RESUMEN
Mycobacterium marinum, a bacterium found in freshwater and saltwater, can infect persons with direct exposure to fish or aquariums. During December 2013, the New York City Department of Health and Mental Hygiene learned of four suspected or confirmed M. marinum skin or soft tissue infections (SSTIs) among persons who purchased whole fish from Chinese markets. Ninety-eight case-patients with non-tuberculous mycobacteria (NTM) SSTIs were identified with onset June 2013-March 2014. Of these, 77 (79%) were female. The median age was 62 years (range 30-91). Whole genome sequencing of clinical isolates revealed two main clusters and marked genetic diversity. Environmental samples from distributors yielded NTM though not M. marinum. We compared 56 case-patients with 185 control subjects who shopped in Chinese markets, frequency-matched by age group and sex. Risk factors for infection included skin injury to the finger or hand (odds ratio [OR]: 15·5; 95% confidence interval [CI]: 6·9-37·3), hand injury while preparing fish or seafood (OR 8·3; 95% CI 3·8-19·1), and purchasing tilapia (OR 3·6; 95% CI 1·1-13·9) or whiting (OR 2·7; 95% CI 1·1-6·6). A definitive environmental outbreak source was not identified.
Asunto(s)
Brotes de Enfermedades , Infecciones por Mycobacterium no Tuberculosas/epidemiología , Mycobacterium marinum/aislamiento & purificación , Enfermedades Cutáneas Bacterianas/epidemiología , Infecciones de los Tejidos Blandos/epidemiología , Adulto , Anciano , Anciano de 80 o más Años , Animales , Estudios de Casos y Controles , Femenino , Peces , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Infecciones por Mycobacterium no Tuberculosas/microbiología , Ciudad de Nueva York/epidemiología , Enfermedades Cutáneas Bacterianas/microbiología , Infecciones de los Tejidos Blandos/microbiologíaRESUMEN
Salmonella typhimurium invasion of nonphagocytic cells requires the expression of a type III secretion system (TTSS) encoded within Salmonella pathogenicity island 1 (SPI1). TTSS gene transcription is activated in response to environmental signals and requires transcriptional regulators encoded within (HilA) and outside (SirA) SPI1. Two unique loci, sirB and sirC, which contribute to SPI1 gene transcription were defined. sirC is an SPI1-encoded transcription factor of the AraC family that contributes to the invasive phenotype. sirB is required for maximal expression of sirC and consists of two open reading frames located near kdsA, a gene involved in lipopolysaccharide biosynthesis. sirC expression, unlike expression of other SPI1 genes, does not require HilA. Overexpression of sirC or sirA restores expression of a subset of SPI1 genes, including invF and sspC, in the absence of HilA. These data define roles for SirC and SirA as part of a HilA-independent pathway to SPI1 gene expression. We postulate that HilA-independent activation of inv expression is important for efficient assembly and function of the SPI1 TTSS.
Asunto(s)
Proteínas Bacterianas/genética , Regulación Bacteriana de la Expresión Génica , Salmonella typhimurium/patogenicidad , Transactivadores/fisiología , Transcripción Genética/genética , Proteínas Bacterianas/fisiología , Genes araC/genética , Modelos Genéticos , Datos de Secuencia Molecular , Mutación , Sistemas de Lectura Abierta/genética , Operón/genética , Fenotipo , Regulón/genética , Salmonella typhimurium/genética , Homología de Secuencia de Aminoácido , Transactivadores/genética , Factores de Transcripción/genética , Factores de Transcripción/fisiologíaRESUMEN
Pseudomonas aeruginosa is a common respiratory tract pathogen that causes serious infections in patients with cystic fibrosis. A number of putative virulence factors have been characterized in several laboratories, and some have been implicated in human infections, based on criteria such as the phenotype of isolates from infected patients, an immune response to a particular antigenic factor, and the effect of a virulence factor on infectivity in an animal model. We have developed a series of genetic tools to study the selective regulation of expression of P. aeruginosa genes during interactions of the pathogen with host tissues. These tools are based on direct enrichment of bacteria, when a particular promoter is induced or repressed. We have found that interaction of bacteria with mucus from patients with cystic fibrosis results in marked induction of expression of several genes, including one that encodes a lipopolysaccharide biosynthetic enzyme, a gene for a protein responsible for uptake of the ferric pyochelin siderophore, and a new gene homologous with a class of iron-responsive repressors. The tools described here are useful for identification of induced or repressed genes in various animal models of infection or in controlled laboratory conditions that mimic natural infections of humans. Such genes might not be detectable when bacteria are cultured in laboratory conditions, and these tools are therefore useful for general probing of a bacterial genome for genes regulated during different stages of infection.