eChapters

Listeria has been divided into seven species with two distinct groups. Among which the Listeria monocyotgenes and Listeria ivanovii are haemolytic and pathogenic for animals. The Listeria murrayi and Listeria grayi are nonhaemolytic, rarely isolated and considered to be non pathogenic. Among which the genus L. monocytogens, being the cause of septicaemia, abortion and CNS infections in a wide range of animal species including humans.

History
L.monocytogenes first described by Murray (1926) who named it as bacterium monocytogenes because of characteristic monocytosis infection in laboratory animals. It was renamed Listerella hepatolytica by Pirie (1927) and the present name given by him in 1940. The Listeria momnocytogenes was first isolated by Gill (1929) from sheep.
Natural Habitat
Listeria species are widely distributed in the environment and can be isolated from soil, faeces, plants, decaying vegetation and silage (pH 5.5) in which the bacteria can multiply. Silage is commonly implicated in outbreaks of listeriosis in cattle and sheep. In poor quality silage the listerial numbers may reach 107 cfu/kg of silage. Asymptomatic faecal carriers occur in man and many animal species. L.monocytogens can be excreted in bovine milk. Human foods associated with listeriosis in man include soft cheeses, milk and poultry meat.

Natural Habitat
The bactrerium is widespread in nature and has been recovered from a wide variety of wild and domestic animals including mammals, fish (both fresh and salt water), birds, reptiles and amphibians. It is present in the soil and can survive for 20 days or longer in alkaline soil. The major source of infection for swine and turkeys is carrier animals of the same species. It is reported that 30-50% of pigs carry the bacterium in their tonsils, other lymphoid tissues. It is present in slurry of piglets and can be recovered from the faeces of carrier pigs.
Morpholgy
Erysipelothrix rhusiopathiae (previously named Erysipelothrix insidiosa) from S (Smooth) -form colonies and usually from acute syndromes is a grampositive rod, the R (rough) form colonies usually from chronic disease is a gram-positive filament. The organism is non-motile, non-spore forming, nonacid fast, capsulated occur either in singly, in groups or in chains.

Cultural Characters
It is a facultative anarobe, but growth is enhanced by 10% CO2. It is able to grow in a temperature range of 50C to 420C, within a pH range 6.7 to 9.2 and 8% NaCl2. Growth occurs on nutrient agar but is improved by the addition of serum or blood. It will not grow on Mac Conkey agar. Media contain either sodium azide (0.1%) or crystal violet (0.001%) may be used as selective media. On blood agar, non-haemolytic pinpoint colonies (0.5 mm) appear at 24hrs incubation. Colonial variation becomes obvious at 48hrs incubation when azone of greenish haemolysis often develops under and just around the colonies.
 

Mycobacteria are slender rods of varying lengths that sometimes show branching filamentous form resembling ‘fungal mycelium’. Hence, the name mycobacteria, meaning fungus like bacteria.
Although cytochemically gram positiive, the Mycobacteria do not take up the dyes of the gram stain because the cell walls are rich in lipids – Mycolic acid. Once a dye has been taken up by the cells they are not easily decolourised, even by acid-alcohol. Mycobacteria are therefore called as acid-fast bacilli. The genus includes animal and human pathogens as well as saprophytic members often referred to as atypical, anonymous, opportunistic, tuberculoid and MOTT (Mycobacteria other than typical tubercle) bacilli. Clasification of Mycobacteria (Tubercle Bacilli)
I. Slowly growing Mycobacteria
• Mycobacterium tuberculosis causes human tuberculosis in human and dogs.
• Mycobacterium bovis causes bovine tuberculosis in many animal species and also cause tuberculosis in human
• Mycobacterium africanum causes human tuberculosis.
• The human type (Mycobacterium tuberculosis) is primarily a pathogen for man. But can cause disease in cattle, pigs, dogs, monkeys, parrots and other species. The bovine type (Mycobacterium bovis) is a common cause of disease in domestic animal particularly cattle, pigs, cat, dogs and horse. The avian type (Mycobacterium avium) is primarily a pathogen for birds. But can cause disease in cattle, sheep, goat and pigs.

