Group B streptococci in human urethral and cervical specimens

Prevalence of group B streptococcal colonization in the healthy non-pregnant population: a systematic review and meta-analysis

BACKGROUND

Colonization and transmission precede invasive group B streptococcal (GBS) disease. Data on GBS colonization prevalence, detection methods and risk factors for carriage are relevant for vaccine development and to understand GBS pathogenesis.

OBJECTIVES

To evaluate GBS colonization prevalence after the first week of life in the healthy non-pregnant population.

DATA SOURCES

Pubmed/Medline, Embase, Latin American and Caribbean Health Sciences Literature, World Health Organization Library Information System, and Scopus. Search performed 12 January 2021 with search terms related to 'GBS' and 'colonization, epidemiology, prevalence or screening' without restrictions.

STUDY ELIGIBILITY CRITERIA

All studies that reported prevalence of GBS colonization (any site) in the healthy population.

PARTICIPANTS

All individuals (>6 days of age), with no indication of pregnancy, invasive disease or severe underlying immunological co-morbidities.

METHODS

Logit transformation and a random effects model (DerSimonian and Laird) were used to pool colonization estimates. Subgroup analysis and meta-regression on a priori determined subgroups were performed.

RESULTS

We included 98 studies with 43 112 participants. Our search identified 9309 studies of which 8831 were excluded based on title and abstract and 380 after reading the full text. Colonization rates varied considerably between studies (I² = 97%), which could be partly explained by differences in culture methods (R² = 27%), culture sites (R² = 24%), continent (R² = 10%) and participant's age (R² = 6%). Higher prevalence was found with selective culture methods (19%, 95% CI 16%-23% versus non-selective methods 8%, 95% CI 6%-9%; p < 0.0001). Colonization rates were highest in rectum (19%, 95% CI 15%-24%), vagina (14%, 95% CI 12%-17%) and urethra (9%, 95% CI 5%-18%). In participants with negative rectal cultures, 7% (95% CI 5%-9%) had GBS cultured from another niche. Colonization prevalence was lower in children (6 months to 16 years; 3%, 95% CI 2%-5%) compared with adults (16%, 95% CI 14%-20%; p < 0.0001). Using selective culture methods in adults resulted in a prevalence of 26% (95% CI 19%-33%) rectal, 21% (95% CI 17%-25%) vaginal and 9% (95% CI 6%-14%) urethral colonization.

CONCLUSION

The rectum is the most common body site colonized by GBS. The best approach to screen for any GBS colonization is to screen multiple body sites using selective culture methods.

The epidemiology of vaginal colonisation with group B streptococci in a sexually transmitted disease clinic

OBJECTIVE

To determine whether Group B streptococcus (GBS) infection is sexually transmitted and whether colonisation with GBS could be related to vaginal symptoms or signs.

STUDY DESIGN

In 432 consecutive female patients visiting a Rotterdam STD clinic a structured sexual and gynaecological history was taken. An extensive search was done for sexually transmitted diseases, bacterial vaginosis and vaginal candidosis. A vaginal swab was taken for bacterial culture. A case-control study was performed on a subset of data.

RESULTS

Twelve percent of patients were colonised with GBS. No significant correlation was found between sexual behaviour variables and GBS colonisation. Vaginal colonisation with GBS was not correlated with vaginal signs or symptoms.

CONCLUSIONS

In our study, vaginal colonisation with GBS was not correlated with any of the epidemiological variables previously reported. Sexual contact does not seem to be the principal way of transmitting GBS. Our findings confirm the general opinion that vaginal colonisation with GBS usually does not cause any vaginal symptoms.

Colonization of human genital tract by Streptococcus agalactiae

This bacteriological study involved 92 young married couples who required medical help because of infertility. Colonization of male urethra or the presence of Streptococcus agalactiae in the ejaculate was detected in 9.78% of men. Vagina or vagina and cervix were colonized in 4.35% of women. Oral application of phenoxymethylpenicillin temporarily eliminated S. agalactiae from the genital tract of all colonized partners. Repeated colonization occurred 3-7 months later, in three cases by different serotypes compared with pretreatment period, in one case by the same serotype.

