Urinary tract infections in pregnancy in a rural population of Bangladesh: population-based prevalence, risk factors, etiology, and antibiotic resistance

The data reported in this manuscript were part of a population-based cluster randomized controlled trial (cRCT) to determine the impact of an antenatal screening program for abnormal vaginal flora and UTI on the incidence of preterm live birth (clinicaltrials.gov identifier: NCT01572532) [14, 15]. The study protocol was approved by the institutional review boards of Johns Hopkins Bloomberg School of Public Health Institutional Review Board (Baltimore, Maryland), International Centre for Diarrhoeal Disease Research, Bangladesh Ethical Review Committee (iccdr,b) (Dhaka, Bangladesh), and Partners Human Research Committee (Boston, MA). The Maternal Infection Screening and Treatment (MIST) study [17] was conducted between January 2, 2012 and July 28, 2015 in two rural sub-districts of Sylhet district, Bangladesh: Zakiganj and Khanaighat, which are part of the Projahnmo research site. The study site is in a rural, agrarian area, with poor access to health care and high need, having one of the highest neonatal mortality rates in Bangladesh. Health services in Bangladesh are provided by the government’s Ministry of Health and Family Welfare, NGOs, and private providers. According to the 2014 Bangladesh Demographic and Health Survey, 79% of pregnant women had at least one ANC visit and 31% received at least four ANC visits [19]. Screening for urinary tract infection in pregnancy by urine culture is not standard of care in Bangladesh.

A cluster was defined as the area served by a community health worker (CHW), comprising several contiguous villages (population~ 4000 people, approximately 120 annual pregnancies, per cluster). In MIST, there were 24 clusters, for which community health workers conducted home visits to provide basic antenatal and post-partum care and education. In the cRCT, 12 clusters were randomized to receive the intervention, which included home-based screening and treatment of UTI and abnormal vaginal flora (AVF). In this manuscript, we report the results of the UTI screening. Results of the AVF intervention are reported elsewhere [20].

All married women of reproductive age in the study areas were under routine monthly community-based pregnancy surveillance through the duration of the study. Pregnant women who had no or uncertain recall of their last menstrual period (LMP), LMP > 19 weeks, self-reported history of irregular bleeding due to injectable depoprovera, or self-reported history of severe chronic disease were excluded. Participants were enrolled after providing verbal informed consent. Verbal consent was obtained because the majority of the prospective study population was illiterate at the initiation of the study. Documentation of verbal informed consent was formally approved by all institutional review boards.

For pregnant women in intervention clusters, during a home visit at < 19 weeks gestation, a clean catch midstream urine specimen was collected for culture. The CHW instructed the mother to spread the labia widely before collecting 20-30 mL of the midstream urine into a sterile wide-mouthed container. The urine specimen was immediately placed in a cooler refrigerated with ice-packs (~ 2 to 8 °C) and transported to the Sylhet field laboratory, maintaining the cold chain. A random selection of 10% of the control arm women also had urine screened by culture.

Urine specimens were inoculated on standard MacConkey and Blood agar plates within 6 h of collection and incubated at 37 °C for 48 h. Bacterial growth was quantified twice (24 and 48 h). Bacterial isolates were speciated using standard microbial techniques. Antibiotic susceptibility testing was performed on Mueller-Hinton agar plates following standard laboratory protocols. The disk diffusion method was used; zones of growth inhibition were measured in mm [21]. The antimicrobial discs used were: cefixime, nitrofurantoin, ampicillin, azithromycin, cotrimoxazole, gentamycin, nalidixic acid, ceftriaxone, and cephalexin.

We defined categories of urinary tract infection shown in Table 1. The list of organisms that we considered as UTI pathogens versus contaminants is shown in Additional file 1: Table S1.

