Successful Veterans Affairs initiative to prevent methicillin-resistant Staphylococcus aureus infections revisited

In 2011 Jain et al reported a 62% reduction of healthcare-associated methicillin-resistant Staphylococcus aureus infections that resulted from an intervention bundle. Here we present a mathematical model and prove, using parameters from the study by Jain et al, that the universal screen and isolate strategy can have contributed only marginally to the reduction in infections.     

Cross-Canada spread of methicillin-resistant Staphylococcus aureus via transplant organs.

We report our investigation of the transmission of methicillin-resistant Staphylococcus aureus (MRSA) through transplantation. The kidneys, liver, and corneas were harvested from a child who died in Nova Scotia. Several days postmortem it was learned that culture of a premortem endotracheal tube aspirate from the donor yielded MRSA. Both kidneys were transplanted into a child in Nova Scotia and the liver into a child in Alberta. Both recipients subsequently became blood culture-positive for MRSA. One corneal ring from the donor was MRSA-positive. All four MRSA isolates were mecA-positive by polymerase chain reaction (PCR). The relatedness of the MRSA isolates was examined by restriction fragment length polymorphism (RFLP) analysis, a 16S-23S ribosomal PCR typing method, and comparison of antibiograms. Results were identical for all four MRSA isolates. These findings indicate that MRSA from the donor was transferred to recipients during implantation of harvested organs in Alberta and Nova Scotia, a cross-Canada spread.     

The spread of a mupirocin-resistant/methicillin-resistant Staphylococcus aureus clone in Kuwait hospitals

High-level mupirocin- and methicillin-resistant Staphylococcus aureus (MRSA) isolated from five hospitals in Kuwait were studied by pulsed-field gel electrophoresis (PFGE) to determine their relatedness to one another and to high-level mupirocin-resistant MRSA isolated previously in a Burns Unit. The genetic location of mupirocin resistance determinant was also determined. All of the isolates were resistant to gentamicin, kanamycin, streptomycin, tetracycline and cadmium, and contained plasmids of 38, 26 and 2.8 kb. Two isolates contained additional 4.4-kb plasmids. Transfer experiments demonstrated that the 38-kb plasmid encoded high-level mupirocin resistance and the 4.4-kb plasmid encoded chloramphenicol resistance. PFGE typing of representative isolates from the five hospitals demonstrated that the majority of them had identical or closely related pulsed-field patterns suggesting that they had a common origin. However, they differed from high-level mupirocin-resistant MRSA isolated previously in the Burns Unit in their resistance and pulsed-field patterns. Whereas the majority of the previous isolates were susceptible to ciprofloxacin and resistant to trimethoprim and chloramphenicol, the majority of the current isolates were susceptible to trimethoprim and chloramphenicol, and resistant to ciprofloxacin. Only one of the current isolates had identical pulsed-field pattern to the majority of isolates obtained previously in the Burns Unit. The results suggested that a previously dominant clone of high-level mupirocin-resistant MRSA has been replaced in the Burns Unit by a new clone, which also spread in four other hospitals.     

Unusual spread of a penicillin-susceptible methicillin-resistant Staphylococcus aureus clone in a geographic area of low incidence.

We describe the unusual spread of a penicillin-susceptible methicillin-resistant Staphylococcus aureus (MRSA) clone in hospitals in western Switzerland, where the incidence of MRSA is usually low. During a 2-year period, this clone had been responsible for several outbreaks and had been isolated from >156 persons in 21 institutions. Molecular typing by pulsed-field gel electrophoresis (PFGE) demonstrated that all of these isolates belonged to the same clone. In 1 of the outbreaks, involving 30 cases, the clone was responsible for at least 17 secondary cases. In contrast, during the period of the latter outbreak, 9 other patients harboring different MRSA strains, as assessed by PFGE, were hospitalized in the same wards, but no secondary cases occurred. These observations suggest that this clone, compared with other MRSA strains, had some intrinsic factor(s) that contributed to its ability to disseminate and could thus be considered epidemic.     

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.     

Control of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of nosocomial infections worldwide. Different approaches to the control of this pathogen have met with varying degrees of success in different health care settings. Controversies exist with regards to various MRSA control strategies. The implementation and outcomes of control measures depend on several factors, including scientific, economic, administrative, governmental, and political influences. It is clear that flexibility to adapt and institute these measures in the context of local epidemiology and resources is required.     

Emergence of ciprofloxacin resistance in nosocomial methicillin-resistant Staphylococcus aureus isolates. Resistance during ciprofloxacin plus rifampin therapy for methicillin-resistant S aureus colonization

We initiated a randomized, single-blinded trial of ciprofloxacin plus rifampin vs sulfamethoxazole and trimethoprim plus rifampin in the therapy for patients who underwent colonization with methicillin-resistant Staphylococcus aureus (MRSA). Patients who were colonized with MRSA received 2 weeks of either regimen. The study was terminated after the enrollment of 21 subjects due to the recognition of ciprofloxacin resistance in 10 of 21 new MRSA isolates during the last 2 months of the study. Five of the 10 patients with ciprofloxacin-resistant MRSA isolates had never received ciprofloxacin. Long-term (6-month) eradication had been achieved in only three of 11 ciprofloxacin plus rifampin and four of 10 sulfamethoxazole and trimethoprim plus rifampin recipients. The use of this new fluoroquinolone for the eradication of MRSA colonization is usually not effective and may risk the development of ciprofloxacin resistance in MRSA within the hospital environment.     

Postoperative toxic shock syndrome caused by a highly virulent methicillin-resistant Staphylococcus aureus strain.

We report on a rare fatal case of postoperative toxic shock syndrome caused by infection with a highly virulent methicillin-resistant Staphylococcus aureus strain, designated Sak-1, which was found to be characteristic in its increased production of toxic shock syndrome toxin 1 in human whole blood (about 30-fold more than produced in Tod Hewitt broth). The strain also produced a high level of toxic shock syndrome toxin 1 in the circulating blood of mice experimentally infected with the strain.     

A nosocomial outbreak of community-associated methicillin-resistant Staphylococcus aureus among healthy newborns and postpartum mothers

BACKGROUND: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increasingly been isolated from individuals with no predisposing risk factors; however, such strains have rarely been linked to outbreaks in the hospital setting. The present study describes the investigation of an outbreak of CA-MRSA that occurred in the maternal-newborn unit of a large community teaching hospital in Toronto, Ontario. METHODS: Screening and clinical specimens collected from mothers and newborns delivered during the outbreak period, as well as from staff on the affected unit, were submitted for microbiological testing. Computerized delivery logs and nursing notes were reviewed, and a case control study was conducted. RESULTS: Analysis by pulsed-field gel electrophoresis revealed 38 babies and seven mothers with MRSA colonization and/or infection by the same unique strain (Canadian MRSA-10-related) from September to December 2004. Isolates were characterized as having the staphylococcal chromosome cassette mec type IVa and were positive for the Panton-Valentine leukocidin gene. No one health care worker was associated with all cases; however, mothers and newborns exposed to one particular nurse (Nurse A) were almost 23 times (odds ratio 22.7, 95% CI 3.3 to 195.9) more likely to acquire MRSA than those with no such contact. MRSA was successfully isolated from Nurse A and from an environmental swab of a telephone recently used by Nurse A; both isolates matched the pulsed-field gel electrophoresis pattern of the outbreak strain. CONCLUSION: The first nosocomial outbreak of CA-MRSA among healthy newborns and postpartum mothers in Canada is described. Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment and monitoring of colonized and/or infected staff.