Food-borne outbreak of group G streptococcal sore throat in an Israeli military base

Streptococcus dysgalactiae subsp. equisimilis infection and its intersection with Streptococcus pyogenes

SUMMARYStreptococcus dysgalactiae subsp. equisimilis (SDSE) is an increasingly recognized cause of disease in humans. Disease manifestations range from non-invasive superficial skin and soft tissue infections to life-threatening streptococcal toxic shock syndrome and necrotizing fasciitis. Invasive disease is usually associated with co-morbidities, immunosuppression, and advancing age. The crude incidence of invasive disease approaches that of the closely related pathogen, Streptococcus pyogenes. Genomic epidemiology using whole-genome sequencing has revealed important insights into global SDSE population dynamics including emerging lineages and spread of anti-microbial resistance. It has also complemented observations of overlapping pathobiology between SDSE and S. pyogenes, including shared virulence factors and mobile gene content, potentially underlying shared pathogen phenotypes. This review provides an overview of the clinical and genomic epidemiology, disease manifestations, treatment, and virulence determinants of human infections with SDSE with a particular focus on its overlap with S. pyogenes. In doing so, we highlight the importance of understanding the overlap of SDSE and S. pyogenes to inform surveillance and disease control strategies.

Prevalence and molecular diversity of invasive Streptococcus dysgalactiae and Streptococcus pyogenes in a German tertiary care medical centre

Prevalence of invasive ß-haemolytic streptococci (BHS) at a tertiary care hospital and molecular diversity of S. pyogenes and S. dysgalactiae was studied. Between 2012 and 2016, all blood culture sets (n = 55,839), CSF (n = 8413) and soft tissue (n = 20,926) samples were analysed for BHS positivity using HYBASE software. Molecular profiles of 99 S. pyogenes and S. dysgalactiae were identified by sequencing of M protein genes (emm types) and multiplex PCR typing of 20 other virulence determinants. Streptococci contributed to 6.2% of blood, 10.7% of CSF and 14.5% of soft tissue isolates, being among the most common invasive isolates. The overall rates of invasive S. pyogenes, S. agalactiae, S. dysgalactiae and S. pneumoniae were 2.4, 4.4, 2.1, and 5.3%. Whereas S. pneumoniae was 1.5% more common in CSF samples, BHS isolates were 2-fold and 11-fold higher in bacteraemia and invasive soft tissue infections. Genetic BHS typing revealed wide molecular diversity of invasive and noninvasive group A and group G BHS, whereas one emm-type (stG62647.0) and no other virulence determinants except scpA were detected in invasive group C BHS. BHS were important invasive pathogens, outpacing S. pneumoniae in bacteraemia and invasive soft tissue infections. The incidence of S. dysgalactiae infections was comparable to that of S. pyogenes even with less diversity of molecular virulence. The results of this study emphasise the need for awareness of BHS invasiveness in humans and the need to develop BHS prevention strategies.

Foodborne Outbreak of Group G Streptococcal Pharyngitis in a School Dormitory in Osaka, Japan

In September 2016, 140 patients with primary symptoms of sore throat and fever were identified in a school dormitory in Osaka, Japan. Epidemiological and laboratory investigations determined that these symptomatic conditions were from a foodborne outbreak of group G streptococcus (GGS), with GGS being isolated from samples from patients, cooks, and foods. The strain of GGS was identified as Streptococcus dysgalactiae subsp. equisimilis of two emm types (stG652.0 and stC36.0). The causative food, a broccoli salad, was contaminated with the two types of S. dysgalactiae subsp. equisimilis, totaling 1.3 × 10⁴ CFU/g. Pulsed-field gel electrophoresis (PFGE) of samples from patients, cooks, and foods produced similar band patterns among samples with the same emm type. This result suggested the possibility of exposure from the contaminated food. The average onset time was 44.9 h and the prevalence rate was 62%. This is the first report to identify the causative food of a foodborne outbreak by Streptococcus dysgalactiae subsp. equisimilis.

A Study to Determine if Addition of Palatal Petechiae to Centor Criteria Adds More Significance to Clinical Diagnosis of Acute Strep Pharyngitis in Children

