Đurđa Slavić, Murray Hazlett

Animal Health Laboratory, University of Guelph, ON

AHL Newsletter 2020;24(1):18.

Having trouble with some of those strange-sounding bacterial species on your laboratory report? Can’t remember if Terrisporobacter glycolicus is a bacteria or fungus? You are not alone. With more precise bacterial identification available through automated devices such as the MALDI-TOF used at the AHL, new taxonomy classification schemes by microbiologists, better bacterial transport and isolation techniques, as well as PCR techniques such as 16S ribosomal RNA, a whole brave new world of bacteria (or at least bacterial names!) is being unleashed upon the unsuspecting clinician and pathologist. Between April 1st and June 30th 2019, approximately 211 different bacterial species were reported on equine cases submitted for culture at the AHL. The most common isolates are well known; however, many others are not. Interpreting the significance of bacterial isolates depends on the clinical picture and the site associated with the sample, as always.

Bacteria that are listed in a bacteriology report will either have at least one report in the literature of involvement in disease (not necessarily in horses) and/or may be reported, depending on the clinical history, if they are one of the dominant isolates taken from a sterile site. We thought it may be useful to highlight a few of these bacteria. To qualify, they had to be reported in more than 4 equine cases in the last quarter and be something that a pathologist would have to ask about (or Google!).

Nicoletella semolina:  6 isolates were reported from 5 cases. All were from guttural pouch, trachea, bronchoalveolar lavage fluid (BAL) or from a submandibular swelling. This Gram-negative bacillus is a member of the Pasteurellaceae family and is usually isolated from horses with respiratory disease. However, this does not necessarily mean it is the cause of the disease, as this bacterium can also be isolated from respiratory tract of clinically healthy horses. 

Streptococcus thoraltensis: 4 isolates from 3 cases. All were from guttural pouch or pharyngeal mucosa.  It has been described in humans with fever of unknown origin and isolated from the oral cavity; also from porcine vaginal and intestinal samples.

Staphylococcus vitulinus: 5 isolates from 5 cases. This bacteria is a coagulase negative Staphylococcus species that is isolated from human clinical samples (urine), as well as from calves, horses, fish and meat products. AHL