Impact of plasmids, including those encodingVirB4/D4 type IV secretion systems, on Salmonella enterica serovar Heidelberg virulence in macrophages and epithelial cells (original) (raw)
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Reviews in Medical Microbiology, 2011
Nontyphoid serovars of Salmonella enterica are one of the leading causes of bacterial food-borne disease. Most human infections are confined to the small intestine and associated with inflammatory diarrhoea. However, bacteria can also spread beyond the intestine causing focal or systemic infections, particularly in infants, the elderly and immuno-compromised hosts. Although usually not required, antimicrobial therapy is mandatory for the control of invasive infections and for people with recognized risk factors. A limited number of nontyphoid serovars carry virulence plasmids, which are actively evolving through loss and/or acquisition of genetic information. Of particular interest is the capture of genes conferring resistance to antimicrobials, which can result from cointegration with resistance plasmids but is more commonly mediated by mobile genetic elements, such as insertion sequences, transposons and integrons. Resistance plasmids carrying virulence genes of serovar specific plasmids, including the spv region, were also detected. This review will focus on hybrid virulence-resistance plasmids found in Typhimurium and its monophasic 4,5,12:i:-variant, Enteritidis and Choleraesuis, which rank among the most common and/or invasive nontyphoid serovars. The epidemiology of these plasmids, the mechanisms underlying their emergence and evolution, as well as the consequences for both the pathogen and its host, will be considered.
Veterinary Research Communications, 2003
Twenty-four strains of Salmonella enteritidis, isolated from several outbreaks of salmonellosis from different poultry farms in India, were checked for the plasmid profile and detection of virulence gene(s) by PCR. Most of the strains contained only a single plasmid of 55 kb. Additional plasmids of 23.2 kb and 8.7 kb were seen in one of the strains, and another strain carried only two plasmids of 23.2 kb and 8.7 kb. Four strains did not carry any plasmid. PCR amplification showed the presence of virulence-associated genes in all the isolates harbouring the 55 kb plasmid. Intraperitoneal inoculation of mice, with most of the strains carrying the 55 kb plasmid, caused 100% mortality. Most strains lacking the 55 kb plasmid were avirulent. In chickens, oral inoculation of the S. enteritidis strains carrying the 55 kb plasmid produced 40–100% mortality, with characteristic signs of salmonellosis. Oral inoculation of strains lacking the 55 kb plasmid did not cause any mortality. Hence, it appears that the large plasmid of S. enteritidis probably contributes towards virulence in mice and chickens.
Pathogens and Global Health, 2019
Infections caused by non-typhoidal Salmonella (NTS) are common around the world, with high morbidity and mortality rates recorded annually. Salmonella serovars harbor plasmids of various sizes which may play roles in antibiotic resistance and virulence. The aim of this study was to profile and determine the role of plasmids in ciprofloxacin resistance and virulence of Salmonella serovars. Using alkaline lysis method 25 NTS serovars from food animals and humans were assayed for plasmids. Isolates ability to resist healthy human serum, bind congo red, produce hemolysin and susceptibility to ciprofloxacin before and after plasmid curing were evaluated. Mobility of plasmids was determined by conjugation. Fifteen (60%) of the 25 Salmonella serovars harbored plasmids with sizes ranging from 0.4 to 38.4 kb. S. Budapest serovars harbored 5-9 plasmids, while S. Essen and S. Mura had six plasmids each. S. Chomedey and a S. Budapest serovar were sensitive to ciprofloxacin after plasmid curing while other serovars remained resistant to ciprofloxacin after plasmid curing. All Salmonella isolates had the ability to withstand human serum before and after plasmid curing, however, some serovars lost their ability to bind congo red after plasmid curing. All Salmonella isolates that initially displayed hemolysin activity retained their ability after curing. Thirteen (86.7%) of the 15 serovars that harbored plasmids conjugatively transferred their plasmids to E. coli K-12 (DH5α). Having Salmonella serovars that harbor transferrable plasmids in the food chain can drive antibiotic resistance and enhanced virulence of otherwise less virulence strains.
Research in Microbiology, 2000
The Salmonella plasmid virulence genes (spv) are commonly found on plasmids contained in a small number of serotypes of Salmonella belonging to subspecies I, where they are important for survival within macrophages and the establishment of successful systemic infection. However, in this study, spv genes were detected by the polymerase chain reaction in the chromosome of a plasmid-free strain of S. IV 16:z 4 , z 32 :-(Salmonella subspecies IV). The full range of spv genes (spvR, spvA, spvB, spvC and spvD) was demonstrated, but a 216-bp deletion, accompanied by an insertion of 59-bp cryptic DNA, was present in spvA. S. IV 16:z 4 , z 32 :-was avirulent in mice and did not become virulent with the introduction of a fully functionally serotype-associated virulence plasmid (SAP) from S. typhimurium. By use of an spvRAB'-chloramphenicol acetyl transferase fusion gene, it was demonstrated that S. IV 16:z 4 , z 32 :-did not express the spv genes. Salmonella subspecies IV is monophasic, and in phylogenetic analyses it clusters distantly to Salmonella subspecies I, where all the serotypes that normally carry SAPs are found. The mechanisms by which spv genes have been transferred to this serotype remain unknown.
Applied and Environmental Microbiology, 2009
Salmonella enterica , a leading cause of food-borne gastroenteritis worldwide, may be found in any raw food of animal, vegetable, or fruit origin. Salmonella serovars differ in distribution, virulence, and host specificity. S almonella enterica serovar Kentucky, though often found in the food supply, is less commonly isolated from ill humans. The multidrug-resistant isolate S . Kentucky CVM29188, isolated from a chicken breast sample in 2003, contains three plasmids (146,811 bp, 101,461 bp, and 46,121 bp), two of which carry resistance determinants (pCVM29188_146 [ strAB and tetRA ] and pCVM29188_101 [ bla CMY-2 and sugE ]). Both resistance plasmids were transferable by conjugation, alone or in combination, to S. Kentucky, S almonella enterica serovar Newport, and E scherichia coli recipients. pCVM29188_146 shares a highly conserved plasmid backbone of 106 kb (>90% nucleotide identity) with two virulence plasmids from a vian p athogenic E scherichia c oli strains (pAPEC-O1-ColBM ...
Food Research International, 2012
During a screening of Salmonella enterica in foods of animal origin four isolates of serovar Typhimurium carrying hybrid virulence-resistance plasmids were detected. Three of them, one from pork and two from chicken meat, contained pUO-StVR2, a derivative of the pSLT virulence plasmid with the bla OXA-1 , catA1, aadA1, sulI and tet(B) genes, which confer resistance to ampicillin, chloramphenicol, streptomycin-spectinomycin, sulfonamides and tetracycline, respectively. The fourth isolate, from pork, harbored a pUO-StVR2 variant (termed ν8) with an additional dfrA10 gene responsible for resistance to trimethoprim. This gene is part of the orf513-dfrA10-qacEΔ1-sul1 element characteristically found in complex class 1 integrons. Pulsed-field gel electrophoresis identified two XbaI-BlnI combined profiles: X2-B2 generated from the three pUO-StVR2 isolates, and X12-B17 shown by the pUO-StVR2-ν8 isolate. The same profiles have also been found in clinical and ill pig isolates, supporting chicken and pork meat as vehicles for transmission of Typhimurium carrying pUO-StVR2-like plasmids.