ABSTRACT
Bacteria were isolated from an industrial water circuit in the Netherlands. These strains were identified using API 20 NE as possible, or likely, Burkholderia pseudomallei. With VITEK 2 some of these strains scored 'low discrimination' for Francisella tularensis, amongst others. A total of twenty-six strains were assigned to the species Pseudomonas brenneri, Pseudomonas gessardii or Pseudomonas proteolytica. Because of the possibility of misidentification of these environmental species as medical- and public-health relevant B. pseudomallei and F. tularensis, an emended description, based on tests results more customarily used in clinical laboratories, was suitable. For this reason, the strains in this study, including the type strains DSM 15294T, DSM 17152T and DSM 15321T, were subjected to a polyphasic identification procedure. This procedure consisted of multiple phenotypic tests, fatty acid analysis, 16S rDNA sequence analysis, matrix-assisted laser desorption ionization time-of-flight mass spectronomy and various species-specific molecular tests. Based on the results of the polyphasic procedures, the species descriptions of P. brenneri, P. gessardii and P. proteolytica have been emended.
Subject(s)
Burkholderia pseudomallei/classification , Francisella tularensis/classification , Phylogeny , Pseudomonas/classification , Water Microbiology , Bacterial Typing Techniques , Burkholderia pseudomallei/isolation & purification , DNA, Bacterial/genetics , Fatty Acids/chemistry , Francisella tularensis/isolation & purification , Netherlands , Pseudomonas/isolation & purification , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA , Species Specificity , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Water SupplyABSTRACT
Mycobacterium marinum causes a systemic tuberculosis-like disease in a large number of poikilothermic animals and is used as a model for mycobacterial pathogenesis. In the present study, we infected zebra fish (Danio rerio) with different strains of M. marinum to determine the variation in pathogenicity. Depending on the M. marinum isolate, the fish developed an acute or chronic disease. Acute disease was characterized by uncontrolled growth of the pathogen and death of all animals within 16 days, whereas chronic disease was characterized by granuloma formation in different organs and survival of the animals for at least 4 to 8 weeks. Genetic analysis of the isolates by amplified fragment length polymorphism showed that M. marinum strains could be divided in two clusters. Cluster I contained predominantly strains isolated from humans with fish tank granuloma, whereas the majority of the cluster II strains were isolated from poikilothermic species. Acute disease progression was noted only with strains belonging to cluster I, whereas all chronic-disease-causing isolates belonged to cluster II. This difference in virulence was also observed in vitro: cluster I isolate Mma20 was able to infect and survive more efficiently in the human macrophage THP-1 and the carp leukocyte CLC cell lines than was the cluster II isolate Mma11. We conclude that strain characteristics play an important role in the pathogenicity of M. marinum. In addition, the correlation between genetic variation and host origin suggests that cluster I isolates are more pathogenic for humans.
Subject(s)
Genetic Variation , Mycobacterium Infections, Nontuberculous/microbiology , Mycobacterium marinum/classification , Mycobacterium marinum/pathogenicity , Acute Disease , Animals , Carps , Cell Line , Chronic Disease , Humans , Male , Mycobacterium Infections, Nontuberculous/mortality , Mycobacterium Infections, Nontuberculous/physiopathology , Mycobacterium marinum/genetics , Polymorphism, Restriction Fragment Length , Virulence , ZebrafishABSTRACT
A premature infant in a neonatal intensive care unit (NICU) developed a bloodstream infection caused by coagulase-negative staphylococci (CoNS) sensitive to vancomycin. The infection persisted for 3 weeks, despite therapy with vancomycin and replacement of all intravenous catheters. The neonate died due to necrotizing enterocolitis which developed during the ongoing sepsis. We screened this strain and 216 other strains of CoNS from cultures of blood obtained from neonates between 1997 and 2000 for heteroresistance to vancomycin. Forty-eight isolates, including the strain that caused ongoing sepsis, proved heteroresistant. All isolates were identified as Staphylococcus capitis and were identical, just as their resistant stable subcolonies were, when they were genetically fingerprinted by amplified-fragment length polymorphism analysis. The heteroresistant phenotype of this endemic strain was confirmed by population analysis. We conclude that heteroresistance to vancomycin occurs in S. capitis and might be the cause of therapeutic failures in NICUs. Moreover, heteroresistant strains can become endemic in such units.
