Between August and November 2017, a total of 350 pregnant women were screened, 292 eligible pregnant women between 12 and 40 weeks gestation consented and were enrolled to participate in the study. From these, 292 questionnaires were fully filled and 292 (100%) vaginal swab samples and 288 (98.6%) anorectal swab samples collected for GBS culture. Four participants declined to have anorectal swabs collected.
Socio‑demographic characteristics
The median age of participants was 30 years (IQR 26-35). About one in five (n=55, 18.8%) were aged below 25 years, majority (n=177, 60.6%) were aged between 26 to 35 years while another one in five were aged 36 years or older (n=60, 20.5%). The median gestation age of study participants was 35 weeks (IQR 30 - 37). Less than half (n=132, 45.2%) of the participants were of gestation age 34 weeks and below while 15.1% (n=44) were term i.e. greater than 37 gestation weeks (Table 1).
Obstetric and clinical characteristics
Half of the participants (n=156, 53.4 %) were multiparous with a median parity of three pregnancies (IQR 2-4). Only 53 (18.2%) of the pregnant women were primigravida. Approximately three quarters of participants (n=210, 71.9%) had one or more live births, however, 29 (9.9%) of participants though having been pregnant before, had never delivered a live birth (Table 1).
Table 1: Sociodemographic and obstetric characteristics of study participants
Participant characteristics
|
Total (N=292) (100%)
|
Age (Years)
|
|
≤ 25
|
55 (18.8%)
|
26 -35
|
177 (60.6%)
|
≥ 36
|
60 (20.5%)
|
Gestation age (weeks)
|
|
< 35
|
132 (45.2%)
|
35-37
|
166 (39.7%)
|
> 37
|
44 (15.1%)
|
Parity
|
|
0
|
53 (18.2%)
|
1
|
83 (28.4%)
|
>1
|
156 (53.4%)
|
Maternal GBS colonization
Out of the 292 study participants, 20.5% (n=60) tested positive to GBS recto-vaginal colonization on both culture and gram stain. GBS was cultured from vaginal swabs of 16.8% (49/292) participants while anorectal swabs of 18.8% (55/288) participants were GBS positive. On the other hand, 15.1% (44/292) of study participants had both rectal and vaginal GBS colonization.
Sociodemographic and obstetric characteristics of GBS rectovaginal colonization among pregnant women receiving antenatal care at Kenyatta National Hospital
The prevalence of GBS was highest among participants within the 26-35 years age bracket at 13.0% (n=38), approximately one in twenty participants (n=12, 4.1%) aged above 36 years were GBS colonized. Participants within the 35-37 weeks gestation bracket had the highest prevalence of GBS (n=28/292, 9.6%) followed by participants of gestational age below 35 weeks (n=26/292, 8.9%). The prevalence of GBS was lowest among participants of gestational age above 37 weeks (n=8/292, 2.1%).
The prevalence of GBS among participants with a history of stillbirth was 6.5% (n=19), abortion or ectopic pregnancy was 3.1% (n=9) while among those with history of preterm birth it was 4.1% (n=12); for participants with a history of fore water break, more than 18 hours before labour, the prevalence was 3.4% (n=10). The prevalence was 2.1% (n=6) among participants allergic to penicillin, and 1.0% (n=3) among HIV-positive participants; participants with white coloured vaginal discharge had the highest GBS colonization with a prevalence of 11.0% (n=32) followed by clear coloured vaginal discharge with a prevalence of 4.5% (n=13) (Table 2).
