Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA): molecular background, virulence, and relevance for public health

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Risk factors for acquisition of Methicillin-resistant Staphylococcus aureus among patients from a burn unit in Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) is an important agent of colonization and infection in burn units. in order to identify risk factors for MRSA acquisition in a Brazilian burn unit, we performed two retrospective studies. In the first ("cohort" study), 175 patients who were not colonized with MRSA on admission were followed to assess risk factors for MRSA acquisition. in the second ("case-case-control" study), 143 individuals from the previous study who were negative for both MRSA and Methicillin-susceptible S. aureus (MSSA) on admission were followed. Case-control studies were performed to investigate risk factors for MRSA and MSSA acquisition. MRSA and MSSA were recovered from 75 and 23 patients, respectively. In the "cohort" study, only the number of wound excisions (Odds Ratio [OR] = 1.55, 95% Confidence Interval [CI] = 1.21-1.98, P = 0.001) was associated with MRSA acquisition. in the "case-case-control" study, burns involving head (OR=3.43, 95%CI = 1.50-7.81, P = 0.003) and the number of wound excisions (OR = 1.83, 95%CI = 1.27-2.63, P = 0.001) were significant risk factors for MRSA. Burns involving perineum were negatively associated with MSSA acquisition (OR = 0.16, 95%CI = 0.03-0.75, P = 0.02). In conclusion, the acquisition of MRSA was related to the site of the burn and to the surgical manipulation of tissues, but not to the use of antimicrobials. (C) 2009 Elsevier Ltd and ISBI. All rights reserved.

Effectiveness of two disinfectant solutions and microwave irradiation in disinfecting complete dentures contaminated with methicillin-resistant Staphylococcus aureus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Immunization protected well nourished mice but not undernourished ones from lung injury in Methicillin-resistant Staphylococcus aureus (MRSA) infection

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nasopharyngeal colonization with methicillin-resistant staphylococcus aureus and mortality among patients in an intensive care unit

A colonização de nasofaringe por Staphylococcus aureus, resistente à meticilina (Methicillin-resistant S.aureus - MRSA), é comum em pacientes criticamente doentes, mas seu significado prognóstico não é inteiramente conhecido. Realizou-se estudo de coorte retrospectivo com 122 pacientes de uma unidade de terapia intensiva que realizaram triagem semanal para colonização por MRSA. Os desfechos de interesse foram: mortalidade geral e mortalidade por infecção. Diversas variáveis de exposição (gravidade, procedimentos, intercorrências e colonização nasofaríngea por MRSA) foram analisadas em modelos univariados e multivariados. Fatores significativamente associados à mortalidade geral ou por infecção foram: APACHE II e doença pulmonar. A colonização por MRSA não foi preditora de mortalidade geral (OR=1,02; IC95%=0,35-3; p=0,97) ou por infecção (OR=0,96; IC95%=0,33-2,89; p=0,96). Os resultados sugerem que, na ausência de fatores de gravidade, a colonização por MRSA não caracteriza pior prognóstico.

Case-case-control study of risk factors for nasopharyngeal colonization with methicillin-resistant Staphylococcus aureus in a medical-surgical intensive care unit

Nasopharyngeal colonization with methicillin-resistant Staphylococcus aureus (MRSA) often precedes the development of nosocomial infections. In order to identify risk factors for MRSA colonization, we conducted a case-case-control study, enrolling 122 patients admitted to a medical-surgical intensive care unit (ICU). All patients had been screened for nasopharyngeal colonization with S. aureus upon admission and weekly thereafter. Two case-control studies were performed, using as cases patients who acquired colonization with MRSA and methicillin-susceptible S. aureus (MSSA), respectively. For both studies, patients in whom colonization was not detected during ICU stay were selected as control subjects. Several potential risk factors were assessed in univariate and multivariable (logistic regression) analysis. MRSA and MSSA were recovered from nasopharyngeal samples from 27 and 10 patients, respectively. Independent risk factors for MRSA colonization were: length-of-stay in the ICU (Odds Ratio [OR]=1.12, 95%Confidence Interval[CI]=1.06-1.19, p<0.001) and use of ciprofloxacin (OR=5.05, 95%CI=1.38-21.90, p=0.015). The use of levofloxacin had a protective effect (OR=0.08, 95%CI=0.01-0.55, p=0.01). Colonization with MSSA was positively associated with central nervous system disease (OR=7.45, 95%CI=1.33-41.74, p=0.02) and negatively associated with age (OR=0.94, 95%CI=0.90-0.99, p=0.01). In conclusion, our study suggests a role for both cross-transmission and selective pressure of antimicrobials in the spread of MRSA.

