Newborn colonization and antibiotic susceptibility patterns of Streptococcus agalactiae at the University of Gondar Referral Hospital, Northwest Ethiopia

The 2016 Ethiopian Demographic and Health Survey (EDHS) indicates that the overall mortality rate of under five children is 67/1000 live births, with the infant mortality rate of 48% (29% neonatal and 19% post-neonatal) deaths/1,000 live births. The estimate of child mortality is 20 deaths/1000 children surviving to 12 months of age [1]. Women in the Amhara National Regional State have the fertility rate of 4.2, and infant and maternal mortality rates of 76/1000 live births and 676/100,000, respectively [2]. Asymptomatic Streptococcus agalactiae (Group B Streptococcus, GBS) recto-vaginal colonization of women is assumed to be one of the contributing factors. It is the most significant pathogen, although little is known about its epidemiology and risk in resource limited countries [3]. Since neonatal infections cause a significant proportion of deaths in the first week of life, more data are needed about the burden of neonatal colonization [4].

Since 1960s, GBS has been identified as a major public health problem that causes perinatal morbidity and mortality. It also became the most prevalent causes of fatal infections in newborns [5‐7]. The researchers estimated about 410,000 GBS cases and 147,000 stillbirths and infant deaths are estimated to occur every year. Despite containing 13% of the world's population, Africa had the highest burden with 54% cases and 65% of stillbirths and infant deaths [8]. GBS causes sepsis, pneumonia, and meningitis in neonates; bacteraemia, amnionitis, endometritis, and urinary tract infection in pregnant women [9‐11]. The Global prevalence of GBS neonatal colonization rate ranged from 1.6% in Turkey [12] to 52.9% in Pakistan [13], and South Africa took the lion share among few African reports [14]. However, evidence on GBS colonization rate of newborns largely remains sparse in the African setting, particularly in Ethiopia.

Furthermore, provision of empiric treatment brings up antibiotic resistance and stewardship issues [8]. Reports from different countries revealed the reduced susceptibility to penicillin, and the increased rate of macrolide resistance GBS isolates for the last few decades [15]. A 2005-2007 Surveillance in Argentina showed the presence of GBS isolates resistance (in minimum inhibitory concentration; MIC range μg /L) to ciprofloxacin (32-64 μg/L), levofloxacin (16-32 μg/L), ofloxacin (32-64 μg/L), and norfloxacin (32-64 μg/L), and all were susceptible to penicillin (0.06 μg/L) (16). Of the 1160 GBS isolates in Australia, 6.4% demonstrated erythromycin resistance and 4.2% to clindamycin [16]. Another study in USA revealed that all the neonatal GBS were susceptible to penicillin, vancomycin, chloramphenicol, and cefotaxime. Its resistance rates to erythromycin was 20.2%, and 6.9% to clindamycin [17]. Another study in France revealed 38.2% erythromycin and 25.6% clindamycin resistance neonatal GBS [18]. However, as is the case in several other African countries, neonatal GBS colonization in Ethiopia has not been well documented. In addition, no preventive strategies for GBS infection have been yet formulated in the study area. Thus, this study was aimed to determine the prevalence of newborn colonization with GBS, its antibiotic susceptibility profile, and associated risk factors in University of Gondar referral hospital, Northwest Ethiopia.

