Summary
Objective
Symptomatic bacteriuria is common in pregnant women and if untreated could lead to serious complications. Although asymptomatic bacteriuria could also lead to such complications, this fact is not so well known. This study was to determine the prevalence of asymptomatic bacteriuria in pregnant women attending antenatal clinic at the Komfo Anokye Teaching Hospital (KATH) Kumasi.
Design
A prospective study to screen antenatal attendants for asymptomatic bacteriuria.
Setting
The study was undertaken at KATH.
Participants
All pregnant women attending antenatal clinic at KATH, Kumasi between February and April 2003 and who agreed to enter the study were clinically evaluated to exclude signs and symptoms of urinary tract infection (UTI).
Methods
Samples of 10–15ml urine were examined for pus cells, bacteria and parasitic ova. The samples were further cultured on cysteine lactose electrolyte deficient agar and colony counts yielding bacterial growth of 105/ml or more of pure isolates were deemed significant.
Results
Of the 220 pregnant women, 16 had significant bacteriuria giving a prevalence rate of 7.3%. The highest age-specific prevalence was found in the 35–39 year-olds (13%) and the lowest in the 15–19 year-olds (0.0%). There was no significant difference in prevalence with increasing parity. The dominant bacteria isolates were E. coli (37%) and Staph aureus (31%).
Conclusion
The prevalence of asymptomatic bacteriuria in pregnant women at KATH is 7.3%. The predominant organisms are E.coli and Staph aureus, and most isolates are sensitive to nitrofurantoin, cefuroxime and gentamicin.
Keywords: Urinary Tract Infection, antenatal, asymptomatic bacteriuria, pregnant women
Introduction
Urinary Tract Infection (UTI) refers to both microbial colonization of the urine and tissue invasion of any structure of the urinary tract1. Bacteria are most commonly responsible although yeast and viruses may also be involved. Asymptomatic bacteriuria, in which urine culture reveals a significant growth of pathogens, that is greater than 105 bacteria/ml,2 but without the patient showing symptoms of UTI, can be found in both pregnant and non pregnant women. Pregnancy enhances the progression from asymptomatic to symptomatic bacteriuria which could lead to pyelonephritis and adverse obstetric outcomes such as prematurity, low-birth weight3, and higher fetal mortality rates4,5. Although UTI may not always lead to complications in the mother, it is still a cause of significant morbidity6.
In Nigeria, Olusanya et al in Sagamu reported a prevalence rate of 23.9% in 19937. Akerele et al also reported 86.6% in Benin City in 20018. A prevalence rate of 7% in pregnant women has been reported in Ethiopia9. In Canada the prevalence rate varies from 4–7%. The prevalence is higher among individuals in lower socioeconomic classes and those with a past history of asymptomatic urinary tract infection4. Other reports have noted that asymptomatic bacteriuria occurs in 5 to 9% of both non-pregnant and pregnant women and that if left untreated in pregnancy progression to symptomatic UTI including acute cystitis and pyelonephritis occurs in 15 to 45%, or 4-fold higher than in non-pregnant women10.
Some studies3,5 have postulated that since asymptomatic bacteriuria, usually caused by aerobic gram-negative bacilli or Staphylococcus haemolyticus can lead to UTI, a urine culture should be obtained from all women early in pregnancy, even in the absence of UTI symptoms. Bacteriuria should be treated with a 3–7 day course of antimicrobials, which reduces the risk of symptomatic UTI by 80 to 90%3, 5.
The association between bacteriuria and pyuria has been reported11,12. While some workers have observed a positive correlation between pyuria and significant bacteriuria11, others have found little or no correlation12.
This study was therefore undertaken to determine the prevalence of asymptomatic bacteriuria in pregnant women attending antenatal clinic at KATH to identify the organisms involved, determine their relative proportions and their antibiotic sensitivities.
Subjects and Methods
The study was undertaken at the Department of Obstetrics and Gynaecology and the Microbiology Laboratory of the Kwame Nkrumah University of Science & Technology School of Medical Sciences (KNUST SMS), and the Komfo Anokye Teaching Hospital (KATH) Kumasi, Ghana between 1st February and 30th April 2003. It was approved by the KNUST SMS Ethical Committee.
All pregnant women attending antenatal clinic at KATH, Kumasi between February and April 2003 and who agreed to enter the study were clinically evaluated to exclude signs and symptoms of UTI. With the aid of a questionnaire, demographic features including age, parity, and gestational age of pregnancy were collected. After being instructed on the correct mode of self collection of urine sample and the importance of a clean catch of urine, they were provided with sterile universal bottles.
Samples of 10–15ml urine were obtained and placed in a cold box. It was microscopically examined for pus cells, bacteria and ova, and then cultured within two hours. Urine samples that were not cultured within two hours were stored at 4°C.
Samples were cultured on dried plates of Cysteine lactose electrolyte deficient agar (CLED), using a calibrated loop delivering 0.002 ml of urine. Plates were incubated aerobically at 37°C overnight. Colony counts yielding bacterial growth of 105/ml or more of pure isolates were deemed significant. Isolates were identified to species level using standard methods and their antimicrobial sensitivities were done using Kirby Bauer disc diffusion technique13. Urine samples producing non-significant and mixed growths did not have the test repeated.
Results
Out of 220 women examined for asymptomatic bacteriuria, 16 were positive for significant bacteriuria, giving a prevalence of 7.3% among the pregnant women. Table 1 shows the age distribution and Table 2 the parity distribution among the women studied. The highest rate of 13% was found in the age group 35–39 years and the lowest rate of 0% in the age groups 15–19 years and 45–49 years. Women with parity 4 or more had the highest prevalence of 16.1% whilst nulliparous women had the least prevalence of 3.7%. Chi-square test of association between parity and significant bacteriuria showed no significant difference. (chi-square 0.05,3 = 5.0976 as against critical value of 7.81).