Corynebacteria are gram positive, non-acidfast, non-motile, non-capsulated, small pleomorphic rods. They frequently occur in rods, coccoid, club and filamentous shape. The term coryneform which refers to the pleomorphic club shape of these gram-positive bacteria. (From Coryne – meaning club). The major pathogen is Corynebacterium diptheria. Which causes diptheria in children. Corynebacteria associated with animals are called diphtheroids.

Morphology
They are gram-positive slender rod with a tendancy to clubbing at one or both ends; they are non-sporing, non-motile, non-capsulated and non-acidfast. They have granules composed of (high energy phosphate stores) – polymetaphosphate. The granules are more strongly gram positive than the rest of the bacterial cell. Stained with Loeffler’s methylene blue, the granules take up a reddish purple color and hence they are called metachromatic granules. They are called as volutinor Babes Ernst Granules. They are often situated at the poles of the bacilli and are called polar bodies. Special stains,
such as Albert’s, Neisser’s and Ponder’s have been devised for demonstrating the granules clearly. Stained smears from animal tissues often reveal groups of cells in parallel (Palisades) or cells at sharp angles to each other (Chinese letter or Cuneiform arrangement). This is due to the incomplete separation of the daughter cells after binary fission. Rhodococcus equi can appear as a gram-positive coccus or a rod or club shaped form arranged in clusters. It is capsulated and sometimes weakly acid fast.

The actinomycetes comprise a heterologous group of prokaryotes that have the ability to form gram positive, branching filaments of less than 1μm in d.m. The main animal pathogens in the actinomycetes are in the genera Actinomyces, Arcanobacterium, Actinobaculum, Nocardia and Dermatophilus. Nonpathogenic, prolific producers of antimicrobial substances – streptomyces are also included in Actinomycetes.
Actinomyces
Natural Habitat
The actinomyces species are present on mucous membrane of the host animal, often in the oral cavity, tonsils, and nasopharynx. The soil is the natural habitat of many actinomyces species.
History
The generic name Actinomyces was first used by Harz (1879). Boestrom (1891) isolated Actinomyces bovis. Cummins (1962) clearly demonstrated Actinomyces were bacteria and they are distinct from other branching genera.

Morphology
The organisms show considerable pleomorphism. Actinomyces species are usually long and fialmentousalthough short V, Y, and T configuration also occur. In lesions of actinomycosis, the pus contains small pale yellow granules referred as sulfur granules. The sulphur granule is composed of bacterial filaments and mineralized calcium phosphate of host origin. When the granules are crushed and gram stained, a mass of gram-positive branching filaments about 1μm in width, short rods, and cocci are evident. Around this mass, a circle of club shaped bodies with their narrow ends pointing towards
the centre-staining gram negative. Hence, called ray fungus. They are nonacid fast, non-spore forming, nonmotile, non-capsulated and do not form endospores or conidia.

Nocardia has the ability to form gram-positive, branching filaments of less than 1um in diameter. It is closely related to Corynebacterium, Mycobacterium and Rhodococcus species
History Nocard described this organism in 1888, following its isolation from a case of bovine ‘farcy’, hence the name of the type species: Nocardia farcinica.
Natural Habitat
Nocardia species are soil borne saprophytes
Morphology
They are gram-positive, obligate aerobes ability to form branching filaments. Some produce true mycelia and some strains are acid-fast. All species are nonmotile. Gram stained smears from lesions revealed gram-positive branching filaments that often show fragmentation into coccobacillary elements. The modified ZN stained smears exhibit a similar morphology but most of the filaments retain the carbol-fuchsin dye and stain red.
Cultural Characters
The Nocardia species grow very well in blood agar incubated aerobically at 370C for upto 7 days. Inoculate the suspected colonies from blood agar into Sabouraud dextrose agar (SDA) and incubated at 370C for upto 10 days.

