Fatal suppurative meningoencephalitis caused by Klebsiella pneumoniae in two calves

Abstract

One calf died (No. 1) and another was euthanized following astasia (No. 2). Histopathological examination revealed suppurative meningoencephalitis in these calves. Klebsiella pneumoniae antigens were detected in lesions. Thymocytes were decreased in the thymus cortex in both cases. 16S rRNA gene sequencing of the No. 1 isolate and bacterial extracts from formalin fixed paraffin embedded sections of No. 2 revealed that both samples were K. pneumoniae. The No. 1 isolate showed multidrug resistance against penicillin antibiotics, fosfomycin, streptomycin, macrolide antibiotics, tetracycline antibiotics, and clindamycin. Immunosuppression is a significant septicemic K. pneumoniae infection risk factor. Our study provides new aspects regarding K. pneumoniae infections in cattle, bacterial meningoencephalitis differentiation, and K. pneumoniae and bacterial meningoencephalitis treatments.

Keywords: Klebsiella pneumoniae; cattle; meningoencephalitis; multidrug resistance.

Fig. 1.

a. At necropsy, congestion was found in the meningeal vessels of No. 1 calf. b. Suppurative exudate was seen in the brain sulcus of No. 2 calf. The meninges were slightly thick.

Fig. 2.

a. Mild to moderate neutrophilic infiltrations in the meninges of No. 1. Hemorrhages (arrowheads) were present in brain meninges. Hematoxylin and eosin (H&E) staining. Bar=100 µm. b. Widespread necrosis in the corpus striatum of No. 2. Perivascular infiltrations are scattered in the lesion (arrows). H&E staining. Bar=200 µm. c. Numerous bacteria freely existed in the blood vessels (arrows) of the umbilical cord in No. 1. Neutrophils (arrowheads) and macrophages were infiltrated around vessels. H&E staining. Bar=50 µm. d. Numerous gram-negative bacteria existed freely in the blood vessels (arrows) of the umbilical cord in No. 1. Gram staining. Bar=10 µm. e. Thymocytes were decreased and collagen fibers were increased in thymus cortex in No. 2. H&E staining. Bar=50 µm. f. K. pneumoniae antigen (red) was detected in meninges and blood vessels (arrows) in No. 1. Immunohistochemical staining. Bar=50 µm. g. Many K. pneumoniae antigens were detected in the blood vessels of the umbilical cord (arrows) and cytoplasm of infiltrated macrophages (arrowhead) in No. 1. Immunohistochemical staining. Bar=20 µm. h. K. pneumoniae antigens were detected in the cytoplasm of infiltrated macrophages and infiltrating neutrophils in the perivascular space of the corpus striatum of No. 2. Immunohistochemical staining. Bar=50 µm.