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Two cases of serotypeable and non-serotypeable variants of Streptococcus pneumoniae detected simultaneously during invasive disease.

ABSTRACT: More than 94 serotypes of Streptococcus pneumoniae have been described to date, however the majority of disease is caused by approximately 20 serotypes. Some pneumococci do not react with commercially available antisera used for serotyping and are thus regarded as non-serotypeable (NT). These pneumococci are commonly isolated during carriage studies and very rarely cause invasive disease. Colonization may occur with more than one serotype however disease with more than one serotype is rarely detected. Thus there are limited data describing cases of pneumococcal disease caused by more than one isolate.In two cases of invasive pneumococcal disease in South Africa, a non-serotypeable and a serotypeable isolate were co-detected during routine serotyping. A serotype 1 and 18C isolate were each co-detected with a non-serotypeable isolate in 2009 (case A) and 2010 (case B), from cerebrospinal fluid and blood, respectively. Both patients were 10-14 years old. For case A, the serotypeable isolate could not be obtained due to low representation in the mixed culture. Using electron microscopy we confirmed lack of capsule for the non-serotypeable isolates. Comparison of the case A non-serotypeable isolate with a serotype 1 genome revealed only the presence of the rhamnose biosynthesis genes (rmlA, B, C and D) in the capsular locus, all other capsular genes were absent. Nonetheless it had a multilocus sequence type (ST) associated with serotype 1 (ST217 and ribosomal ST3462) and its core genome clustered with other ST217 isolates. The case B non-serotypeable isolate had all serotype 18C capsular genes except for variation in the wchA and wze genes, compared to the 18C isolate. Both case B isolates were ST9817 and their core genomes were identical.The ability of pneumococci to alter capsule production is a potential vaccine escape mechanism and therefore non-serotypeable pneumococci should be monitored as such organisms may increase under vaccine pressure.

SUBMITTER: Ndlangisa KM

PROVIDER: S-EPMC4921036 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Two cases of serotypeable and non-serotypeable variants of Streptococcus pneumoniae detected simultaneously during invasive disease.

Ndlangisa Kedibone M KM du Plessis Mignon M Allam Mushal M Wolter Nicole N Mohale Thabo T de Gouveia Linda L Birkhead Monica M Klugman Keith P KP von Gottberg Anne A

BMC microbiology 20160624 1

<h4>Background</h4>More than 94 serotypes of Streptococcus pneumoniae have been described to date, however the majority of disease is caused by approximately 20 serotypes. Some pneumococci do not react with commercially available antisera used for serotyping and are thus regarded as non-serotypeable (NT). These pneumococci are commonly isolated during carriage studies and very rarely cause invasive disease. Colonization may occur with more than one serotype however disease with more than one ser ...[more]

PMID: 27342074

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Project description:BackgroundGlobally, over 800 000 children under five die each year from infectious diseases caused by Streptococcus pneumoniae. To understand genetic relatedness between isolates, study transmission routes, assess the impact of human interventions e.g. vaccines, and determine infection sources, genotyping methods are required. The 'gold standard' genotyping method, Multi-Locus Sequence Typing (MLST), is useful for long-term and global studies. Another genotyping method, Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA), has emerged as a more discriminatory, inexpensive and faster technique; however there is no universally accepted method and it is currently suitable for short-term and localised epidemiology studies. Currently Australia has no national MLST database, nor has it adopted any MLVA method for short-term or localised studies. This study aims to improve S. pneumoniae genotyping methods by modifying the existing MLVA techniques to be more discriminatory, faster, cheaper and technically less demanding than previously published MLVA methods and MLST.MethodsFour different MLVA protocols, including a modified method, were applied to 317 isolates of serotyped invasive S. pneumoniae isolated from sterile body sites of Queensland children under 15 years from 2007-2012. MLST was applied to 202 isolates for comparison.ResultsThe modified MLVA4 is significantly more discriminatory than the 'gold standard' MLST method. MLVA4 has similar discrimination compared to other MLVA techniques in this study). The failure to amplify particular loci in previous MLVA methods were minimised in MLVA4. Failure to amplify BOX-13 and Spneu19 were found to be serotype specific.ConclusionWe have modified a highly discriminatory MLVA technique for genotyping Queensland invasive S. pneumoniae. MLVA4 has the ability to enhance our understanding of the pneumococcal epidemiology and the changing genetics of the pneumococcus in localised and short-term studies.

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Two cases of serotypeable and non-serotypeable variants of Streptococcus pneumoniae detected simultaneously during invasive disease.

Publications

Two cases of serotypeable and non-serotypeable variants of Streptococcus pneumoniae detected simultaneously during invasive disease.

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