Dermatophylaceae is a group of bacteria with mycelial filaments which divide transversely and in at least two longitudinal planes to form masses of coccoid or cuboidal cells, which characteristically become motile. They are gram positive, non acid fast, aerobic and produce aerial mycelium when their growths are stimulated by 10% CO2. Dermatophilus congolensis, Dermatophilus  dermatonomus and Dermatophilus pedis are the pathogens causing variety of skin lesions in mammals, including man. Dermatophilus congolensis causes very severe clinical disease and its infection is most common in tropical and subtropical regions.
Diseases caused by Dermatophilus species
Dermatophilus congolensis mainly affects Cattle, horses, sheep and goats, but many animal species and man can be infected.The disease has many names;
Cattle : Streptothricosis or Dermatophilosis
Horse : Skin Funk (Rain Rot, Rain Scald, Dew Poisoning), Grease heal
Sheep: Mycotic dermatitis (general infection), lumpy wool (wool- covered skin) and strawberry foot rot (skin of lower leg and coronet
Natural Habitat
Dermatophilus congolensis is the only species in the genus is thought to maintain itself in small foci of infection on a carrier animal or within scab particles in dust. It can survive in scab material for period’s upto 3 years.
History
Bovine disease was first described by Van Saceghem in 1915 in the Congo now known as Zaire in Africa.

Introduction
Escherichia coli (commonly abbreviated as E. coli) is a Gram-negative, facultative anaerobic, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms).
Escherichia coli are common inhabitants of the terminal small intestine and large intestine of mammals. They are often the most abundant facultative anaerobes in this environment. They can occasionally be isolated in association with the intestinal tract of non-mammalian animals and insects. The presence of E.coli in the environment is usually considered to reflect faecal contamination and not the ability to replicate freely outside the intestine.
Morphology
E.coli is Gram-negative, facultative anaerobic and non-sporulating. Cells are typically rod-shaped, and are about 2.0 micrometers (μm) long and 0.25- 1.0 μm in diameter, with a cell volume of 0.6–0.7 μm. It can live on a wide variety of substrates. Strains that possess flagella are motile. The flagella have a peritrichous arrangement. It is motile by peritrichous flagellae, though some strains are non-motile.Spores are not formed. Capsules and fimbriae are found in some strains.
Cultural Characteristics
Escherichia coli or E.coli cells may grow on a solid or in a liquid growth medium under a laboratory condition. Solid and liquid media may have exactly the same composition except that the solid medium contains an extra 1.5% agar. Different E.coli clones may have different properties. Colonies growing on solid media represent different clones. It is an aerobe and a facultative anaerobe. Optimal growth of E. coli occurs at 37°C (98.6°F) but some laboratory strains can multiply at temperatures of up to 49°C (120°F).

Klebsiella pneumoniae (also known as Friedlander’s bacillus) is a Gramnegative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines.
Klebsiella spp. are Gram-negative, nonmotile, usually encapsulated rod-shaped bacteria, belonging to the family Enterobacteriaceae. These bacteria produce lysine decarboxylase but not ornithine decarboxylase and are generally positive in the Voges-Proskauer test. Members of the Enterobacteriaceae family are generally facultative anaerobic, and range from 0.3 to 1.0 μm in width and 0.6
to 6.0 μm in length. Klebsiella spp. often occurs in mucoid colonies. The genus consists of 77 capsular antigens (K antigens), leading to different serogroups. Morphology of Klebsiella pneumoniae (K. pneumoniae)
• Shape – Klebsiella pneumoniae is a short, plump, straight rod shape (bacillus) bacterium.
• Size – The size of Klebsiella pneumoniae is about 1–2 μm × 0.5–0.8 μm (micrometer).
• Arrangement Of Cells – K. pneumoniae is arranged singly, in pairs, or in short chains and sometimes in clusters.
• Motility – Klebsiella pneumoniae is a non-motile bacterium.
• Flagella – K. pneumoniae is a non-flagellated bacterium.
• Spores – The Klebsiella pneumoniae is a non–sporing bacterium.
• Capsule – Capsules are present in Klebsiella pneumoniae which can easily be demonstrated using India ink preparation, appear as a clear halo in a dark background.
• Gram Staining Reaction – Klebsiella pneumoniae is a Gram -ve (Negative) bacterium.

