DOI: 10.31196/huvfd.1939094 ISSN: 2146-717X

Microbiological and Histopathological Investigation of Necropsy-Confirmed Lobar Pneumonia in Lambs

Zeynep Yerlikaya, Burak Karabulut, Eren Çankaya, Muhammed Girgin, Pelin Fatoş Polat Dinçer, Hatice Eröksüz
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Lobar pneumonia is a significant cause of losses in lamb raising, yet there is limited integrated necropsy-based data linking histopathology with microbiological identification and susceptibility testing. This study investigated the etiological diversity of lobar pneumonia among 118 lambs submitted for routine necropsy in 2025. Thirty-six lungs with gross lesions consistent with lobar pneumonia were histologically classified as catarrhal purulent bronchopneumonia (n=20), fibrinous pneumonia (n=9), or purulent necrotizing bronchopneumonia (n=7). Fresh tissues were cultured on blood and chocolate agar and incubated at 37°C for 48 hours under both aerobic and 10% CO₂ conditions. Isolates were identified through MALDI-TOF MS, and Mycoplasma spp. DNA was screened using conventional PCR. Antimicrobial susceptibility testing employed the Kirby-Bauer disk diffusion method with a panel of antibiotics including ampicillin, amoxicillin/clavulanic acid, cefotaxime, tetracycline, trimethoprim-sulfamethoxazole, ciprofloxacin, and gentamicin. Bacterial growth was observed in 25 of 36 lungs, yielding 33 isolates, predominantly Escherichia coli (n=10) and Pasteurella multocida (n=6). Mycoplasma spp. DNA was detected in 13 lungs, including two culture-negative samples. Pasteurellaceae were significantly more common in fibrinous/purulent necrotizing bronchopneumonia compared to catarrhal purulent bronchopneumonia (p<0.001). Resistance in E. coli was most frequent to ampicillin and trimethoprim-sulfamethoxazole, while susceptibility to amoxicillin/clavulanic acid and cefotaxime was maintained. Overall, these results illustrate pattern-specific etiological profiles and support the use of integrated necropsy-based investigation for lamb pneumonia.

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