Evaluation of the antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus isolated from human infections

Multiresistant Staphylococcus aureus constitutes an important public health problem, especially in view of its possible spread in nosocomial environments. In the present work, we analyzed the susceptibility profile of 80 S. aureus stains from human infections resistant to at least 10 drugs. For this study, the techniques used were the disk method and minimum inhibitory concentration (MIC) of the following drugs: cefuroxime, ciprofloxacin, clindamycin, erythromycin, gentamycin, imipenem, oxacillin, rifampicin, tetracycline and vancomycin, according the criteria of the National Committee for Clinical Laboratory Standards (NCCLS). Methicillin was included in the antibiogram as a marker, which is usually used in drugs selection for the treatment of staphylococcal infections. Results indicated that the most effective drug was vancomycin. For the other 10 drugs, the percentage of resistant strains ranged from 85% to 93.75%. In relation to the MICs, it was observed that vancomycin (MIC 90% = 0.615ug/ml) was the most effective drug; followed by rifampicin (MIC 90% = 2.6ug/ml) and ciprofloxacin (MIC 90% = 26.6ug/ml). The drugs that showed the least effective activity were cefuroxime, clindamycin, erythromycin, gentamycin, and oxacillin. On the other hand, observation of β-lactamase production revealed that most of the methicillin-resistant strains produced β-lactamase (83.7%), potentiating the risks of nosocomial infections. In general, vancomycin still continues to be one of the most effective drugs for staphylococcal infections therapy.

Phototoxic effect of curcumin on methicillin-resistant Staphylococcus aureus and L929 fibroblasts

Photodynamic therapy has been investigated as an alternative method of killing pathogens in response to the multiantibiotic resistance problem. This study evaluated the photodynamic effect of curcumin on methicillin-resistant Staphylococcus aureus (MRSA) compared to susceptible S. aureus (MSSA) and L929 fibroblasts. Suspensions of MSSA and MRSA were treated with different concentrations of curcumin and exposed to light-emitting diode (LED). Serial dilutions were obtained from each sample, and colony counts were quantified. For fibroblasts, the cell viability subsequent to the curcumin-mediated photodynamic therapy was evaluated using the MTT assay and morphological changes were assessed by SEM analysis. Curcumin concentrations ranging from 5.0 to 20.0 μM in combination with any tested LED fluences resulted in photokilling of MSSA. However, only the 20.0 μM concentration in combination with highest fluence resulted in photokilling of MRSA. This combination also promoted an 80% reduction in fibroblast cell metabolism and morphological changes were present, indicating that cell membrane was the main target of this phototherapy. The combination of curcumin with LED light caused photokilling of both S. aureus strains and may represent an alternative treatment for eradicating MRSA, responsible for significantly higher morbidity and mortality and increased healthcare costs in institutions and hospitals. © 2012 Springer-Verlag London Ltd.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a burn unit from Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) poses a threat for patients in burn units. Studies that mix epidemiological designs with molecular typing may contribute to the development of strategies for MRSA control. We conducted a study including: molecular characterization of Staphylococcal Chromosome Cassette mecA (SCCmec), strain typing with pulsed field gel electrophoresis (PFGE) and detection of virulence genes, altogether with a case-case-control study that assessed risk factors for MRSA and for methicillin-susceptible S. aureus (MSSA), using S. aureus negative patients as controls. Strains were collected from clinical and surveillance cultures from October 2006 through March 2009. MRSA was isolated from 96 patients. Most isolates (94.8%) harbored SCCmec type III. SCCmec type IV was identified in isolates from four patients. In only one case it could be epidemiologically characterized as community-associated. PFGE typing identified 36 coexisting MRSA clones. When compared to MSSA (38 isolates), MRSA isolates were more likely to harbor two virulence genes: tst and lukPV. Previous stay in other hospital and admission to Intensive Care Unit were independent risk factors for both MRSA and MSSA, while the number of burn wound excisions was significantly related with the former (OR = 6.80, 95%CI = 3.54-13.07). In conclusion, our study found polyclonal endemicity of MRSA in a burn unit, possibly related to importing of strains from other hospitals. Also, it pointed out to a role of surgical procedures in the dissemination of MRSA strains. © 2013 Elsevier Ltd and ISBI. All rights reserved.

Molecular characterization of methicillin-resistant Staphylococcus aureus isolated from a Brazilian university hospital

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Methicillin-resistant Staphylococcus aureus of lineage ST398 as cause of mastitis in cows

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Molecular analysis of community-acquired methicillin-resistant Staphylococcus aureus isolated from skin and soft tissue infections, Botucatu Medical School, Brazil

Community acquired methicillin Staphylococcus aureus (CA-MRSA) was first reported in 1981, infecting people without risk factors. These strains harbor the Staphylococcal Cassette Chromosome mec (SCCmec) type IV, which contains the mecA gene codifying for methicillin resistance. CA-MRSA strains usually carry PVL (Panton-Valentine Leukocidin), a virulence factor responsible for tissue invasion, causing systemic infections and leading to serious complications. The aims of this work were to detect the mecA gene, SCCmec characterization and to detect the PVL gene of the S. aureus strains isolated from patients diagnosed with skin and soft tissue infections attending the Dermatology Service, of the Botucatu Medical School, Brazil. Among 127 collected samples, 66 (51.9%) were S. aureus and, from these, 7 (10.6%) harbored mecA gene, 3 (42%) with cassette type IV, and none of these samples carried the PVL gene, but it was detected in 10 (15.1%) samples of S. aureus methicillin sensitive (MSSA). Our study suggests the S. aureus strains that harbor PVL gene and MRSA are present in the community as important pathogens.

Eradication of a Mature Methicillin-Resistant Staphylococcus aureus (MRSA) Biofilm From Acrylic Surfaces

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Community-associated methicillin-resistant Staphylococcus aureus in non-outbreak skin infections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Community-associated methicillin-resistant Staphylococcus aureus in non-outbreak skin infections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)