Table 1.
Age distribution among pregnant women showing significant bacteriuria at KATH
| Age Group |
Total Number |
No. with Significant Bacteriuria |
Age Specific prevalence (%) |
| 15–19 | 8 | 0 | 0 |
| 20–24 | 25 | 2 | 8.0 |
| 25–29 | 85 | 7 | 8.2 |
| 30–34 | 68 | 3 | 4.4 |
| 35–39 | 23 | 3 | 13.0 |
| 40–44 | 9 | 1 | 11.1 |
| 45–49 | 2 | 0 | 0 |
| Total | 220 | 16 | 7.3 |
Table 2.
Parity distribution among pregnant women showing significant bacteriuria KATH
| Parity | No. of women with significant bacteriuria (% in parity group) |
No. of women with no significant bacteriuria (% in parity group) |
Total | |
| 0 | 2 (3.7) | 52 (96.3) | 54 (100) | |
| 1–3 | 9 (6.7) | 126 (93.3) | 135 (100) | |
| ≥ 4 | 5 (16.1) | 26 (83.9) | 31 (100) | |
| Total | 16 (7.3) | 204 (92.7) | 220 (100) |
X2 = 4.70, p = 0.095
The bacterial isolates are shown in Table 3. The dominant bacteria were E.coli (37%) and Staph aureus (31%). The other isolates were Klebsiella, Providencia species, other coliforms, Staphylococcus saprophyticus and Enterococcus faecalis.
Table 3.
Bacterial isolates among pregnant women with significant bacteriuria at KATH
| Bacterial Isolate | Number of women with isolates# |
| Escherichia coli | 6 (37.5) |
| Staphylococcus aureus | 5 (31.25) |
| Providencia species | 1 (6.25) |
| Other Coliform | 1 (6. 25) |
| Klebsiella species | 1 (6.25) |
| Staphylococcus saprophyticus | 1 (6.25) |
| Enterococcus faecalis | 1 (6.25) |
| Total Isolates | 16 (100) |
% of total number with asymptomatic bacteria
All the E.coli isolates were sensitive to nitrofurantoin, gentamicin, cefuroxime and nalidixic acid; only two were sensitive to ampicillin and cotrimoxazole. The five isolates of Staph aureus were sensitive to nitrofurantoin and ampicillin, four were sensitive to cefuroxime and three to gentamicin and cotrimoxazole. All were resistant to nalidixic acid. All except one (Enterococcus faecalis) of the sixteen isolates were sensitive to nitro-furantoin; thirteen were sensitive to cefuroxime and gentamicin, nine to ampicillin, and eight to nalidixic acid and cotrimoxazole.
Ten (10) out of 16 women with asymptomatic bacteriuria were in the first trimester, 4 in the second trimester and the remaining 2 in the third trimester.
Fifty percent (50%) of the pregnant women with significant bacteriuria also had significant pyuria (or pus cells of more than 10 per high power field). Among the study subjects 19.6% had significant pyuria without significant bacteriuria.
Discussion
The study found sixteen significant bacteriuria among 220 pregnant women at KATH, giving a prevalence rate of 7.3%. Rates of 4–7% have been reported from Canada4 and 7% in Ethiopia9. Nicolle stated that the prevalence rate will be higher among individuals with lower socioeconomic status4. The highest prevalence of 13% was recorded in the age-group 35–39 years and the lowest rate of 0.0% among the 15–19 age-group. In relation to parity, women with 4 or more children had a prevalence of 16.1% as against 3.7% in the nulliparous women.
The dominant organisms were E.coli (37.5%) and Staphylococcus aureus (31.25%). This is similar to the findings in previous studies by Cheesbrough14 and Delzel15. This could be due to the fact that urinary stasis is common in pregnancy and since most E. coli strains prefer that environment, they cause UTI15. The other organisms isolated included Staphylococcus saprophyticus, Klebsiella species, Providencia species, Enterococcus faecalis and an unidentified coliform. They are less common organisms causing UTI14.
This study has found that nitrofurantoin, cefuroxime and gentamicin were very effective against most of the urinary isolates. All gram negative organisms were susceptible to nalidixic acid with the exception of the unidentified coliform isolated. The prevalence of resistance of urinary isolates to nitrofurantoin and gentamicin was 0% to 2%16. Gupta et al stated that nitrofurantoin is relatively safe in pregnancy and is effective against most UTI, but may cause haemolysis in a glucose-6-phosphate dehydrogenase deficient infant if used close to term16. Although gentamicin is also effective in treating asymptomatic bacteriuria in pregnant women, it is known to be nephrotoxic15. Gentamicin should therefore be used when absolutely necessary17. All the E.coli isolated were 100% susceptible to both nitrofurantoin and gentamicin.
In this study, it was observed that pregnant women with four or more children had the highest percentage of asymptomatic significant bacteriuria. It was also noted that most of the infected subjects were in their first and early second trimesters. This could be because most pregnant women report at the antenatal clinic for booking during these periods. Nicolle4 stated that the gold standard in screening for asymptomatic bacteriuria is urine culture in early pregnancy of 12 to 16 weeks gestation. Indeed, the first trimester urine culture remains the screening test of choice3.
In conclusion, the prevalence of asymptomatic bacteriuria in pregnant women at Komfo Anokye Teaching Hospital is 7.3%. The predominant organisms are E.coli and Staph aureus, and most isolates are sensitive to nitrofurantoin, cefuroxime and gentamicin.
Acknowledgement
We thank the nursing staff of the Antenatal Clinic at KATH for their help in patient recruitment, and the staff of the Microbiology Laboratory for their help in specimen processing.
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