BMC Public Health 2009, 9:437 http://www.biomedcentral.com/1471-2458/9/437 The association between GBS colonisation rate in neonates and maternal obstetric factors is summarized in Table 3. Prolonged duration of labour was significantly shown to influence GBS colonisation in neonates; 6/17 (35.3%), P < 0.001. The rate of GBS colonisation was higher 14/139 (10.1%) in neonates born by spontaneous vaginal delivery compared to 2/41 (4.9%) among neonates born by caesarean section, P > 0.05 however, was not statistically significant. Nearly all women (15/16) who had history of taking antibiotic during labour had neonates with no GBS colonisation. The time taken between antibiotic intake and delivery was approximately one to four hours for those who were given intravenous antibiotics (ampicillin or ceftriaxone) at labour ward. The reasons for antibiotic administration included; prolonged duration of labor with fetal distress, caesarean section, and intrapartum fever. Table 4 presents the antimicrobial susceptibility pattern of GBS isolated from different sites. The GBS isolates were all (100%) sensitive to vancomycin and ampicillin, (90%- 100%) sensitive to penicillin G and ciprofloxacin and (80-90%) sensitive to clindamycin, erythromycin, cotri- moxazole and ceftriaxone. Discussion This study at the MNH in Dar es Salaam, Tanzania shows the overall prevalence of GBS among pregnant women and neonates to be 23% and 8.9%, respectively. These findings are consistent with reports from other developing countries [8,13], but lower than those reported in Zimba- bwe 31.6% and Trinidad 32.9% [9,14], indicating signifi- cant country variations [15]. The variations between countries could possibly be due, at least in part, to differ- ences in sampling sites and techniques. For instance, in this study due to investigating sexually transmitted infec- tions, we used high vaginal swabs which is in keeping with some previous studies [9,16], while others investiga- tors have used lower third of vaginal site [5,6]. Other var- iations in isolation frequency could be due differences in culture methods, and type of culture media used as well as populations investigated [4]. In this study vaginal carriage rate (12.3%) was higher than rectal colonisation rate (5%), which is comparable to a study done in Zimbabwe by Moyo et al [13] in which vag- inal and rectal colonisation rates were 12.6% and 6.3%, respectively. The fact that GBS was at times isolated from one and not the other site clearly indicate that it is impor- tant to sample both vagina and rectum when screening for GBS carriage in pregnant women. Notably, there was loss of 120 neonates to follow up due to the fact that mothers delivered in other facilities. One twenty neonates made 40% of neonates and this could have affected the reported neonatal colonisation rate. Table 3: Association between obstetric factors and GBS colonisation rate in neonates (n = 180) Total Number GBS isolated Percentages P-value Variable Mode of delivery Vaginal delivery Caesarean Time of membrane rupture ≤ 18 hrs >18 hrs Intrapartum fever No Yes Antibiotic use before/during labour No Yes Duration of labour ≤ 12 hrs >12 hrs Weight of baby <2.5 kg ≥ 2.5 kg 139 41 178 2 177 3 164 16 163 17 20 160 14 2 16 0 16 0 15 1 10 6 1 15 10.1 4.9 9 0 9 0 9.1 6.3 6.1 35.3 5 9.4 0.61 0.65 0.58 0.69 0.00 0.51 Page 5 of 7 (page number not for citation purposes)