Our study showed that 62 (16.1%; 95% CI: 12.2-20.0) of the newborns participated in the study were colonized with GBS, which could be the possible causes to the high morbidity and mortality of neonates in the study area. This prevalence of colonization was in agreement with different studies conducted worldwide such as: France (13.9%) [26], Turkey (17.3%) [27]), South Africa (15.8%) [14] and Gambia (12.0%) [28]. Contrary to our study, other studies showed the lower prevalence of newborn colonization with GBS and some of these were Iran (1.7% to 5.5%) [29‐31], Saudi Arabia (1.0%) [32], Turkey (1.6% to 8.0%) [12, 33], Pakistan (6.0%) [13], China (4.9%) [34], India (1.3% to 3.2%) [35, 36], Korea (1.5%) [37], Bangladesh (6.3% to 7.4%; in which, the finding from umbilicus is in agreement with ours) [38, 39], Lithuania (6.4%; where 5.3% GBS were isolated from the ear swab of the newborns as it was observed in our study and 4.6% from the throat) [40], Greek (2.4%) [41], Nigeria (6.8%) [42], Tanzania (8.9%) [43] and Ethiopia (5%) [19]. The discrepancies might be associated with the Global variability of maternal colonization with GBS (differences in geography, season, IAP provision), the mode of delivery (in which newborns born by spontaneous vaginal delivery had usually more GBS colonization), and the availability of laboratory facilities and experiences of laboratories to detect GBS.

Inconsistent to our result, a lot of studies showed higher neonatal colonization with GBS, for example, studies in Poland (26.7% to 34.5%) [44, 45] and Bangladesh (38%) [39]. The regional differences, variability in the sample size, methods employed for GBS detection, availabilities of laboratory facilities, experiences of laboratory technologists, newborn body surface sites swabbed and time of sample collection (soon after birth or later) might be possibly explained the disparities. The differences could also be explained by the presence or absence of the IAP administration, variations of maternal colonization and density of GBS colony and mode of delivery.

In our study, the antibiotics susceptibility rates of GBS were 95.1%, 89.6%, 88.9%, 85.7%, 85.3%, 81.3%, 76.9%, 76.1%, 73.8%, and 34.4% to ampicillin, penicillin, ciprofloxacin, chloramphenicol, vancomycin, azitromycin, erythromycin, clindamycin, ceftriaxone, and tetracycline respectively. We identified that ciprofloxacin, chloramphenicol, vancomycin and azithromycin were the drug of choice next to ampicillin and penicillin. The GBS in the current study showed better sensitivity to azithromycin than erythromycin and clindamycin. Thus, given the recent interest in the azithromycin, it is wise to do more study on this drug and consider it as the alternative prophylaxis for the penicillin allergic laboring mothers to reduce the carriage of GBS in mothers and newborns and then to lower the risk of neonatal diseases beyond the trachoma control.

In agreement with our findings, a study in Egypt showed that 29.4% of the GBS isolated from the neonates were resistance to erythromycin and 17.6% were resistance to clindamycin [46]. Another studies conducted in different parts of the world such as, in France showed that 25.6% were resistance to clindamycin and 38.2% to erythromycin [18] and 21.4% to macrolide [47], in the USA, 20.2% to 32% were resistance to erythromycin and 6.9% to 15% to clindamycin [17, 48, 49], and in Italy, 17% were resistance to erythromycin and 15.3 % to clindamycin [50]. Another report from Tanzania revealed that the neonatal GBS were 100% susceptible to penicillin, ampicillin, vancomycin and ciprofloxacin whereas susceptibility to ceftriaxone, clindamycin and erythromycin were 93.8%, 87.5% and 81.3% respectively [43]. A study in Germany also reported that all the isolates were susceptible to beta-lactams and vancomycin while 10.1% were resistance to erythromycin and 5.7% to clindamycin [51] which are lower than our reports. This variation might be explained by the fact that the laboratory facilities and health literacy of the people in our setting are different from other developed countries.

