Methicillin-resistant Staphylococcus aureus in Dublin 1971-84

Activated mesenchymal stem cells increase drug susceptibility of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa

Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are major causes of hospital-acquired infections and sepsis. Due to increasing antibiotic resistance, new treatments are needed. Mesenchymal stem cells (MSCs) have antimicrobial effects, which can be enhanced by preconditioning with antibiotics. This study investigated using antibiotics to strengthen MSCs against MRSA and P. aeruginosa. MSCs were preconditioned with linezolid, vancomycin, meropenem, or cephalosporin. Optimal antibiotic concentrations were determined by assessing MSC survival. Antimicrobial effects were measured by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antimicrobial peptide (AMP) gene expression. Optimal antibiotic concentrations for preconditioning MSCs without reducing viability were 1 μg/mL for linezolid, meropenem, and cephalosporin and 2 μg/mL for vancomycin. In MIC assays, MSCs preconditioned with linezolid, vancomycin, meropenem, or cephalosporin inhibited MRSA or P. aeruginosa growth at lower concentrations than non-preconditioned MSCs (p ≤ 0.001). In MBC assays, preconditioned MSCs showed enhanced bacterial clearance compared to non-preconditioned MSCs, especially when linezolid and vancomycin were used against MRSA (p ≤ 0.05). Preconditioned MSCs showed increased expression of genes encoding the antimicrobial peptide genes hepcidin and LL-37 compared to non-preconditioned MSCs. The highest hepcidin expression was seen with linezolid and vancomycin preconditioning (p ≤ 0.001). The highest LL-37 expression was with linezolid preconditioning (p ≤ 0.001). MSCs' preconditioning with linezolid, vancomycin, meropenem, or cephalosporin at optimal concentrations enhances their antimicrobial effects against MRSA and P. aeruginosa without compromising viability. This suggests preconditioned MSCs could be an effective adjuvant treatment for antibiotic-resistant infections. The mechanism may involve upregulation of AMP genes.

Preoperative screening for nasal carriage of methicillin-resistant Staphylococcus aureus in patients undergoing general thoracic surgery

Objectives: Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) is a risk factor for surgical site infections (SSIs). However, few studies have evaluated the rate of nasal carriage of MRSA and its effect on SSIs in patients undergoing general thoracic surgery. We investigated the importance of preoperative screening for nasal carriage of MRSA in patients undergoing general thoracic surgery.

Patients and Methods: We retrospectively analyzed 238 patients with thoracic diseases who underwent thoracic surgery. We reviewed the rates of nasal carriage of MRSA and SSIs.

Results: Results of MRSA screening were positive in 11 of 238 patients (4.6%), and 9 of these 11 patients received nasal mupirocin. SSIs occurred in 4 patients (1.8%). All 4 patients developed pneumonia; however, MRSA pneumonia occurred in only 1 of these 4 patients. No patient developed wound infection, empyema, and/or mediastinitis. SSIs did not occur in any of the 11 patients with positive results on MRSA screening.

Conclusions: The rates of nasal carriage of MRSA and SSIs were low in this case series. Surveillance is important to determine the prevalence of MRSA carriage and infection in hospitals, particularly in the intensive care unit. However, routine preoperative screening for nasal carriage of MRSA is not recommended in patients undergoing general thoracic surgery.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Methicillin-Resistant Staphylococcus aureus Outbreak at a Veterans' Affairs Medical Center: Importance of Carriage of the Organism by Hospital Personnel