Microflora of the urethra in adolescent boys: relationships to sexual activity and nongonococcal urethritis

Urethral cultures were obtained from 90 adolescent youth, 16 of whom denied previous sexual activity. Among the sexually active boys was a group of 32 with clinically significant pyuria, consistent with the diagnosis of urethritis, on a first-part urinalysis (FPU) specimen. To relate differences in urethral microflora to sexual activity, 42 sexually active patients with a negative FPU were compared with the never sexually active group. The profile of anaerobic, but not aerobic, bacteria isolated from the urethra was related to the presence or absence of previous sexual activity. Mycoplasma species and Ureaplasma urealyticum were isolated from sexually active patients only, and may be markers of sexual activity in adolescent boys. Of the 32 patients with FPU evidence of urethritis, 22 (69%) had cultures positive for Chlamydia trachomatis, and an additional three (9%) had cultures positive for Neisseria gonorrhoeae. The findings in sexually active patients with a positive FPU were otherwise similar to those of sexually active patients without evidence of urethritis. C. trachomatis appears to be the most important agent of urethritis among adolescent boys with a positive FPU.

The in vitro activity of ampicillin, amoxicillin, cephalexin, nitrofurantoin, sulphadiazine and trimethoprim against Streptococcus agalactiae isolated from urinary and other infections

The minimum inhibitory concentrations (MIC) for 100 strains of Streptococcus agalactiae varied as follows: ampicillin 0.1 to greater than 1 mg/l, amoxicillin 0.03 to 0.5 mg/l, cephalexin 2 to greater than 16 mg/l, nitrofurantoin 8 to greater than 64 mg/l, sulphadiazine all greater than 500 mg/l and trimethoprim less than 3.9 to greater than 250 mg/l. The MICs of the beta-lactams were not affected by inoculum density. Amoxicillin was 2.5 times as active as ampicillin. Sulphadiazine and trimethoprim acted synergistically, and the average factor of potentiation exceeded 5.9. The growth curves and drug susceptibilities of 19 strains isolated from urine were similar to those of the 81 strains isolated from other sources.

Several factors influencing the colonization of group B streptococci--rectum probably the main reservoir

Women (1 268) attending a gynaecological clinic or a venereal disease clinic had positive cultures of group B streptococci from urethra in 27.8% and from rectum in 29.4%. The colonization rate was highest in patients from the venereal disease clinic (p less than 0.001). In a study of 405 of the females at different parts of the menstrual cycle group B streptococci were detected during the last half of the cycle in specimens from cervix in 18%, from urethra in 29% (p less than 0.005), and from rectum in 35% (p less than 0.001). The correlation between contraceptive methods and isolation of group B streptococci was investigated for 435 women. Females with intrauterine devices but not those using oral contraceptives had a significantly increased colonization rate genitally. The colonization rate of group B streptococci was also studied in 271 women using sanitary tampons and 129 women using sanitary towel. Those using tampons were significantly more often colonized. Cultures for Neisseria gonorrhoeae were performed from 380 patients but no correlation between N. gonorrhoeae and group B streptococci was found. The study supports the view that rectum and not the genito-urinary tract is the main reservoir of group B streptococci in females, that genital colonization mainly represents contamination from the gastrointestinal flora and sexual transmission is only one of many factors influencing the colonization rate.

Quantitation of antibodies against group B streptococci, Types Ia, Ib and III in sera from different groups of individuals: high antibody levels in sera from venereal disease clinic patients

Sera from 3 groups of individuals were investigated for antibodies to group B streptococci (GBS) types Ia, Ib and III using radiolabelled protein A: 45 girls, aged 1 to 12 years; 123 non-pregnant gynecological outpatients, aged 15 to 42 years; and 96 female venereological disease (VD) clinic patients, aged 15 to 54 years. The two groups of adults had higher antibody levels against type Ia than the girls, while no difference was found between the two adult groups in this respect. On the other hand, the VD patients had higher levels of antibodies against type Ib than the girls and the gynecological patients; the gynecological patients did not differ from the girls as regards anti-Ib antibodies. The antibody levels against type III were higher among the VD clinic patients than among the gynecological patients, who in turn had higher levels than the girls. Thus, the adults showed higher levels of antibodies against 2 of the 3 GBS types than did the girls. Furthermore, the VD clinic patients had higher levels against 2 of the 3 GBS types than the gynecological patients.