Salmonella consists of bacilli leading to Enteric fever, Gastroenteritis, Speticaemia etc. The important member of the genus is Salmonella typhi, which causes Typhoid fever. Salmonella are of two groups;
(i) Enteric fever group consisting of typhoid & Paratyphoid bacilli exclusively or primary human parasites
(ii) Food poisoning group, which are animal parasite but may infect humans causing gastrointestinal infections Salmonella is oxidase negative, catalase positive, indole and Voges Proskauer (VP) negative, methyl red and Simmons citrate positive, H₂S producing andurea negative.
Characteristics
Cells are rod-shaped, non-spore-forming, and predominantly motile by means of peritrichous flagella with diameters of around 0.7-1.5μm and lengths of 2-5μm with a few exceptions. On blood agar, colonies are 2-3mm in diameter. Colonies are generally lactose non-fermenters. They obtain their energy from oxidation and reduction reactions using organic sources, and are facultative anaerobes. They produce acid from glucose usually with the production of gas, and are oxidase negative. Most produce hydrogen sulphide except Salmonella paratyphi A and Salmonella typhi, which is a weak producer. They are identified
with a combination of serological and biochemical tests. Salmonella species are classified and identified into serotypes according to the White-Kauffmann-Le Minor scheme; there are more than 2,500 Salmonella
serotypes that have been described and reported.

Yersinia species are non-lactose fermenters and, with the exception of Y. pestis are motile. Although there are more than 10 Yersinia species, only Y. pestis, Y. enterocolitica and Y. pseudotuberculosis are pathogenic for animals and man. Yersinia ruckeri causes perioral haemorrhagic inflammation in some species of fish. Growth of yersiniae tends to be less rapid than other members of the
Enferobacteriaceae. They characteristically demonstrate bipolar staining in Giemsa-stained smears from animal tissues
Natural Habitat
Y. pestis, the cause of bubonic plague in man and a sylvatic cycle in animals, is transmitted mainly by fleas from tolerant rodents. Human infections through cuts, bites, scratches and aerosols can also occur. Cats are susceptible to Y.pestis and naturally infected cats can pose a health hazard for humans in endemic areas. Y. pseudotuberculosis persists in wild rodents and birds as well as in the environment. The intestinal tract of wild and domestic animals appears to be the reservoir for Y. enterocolitica. Pigs, particularly, are carriers of Y. enterocolitica strains pathogenic for humans.
Isolation
Yersinia species grow on nutrient, blood and MacConkey agars but the colonies, after 24 hours incubation, tend to be smaller than those of the other members of the Enterobacteriaceae. Y. pestis grows poorly on agars containing desoxycholate whereas Y. enterocolitica and Y. pseudotuberculosis grow well on these media. Yersinia selective medium (CIN agar) containing the antibiotic supplement cefsulodin (15mg/litre), irgasin (4 mg/litre) and novobiocin (2.5 mg/litre) is designed for the isolation of Y. enrerocolitica from faeces.

The genera Proteus and Providencia belong to the tribe Proteae of the family Enterobacteriaeceae. The members of both these genera are gram negative, motile bacilli, aerobes and facultative anaerobes and can grow on basic media. A characteristic feature which distinguishes tribe Proteae from other members of Enterobactereaceae is the presence of the enzyme phenylalanine-deaminase which converts phenylalanine to phenylpyruvic acid (PPA reaction).They also produces a powerful urease enzyme which rapidly hydrolyses urea to ammonia.
Genus Proteus
They are gram-negative bacilli, 1-3 μm long and 0.6 μm wide. They are noncapsulated and are actively motile by peritrichous flagella. The name ‘Proteus’ refers to their pleomorphism, after the Greek God Proteus who could assume any shape. Four species: Proteus mirabilis, P.vulgaris, P.penneri and P.myxofaciens are recognized. Proteus mirabilis, P.vulgaris are widely recognised as human pathogens.
Culture Characteristics
These can grow on ordinary media like nutrient agar with a characteristic fishy or seminal odour. On MacConkey and Teepol lactose agar, lactose nonfermenting pale colonies, around 2-3 mm in size are formed. On non-inhibitory solid media such as blood and nutrient agar Proteus mirabilis and P vulgaris show characteristic swarming growth in the form of a uniform film, which spreads over the whole surface of the plate. In young swarming cultures, many of the bacteria are long, curved and filamentous, sometimes reaching upto 80 μm in length. When two different strains of swarming proteus mirabilis encounter one another on an agar plate, swarming ceases and a visibile line of demarcation forms. This is known as the Dienes phenomenon. In liquid medium (peptone water, nutrient broth), Proteus produces uniform
turbidity with a slight powdery deposit and an ammoniacal odour.

