RESUMO
OBJECTIVES: Information on genetic determinants of chlorhexidine tolerance (qacA carriage and MIC) in vitro is available, although evidence of the clinical impact and mechanisms remain poorly understood. We investigated why, following chlorhexidine intervention, prevalent epidemic MRSA ST22 and ST36 clones declined at an ICU, whilst an ST239-TW clone did not. The chlorhexidine tolerant ST239-TW phenotypes were assessed for their protein binding, cell adhesion and intracellular uptake potential. METHODS: Six ST22, ST36 and ST239-TW bloodstream infection isolates with comparable chlorhexidine MICs were selected from a 2-year outbreak in an ICU at Guy's and St. Thomas' Hospital. Isolates were tested for fibrinogen and fibronectin binding, and adhesion/internalization into human keratinocytes with and without biocide. RESULTS: Binding to fibrinogen and fibronectin, adhesion and intracellular uptake within keratinocytes (Pâ¯<â¯0.001) and intracellular survival in keratinocytes under chlorhexidine pressure (ST22 3.18%, ST36 4.57%â¯vs ST239-TW 12.79%; Pâ¯<â¯0.0001) was consistently higher for ST239-TW. CONCLUSIONS: We present evidence that MRSA clones with similarly low in vitro tolerance to chlorhexidine exhibit different in vivo susceptibilities. The phenomenon of S. aureus adhesion and intracellular uptake into keratinocytes could therefore be regarded as an additional mechanism of chlorhexidine tolerance, enabling MRSA to evade infection control measures.
Assuntos
Aderência Bacteriana/efeitos dos fármacos , Clorexidina/farmacologia , Desinfetantes/farmacologia , Queratinócitos/microbiologia , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Linhagem Celular , Citoplasma/microbiologia , Fibrinogênio/metabolismo , Fibronectinas/metabolismo , Humanos , Controle de Infecções , Queratinócitos/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Ligação ProteicaAssuntos
DNA Bacteriano/análise , Endoftalmite/diagnóstico , Infecções Oculares Bacterianas/diagnóstico , Bactérias Gram-Positivas/genética , Infecções por Bactérias Gram-Positivas/diagnóstico , RNA Ribossômico 16S/genética , Adulto , Técnicas de Tipagem Bacteriana , Endoftalmite/etiologia , Infecções Oculares Bacterianas/microbiologia , Infecções por Bactérias Gram-Positivas/microbiologia , Humanos , Hospedeiro Imunocomprometido , Masculino , Reação em Cadeia da Polimerase , Tomografia de Coerência ÓpticaRESUMO
BACKGROUND: Human rabies infection continues to be a significant public health burden globally, and is occasionally imported to high income settings where the Milwaukee Protocol for intensive care management has recently been employed, with limited success in improving survival. Access to molecular diagnostics, pre- and post-mortem, and documentation of pathophysiological responses while using the Milwaukee protocol, can add useful insights for the future of rabies management. CASE PRESENTATION: A 58-year-old British Asian woman was referred to a regional general hospital in the UK with hydrophobia, anxiety and confusion nine weeks after receiving a dog bite in North West India. Nuchal skin biopsy, saliva, and a skin biopsy from the site of the dog bite wound, taken on the day of admission, all demonstrated the presence of rabies virus RNA. Within 48 hours sequence analysis of viral RNA confirmed the diagnosis and demonstrated that the virus was a strain closely related to canine rabies viruses circulating in South Asia. Her condition deteriorated rapidly with increased agitation and autonomic dysfunction. She was heavily sedated and intubated on the day after admission, treated according to a modified Milwaukee protocol, and remained stable until she developed heart block and profound acidosis and died on the eighth day. Analysis of autopsy samples showed a complete absence of rabies neutralizing antibody in cerebrospinal fluid and serum, and corresponding high levels of virus antigen and nucleic acid in brain and cerebrospinal fluid. Quantitative PCR showed virus was also distributed widely in peripheral tissues despite mild or undetectable histopathological changes. Vagus nerve branches in the heart showed neuritis, a probable Negri body but no demonstrable rabies antigen. CONCLUSION: Rapid molecular diagnosis and strain typing is helpful in the management of human rabies infection. Post-mortem findings such as vagal neuritis highlight clinically important effects on the cardiovascular system which are typical for the clinical course of rabies in humans. Management guided by the Milwaukee protocol is feasible within well-resourced intensive care units, but its role in improving outcome for canine-derived rabies remains theoretical.
