Use of single-strand conformation polymorphism analysis to examine the variability of the rpoS sequence in environmental isolates of Salmonellae.
(25/1341)
The natural environment places its resident microflora under stress, which may often result in adaptation by the microflora in order to increase the probability of survival. One such mechanism that has been postulated involves rpoS, which encodes a sigma factor that is known to enhance survival upon exposure to stress. The present work aimed to examine the genetic variability of rpoS in a selection of Salmonella enterica subspecies environmental isolates with an automated single-strand conformation polymorphism analysis technique. The results indicated that sequence variation does occur and that these changes are mainly located in two areas: at the center and near the end of the coding region. The variability was generally at the single-base level, although one strain (S. arizonae) did demonstrate significant differences in nucleotide sequence. (+info)
Presence of alpha and a mating types in environmental and clinical collections of Cryptococcus neoformans var. gattii strains from Australia.
(26/1341)
Cryptococcus neoformans var. gattii lives in association with certain species of eucalyptus trees and is a causative agent of cryptococcosis. It exists as two mating types, MATalpha and MATa, which is determined by a single-locus, two-allele system. In the closely related C. neoformans var. neoformans, the alpha mating type has been found to outnumber its a counterpart by at least 30:1, but there have been very limited data on the proportions of each mating type in C. neoformans var. gattii. In the present study, specific PCR primers were designed to amplify two separate alpha-mating-type genes from C. neoformans var. gattii strains. These were used to survey for the presence of the two mating types in clinical and environmental collections of C. neoformans var. gattii strains from Australia. Sixty-eight of 69 clinical isolates produced both alpha mating type-specific bands and were assumed to be of the alpha mating type. The majority of environmental isolates were also of the alpha mating type, but the a mating type was located in two separate areas. In one area, the a mating type outnumbered the alpha mating type by 27:2, but in the second area, the ratio of the two mating types was close to the 50:50 ratio expected for sexual recombination. (+info)
Molecular epidemiology of ceftazidime-resistant gram-negative bacilli on inanimate surfaces and their role in cross-transmission during nonoutbreak periods.
(27/1341)
We described the molecular epidemiology of expanded-spectrum cephalosporin-resistant gram-negative bacilli (RGN) recovered from inanimate surfaces. RGN were isolated from 9% of environmental cultures. Numerous species, each with multiple unique strains, were recovered. Epidemiological links between environmental, personnel, and patient strains suggested the exogenous acquisition of RGN from the hospital environment. (+info)
Amplified fragment length polymorphism fingerprinting of Pseudomonas strains from a poultry processing plant.
(28/1341)
Molecular typing has been used previously to identify and trace dissemination of pathogenic and spoilage bacteria associated with food processing. Amplified fragment length polymorphism (AFLP) is a novel DNA fingerprinting technique which is considered highly reproducible and has high discriminatory power. This technique was used to fingerprint 88 Pseudomonas fluorescens and Pseudomonas putida strains that were previously isolated from plate counts of carcasses at six processing stages and various equipment surfaces and environmental sources of a poultry abattoir. Clustering of the AFLP patterns revealed a high level of diversity among the strains. Six clusters (clusters I through VI) were delineated at an arbitrary Dice coefficient level of 0.65; clusters III (31 strains) and IV (28 strains) were the largest clusters. More than one-half (52.3%) of the strains obtained from carcass samples, which may have represented the resident carcass population, grouped together in cluster III. By contrast, 43.2% of the strains from most of the equipment surfaces and environmental sources grouped together in cluster IV. In most cases, the clusters in which carcass strains from processing stages grouped corresponded to the clusters in which strains from the associated equipment surfaces and/or environmental sources were found. This provided evidence that there was cross-contamination between carcasses and the abattoir environment at the DNA level. The AFLP data also showed that strains were being disseminated from the beginning to the end of the poultry processing operation, since many strains associated with carcasses at the packaging stage were members of the same clusters as strains obtained from carcasses after the defeathering stage. (+info)
Generalized transduction of small Yersinia enterocolitica plasmids.
