors for infection. Early discharge of infected patients to convalescent homes, or to homes for the elderly, has created a new reservoir of infected and colonized patients. The emergence of high-level mupirocin resistance may soon also contribute to failure of control. The transfer of vancomycin resistance from Enterococcus faecium to a laboratory strain of S. aureus suggests that, especially in hospitals with both vancomycin-resistant enterococci and MRSA, there is the opportunity for the emergence of vancomycin-resistant MRSA for which there may be no effective antimicrobial prophylaxis or treatment. It is increasingly important to persuade hospital managers that even partial control of MRSA, whilst expensive, is still cost-effective and is a quality issue for individual hospitals. The control of EMRSA-16 in one hospital has recently been estimated to have saved more than 629,000 pounds extra costs. MRSA continues to be at the forefront of those organisms that seriously challenge modern technological medicine and surgery.

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.

Staphylococcus aureus: a review of the literature

Staphylococcus aureus has a long association with nosocomial infection. Problems date from the 1950s, although methicillin-resistant Staphylococcus aureus (MRSA) did not emerge until the following decade. Initially the pathogenicity of antibiotic-resistant strains was underestimated, and is still sometimes questioned, but today most authorities consider MRSA a serious threat, especially given current preoccupation with cost-effectiveness within the health service: nosocomial infection is associated with increased expenditure and may be regarded as a hallmark of indifferent nursing and medical care. This review documents the emergence of MRSA and recognition of the ensuing problems throughout the 1980s and early 1990s, with suggestions for nursing activities which could contribute towards improved control. Lessons learnt during outbreaks are seen to be of value, but there is also a need for staff at ward level to review routine practice continually so that awareness of activities likely to result in cross-infection is maintained. The use of protective clothing emerges as less important than handwashing, which may be periodically audited to maintain standards.

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: the scale of the problem in a Shri Lankan hospital

A three month surveillance study of methicillin resistant Staphylococcus aureus (MRSA) was carried out in the male surgical unit of the General Hospital, Peradeniya, Shri Lanka. Nose, throat, axillary, perineal and wound swabs were taken from 251 patients and 35 staff members. Eighty-four (27.5%) of 305 isolates of S. aureus from patients were MRSA. Seventy-three of these isolates were also resistant to penicillin, tetracycline, erythromycin, gentamicin, chloramphenicol and co-trimoxazole. All isolates were sensitive to fusidic acid, clindamycin, vancomycin and rifampicin. The acquisition of MRSA was higher than of methicillin sensitive S. aureus (MRSA). No deaths occurred due to MRSA. Staff carriage was only 6%. The treatment and management of MRSA in hospitals with very poor resources requires further study of interventions which are practicable in this situation.

National survey of methicillin-resistant Staphylococcus aureus in Belgian hospitals: detection methods, prevalence trends and infection control measures. The Groupement pour le Dépistage, l'Etude et la Prévention des Infections Hospitalières

A questionnaire survey of Belgian acute care hospitals was conducted to determine the methods used for detection of methicillin-resistant Staphylococcus aureus (MRSA), to estimate the prevalence of this organism during the period 1989-1991 and to describe the infection control measures used locally for limiting its spread. Questionnaires were returned by 144 acute care hospitals, with a coverage of 41 to 72% of hospitals by province. Methods used for detection of MRSA included disk diffusion (91%), microdilution panels (8%) and oxacillin agar screen (9%). Only 34% of laboratories performed disk diffusion testing under optimal conditions for detection of heterogenous resistance. Among 36 hospitals reporting complete susceptibility data of Staphylococcus aureus isolates tested during the study period (n = 24,153), a mean MRSA prevalence of 14% was found (range: 0-70%). The median prevalence increased from 9.5% in 1989 to 13.7% in 1991 and showed a significant linear increase during this period in 30% of these hospitals (p < 0.01). Precautions used for controlling spread of MRSA included hand decontamination using either soap and water or antimicrobial preparations (68% of hospitals), room decontamination (62%), patient isolation (55%) and various barrier precautions (24-49%). Carrier screening was performed in 37% of hospitals, but antibiotic decolonization was attempted in only 24%. This survey identified areas for improvement in MRSA detection methods and underscored the need for multicentric surveillance of MRSA prevalence and a reappraisal of MRSA control strategies in Belgian hospitals.

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.

Methicillin-resistant Staphylococcus aureus: a consensus review of the microbiology, pathogenesis, and epidemiology with implications for prevention and management

Methicillin-resistant Staphylococcus aureus (MRSA) has become a major nosocomial pathogen in community hospitals, long-term-care facilities, and tertiary care hospitals. The basic mechanism of resistance is alteration in penicillin-binding proteins of the organism. Methods for isolation by culture and typing of the organism are reviewed. MRSA colonization precedes infection. A major reservoir is the anterior nares. MRSA is usually introduced into an institution by a colonized or infected patient or health care worker. The principal mode of transmission is via the transiently colonized hands of hospital personnel. Indications for antibiotic therapy for eradication of colonization and treatment of infection are reviewed. Infection control guidelines and discharge policy are presented in detail for acute-care hospitals, intensive care and burn units, outpatient settings, and long-term-care facilities. Recommendations for handling an outbreak, surveillance, and culturing of patients are presented based on the known epidemiology.

