ABSTRACT
Pyogenic streptococci cause significant morbidity and mortality, and the incidence of invasive group C and G streptococcal disease appears to be increasing. In this retrospective study we describe the epidemiological characteristics of invasive group A, C and G, along with non-invasive group C and G streptococcal infections in Western Norway from 1999 to 2013. A total of 512 invasive streptococcal infections were identified, of these 297 (58%) were group A (GAS), 24 (5%) group C (GCS) and 188 (37%) group G streptococci (GGS). In the non-invasive group, 4935 GCS and GGS-infections were identified. GCS and GGS were treated as one group (GCGS) for statistical purposes. All microbial categories displayed increasing incidence with age, seasonal variation and a male predominance. The incidence of invasive GCGS infections increased significantly from 1.4/100,000 inhabitants in 1999 to 6.3/100,000 in 2013 (p <0.001). Conversely, the annual rates of invasive GAS infection exhibited marked fluctuations, ranging from 2.7/100,000 (2000) to 8.3/100,000 (1999), but no significant temporal trends were observed. The incidence of non-invasive GCGS infections decreased significantly during the study period (p <0.001). The most frequently encountered emm-types among the 209 iGAS-isolates analysed were emm1 (24%), emm3 (14%) and emm28 (14%); whereas stG643 (19%), stG485 (15%) and stG6 (13%) were most prevalent among the 122 iGCGS-isolates available for typing. The increasing burden of invasive ß-haemolytic streptococcal disease in our community calls for sustained attentiveness to the clinical and molecular aspects of GAS, GCS and GGS infections.
Subject(s)
Streptococcal Infections/epidemiology , Streptococcal Infections/microbiology , Streptococcus/classification , Streptococcus/isolation & purification , Adolescent , Adult , Age Factors , Aged , Aged, 80 and over , Antigens, Bacterial/genetics , Bacterial Outer Membrane Proteins/genetics , Carrier Proteins/genetics , Child , Child, Preschool , Female , Genotype , Humans , Incidence , Infant , Infant, Newborn , Male , Middle Aged , Molecular Epidemiology , Norway/epidemiology , Retrospective Studies , Risk Factors , Seasons , Sex Factors , Streptococcus/genetics , Surveys and Questionnaires , Young AdultABSTRACT
Streptococcal inhibitor of complement (SIC) and distantly related to SIC (DRS) are well-characterized extracellular virulence factors produced by only a few emm types among group A streptococci. The prevalence and sequence variations of the sic-like gene (sicG) in clinical samples of group C and G Streptococcus dysgalactiae subspecies equisimilis (SDSE), however, have not been widely investigated. We constructed primers targeting sicG and screened 129 geographically matched and previously emm-typed non-invasive (n = 64) and invasive (n = 65) SDSE isolates for the presence of this gene. sicG was detected in seven non-invasive and eight invasive isolates belonging to eight different emm types. Within five of these emm types, sicG-negative isolates were also detected. All three isolates of stG2078.0 possessed sicG and were associated with severe soft tissue infections. Altogether, six sicG alleles (sicG1-6) were identified, and sequence variations were mainly caused by single nucleotide polymorphisms and deletion/insertion mutations. sicG1-6 were predicted to encode SICG proteins of varying length, composition, and homology with SIC and DRS proteins of group A streptococci. Our findings indicate an unpredictable association between sicG and emm type, a limited distribution and substantial sequence diversity of sicG, and no obvious relation between its presence and disease severity.