Quantitation of serum antibodies to surface antigens of group B streptococci types Ia, Ib, and III: low antibody levels in mothers of neonatally infected infants

A method has been developed for the detection in human sera of antibodies to surface antigens of group B streptococci (GBS), types Ia, Ib, or III. The sera were absorbed with GBS type II and then added to a suspension of GBS of the type against which antibodies were to be measured. After incubation and washing of the bacteria, the antibodies present on the surface of the cells were quantitated with radiolabelled protein A. Antibodies of IgG class were detected, probably specific for types Ia, Ib, or III, with the exception that the Ib GBS suspension used could detect some antibodies to type Ia. With this method it was found that 6/7 mothers to infants with GBS septicemia had low levels of serum antibodies to the infant's type of GBS. Urogenital carriers of GBS, giving birth to neonatally healthy infants, had higher serum antibody levels against the colonizing type.

Prevalence of group B beta-hemolytic streptococci in the male urethra

To evaluate the carrier rate of group B beta-hemolytic streptococci in males, we studied urethral swabs collected from 116 venereal disease (V.D.) clinic patients and 90 medical students. The prevalence rates for colonization in these groups were 8.6 and 2.2% respectively (statistically significant difference). The colonization rate in V.D. patients was higher in those with gonococcal infection than in those without but the difference was not statistically significant. Rates in patients with and without urethral symptoms were the same.

Group B streptococcal carriage in Nigeria

1038 patients of different age groups and clinical conditions attending three large hospitals in Ibadan between August 1977 and December 1978 were screened for group B streptococcal carriage. 132 (12.7%) of these patients were found to be colonized by this organism. A breakdown of the colonization rates was: in women--19.3% during the first and second trimesters of pregnancy, 17.6% during labour (third trimester) and 19% among STD patients; in adult males--9% among STD patients and nil among patients without STD; in newborns--4.7%. Type III was found most frequently (56.1%)) and there was a high incidence of R and X strains and of strains with only Ic protein. Type Ia streptococci were sensitive to penicillin G, ampicillin, erythromycin and cephalothin. Only 74.2% of the strains were sensitive to tetracycline.

Neonatal septicemia resulting from group B streptococci: a case report

A case of neonatal septicemia resulting from group B Streptococcus, type Ic is reported. The infection occurred in a premature infant delivered by cesarean section, which followed fetal distress. The same organism was isolated from a high vaginal swab taken from the mother who had had premature rupture of the membranes 48 hours before admission to the hospital. Both infant and mother made satisfactory recoveries. This is the first case of neonatal group B streptococcal infection reported from Nigeria.

The prevalence of group B streptococci in human urogenital secretions

Urogenital secretions from a total of 510 patients (153 female and 151 male venereological patients, 123 gynaecological patients and 83 gynaecologically normal women) have been examined for group B streptococci (B-str.) and gonococci. The prevalence of B-str. (32%) among the female venereological patients was significantly higher than among the gynaecological patients (21.1%) and normal women (18.0%). Urethral samples gave a higher recovery rate of B-str. than cervical samples. A significant correlation was demonstrated between the presence of B-str. and the diagnosis of vaginitis in the gynaecological material. Fermentation types of B-str. isolated from urogenital patients differed considerably from the types prevalent in bovine isolates.

Upper respiratory tract spread of group B streptococci type I b in a kindergarten

In a kindergarten with 42 children and 17 female staff members, an epidemic of group B streptococcal carriage in the upper respiratory tract occurred. In the middle of February 1978, 6 children and 5 adults carried type I b streptococci in the throat while only 2 of these 11 were carriers 2 weeks later. Only one other streptococcus, belonging to type II, was found in the throat specimens. Five strains other than type I b were found in the urogenital tract of the staff. Three type I b throat carriers were also urogenital carriers of this type. The spread of type I b streptococci could have resulted from co-spreading with other upper respiratory tract pathogens found, including group A streptococci of type 12. Haemophilus influenzae, Branhamella catarrhalis and pneumococci. Estimation of antibodies with radiolabelled protein A indicated an immune response to type I b, but not to types I a, II or III group B streptococci in the staff compared with healthy blood donors.

Localization of group B beta-hemolytic streptococci in the female urogenital tract

Isolation rates of group B streptococci were determined for various sites in 100 women attending a Special Urology (VD) Clinic. Standard procedures were used for the collection of specimens, all of which were processed using a selective medium. Specimens from the urethra and lower vagina yielded significantly higher percentages of isolations than those collected from the cervix, upper vagina, and rectum. Although lower vaginal cultures yielded more positive results than urethral cultures, the difference was not significant.

