Urinary tract infections in pregnancy : studies in vivo and in vitro

Abstract

The risk of urinary tract infection (UTI) in pregnant women is increased and predisposes them to acute pyelonephritis together with poor pregnancy outcomes. Increased frequency of micturition, nocturia and lower abdominal discomfort are common non-specific complaints during pregnancy, which render clinical diagnosis of UTI inaccurate. To prevent undesirable effects on the growing fetus, antimicrobial agents used in management of UTI during pregnancy should be carefully selected. In this thesis, we investigated virulence determinants and susceptibility of E. coli to antimicrobial agents and evaluated the possibility for medical staff - with limited training in microbiology - to evaluate easy-to-use tests for the diagnoses of UTI. The easy-to-use tests included nitrite, leucocyte esterase, urine microscopy and dipslide. Further, we evaluated the impact of vitamin D on innate immunity during pregnancy as well as the in vitro effects of Labisia pumila var. alata - a medicinal herb - on E. coli infected uroepithelial cells.

E. coli resistance to antimicrobial agents differs by region and is influenced to some extent by virulence characteristics of the bacteria. We hypothesized that antibiotic resistance and virulence characteristics of E. coli differ depending on the use of antibiotics. We report significantly higher prevalence of antibiotic resistance among isolates from Uganda and Vietnam compared to those from Sweden. Presence of the flu gene was associated with increased risk of antibiotic resistance.

The high prevalence of antibiotic resistance seen in Uganda is partly due to limited access to microbiology services. In comparison to urine culture, 96% of pregnant women diagnosed based on symptoms mimicking those of urinary tract infection freely received unnecessary antibiotics. We therefore evaluated nitrite, leucocyte esterase, leucocyturia and dipslide in outpatient settings as a way of reducing antibiotic misuse. We demonstrated high specificity, but low sensitivity of the combined nitrite and leucocyte esterase tests. There was poor correlation between leucocyte esterase and leucocyturia as analyzed by microscopy. Nurses and gynaecologist with limited knowledge of microbiology correctly diagnosed E. coli with a simplified culture method – the dipslide test.

During pregnancy, vitamin D is required for development of the fetal skeleton, but it is also important for innate immunity. The major source of vitamin D is sunlight. Although Uganda has high sun exposure the whole year, persons with dark pigmented skin may not be able to optimally synthesize vitamin D. We found vitamin D as well as the antimicrobial peptide LL- 37 - that is induced by vitamin D, increased with advancing gestational age. There were significantly higher levels in the third compared to the first trimester. Furthermore, serum had increased bactericidal activity with increasing vitamin D levels. Conversely, IL-8 decreased with advancing gestational age. In vitro, vitamin D decreased expression of IL-8 in a dosedependent manner potentially modifying the inflammatory response to infection.

The breakaway resistance to antibiotics recommended in management of UTI calls for alternative intervention that could be used alone or in combination with antibiotic therapy. The mechanisms of action of many medicinal herbs with potential disease-modifying effects have not been elucidated. We evaluated the medicinal herb Labisia pumila var. alata (LPva) – a herb whose effects on female genital conditions are widely reported but whose mode of action in UTI is not properly understood. LPva was not bactericidal but prevented bacterial invasion by down regulating β1 integrin and it also induced apoptosis in a dose-dependent manner.

In conclusion, management of UTI in pregnancy will be improved by using effective antibiotics coupled with improved diagnostics. More vigorous interrogation of medicinal herbs hold promise for alternative therapies. We demonstrate for the first time the variation of LL-37 during pregnancy; given impaired vitamin D synthesis among dark-skinned persons, fortification of food especially for pregnant women needs to be considered.