Objective. A study to determine if addition of palatal petechiae to Centor criteria adds more value for clinical diagnosis of acute strep pharyngitis in children. Hypothesis. In children, Centor Criteria does not cover all the symptoms and signs of acute strep pharyngitis. We hypothesize that addition of palatal petechiae to Centor Criteria will increase the possibility of clinical diagnosis of group A streptococcal pharyngitis in children. Methods. One hundred patients with a complaint of sore throat were enrolled in the study. All the patients were examined clinically using the Centor Criteria. They were also examined for other signs and symptoms like petechial lesions over the palate, abdominal pain, and skin rash. All the patients were given rapid strep tests, and throat cultures were sent. No antibiotics were given until culture results were obtained. Results. The sample size was 100 patients. All 100 had fever, sore throat, and erythema of tonsils. Twenty of the 100 patients had tonsillar exudates, 85/100 had tender anterior cervical lymph nodes, and 86/100 had no cough. In total, 9 out of the 100 patients had positive throat cultures. We observed that petechiae over the palate, a very significant sign, is not included in the Centor Criteria. Palatal petechiae were present in 8 out of the 100 patients. Six out of these 8 with palatal petechiae had positive throat culture for strep (75%). Only 7 out of 20 with exudates had positive strep culture. Sixteen out of the 100 patients had rapid strep test positive. Those 84/100 who had negative rapid strep also had negative throat culture. Statistics. We used Fisher’s exact test, comparing throat culture positive and negative versus presence of exudates and palatal hemorrhages with positive and negative throat cultures and the resultant P value <.0001. Conclusion. Our study concludes that addition of petechiae over the palate to Centor Criteria will increase the possibility of diagnosing acute group A streptococcal pharyngitis in children.

Molecular characterization and antibiotic resistance of group G streptococci in Israel: comparison of invasive, non-invasive and carriage isolates

Beta-hemolytic group G streptococci (GGS) are increasingly recognized as a source of substantial morbidity, causing mild to severe sporadic infections as well as outbreaks. The purpose of this study was to determine the genetic diversity and antibiotic resistance of GGS in Israel in order to aid in prevention and control. A total of 325 GGS isolates were collected in Israel between 2007 and 2011 from three determined settings: (1) carriage (n = 60), an observational longitudinal carriage study in the IF, (2) non-invasive (n = 166), clinical sporadic and epidemic non-invasive cases in the IDF, and (3) invasive (n = 99) cases of bacteremia collected during this period in Israel from a similar age group, at the national Streptococcal Reference Center. All isolates were characterized genetically and by their antibiotic-resistance profile. emm typing revealed 35 distinct types and subtypes among 228 S. dysgalactiae subsp. equisimilis (SDSE) isolates, with high genetic diversity. An additional 97 GGS were identified as Streptococcus anginosus (SAG). The proportion of SDSE was higher in the invasive (100 %) and non-invasive (63.8 %) isolates compared to the carriage ones (38.3 %). Clindamycin, erythromycin, azithromycin and tetracycline resistance was detected in 6.6 %, 8.6 %, 9.7 % and 37.6 % of isolates, respectively. Overall, the most resistant isolates were in the invasive group and the fewest were in the SAG group. Considerable genetic diversity and common antibiotic resistance were revealed among GGS strains which differed according to the epidemiologic settings. Further clinical, epidemiological and basic research of GGS as a pathogen is warranted.

Genome sequence and virulence factors of a group G Streptococcus dysgalactiae subsp. equisimilis strain with a new element carrying erm(B)

A Streptococcus dysgalactiae subsp. equisimilis (SDSE) strain WCHSDSE-1, which caused an outbreak of tonsillopharyngitis among healthcare workers in China, was subjected to genome sequencing and analysis. WCHSDSE-1 belongs to the Lancefield group G, emm type stG211.1 and sequence type 44. WCHSDSE-1 has virulence factors for adherence, impairing the recruitment of neutrophils to infection sites and toxins including streptolysins O and S and exotoxin G. WCHSDSE-1 has a 45.4-kb element resembling a conjugative transposon. This element is absent from other known SDSE genomes and contains the macrolide-resistant gene erm(B). Conjugative transfer of erm(B) was not successful in mating experiments, suggesting that the element might have lost its ability of conjugation. An almost identical element, which contains the tetracycline-resistant gene tet(M) instead of erm(B), is present on the genome of Filifactor alocis ATCC 35896. The boundaries and insertion sites of the two elements were identified and both were flanked by a 3-bp direct repeat, which is characteristic of transposition. In conclusion, the spectrum of virulence factors of WCHSDSE-1 is similar to other SDSE strains causing invasive diseases. WCHSDSE-1 possesses a new transposable element encoding macrolide resistance, which could pick up different resistance genes and could be transferred across species in oral microflora.

Inverse association between Lancefield group G Streptococcus colonization and sore throat in slum and nonslum settings in Brazil

Group G Streptococcus has been implicated as a causative agent of pharyngitis in outbreak situations, but its role in endemic disease remains elusive. We found an unexpected inverse association of Streptococcus dysgalactiae subsp. equisimilis colonization and sore throat in a study of 2,194 children of 3 to 15 years of age in Salvador, Brazil.

