Molecular surveillance of Staphylococcus aureus and Staphylococcus saprophyticus isolates from pregnant women with asymptomatic bacteriuria in Thi-Qar province

Abstract

Asymptomatic bacteriuria (ASB) is a common condition during pregnancy, increasing the risk of maternal complications and adverse fetal outcomes. The number of pregnant women infected with Staphylococcus aureus has risen in recent years, while Staphylococcus saprophyticus is detected in up to 40% of sexually active young women as part of the normal genitourinary flora. Maternal infections during pregnancy require particular attention, as they may be vertically transmitted to the fetus, leading to unfavorable outcomes. This study aimed to investigate the prevalence and frequency of S. aureus and S. saprophyticus in pregnant women with ASB in Thi-Qar Province, considering gestational stage, maternal age, and molecular identification.

Methods. Midstream urine samples were collected from pregnant women between January 2023 and December 2024. A total of 235 samples were analyzed: 116 from pregnant women with ASB and 119 from non-pregnant women who served as controls. Diagnosis was performed using standard biochemical phenotypic tests, and molecular confirmation of S. aureus and S. saprophyticus was carried out by PCR targeting the 16S rRNA gene.

Results. Among pregnant women, the prevalence of S. aureus and S. saprophyticus was 25.0% and 60.3%, respectively, significantly higher than in the control group (5.8% and 10.0%; χ²=13.4 and 41.0; p<0.05). The frequency of isolation was 30.6% for S. aureus and 43.6% for S. saprophyticus in pregnant women, compared with 3.4% and 22.5% in controls (χ²=10.6 and 157.3; p<0.05). Gestational age influenced bacterial detection: S. aureus peaked in months II–IV (40–46.6%) but declined to 0% after the seventh month (p<0.05), while S. saprophyticus gradually increased, reaching 64.2–100% in months II–IX (χ²=120, p<0.05). Maternal age also correlated with infection rates: S. aureus was highest in women <20 years (45.3%), whereas S. saprophyticus dominated in women aged 30–39 years (68.0%) (χ²=453.7 and 1249.7; p<0.05).

Conclusions. S. aureus and S. saprophyticus are prevalent etiological agents of asymptomatic bacteriuria in pregnant women, with clear associations to gestational stage and maternal age. S. saprophyticus predominates in later months of pregnancy and among women of middle age, whereas S. aureus is more frequent in early pregnancy and younger women.