Molecular fingerprinting of meticillin-resistant Staphylococcus aureus strains isolated from patients and staff of two Iranian hospitals

Meticillin-resistant Staphylococcus aureus (MRSA) is an important cause of hospital-acquired infection. Methods for typing and epidemiological investigation of MRSA isolates have an important impact in detection of MRSA strains, source, transmission and control of these micro-organisms. The aims of this study were to study molecular diversity of MRSA isolates by randomly amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR), the surveillance efficacy of this method and determination of antibiotic resistance patterns of MRSA isolates. MRSA isolates were collected from clinical specimens and noses of 460 staff and inpatients admitted to Imam Khomeini and Paediatric Hospitals during a six-month period (2004-2005). Eighty MRSA strains, in which the presence of mecA gene had been confirmed by PCR, were subjected to RAPD-PCR using five primers and the results were summarised in a dendrogram to show the relationships between the test isolates. Antibiotic resistance patterns of MRSA isolates were also determined by disc agar diffusion method using 13 antibiotic discs according to Clinical and Laboratory Standards Institute guidelines. Forty-three RAPD-PCR profiles were detected. The test isolates were clustered into 18 taxa with 50% similarity, indicating the heterogeneity of our test isolates. MRSA isolates fell into 41 antibiotic resistance patterns. There was correlation between antibiotic resistance patterns and results of RAPD-PCR. Most of the MRSA isolates were multi-resistant.     

Virulence determinants in community and hospital meticillin-resistant Staphylococcus aureus

Staphylococcus aureus produces many virulence factors, most of which act in a synergistic and coordinated fashion. Some appear to be specifically associated with certain severe infections and are produced by meticillin-resistant Staphylococcus aureus (MRSA) clones distributed worldwide. Superantigenic exotoxins appear to be major virulence factors in hospital MRSA clones (HA-MRSA), and staphylococcal enterotoxin A (SEA) may be involved in the physiopathology of septic shock. Panton Valentine Leucocidin (PVL) has emerged as a major virulence factor in community-acquired Staphylococcus aureus (CA-MRSA) infections. In particular, the leukotoxic action of PVL is responsible for the high mortality rate associated with necrotizing pneumonia. CA-MRSA can also harbour the toxic shock toxin 1 (TSST-1) and rarely the exfoliative toxin.     

Burden of meticillin-resistant Staphylococcus aureus colonization and infection in London acute hospitals: retrospective on a voluntary surveillance programme

Although meticillin-resistant Staphylococcus aureus (MRSA) is recognized as an important cause of hospital and community healthcare-associated morbidity, and colonization as a precursor to infection, few studies have attempted to assess the burden of both colonization and infection across acute healthcare providers within a defined health economy. This study describes the prevalence and incidence of MRSA colonization and infection in acute London hospital Trusts participating in a voluntary surveillance programme in 2000-2001. Hospital infection control staff completed a weekly return including details on incident and prevalent colonizations, bacteraemias and other significant infections due to MRSA. Incidence and prevalence rates were calculated for hospitals with sufficient participation across both years. Colonizations accounted for 79% of incident MRSA cases reported; 4% were bacteraemias, and 17% other significant infections. There was no change in incidence of colonization of hospital patients between 2000 and 2001. By contrast, there was an unexplained 49% increase in prevalence of colonizations over this period. For any given month, prevalent colonizations outnumbered incident colonizations at least twofold. This MRSA surveillance programme was unusual for prospective ascertainment of incident and prevalent cases of both colonization and infection within an English regional health economy. Consistent with other studies, the incidence and prevalence of colonization substantially exceeded infection. Given the small contribution of bacteraemias to the overall MRSA burden, and the surveillance, screening and control interventions of recent years, it may be appropriate to review the present reliance on bacteraemia surveillance.     

Costs of an outbreak of meticillin-resistant Staphylococcus aureus

An outbreak of meticillin-resistant Staphylococcus aureus (MRSA) occurred in surgical and internal medicine units of a 1752-bed Finnish tertiary care hospital during 2003-2004. In order to analyse the costs of this 14-month outbreak, patients were categorized as follows: patients with MRSA infections; patients with MRSA colonization; patients exposed to MRSA but whose MRSA status remained inconclusive; and exposed patients who were negative for MRSA. We reviewed a sample of patients' charts to determine the types of clinical infections and interviewed staff about the practical implementation of control measures. The number of patients and patient-days involved in the outbreak were identified from the hospital's databases, with the administrative database supplying unit costs of work and materials. Loss of income due to closed beds was analysed. A total of 266 MRSA-positive patients (114 with infections and 152 colonized) and 797 patients exposed to MRSA were identified (11,744 contact isolation days). There were 1240 patients negative after screening (9880 contact isolation days). Total additional costs of MRSA were 386,062 euro (70% for screening and 25% for contact isolation). Costs due to meticillin resistance in treatment of MRSA infections were 16,000 euro. The income loss for this hospital due to closed beds was 1,183,808 euro. The high cost of MRSA screening underlines the importance of appropriate screening methods. Our model of analysing costs might be useful for other hospitals after adapting variables such as local control measures.     

