Frequencies of streptococci of groups A, B, C, D, and G in urethra and cervix swab specimens from patients with suspected gonococcal infection

Interspecies communication among commensal and pathogenic streptococci

Quorum sensing (QS) regulates diverse and coordinated behaviors in bacteria, including the production of virulence factors, biofilm formation, sporulation, and competence development. It is now established that some streptococci utilize Rgg-type proteins in concert with short hydrophobic peptides (SHPs) to mediate QS, and sequence analysis reveals that several streptococcal species contain highly homologous Rgg/SHP pairs. In group A streptococcus (GAS), two SHPs (SHP2 and SHP3 [SHP2/3]) were previously identified to be important in GAS biofilm formation. SHP2/3 are detected by two antagonistic regulators, Rgg2 and Rgg3, which control expression of the shp genes. In group B streptococcus (GBS), RovS is a known virulence gene regulator and ortholog of Rgg2, whereas no apparent Rgg3 homolog exists. Adjacent to rovS is a gene (shp1520) encoding a peptide nearly identical to SHP2. Using isogenic mutant strains and transcriptional reporters, we confirmed that RovS/SHP1520 comprise a QS circuit in GBS. More important, we performed experiments demonstrating that production and secretion of SHP1520 by GBS can modulate Rgg2/3-regulated gene expression in GAS in trans; likewise, SHP2/3 production by GAS can stimulate RovS-mediated gene regulation in GBS. An isolate of Streptococcus dysgalactiae subsp. equisimilis also produced a secreted factor capable of simulating the QS circuits of both GAS and GBS, and sequencing confirms the presence of an orthologous Rgg2/SHP2 pair in this species as well. To our knowledge, this is the first documented case of bidirectional signaling between streptococcal species in coculture and suggests a role for orthologous Rgg/SHP systems in interspecies communication between important human pathogens.

Pathogenic streptococci, such as group A (GAS) and group B (GBS) streptococcus, are able to persist in the human body without causing disease but become pathogenic under certain conditions that are not fully characterized. Environmental cues and interspecies signaling between members of the human flora likely play an important role in the transition to a disease state. Since quorum-sensing (QS) peptides have been consistently shown to regulate virulence factor production in pathogenic species, the ability of bacteria to signal via these peptides may prove to be an important link between the carrier and pathogenic states. Here we provide evidence of a bidirectional QS system between GAS, GBS, and Streptococcus dysgalactiae subsp. equisimilis, demonstrating the possibility of evolved communication systems between human pathogens.

Fibronectin-binding protein gene recombination and horizontal transfer between group A and G streptococci

We report evidence of interspecies gene transfer between the important virulence factor genes sfbI and gfbA. Because the identified group G streptococcus gfbA types possess DNA cassettes that can be identified in a number of group A streptococcus strains, it appears that homologous recombination is occurring between these species.

Report of cases of and taxonomic considerations for large-colony-forming Lancefield group C streptococcal bacteremia

Traditionally, group C streptococci include four species: Streptococcus equisimilis, S. zooepidemicus, S. equi, and S. dysgalactiae, the first three of which are group C beta-hemolytic streptococci (GCBHS). However, many of the beta-hemolytic streptococci carrying Lancefield group C antigen isolated from clinical specimens are S. milleri. These organisms can be differentiated by colony size. We retrospectively collected data concerning large-colony-forming GCBHS bacteremia that occurred during a period of 8 years at the Massachusetts General Hospital. A total of 222 cases of beta-hemolytic streptococcal bacteremia were identified; data on the Lancefield grouping were available in 192 cases: 45 cases (23.6%) were group A, 96 cases (50%) were group B, 7 cases (3.6%) were group C (large colony forming), and 44 cases (22.9%) were group G. The medical records for cases of large-colony-forming GCBHS bacteremia were reviewed. In one case, the isolate was thought to be a contaminant; the other six cases are reported (five males and one female; mean age, 55 years). All patients had severe underlying conditions, and none had a history of exposure to animals. The clinical syndromes included two cases of cellulitis and one case each of endocarditis, myocardial infarction complicated by infection, pneumonia, and myofasciitis. The diagnoses for two patients with endovascular infections were delayed. Three of the six patients had fatal outcomes, and other two, after prolonged hospitalization, were transferred to a long-term rehabilitation center. We concluded that the severe outcomes reflect delay in diagnosis and treatment as well as the severity of the underlying diseases. The taxonomy of GCBHS is discussed. More reports differentiating large- and small-colony-forming GCBHS are needed.

