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

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.

Group B streptococcus carriage and vulvovaginal symptoms: causal or casual? A case-control study in a GUM clinic population

OBJECTIVES

The isolation of group B streptococcus (GBS) on routine swabs taken from genitourinary medicine (GUM) clinic attendees is a common finding. The relation of GBS to vulvovaginal symptoms is unclear, creating confusion about management. This case-control study tested the hypothesis that detection of GBS on routine clinical specimens is not causally related to vulvovaginal symptoms in female GUM clinic attendees.

METHODS

Data were collected on all female GUM clinic attendees who had GBS isolated from anogenital swabs between July 1999 and July 2001. Controls were randomly selected from all new and rebooking female GUM clinic attendees. Controls were group matched for age with cases and were included only if a sexual health screen was performed and the results of this were available.

RESULTS

118 cases and 308 controls were identified during the study period. There was no significant difference between cases and controls in patient demographic or behavioural characteristics, the presence of genital co-infection, or vulvovaginal symptoms. There was no relation between symptoms and quantitative growth of GBS reported by the laboratory in either cervical or urethral swabs. Only nine cases had high vaginal swabs taken, in whom there was a significant association between a heavy growth of GBS and vulvovaginal symptoms (p=0.008).

CONCLUSION

The isolation of GBS from routinely collected genital swabs in female attendees of a GUM clinic is not causally related to vulvovaginal symptoms. We recommend that patients should receive this advice and should not be treated with antibiotic therapy for this indication.

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.

Perinatal screening for group B streptococci: cost-benefit analysis of rapid polymerase chain reaction

OBJECTIVE

To evaluate the costs and benefits of a group B streptococci screening strategy using a new, rapid polymerase chain reaction test in a hypothetical cohort of expectant mothers in the United States.

DESIGN

Cost-benefit analysis using the human capital method. We developed a decision model to analyze the costs and benefits of a hypothetical group B streptococci screening strategy using a new, rapid polymerase chain reaction test as compared with the currently recommended group B streptococci screening guidelines-prenatal culture performed at 35 to 37 weeks or risk-factor-based strategy with subsequent intrapartum treatment of the expectant mothers with antibiotics to prevent early-onset group B streptococcal infections in their infants.

PARTICIPANTS

A hypothetical cohort of pregnant women and their newborns.

INTERVENTIONS

Screening strategies for group B streptococci using the new polymerase chain reaction technique, the 35- to 37-week culture, or maternal risk factors.

OUTCOME MEASURES

Infant infections averted, infant deaths, infant disabilities, costs, and societal benefits of healthy infants.

RESULTS

A screening strategy using the new polymerase chain reaction test generates a net benefit of $7 per birth when compared with the maternal risk-factor strategy. For every 1 million births, 80 700 more women would receive antibiotics, 884 fewer infants would become infected with early-onset group B streptococci, and 23 infants would be saved from death or disability. The polymerase chain reaction-based strategy generates a net benefit of $6 per birth when compared with the 35- to 37-week prenatal culture strategy and results in fewer maternal courses of antibiotics (64 080 per million births), fewer perinatal infections with early-onset group B streptococci (218/million), and a reduction in 6 infant deaths and severe infant disability per million births. The benefits hold over a wide range of assumptions regarding key factors in the analysis.

CONCLUSIONS

Although additional clinical trials are needed to establish the accuracy of this new polymerase chain reaction test, initial studies suggest that strategies using this test will be superior to the other 2 strategies. Using the rapid polymerase chain reaction test becomes less attractive as the cost of the test increases. The test's greatest strengths lie in its ability to identify women and infants at risk at the time of labor, thereby decreasing the number of false-positives and false-negatives seen with the other 2 strategies and allowing for more accurate and effective intrapartum prophylaxis.

Risk factors for early-onset group B streptococcal sepsis: estimation of odds ratios by critical literature review

OBJECTIVE

To identify and to establish the prevalence of ORs factors associated with increased risk for early-onset group B streptococcal (EOGBS) infection in neonates. streptococcal (EOGBS) infection in neonates.

STUDY DESIGN

Literature review and reanalysis of published data.

RESULTS

Risk factors for EOGBS infection include group B streptococcal (GBS)-positive vaginal culture at delivery (OR: 204), GBS-positive rectovaginal culture at 28 (OR: 9.64) or 36 weeks gestation (OR: 26. 7), vaginal Strep B OIA test positive at delivery (OR: 15.4), birth weight </= 2500 g (OR: 7.37), gestation <37 weeks (OR: 4.83), gestation <28 weeks (OR: 21.7), prolonged rupture of membranes (PROM) >18 hours (OR: 7.28), intrapartum fever >37.5 degrees C (OR: 4.05), intrapartum fever, PROM, or prematurity (OR: 9.74), intrapartum fever or PROM at term (OR: 11.5), chorioamnionitis (OR: 6.43). Chorioamnionitis is reported in most (88%) cases in which neonatal infection occurred despite intrapartum maternal antibiotic therapy. ORs could not be estimated for maternal GBS bacteriuria during pregnancy, with preterm premature rupture of membranes, or with a sibling or twin with invasive GBS disease, but these findings seem to be associated with a very high risk. Multiple gestation is not an independent risk factor for GBS infection.

