Invasiveness of Salmonella typhimurium in HEp-2 cell cultures preinfected with Coxsackie B 1 virus

Kingella kingae and Viral Infections

Kingella kingae (K. kingae) is an oropharyngeal commensal agent of toddlers and the primary cause of osteoarticular infections in 6–23-month-old children. Knowing that the oropharynx of young children is the reservoir and the portal of entry of K. kingae, these results suggested that a viral infection may promote K. kingae infection. In this narrative review, we report the current knowledge of the concomitance between K. kingae and viral infections. This hypothesis was first suggested because some authors described that symptoms of viral infections were frequently concomitant with K. kingae infection. Second, specific viral syndromes, such as hand, foot and mouth disease or stomatitis, have been described in children experiencing a K. kingae infection. Moreover, some clusters of K. kingae infection occurring in daycare centers were preceded by viral outbreaks. Third, the major viruses identified in patients during K. kingae infection were human rhinovirus or coxsackievirus, which both belong to the Picornaviridae family and are known to facilitate bacterial infections. Finally, a temporal association was observed between human rhinovirus circulation and K. kingae infection. Although highly probable, the role of viral infection in the K. kingae pathophysiology remains unclear and is based on case description or temporal association. Molecular studies are needed.

Coxsackie B1 virus-induced changes in cell membrane-associated functions are not responsible for altered sensitivity to bacterial invasiveness

To analyze the possible mechanisms by which coxsackie B1 virus infection affects the invasiveness of Shigella flexneri, we have studied the influence of intracellular levels of Na+ and K+, ATPase activity, cytoplasmic membrane potential, cAMP level and cell communication through gap junctions. 3h after adsorption of viable or UV-inactivated coxsackie B1 virus the Na(+)-K+ gradient of the cell collapsed, ATPase activity decreased, the cytoplasmic membranic potential-dependent tetraphosphonium ion uptake were reduced. No changes in cAMP or intercellular cell communication were observed. S. flexneri invasiveness in HEp-2 cell pretreated with viable or UV-inactivated coxsackie B 1 virus was enhanced, but bacterial invasiveness was unchanged in K(+)-depleted HEp-2 cells, cell cultures with high intracellular Na+ content or ouabain pre-treated cells compared to control cells. We found no correlation between the enhanced bacterial invasiveness in the early phase of coxsackie B 1 virus infection in HEp-2 cell cultures and intracellular K+ depletion, high intracellular Na+ content, inhibited Na(+)-K+ ATPase activity or membranic depolarization.

Effect of enteroviruses on adherence to and invasion of HEp-2 cells by Campylobacter isolates

Coinfection of HEp-2 epithelial cells with coxsackievirus B3, echovirus 7, poliovirus (LSc type 1), porcine enterovirus, and Campylobacter isolates was performed to determine if a synergistic effect could be obtained. The invasiveness of Campylobacter jejuni ATCC 33560 was significantly increased for HEp-2 cells preinfected with echovirus 7, coxsackievirus B3, and UV-inactivated (noninfectious) coxsackievirus B3 particles. Additionally, the invasiveness of C. jejuni M96, a clinical isolate, was significantly increased for HEp-2 cells preinfected with coxsackievirus B3. Poliovirus and porcine enterovirus had no effect on C. jejuni ATCC 33560 adherence and invasiveness. Furthermore, poliovirus had no effect on the ability of C. jejuni M96 to adhere to and invade HEp-2 cells. Campylobacter hyointestinalis and Campylobacter mucosalis, two noninvasive isolates, did not invade virus-infected HEp-2 cells. The increase in the invasiveness of C. jejuni appeared to be the result of specific interactions between the virus and the HEp-2 cell membrane. The data suggest that the invasiveness of Campylobacter spp. is dependent upon the inherent properties of the organism. Virus-induced cell alterations can potentiate the invasiveness of virulent Campylobacter spp. but are not sufficient to allow internalization of noninvasive bacteria.

Expression of Campylobacter jejuni invasiveness in cell cultures coinfected with other bacteria

Enteroinvasive Salmonella, Shigella, and Escherichia coli strains were found to exert an effect which rendered Campylobacter jejuni capable of intracellular localization in epithelial cells in vitro. When monolayers of HEp-2 or A-549 cells were challenged with pure cultures of C. jejuni or Campylobacter coli, none of the eight strains tested invaded the cells. In contrast, four of these strains were able to localize intracellularly when the cells were challenged with a mixture of campylobacters and enteroinvasive Salmonella typhimurium, Shigella flexneri, Shigella boydii, Shigella sonnei, or E. coli strains. Invasiveness of campylobacters was also induced by one nonenteroinvasive strain of E. coli O124. Coinfection with other nonenteroinvasive E. coli strains did not induce invasiveness in C. jejuni. The degree of internalization induced by S. typhimurium was significantly higher than that induced by Shigella or E. coli strains. The invasive capacity of C. jejuni was found to differ considerably between strains. No evidence of an invasive potential was demonstrable for two C. coli strains or for two enterotoxigenic isolates of C. jejuni examined. C. jejuni was only able to localize intracellularly in cell cultures when the interaction occurred in a microaerobic atmosphere. None of the strains tested evoked keratoconjunctivitis in guinea pig eyes (Sereny test), regardless of the presence of coinfectants. The results indicate that a synergistic interaction that exists between C. jejuni and other enteropathogens facilitates invasion by C. jejuni.