Rectal colonization with group B streptococci: relation to urogenital carriage

Urethral, cervical and rectal specimens were taken from 92 females and urethral and rectal swabs from 46 males attending a venereological outpatient department. The frequencies of group B streptococci were, in the women: urethra 24%, cervix 14% and rectum 17%; in the males: urethra 22% and rectum 7%. These findings, supported by the results of serotyping, clearly demonstrate that the human urethra is an important site of colonization and do not support the idea that the gastrointestinal canal is the primary site of acquisition.

Group B beta haemolytic streptococci in the female genital tract: a study of four clinic populations

The carrier rate of group B beta-haemolytic streptococci (GBS) was assessed in pregnant and non-pregnant women attending four clinics. Multiple sites were sampled and standard methods were used to isolate GBS. Colonization rates were highest in patients attending a venereal disease clinic but were not associated with other sexually transmitted diseases. Higher colonization rates were detected when multiple sites were sampled. Serotypes II and III occurred most frequently.

Typing of group B streptococci from the throat and urogenital tract of females

Group B streptococci were isolated from the urogenital tract of 54 of 168 patients (32%) examined at a gynecological outpatient department. 11 (7%) of the patients were group B throat carriers. In contrast to the frequency of type III group B steptococci in the urogenital tract (41% of group B streptococcal carriers) only 1 of 11 strains isolated from the throat belonged to type III. Apart from 1 patient who carried type III streptococci in the urogenital tract, all patients who were both throat and urogenital tract carriers harboured the same type in both sites. Significantly more patients who were only throat carriers of group B streptococci or harboured another type in the throat than in the urogenital tract, harboured lactose-fermenting group B streptococci as compared to patients who were only carriers of group B streptococci in the urogenital tract. These results pointed out the possible existence of "throat-preferring" and "urogenital-preferring" group B streptococci.

Group B streptococcal meningitis in previously healthy adult males

Two previously healthy men, aged 38 and 39 years, with meningitis due to group B streptococci are described. These patients are unique as only one or two adults with group B streptococcal meningitis without predisposing diseases have been reported previously.

The prevalence and persistence of group B streptococcal colonization among hospital personnel

A prospective study was performed to determine the prevalence and persistence of group B streptococcal colonization among obstetric (high-risk) and nonobstetric (low-risk) personnel. Seventy-four individuals participated in the study and the following sites were sampled: throat, rectum, vagina (females) and anterior urethra (males). The overall colonization rate was 32.4% and no statistical difference was found between high- and low-risk groups. The most frequently recovered serotypes were type III (37.5%) and type II/Ic (33.3%). Individuals older than 30 years were more likely to carry type II/Ic, whereas personnel in their twenties were most frequently colonized with type III. The rectum was the most frequently colonized site (83.3%). The vagina/urethra was colonized in 62.5% and the throat in 8.4% of carriers. Twenty-three culture-positive individuals were recultured from all sites three to six months later and persistent colonization was found in 56.5%. There was no statistical difference in persistence between the high- and low-risk groups. Type III carriers tended to become culture-negative, whereas type II/Ic carriers were significantly more likely to remain colonized with group B streptococci.

Streptococcus agalactiae in urinary tract infections

Streptococcus agalactiae was found to be the cause of approximately 1% of urinary tract infections in a London teaching hospital in the 2 years studied. Of the forty-eight patients with this infection, forty-three were female. In nine patients the infection followed renal transplantation while in nine others it occurred in the presence of chronic renal failure. The rest, who included seven females who developed the infection following hysterectomies, had other clinical conditions which could have predisposed to such infections. The rarity of urinary tract infection by S. agalactiae is in contrast to the high frequency with which the organism colonizes the normal urethra. Serotypes III and II were the predominant isolates in these patients with urinary tract infections; this corresponds to the distribution of the different serotypes in the genito-urinary tract of normal individuals.

The persistence of group B streptococci in families

Four years ago the relative occurrence of group B streptococci was studied in a group of 118 term pregnant women of which 17 were B-streptococcal carriers. Of these, 15 were investigated in connection with the delivery. 11 of these women were reexamined 45-50 months after delivery together with their families. A high frequency of positive cultures without symptoms (50%) was found in this small group of women and their husbands compared with male and female control groups. Persistence seems to be common, a fact to be remembered in subsequent pregnancies.