History
Pseudomonas is comprised of two Greek words-Pseudo meaning false and Monas meaning unit, so literally the term means “false unit”. However Pseudomonas is a real bacteria so we really do not know the basis of the nomenclature by Walter Migula. A scientist by the name of Migula gave the Genus name of Pseudomonas in 1894 to these bacteria. Classification
The classification of Pseudomonas is given below:
• Class : Gamma Proteobacteria
• Order : Pseudomonadales
• Family : Pseudomonadaceae
• Genus : Pseudomonas
• Eight groups : P. aeruginosa ; P. chlororaphis; P. fluorescens;
P.pertucinogena; P.putida; P. stutzeri; P. syringae; P.
incertae sedis.
The family has 191 valid species. These include bacteria which are saprophytic, free living, and human, animal and plant pathogens. The type species is Pseudomonas aeruginosa.
Usual Habitat
Pseudomonas species are environmental organisms which occur worldwide in water and soil, and on plants. Pseudomonas aeruginasa is also found on the skin, on mucous membranes and in faeces. Burkholderia pseudomallei, which is found in soils, occasionally infectsanimals and man. Wild rodents can act as reservoirs of this organism. It is widely distributed in some tropical and subtropical regions of Southeast Asia and Australia.Although B.mallei can survive in the environment for upto 6 weeks its reservoir is infected Equidae.

Pasteurella and Mannheimia species are small (0.2 x 1-2 μm) non-motile, Gramnegative rods or coccobacilli. They are oxidase-positive facultative anaerobes, and most species are catalase-positive. Although non-enriched media will support their growth, these organisms grow best on media supplemented with blood or serum. They usually remain viable for only a few days on culture plates.
Some species, such as Mannheimia haemolytica, Pasteurella trehalosi and P. aerogenes can tolerate the bile salts in MacConkey agar. In smears from infected tissues stained by the Giemsa method, pasteurellae exhibit bipolar staining.
The family Pasteurellaceae comprises five genera, Actinobacillus, Haemophilus, Mannheimia, Pasteurella and Lonepinella. These genera share a number of common features and some organisms have been reclassified within these genera following deoxyribonucleic acid hybridization studies and 16s rRNA sequencing.
The pasteurellae are small (0. 2 μm by up to 2.0 μm), Gram-negative rods or coccobacilli. They are nonmotile,non-sporing, facultatively anaerobic, fermentative(except for P. anatipesrijer), oxidase-positive andcatalase - positive (except for P. caballi). Althoughunenriched media support their growth, they grow beston media supplemented with serum or blood.
Recent Changes in Nomenclature
Previous name Present name
Pasteurella ureae Actinobacillus ureae
Haemophilus avium Pasteurella avium
Pasteurella pneumotropica Pasteurella dogmatis
(Henriksen biotype)

Actinobacillus species are non-motile, Gram-negative rods (0.3 to 0.5 x 0.6 to 1.4 μm) which occasionally have a coccobacillary appearance. They are non-motile, non-sporeformingand non-acid-fast. A surface slime is presentin the three major species (A. ligllieresii. A. equuli andA. suis) and may be related to the stickiness of theircolonies on agar. Surface cultures have low viabilityand die in 5-7 days. The actinobacilli ferment carbohydrates, without the production of gas, within 24 hours and most species produce urease and grow on MacConkey agar. Most species are urease and oxidase positive. The
reactions in the oxidase andcatalase tests are variable. The genus is still in a stateof flux, mainly because of the close similaritiesbetween actinobacilli and species in the genera Pasteurella and Haemophilus.
These facultative anaerobes ferment carbohydrates producing acid but not gas. Actinobacilli exhibit some host specificity and are mainly pathogens of farm animals.
Usual Habitat
Actinobacilli are commensals on mucous membranes of animals particularly in the upper respiratory tract and oral cavity. As actinobacilli cannot survive for long in the environment, carrier animals play a major role in transmission.
Colonial Appearance
• A. lignieresii: small, glistening colonies develop in 24 hours. They are usually slightly sticky (viscid) on primary isolation but lose th is characteristic on subculture. The colonies are non-haemolytic and develop to about 2 mm in diameter in 48 hours. The organism grows well on MacConkey agar, the colonies are at first pale but become pinkish as A. lignieresii is a late lactose-fermemer.
• A. equuli: some strains are haemolytic and the colonies are sticky with this feature remaining on subculture. I t is a lactose-fermenter onMacConkey agar.

