Brote de gastroenteritis en una guardería causado por una cepa de Salmonella enterica serovar Typhimurium portadora del plásmido híbrido de resistencia-virulencia pUO-StVR2
Epidemiological and microbiological study of a salmonellosis outbreak, affecting 22 children in a nursery school in Oviedo (Spain).
Attack rates and epidemic curves were determined, and bacterial typing methods were applied.
The outbreak was attributed to a Salmonella enterica serovar Typhimurium strain, belonging to an emergent type characterized by the presence of a hybrid virulence-resistance plasmid of 125-130 kb, named pUO-StVR2. The attack rate of confirmed cases vs.
possible cases was 27.2% vs. 23.5% for the children and 0 vs. 26.5% for the staff of the affected center. The source of the infection could not be identified. Nevertheless, according to the evolution of the cases over time, the transmission route was likely to be personal contact between the staff and children, which facilitates fecal-oral dissemination. All but one of the 27 isolates analyzed (from 22 patients) showed identical features: R-profile, plasmid-profile, RAPD-type, PFGE-type; all were non-phage-typeable, with the exception of a DT104b isolate. pUO-StVR2 is probably a derivative of the virulence plasmid pSLT from the LT2 type strain that acquired an R-region complex (ACSSuT/blaOXA-catA1-strA/B-aadA1-sul1-sul2-tet[B]), in which the blaOXA-aadA1 genes are part of the variable region of a class 1 integron.
This outbreak is an example of how a Salmonella enterica serovar Typhimurium strain belonging to a type that is probably endemic in Spain can be transferred to the community and affect a susceptible population.
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ABSTRACT: The diversity of Salmonella serotype Virchow organisms causing human salmonellosis in a Spanish region over 1990-1996 was studied by genetic and phenotypic procedures. Isolates showing identical DNA fingerprintings (ribotypes, RAPD-, REP- and ERIC-types) were clustered into the same lineage. Eight lineages were defined, of which only one caused diseases throughout the studied period. Eleven phage types (PTs) were represented, the most frequent being PTs 8, 19, 31, throughout the study period, and PT4a only during 1994. Class I integrons with variable regions of 1000-, 1600-, and 2300-bp in size were respectively present in 24, 3 and 5 multiresistant isolates; 43.5% of isolates were susceptible to antimicrobials, the rest were grouped into 17 R-profiles, including from one up to eight resistances. Plasmids could be recovered from 71.5% of isolates and grouped into 25 plasmid profiles (with 1-7 plasmids each); a 3.6 kb cryptic-plasmid and a 60 kb virulence-plasmid were those most frequently found. Phage type, presence and size of integrons, and resistance profile were used to differentiate 39 clones. During the period studied 135 cases of Virchow salmonellosis were identified; 93 were apparently sporadic whereas the remainder were associated with four outbreaks. Infants under 1 year constituted the most frequent age group, with 30 gastroenteritis and two septicaemia episodes. In the four outbreaks, different clones falling into the prevalent lineage were implicated but each clone was involved in only one outbreak.European Journal of Epidemiology 02/2001; 17(1):31-40. · 5.12 Impact Factor
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ABSTRACT: Strains of multidrug-resistant Salmonella enterica serovar Typhimurium DT104 (DT104) and S. enterica serovar Agona (Agona) have been found to harbor Salmonella genomic island 1 (SGI1), a 43-kb genomic region that contains many of the drug resistance genes. Such strains are resistant to ampicillin (pse-1), chloramphenicol/florfenicol (floR), streptomycin/spectinomycin (aadA2), sulfonamides (sul1), and tetracycline [tet(G)] (commonly called the ACSSuT phenotype). All five resistance genes are found in a 13-kb multidrug resistance (MDR) region consisting of an unusual class I integron structure related to In4. We examined DT104 and Agona strains that exhibited other resistance phenotypes to determine if the resistance genes were associated with variant SGI1 MDR regions. All strains were found to harbor variant SGI1-like elements by using a combination of Southern hybridization, PCR mapping, and sequencing. Variant SGI1-like elements were found with MDR regions consisting of (i) an integron consisting of the SGI1 MDR region with the addition of a region containing a putative transposase gene (orf513) and dfrA10 located between duplicated qacEDelta1/sulI genes (SGI1-A; ACSSuTTm); (ii) an integron with either an aadA2 (SSu) or a pse-1 (ASu) cassette (SGI1-C and SGI1-B, respectively); (iii) an integron consisting of the SGI1-C MDR region plus an orf513/dfrA10 region as in SGI1-A (SGI1-D; ASSuTm; ampicillin resistance due to a TEM beta-lactamase); and (iv) an integron related to that in SGI1 but which contains a 10-kb inversion between two copies of IS6100, one which is inserted in floR (SGI1-E; ASSuT). We hypothesize that the MDR of SGI1 is subject to recombinational events that lead to the various resistance phenotypes in the Salmonella strains in which it is found.Antimicrobial Agents and Chemotherapy 07/2002; 46(6):1714-22. · 4.57 Impact Factor
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ABSTRACT: The genetic background of the antimicrobial resistance of 10 selected multiresistant Salmonella serotype Typhimurium (S. Typhimurium) strains (including the emerging monophasic variant [4,5,12:i:- ]) was investigated. All strains shared class 1 integrons (with seven types of variable regions) and belonged to different lineages (L1-L6) according to their phage types, DNA polymorphisms by XbaI-pulsed-field gel electrophoresis (PFGE), integrons, and/or resistance patterns. The strains were screened for the presence and localization (chromosomal or plasmid) of 32 DNA sequences representing integron-, Tn21-like transposon-, resistance-, and virulence-plasmid genes. Strains belonging to lineage L1 (definitive phage type DT104) carried the 90-kb Salmonella virulence plasmid together with the complete or partial chromosomally located Salmonella Genomic Island 1 (SGI1). All strains belonging to the other five lineages carried their resistance determinants on various resistance plasmids. Two of these strains showed complex plasmid profiles, which included a 95 kb virulence plasmid together with two or four resistance plasmids. Two strains carried a resistance plasmid that lacked the virulence-plasmid-encoding sequences. The remaining two strains carried two different hybrid virulence-resistance plasmids. Twenty-three of the DNA sequences could be assigned to distinct XbaI genomic restriction patterns (PFGE profiles). In this way, the influence of the resistance and virulence plasmids on the PFGE profiles was determined, and several groups of resistance genes could be identified. The data obtained represent a useful epidemiological tool for tracing the emergence and distribution of multiresistant S. Typhimurium worldwide.Microbial Drug Resistance 02/2004; 10(2):83-91. · 2.36 Impact Factor