Update on Streptococcus suis Research and Prevention in the Era of Antimicrobial Restriction: 4th International Workshop on S. suis.

Streptococcus suis is a swine pathogen and a zoonotic agent afflicting people in close contact with infected pigs or pork meat. Sporadic cases of human infections have been reported worldwide. In addition, S. suis outbreaks emerged in Asia, making this bacterium a primary health concern in this part of the globe. In pigs, S. suis disease results in decreased performance and increased mortality, which have a significant economic impact on swine production worldwide. Facing the new regulations in preventive use of antimicrobials in livestock and lack of effective vaccines, control of S. suis infections is worrisome. Increasing and sharing of knowledge on this pathogen is of utmost importance. As such, the pathogenesis and epidemiology of the infection, antimicrobial resistance, progress on diagnosis, prevention, and control were among the topics discussed during the 4th International Workshop on Streptococcus suis (held in Montreal, Canada, June 2019). This review gathers together recent findings on this important pathogen from lectures performed by lead researchers from several countries including Australia, Canada, France, Germany, Japan, Spain, Thailand, The Netherlands, UK, and USA. Finally, policies and recommendations for the manufacture, quality control, and use of inactivated autogenous vaccines are addressed to advance this important field in veterinary medicine.

A campaign to eradicate bovine babesiosis from New Caledonia.

In December 2007, Babesia bovis was introduced to New Caledonia through the importation of cattle that had been vaccinated with a live tick fever (babesiosis and anaplasmosis) vaccine. Although the tick Rhipicephalus (Boophilus) microplus is common in New Caledonia, the territory had previously been free of tick-borne diseases of cattle. This paper describes the initial extent of the outbreak, the measures and rationale for disease control, and the progress to date of the eradication campaign. Initially, 22 properties were affected involving approximately 2300 cattle in 'high risk' zones and 1600 in adjoining 'suspect' zones. Rather than slaughtering infected herds or attempting to eliminate the tick vector, the campaign was based on quarantine of affected properties, and aggressive tick control in conjunction with 3-monthly treatments of the high risk cattle with the antiprotozoal drug imidocarb dipropionate. Subsequent surveillance by ELISA and PCR showed a progressive and dramatic decline in seroprevalence among infected herds and the absence of new infections. All 22 properties were considered to be free of Babesia within 12 months of the start of the disease control program. These results indicate that the strategy was effective in eliminating Babesia from infected herds and feasible as an eradication strategy on a moderately large scale. Unfortunately, early in the campaign, babesiosis spread to a herd of feral cattle on a property in the 'suspect' zone, and this reservoir of infection subsequently resulted in the infection (or reinfection) of cattle on several neighbouring commercial farms. The eradication campaign in New Caledonia is currently focussed on destocking the feral cattle - extensive surveillance suggests that this is the only remaining nidus of infection.

Indole and aminoimidazole moieties appear as key structural units in antiplasmodial molecules.

From a library of compounds of natural sources, a big series of molecules was chosen by random sampling to evaluate their in vitro antimalarial activity against Plasmodium falciparum and their antifungal activity against Candida sp. From 184 molecules tested, no molecules were active against Candida sp. (MIC>10µg/ml) whereas 13 clearly showed high antiplasmodial activity in vitro, with an IC(50) less than 1µg/ml against the chloroquine-resistant strain of P. falciparum FcM29-Cameroon. The molecules with the best antiplasmodial efficacy were 10-hydroxy-ellipticin (IC(50): 0.08µg/ml), tchibangensin (IC(50): 0.13µg/ml), ellipticin hydrochloride (IC(50): 0.17µg/ml), usambarensin (IC(50): 0.23µg/ml), 7S,3S-ochropposinine oxindole (IC(50): 0.25µg/ml), 3,14-dihydro-ellipticin (IC(50): 0.25µg/ml), tetrahydro-4',5',6'17-usambarensin 17S (IC(50): 0.26µg/ml), ellipticine (IC(50): 0.28µg/ml), aricin (IC(50): 0.3µg/ml), 10-methoxy-ellipticin (IC(50): 0.32µg/ml), aplysinopsin (IC(50): 0.43µg/ml), descarbomethoxydihydrogambirtannin (IC(50): 0.46µg/ml) and ochrolifuanin A (IC(50): 0.47µg/ml). Among these 13 promising molecules, all except descarbomethoxydihydrogambirtannin, ochrolifuanine A and usambarensine presented here novel biological activities since they had never been described in the literature for their antiplasmodial activity. In spite of the large diversity of the molecules which have been tested, it is interesting to note that the ones active against Plasmodium are all indole derivatives (and one is both indolic and aminoimidazolic). To find new antiplasmodial compounds, ethnopharmacological approaches studying traditional medicine treatments for malaria is largely used but random research produced here an interesting yield (7%) of new antiplasmodial hits and appears therefore complementary to the traditional medicine way.

Girolline: a potential lead structure for antiplasmodial drug research.

Girolline is a 2-aminoimidazole derivative extracted from Cymbastela cantharella (a New-Caledonian sponge) that has shown antitumor activity. In this study, we investigated its antimalarial activity and the point of action within the erythrocytic cycle of Plasmodium falciparum. Initially, we tested girolline and some synthetic analogues in vitro against four P. falciparum strains. The IC (50) values of girolline ranged from 77 to 215 nM, and as with artemisinin or chloroquine, girolline inhibited parasitic growth by 100 %. Girolline was found to be active at a dose of 1 mg/kg/d (orally and intraperitoneally) in vivo. Moreover, there was a significant synergistic effect between girolline and chloroquine in vitro. The investigation of the mechanism of action of girolline during the erythrocytic life cycle of the parasite showed that its action targets the synthesis of proteins by the parasite. With such a biological profile, girolline could be considered as a model chemical structure for new candidates in the arsenal of new drugs and in particular of drugs able to fight malaria.