The reported prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) by hospital personnel averages 2.5%. From August 1985 to September 1987, 155 patients at our Veterans' Affairs Medical Center (VAMC) were colonized or infected with MRSA. In December 1986, only two (2.1%) of 94 healthcare workers were identified as nasal carriers. Prompted by a sharp increase in the number of patients with MRSA in early 1987, contact tracing identified 450 employees, of whom 36 (8%) were nasal carriers. Thirty-five percent of surgical residents (7 of 20) were nasal carriers. Prior to being identified as a nasal carrier, one surgical resident was associated with the inter-hospital spread of the VAMC MRSA strain to the burn unit of the affiliated university hospital. Three family members of two employee carriers were also found to harbor the epidemic strain. All 36 carriers were decolonized with various antimicrobial combinations. Vigorous infection control measures were effective in controlling the epidemic. The frequency of MRSA carriage by hospital personnel at our medical center during the epidemic proved higher than previously appreciated. Thus, healthcare workers may comprise a sizable MRSA reservoir. During an MRSA epidemic, infection control should attempt to identify and decolonize this hospital reservoir, as these individuals can disseminate MRSA both within the hospital as well as into the community.

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.

Molecular epidemiology and antimicrobial resistance of methicillin-resistant Staphylococcus aureus bloodstream isolates in Taiwan, 2010

The information of molecular characteristics and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus (MRSA) is essential for control and treatment of diseases caused by this medically important pathogen. A total of 577 clinical MRSA bloodstream isolates from six major hospitals in Taiwan were determined for molecular types, carriage of Panton-Valentine leukocidin (PVL) and sasX genes and susceptibilities to 9 non-beta-lactam antimicrobial agents. A total of 17 genotypes were identified in 577 strains by pulsotyping. Five major pulsotypes, which included type A (26.2%, belonging to sequence type (ST) 239, carrying type III staphylococcal chromosomal cassette mec (SCCmec), type F (18.9%, ST5-SCCmecII), type C (18.5%, ST59-SCCmecIV), type B (12.0%, ST239-SCCmecIII) and type D (10.9%, ST59-SCCmecV_T/IV), prevailed in each of the six sampled hospitals. PVL and sasX genes were respectively carried by ST59-type D strains and ST239 strains with high frequencies (93.7% and 99.1%, respectively) but rarely detected in strains of other genotypes. Isolates of different genotypes and from different hospitals exhibited distinct antibiograms. Multi-resistance to ≥3 non-beta-lactams was more common in ST239 isolates (100%) than in ST5 isolates (97.2%, P = 0.0347) and ST59 isolates (8.2%, P<0.0001). Multivariate analysis further indicated that the genotype, but not the hospital, was an independent factor associated with muti-resistance of the MRSA strains. In conclusion, five common MRSA clones with distinct antibiograms prevailed in the major hospitals in Taiwan in 2010. The antimicrobial susceptibility pattern of invasive MRSA was mainly determined by the clonal distribution.

Staphylococcus aureus: the enduring pathogen in surgery

Staphylococcus aureus is part of the normal bacterial flora of the upper respiratory tract, especially the nose, but it can colonise other sites, such as the skin. However, S. aureus is also the commonest cause of surgical site infection (SSI) and is a major cause of bloodstream infection (BSI). The development of staphylococcal infection arises from a combination of bacterial factors, e.g. production of toxins and host factors, including underlying patient disease, e.g. diabetes mellitus. The surveillance of SSI and BSI are increasingly components of national quality programmes to reduce healthcare-associated infection (HCAI) in the UK, Ireland and beyond and the proportion of S. aureus BSI due to methicillin-resistant S. aureus (MRSA) has declined in recent years but not necessarily that due to methicillin-susceptible S. aureus. However, the complexity and sophistication of the staphylococcal genome has enabled it to change and adapt to varying circumstances such as exposure to a new antibiotic, adherence to a biomedical device and transfer from an animal to a human host. The future will perhaps see more cases of community-acquired MRSA and which may become endemic in hospitals and cause HCAI, technology becoming available to rapidly detect, type and characterise isolates for resistance and virulence and finally greater efforts at local and national level to drive down infection rates. However, good surgical practice, education and audit supported by new technology will enable surgeons to meet the challenges ahead.

