Association between adenosine triphosphate luminometry of feeding equipment and environmental and health parameters of preweaning calves on dairy farms.

The objective of this study was to examine the influence of different environmental factors on ATP luminometry measurements of feeding equipment and to investigate associations with health of preweaning calves and the levels of ATP identified through luminometry. On 50 commercial dairy farms in Quebec, Canada, ATP luminometry measurements (in relative light units, RLU) were obtained using the direct swabbing technique with Hygiena UltraSnap swabs and a liquid rinsing technique with the same swab for automatic milk feeders (AMF), bottles, buckets, esophageal tube feeders (ET), milk replacer, nipples, and water. During this visit, environmental factors (including temperature, air draft, humidity, ammonia, and bacterial count) were collected, and a clinical examination (including respiratory score and fecal score) was performed for all preweaning calves present at the farm. This process was repeated 4 times in a year, leading to collection of luminometer results, environmental parameters, and overall health of calves for each season per farm. Overall, a difference in luminometer results was seen between the different periods sampled for all feeding equipment (except the ET), milk replacer, and water, showing higher RLU values in spring and summer and lower values in autumn and winter. When comparing RLU measurements with environmental factors, only a low to negligible correlation could be found. When feeding equipment was classified as not contaminated or contaminated based on previously described cutoff values, a good agreement within a farm for the different seasons was noticed only for nipples (Gwet's agreement AC1 = 0.64), with a poor to moderate agreement for other feeding equipment. Regarding the different models of nipples, Peach Teat nipples showed higher RLU values compared with Merrick's nipples. An association was seen between the proportion of preweaning calves suffering from diarrhea on the farm and the contamination of AMF based on ATP luminometry (logistic regression estimate = 0.52). For other feeding equipment, milk replacer, and water, no significant associations were found. This study showed that ATP luminometry measurements of feeding equipment from preweaning calves are susceptible to seasonality and type of nipple. Thus, these factors should be taken into consideration when interpreting results. Additionally, an association could be made between diarrhea in preweaning calves and the contamination of AMF based on ATP luminometry, showing the potential clinical importance of this on-farm hygiene assessment tool.

In vitro efficacy of combinations of antibiotics used in clinical practice on clinical isolates of Helicobacter pylori.

BACKGROUND: The main antibiotics used against Helicobacter pylori have been chosen empirically over time, with few preclinical studies to provide support. The rise in resistance to some of these antibiotics is prompting a reassessment of their use. This work aimed to evaluate the in vitro efficacy of 2 × 2 combinations of the most widely used antibiotics against H. pylori. MATERIALS AND METHODS: J99 reference strains and 19 clinical isolates of H. pylori with various antibiotic resistance phenotypes were used. Minimum inhibitory concentrations were carried out using the microdilution method in 96-well plates. The activity of 15 possible combinations of two antibiotics including amoxicillin, clarithromycin (CLA), levofloxacin, rifampicin, tetracycline, and metronidazole was determined for all strains by the checkerboard method. A mean fractional inhibitory concentration index (FICmean) was calculated for each combination and strain and the type of pharmacodynamic interaction was considered as synergic if FICmean ≤ 0.5, additive if 0.5 < FICmean ≤ 1, indifferent if 1 < FICmean < 4 or antagonistic if FICmean ≥ 4. RESULTS: Most of the 285 pharmacodynamic interactions tested with clinical strains were close to additivity (average FICmean = 0.89 [0.38-1.28]). No interaction was found to be antagonistic. When two antibiotics to which a strain was resistant were combined, the concentrations required to inhibit bacterial growth were higher than their respective breakpoints. CONCLUSION: The present results have shown that in vitro, the different antibiotics used in therapeutics have additive effects. The addition of the effects of two antibiotics to which a strain was resistant was not sufficient to inhibit bacterial growth. In probabilistic treatment, the choice of antibiotics to combine should therefore be based on the local epidemiology of resistance, and on susceptibility testing in the case of CLA therapy, so that at least one antibiotic to which the strain is susceptible is used.