LESSON 4

Question 1

 Gram-positive, pleomorphic bacteria
 Fastidious, requiring enriched media
 Occur singly, in palisades of parallel cells and in angular clusters resembling Chinese characters in stained smears
Fig. 1 Characteristic pleomorphism of
corynebacteria showing their
typical arrangement in stained smears.
 Majority are commensals on mucous membranes
 Cause pyogenic infections
 non-motile facultative anaerobes
 catalase-positive, oxidase negative
 usual habitat: mucous membranes
 Identification criteria: o Morphology
o Colonial characteristics o Biochemical reactions

Answer 1

Lesson 4a: Corynebacterium species

Question 2

Table 1 The pathogenic corynebacteria, their hosts, usual habitats and the disease conditions which they produce.
Pathogen -Host -Disease condition- Usual habitat

Question 3

Corynebacterium bovis - Cattle

Answer 3

Subclinical mastitis -Teat cistern

Question 4

C. diptheriae Humans?
Horses?

Answer 4

Diptheria
Wound infection

Question 5

C. kutscheri—— Lab. Rodents

Answer 5

Abscess, foci in liver, lungs and lymphnodes

Mucous membrane, Environment

Question 6

C. pseudotubercolusis
Non-nitrate reducing biotype Sheep, goats
nitrate reducing biotype Horses, cattle

Answer 6

Caseous lymphadenitis Skin, Mucous membrane,
Environment

Ulcerative lymphagitis, abscess Environment

Question 7

C. renale group
C. renale (type
I)
Cattle
Sheep and goats
C. pilosum
(type II)
Cattle
C. cystidis
(type III)
Cattle

Answer 7

Cattle —-Cystitis, pyelonephritis—– Lower urogenital tracts of cows and bulls

Sheep and Goat—-Ulcerativebalanoposthitis —-Prepuce

Cattle—Cystitis, pyelonephritis —-Bovine urogenital tract

Cattle—–Severe cystitis, pyelonephritis——- Bovine urogenital tract

Question 8

C. ulcerans
Cattle
Cats
Humans

Answer 8

Mastitis
Upper respiratory tract infection
Diptheria

Question 9

Table 2 Differentiation of bacteria in the Corynebacterium renale group.
Feature C. renale (type I) C. pilosum (type II) C. cystidis (type III)
Page

Answer 9

32

Question 10

 Most are opportunistic pathogens and pyogenic except

Answer 10

C. bovis.

Question 11

______________ is a facultative intracellular pathogen capable of surviving and replicating in phagocytes whose virulence is linked to its cell wall lipid and to the production of an exotoxin, phospholipase D (PLD) that enhances its survival and multiplication in the host.

Answer 11

C. pseudotuberculosis

Question 12

 _______ from C. ulcerans and C. pseudotuberculosis present in raw milk cows may implicate public health.

Answer 12

Diptheria toxin

Question 13

 Clinical signs are suggestive of diagnosis
 Specimens suitable for laboratory procedures include pus, exudates, tissue samples for culture and histopathology and mid-stream urine.
 Gram-staining
 Isolation and identification of bacteria from cell culture on blood agar, selective blood agar and MacConkey agar at 37°C for 1 to 2 days.
 Identification criteria for isolates:
 Colonial characteristics
 Morphology in stained smears
 Presence or absence of haemolysis on blood agar
 Absence of growth on MacConkey agar
 Enhancement of haemolysis test for C. pseudotuberculosis
 Molecular detection through PCR

Answer 13

Corynebacterium species

Question 14

: caused by the non-nitrate-reducing biotype of C. pseudotuberculosis in goats, sheep and cattle (rare). Manifestations: chronic supporative conditions, encapsulated abscess formation which have an ‘onion ring’ appearance in cross-section, enlargement of lymph nodes thus results in condemnation of carcasses and devaluation of hides.

Answer 14

Caseous lymphadenitis

Question 15

________________ has been isolated from the milk of affected goats thus posing a threat to public. Sheep become infected through contamination of shearing wounds, by arthropod bites or from contaminated dips. Dx: clinical lesions, Gram-staining, Bacterial culture from abscess swab samples, or detection antibodies by ELISA. Tx: no effective tx. Control: strict border control, heightened biosecurity, or culling.

Answer 15

 Corynebacterium pseudotuberculosis

Question 16

: caused by the nitrate-reducing biotype of C. pseudotuberculosis in horses and cattle. Prevalent in countries with temperate weather.

Answer 16

Ulcerative lymphangitis

Question 17

: caused by C. renale group. The stress of parturition and the short urethra in the cow predispose to infection of the urinary tract. Clinical signs of pyelonephritis include fever, anorexia and decreased milk production. Dx: rectal palpation (unilateral thickened ureter/enlarged kidneys) bacterial culure from urine sample, presence of rbc or protein in urine. Tx: penicillin

Answer 17

 Bovine pyelonephritis

Question 18

: also called pizzle rot common in Merino sheep and Angora goats, is caused by C. renale and is characterized by ulceration around the preputial orifice (or vulva in ewes), with a brownish crust developing over the lesion.