CONCLUSIONS

h Mothers with GBS bacteriuria during pregnancy, with another child with GBS disease, or with chorioamnionitis should receive empirical intrapartum antibiotic treatment. Their infants should have complete diagnostic evaluations and receive empirical treatment until infection is excluded by observation and negative cultures because of their particularly high risk for EOGBS infection. Either screening with cultures at 28 weeks gestation or identification of clinical risk factors, ie, PROM, intrapartum fever, or prematurity, may identify parturients whose infants include 65% of those with EOGBS infection. Intrapartum screening using the Strep B OIA rapid test identifies more at-risk infants (75%) than any other method. These risk identifiers may permit judicious selection of patients for prophylactic interventions.

Group B streptococcal disease in newborns: a global perspective on prevention

Group B Streptococcus (GBS) is an important cause of neonatal sepsis in many areas. Although incidence data are available for a minority of countries, the magnitude of illness due to this bacterium appears to vary substantially. Disease may vary due to the prevalence of asymptomatic GBS colonization, the virulence of circulating strains, the frequency of predisposing conditions such as low birth weight, or differences in obstetric practices. Approaches to prevention of neonatal GBS disease include administering antibiotics to high risk mothers intrapartum, use of intrapartum vaginal disinfectants, development of GBS vaccines, and nonspecific approaches. Determinants of prevention policies in a given area depend on the incidence of disease, the structure of health care delivery, cost-effectiveness, and cultural attitudes. Much GBS disease among newborns is now preventable, yet data on incidence are needed to guide selection of appropriate approaches to disease prevention.

Streptococci and the genital tract

Streptococci of Lancefield Group B (GBS) are known to cause maternal sepsis and neonatal infection, whereas streptococci Lancefield Group A (GAS) cause vulvo-vaginitis in both children and adults. Prevalence of SGB colonization of the lower genital tract of normal women is between 4-18%, with higher rates found in hospital personnel and delivery rooms. Such high carriage rates may be a significant factor in nosocomial transmission of GBS to neonates. Symptomatic infection is uncommon and usually secondary to other pathological states. Amnionitis is a complication of vaginal carriage of GBS and there is now evidence that chorioamnionitis is associated with pre-term labour and its attendant problems. GBS infection of the male genitalia has also been described. Intrapartum chemoprophylaxis has been shown to prevent early onset GBS disease of the neonate. Prevalence of GAS in the genital tract is lower than that for GBS, but is more likely to be symptomatic. The response to penicillin is usually prompt. Optimal drug regimens need to be determined, particularly for use in pregnancy.

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.

Group B streptococcus

Over the past 25 years group B streptococci have become established as one of the main bacterial pathogens of the neonate in Western Europe and the United States. The attack rate of 0.25/1,000 live births found by Mayon White in Great Britain1 appears typical of many European countries. However, in some centers in the United States attack rates can be over 10 times higher.

Two types of neonatal group B streptococcus (GBS) diseases exist, “early” and “late” onset. Early onset disease usually presents within the first few days of life. Often the most serious infections are present at birth or seen within a few hours. Early onset disease presents with pneumonia, respiratory distress and shock. Bacteremia is normally present and meningitis may occur. Mortality is high (50% to 75%). The portal of entry is probably the respiratory tract. Infants normally acquire the infecting organism from their mothers. Heavy maternal and infant colonization, prolonged rupture of membranes, prematurity, and obstetric complications are all risk factors.

Delayed onset disease, as its name suggests, presents after the first week of life, primarily with bacteremia and meningitis. Mortality is much lower than for the early onset form, but still appreciable for a bacterial infection (14% to 18%). Its epidemiology is uncertain.

Group B streptococcal colonisation and the outcome of pregnancy

Vaginal colonisation of pregnant women with group B streptococci (GBS) was not related to age, parity or blood group. There were marked differences between racial groups, Asians having a low colonisation rate and Negroes a high rate. Vaginal GBS colonisation was associated with intrapartum pyrexia, but not with preterm labour, premature rupture of membranes or other complications in labour. Group B streptococci may be an important cause of bacteriuria in pregnancy and their effect on the outcome of pregnancy as urinary pathogens needs further evaluation.

Carriage and transmission of group B streptococci among STD clinic patients

High rates of carriage of group B streptococci were found among men (38%) and women (42.3%) attending a clinic for sexually transmitted diseases. Swabs from the perineal/anorectal area gave the highest isolation rate and those from the urethra the lowest. The subpreputial sac was an important site for carriage of the organism, and there was a strong association between streptococcal isolation and balanitis. Of 92 couples studied, neither partner was colonised with group B streptococci in 36. In a further 36 one or other was colonised and in 20 both were colonised. Serotyping and phage typing showed that only three of these 20 couples were colonised with similar strains of the organism.

Carriage of Streptococcus agalactiae in women and neonates and distribution of serological types: a study in Brazil

The prevalence of group B streptococcal carriage was evaluated in nonpregnant women and in mothers and their offsprings. The overall carriage rate of group B streptococci at one site was 18.2%. Streptococci were recovered from one or more of the sites sampled in 25.6% of mothers and 15.4% of newborn infants. The maternal genital carriage rate was 18.6%, and acquisition of the organism from the mother was assessed by serological typing of group B streptococcal isolates in the mother-infant pairs. A cervical carriage rate of 16.3% was seen in nonpregnant women.

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.

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.