Laser light combined with a photosensitizer may eliminate methicillin-resistant strains of Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital acquired infection throughout the world especially in wound and burn infections, pneumonia, septicaemia and endocarditis. We describe the effect of a HeNe laser in combination with a TBO dye on the viability of MRSA. A total of 34 isolates of S. aureus were obtained from 100 patients suffering from burns or wounds and from the nasal vestibulum of medical and nonmedical staff as carriers; eight isolates were methicillin-resistant. The isolates were exposed for 5, 10 and 15 min to a HeNe laser at a wavelength of 632.8 nm and 7.5 mW output power in the presence of 50 microg/ml toluidune blue O photosensitizer. The viable count was substantially decreased as determined by the plate count method for the three exposure times, with 100% killing with the 15-min exposure time. No significant effect was observed on MRSA isolates exposed to the laser alone. So MRSA was completely eradicated following 15 min exposure to a 632.8-nm HeNe laser in the presence of 50 microg/ml toluidune blue O photosensitizer under in vitro conditions.

The role of healthcare personnel in the maintenance and spread of methicillin-resistant Staphylococcus aureus

Healthcare workers may acquire methicillin-resistant Staphylococcus aureus (MRSA) from patients, both hospital and home environments, other healthcare workers, family and public acquaintances, and pets. There is a consensus of case reports and series which now strongly support the role for MRSA-carrying healthcare personnel to serve as a reservoir and as a vehicle of spread within healthcare settings. Carriage may occur at a number of body sites and for short, intermediate, and long terms. A number of approaches have been taken to interrupt the linkage of staff-patient spread, but most emphasis has been placed on handwashing and the treatment of staff MRSA carriers. The importance of healthcare workers in transmission has been viewed with varying degrees of interest, and several logistical problems have arisen when healthcare worker screening is brought to the forefront. There is now considerable support for the screening and treatment of healthcare workers, but it is suggested that the intensity of any such approach must consider available resources, the nature of the outbreak, and the strength of epidemiological associations. The task of assessing healthcare personnel carriage in any context should be shaped with due regard to national and international guidelines, should be honed and practiced according to local needs and experience, and must be patient-oriented.

Guidelines for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the UK

These evidence-based guidelines have been produced after a literature review of the treatment and prophylaxis of methicillin-resistant Staphylococcus aureus (MRSA) infection. The guidelines were further informed by antibiotic susceptibility data on MRSA from the UK. Recommendations are given for the treatment of common infections caused by MRSA, elimination of MRSA from carriage sites and prophylaxis of surgical site infection. There are several antibiotics currently available that are suitable for use in the management of this problem and potentially useful new agents are continuing to emerge.

Nasal carriage of methicillin-resistant Staphylococcus aureus among hospital staff and outpatients

This study sought to determine the rate of nasal methicillin-resistant Staphylococcus aureus (MRSA) carriage among hospital staff and outpatients. Nasal swabs were obtained from 500 outpatients and 500 hospital staff. Hospital staff were 2.3-fold more likely to carry MRSA than were outpatients (6% vs 2.6%, P = .013).

Molecular epidemiology of clinical isolates of methicillin-resistant Staphylococcus aureus in Taiwan

During July 2000 and October 2001, a total of 595 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were collected from six medical centers distributed in northern, central, and southern Taiwan. Specimen sources included blood (n = 279), pus (n = 173), sputum (n = 94), body fluids (n = 21), catheter tips (n = 20), and urine (n = 8). Pulsed-field gel electrophoresis (PFGE) with SmaI digestion was used to fingerprint these isolates. A total of 31 genotypes with 97 type-subtypes were identified. Subtypes could be identified in 7 genotypes. While there were 6 to 15 genotypes in each hospital, 433 isolates (73%) were shown to belong to a major type (genotype A, with 29 subtypes). This genotype was not only the type prevailing in all six hospitals but also the predominant clone in each hospital, accounting for 46 to 89% of all isolates in each hospital. Genotype C (16 subtypes) was the second dominant genotype, accounting for 9% of all isolates, and was distributed in five hospitals. Genotypes D (11 subtypes), E (5 subtypes), and B (6 subtypes) were distributed in five, four, and three hospitals, respectively. The other 26 types (30 type-subtypes) were minor. We conclude that the majority of MRSA clinical isolates shared a common PFGE pattern, indicating the presence of a single, epidemic MRSA clone prevailing in major hospitals in Taiwan.

