Dataset Information

Clonal relationships between invasive and noninvasive Lancefield group C and G streptococci and emm-specific differences in invasiveness.

ABSTRACT: Lancefield group G and group C streptococci (GGS and GCS, respectively) are pathogens responsible for a number of life-threatening infections. A collection of 116 recent (1998 to 2004) invasive (n = 28) and noninvasive (n = 88) GGS and GCS clinical isolates from Portugal were characterized. All isolates were identified as Streptococcus dysgalactiae subsp. equisimilis and characterized by emm typing and DNA macrorestriction profiling using pulsed-field gel electrophoresis (PFGE). emm typing revealed the presence of 22 distinct types, including 3 novel types. PFGE identified 14 clones with more than two isolates, but over half of the isolates were concentrated in 3 large clones. Individual clones and emm types showed a low level of association, since the majority of the clones included more than one emm type and the same emm type was found among diverse genetic backgrounds. Two emm types, stg2078 and stg10, were significantly more frequent among invasive isolates, and another two, stg6792 and stg166b, were present only in noninvasive isolates, suggesting a correlation between emm type and invasive disease potential.

SUBMITTER: Pinho MD

PROVIDER: S-EPMC1393098 | biostudies-literature | 2006 Mar

REPOSITORIES: biostudies-literature

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Clonal relationships between invasive and noninvasive Lancefield group C and G streptococci and emm-specific differences in invasiveness.

Pinho M D MD Melo-Cristino J J Ramirez M M

Journal of clinical microbiology 20060301 3

Lancefield group G and group C streptococci (GGS and GCS, respectively) are pathogens responsible for a number of life-threatening infections. A collection of 116 recent (1998 to 2004) invasive (n = 28) and noninvasive (n = 88) GGS and GCS clinical isolates from Portugal were characterized. All isolates were identified as Streptococcus dysgalactiae subsp. equisimilis and characterized by emm typing and DNA macrorestriction profiling using pulsed-field gel electrophoresis (PFGE). emm typing revea ...[more]

PMID: 16517864

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Project description:BackgroundA few lineages of Group A streptococci (GAS) have been associated with a reemergence of severe invasive streptococcal disease in developed countries. However, the majority of the comparisons between invasive and non-invasive GAS isolates have been performed for collections of reduced genetic diversity or relied on limited typing information to distinguish clones. We characterized by several typing methods and compared a collection of 160 isolates recovered from normally sterile sites with 320 isolates associated with pharyngitis and recovered in the same time period in Portugal.ResultsAlthough most of the isolates belonged to clones that were equally prevalent in invasive infections and pharyngitis, we identified markers of invasiveness, namely the emm types 1 and 64, and the presence of the speA and speJ genes. In contrast, emm4, emm75, and the ssa and speL/M genes were significantly associated with pharyngitis. There was a strong agreement between the emm type, the superantigen (SAg) genes and the clusters defined by pulsed-field gel electrophoresis (PFGE) profiling. Therefore, combinations of particular emm types and SAg genes frequently co-occurred in the same PFGE cluster, but there was no synergistic or antagonistic interaction between them in determining invasiveness. Only macrolide-susceptible PFGE clones were significantly associated with invasive infections or pharyngitis, while the clones of resistant isolates sharing all other molecular properties analyzed were equally prevalent in the two groups of isolates.ConclusionsThis study confirmed the importance of the widely disseminated emm1-T1-ST28 clone in invasive infections but also identified other clones linked to either invasive infections (emm64-ST164) or pharyngitis (emm4-T4-ST39), which may be more limited in their temporal and geographical spread. Clonal properties like some emm types or SAg genes were associated with disease presentation, highlighting the importance of bacterial genetic factors to the outcome of GAS infections, although other, yet unidentified factors may also play an important role.