Introduction
The genus Haemophilus contains small, nonmotile, nonsporing, oxidase positive, pleomorphic, gram negative bacilli that are parasitic on human beings or animals. Haemophilus means blood loving organisms.

Haemophilus species are small (less than 1 pm x 1 to 3 μm), Gram-negative rods, which often appear coccobacillary and may occasionally form short filaments. These motile organisms, which are facultative anaerobes with variable reactions in catalase and oxidase tests, do not grow on MacConkey agar. They are fastidious bacteria requiring one or both of the growth factors X (haemin) and V (nicotinamide adenine dinucleotide, NAD). Optimal growth occurs in an atmosphere of 5-10% CO2 on chocolate agar which supplies both X and V factors. Small, transparent, dewdrop-like colonies are formed by most Haemophilus species after incubation for 48 hours.

Colonies of H.somnus have a yellowish hue and some isolates are haemolytic on sheep blood agar. The main pathogens in the genus are H.somnus in cattle and sheep, H.parasuis in pigs and H.paragallinarum which is responsible for infectious coryza of chickens.

The haemophili are motile, facultative anaerobes, produce acid from glucose, reduce nitrates and are variable in the oxidase and catalase tests. They are nutritionally fastidious, will not grow on MacConkey agar and grow best on chocolate agar (supplying the X and V factors) under 5- 10 per cent CO2 at 37°C.

The growth of many of the Haemaphilus species is enhanced by 10 per cent CO2, As this is not inhibitory for any of them, CO2 should be used for routine isolation.The inoculated chocolate agar plates are incubated under 10 per cent CO2 at 35-37°C for 3-4 days, although some growth may be seen after 24 hours.

Brucella species are small (0.6 x 0.6 to 1.5 pm), nonmotile, coccobacillary, Gram-negative bacteria. As they are not decolourized by 0.5% acetic acid in the modified Ziehl-Neelsen (MZN) staining technique, they are classed as MZN-positive. In MZN-stained smears of body fluids or tissues, they characteristically appear as clusters of red coccobacilli. For taxonomic purposes, all Brucella species should be classified as Brucella melitensis as DNA hybridization studies have shown that the genus contains only one species.
Brucella species are aerobic, capnophilic and catalase-positive. Apart from B.ovis and B.neotomae, they are oxidase-positive. All Brucella species are urease-positive except B.ovis. Brucella ovis and some biotypes of B.abortus require 5 to 10% CO2 for primary isolation. Moreover, the growth of other Brucella species is enhanced in an atmosphere of CO2. Media enriched with blood or serum is required for culturing B.abortus biotype 2 and B.ovis. Recently, brucellae have been detected in sea-mammals. Smears are made from specimens and stained by the modified Ziehl- Neelsen (MZN) stain. Brucellae appear as small, red-staining coccobacilli in clumps because of their intracellular growth.
Isolation
The brucellae grow well on 5-10 per cent blood agar. However, other than foetal abomasal contents and colostrum, the specimens are likely to contain many contaminating bacteria and fungi, so selective media are usually required. The selective media contain a nutritive blood agar base with 5 per cent sterile seronegative equine or bovine serum and an antibiotic supplement. The antibiotic
supplement used in selective media for B.ovis usually differs from that for B. abortus. Skirrow agar is a satisfactorymedium for both the Campylobacter fetus subspecies and for brucellae, including the most fastidious species such as B. abortus biotype 2, B.canis and B.ovis.