Table 2: Sociodemographic and obstetric characteristics of GBS colonized women
Sociodemographic and obstetric characteristics
|
GBS culture results
|
Negative (N=232)
|
Positive (N=60)
|
P
|
n (%)
|
n (%)
|
Maternal age (Years)
|
|
|
0.864
|
<26
|
45 (15.4%)
|
10 (3.4%)
|
26 -35
|
139 (47.6%)
|
38 (13.0%)
|
>36
|
48 (16.4%)
|
12 (4.1%)
|
Gestation age (weeks)
|
|
|
0.323
|
<35
|
106 (36.3%)
|
26 (8.9%)
|
35-37
|
88 (30.1%)
|
28 (9.6%)
|
>37
|
38 (13.0%)
|
6 (2.1%)
|
Parity
|
|
|
0.499
|
0
|
43 (14.7%)
|
10 (3.4%)
|
1
|
69 (23.6%)
|
14 (4.8%)
|
>1
|
120 (41.1%)
|
36 (12.3%)
|
Number of prior live births if parity >0
|
|
|
0.566
|
0
|
25 (8.6%)
|
4 (1.4%)
|
>0
|
164 (56.2%)
|
46 (15.8%)
|
Number of prior stillbirths
|
74 (25.3%)
|
19 (6.5%)
|
0.935
|
History of pregnancy loss in prior pregnancies (abortion or ectopic)
|
23 (7.9%)
|
9 (3.1%)
|
0.308
|
History of preterm birth in prior pregnancy
|
45 (15.4%)
|
12 (4.1%)
|
0.945
|
Rupture of membranes for >18 hours before labour in prior pregnancy
|
48 (16.4%)
|
10 (3.4%)
|
0.688
|
Past history of neonatal death in first week of birth
|
23 (7.9%)
|
9 (3.1%)
|
0.526
|
Past history of neonatal infection after birth
|
25 (8.6%)
|
5 (1.7%)
|
0.782
|
Fore water break in past pregnancy Rupture of membranes?
|
5 (1.7%)
|
2 (.7%)
|
0.595
|
Allergy to penicillin
|
|
|
0.051
|
Yes
|
9 (3.1%)
|
6 (2.1%)
|
Don’t Know
|
50 (17.1%)
|
7 (2.4%)
|
HIV status
|
|
|
0.628
|
Positive
|
12 (4.1%)
|
3 (1.0%)
|
Colour of vaginal discharge
|
|
|
0.942
|
Yellow
|
25 (8.6%)
|
7 (2.4%)
|
Brown
|
32 (11.0%)
|
8 (2.7%)
|
White
|
132 (45.2%)
|
32 (11.0%)
|
Clear
|
43 (14.7%)
|
13 (4.5%)
|
GBS Group B Streptococcus, n number of participants within group, % percentage of participants within group, Chi-square statistics was used test statistical; difference between GBS colonized and uncolonized participants
Antimicrobial susceptibility pattern
Penicillin G, ampicillin and vancomycin susceptibility pattern was tested on 58 samples while clindamycin susceptibility was tested on 46 samples. GBS bacterium isolated in this population had the highest resistance to penicillin G (72.4%, n=42/58) and ampicillin (55.2%, n=32/58). Resistance to vancomycin and clindamycin was at 24.1% (n=14/58) and 30.4% (n=14/46) respectively. In general, a slightly higher percentage of GBS isolates from the anorectal canal was resistant to tested antimicrobials in comparison to those isolated from the lower vagina. However, the difference between the two proportions was not statistically significant (Table 3).
Table 3: Difference between proportions of antimicrobial resistant GBS isolated from the lower vagina and those isolated from the anorectal canal.