(29/1341)
To study phage-mediated gene transfer in Yersinia, the ability of Yersinia phages to transduce naturally occurring plasmids was investigated. The transduction experiments were performed with a temperate phage isolated from a pathogenic Yersinia enterocolitica strain and phage mixtures isolated from sewage. Small plasmids (4.3 and 5.8 kb) were transduced at a frequency of 10(-5) to 10(-7)/PFU. However, we could not detect the transduction of any indigenous virulence plasmid (ca. 72 kb) in pathogenic Yersinia strains. Transductants obtained by infection with the temperate phage were lysogenic and harbored the phage genome in their chromosomes. (+info)
Isolation of nitrogen-fixing bacteria containing molybdenum-independent nitrogenases from natural environments.
(30/1341)
Seven diazotrophs that grow well under Mo-deficient, N(2)-fixing conditions were isolated from a variety of environments. These isolates fall in the gamma subdivision of the class Proteobacteria and have genes that encode the Mo nitrogenase (nitrogenase 1) and the V nitrogenase (nitrogenase 2). Four of the isolates also harbor genes that encode the iron-only nitrogenase (nitrogenase 3). (+info)
Lipopolysaccharide chemotypes of Burkholderia cepacia.
(31/1341)
Burkholderia cepacia is an important pathogen in patients with cystic fibrosis (CF) and much is now known of its epidemiology. In contrast, its virulence mechanisms are poorly understood. The lipopolysaccharide (LPS) of B. cepacia, a well-recognised virulence factor of other gram-negative bacteria, is known to be strongly endotoxic in vitro. The aim of this study was to observe if there were any links between the structure of B. cepacia LPS and virulence. This has been investigated by polyacrylamide gel electrophoresis and immunoblotting to define the chemotype and antigenic cross reactivity of B. cepacia LPS. Strains (16) belonging to different genomovars of the B. cepacia complex were selected to represent epidemic and non-epidemic clinical isolates and environmental strains. All strains belonging to genomovars I and II (the latter now renamed B. multivorans) had smooth LPS. However, isolates belonging to genomovar III, the group to which most of the epidemic CF isolates belong - including the highly transmissible strain (ET 12) which has been found in both the UK and North America - were of either rough or smooth LPS chemotype. In this study, B. cepacia J2315 represents the ET 12 lineage, and has a rough chemotype. Rabbit antiserum raised to strain J2315 revealed that the LPS core of this strain was antigenically related to some but not all other genomovar III strains, but it also cross-reacted strongly with all B. multivorans (genomovar II) and most genomovar I strains. Intra-strain phenotypic variation was demonstrated between bacteria grown in broth or on solid agar with a concomitant variation in antigenic cross reactivity. There was no clear evidence to associate any particular LPS phenotype with epidemic or non-epidemic strains, but changes in phenotype in vitro may provide clues to the survival and adaptability of B. cepacia in hostile environments and possibly to its ability to produce an inflammatory response in vivo. (+info)
Molecular typing of Legionella pneumophila serogroup 1 isolates from patients and the nosocomial environment by arbitrarily primed PCR and pulsed-field gel electrophoresis.
(32/1341)
The ubiquity of Legionella pneumophila in aquatic habitats means that epidemiological evaluation is important for the investigation and control of nosocomial outbreaks of legionellosis. Pulsed-field gel electrophoresis (PFGE) of chromosomal DNA following digestion with SfiI is considered to be one of the most discriminative methods for detecting DNA polymorphisms amongst L. pneumophila serogroup 1 (Lp1) isolates. This paper describes an arbitrarily primed PCR (AP-PCR) method with three different primers (20-mers) for detecting DNA polymorphisms of Lp1 isolates. The AP-PCR assay was compared with PFGE analysis. Both experimental methods were found to have good discriminatory power (discrimination index of 98% and 94.3%, respectively) with 27 unrelated isolates from different geographical areas collected between 1987 and 1997. Furthermore, when the AP-PCR was used in the epidemiological investigation of nosocomial cases of infection, convergent results with the three primers allowed an epidemiological link to be established between isolates from patients and their environment. The AP-PCR method, which is rapid and easy to perform, gave results at least as discriminatory as those obtained with the PFGE method and is proposed for use in the molecular typing of Lp1 outbreaks. (+info)