IS200 Typing Research Articles

Nontyphoid Salmonella gastroenteritis in pediatric patients from urban areas in the city of Mérida, Venezuela

Nontyphoid Salmonella (NTS) infections are a frequent cause of self-limited diarrhoeal illness in healthy children that do not usually require antibiotic treatment. This study was conducted by analyzing the phenotypic and genotypic traits of NTS strains from pediatric patients with acute gastroenteritis living in urban areas in the city of Mérida, Venezuela. Thirty-seven Salmonella strains (18 S. Enteritidis; 14 S. Typhimurium; 2 S. Java; 2 S. Saintpaul; 1 S. Infantis) were isolated from 243 stool specimens. These strains were biochemically identified and serotyped. Antimicrobial susceptibility was determined by the disc-diffusion assay. Genetic characterization included plasmid profiling, PCR detection of the spv region and inv genes, and IS200 typing. Thirty (81.0%) of the Salmonella isolates were resistant to the antimicrobial tested. Of these strains, 17 (56.7%) were resistant to at least one antibiotic. Five resistance patterns were observed, of which the most frequently found was the single type (tetracycline, streptomycin or ampicillin). All the S. Typhimurium harbored plasmids, but only three large plasmids (60, 72 and 84 kb) yielded amplicons with a spvR specific primers. All the Salmonella serotypes showed the presence of an inv region. Eight distinct IS200 profiles could be detected among the 37 Salmonella strains studied. Predominant Enteritidis and Typhimurium serotypes, as well as serotypes Java, Saintpaul and Infantis, are circulating in the city of Mérida, Venezuela. Most of these strains are susceptible to first-line antibiotics but active monitoring of isolates for antimicrobial resistance is necessary. IS200 typing, applied in association with conventional methods, allowed the characterization of all isolates and suggested the presence of different infection sources.

Clonal diversity of Salmonella enterica serotype Typhi isolated from patients with typhoid fever in Tehran

In this study, antimicrobial susceptibility test and genetic typing were used to characterize 15 Salmonella enterica serotype Typhi (S. Typhi) isolates recovered from sporadic cases of typhoid fever in Tehran, Iran during 2004. Antimicrobial susceptibility test showed that all isolates were susceptible to 20 antimicrobials examined in this study. Analysis of insertion elements showed that 2 IS200 types with 10 and 11 copies were present. 11 of the 15 isolates were found to possess 10 IS200 elements residing on fragments from 23 to 2.3 kb. Comparison of the RiboPrinter (automated ribotyping) patterns of S. Typhi showed that 60% (9/15) of the isolates belonged to a single ribotype. PCR based random amplified polymorphic DNA analysis (RAPD) and enterobacterial repetitive intergenic consensus (ERIC) and pulsed-field gel electrophresis (PFGE) were also performed. ERIC and RAPD-PCR method showed 2 and 3 genotyping patterns amongst the isolates, respectively. The PFGE typing was carried out by using XbaI restriction enzyme, and 7 restriction patterns were observed. Overall, the molecular typing methods applied in this study showed that the isolated S. Typhi populations were highly polyclonal as shown by PFGE.

Molecular Typing Reveals a Unique Clone of Salmonella enterica Serotype Typhi among Indian Strains

Molecular Typing Reveals a Unique Clone of <i>Salmonella enterica</i> Serotype Typhi among Indian Strains

Molecular characterization of Salmonella enterica subsp. enterica serovar Typhimurium DT009 isolates: differentiation of the live vaccine strain Zoosaloral from field isolates.

