Modern molecular technologies have revolutionized our understanding of bacterial epidemiology, but reported data across studies and different geographic endemic settings remain under-integrated in common theoretical frameworks. Pneumococcus serotype co-colonization, caused by the polymorphic bacteria , has been increasingly investigated and reported in recent years. While the global genomic diversity and serotype distribution of have been well-characterized, there is limited information on how co-colonization patterns vary globally, critical for understanding the evolution and transmission dynamics of the bacteria. Gathering a rich dataset of cross-sectional pneumococcal colonization studies in the literature, we quantified patterns of transmission intensity and co-colonization prevalence variation in children populations across 17 geographic locations. Linking these data to an SIS model with cocolonization under the assumption of quasi-neutrality among multiple interacting strains, our analysis reveals strong patterns of negative co-variation between transmission intensity () and susceptibility to co-colonization (). In line with expectations from the stress-gradient-hypothesis in ecology (SGH), pneumococcus serotypes appear to compete more in co-colonization in high-transmission settings and compete less in low-transmission settings, a trade-off which ultimately leads to a conserved ratio of single to co-colonization . From the mathematical model’s behavior, such conservation suggests preservation of ‘stability-diversity-complexity’ regimes in coexistence of similar co-colonizing strains. We find no major differences in serotype compositions across studies, pointing to adaptation of the same set of serotypes across variable environments as an explanation for their differential interaction in different transmission settings. Our work highlights that the understanding of transmission patterns of from global scale epidemiological data can benefit from simple analytical approaches that account for quasi-neutrality among strains, co-colonization, as well as variable environmental adaptation.

中文翻译：

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肺炎球菌和压力梯度假说：权衡联系[公式省略]和各国共同定植的易感性

现代分子技术彻底改变了我们对细菌流行病学的理解，但跨研究和不同地理流行环境报告的数据在共同的理论框架中仍然没有得到充分整合。近年来，由多态性细菌引起的肺炎球菌血清型共定植现象得到越来越多的研究和报道。虽然全球基因组多样性和血清型分布已得到充分表征，但关于全球共定殖模式如何变化的信息有限，这对于了解细菌的进化和传播动力学至关重要。我们收集了文献中丰富的横断面肺炎球菌定植研究数据集，量化了 17 个地理位置儿童群体的传播强度模式和共定植流行率变化。在多个相互作用菌株之间准中性的假设下，将这些数据与共定植的 SIS 模型联系起来，我们的分析揭示了传输强度 () 和共定植敏感性 () 之间强烈的负共变模式。根据生态学压力梯度假说 (SGH) 的预期，肺炎球菌血清型似乎在高传播环境中的共定殖中竞争更多，而在低传播环境中竞争较少，这种权衡最终导致单一定植与共定植的保守比率。从数学模型的行为来看，这种保守性表明在相似的共殖民菌株共存时保留了“稳定性-多样性-复杂性”机制。我们发现不同研究之间的血清型组成没有重大差异，这表明同一组血清型在不同环境中的适应可以解释它们在不同传播环境中的差异相互作用。我们的工作强调，从全球范围内的流行病学数据中了解传播模式可以受益于简单的分析方法，这些方法解释了菌株之间的准中性、共同定植以及可变的环境适应。