Clinical and radiographic findings in Corynebacterium equi pneumonia of foals

Abstract

SUMMARY Thirty-nine foals with pneumonia were admitted to the Veterinary Medical Teaching Hospital at the University of California, Davis. Corynebacterium equi was recovered from each of them on bacteriologic culture of transtracheal aspiration specimens or lung specimens at necropsy. The foals were divided into 2 groups. Group I consisted of 20 foals that died because of C equi pneumonia and were subsequently necropsied. Group II consisted of 19 foals that were treated and discharged from the hospital. Radiography was performed on all foals. Clinical signs included increased respiratory rate, fever, cough, nasal discharge, increased bronchovesicular sounds over large airways, and wheezing over small airways. Highly significant differences were found in the mean respiratory rate ( P <0.005) and temperature ( P <0.001), recorded at admission, between the 2 groups; both factors were higher for group I. Hematology revealed leukocytosis with neutrophilia, monocytosis, and high plasma fibrinogen content in all foals. Significant differences were recorded in the mean total leukocyte count ( P <0.05), mean neutrophil count ( P <0.05), mean monocyte count ( P <0.005), and mean fibrinogen value ( P <0.05) between the 2 groups; values from group I were higher than those from group II. Although C equi was isolated alone from 25 of the tracheal aspirates and lung specimens, 14 cultures yielded multiple pathogens. At the time of initial examination, all foals had radiographic evidence of pneumonia. Pulmonary consolidation indicative of bronchopneumonia was identified in 31 of the 39 foals. Lymphadenopathy, nodular lesions, and cavitary lesions were more frequently seen in foals that were treated unsuccessfully than in those that were treated successfully. Pleural effusion was an infrequent finding (2/39). Both the Kirby-Bauer method and determination of the minimal inhibitory concentration were used for antimicrobial sensitivity testing. Gentamicin, erythromycin, and trimethoprim/sulfa were found to have the lowest effective concentrations for C equi isolated (0.25 to 0.5 μg/ml) for most isolates tested.