Vertical Transmission, Risk Factors, and Antimicrobial Resistance Patterns of Group B Streptococcus among Mothers and Their Neonates in Southern Ethiopia

Background Group B Streptococcus (GBS) contributes to maternal and neonatal morbidity and mortality by increasing intrauterine infection or vertical transmission at the time of birth. Despite many efforts to reduce the potential risk of vertical transmission, GBS remains the main cause of serious disease (neonatal sepsis, meningitis, and/or pneumonia) in vulnerable newborns during the first week of life. This study aimed to assess vertical transmission, risk factors, and antimicrobial resistance patterns of GBS among pregnant women and their neonates. Methods A facility-based cross-sectional study was conducted among mothers and their neonates from February to May 2021. A total of 201 pregnant women with their neonates participated in this study. A well-designed questionnaire was used to collect sociodemographic and clinical data. A vaginal swab from mother before delivery and neonatal nasal and ear canal swab samples were taken as soon as after delivery within 30 minutes. Vaginal swabs, neonatal ear canal, and nasal swabs were placed into Todd–Hewitt broth and incubated at 37°C for 18–24 hours at 35–37°C in 5% CO2 conditions and then subcultured on 5% sheep blood agar for 18–48 hours. Presumptive identification of GBS was made by morphology, Gram stain, catalase, and hemolytic activity on sheep blood agar plates. CAMP and bacitracin susceptibility tests were used as confirmatory tests for GBS. Data were analyzed using SPSS version 21. P value ≤0.05 was considered statistically significant. Results Vertical transmission rates of GBS (mother to neonates) were 11.9%. The prevalence of GBS among pregnant women and newborns was 24/201 (11.9%) (95% CI = 7.5–16.9) and 11/201 (5.5%) (95% CI = 2.5–9.0), respectively. The history of prolonged rupture of membranes (AOR = 3.5, CI = 2.2–18.8) and urinary tract infection (AOR = 2.9, CI = 1.7–16.3) were associated factors for maternal GBS colonization. Gestational age of <37 weeks (p=0.008), low birth weight of <2.5 kg (p=0.001), and maternal history of vaginal discharge (p=0.048) were associated factors for neonatal GBS colonization. Low antibiotic resistance was observed for erythromycin 8.6%, clindamycin 5.7%, and chloramphenicol 2.9%. Conclusion In this study, high vertical transmission (mother to neonates) rate was observed. The prevalence of vaginal GBS colonization of women at delivery was 11.9% and significantly associated with the history of prolonged rupture of membranes and urinary tract infections. Gestational age of <37 weeks, low birth weight of <2.5 kg, and maternal history of vaginal discharge were associated with neonatal GBS colonization. Hence, there is a need for antenatal culture-based GBS screening, risk factor-based interventions, and regular follow-up of drug resistance patterns for proper treatment and management of GBS.


Introduction
Globally, newborn mortality is a critical problem resulting in over 3 million deaths per year with 2/3rd occurring in the first week of life. Neonatal sepsis and pneumonia are responsible for 20% of those deaths [1]. Group B Streptococcus (GBS) is among the leading causes of early onset sepsis (EOS) worldwide with a 12% global case-fatality rate, which can be 3 times higher in low-income countries [2]. e burden of GBS early onset disease extends beyond neonatal illness and death, including such long-term impairments as vision or hearing loss and mental retardation. Over half (50%) of the survivors of bacterial meningitis diagnosed with GBS develop lifelong neurological sequelae such as increased intracranial pressure, stroke, development of cerebral palsy, blindness, deafness, epilepsy, and educational deficits in later life [3].
Group B Streptococcus colonization of the genitourinary or gastrointestinal tract of pregnant women and its transmission to the infant during the labor and delivery process is the principal risk factor for early onset invasive GBS disease [4]. During pregnancy, approximately 10-30% of women are colonized with GBS in the vagina and rectum asymptomatically as normal flora and 60% of their infants acquire this organism through the birth canal. About 30-70% of colonized mothers deliver GBS-colonized newborns and 1-2% of these develop early onset infections where heavily colonized mothers are more likely to transmit GBS to their offspring [5,6]. Infection of the fetus can occur either by an invasion of amniotic fluid following prolonged rupture of membranes (PROM) or through direct acquisition during birth [6,7]. e listed worldwide "classical" risk factors for vertical transmissions are as follows: GBS bacteriuria at any time during pregnancy, chorioamnionitis, PROM (>18 hours), prematurity (<37 weeks), prolonged labor (>12 hours), and intrapartum fever (≥38°C). Preterm infants are at 3-fold to 30-fold greater risk of developing early onset disease (EOD) compared with full-term infants, with the highest risk at lower gestational ages [3,8,9].
Universal screening of mothers for vaginal or rectal GBS colonization at 35-37 weeks of gestation and a risk-based strategy for selective intrapartum antibiotic prophylaxis (IAP) for all screen-positive women are the strategies currently recommended by CDC [1]. Streptococcus agalactiae remain fully susceptible to penicillin as well as to most β-lactams, and penicillin remains the first-choice antibiotic to prevent GBS-EOD and to treat GBS disease. However, over the last two decades, resistance to macrolides and clindamycin among invasive isolates of GBS has increased from <5% to common resistance of 20-30% [5,10]. GBS is associated with maternal and neonatal morbidity and mortality which is a major health concern; understanding the vertical transmission, risk factors and antimicrobial resistance patterns among mothers and neonates are very important for proper treatment and management of GBS since these data are lacking in the study area.

