Comparison of two bacterial transport media for culture of tonsilar swabs from bighorn sheep and mountain goats

Monitoring of respiratory pathogens in bighorn sheep and mountain goats serves the purpose of understanding the relationships between these pathogens and population health, and comparing the pathogen distribution between... [ view full abstract ]

Monitoring of respiratory pathogens in bighorn sheep and mountain goats serves the purpose of understanding the relationships between these pathogens and population health, and comparing the pathogen distribution between populations. In live animals, bacterial cultures for Pasteurellaceae are usually done from tonsillar or oropharyngeal swabs that are placed in a bacteriologic transport media (BTM) specifically designed for transport of swab samples to the laboratory. BTM require refrigeration after sample collection, and must be received by the laboratory within 48-72 hours to achieve reasonable culture success. Practically, this means that samples need to be shipped on Monday – Thursday, which can be challenging when working in remote areas or if weather affects the capture schedule. Bacterial cryopreservation media (BCM), although not designed for specimen transport, may provide increased flexibility in the timing of shipping, since once frozen bacterial viability may be better preserved over time. For this reason, BCM have been increasingly used for transport of tonsillar or oropharyngeal swabs from bighorn sheep and mountain goats. However, BCM have not been systematically evaluated for survival and recovery of bacteria in comparison of conventional BTM. Duplicate tonsilar swabs were collected from 77 bighorn sheep and 19 mountain goats from 5 populations in Utah between October 2015 and January 2016. Swabs were refrigerated in agar-based bacteriologic transport media or frozen in TSB/glycerol cryogenic media prior to bacteriologic culture. On a herd level, the cryogenic media yielded comparable or superior bacterial growth, but the agreement between the two media was poor on an individual animal level. Based on these results, both BTM and BCM are suitable transport systems for swab samples from bighorn sheep and mountain goats, with BCM providing increased flexibility for capture scheduling and specimen shipment. The results should not be compared between individual animals, but are comparable on a herd level.