A Brucella melitensis H38ΔwbkF rough mutant protects against Brucella ovis in rams.

Brucella melitensis and Brucella ovis are gram-negative pathogens of sheep that cause severe economic losses and, although B. ovis is non-zoonotic, B. melitensis is the main cause of human brucellosis. B. melitensis carries a smooth (S) lipopolysaccharide (LPS) with an N-formyl-perosamine O-polysaccharide (O-PS) that is absent in the rough LPS of B. ovis. Their control and eradication require vaccination, but B. melitensis Rev 1, the only vaccine available, triggers anti-O-PS antibodies that interfere in the S-brucellae serodiagnosis. Since eradication and serological surveillance of the zoonotic species are priorities, Rev 1 is banned once B. melitensis is eradicated or where it never existed, hampering B. ovis control and eradication. To develop a B. ovis specific vaccine, we investigated three Brucella live vaccine candidates lacking N-formyl-perosamine O-PS: Bov::CAΔwadB (CO2-independent B. ovis with truncated LPS core oligosaccharide); Rev1::wbdRΔwbkC (carrying N-acetylated O-PS); and H38ΔwbkF (B. melitensis rough mutant with intact LPS core). After confirming their attenuation and protection against B. ovis in mice, were tested in rams for efficacy. H38ΔwbkF yielded similar protection to Rev 1 against B. ovis but Bov::CAΔwadB and Rev1::wbdRΔwbkC conferred no or poor protection, respectively. All H38ΔwbkF vaccinated rams developed a protracted antibody response in ELISA and immunoprecipitation B. ovis diagnostic tests. In contrast, all remained negative in Rose Bengal and complement fixation tests used routinely for B. melitensis diagnosis, though some became positive in S-LPS ELISA owing to LPS core epitope reactivity. Thus, H38ΔwbkF is an interesting candidate for the immunoprophylaxis of B. ovis in B. melitensis-free areas.

Weaned piglets: another factor to be considered for the control of Salmonella infection in breeding pig farms.

Field studies on Salmonella infection in suckling piglets are scarce due to the intrinsic difficulties of collecting proper samples (i.e. tonsils or mesenteric lymph nodes), and most of them rely on the analysis of rectal swabs that limit their accuracy. We used 495 slaughtered 4-weeks-old male piglets intended for human consumption from 5 Salmonella-seropositive breeding farms to collect gastrointestinal packages and perform a thorough detection of Salmonella on mesenteric lymph nodes and intestinal content. The overall prevalence of both infection and shedding was high (≈ 36%) indicating that piglets played an active role in Salmonella maintenance in the farms. Major serotypes found in piglets included 4,[5],12:i: (35.4%), Rissen (17.1%), Derby (10.9%) and Bovismorbificans (10.3%). In most of the infected animals (72.8%) the same serotype was found in mesenteric lymph nodes and feces. Significant higher ELISA OD% values were found in meat juice samples from non-infected piglets compared to infected ones (median OD% of 12.0 and 17.3, respectively; P = 0.002) suggesting some protective effect of sow's colostrum. Salmonella was also isolated from feces from weaned sows contemporary of the slaughtered piglets, and 89% of the serotypes identified in sows were also detected in piglets. Pulsed field gel electrophoresis analyses showed that 75% of the piglet isolates that were compared to those of sows were related to them, suggesting the circulation of Salmonella strains between sows and piglets. It appears that improving piglet colostrum intake along with the reduction of the shedding in sows may favor the control of Salmonella infection in breeding farms.

Role of wild bird and rodents in the epidemiology of subclinical salmonellosis in finishing pigs.

Wild birds and rodents may play an important role in the dynamics of subclinical pig salmonellosis, either as the introducers of the bacteria into the farm or as receptors of an infection already established in the farm. We tried to gain further insight into the epidemiology of this infection by studying the phenotypic (i.e., serotype and antimicrobial resistance patterns) and molecular characteristics of Salmonella strains isolated from samples collected from pigs and wildlife captured in the vicinity of pig farms. Salmonella-positive pig fecal samples were identified in 56.1% of the 41 farms investigated. Birds shedding Salmonella spp. were detected in 21.4% of the farms despite the low numbers of birds captured in many farms. Most Salmonella isolates from birds (74%) did not show any antimicrobial resistance (AR) pattern and belonged to phage types rarely seen in the pig population (U310, DT56, DT137, DT164), supporting the likely avian source of infection for most birds. The proportion of farms showing Salmonella-infected rodents was higher (46.2%), with Salmonella isolates showing a high homology with those likely originated from pigs. Salmonella-positive environmental samples were found in >50% of the farms, and the characteristics of these Salmonella strains supported the idea of pigs as a major source of Salmonella contamination of the farm environment. Dissemination of Salmonella in pig farms from areas of high Salmonella prevalence appeared to depend to some extent upon rodents and wild birds present in the farm, but the role of rodents in its maintenance seemed to be somewhat more relevant than that of birds. In conclusion, activities aimed at reducing the contact of these wild species with pigs will probably assist in the control of pig salmonellosis. Strict hygienic measures should be considered in areas of high prevalence of infection to lower the high load of environmental contamination.

