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UDC 619:616.98:579.84

Received: April 27, 2026

Revised: May 4, 2026

Published: May 29, 2026

This is an Open Access article under the CC BY-NC-ND 4.0 license

 

The study investigated the cytotoxic activity of clinical isolates of Bordetella bronchiseptica and its relationship with the dermonecrotic effect as a manifestation of pathogen virulence. The study was conducted on 24 isolates obtained from dogs and cats with signs of respiratory pathology. Cytotoxicity was determined in vitro on Vero cell culture based on the level of cellular metabolic activity (OD₄₉₀), followed by calculation of the cytotoxicity index (ΔOD₄₉₀). Dermonecrotic activity was assessed in vivo in laboratory mice using a semi-quantitative scale (0–3 points). It was established that the isolates were characterized by significant variability in toxigenic properties: the cytotoxicity index (ΔOD₄₉₀) ranged from 0.34 to 0.80, while the severity of dermonecrotic lesions ranged from 0 to 3 points. Most isolates demonstrated a moderate level of cytotoxic activity (45.8%), whereas a high level was detected in 29.2% of cases and a low level in 25.0%. Similarly, dermonecrotic lesions of moderate severity (37.5%) were most frequently recorded, whereas severe lesions and the absence of lesions were observed considerably less often. It was shown that isolates with low cytotoxicity index values (<0.45 ΔOD₄₉₀) predominantly did not cause or caused minimal lesions, whereas at high values (>0.65 ΔOD₄₉₀) more pronounced dermonecrotic lesions were more frequently observed. At the same time, certain discrepancies between the level of cytotoxicity and the severity of dermonecrotic skin lesions were identified, indicating a complex and nonlinear nature of the relationship between the studied parameters. Correlation analysis confirmed the presence of a moderate positive relationship between cytotoxic activity and dermonecrotic effect (r = 0.48; p < 0.05), indicating partial consistency of the mechanisms of cellular damage and the development of necrotic changes. The obtained results indicate that cytotoxicity can be considered as an integral indicator of the toxigenicity of isolates and an informative indicator of their dermonecrotic potential. At the same time, the observed variability of the indicators emphasizes that dermonecrosis is a multifactorial process and is not determined exclusively by cytotoxic action. This substantiates the expediency of a comprehensive approach to the assessment of the virulent properties of B. bronchiseptica. The obtained data confirm the possibility of using in vitro methods for assessing cytotoxicity as an alternative approach for the preliminary characterization of isolate virulence, which has practical significance and complies with modern bioethical requirements regarding the reduction of laboratory animal use.

 

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