Streptococcus equi subsp. zooepidemicus Invades and Survives in Epithelial Cells

Abstract

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) is an opportunistic pathogen of several species including humans. S. zooepidemicus is found on mucus membranes of healthy horses, but can cause acute and chronic endometritis. Recently S. zooepidemicus was found able to reside in the endometrium for prolonged periods of time. Thus, we hypothesized that an intracellular phase may be part of the S. zooepidemicus pathogenesis and investigated if S. zooepidemicus was able to invade and survive inside epithelial cells. HEp-2 and HeLa cell lines were co-cultured with two S. zooepidemicus strains (1-4a and S31A1) both originating from the uterus of mares suffering from endometritis. Cells were fixed at different time points during the 23 h infection assay and field emission scanning electron microscopy (FESEM) was used to characterize adhesion and invasion mechanisms. The FESEM images showed three morphologically different types of invasion for both bacterial strains. The main port of entry was through large invaginations in the epithelial cell membrane. Pili-like bacterial appendages were observed when the S. zooepidemicus cells were in close proximity to the epithelial cells indicating that attachment and invasion were active processes. Adherent and intracellular S. zooepidemicus, and bacteria in association with lysosomes was determined by immunofluorescence staining techniques and fluorescence microscopy. Quantification of intracellular bacteria was determined in penicillin protection assays. Both S. zooepidemicus strains investigated were able to invade epithelial cells although at different magnitudes. The immunofluorescence data showed significantly higher adhesion and invasion rates for strain 1-4a when compared to strain S31A1. S. zooepidemicus was able to survive intracellularly, but the survival rate decreased over time in the cell culture system. Phagosome-like compartments containing S. zooepidemicus at some stages fused with lysosomes to form a phagolysosome. The results indicate that an intracellular phase may be one way S. zooepidemicus survives in the host, and could in part explain how S. zooepidemicus can cause recurrent/persistent infections. Future studies should reveal the ability of S. zooepidemicus to internalize and survive in primary equine endometrial cells and during in vivo conditions.

Frecuencia de patógenos asociados a linfadenitis cervical en cuyes de centros de crianza familiar-comercial en Cusco, Perú

“…Staphylococcus spp pueden producir, además, neumonía y mastitis purulenta, así como conjuntivitis ( Dentro del mecanismo de infección de S. zooepidemicus, se sabe que la mucosa oral intacta podría ser la vía de entrada directa, favorecida por la abrasión o lesión pro-ducto de mordeduras en piel o mediante aerosoles (Murphy et al, 1991;Percy y Barthold, 2007). Recientemente se ha sugerido que dicho agente tendría una fase intracelular, lo cual podría favorecer la sobrevivencia en el hospedero y explicaría en parte las infecciones recurrentes o persistentes (Skive et al, 2017). A pesar de que los ganglios linfáticos cervicales son un lugar común de infección bacteriana y, por tanto, de formación de abscesos, otros ganglios u órganos puedes verse comprometidos (Harkness y Wagner, 1995).…”

Cases of high mortality in cull sows and feeder pigs associated withStreptococcus equisubsp.zooepidemicussepticemia

“…In vitro experiments have demonstrated the ability of S. zooepidemicus to survive within epithelial cells, which could contribute to the persistent and recurrent infection described in horses. 28 In addition, S. zooepidemicus isolates with increased capsular production have been linked with enhancement of antiphagocytic ability in experimentally infected mice and are often obtained from horses with opportunistic respiratory tract infection. 3,12 Interestingly, instability of capsular expression has been reported on primary culture of S. zooepidemicus in contrast to the robust capsular production in the closely related S. equi subsp.…”

Pathogenicity and drug resistance of animal streptococci responsible for human infections

“…This microorganism caused an epidemic of respiratory diseases among several thousand Icelandic horses in 2010 [68,83,88]. Skive et al [89] demonstrated the viability of SEZ in the endometrium, suggesting its intracellular viability.…”

“…Skive et al . [89] demonstrated the viability of SEZ in the endometrium, suggesting its intracellular viability.…”