Study Design, Setting, and Population.
A facility-based cross-sectional study was conducted from February to July 2021 at Arba Minch General Hospital, Southern Ethiopia. Study populations in this study were all pregnant women at gestation and attending Arba Minch General Hospital for delivery and their neonates. An inclusion criterion was women who are with live born. Exclusion criteria include women who used antibiotics within 2 weeks of labor, physically or mentally incapable of responding, assigned for caesarian section, and presented with obstructed labor, hemorrhage, severe preeclampsia, or fetal distress. Vertical transmission indicates mother-neonate GBS colonization during labor (delivery) or neonatal GBS colonization from GBS colonized mother. Vertical transmission at birth was confirmed by culture of swabs taken from the ear canal and nose of a neonate as soon as possible after delivery within 30 minutes.

Data Collection.
Sociodemographic and clinical data were collected with a pretested well-designed questionnaire. Clinical/obstetrical characteristics such as gravidity, prenatal care, parity, prolonged labor, premature rupture of membrane, gestational age, prematurity, maternal fever, low birth weight, and some underlying medical conditions such as gestational diabetes mellitus and HIV were collected from pregnant mothers. Vaginal swabs were collected within 30 minutes of delivery from the mother and neonate.

Laboratory Investigations.
Vaginal swabs were collected from mothers by brushing the lower one-third of the vagina with sterile cotton-tipped swabs and swabs from neonates' nasal area and ear canal were collected within 30 minutes after birth following standard CDC guidelines for sample collection [11]. Sample swabs were placed in GBS broth (enrichment broth and transport medium) and transported to the Medical Microbiology and Parasitology Laboratory of Arba Minch University College of Medicine and Health Science for microbiological investigations.
e zones of inhibition were measured in millimeters using a ruler or caliper. e sizes of inhibition zones were graded according to the CLSI as sensitive, intermediate, or resistant to each antibiotic tested [12].

Results and Discussion
3.1. Baseline Sociodemographic Characteristics. e age of the study participants ranged from 17 to 40 years with a mean age of 24.96 SD ± 4.33. A majority (54.2%) of women participants' age was greater than 25 years (Table 1).

Prevalence of GBS among Pregnant Women and eir
Newborns.

Clinical Factors Associated with Neonatal GBS Colonization (Vertical Transmission).
Gestational age of <37 weeks (p � 0.008), low birth weight of <2.5 kg (p � 0.001), and maternal history of vaginal discharge (p � 0.048) were associated factors for neonatal GBS colonization (Table 4). ese findings are in line with studies done in India [9], Indonesia [33], Korea [32], and Guatemala [2]. us, investigating the risk factors which might be associated with vertical transmission would be useful for preventive strategies [26].

Antimicrobial Susceptibility Patterns.
In this study, low antibiotic resistance was observed for erythromycin 8.6%, clindamycin 5.7%, and chloramphenicol 2.9%. Most GBS isolates were susceptible to antibiotics (Table 5). e result of erythromycin resistance is comparable with reports from Ethiopia [34], Tanzania [21], and Brazil [35]. Clindamycin resistance is comparable with reports from Tanzania [21], Brazil [35], and Kuwait [36]. e widespread use of these antibiotics to prevent early onset GBS disease has raised concern about the development of antibiotic resistance among GBS isolates [17,37]. e drug resistance level underlines the need of carrying out antimicrobial susceptibility testing before prescription of antibiotics.

Conclusion
In our study, a high vertical transmission (mother to neonates) rate was observed. e prevalence of GBS among pregnant women and their newborns was 11.9% and 5.5%, respectively. e history of prolonged rupture of membrane and history of maternal UTI were associated factors of maternal GBS colonization. Gestational age of <37 weeks, low birth weight of <2.5 kg, and maternal history of vaginal discharge were associated factors for neonatal GBS colonization.
is study showed no drug resistance against penicillin as it is still the antibiotic of choice for treating GBS infections in Ethiopia and the first-line agent for intrapartum antibiotic prophylaxis. Low antibiotic resistance was found for erythromycin (8.6%), clindamycin (5.7%), and chloramphenicol (2.9%) which needs attention. Hence, there is a need for antenatal culture-based GBS screening, risk factor-based interventions, and regular follow-up of drug resistance patterns for proper treatment and management of GBS.

Limitation of the Study.
Serotyping, minimal inhibitory concentration of antimicrobials, and molecular characterization of GBS isolates were not performed because of budget constraints.

Abbreviations
AOR: Adjusted odds ratio CAMP: Christie, Atkins, and Munch-Peterson CDC: Center for Disease Control and Prevention CI: Confidence interval CLSI: Clinical and Laboratory Standards Institute COR: Crude odds ratio EOD: Early onset diseases EOS: Early onset sepsis IAP: Intrapartum antibiotic prophylaxis GBS: Group B Streptococcus PROM: Prolonged rupture of membranes TBH: Todd-Hewitt broth.
Data Availability e datasets generated and/or analyzed during the current study are not publicly available due to ethical and confidentiality reasons but are available from the corresponding author upon request.

Ethical Approval
Ethical clearance was obtained from the Institutional Research Ethics Review Board of Arba Minch University College of Medicine and Health Sciences. is study was conducted in accordance with the Declaration of Helsinki.

Consent
Written consent was obtained from study participants. Strict confidentiality was maintained and anonymity was kept. e study participants were told they can withdraw from the study anytime. Positive results were communicated to respective physicians for appropriate interventions. Disclosure e funding agencies had no involvement in the design of the study, data collection and analysis, interpretation of data, and writing the manuscript.