Surveillance of hospital-acquired infection in the Republic of Ireland: past, present and future

There is increasing interest in the surveillance of hospital-acquired infection (HAI) in the Republic of Ireland due to a greater awareness of the consequences of antibiotic resistance, and consumer pressure in the form of public expectations of the quality of health care. To date there have been no nationwide prospective surveillance projects but surveillance has taken place in the form of participation in international and national studies, and the description of local outbreaks. Infection control teams and others have participated in projects such as a European study of HAI in intensive care units conducted in 1992, the second national prevalence study conducted in the UK in 1993 and two surveys of methicillin-resistant Staphylococcus aureus (MRSA) carried out in 1995 and 1999, the latter involving colleagues in Northern Ireland. There have been a number of local surveys of antibiotic-resistant bacteria including the molecular characterization of MRSA in Dublin hospitals, vancomycin-resistant enterococci, and Gram-negative bacteria such as Enterobacter spp. and Serratia spp. affecting compromised patients such as bone marrow transplant recipients. In the future, it is hoped to standardize case definitions, automate data entry, increase collaboration with surveillance initiatives in Northern Ireland and link in with European networks such as EARSS and HELICS. Apart from the need to improve the quality of health care in Irish hospitals, approximate costings suggest that there are potential savings of 7.5 pounds sterling -15 pounds sterling m to be made following a reduction of HAI rates of 15%.

Strategies for the management of healthcare staff colonized with epidemic methicillin-resistant Staphylococcus aureus

An outbreak of epidemic methicillin-resistant Staphylococcus aureus (MRSA) caused by EMRSA-16 has affected hospitals in north east Northamptonshire since April 1991. Between the start of the outbreak and December 1995, 74 healthcare staff (0.9% of the staff screened) were colonized by the outbreak strain. Thirty-two percent of colonized staff were excluded from work, and six were excluded for periods of longer than three weeks. Twenty-four percent of staff had more than one course of treatment to eradicate carriage. The contribution of staff carriage in hospitals where EMRSA-16 is endemic and strategies for the management of colonized staff are discussed. We conclude that screening of staff has a limited role in the control of outbreaks caused by EMRSA-16 and that when resources for screening are scarce priority should be given to patients.

Staphylococcus aureus sensitivity to various antibiotics--a national survey in Ireland 1993

The sensitivity of Staphylococcus aureus (S. aureus) to methicillin, penicillin, gentamicin, erythromycin, ciprofloxacin, fusidic acid and mupirocin was tested in 1152 clinical isolates from nine hospital microbiology departments. In all cases standard methods for culture and sensitivity were employed using either the Stokes' or a modified Stokes' method for susceptibility testing. The isolates were recovered from 1150 patients (606 men, 544 women; mean age: 41 years) and only those deemed relevant to the patient's clinical condition were included. Of the total 1152 isolates, 454 were regarded as hospital acquired, 506 were community acquired and the source of the remaining 192 isolates was unknown. The overall percentages of S. aureus sensitive to the tested antibiotics were as follows: methicillin 85%, penicillin 8%, gentamicin 89%, ciprofloxacin 85%, erythromycin 80%, fusidic acid 96%, mupirocin 98%. The sensitivity of the methicillin resistant strains to the other antibiotics tested was generally low except for fusidic acid and mupirocin, both of which retain good activity against methicillin resistant S. aureus (MRSA).

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.

