PUCRS, Escola de Ciências, Laboratório de Imunologia e Microbiologia, Porto Alegre, RS, Brazil.
PUCRS, Escola de Ciências, Programa de Pós-graduação em Ecologia e Evolução da Biodiversidade, Porto Alegre, RS, Brazil.
Sci Rep. 2019 May 10;9(1):7232. doi: 10.1038/s41598-019-43631-7.
Persistence phenotype and small colony variants (SCVs) can be part of a bacterial bet-hedging strategy for survival under environmental stresses, such as antimicrobial exposure. These phenotypes are of particular concern in persistent and relapsing infections, since cells resume to normal growth after cessation of the stressful condition. In this context, we found persisters and unstable SCVs as phenotypic variants of Salmonella enterica that were able to survive ciprofloxacin exposure. A high heterogeneity in persister levels was observed among S. enterica isolates grown under planktonic and biofilm conditions and exposed to ciprofloxacin or ceftazidime, which may indicate persistence as a non-multidrug-tolerant phenotype. Nevertheless, a comparable variability was not found in the formation of SCVs among the isolates. Indeed, similar proportions of SCV in relation to normal colony phenotype (NCP) were maintained even after three successive cycles of ciprofloxacin exposure testing colonies from both origins (SCV or NCP). Additionally, we found filamentous and dividing cells in the same scanning electron microscopy images from both SCV and NCP. These findings lead us to hypothesize that besides variability among isolates, a single isolate may generate distinct populations of persisters, where cells growing under distinct conditions may adopt different and perhaps complementary survival strategies.
持久性表型和小菌落变异体（SCVs）可能是细菌在环境压力下（如抗菌药物暴露）生存的一种赌注回避策略的一部分。这些表型在持续性和复发性感染中尤为令人关注，因为在应激条件停止后，细胞会恢复正常生长。在这方面，我们发现沙门氏菌中的持久性和不稳定 SCVs 是能够在环丙沙星暴露下存活的表型变异体。在浮游和生物膜条件下生长并暴露于环丙沙星或头孢他啶的沙门氏菌分离株中，观察到持久性水平存在高度异质性，这可能表明持久性是一种非多药耐受表型。然而，在 SCV 的形成中，分离株之间并没有发现类似的可变性。事实上，即使在对来自两个来源（SCV 或 NCP）的菌落进行三轮连续的环丙沙星暴露测试后，SCV 与正常菌落表型（NCP）的比例仍保持相似。此外，我们在来自 SCV 和 NCP 的相同扫描电子显微镜图像中发现了丝状和分裂细胞。这些发现使我们假设，除了分离株之间的可变性外，单个分离株可能会产生不同的持久性细胞群体，在不同条件下生长的细胞可能会采用不同的、也许是互补的生存策略。