A total of 25 epidemiologically unrelated Salmonella enterica subsp. enterica (S.) serovar Typhimurium DT009 isolates from various human and animal sources, the original S. Typhimurium DT009 Zoosaloral live vaccine strain and two Zoosaloral strains reisolated from vaccinated chickens were investigated by various molecular typing methods (I) to determine the most suitable method or combination of methods for the differentiation of DT009 field isolates and (II) to investigate which molecular methods are suitable to differentiate the Zoosaloral live vaccine strain from field isolates of the same phage type. Based on the results of plasmid profile analysis, IS200 typing and macrorestriction analysis with XbaI, SpeI and BlnI, the 28 S. Typhimurium DT009 isolates were assigned to 16 different genomic groups, one of which was exclusively represented by the original and the reisolated Zoosaloral strains. IS200 typing was the most discriminatory single method for the differentiation of the DT009 isolates followed by plasmid profile analysis and BlnI-macrorestriction analysis. The Zoosaloral vaccine strain differed from the DT009 field isolates by its unique HindIII-fragment pattern of the virulence plasmid and by its unique SpeI-macrorestriction pattern.

IS200 fingerprint of Salmonella enterica serotype Typhimurium human strains isolated in Sardinia.

A collection of Salmonella enterica serotype Typhimurium human strains isolated in Northern Sardinia (Italy) was examined for the insertion sequence IS200, phage type, antibiotic profile, ribotyping polymorphisms and plasmid profile. All clinical isolates studied contained from 4 to 10 copies of the IS200 element. IS200 permitted to discriminate Typhimurium strains and to identify five IS200 types, some of them circulating in Sardinia at least since 1900. Strains belonging to phage DT104 predominated and correlated with a specific IS200 pattern.

Antibiotic-resistant Salmonella typhi from two outbreaks: few ribotypes and IS200 types harbor Inc HI1 plasmids.

To investigate factors that could be involved in the emergence of antibiotic resistant S. typhi, we characterized R plasmids and antibiotic resistant S. typhi strains from two outbreaks of typhoid in Peru and Chile. Differences in the Inc HI1 plasmids of Peruvian and Chilean strains were identified by conjugation and incompatibility studies and plasmid DNA characterization. Antibiotic-resistant S. typhi harboring Inc HI1 plasmids belonged to a reduced number of Pst1 and Cla1 ribotypes and IS200 types, in contrast to the high genetic diversity found among epidemic antibiotic-susceptible S. typhi. The low diversity of antibiotic-resistant S. typhi suggests that they may express properties that are related to both their ability to harbor Inc HI1 R plasmids and to disseminate.

Molecular typing of Salmonella enterica serovar typhi.

The efficiencies of different tests for epidemiological markers--phage typing, ribotyping, IS200 typing, and pulsed-field gel electrophoresis (PFGE)--were evaluated for strains from sporadic cases of typhoid fever and a well-defined outbreak. Ribotyping and PFGE proved to be the most discriminating. Both detected two different patterns among outbreak-associated strains.

Epidemic typhoid in Chile: analysis by molecular and conventional methods of Salmonella typhi strain diversity in epidemic (1977 and 1981) and nonepidemic (1990) years.

From 1977 to 1986, Chile experienced an important typhoid fever epidemic, despite statistics that indicated apparently improving levels of sanitation of drinking water and sewage disposal. The lack of antibiotic resistance among the Salmonella typhi strains isolated during this period, the mild clinical presentation of the disease, and the initially low level of efficacy of the S. typhi Ty21a vaccine in the population exposed to the epidemic suggested that this epidemic might have resulted from the dissemination of S. typhi strains with unique characteristics. To investigate this hypothesis, we used conventional methods (bacteriophage typing and biotyping) and molecular methods (restriction fragment length polymorphism analysis, ribotyping, IS200 typing, and PCR amplification of the fliC-d gene) to study a population of 149 S. typhi isolates during 1977, 1981, and 1990, the years that included periods with low (when the disease was endemic) and high (when the disease was epidemic) morbidities. Our results indicate that these S. typhi isolates in Chile represent a number of highly diverse variants of the clone of S. typhi with a worldwide distribution described by Selander et al. (R. K. Selander, P. Beltran, N.H. Smith, R. Helmuth, F.A. Rubin, D.J. Kopecko, K. Ferris, B.D. Tall, A. Cravioto, and J.M. Musser, Infect. Immun. 58:2262-2275, 1990). For example, we detected 26 PstI and 10 ClaI ribotypes among 47 and 16 S. typhi strains belonging to this clone, respectively. These results suggest that the Chilean epidemic was probably produced by multiple sources of infection because of deficient sanitary conditions. These findings illustrate the usefulness of molecular methods for characterizing the potential causes of the typhoid epidemics and the possible routes of transmission of S. typhi strains in typhoid epidemics.

