The Lipopolysaccharide Lipid A Long-Chain Fatty Acid Is Important for Rhizobium leguminosarum Growth and Stress Adaptation in Free-Living and Nodule Environments.

Rhizobium bacteria live in soil and plant environments, are capable of inducing symbiotic nodules on legumes, invade these nodules, and develop into bacteroids that fix atmospheric nitrogen into ammonia. Rhizobial lipopolysaccharide (LPS) is anchored in the bacterial outer membrane through a specialized lipid A containing a very long-chain fatty acid (VLCFA). VLCFA function for rhizobial growth in soil and plant environments is not well understood. Two genes, acpXL and lpxXL, encoding acyl carrier protein and acyltransferase, are among the six genes required for biosynthesis and transfer of VLCFA to lipid A. Rhizobium leguminosarum mutant strains acpXL, acpXL-/lpxXL-, and lpxXL- were examined for LPS structure, viability, and symbiosis. Mutations in acpXL and lpxXL abolished VLCFA attachment to lipid A. The acpXL mutant transferred a shorter acyl chain instead of VLCFA. Strains without lpxXL neither added VLCFA nor a shorter acyl chain. In all strains isolated from nodule bacteria, lipid A had longer acyl chains compared with laboratory-cultured bacteria, whereas mutant strains displayed altered membrane properties, modified cationic peptide sensitivity, and diminished levels of cyclic ß-glucans. In pea nodules, mutant bacteroids were atypically formed and nitrogen fixation and senescence were affected. The role of VLCFA for rhizobial environmental fitness is discussed.

In vitro Effect of Photoactive Compounds Curcumin and Chlorophyllin Against Single Strains of Salmonella and Campylobacter.

Salmonella and Campylobacter are two of the most common foodborne pathogens associated with poultry meat. Regulatory restrictions and consumer concerns have increased the interest for plant-derived antimicrobials and emerging novel technologies. The objective of this study was to determine the antimicrobial activity of photoactive compounds curcumin (CUR) and chlorophyllin (CH) followed by activating light exposure for the reduction of Salmonella and Campylobacter. Peroxyacetic acid (PAA) was also evaluated as a poultry industry standard antimicrobial processing aid. CUR and CH were evaluated in 96-well plates at concentrations of 100, 500, and 1,000 ppm, along with PAA at 100, 200, and 300 ppm, or distilled water (DW). Each well was inoculated with 105 CFU/mL of Salmonella Typhimurium or Campylobacter jejuni, and plates were exposed to activating light (430 nm) for 0 or 5 min. No detectable reductions were observed for Salmonella or Campylobacter when treated with CUR, CH, or 100 ppm PAA. However, when Salmonella was treated with 200 ppm PAA, counts were reduced from 4.57 to 2.52 log10 CFU/mL. When Salmonella was treated with 300 ppm PAA, counts were reduced to below detectable levels (5 CFU/mL). Campylobacter was reduced from 4.67 to 2.82 log10 CFU/mL when treated with 200 ppm PAA. However, no further reductions were observed when Campylobacter was treated with 300 ppm PAA (2.50 log10 CFU/mL). These results indicate that CUR and CH were not effective as antimicrobials under the evaluated conditions, particularly in comparison to the commonly used antimicrobial, PAA.

Investigation of the potential of aerosolized Salmonella Enteritidis on colonization and persistence in broilers from day 3 to 21.

The presence of Salmonella in air of poultry houses has been previously confirmed. Therefore, it is important to investigate the entry of Salmonella into broilers through air. The present study aimed to evaluate different levels of Salmonella Enteritidis aerosol inoculations in broiler chicks for colonization of ceca, trachea, and liver/spleen and persistence over time. In 3 independent trials, 112 one-day-old birds were randomly divided into 4 groups (n = 28/group). On d 1 of age, one group was exposed to an aerosol of sterile saline and the remaining three groups were exposed to an aerosol generated from one of 3 doses (103, 106, or 109 CFU/mL) of S. Enteritidis inoculum. Aerosol exposure time was 30 min/group and was performed using a nebulizer. On d 3, 7, 14, and 21 of age, ceca, trachea, and liver/spleen were aseptically removed. Ceca were cultured for Salmonella counts (log10 CFU/g) and all tissues were cultured for Salmonella prevalence. All tissues from the control group were Salmonella negative for all sampling days. On sampling d 3 and 7, ceca Salmonella counts were highest (5.14 and 5.11, respectively) when challenged with 109Salmonella (P ≤ 0.0281). Ceca Salmonella counts increased from d 3 (2.43) to d 7 (4.43), then remained constant when challenged at 103Salmonella, and counts decreased over time for all other groups. Tissue Salmonella prevalence increased with increasing challenge levels at all sampling timepoints (P ≤ 0.0213). Salmonella prevalence was low (0/18 to 4/18) and did not change over time following 103Salmonella challenge (P ≥ 0.2394). Prevalence decreased over time in ceca and trachea following 106 and 109Salmonella challenge (P ≤ 0.0483). Liver/spleen Salmonella prevalence increased from d 3 (13/18) to d 14 (18/18) and then decreased at d 21 (10/18) in birds exposed to an aerosol of 109Salmonella but remained constant over time for rest of the Salmonella inoculated groups. Overall, this study demonstrated the Salmonella colonization and persistence in different tissues in broilers following exposure to aerosolized Salmonella.