New insights into the pathogenesis and transmission of Brucella pinnipedialis: systemic infection in two bottlenose dolphins (Tursiops truncatus).

IMPORTANCE: Brucella spp. are zoonotic pathogens that can affect both terrestrial and marine mammals. Brucella ceti has been identified in various cetacean species, but only one sequence type (ST27) has been reported in humans. However, it is important to conduct surveillance studies to better understand the impact of marine Brucella species on marine mammals, a typically understudied host group. Here, we describe a systemic infection by two related strains of Brucella pinnipedialis (ST25) in a couple of live-stranded bottlenose dolphins, with more severe lesions in the younger animal. Furthermore, B. pinnipedialis was first detected in milk from a female cetacean that stranded with its offspring. Our study reveals novel insights into the epidemiology and pathological consequences of B. pinnipedialis infections in cetaceans, emphasizing the crucial importance of ongoing surveillance and accurate diagnosis to understand the impact of this pathogen on marine mammal populations.

Phylogeography and epidemiology of Brucella suis biovar 2 in wildlife and domestic swine.

Swine brucellosis due to Brucella suis biovar 2 (bv2) is enzootic in wild boar and hare in continental Europe and may cause major economic losses to the pig industry, mainly in free-ranged pig farms. The high nucleotide identity found among the B. suis biovar 2 isolates has long hindered the full understanding of the epidemiology and the phylogeography of the disease. Here, we used multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) and whole-genome analysis to identify single-nucleotide polymorphisms (SNPs) in order to gain insights from the largest B. suis bv2 dataset analyzed so far composed of domestic pigs and wildlife isolates collected throughout Europe since the 1970s. We found four major clades with a specific phylogeographic pattern. The Iberian clade contains isolates exclusively from the Iberian Peninsula. The Central European clade includes most isolates from France, Northern Italy, Switzerland and an important proportion of those of Northern Spain. The Eastern European clade clustered isolates from Croatia and Hungary mainly but also from areas of France, Germany, Italy and Poland. Finally, a separated Sardinian clade grouped three isolates from this island. At fine scale, MLVA demonstrated an endemic status of the infection in Europe and it allowed tracking a large outbreak formed by different farms from Spain linked to the same infection source. The whole genome SNP analysis showed that the strains form genetically distinct clades, shared between wild boar and pigs, in agreement with the MLVA clades. Interestingly, all hare isolates clustered together within two groups composed exclusively of wildlife isolates. Our results support the hypothesis that maintenance and spread of B. suis bv2 in Europe is a dynamic process linked to the natural expansion of wild boar as the main wild reservoir of the infection, while spread over long distances is found largely dependent on anthropogenic activities.

Characterization of Salmonella enterica Serovar Typhimurium Isolates from Pigs and Pig Environment-Related Sources and Evidence of New Circulating Monophasic Strains in Spain.

A total of 117 Salmonella enterica serovar Typhimurium and 59 monophasic Salmonella Typhimurium (S. enterica serovar 4,[5],12:i:-) strains isolated between 2008 and 2012 from pig, wild bird, rodent, and farm environment samples from the northeast of Spain were characterized by phage typing, antibiotic susceptibility testing, and multiple-locus variable-number tandem repeat analysis in order to evaluate their phenotypic and genetic relatedness. In Salmonella 4,[5],12:i:-, the most prevalent phage types were U311 (40.7%) and DT195 (22%), which did not correspond with the so-called Spanish clone and generally showed a different resistance pattern (ASSuT). Antibiotic resistance was found in 85.8% of the isolates, with 94.1% of them displaying multidrug resistance. Multiple-locus variable-number tandem repeat analysis identified 92 different profiles, six of them shared by both serovars. The minimum spanning tree showed one major cluster that included 95% of the Salmonella 4,[5],12:i:- isolates, which came from different animal sources, geographic locations, and time periods, suggesting high clonality among those Salmonella strains and the ability to spread among pig farms. Overall, isolates of Salmonella 4,[5],12:i:- were more similar to European strains than to the well-characterized Spanish clone. The spread of these new strains of Salmonella 4,[5],12:i:- would likely have been favored by the important pig trade between this Spanish region and other European countries. The overall high prevalence of multidrug resistance observed in these new strains should be noted.