Ipe Deepak S, Goh Kelvin G K, Desai Devika, Ben-Zakour Nouri, Sullivan Matthew J, Beatson Scott A, Ulett Glen C
School of Pharmacy and Medical Sciences, Institute for Biomedicine and Glycomics, Griffith University, Gold Coast Campus, Gold Coast, QLD 4222, Australia.
School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia.
Microbiology (Reading). 2025 Feb;171(2). doi: 10.1099/mic.0.001533.
Group B (GBS) causes various infections in adults, including urinary tract infection (UTI) and asymptomatic bacteriuria (ABU). Some bacteria that cause ABU can utilize urine as a substrate for growth, which can promote asymptomatic colonization in the host. An analysis of diverse GBS isolates associated with ABU and UTI for growth in human urine has not been undertaken. Here, we examined a large collection of clinical urinary GBS isolates from individuals with acute UTI (=62), and ABU with bacteriuria ≥10 c.f.u. ml (=206) or <10 c.f.u. ml (=90) for their ability to grow in human urine. Among all 358 GBS isolates analysed, 40 exhibited robust growth in urine in contrast to 25 that were unable to grow and non-culturable after incubation in urine. Growth phenotypes were disproportionately represented among the different groups of isolates, whereby robust growth was significantly more likely to be associated with high-grade ABU versus low-grade ABU or acute UTI (38/40 vs. 11/25; odds ratio 4.6, 95% CI, 1.5-14.8). Growth of bacteria in urine can depend on iron bioavailability, and we therefore performed growth assays using urine supplemented with 2,2-dipyridyl to chelate iron. In contrast to a control strain of ABU for which iron limitation significantly attenuated growth, iron sequestration had no significant attenuation effect on the growth of ABU GBS strain 834 in urine. Despite this finding, PCR confirmed the presence of several known growth-associated genes in GBS 834, including for iron uptake. We conclude that GBS adaptation for growth in human urine is more likely to be associated with high-grade ABU than acute UTI, and for GBS 834, this growth trait is not significantly constrained by conditions of iron sequestration.
B组链球菌（GBS）可在成人中引发多种感染，包括尿路感染（UTI）和无症状菌尿（ABU）。一些导致ABU的细菌可利用尿液作为生长底物，这会促进在宿主体内的无症状定植。尚未对与ABU和UTI相关的多种GBS分离株在人尿中的生长情况进行分析。在此，我们检测了大量来自急性UTI患者（=62例）以及菌尿≥10 c.f.u./ml（=206例）或<10 c.f.u./ml（=90例）的ABU患者的临床尿GBS分离株在人尿中的生长能力。在分析的所有358株GBS分离株中，40株在尿液中生长旺盛，相比之下，有25株在尿液中培养后无法生长且不可培养。生长表型在不同分离株组中的分布不均衡，其中旺盛生长与高级别ABU的关联显著高于低级别ABU或急性UTI（38/40对11/25；优势比4.6，95%置信区间，1.5 - 14.8）。细菌在尿液中的生长可能取决于铁的生物可利用性，因此我们使用添加了2,2 - 联吡啶以螯合铁的尿液进行生长试验。与一株ABU对照菌株不同，铁限制显著减弱了其生长，而铁螯合对尿液中ABU GBS菌株834的生长没有显著的减弱作用。尽管有这一发现，但PCR证实GBS 834中存在几个已知的与生长相关的基因，包括铁摄取相关基因。我们得出结论，GBS在人尿中生长的适应性与高级别ABU的关联更可能高于急性UTI，并且对于GBS 834而言，这种生长特性不受铁螯合条件显著限制。