An outbreak of food-borne group A Streptococcus (GAS) tonsillopharyngitis among residents of a dormitory

Epidemics of food-borne pharyngitis due to group A Streptococcus are rarely reported. Here we present an outbreak of food-borne tonsillopharyngitis in female dormitories in the Islamic Republic of Iran. Throat swabs and cultures were performed on a number of patients, and of specimens from the nasopharynx and hands of staff who were involved in food processing. We planned a case-control study for assessing the source of epidemics. 11 out of 17 throat swabs of students were positive for Streptococcus group A and also 2 throat samples from asymptomatic cooks were positive. A DNA fingerprinting study showed that Streptococcus group A strains of 11 students and 1 cook had the same T agglutination pattern and M protein factor (M3/T13). It is suggested that group A streptococci as well as group C and G streptococci can cause epidemic food-borne pharyngitis. Regular health surveillance of food handlers and food preparation processes are important for prevention of such outbreaks.

Beta-lactam failure in treatment of two group G Streptococcus dysgalactiae subsp. equisimilis Pharyngitis patients

We present two cases of exudative pharyngitis due to Streptococcus dysgalactiae subsp. equisimilis, Lancefield group G. While the participation of this organism as an agent of pharyngitis is well documented, we focus on failure of beta-lactam therapy, a phenomenon that is well described for pharyngitis due to Streptococcus pyogenes. Therefore, these case reports add to our knowledge of pharyngitis caused by non-S. pyogenes streptococci.

A food-borne streptococcal sore throat outbreak in a small community

Beta-haemolytic group A streptococci (GAS) is a common cause of sore throat, usually spread person-to-person. Outbreaks related to infected food have more seldom been reported. The bacteria may originate from the throat or from wounds on the hands of persons handling the food. An outbreak in Sätila, Sweden, in April/May 2003 involving 153 individuals who fell ill after eating contaminated 'sandwich-layer cakes' was investigated in a descriptive, retrospective cohort study. Questionnaires were distributed, one immediately after the outbreak and one 3 months later. The average attack rate was 72%. 143 individuals sought medical care and 137 were treated with antibiotics. 76 individuals were ill for more than 4 days. GAS isolates of identical T-type were obtained from the throats of the patients, wounds on the caterer's fingers and also from the cakes. PFGE banding patterns of 14 representative isolates were identical, as well as the emm-sequence type, emm 89, of 3 chosen isolates. The study shows that GAS from a small wound on a finger can cause illness in a large number of individuals. To prevent further outbreaks, it is important to increase public awareness of this type of transmission.

Susceptibility of beta-hemolytic streptococci to nine antimicrobial agents among four medical centers in Salt Lake City, Utah, USA

A multicenter study was performed to evaluate the susceptibility of beta-hemolytic streptococci to nine antimicrobial agents. MICs were performed in cation-supplemented Mueller-Hinton broth with 3.5% lysed sheep red blood cells according to NCCLS guidelines. A total of 646 isolates were tested: 300 (46%) group A; 170 (26%) group B; 38 (6%) group C, 35 (5%) group F; 83 (17%) group G; and 20 (3%) nongroupable. Six percent of the total isolates were resistant to one or more of the antibiotics tested. Approximately 7% of 387 strains from the University of Utah Hospital and Clinics were resistant to erythromycin. Four isolates were resistant to clindamycin. Six strains (3%) from Primary Children's Medical Center (207 tested) were resistant to one or more of the macrolides. Resistance was rare at the LDS Hospital and the Salt Lake Veteran's Affairs Hospital. Overall, resistance among beta-hemolytic streptococci in this geographic location does not seem to be a significant problem, except at the tertiary care university hospital.

Beta-haemolytic non-group A streptococci and pharyngitis: a case-control study

A case-control study was conducted to examine the association of beta-haemolytic non-group A streptococci and pharyngitis in a paediatric population (n = 502). No association could be found between disease and traditional Lancefield groups B, C, F, or G. When the analysis included the clustering of genetically related subgroups from different Lancefield groups, an association was evident for moderate and heavy quantitations of beta-haemolytic "large colony" group C and G streptococci (Streptococcus equisimilis and human biotypes of large colony group G streptococci) (p = 0.021). This study further defines a subset of the beta-haemolytic non-group A streptococci that merit recognition by both the laboratory and physician.

The epidemiology of beta-haemolytic non-group A streptococci isolated from the throats of children over a one-year period

The incidence of beta-haemolytic non-Group A streptococci (BHNAS) in the throats of a paediatric population was examined over a 1-year period. There was minimal seasonal fluctuation of Lancefield groups including species and biotypes within Groups C and G streptococci. A trend of increasing incidence with age of Streptococcus anginosus ('Streptococcus milleri') (possessing Groups C and G Lancefield antigens) was evident. A clinical impression of streptococcal pharyngitis was more common in patients with large-colony Groups C or G streptococci isolated from their throats compared with those patients where other BHNAS were isolated. This study is requisite to the planning of case control studies which are required to test the association of BHNAS (especially Groups C and G subgroups) and pharyngitis.