Open Access
Research (Published online: 07-08-2021)
7. Biological and molecular characterization of a sheep pathogen isolate of Mannheimia haemolytica and leukotoxin production kinetics
Dounia Bkiri, Noha Semmate, Zineb Boumart, Najete Safini, Fatima Zohra Fakri, Zahra Bamouh, Khalid Omari Tadlaoui, Siham Fellahi, Noursaid Tligui, Ouafaa Fassi Fihri and Mehdi El Harrak
Veterinary World, 14(8): 2031-2040

Dounia Bkiri: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco; Department of Microbiology, Immunology and Contagious Diseases, Institute of Agronomy and Veterinary Medicine Hassan II, Rabat, Morocco.
Noha Semmate: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco.
Zineb Boumart: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco.
Najete Safini: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco.
Fatima Zohra Fakri: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco.
Zahra Bamouh: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco.
Khalid Omari Tadlaoui: Department of Research and Development, Multi-chemical Industry, Mohammedia, Morocco.
Siham Fellahi: Department of Microbiology, Immunology and Contagious Diseases, Institute of Agronomy and Veterinary Medicine Hassan II, Rabat, Morocco.
Noursaid Tligui: Department of Microbiology, Immunology and Contagious Diseases, Institute of Agronomy and Veterinary Medicine Hassan II, Rabat, Morocco.
Ouafaa Fassi Fihri: Department of Microbiology, Immunology and Contagious Diseases, Institute of Agronomy and Veterinary Medicine Hassan II, Rabat, Morocco.
Mehdi El Harrak: Department of Microbiology, Immunology and Contagious Diseases, Institute of Agronomy and Veterinary Medicine Hassan II, Rabat, Morocco.

doi: www.doi.org/10.14202/vetworld.2021.2031-2040

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Article history: Received: 28-03-2021, Accepted: 25-06-2021, Published online: 07-08-2021

Corresponding author: Dounia Bkiri

E-mail: D.bkiri@mci-santeanimale.com

Citation: Bkiri D, Semmate N, Boumart Z, Safini N, Fakri FZ, Bamouh Z, Omari Tadlaoui K, Fellahi S, Tligui N, Fassi Fihri O, El Harrak M (2021) Biological and molecular characterization of a sheep pathogen isolate of Mannheimia haemolytica and leukotoxin production kinetics, Veterinary World, 14(8): 2031-2040.
Abstract

Background and Aim: Mannheimia haemolytica (Mha) is a common agent of pneumonia in ruminants globally, causing economic losses by morbidity, mortality, and treatment costs. Infection by Mha is often associated with or promoted by respiratory viral pathogens and environmental conditions. Infections due to Mha have rarely been described in small ruminants. This study reports the biological and molecular characteristics of a new Moroccan Mha isolate from small ruminants presenting typical respiratory symptoms. We also studied the cultural parameters, growth kinetics, and Lkt excretion of the isolate and its pathogenicity on laboratory animals and small ruminants.

Materials and Methods: Suspected pasteurellosis cases in sheep and goat flocks in Morocco were investigated. A local strain of Mha was isolated and identified using biochemical and molecular methods. Polymerase chain reaction-targeting specific genes were used for serotyping and phylogenetic analyses; further, leukotoxin production, cytotoxicity, and pathogenicity of the isolate in mice, goats, and sheep were investigated.

Results: Phylogeny analysis revealed 98.76% sequence identity with the USA isolate of 2013; the strain growth with a cycle of 9-10 h with leukotoxin secretion was detected by NETosis and quantified by cytotoxicity and mortality of mice. Goat and sheep infections cause hyperthermia, with characteristic postmortem lesions in the trachea and lung.

Conclusion: A local isolate of Mha from sheep that died of pneumonia was characterized for the 1st time in North Africa using biological and molecular methods. Although growth on appropriate culture media is accompanied by intense leukotoxin secretion, experimental infections of sheep and goats cause hyperthermia and typical lesions of pneumonia.

Keywords: histopathology, isolation, leukotoxin, Mannheimia haemolytica, phylogeny, polymerase chain reaction.