Antimicrobial susceptibility
|
GBS colonization
|
P
|
Vaginal Positive
|
Anorectal Positive
|
(n, %)
|
(n, %)
|
Penicillin
|
Susceptible
|
15 (31%)
|
13 (25%)
|
0.499
|
Resistant
|
34 (69%)
|
40 (75%)
|
Ampicillins
|
Susceptible
|
24 (49%)
|
23 (43%)
|
0.544
|
Resistant
|
25 (51%)
|
30 (57%)
|
Vancomycin
|
Susceptible
|
39 (80%)
|
40 (75%)
|
0.546
|
Resistant
|
10 (20%)
|
13 (25%)
|
Clindamycin
|
Susceptible
|
28 (70%)
|
29 (69%)
|
0.922
|
Resistant
|
12 (30%)
|
13 (31%)
|
GBS Group B Streptococcus, n Number of positive GBS isolates, % percentage of isolates within group, P value obtained by comparing proportion of antimicrobial resistant isolated from anal and rectal canal
Serotypes of isolated Group B Streptococcus bacteria and their antimicrobial pattern
Out of the 60 GBS positive samples, serotype testing was conducted on 53 samples; seven samples did not grow after repeated sub-culturing. All ten known GBS serotypes occurred in this population. Serotype Ia was the most common serotype isolated from 75.9% of cultures followed by serotype III at 62.0%. Serotype IV was the least occurring serotype at 36.0%.
There was high resistance to penicillin G and ampicillin by all isolated GBS serotypes that ranged from 68% to 84% and 57% to 78% respectively. In comparison, resistance to vancomycin and clindamycin was low ranging between 16% to 26% and 15% to 33% respectively.
Serotypes IV isolates were the most resistant to penicillin G and ampicillin at 83.3% and 77.8% respectively while serotype Ia had the highest resistance to clindamycin at 33.3%; serotype VI was the most resistant to vancomycin at 25.9%. Overall, serotype IV was the most resistant to all tested antimicrobials while serotype II was the least resistance to tested antimicrobials.
Association between GBS serotype and antimicrobial susceptibility among pregnant women receiving antenatal care at Kenyatta National Hospital.
As summarized in table 4, being colonized with serotype Ia was associated with penicillin resistance (OR 4.8; CI: 1.265-18.311, p=0.021). Colonization with serotypes III (OR 6.84; CI:1.899-24.672, p=0.003), IV (OR 5.12; CI:1.372-19.077, p=0.015), VI (OR 4.45; CI:1.353-14.653, p=0.014), and VIII (OR 4.67; CI:1.255-17.358, p=0.022) was associated with ampicillin resistance. None of the isolates was associated with either vancomycin or clindamycin resistance.
Risk factors for Group B Streptococcus colonization among pregnant women receiving antenatal care at Kenyatta National Hospital.
Logistic regression was used to determine predictors of positive GBS colonization. The variables were analysed both individually and in combination to ascertain their ability to predict positive GBS colonization. None of the variables in this study was a predictor of positive GBS colonization as indicated by the greater than 0.05 p value in table 5.
Table 5: Risk factors of GBS among study participants
GBS Results
|
Odds Ratio
|
95% Conf. Interval
|
P
|
Maternal age (Years)
|
1.0
|
0.94 - 1.06
|
0.868
|
Parity
|
1.1
|
0.77 - 1.51
|
0.656
|
Parity group
|
2.3
|
0.87 - 5.99
|
0.092
|
Gestation Age
|
1.0
|
0.93 - 1.11
|
0.710
|
Gestation groups
|
0.8
|
0.45 - 1.51
|
0.528
|
Number of prior live births
|
1.1
|
0.77 - 1.51
|
0.669
|
Still births
|
0.7
|
0.46 - 1.16
|
0.187
|
History of pregnancy loss in prior pregnancies (abortion or ectopic)
|
1.3
|
0.77 - 2.20
|
0.331
|
History of preterm birth in prior pregnancy
|
1.0
|
0.64 - 1.51
|
0.948
|
Rupture of membranes for >18 hours before labour in prior pregnancy
|
0.7
|
0.30 - 1.60
|
0.396
|
Past history of neonatal death in first week of birth
|
2.1
|
0.80 - 5.60
|
0.130
|
Neonatal infection
|
0.5
|
0.15 - 1.61
|
0.238
|
Fore water break in past pregnancy/Rupture of membranes
|
1.4
|
0.23 - 8.41
|
0.725
|
GBS Group B Streptococcus, Chi-square statistics was used to obtain P value