Nasal carriage of Staphylococcus aureus in Australian (pre-clinical and clinical) medical students

The nasal carriage of Staphylococcus aureus in 808 Australian medical students was studied. Five groups of students experienced varying degrees of clinical exposure in a hospital environment ranging from 0 to 42 months. The overall percentage of carriers among the five groups did not vary. However, with increasing clinical exposure there was a decrease in the percentage of isolates sensitive to all antibiotics tested, and an increase in the carriage of S. aureus resistant to three or more antibiotics. No carriers of methicillin-resistant S. aureus (MRSA) were detected. The comparative rates of S. aureus carriage between female and male students varied. The relevance of medical students as nasal carriers of S. aureus in the hospital environment today is discussed.

The incidence of isolation of methicillin-resistant Staphylococcus aureus (MRSA) strains from skin infections during the past three years (1989-1991)

We did a statistical study of 294 strains of Staphylococcus aureus (S. aureus) isolated from skin infections during the period from January of 1989 to December of 1991 in the Department of Dermatology, Kansai Medical University Hospital. We especially examined methicillin-resistant S. aureus (MRSA) from the point of view of incidence, variety of skin infections with MRSA, coagulase type, phase type, and resistance against antimicrobial agents. The frequency of isolation of MRSA has been increasing. In 1991, the proportion of MRSA isolates among all S. aureus strains isolated from skin infections was 41.5%. MRSA was isolated most often from infectious decubitus. Coagulase type II and phage group NT (not typable) MRSA were most frequently isolated. The resistance of MRSA to OFLX and IMP/CS had remarkably increased. Notably, the resistance to MINO was low before 1991.

Ten years' experience with methicillin-resistant Staphylococcus aureus in a large Australian hospital

The Royal Brisbane Hospital (RBH) is a 1200-bed teaching hospital with acute, general and specialist units for adult patients. Methicillin-resistant Staphylococcus aureus (MRSA) was first detected at the RBH in 1975 and the number of new patients colonized and infected increased from one in 1975 to 720 in 1989, with a peak of 811 in 1987. Virulence may be inferred from blood culture isolates. Between 1979 and 1989 the number of patients with S. aureus bacteraemia increased from 40 to 138 per year. The percentage of these isolates which were MRSA varied from a low of 4% in 1980 to a peak of 37% in 1984 with 28% in 1989. The control attempts, sensitivity patterns, sources of the isolates and their probable impact and importance will be discussed.

Nurses' hands as vectors of hospital-acquired infection: a review

Hospital-acquired infections (HAI) are notorious for the manner in which they complicate the course of the original illness, increase costs of hospital stay and delay recovery. This review will briefly outline the problems presented by HAI in developed countries and present evidence that Staphylococcus aureus and gram negative bacilli, the main causative agents, reach susceptible patients via the contact rather than airborne route, predominantly on the hands of hospital staff. Good hand hygiene could help reduce the economic burden and patient distress caused by HAI, but there is evidence that it is infrequently and poorly performed by nurses, the health care staff most frequently in continuous contact with patients. Possible reasons are explored in an attempt to identify strategies to improve hand hygiene.

Methicillin-resistant Staphylococcus aureus outbreak at a Veterans' Affairs Medical Center: importance of carriage of the organism by hospital personnel

The reported prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) by hospital personnel averages 2.5%. From August 1985 to September 1987, 155 patients at our Veterans' Affairs Medical Center (VAMC) were colonized or infected with MRSA. In December 1986, only two (2.1%) of 94 healthcare workers were identified as nasal carriers. Prompted by a sharp increase in the number of patients with MRSA in early 1987, contact tracing identified 450 employees, of whom 36 (8%) were nasal carriers. Thirty-five percent of surgical residents (7 of 20) were nasal carriers. Prior to being identified as a nasal carrier, one surgical resident was associated with the inter-hospital spread of the VAMC MRSA strain to the burn unit of the affiliated university hospital. Three family members of two employee carriers were also found to harbor the epidemic strain. All 36 carriers were decolonized with various antimicrobial combinations. Vigorous infection control measures were effective in controlling the epidemic. The frequency of MRSA carriage by hospital personnel at our medical center during the epidemic proved higher than previously appreciated. Thus, healthcare workers may comprise a sizable MRSA reservoir. During an MRSA epidemic, infection control should attempt to identify and decolonize this hospital reservoir, as these individuals can disseminate MRSA both within the hospital as well as into the community.

