Expression study by real-time quantitative RT-PCR of the Salmonella typhimurium mntH gene

The aim of our study was to compare the mntH expression of different Salmonella Typhimurium strains and other Salmonella serovars with real-time RT-PCR. Following the mntH expression in function of the growth showed that the mntH expression of S. Typhimurium is growth dependent. A strong decrease of the mntH expression is noticed when the growth reaches 1.78 108 CFU/ml. After induction with EDTA or H2O2, variations between different S. Typhimurium strains were observed. For some S. Typhimurium strains a 10 to 20 times higher mntH expression was noticed after H2O2 induction. The EDTA induction was for most strains lower (5 to 10 times) but also variations between different strains were observed. The other Salmonella serovars were strongly induced after H2O2 but not after EDTA induction

The prevalence of Salmonella, Campylobacter and VTEC in pig farms

Four different pig farms were sampled for the prevalence of Salmonella, Campylobacter and VTEC. From a total of 215 rectal samples of individual pigs, 15 rectal samples taken from animals at the same farm were positive for Salmonella. The Salmonella status of the pigs at this farm differed from one age group to another. S. Typhimurium was isolated from all the rectal samples and S. Typhimurium and S. Schwarzengrund were isolated from the environment. On two other farms Salmonella was only present in the environment with S. London and S. Typhimurium as serotypes. With cut-off value %OD\u3e 40 in the ELISA we found a good correlation with the Salmonella status of the farm. The presence of Campylobacter was tested in 150 rectal swabs, 51 of these, spread over the four farms, turned out positive. All the strains were identified as Campylobacter coli by a species-specific PCR. To determine if pigs are a reservoir of VTEC a total of 289 samples were screened for the presence of VTEC and 54 strains were isolated that each carried one virulence gene. Thirty-one strains carried the vt2e variant of the vt2 gene, four strains harboured the hly A gene and 19 the eaeA gene

SPI-2 of Salmonella Typhimurium is not necessary for long term colonization of pigs

Unravelling the role of Salmonella virulence factors in the porcine host could greatly contribute to the development of control measures such as vaccination. The virulence genes located on the Salmonella Pathogenicity Island 2 (SPI-2) are indispensable for the induction of systemic disease and persistence in BALB/c mice. The role of this pathogenicity island in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. Therefore, in the present study, the interactions of a porcine field strain of Salmonella Typhimurium and a non-polar isogenic SPI-2 (D-ssrA) deletion mutant were compared in both in vitro and in vivo models. The ssrA mutant strain displayed decreased SPI-2 expression levels in vitro and was attenuated in a mouse model after oral inoculation. No difference was seen in the expression of SPI-1 related virulence genes. Through flowcytometric analysis, the ssrA mutant strain was found to be moderately attenuated in intracellular replication in porcine macrophages in vitro. In an infection experiment, 2 groups of 10 piglets were orally inoculated with the wild type or the ssrA mutant strain. The infection of the animals inoculated with the ssrA mutant strain followed a similar course as the animals infected with the wild type strain. At days 5 and 28 post inoculation, the animals of both groups were infected to the same extent in the gut and gut-associated lymphoid tissue, as well as in the mternal organs. These results suggest that SPI-2 of Salmonella Typhimurium may not contribute to the colonization of pigs to the same extent as it contributes to the colonization of BALB/c mice

An awkward fishing expedition

We report the case of a patient, among a group of five, in a small outbreak of histamine fish poisoning (HFP). The epidemic character of the ailment led us to the correct diagnosis. In this case, the diagnosis was also associated with a Kounis syndrome (KS). Literature concerning this subject is reviewed, reporting recent physiopathological data

A Reservoir of Drug-Resistant Pathogenic Bacteria in Asymptomatic Hosts

The population genetics of pathogenic bacteria has been intensively studied in order to understand the spread of disease and the evolution of virulence and drug resistance. However, much less attention has been paid to bacterial carriage populations, which inhabit hosts without producing disease. Since new virulent strains that cause disease can be recruited from the carriage population of bacteria, our understanding of infectious disease is seriously incomplete without knowledge on the population structure of pathogenic bacteria living in an asymptomatic host. We report the first extensive survey of the abundance and diversity of a human pathogen in asymptomatic animal hosts. We have found that asymptomatic swine from livestock productions frequently carry populations of Salmonella enterica with a broad range of drug-resistant strains and genetic diversity greatly exceeding that previously described. This study shows how agricultural practice and human intervention may lead and influence the evolution of a hidden reservoir of pathogens, with important implications for human health

Differential Gene Expression by RamA in Ciprofloxacin-Resistant Salmonella Typhimurium

Overexpression of ramA has been implicated in resistance to multiple drugs in several enterobacterial pathogens. In the present study, Salmonella Typhimurium strain LTL with constitutive expression of ramA was compared to its ramA-deletion mutant by employing both DNA microarrays and phenotype microarrays (PM). The mutant strain with the disruption of ramA showed differential expression of at least 33 genes involved in 11 functional groups. The study confirmed at the transcriptional level that the constitutive expression of ramA was directly associated with increased expression of multidrug efflux pump AcrAB-TolC and decreased expression of porin protein OmpF, thereby conferring multiple drug resistance phenotype. Compared to the parent strain constitutively expressing ramA, the ramA mutant had increased susceptibility to over 70 antimicrobials and toxic compounds. The PM analysis also uncovered that the ramA mutant was better in utilization of 10 carbon sources and 5 phosphorus sources. This study suggested that the constitutive expression of ramA locus regulate not only multidrug efflux pump and accessory genes but also genes involved in carbon metabolic pathways