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Chapter 172 – Gram-negative coccobacilli

Mary P.E. Slack


The Gram-negative coccobacilli that are important human pathogens including Bordetella, Brucella, Francisella, Haemophilus, Legionella, Pasteurella and Yersinia spp. Actinobacillus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella and Moraxella spp. occasionally cause human disease. All of these genera except Yersinia are fastidious, requiring special nutrients and growth factors for isolation. Like other members of the Enterobacteriaceae, Yersinia spp. are not exacting in their growth requirements.

The genera Brucella, Francisella, Pasteurella and Yersinia cause zoonotic infections in humans. Legionella infections are acquired through exposure to environmental contamination. Haemophilus and most Bordetella infections arise through person-to-person transmission. Rarely Bordetella bronchiseptica, an animal pathogen, produces opportunistic human infections.