Answer 18

 Ulcerative balanoposthitis

Question 19

 Formerly named Corynebacterium equi
 Gram-positive rods or cocci, aerobic, soil saprophyte, worldwide distribution
 Oppurtunistic intracellular pathogen (foal under 6 months old)
Fig. 2 Cocci and rods, the two distinct morphological forms of Rhodococcus equi.
 Non-motile, catalase-positive, oxidase-negative and weakly acid-fast
 oxidation-fermentation test and in sugar fermentation tests negative
 CAMP-test positive
 Together with Nocardia sp and Mycobacterium sp they form Actinomycetales
 Respiratory pathogen of foal (under 6 mos old)

Answer 19

Rhodococcus equi

Question 20

Foals 1 to 4 months of age

Answer 20

Suppurative bronchopneumonia and pulmonary abscessation

Question 21

Rhodococcus equi.
Host Clinical condition

Horses?

Answer 21

Superficial abscessation

Question 22

Rhodococcus equi.
Host Clinical condition

Pigs, cattle

Answer 22

Mild cervical lymphadenopathy

Question 23

Rhodococcus equi.
Host Clinical condition
Cats

Answer 23

Subcutaneous abscesses, mediastinal granulomas

Question 24

Rhodococcus equi.
Host Clinical condition

Immunosuppressed humans

Answer 24

Pneumonia

Question 25

bronchopneumonia and lung abscessation in foals under 6 months of age. Epidemiology: Infection by inhalation of contaminated dust or ingestion (sputum) of large numbers of R. equi result to infection granulomatous ulcerative enterocolitis and mesenteric lymphadenitis. Source of contamination include faeces of horse, mammals and even birds. Predisposing factors: dry weather, low humidity, high animal density. Pathogenecity: The virulence of R. equi, is principally associated with a large plasmid which contains genes that encode most importantly vapA protein that can be used as epidemiological marker. Other virulence factors include capsular polysaccharides and mycolic acids in the cell wall which retard phagocytosis, and also a variety of exoenzymes. Clinical signs include fever, anorexia and signs of bronchopneumonia. Dx: farm history, pulmonary ultrasonography, cytology of respiratory secretions, bacterial culture (blood agar and MacConkey agar-no growth in MacConkey) . Tx: oral rifampin and macrolide combination.

Answer 25

Suppurative bronchopneumonia of foals

Question 26

 Aesculin hydrolysed
 Most are small, Gram-positive, coccobacillary rods, up to 2 μm in length
 Catalase-positive, oxidase-negative, motile, facultative anaerobes
 Environmental saprophytes (Herbage, faeces of healthy animals, sewage effluent and bodies of fresh water, can replicate in the environment).
 Grow on non-enriched media
 Tolerate wide temperature and pH ranges
 Small haemolytic colonies on blood agar
 Tumbling motility at 25°C
 Aesculin hydrolysed

Fig. 3 The typical coccobacillary form of Listeria monocytogenes from an actively growing culture.

 Outbreaks of listeriosis often related to silage feeding
 Pathogenicity associated with intracellular replication

Answer 26

Listeria species

Question 27

Listeria species in domestic animals.
Species Host Form of disease
Page36

Question 28

Table 5 Laboratory methods for differentiating Listeria species.
Listeria species Haemolysis on sheep blood agar CAMP test Acid production from sugars

Answer 28

36-37

Question 29

Ingestion of feed contaminated with____________ result to septicaemia, encephalitis or abortion.

Answer 29

L. monocytogenes

Question 30

 In pregnant animals, infection results in transplacental transmission.

Answer 30

Listeria species

Question 31

 It is thought that the organism may penetrate via the dental pulp when sheep are cutting or losing teeth. From this site, migration in cranial nerves is thought to be the main route of infection in neural listeriosis.

Answer 31

Listeria species

Question 32

_______ has the ability to invade both phagocytic and non- phagocytic cells, to survive and replicate intracellularly and to transfer from cell to cell without exposure to humoral defence mechanisms.

Answer 32

 L. monocytogenes

Question 33

 The action of a its cytolytic toxin, listeriolysin, and a phospholipase enzyme destroys the membranes of phagocytic vacuoles allowing Listeria to escape into the cytoplasm. In the cytoplasm, an actin-polymerizing protein, ActA, produced by the organism, directs the formation of tail-like structures from host cellular microfilaments which aid the motility of the invading pathogens thereby inducing pseudopod-like projections which are taken up by adjacent cells and replicate infection.

Question 34

 Another way of ___________ to survive within the hosts cell is by inhibiting cell autophagy.

Answer 34

L. monocytogenes

Question 35

is present as encephalitis, abortion, septicaemia or endophthalmitis in ruminants. Clinical signs: for neural listeriosis (14-40 days) are dullness, circling and tilting of the head, unilateral facial paralysis. While septicaemic listeriosis only has 2-3 days incubation period. Tx: ampicillin, amoxicillin, or in combination with aminoglycosides.
Fig. 1 Filaments of
Erysipelothrix rhusiopathiae from a
chronic lesion, showing morphological variation.

Answer 35

Bovine Listeriosis