Use of ribotyping, IS200 typing and plasmid analysis for the identification of Salmonella enterica subsp.enterica serovar typhimurium vaccine strain Zoosaloral H and its differentiation from wild type strains of the same serovar

Fifty Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) isolates obtained from one vaccinated and three non-vaccinated poultry flocks as well as the commercially available vaccine strain Zoosaloral H and a S. Typhimurium reference strain were characterized genotypically to differentiate between S. Typhimurium live vaccine strain Zoosaloral H and wild type strains of the same serovar. Ribotyping revealed five different patterns one of which exclusively occurred in the vaccine strain. Seven different hybridization patterns could be observed by IS200-typing of the S. Typhimurium isolates; one of them was only detectable in the vaccine strain. Plasmid analysis showed that 51% of the S. Typhimurium isolates including the vaccine strain harboured large plasmids of approximately 60 MDa. Hybridization with a virulence gene probe identified only 48% of these large plasmids, including that of the vaccine strain, to carry this virulence-associated gene. However, restriction endonuclease analysis of the hybridizing plasmids showed that the virulence gene was located on HindIII fragments of different sizes in the plasmid of the S. Typhimurium vaccine strain Zoosaloral H and in the plasmids of the respective wild type S. Typhimurium isolates. Thus, ribotyping, IS200-typing and plasmid analysis represent at least three independent systems which allow the genotypic identification of the S. Typhimurium vaccine strain Zoosaloral H and its differentiation from wild type isolates of the same serovar.

Demonstration of persistence of Salmonella typhimurium in an AIDS patient by molecular methods

We document microbiological persistence of the same Salmonella typhimurium strain in an AIDS patient during 7 months of clinical observation despite prolonged quinolone therapy. Persistence was demonstrated by phage types that closely resembled one another, similar antibiotic resistance patterns, conserved restriction fragment length polymorphism of chromosomal DNA digested with different DNA restriction enzymes, identical ribotypes, and IS200 types in four characterized sequential isolates of S. typhimurium.

Insertion sequence IS200 can differentiate drug-resistant and drug-sensitive Salmonella typhi of Vi-phage types E1 and M1

The type strains of Vi-phage types E1, M1 and A of Salmonella typhi, together with drug-resistant and drug-sensitive strains of phage types E1 and M1 isolated in 1992 from patients associated with India or Pakistan, and a drug-resistant strain of phage type A isolated in South Africa in 1991, were characterised with respect to the presence of plasmids conferring resistance to antimicrobial drugs and their chromosomal insertion sequence IS200 profiles. The three type strains, the drug-sensitive strains of Vi-phage types E1 and M1, and a strain of phage type M1 resistant to ampicillin and trimethoprim but not to chloramphenicol, did not contain plasmids. In contrast, for strains of phage types E1 and M1 resistant to chloramphenicol, ampicillin and trimethoprim, and for the drug-resistant strain of phage type A, the complete spectrum of resistance was encoded by high molecular mass plasmids belonging to the H1 incompatibility group. Characterisation of IS200 profiles demonstrated that at least 13 IS200 copies were distributed on the chromosome of all strains tested. Although the IS200 profiles of the type strains of Vi-phage types A, E1 and M1 were identical, it was possible to distinguish between drug-sensitive and drug-resistant strains of Vi-phage types E1 and M1 isolated from patients infected in India and Pakistan by this method. It was concluded that although IS200 typing is not as discriminatory as phage typing for the primary subdivision of S. typhi, it may be useful for certain epidemiological investigations and, in particular, for investigating the origins of strains with multiple drug resistance.