Contrasting to the results of our study, a Chinese report revealed that all the GBS isolated from the neonates were susceptible to penicillin, but the rates of resistance to clindamycin and erythromycin were 84.0% and 88.0% [52]. These discrepancies may dictate that the rates of resistance to erythromycin and clindamycin varied among geographic regions and were notably the highest in China. Additionally, a study explained that antibiotics currently prevent an estimated 29,000 cases of early onset GBS disease per year. This approach may challenge in the low-income countries where many births take place at home, and laboratory capacity for the screening of GBS is limited [8]. The provision of antibiotics to pregnant women without screening may also contribute to the emergence of antibiotic resistance. An alternative prophylaxis failure is becoming more likely to the increasing of macrolide resistance rates among the GBS isolates. Therefore, in cases when considering these antibiotics, including azithromycin as alternatives for prophylaxis and treatment for GBS, susceptibility test should be done before the prescriptions. We also reported that among the GBS tested for MLS_B by using the double disk diffusion technique, 34.4%, 31.3%, 21.9% and 12.5% isolates had L- and M- phenotypes, cMLS_B and iMLS_B, respectively. The inducible and constitutive resistance reported in our study is lower than a study from Canada, where 40.0% of the isolates were inducible and 47.3% were constitutive resistance to clindamycin [24].

Of the possible factors associated for the colonization of the newborns that were investigated in our study, the newborns born to mothers whose education status was below tertiary level and from employed mothers had the increased risk of colonization with GBS. It could be justified by the fact that keeping personal hygiene is likely better among those people who have more education status than their counterparts. In addition, employment may increase mobility of women and expose them for different causal partnerships with different people who could be the risks for them, later becomes a source for their neonatal colonization. Being nulliparity and multigravida are among the maternal factors, and newborns who were in resuscitation and who didn`t have immediate contact with their mothers (in the neonatal intensive care unit) had also the increased risk of newborn colonization.

Congruently, different literatures presented that women with less (or no formal,/lack of) education, women of lower parity, multigravid, young maternal age (< 20 yrs), vaginal mode of delivery, intrapartum fever, prolonged premature rupture of membrane, preterm gestational age, low birth weight (< 2.5kg), and neonatal intensive care admission were associated with neonatal colonization with GBS [43, 46, 53‐56]. Likewise, a study in Tanzania showed that prolonged duration of labour had the significant association with colonization of the newborns with GBS, possibly due to the extended exposure of the newborns in the birth canal [43]. This calls for the screening of pregnant women for GBS at their 35 to 37 weeks of pregnancy and provision of IAP for those women who have been positive for GBS to reduce the chances of later neonatal colonization.

We found that maternal age, obstetric history, gestational age, sex of the newborn, HIV infection, Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) score, preterm delivery, number of antenatal care (ANC) visit, and duration of labour did not show a significant association with neonatal colonization. In agreement to this, Joachim and his co-workers in Tanzania [43] presented that prolonged premature rupture of membrane, intrapartum fever, mode of delivery and low birth weight did not influence neonatal colonization with GBS. Tsolia et al. [41] in their study reported that the multiparity (≥2 previous births) is associated with a low risk for maternal colonization with GBS. It might be explained by the numbers of participants in our study with these risk factors were small. It is useful to know that GBS could be transferred from pregnant women to newborns, and was evidenced by the fact that after the Caesarean section was done (before rupture of the membrane), molecular strain identification demonstrated that same GBS strain was found in mothers and their newborns [45]. So to prevent neonatal colonization with GBS and to increase newborn health conditions, prevention strategies should be developed and promoted in the study area.

Prevalence of newborn colonization with GBS in this study was higher than the findings reported three Decades ago in the same area. We identified that ciprofloxacin, chloramphenicol, vancomycin and azithromycin were the drug of choice next to ampicillin and penicillin. In addition, 12.5% of the isolates in our study showed inducible clindamycin resistance. Lower education status, being employed, and being nullipara and multigrapvida were the maternal factors associated with the increased risk of newborn colonization. Resuscitation and denial of the newborn`s immediate contact with their mothers were the neonatal factors which showed the increased risk of newborn colonization. So to prevent neonatal colonization with GBS, continuous health education, screening of pregnancy for GBS at the 35 to 37 weeks of gestation and provision of IAP for those positive cases for GBS should be promoted in the study area. GBS surveillance and their antibiotic susceptibility testing should also be conducted in the country by using advanced laboratory technologies.