Project description:Genetic intractability presents a fundamental barrier to the manipulation of bacteria, hindering advancements in microbiological research. Group A Streptococcus (GAS), a lethal human pathogen currently associated with an unprecedented surge of infections worldwide, exhibits poor genetic tractability attributed to the activity of a conserved type 1 restriction modification system (RMS). RMS detect and cleave specific target sequences in foreign DNA that are protected in host DNA by sequence-specific methylation. Overcoming this "restriction barrier" thus presents a major technical challenge. Here, we demonstrate for the first time that different RMS variants expressed by GAS give rise to genotype-specific and methylome-dependent variation in transformation efficiency. Furthermore, we show that the magnitude of impact of methylation on transformation efficiency elicited by RMS variant TRDAG, encoded by all sequenced strains of the dominant and upsurge-associated emm1 genotype, is 100-fold greater than for all other TRD tested and is responsible for the poor transformation efficiency associated with this lineage. In dissecting the underlying mechanism, we developed an improved GAS transformation protocol, whereby the restriction barrier is overcome by the addition of the phage anti-restriction protein Ocr. This protocol is highly effective for TRDAG strains including clinical isolates representing all emm1 lineages and will expedite critical research interrogating the genetics of emm1 GAS, negating the need to work in an RMS-negative background. These findings provide a striking example of the impact of RMS target sequence variation on bacterial transformation and the importance of defining lineage-specific mechanisms of genetic recalcitrance. IMPORTANCE Understanding the mechanisms by which bacterial pathogens are able to cause disease is essential to enable the targeted development of novel therapeutics. A key experimental approach to facilitate this research is the generation of bacterial mutants, through either specific gene deletions or sequence manipulation. This process relies on the ability to transform bacteria with exogenous DNA designed to generate the desired sequence changes. Bacteria have naturally developed protective mechanisms to detect and destroy invading DNA, and these systems severely impede the genetic manipulation of many important pathogens, including the lethal human pathogen group A Streptococcus (GAS). Many GAS lineages exist, of which emm1 is dominant among clinical isolates. Based on new experimental evidence, we identify the mechanism by which transformation is impaired in the emm1 lineage and establish an improved and highly efficient transformation protocol to expedite the generation of mutants.

Project description:ObjectiveTo assess the association between features of acute sore throat and the growth of streptococci from culturing a throat swab.DesignDiagnostic cohort.SettingUK general practices.ParticipantsPatients aged 5 or over presenting with an acute sore throat. Patients were recruited for a second cohort (cohort 2, n=517) consecutively after the first (cohort 1, n=606) from similar practices.Main outcomePredictors of the presence of Lancefield A/C/G streptococci.ResultsThe clinical score developed from cohort 1 had poor discrimination in cohort 2 (bootstrapped estimate of area under the receiver operator characteristic (ROC) curve (0.65), due to the poor validity of the individual items in the second data set. Variables significant in multivariate analysis in both cohorts were rapid attendance (prior duration 3 days or less; multivariate adjusted OR 1.92 cohort, 1.67 cohort 2); fever in the last 24 h (1.69, 2.40); and doctor assessment of severity (severely inflamed pharynx/tonsils (2.28, 2.29)). The absence of coryza or cough and purulent tonsils were significant in univariate analysis in both cohorts and in multivariate analysis in one cohort. A five-item score based on Fever, Purulence, Attend rapidly (3 days or less), severely Inflamed tonsils and No cough or coryza (FeverPAIN) had moderate predictive value (bootstrapped area under the ROC curve 0.73 cohort 1, 0.71 cohort 2) and identified a substantial number of participants at low risk of streptococcal infection (38% in cohort 1, 36% in cohort 2 scored ≤1, associated with a streptococcal percentage of 13% and 18%, respectively). A Centor score of ≤1 identified 23% and 26% of participants with streptococcal percentages of 10% and 28%, respectively.ConclusionsItems widely used to help identify streptococcal sore throat may not be the most consistent. A modified clinical scoring system (FeverPAIN) which requires further validation may be clinically helpful in identifying individuals who are unlikely to have major pathogenic streptococci.

Dataset Information

Clonal relationships between invasive and noninvasive Lancefield group C and G streptococci and emm-specific differences in invasiveness.

Publications

Clonal relationships between invasive and noninvasive Lancefield group C and G streptococci and emm-specific differences in invasiveness.

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