Vaginal and uterine volatile organic compound profiles, bacterial isolates, and antimicrobial susceptibility in canine pyometra.

Abstract

Canine pyometra is a life-threatening uterine disease requiring timely diagnosis and appropriate antimicrobial treatment. This study characterized uterine bacteria and antimicrobial susceptibility and compared vaginal and uterine volatile organic compound (VOC) profiles in 27 bitches with pyometra (14 open-cervix, 13 closed-cervix) and 14 healthy controls. Uterine isolates were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and susceptibility was assessed by disk diffusion. Vaginal and uterine swabs were analyzed by headspace solid-phase microextraction-gas chromatography-mass spectrometry. Aerobic bacterial growth occurred in 17/27 pyometra cases (63.0%), yielding nine species; Escherichia coli was most frequent (4/17 isolates; 23.5%). Chloramphenicol had the highest proportion of susceptible isolates (94.1%), whereas cephalexin had the highest resistance proportion (58.8%); one E. coli isolate was multidrug resistant. Among eight shared VOC features, VOC-1 and VOC-2 had greater peak areas in vaginal (P = 0.004 and 0.005) and uterine (P = 0.002 and 0.001) pyometra samples than controls. VOC-3 differed significantly only in uterine samples (P = 0.009). However, vaginal VOC-1, VOC-2, and VOC-3 did not significantly distinguish closed-cervix pyometra from healthy controls. Compound assignments were tentative (Metabolomics Standards Initiative Level 2/3), based on library matches without confirmation using authentic standards. These exploratory findings characterize uterine bacterial isolates, antimicrobial susceptibility, and vaginal and uterine VOC profiles in canine pyometra. Chemical confirmation and validation in larger independent cohorts are required before diagnostic application, particularly in closed-cervix cases.

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