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Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in northern Thailand.

ABSTRACT: Infection with group A streptococci (GAS) can lead to the development of severe postinfectious sequelae such as rheumatic fever (RF). In Thailand, RF and rheumatic heart disease (RHD) remain important health problems. More than 80% of GAS circulating in this population are non-M antigen typeable by conventional M serotyping methods. In this study, we determine the M protein sequence types of GAS isolates found in northern Thailand. The emm genes from 53 GAS isolates, collected between 1985 and 1995 from individuals with pharyngitis, impetigo, acute RF (ARF), RHD, or meningitis as well as from individuals without infections, were amplified by PCR and sequenced. Thirteen new sequence types that did not show homology to previously published sequences were characterized. Six of these sequence types could be isolated from both skin and throat sites of impetigo and pharyngitis/ARF patients, respectively. In many cases we could not specifically differentiate skin strains or throat strains that could be associated with ARF or acute glomerulonephritis. Antigenic variations in the emm gene of the isolates investigated, compared to published M protein sequences, were predominantly due to point mutations, small deletions, and insertions in the hypervariable region. One group of isolates with homology to M44 exhibited corrected frameshift mutations. A new M type isolated from an RHD patient exhibited nucleotide sequence corresponding to the N terminus of M58 and the C terminus of M25, suggesting that recombination between the two types may have occurred. This study provided epidemiological data relating to GAS endemic to northern Thailand which could be useful for identification of vaccine candidates in a specific region of endemicity.

SUBMITTER: Pruksakorn S

PROVIDER: S-EPMC86390 | biostudies-literature | 2000 Mar

REPOSITORIES: biostudies-literature

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Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in northern Thailand.

Pruksakorn S S Sittisombut N N Phornphutkul C C Pruksachatkunakorn C C Good M F MF Brandt E E

Journal of clinical microbiology 20000301 3

Infection with group A streptococci (GAS) can lead to the development of severe postinfectious sequelae such as rheumatic fever (RF). In Thailand, RF and rheumatic heart disease (RHD) remain important health problems. More than 80% of GAS circulating in this population are non-M antigen typeable by conventional M serotyping methods. In this study, we determine the M protein sequence types of GAS isolates found in northern Thailand. The emm genes from 53 GAS isolates, collected between 1985 and 1 ...[more]

PMID: 10699034

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Project description:Background. Pneumococcus is a major human pathogen and the polysaccharide capsule is considered its main virulence factor. Nevertheless, strains lacking a capsule, named non-typeable pneumococcus (NT), are maintained in nature and frequently colonise the human nasopharynx. Interest in these strains, not targeted by any of the currently available pneumococcal vaccines, has been rising as they seem to play an important role in the evolution of the species. Currently, there is a paucity of data regarding this group of pneumococci. Also, questions have been raised on whether they are true pneumococci. We aimed to obtain insights in the genetic content of NT and the mechanisms leading to non-typeability and to genetic diversity. Methods. A collection of 52 NT isolates representative of the lineages circulating in Portugal between 1997 and 2007, as determined by pulsed-field gel electrophoresis and multilocus sequence typing, was analysed. The capsular region was sequenced and comparative genomic hybridisation (CGH) using a microarray covering the genome of 10 pneumococcal strains was carried out. The presence of mobile elements was investigated as source of intraclonal variation. Results. NT circulating in Portugal were found to have similar capsular regions, of cps type NCC2, i.e., having aliB-like ORF1 and aliB-like ORF2 genes. The core genome of NT was essentially similar to that of encapsulated strains. Also, competence genes and most virulence genes were present. The few virulence genes absent in all NT were the capsular genes, type-I and type-II pili, choline-binding protein A (cbpA/pspC), and pneumococcal surface protein A (pspA). Intraclonal variation could not be entirely explained by the presence of prophages and other mobile elements. Conclusions. NT circulating in Portugal are a homogeneous group belonging to cps type NCC2. Our observations support the theory that they are bona-fide pneumococcal isolates that do not express the capsule but are otherwise essentially similar to encapsulated pneumococci. Thus we propose that NT should be routinely identified and reported in surveillance studies.

Dataset Information

Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in northern Thailand.

Publications

Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in northern Thailand.

Similar Datasets

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