In vitro killing of Pasteurella piscicida by fish macrophages

Abstract

The capacity of Pasteurella piscicida strains to survlve contact with macrophages obtained from rainbow trout Oncorhynchus mykiss, sea bass Dicentrarchus labrax and gilthead sea bream Sparus aurata was evaluated using an in vitro assay. Both virulent and avirulent isolates were killed by all the macrophages tested after 3 and 5 h incubation. The increased production of superoxide anion ( 0 2 -) by rainbow trout macrophages infected with P. pisclcida coinciding wlth the highest bactericidal activity (5 h incubation) suggests that the 0,-could be involved in the killing of P pjscicida. Bactericidal activity of cell-free generated 02-confirms this hypothesis, although this indicates that some other microbicidal factors must also contribute to the killing of P. pisclcida by fish macrophages.

Modulation of the innate immune responses in the striped snakehead murrel, <i>Channa striata</i> upon experimental infection with live and heat killed <i>Aeromonas hydrophila</i>

“…Vaccinating Mozambique tilapia, O. mossambicus with heat-killed A. hydrophila resulted in a strain dependent modulation of ROS production by PBL (Subramani et al, 2016a). The increased production of O2 -by rainbow trout macrophages infected with Pasteurella piscicida involved in the killing of pathogen by macrophages, since the highest level of O2 -production (after 5 h incubation) coincided with the highest bactericidal activity (Skarmeta et al, 1995). Injection of pathogenic A. hydrophila into C. striata resulted in the upregulation of tumour necrosis factor-α (TNF-α) within 24 hours which subsequently led to ROS production by phagocytic cells (Palanisamy et al, 2015).…”

Invasion of fish epithelial cells by Photobacterium damselae subsp. piscicida: evidence for receptor specificity, and effect of capsule and serum

“…As the capsule confers resistance to complement-dependent killing (Margarin4 os et al, 1996b ;Arijo et al, 1998), the intracellular environment may be more important to escape contact with phagocytes. Although some studies have indicated that P. damselae survives inside macrophages (Kubota et al, 1970 ;Nelson et al, 1981 ;Kusuda & Salati, 1993 ;Noya et al, 1995a, b), Skarmeta et al (1995) and Arijo et al (1998) found that fish macrophages have the ability to kill the bacteria, and Barnes et al (1999) have recently confirmed that P. damselae does not have adaptive defences against the bactericidal activities of macrophages. Since macrophages are able to kill P. damselae, the invasion of epithelial host cells may avoid, or at least delay, the contact between bacteria and macrophages, so contributing to the advance of disease.…”

“…Regarding the interaction of P. damselae with phagocytes, the results have been contradictory. Whilst morphologically intact bacteria within macrophages have been found in vivo (Kubota et al, 1970 ;Nelson et al, 1981 ;Kusuda & Salati, 1993 ;Noya et al, 1995a, b), suggesting that P. damselae can survive inside macrophages, in vitro studies (Skarmeta et al, 1995 ;Arijo et al, 1998) have indicated that macrophages from three different fish species were able to kill the bacteria. More recently, Barnes et al (1999) have confirmed that this species is unable to respond to oxidative attack such as that experienced during the macrophage respiratory burst.…”

Role of the capsule ofPhotobacterium damselasubsp.piscicidain protection against phagocytosis and killing by gilt-head seabream (Sparus aurata, L) macrophages

“…Nonetheless, evaluating the killing ratio demonstrated the greater susceptibility of the avirulent strain compared to virulent strains, although the di#erences between these ratios were not significant. Skarmeta et al (1995) studying the bactericidal activity of seabass, gilt-head seabream and trout macrophages against several stains of P. damsela subsp. piscicida observed that the EPOY-8803-II strain was killed with a lower e$ciency than the virulent strain DI21 by all kinds of macrophages tested, although this di#erence was only statistically significant with seabass macrophages.…”

“…The water was removed and 100 l of TSAS was added to support an overnight growth of the surviving bacteria at 18 C. After this incubation period, the number of bacteria present in the wells was determined by adding 10 l of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) (Sigma) (5 mg ml 1 distilled water), shaking the plate and reading the optical density (OD) at 550 nm min later on a multiscan spectrophotometer (Flow). The data were adjusted to yield a killing index (KI) by: (T0 MTT reduction-T 5 MTT reduction/T0 MTT reduction) 100, where the T0=bacteria at Time 0, and T 5 =bacteria at 5 h (Skarmeta et al, 1995).…”