Reproductive performance of gilts following an outbreak of acute proliferative enteropathy due to Lawsonia intracellularis

Spread of an Experimental Salmonella Derby Infection in Antibiotic-Treated or Lawsonia intracellularis Vaccinated Piglets

Lawsonia intracellularis infections are a common reason for antibiotic treatment in pig production. Experimental studies in animals naturally infected with Lawsonia intracellularis comparing the course of an experimental Salmonella infection in piglets previously treated with tylosin or vaccinated against Lawsonia intracellularis are scarce. A total of 72 seven-week-old Salmonella-free pigs were taken from a herd with a Lawsonia intracellularis history in piglet rearing. The pigs were divided into two groups with three replicates each. Animals had either been previously treated with tylosin (10 mg/kg body weight) for seven days (AB⁺VAC^-) or had been vaccinated as suckling pigs by drenching (Enterisol^®Ileitis; AB^-VAC⁺). Two animals per replicate were primarily infected with Salmonella Derby (1.04 × 10⁸ colony-forming units per animal). The detection of Salmonella in faeces (p < 0.0001, odds ratio: 3.8364) and in the ileocaecal lymph nodes (p = 0.0295, odds ratio: 3.5043) was significantly more frequent in AB⁺VAC^- animals. Overall, the odds ratio for detecting Salmonella in any substrate or organ was significantly higher in the AB⁺VAC^- group animals (p = 0.0004, odds ratio: 5.9091). Treatment with tylosin can significantly increase the spread of a Salmonella infection, which is not observed after early Lawsonia intracellularis vaccination.

Lawsonia intracellularis contains a gene encoding a functional rickettsia-like ATP/ADP translocase for host exploitation

ATP/ADP translocases are a hallmark of obligate intracellular pathogens related to chlamydiae and rickettsiae. These proteins catalyze the highly specific exchange of bacterial ADP against host ATP and thus allow bacteria to exploit their hosts' energy pool, a process also referred to as energy parasitism. The genome sequence of the obligate intracellular pathogen Lawsonia intracellularis (Deltaproteobacteria), responsible for one of the most economically important diseases in the swine industry worldwide, revealed the presence of a putative ATP/ADP translocase most similar to known ATP/ADP translocases of chlamydiae and rickettsiae (around 47% amino acid sequence identity). The gene coding for the putative ATP/ADP translocase of L. intracellularis (L. intracellularis nucleotide transporter 1 [NTT1(Li)]) was cloned and expressed in the heterologous host Escherichia coli. The transport properties of NTT1(Li) were determined by measuring the uptake of radioactively labeled substrates by E. coli. NTT1(Li) transported ATP in a counterexchange mode with ADP in a highly specific manner; the substrate affinities determined were 236.3 (+/- 36.5) microM for ATP and 275.2 (+/- 28.1) microM for ADP, identifying this protein as a functional ATP/ADP translocase. NTT1(Li) is the first ATP/ADP translocase from a bacterium not related to Chlamydiae or Rickettsiales, showing that energy parasitism by ATP/ADP translocases is more widespread than previously recognized. The occurrence of an ATP/ADP translocase in L. intracellularis is explained by a relatively recent horizontal gene transfer event with rickettsiae as donors.