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.

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.

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.

Pulmonary infection due to methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) are now causing severe clinical infection on a worldwide basis. Pulmonary infection due to MRSA although widely reported is poorly documented. We report the predisposing factors, underlying diseases, treatment and outcome in 4 patients with pneumonia, 3 patients with empyema thoracis, 1 patient with pneumonia and empyema thoracis, 1 patient with pneumonia plus lobectomy wound infection and 2 patients with lung abscess. Vancomycin was highly effective in treatment, a finding compatible with experience treating other severe MRSA infections.

Plasmid fingerprinting of methicillin-resistant Staphylococcus aureus strains isolated in Hamburg

By means of restriction endonuclease digests and DNA/hybridisation studies we analysed ten representative methicillin-resistant Staphylococcus aureus strains of our collection for plasmid similarities and plasmid associated resistance determinants. We found that strains isolated at our laboratory contained identical or at least most similar plasmids. Isolates from another geographical origin showed different plasmid patterns. We found resistance determinants for gentamicin to be chromosomally encoded, whereas resistance to heavy metal ions and chloramphenicol was always plasmid associated. Resistance to trimethoprim, tetracycline and erythromycin was usually chromosomally mediated but could also reside on a plasmid. Our results indicate that methicillin-resistant strains from our collection may have a common origin. The clinical relevance of these results is discussed.

Antimicrobial resistance of Staphylococcus aureus: genetic basis

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Molecular typing of methicillin and gentamicin resistant Staphylococcus aureus in Dublin

The high incidence of infection in Dublin hospitals caused by non-typable strains of methicillin- and gentamicin-resistant Staphylococcus aureus (MGRSA) has created an important epidemiological problem as conventional methods of sub-dividing these organisms have not been useful. This report describes a novel approach to the typing and analysis of MGRSA strains, particularly non-typable isolates, by comparing restriction endonuclease HindIII digest patterns of total cellular DNA; and by using Southern hybridization analysis to detect size variations or polymorphisms in restriction endonuclease cleavage fragments within small regions of the chromosome. Non-typable MGRSA strains and isolates belonging to two phenotypically related groups of phage-type 77 and 77/84 strains were readily subdivided on the basis of molecular size differences in high molecular weight DNA fragments generated by the enzyme HindIII. Restriction endonuclease fragment size polymorphisms were readily detected in many of the non-typable strains tested in hybridization experiments, and these were used for strain sub-division. Both techniques were useful tools for the separation of closely related MGRSA strains.

Methicillin-resistant Staphylococcus aureus: a 6-month survey in a Lisbon paediatric hospital

The prevalence of nasal colonization and infection with methicillin-resistant Staphylococcus aureus (MRSA) among patients and staff was studied in a section of a Paediatric Surgical Unit in Lisbon between February and July 1985. Nasal colonization was demonstrated in 41% of burned patients, 5% of non-burned patients and 35% of the nurses. Infection by MRSA occurred in 30% of the burns. The isolates had identical serological patterns, slight differences on phage typing and were resistant to methicillin, cephalosporins, tetracycline, erythromycin and aminoglycosides. A chloramphenicol resistance plasmid of 3 Md was present in those isolates which were chloramphenicol resistant and a small plasmid of 1.7 Md which coded for constitutive erythromycin resistance was present in many isolates. Gentamicin, tetracycline and inducible erythromycin resistance were chromosomal. Several reasons for the apparent low virulence of the isolates are discussed. Attempts to control the outbreak by the discharge of colonized or infected patients, improvement of nursing practices and treatment with temporary removal from work of the colonized nurses did not eliminate the organism from the unit.