Effect of subinhibitory exposure to quaternary ammonium compounds on the ciprofloxacin susceptibility of Escherichia coli strains in animal husbandry.

BACKGROUND: Quaternary ammonium compound based disinfectants are commonly used in pig and poultry husbandry to maintain farm hygiene. However, studies have shown that subinhibitory concentrations of these disinfectants may increase antibiotic resistance. Investigation of antibiotic susceptibility is usually assessed via the microbroth dilution method, although this conventional culture-based technique only provides information on the bacteriostatic activity of an antimicrobial agent. Therefore, experiments were performed to investigate the effect of prior benzalkonium chloride (BKC) exposure on the viability of subsequent ciprofloxacin (CIP) treated Escherichia coli. RESULTS: Following CIP treatment, bacterial cell counts were significantly higher after exposure to a subinhibitory BKC concentration than without BKC exposure. The flow cytometric results suggested a BKC-dependent onset of membrane damage and loss of membrane potential. CONCLUSION: Our results indicate a lower bactericidal effect of CIP treatment on BKC-exposed E. coli isolates compared to unexposed E. coli isolates.

Secreted phospholipase A2 inhibitor modulates fatty acid composition and reduces obesity-induced inflammation in Beagle dogs.

Secreted phospholipase A2 inhibitor (sPLA2i) has been reported to have an anti-inflammatory function by blocking the production of inflammatory mediators. Obesity is characterized by low-grade inflammation and oxidative stress. The aim of this study was to investigate the effects of dietary supplementation of sPLA2i on inflammation, oxidative stress and serum fatty acid profile in dogs. Seven obese and seven lean Beagle dogs were used in a 28-day double blind cross-over design. Dogs were fed a control diet without supplemental sPLA2i or an sPLA2i supplemented diet. The sPLA2i diet decreased plasma fibrinogen levels and increased the protein:fibrinogen ratio in obese dogs to levels similar to those of lean dogs fed the same diet. Obese dogs had a higher plasma concentration of the lipophilic vitamin A with potential antioxidative capacity and a lower ratio of retinol binding protein 4:vitamin A compared to lean dogs, independent of the diets. A higher proportion of myristic acid (C14:0) and a lower proportion of linoleic acid (C18:2n-6) were observed in the dogs fed with the sPLA2i diet compared to dogs fed with the control diet. Furthermore, a higher ratio of n-6 to n-3, a lower proportion of n-3 polyunsaturated fatty acids and lower omega-3 index were observed in obese compared to lean dogs. The results indicate that obese dogs are characterized by a more 'proinflammatory' serum fatty acid profile and that diet inclusion of sPLA2i may reduce inflammation and alter fatty acid profile.

Heifer and quarter characteristics associated with periparturient blood and milk neutrophil apoptosis in healthy heifers and in heifers with subclinical mastitis.

Polymorphonuclear neutrophilic leukocytes (PMNL) play an important role in the first line cell-mediated immune defense of the body in general and of the mammary gland against mastitis pathogens in particular. Reduced viability of PMNL close to parturition may explain the high incidence of infectious diseases and the high prevalence of intramammary infections (IMI) in periparturient dairy heifers. Apoptosis of blood PMNL 1 wk before the expected calving date and of blood and milk PMNL at 1 to 4 d in milk was determined using flow cytometry. Information on heifer and gland characteristics was collected before calving and in early lactation. Data were analyzed using multivariable, multilevel regression analysis. Supplementation of a commercial mineral/vitamin mix before calving was associated with less blood (14.4 +/- 2.9 vs. 22.4 +/- 2.1%) and milk PMNL apoptosis (19.0 +/- 1.1 vs. 26.4 +/- 0.9%) near calving, presumably related to higher blood selenium concentrations. Both blood and milk PMNL apoptosis showed seasonal variation with the highest proportion of apoptotic cells between January and March (32.0 +/- 6.1 and 34.6 +/- 2.7%, respectively) and April and June (31.3 +/- 5.7 and 37.8 +/- 2.3%, respectively). Heifers losing 0.25 points or more of their body condition in the periparturient period had higher proportions of apoptotic blood PMNL in early lactation compared with heifers losing less than 0.25 points (24.0 +/- 2.8 vs. 16.6 +/- 1.7%). Milk PMNL apoptosis was less pronounced in quarters having teat orifices colonized with non-aureus staphylococci before calving (18.9 +/- 1.0 vs. 29.4 +/- 1.0%). The variation in blood PMNL apoptosis before and after calving mainly resided at the heifer level (71.4 and 98.4% of the total variation, respectively), whereas the variation in milk PMNL apoptosis mainly resided at the heifer (45.7% of the total variation) and quarter levels (45.5% of the total variation). These data imply that the impaired blood and milk PMNL viability in periparturient heifers can be reduced by optimization of certain heifer management practices such as supplementation of minerals/vitamins, and pasture and feeding strategies.