Costs of nosocomial pneumonia caused by meticillin-resistant Staphylococcus aureus

Nosocomial infections with meticillin-resistant Staphylococcus aureus (MRSA) lead to increased health and economic costs. The purpose of this study was to determine costs for?nosocomial MRSA pneumonia compared with meticillin-susceptible S. aureus (MSSA) pneumonia. A case-control study was conducted with patients who acquired nosocomial pneumonia?with either MRSA or MSSA between January 2005 and December 2007. Patients were matched for age, severity of underlying disease, stay on intensive care units and non-intensive care units, admission and discharge within the same year, and in-hospital stay at least as long as that of cases before MRSA pneumonia. Our analysis includes 82 patients (41 cases, 41 controls). The overall costs for patients with nosocomial MRSA pneumonia were significantly higher than for patients with MSSA pneumonia (?0,684 vs ?8,731; P=0.01). The attributable costs for MRSA pneumonia per patient were ?7,282 (P<0.001). The financial loss was higher for patients with MRSA pneumonia than for patients with MSSA pneumonia (?1,704 vs ?,662; P=0.002). More cases died than controls while in the hospital (13 vs 1 death, P<0.001). Hospital personnel should be aware of the attributable costs of MRSA pneumonia, and should implement control measures to prevent MRSA transmission.     

Review of a three-year meticillin-resistant Staphylococcus aureus screening programme

The Newcastle upon Tyne Hospitals NHS Foundation Trust (NuTH) implemented a seek and destroy (S&D) programme in 2006 to minimise meticillin-resistant Staphylococcus aureus (MRSA) colonisation and/or infection of patients. Using a phased introduction, all patient specialties were included in the scheme by September 2008, well in advance of the mandatory Department of Health, England (DoH) requirement for all patients to be screened. NuTH screens nose, throat and perineum samples from approximately 15,000 patients per month using a chromogenic culture method, showing a mean MRSA prevalence of 2.4%. Provision of seven-day microbiology and infection control services ensured that the turnaround time to prescribing decolonisation therapy was <24 h. Analysis of 168,073 results identified the necessity for inclusion of all three screening sites to maximise recovery of MRSA. Appraisal of the S&D policy demonstrated that MRSA detection rates did not increase despite an exponential increase in workload owing to mandatory inclusion of low risk areas in the screening programme. Review of data during a typical one-month period indicated that only seven day-case patients would not have been identified as MRSA carriers using our targeted S&D approach compared with the DoH universal screening. Detection of these additional patients incurred total laboratory costs of ￡20,000 and generated a further 4200 associated negative screens in one month alone. Our study indicates that a screening strategy based upon clinical risk is more pragmatic and more cost-effective than the universal programme currently required in England.     

Infection control and meticillin-resistant Staphylococcus aureus in nursing homes in Oslo

Healthcare workers (HCWs) might be important in reducing healthcare-associated infections but infected or colonised HCWs may still spread pathogenic microbes to others. Norwegian policies for infection control in healthcare environments emphasise infection control programmes for both patients and HCWs. In this study, HCWs from 42 of 55 nursing homes in Oslo participated in an investigation concerning the implementation of infection control programmes during 2006-2007. Three separate questionnaires were used: the first aimed at nursing staff (enrolled nurses and assisting staff); the second for ward sisters; and the third for institution managers. Nearly 70% of the nursing homes had policies for controlling infection and transmission of meticillin-resistant Staphylococcus aureus (MRSA). About 60% of the institutions had policies for tracing MRSA infections. Four of five ward sisters tested patients for MRSA when wounds were not healing, when admitted from hospitals overseas, when patients shared a room with an MRSA-infected patient, or if patients had ever been MRSA positive. Two of five sisters would test patients with chronic urinary tract infection or patients admitted from another hospital. Among nursing staff, one out of five had cared for MRSA-positive patients. Only 4% of the staff had worked in healthcare institutions abroad, and only a few of them had been tested for MRSA. Almost 20% of the responding nursing staff worked at several institutions at the same time.     

Methicillin-resistant and -susceptible Staphylococcus aureus sequence type 398 in pigs and humans

Methicillin-resistant Staphylococcus aureus sequence type 398 (ST398 MRSA) was identified in Dutch pigs and pig farmers. ST398 methicillin-susceptible S. aureus circulates among humans at low frequency (0.2%) but was isolated in 3 human cases of bacteremia (2.1%; p = 0.026). Although its natural host is probably porcine, ST398 MRSA likely causes infections in humans.     

Endocarditis due to meticillin-resistant Staphylococcus aureus originating from pigs

A 63-year-old woman with a kidney transplant was admitted with endocarditis caused by meticillin-resistant Staphylococcus aureus (MRSA). Once her antibiotic therapy had been adjusted to the sensitivity-pattern of the bacterial strain she recovered, without the need for surgical intervention. The isolated S. aureus was typed by multi-locus sequence typing as sequence type 398, a MRSA-strain that has recently been isolated from a high percentage of Dutch pigs. This is the first report of a life-threatening infection with this pig MRSA. This strain is genetically different from the globally dispersed nosocomial MRSA-strains, and also from the strains that have been epidemic for several years in the USA as the causative agent ofcommunity-acquired skin infections. The Dutch Working Group on Infection Prevention (WIP) has recently adjusted its guidelines to halt further spread of this strain, and advises that the population at risk (pig breeders, slaughterhouse personnel and veterinarians) be held in isolation when hospitalised until MRSA colonisation has been excluded. The patient described here, however, did not belong to this population at risk.