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INTRODUCTION

Vibrio, Aeromonas, Campylobacter, and Helicobacter are Gram-negative rods that are all widely distributed in nature. The vibrios are found in marine and surface waters. Aeromonads are inhabitants of aquatic ecosystems, worldwide, and are found in fresh and brackish waters. The campylobacters are found in many species of animals, including many domesticated animals. Helicobacters are found in the gastrointestinal and hepatobiliary tracts of humans and various other mammals (eg, dogs, cats, cattle, and dolphins), as well as chickens and wild birds. Vibrio cholerae produces an enterotoxin that causes cholera, a profuse watery diarrhea that can rapidly lead to dehydration and death. Campylobacter jejuni is a common cause of enteritis in humans. Helicobacter pylori is associated with gastritis and duodenal ulcer disease.

THE VIBRIOS

Vibrios are among the most common bacteria in marine and estuarine waters, worldwide. They are comma-shaped, curved, and sometimes straight facultatively anaerobic, fermentative rods; they are catalase and oxidase positive, and most species are motile by means of monotrichous or multitrichous polar flagella. Vibrios can grow within a broad temperature range (14–40°C), and all species require sodium chloride (NaCl) for growth; hence the term halophilic (“salt loving”). V. cholerae serogroups O1 and O139 cause cholera in humans, and other vibrios, most commonly V. parahaemolyticus and V. vulnificus, are important human pathogens, causing skin and soft tissue infections, sepsis, or gastroenteritis. The medically important vibrios are listed in Table 17-1.

TABLE 17-1The Medically Important Vibrios

VIBRIO CHOLERAE

The bacterium V. cholerae is the cause of cholera. The epidemiology of cholera closely parallels the recognition of V. cholerae transmission in water and the development of sanitary water systems. Cholera is associated with poor sanitation, as well as direct contact with or consumption of contaminated water and/or food (eg, water used for drinking, cooking, bathing, and crop irrigation).

Morphology and Identification

A. Typical Organisms

Upon first isolation, V. cholerae is a comma-shaped, curved rod 2–4 µm long (Figure 17-1). It is actively motile by means of a polar flagellum. On prolonged cultivation, organisms may become straight rods that can resemble other Gram-negative enteric bacteria.

FIGURE 17-1

Gram-stain of V. cholerae. Often they are comma shaped or slightly curved (arrows) and 1 × 2 to 4 µm. Original magnification ×1000.

B. Culture

V. cholerae produces convex, smooth, round colonies that are opaque and granular ...

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