Management and epidemiologic analyses of an outbreak due to methicillin-resistant Staphylococcus aureus

PURPOSE

Following implementation of special measures to control a nosocomial outbreak of methicillin-resistant Staphylococcus aureus (MRSA), we used immunoblot typing in conjunction with antimicrobial susceptibility testing to investigate the epidemiology of this event and to determine whether this outbreak represented the failure of infection control measures to limit the spread of previously endemic MRSA strains or the introduction of a new strain of MRSA.

MATERIALS AND METHODS

Isolates of MRSA recovered from hospitalized patients were initially categorized on the basis of antimicrobial susceptibility results. Organisms susceptible to ciprofloxacin and/or trimethoprim/sulfamethoxazole were recovered from patients at a relatively constant rate prior to December 1988 and were categorized as endemic isolates. Subsequently, there was an outbreak due to organisms resistant to both of these antibiotics; these were therefore categorized as outbreak isolates. Isolates were later characterized by immunoblot typing. Prior to this analysis, isolates were given code numbers so that clinical and epidemiologic data as well as resistance patterns were not known until this testing was complete.

RESULTS

Between January 1986 and November 1988, an average of 3.9 patients per month acquired nosocomial MRSA in the Sepulveda Veterans Administration Medical Center. In contrast, from December 1988 to October 1989, 369 MRSA isolates were collected from 125 patients (an average of 11.4 patients per month). Prior to December 1988, all tested nosocomial isolates of MRSA were susceptible to ciprofloxacin and/or to trimethoprim/sulfamethoxazole. In contrast, the outbreak was due to spread of MRSA isolates resistant to these antibiotics. Immunoblot typing of 204 isolates from 98 individuals identified five distinct immunoblot types of which types B and C were by far the most common. Type B was highly associated with outbreak isolates, whereas type C was associated with endemic isolates (p less than 0.001). All sequential isolates from single patients that belonged to different susceptibility categories demonstrated discordant immunoblot types. In contrast, concordant immunoblot types were observed for 25 of 27 sequential isolates that displayed minor variations in antimicrobial resistance. The institution of more stringent infection control measures was followed by the return of nosocomial MRSA acquisition rates to pre-outbreak levels. Although novobiocin and trimethoprim/sulfamethoxazole were extensively used to treat patients harboring outbreak and endemic isolates, respectively, in no instance was the initial MRSA isolate from any patient resistant to novobiocin and only 6% of initial endemic isolates displayed trimethoprim/sulfamethoxazole resistance. A modest, significant increase in the resistance of endemic isolates to various other antimicrobial agents was noted however.

CONCLUSION

Immunoblot analyses provided strong, corroborative evidence that at least two separate strains of MRSA were present during the outbreak and that a newly introduced strain with a distinctive antimicrobial resistance pattern was primarily responsible for the rapid spread of MRSA during the outbreak. The observation that previously effective infection control measures failed to prevent the nosocomial spread of a newly introduced community-acquired MRSA strain suggests that a single set of control measures may not be equally efficacious against all strains of MRSA. In this regard, previously reported variations in resistance to topical antimicrobials and/or antiseptics, and differences in virulence factors such as colonization potential, invasiveness, and survival on fomites, may warrant further study. Control of the outbreak strain of MRSA in our institution did occur after the implementation of more strenuous isolation procedures.(ABSTRACT TRUNCATED)

Should we vigorously try to contain and control methicillin-resistant Staphylococcus aureus?

OBJECTIVE

To review practices currently used to control transmission of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, determine the frequency of their use, and discuss the indications for implementing such measures.

DESIGN

A questionnaire survey to determine how commonly selected control practices are used, and a literature review of the efficacy of control practices.

PARTICIPANTS

Two hundred fifty-six of 360 hospital-based members fo the Society for Hospital Epidemiology of America, Inc. (SHEA) completed the survey questionnaire.

RESULTS

Many different combinations of surveillance and control measures are used by hospitals with MRSA. Nine percent of hospitals stated that no special measures were used to control MRSA. The efficacy of commonly used control measures has not been established by controlled trials.

CONCLUSIONS

Implementing control measures is warranted when MRSA causes a high incidence of serious nosocomial infections, and is desirable when MRSA has been newly introduced into a hospital or into an intensive care unit, or when MRSA accounts for more than 10% of nosocomial staphylococcal isolates. While the value of some practices is well established, measures such as routinely attempting to eradicate carriage of MRSA by colonized patients and personnel require further evaluation.