The MIST treatment algorithm for positive urine cultures is shown in Additional file 1: Figure S1. UTI was treated in pregnant women with high burden growth (> 10⁵ CFU/mL of a uro-pathogen), as well as among women with intermediate growth who had UTI symptoms, as per ACOG recommendations [22]. From January to October 2012, the first line antibiotic treatment was cefixime 400 mg po once daily for 3 days. After observing that only two-thirds of E. coli were susceptible to cefixime, the first-line treatment was then changed to nitrofurantoin (Macrobid) 100 mg po bid for 7 days. All symptomatic women were also referred to the sub-district hospital for further evaluation and management.

A test of cure was obtained 1 week after antibiotic completion for all pregnant women with positive cultures. If the second urine culture remained positive, the supervising field physician prescribed an antibiotic based on the antimicrobial sensitivity pattern. Persistent UTI after twice-repeated treatment was referred to Sylhet Osmani Medical College Hospital for further evaluation and management.

Simple descriptive statistics were used to describe the distribution of uro-pathogens and antibiotic sensitivity patterns.

For the risk factor analysis, the primary outcome was UTI requiring antibiotic treatment, as defined in Table 1. We included a number of socio-demographic characteristics, nutrition, behavior, and reproductive history variables as potential risk factors. Socio-demographic characteristics included household wealth, household size, religion, woman’s age at enrollment, parity, and educational attainment of both the woman and her husband. All variables were categorized. A wealth index indicative of relative economic status of the household within the study population was constructed using household facilities and assets weighted with principal component analysis [23]; the households were categorized into quintiles. Comparisons of proportions between groups were analyzed by chi-squared statistic.

In the initial screening of urine samples from the general pregnancy population (n = 4034), 230 (5.7%) women had high burden (> 100,000 CFU/mL) bacteriuria, among which 47 (20.4%) reported clinical signs of UTI, and 183 (79.6%) had no symptoms (Table 2). An additional 599 (14.9%) women in the initial screening had intermediate level (> 1000- < 100,000 CFU/mL) bacteriuria, with 130 (21.7%) of those women reporting UTI symptoms, which were treated with antibiotics. Overall, 360 (8.9%) of women required treatment for UTI, of whom 308 (86%) were started on antibiotics and 284 (92%) completed the full course.

Among women with positive screening urine cultures, we successfully obtained a test of cure specimen in 276/360 women. Among these mothers, 56/276 (20.3%) had a persistent UTI on the second urine culture that required a second course of antibiotics, that was selected based on antimicrobial resistance patterns. Among these women, we obtained a final test of cure specimen from 42 women with persistent UTI. The prevalence of persistent UTI among those women was 26.2% on the final screening.

Table 3 shows the analysis of risk factors for UTI in this population. In bivariate analysis, low household wealth, primiparity, and maternal undernutrition as measured by MUAC were associated with increased risk of UTI. Higher education of the women and their husbands were protective for UTI. In multivariate analysis (Table 4), low MUAC, low paternal education, and primiparity remained statistically significant risk factors for UTI.

Figure 2 shows the bacterial etiology of UTI pathogens among pregnant mothers who were treated (high burden and intermediate growth in symptomatic mothers; n = 360) in the initial screening of the general pregnancy population in Sylhet, Bangladesh. The predominant micro-organisms were E. coli (n = 135; 38% of isolates) and Staphylococcus species (non-aureus) (n = 82; 23%), followed by Klebsiella species (n = 44, 12%). Staphylococcus aureus was common, isolated in 42 (12%) women with UTI. The prevalence of Group B Streptococcus (GBS) bacteriuria was generally lower, with 19 isolates (n = 19; 5.3%).

Among the intermediate growth in mothers who were asymptomatic, there was a predominance of skin contaminants, including staph and strep species, and these are shown in the Additional file 1: Figure S2.

Table 5 shows the antimicrobial susceptibility patterns of uro-pathogens in the MIST study. E. coli isolates had low rates of susceptibility to ampicillin (34% of isolates) and azithromycin (28%); susceptibility to cefixime, cotrimoxazole, and cephalexin were in the moderate range (69, 63, and 62% respectively). The majority of species were highly susceptible to nitrofurantoin, with the exception of Klebsiella species, where 74% of strains were susceptible. Rates of susceptibility to azithromycin were low among the gram-negative species.