Introduction
Vibrios are Gram-negative, rigid, curved rods that are actively motile by means of a polar flagellum. The name ‘Vibrio’ is derived from the characteristic vibratory motility (from vibrare, meaning to vibrate). They are asporogenous and noncapsulated. Vibrios are present in marine environments and surface waters worldwide. The most important member of the genus is Vibrio cholerae, the causative agent of cholera. It was first isolated by Koch (1883) from cholera patients in Egypt, though it has been observed earlier by Pacini (1884) and others.
Natural Habitat
Vibrio spp. can be present in both freshwater and seawater as well as in the alimentary tracts of animals and man. At least five Vibrio spp. are human pathogens including V. cholerae, the cholera bacillus, and V.parahaemolyticus which causes food poisoning. Only V. metschnikovii is associated with disease in domestic animals. It causes a cholera-like disease in chickens and other birds but its geographical distribution is very limited. V. anguillarum causes infections in many species of fish especially in salt or brackish water. It causes high mortality in salt water eels.
Vibrio Cholerae
Morphology
The cholera vibrio is a short, curved, cylindrical rod, about 1.5 × 0.2-0.4 mm in size, with rounded or slightly pointed ends. The cell is typically comma shaped (hence the old name V comma) but the curvature is often lost on subculture. S-shaped or spiral form may be seen due to two or more cells lying end to end. Pleomorphism is frequent in old cultures. In stained films of mucus flakes from acute cholera cases, the vibrios are seen arranged in parallel rows,

Campylobacter species are slender, curved motile Gram negative rods (0.2 to 0.5 pm wide) with polar flagella. Daughter cells which remain joined have a characteristic gull-winged appearance and long spirals formed by joined cells also occur. These microaerophilic organisms grow best on enriched media in an atmosphere of increased CO2 and decreased oxygen tension. Many Campylobacter species grow on MacConkey agar. They are non-fermentative and oxidase-positive and have variable catalase reactions.
Usual Habitat
Many Campylobacter species are commensals in the intestinal tracts of warm-blooded animals. Campylobacter jejuni and C. lari (formerly C. laridis) colonize the intestines of birds, which can result in faecal contamination of water courses and stored food. A number of Campylobacter species are excreted in the faeces of pigs. Campylobacter fetus subspecies venerealis appears to be adapted principally to bovine preputial mucosa.
Differentiation of Campylobacter Species
Campylobacter species are strictly microaerophilic, requiring an atmosphere of 5 to 10% oxygen and 1 to 10% CO2 for growth. A selective enriched medium such as Skirrow agar is usually used for primary isolation. Differentiation of isolates is based on colonial morphology and certain cultural, biochemical and antibiotic-susceptibility characteristics.
Colonial Morphology
• Campylobacter fetus subspecies venerealis and C.fetus subspecies fetus have small, round, smooth, translucent colonies with a dewdrop appearance.
• Campylobacter jejuni produces small, flat, grey colonies with a spreading, watery appearance.

to be coccobacillary.They are strict aerobes and do not attack carbohydratesbut derive energy by the oxidation of amino acids. B. avium and B. bronchiseptica are motile by peritricholls flagella but B. pertussis and B. parapertussis are non-motile. All are catalase-positive and oxidase-positive. B. bronchiseptica and B. aium willgrow on MacConkey agar.
The genus Bordetella contains four species, B.pertussis, B.parapertussis, B. bronchiseptica and B. avium. Bordetella pertussis, the type species, and B.parapertussis are human pathogens associated with whooping cough in children. Bordetella bronchiseptica infects a wide range of animal species including man, while B.avium is a pathogen of avian species. The bordetellae are occasional pathogens which have an affinity for ciliated respiratory epithelium.
Bordetella bronchiseptica and B.avium are small (0.2 to 0.5 x 0.5 to 1.5 pm), Gramnegative rods with a coccobacillary appearance. They are catalasepositive, oxidase-positive aerobes and are motile peritrichous bacteria. Because they cannot utilize carbohydrates, they derive their energy mainly from the oxidation of amino acids and have no special growth requirements. They grow on MacConkey agar.
Natural Habitat
The bordetellae are inhabitants primarily of the upper respiratory tract of healthy and diseased humans, animals and birds. B. pertussis and B. parapertussis are human pathogens causing whooping cough and a mild form of whooping cough, respectively. B. bronchiseptica can be present in the upper respiratory tract of pigs, dogs, cats, rabbits, guinea-pigs, rats, horses and possibly other animals. B. avium inhabits the respiratory tract of infected poultry, principally turkeys. Mammalian infections are mainly transmitted by aerosols but in turkeys indirect spread can occur via water and litter.