The impact of methicillin- and aminoglycoside-resistant Staphylococcus aureus on the pattern of hospital-acquired infection in an acute hospital

Infections due to methicillin- and aminoglycoside-resistant Staphylococcus aureus (MARSA) appeared in a new teaching hospital shortly after it opened. The effect this had on the pattern of hospital-acquired infections in the four years that followed is described. No control measures were applied and MARSA became endemic. New infections appeared at a rate of about four for each 1000 patients discharged. It established itself at different levels of incidence in various specialist units, patients under intensive care being most severely affected. MARSA was implicated in half of all hospital-acquired infections due to S. aureus but it was not more pathogenic than its more sensitive counterpart. It had little impact on the life of the hospital.

Importation of methicillin-resistant Staphylococcus aureus from Baghdad to Dublin and subsequent nosocomial spread

We report the spread of a methicillin- and gentamicin-resistant Staphylococcus aureus strain (MGRSA) from the Middle East and its subsequent dissemination within two hospitals in Dublin. The index case, a 30-year-old male with serious blast injuries was transferred from a Baghdad hospital to a Dublin hospital in May 1985. He was heavily infected with two MGRSA strains, one of which spread and was responsible for numerous episodes of nosocomial infection. This strain was very similar to MGRSA isolates recovered in a Baghdad hospital during 1984. This imported strain has now spread to two hospitals in our group causing sepsis. This report emphasizes the difficulty of detecting an imported strain in an endemic area, but above all points to the potential for spread when there is considerable movement of patients and personnel.

Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence

While most authorities agree that methicillin-resistant Staphylococcus aureus (MRSA) are as pathogenic as methicillin-sensitive strains (MSSA), some believe that MRSA are relatively avirulent opportunists, and that their importance has been exaggerated. We present evidence that Hong Kong strains of MRSA and MSSA are equally pathogenic: they have similar virulence in animal models; they are isolated in similar proportions from both deep and superficial clinical sites including blood; in patients with hospital-acquired bacteraemias mortality rates are similar when adjusted for clinical factors; and in both animals and patients with systemic MRSA infection, mortality rates are significantly reduced by vancomycin therapy. Efforts to control the spread of MRSA are justified, and in invasive sepsis early treatment with vancomycin may be life-saving.

Methicillin-resistant Staphylococcus aureus: a ten-year survey in a Dublin hospital

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.

Methicillin-resistant Staphylococcus aureus in two burn units: clinical significance and epidemiological control

Routine isolation adequately controlled MRSA strains in two burns units with a restrictive antibiotic policy. Ventilation control and more rigorous change of clothing offered no further advantage. No carriers among staff were found, but some suffered minor skin lesions that were the source of further MRSA spread. Spread of MRSA from the unit to other parts of the hospital was prevented by early identification of colonized patients and by restricting patient and staff movement.

A descriptive survey of uncontrolled methicillin-resistant Staphylococcus aureus in a twin site general hospital

Over a five year period beginning in 1981, during which control measures were applied intermittently, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) isolates increased steadily within a twin site general hospital. A retrospective chart review of 154 patients identified in 1984-1985 showed that the MRSA 'definitely' contributed to three deaths (2%) and 'probably' contributed to a further 15 (10%). The prolonged median duration of hospital admission (22 days) before first isolation of MRSA, together with the clustering of cases in time on certain wards, suggested that most, if not all, affected patients acquired the MRSA in hospital. As the virulence of MRSA in our outbreak appeared the same as that reported from teaching hospitals, MRSA control measures need to be comprehensively applied in general hospitals.

Methicillin-resistant Staphylococcus aureus bacteraemia in Hong Kong

In the first 22 months of operation at the Prince of Wales Hospital, 26 (46%) of 56 hospital-acquired Staphylococcus aureus bacteraemias were due to methicillin-resistant organisms (MRSA). There were 10 plasmid profiles amongst 24 of the MRSA strains analysed. MRSA bacteraemias were first seen in the hospital 1 year after opening when the isolation rate of MRSA from all sites had risen to about 1% of patient admissions. During the last 3 months of the study period, 17 out of 18 S. aureus bacteraemias were due to methicillin-resistant strains. Patients with MRSA bacteraemia were significantly more likely than those with methicillin-sensitive S. aureus bacteraemia to have had a severe underlying disease, a poor clinical prognosis, prolonged hospitalization, and prior antimicrobial therapy, especially with aminoglycosides. They also had a significantly longer hospital stay after infection, a significantly higher cost of antimicrobial therapy and a higher mortality rate. The lower mortality rate in MRSA patients treated with vancomycin (18%) compared with those treated with other antimicrobials (40%) confirms that, at present, vancomycin is the treatment of choice for invasive MRSA infections.