Storage time and temperature affect the isolation rate of Mannheimia haemolytica and Pasteurella multocida from bovine bronchoalveolar lavage samples

Abstract

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background:</jats:bold> A microbiological diagnosis is essential to better target antimicrobial treatment, control and prevention of respiratory tract infections in cattle. Under field conditions, non-endoscopic broncho-alveolar lavage (nBAL) samples are increasingly collected. To what extent the highly variable turnaround time and storage temperatures between sampling and cultivation affect the isolation rate of bacterial pathogens is unknown. Therefore, the objective of this experimental study was to determine the effect of different storage temperatures (0°C, 8°C, 23°C and 36°C) and times (0,2,4,6,8,24,48 hours) on the isolation rate and concentration of <jats:italic>Pasteurellaceae</jats:italic> in nBAL samples from clinically affected animals.<jats:bold>Results</jats:bold>: At a storage temperature temperature of 36°C isolation rates of <jats:italic>Mannheimia haemolytica</jats:italic> and <jats:italic>Pasteurella multocida</jats:italic> were significantly reduced 6h and 48h after sampling, respectively. At room temperature (23°C), a decrease in <jats:italic>M. haemolytica </jats:italic>and <jats:italic>P. multocida</jats:italic> isolation rate was noticed, starting at 24 and 48 hours after sampling, respectively, but only significant for <jats:italic>P. multocida</jats:italic> at 48h. The presence of microbial contamination negatively affected the isolation of <jats:italic>P. multocida </jats:italic>in clinical nBAL samples, but not of <jats:italic>M. haemolytica</jats:italic>. <jats:bold>Conclusion</jats:bold>: Optimal <jats:italic>M. haemolytica </jats:italic>and<jats:italic> P. multocida</jats:italic> isolation rates from clinical nBAL samples are obtained after storage at 0°C or 8°C, provided that the sample is cultivated within 24 hours after sampling. The maximum period a sample can be stored without an effect on the <jats:italic>M. haemolytica</jats:italic> and <jats:italic>P. multocida</jats:italic> isolation success varies and is dependent on the storage temperature and the degree of microbial contamination.</jats:p>