Patterns of carriage of group B streptococci in genitourinary medicine clinic patients

Anogenital carriage of group B streptococci was found in 46% (57/125) of men and 38% (68/179) of women attending a genitourinary medicine clinic. Colonisation with group B streptococci was more common in patients who had a history of more than one sexual partner in the preceding three months, but was not related to any previous sexually transmitted infection. Group B streptococci were isolated from either one or both partners of 28 couples, in 12 of which both partners yielded isolates that were indistinguishable by serotyping and phage typing. Colonisation with matching isolates of group B streptococci was more common in couples who had relatively stable relationships.

Vaginitis caused by nutritionally variant Streptococcus pyogenes

A nutritionally variant Streptococcus pyogenes was isolated from a vaginal specimen. The organism was isolated in essentially pure culture with a few colonies of normal vaginal flora. The bacterium was identified as Streptococcus pyogenes with the use of rapid test kits and the presence of group A antigen.

Group G streptococci in healthy school-children and in patients with glomerulonephritis in Trinidad

The group G streptococcus has generally not been considered a prominent pathogen. In a 1982 study of the colonization rate by beta-haemolytic streptococci in apparently healthy children, age 5-11 years, 25 of 69 isolates belonged to group G. This surprisingly high rate of group G colonization (14.3%) led to a retrospective study of school surveys in 1967 which showed that the colonization rate with this organism was 2.3% (range 1.3-3.5%). A review of bacitracin-sensitive streptococcal isolates from hospital admissions of patients with acute glomerulonephritis (AGN), rheumatic fever, and their siblings, between January 1967 and July 1980, was conducted. Of 1063 bacitracin-sensitive isolates, 63 were group G, and 52 of these were isolated from AGN patients and their siblings, i.e. 7 from skin lesions of AGN patients, 40 from the throats of siblings and only 5 from the skins of the siblings. The other 11 group G isolates were from rheumatic-fever patients and their siblings. Thus, the group G colonization rate fluctuates in the population. The isolation of only group G streptococci from skin lesions of patients with AGN suggests a possible association between group G streptococcal pyoderma and acute post-streptococcal glomerulonephritis.

Group C beta-hemolytic streptococcal endocarditis: report of a pediatric case

A 9-year-old boy with a ventricular septal defect and a bicuspid aortic valve developed bacterial endocarditis due to group C streptococci. He responded to an initial antibiotic regimen of nafcillin plus gentamicin and was cured by the use of penicillin G following the isolation of the organism. The unusual nature of this case is discussed and physicians are cautioned to recognize this organism as a potential cause of infectious endocarditis in the pediatric population.

Colonization of newborns with group B streptococci: relation to maternal urogenital carriage

Urethral and cervical specimens were obtained from 786 parturients during labour. 126 women (16%) were found to be urogenital carriers of group B streptococci (GBS). Bacteriological specimens were also obtained from the throat, umbilicus and external auditory canal of their 786 infants immediately after birth, and from 671 of the infants staying at the maternity unit 4 days later. 51% (64/126) of the infants born to GBS carriers were culture-positive for GBS immediately after birth. Only 27% (6/22) of the infants born to women who were GBS culture-positive in the urethra but not in the cervix contracted GBS at the delivery, in contrast to 59% (58/85) of the infants born to combined urethral and cervical carriers (P less than 0.05). This difference in colonization rate was not related to differences in levels of antibodies to the type of GBS carried by the individual parturient. On day 4, 13% (90/671) of the infants in the maternity unit were colonized with GBS. 39% of them were colonized at birth from their mother, 12% were culture negative at birth but had become colonized by day 4 with the same type of GBS as that isolated from the urogenital tract of the mother, and 37% were GBS positive on day 4 but culture-negative at birth and the mother's specimens did not reveal GBS. The distribution of serotypes among these infants was identical with that found among the other colonized infants, indicating that they might have contracted their GBS from the other infants in the maternity unit.

Infection with Streptococcus agalactiae in a London hospital

Streptococcus agalactiae is presently the commonest beta-haemolytic streptococcus isolated from clinical material in this hospital. Between October 1974 and March 1975, 81 patients with such infections were seen. Seventeen had urinary tract infections, six had septicaemia, and one neonate had meningitis. Three of those with septicaemia were neonates and two died. The organism was also found to be a cause of pyogenic skin conditions in five patients. Isolates from throat swabs in 12 patients, from sputum in four, and from the female genital tract in 18 were considered part of the normal flora. Human strains of Str. agalactiae were found to be biochemically different from animal strains.