Assuntos
Mordeduras e Picadas/complicações , Vírus da Raiva/isolamento & purificação , Raiva/diagnóstico , Raiva/patologia , Animais , Cães , Evolução Fatal , Feminino , Humanos , Índia , Pessoa de Meia-Idade , RNA Viral/isolamento & purificação , Viagem , Reino UnidoAssuntos
Herpes Zoster/virologia , Herpesvirus Humano 3 , Meningite Viral/virologia , Idoso , DNA Viral/líquido cefalorraquidiano , Cavidade Pulpar/cirurgia , Feminino , Herpes Zoster/líquido cefalorraquidiano , Herpes Zoster/diagnóstico , Humanos , Meningite Viral/líquido cefalorraquidiano , Meningite Viral/diagnóstico , Retina/virologia , Úvea/virologia , Ativação ViralRESUMO
The 3.1-Mb genome of an outbreak methicillin-resistant Staphylococcus aureus (MRSA) strain (TW20) contains evidence of recently acquired DNA, including two large regions (635 kb and 127 kb). The strain is resistant to a wide range of antibiotics, antiseptics, and heavy metals due to resistance genes encoded on mobile genetic elements and also mutations in housekeeping genes.
Assuntos
Farmacorresistência Bacteriana Múltipla/genética , Genoma Bacteriano/genética , Staphylococcus aureus Resistente à Meticilina/genética , Antibacterianos/farmacologia , Anti-Infecciosos Locais/farmacologia , Metais Pesados/toxicidade , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Modelos Genéticos , Dados de Sequência MolecularRESUMO
Multilocus sequence typing (MLST) and multi-strain microarray analysis have shown that most human Staphylococcus aureus strains belong to ten dominant clonal complexes (CCs) or lineages, each with unique surface architecture. Meticillin-resistant S. aureus (MRSA) strains currently belong to six of these lineages (CC1, CC5, CC8, CC22, CC30 and CC45), each of which has independently acquired mobile genetic elements (MGEs) carrying antibiotic resistance genes. MLST and microarrays are expensive and time consuming methods for routine determination of S. aureus lineage. A restriction-modification (RM) test has now been developed that is rapid, simple, inexpensive and accurately determines lineage of hospital-acquired MRSA. The RM test is based on three PCRs for hsdS gene variants, as hsdS genes likely control the independent evolution of S. aureus lineages. The RM test correctly identified 102 MRSA isolates as belonging to one of the six lineages/CCs. Real-time MRSA typing can be used to identify and track changes in local MRSA outbreaks, and provide support for targeting infection control strategies. Simple and accurate typing methods will also support large scale epidemiological studies, and could lead to greater understanding of the carriage, spread and virulence of different MRSA lineages.
Assuntos
Infecção Hospitalar/microbiologia , Desoxirribonucleases de Sítio Específico do Tipo I/genética , Resistência a Meticilina , Reação em Cadeia da Polimerase/métodos , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/classificação , Enzimas de Restrição-Modificação do DNA/genética , DNA Bacteriano/genética , Humanos , Epidemiologia Molecular/métodos , Sensibilidade e Especificidade , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/genética , Staphylococcus aureus/isolamento & purificaçãoRESUMO
BACKGROUND: Patients in intensive care units are at high risk of developing methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. We report an epidemiological and bacterial genomic analysis of a 2-year outbreak in an intensive care unit of a variant of MRSA sequence type 239 (hereafter designated TW). METHODS: A cohort study was conducted to compare risk factors for MRSA bacteremia in patients who acquired TW versus patients who acquired non-TW strains of MRSA. Genetic analysis of TW was performed using multilocus sequence typing and microarray analysis. RESULTS: Patients who acquired TW were more likely than patients who acquired non-TW strains of MRSA to have MRSA isolated from blood samples (47% vs. 13%; P<.001) and to have MRSA-positive vascular access device-sample cultures (59% vs. 26%; P<.001), but less likely to have MRSA isolated from screening swab samples (30% vs. 71%; P<.001). This increased rate of TW bacteremia was confined to the first week after acquisition of TW infection. Using Cox regression analysis, the adjusted hazard ratio for bacteremia with TW was 4.5 times that of non-TW strains of MRSA (95% confidence interval, 2.25-9.00; P<.001). Microarray analysis revealed that TW had accumulated all detectable mobile genetic elements that were variably expressed by other epidemic strains of MRSA sequence type 239 in the United Kingdom. CONCLUSIONS: To our knowledge, this is the first report to provide direct evidence that strains of MRSA can differ in their ability to cause bacteremia. Further genetic and in vitro analysis of the TW strain may provide insight into the mechanism of vascular access device-related bacteremia in the intensive care unit environment.