bacte 2 corynebacterium, listeria, Erysipelothrix

Describe the Gram reaction, shape, and characteristic arrangement of Corynebacterium species in stained smears

Reaction: Gram-positive. Shape: Small and pleomorphic (coccoid, club, and rod forms).Arrangement: Single, palisades (parallel), or angular clusters resembling Chinese characters.

"hich four genera make up the ""CMN group,"" and what are two shared chemical characteristics of this group?"

Genera: Corynebacterium, Mycobacterium, Nocardia, and Rhodococcus. Characteristics: High G + C content and cell walls containing mycolic acids.

How do the mycolic acids of Corynebacterium differ from those of other genera in the CMN group (e.g., Mycobacterium)

They are shorter and the carbon chains are usually saturated.

What are the four primary biochemical/growth characteristics of most Corynebacterium species? (catalase, oxidase, spore, O2)

1. Catalase-positive 2. Oxidase-negative 3. Non-spore-forming 4. Facultative anaerobes (requiring enriched media for growth)

1. Are pathogenic Corynebacterium species motile or non-motile? 2. What physical event usually precedes infection, and what is the characteristic of the resulting lesion?

1. Non-motile. 2. Tissue trauma precedes infection; lesions are characterized by suppuration (pus formation)

1. Where are most Corynebacterium species found in the body? 2. Which specific species is known for surviving months in the environment

1. Commensals on mucous membranes. 2. Corynebacterium pseudotuberculosis (formerly C. ovis

1. What unique growth requirement does C. bovis have? 2. Describe its colonial appearance on milk samples

1. It is lipophilic (requires lipids for optimal growth). 2. Produces small, white, dry, non-haemolytic colonies

Describe the progression of C. pseudotuberculosis colonies over several days

Early (up to 72h): Small, whitish with a narrow zone of complete haemolysis. Late: Become dry, crumbly, and cream-coloured.

How are the two biotypes of C. pseudotuberculosis differentiated biochemically and by host species?

Ovine/Caprine strains: Nitrate-negative (lack nitrate-reducing capacity). Equine/Bovine strains: Nitrate-positive (usually reduce nitrate)

what is a key differentiating feature used to distinguish the three species within the C. renale group after 48 hours of incubation?

Pigment production. (They start as small, non-haemolytic colonies at 24 hours).

Which pathogenic Corynebacterium species is the exception to the rule that all pathogenic corynebacteria produce urease?

Corynebacterium bovis

How is the haemolysis of C. pseudotuberculosis enhanced for identification purposes

By inoculating the organism across a streak of Rhodococcus equi

What is the primary pathological characteristic of most Corynebacterium species (except C. bovis)?

They are pyogenic (pus-forming) organisms that cause variety of suppurative conditions in domestic animals

1. Where is C. bovis typically found in dairy cows? 2. What is the hypothesized benefit of the mild neutrophil response it provokes?

1. In the teat canal (found in up to 20% of healthy cows). 2. It may protect the mammary gland against invasion by more virulent pathogens

How is C. pseudotuberculosis classified in terms of its relationship with host cells?

It is a facultative intracellular pathogen, capable of surviving and replicating inside phagocytes (macrophages)

1. What is the primary exotoxin produced by C. pseudotuberculosis? 2. What is its mechanism of action on host cells?

1. Phospholipase D (PLD). 2. It hydrolyses sphingomyelin in mammalian cell membranes, releasing choline. This enhances the survival and multiplication of the bacteria

What is CP40, and why is it considered a significant protective antigen in C. pseudotuberculosis?

It is corynebacterial secreted protease 40. It is a major virulence factor; immunization against CP40 provides considerable protection against infection

Under what specific condition can C. ulcerans and C. pseudotuberculosis produce diphtheria toxin?

When they are lysogenized by corynephage beta (which carries the tox gene). This is a public health concern when found in raw milk

explain the role of corynephage beta in causing diphtheria

Lysogenic Conversion: When a corynephage β infects C. diphtheriae, it doesn't immediately kill the cell but inserts its DNA (including the tox gene) into the bacterial genome, becoming a prophage.Toxin Production: This integration makes the bacterium toxigenic, allowing it to produce diphtheria toxin, a key factor in the disease's severity.Gene Transfer: The beta phage acts as a vector, spreading the tox gene between C. diphtheriae and other related bacteria like C. ulcerans.

What are the two primary virulence factors used by the C. renale group to cause cystitis and pyelonephritis?

1. Fimbriae: For attachment to the urogenital mucosa. 2. Urease: To hydrolyse urea, which contributes to tissue damage in the urinary tract

What are the four main types of specimens suitable for the laboratory diagnosis of Corynebacterium infections

1. Pus 2. Exudate 3. Affected tissue 4. Mid-stream urine (specifically for the C. renale group)

What should you look for in a direct Gram-stained smear of a specimen when suspecting Corynebacterium?

"Coryneform organisms (Gram-positive, pleomorphic bacteria in palisades or angular ""Chinese character"" arrangements)"

What are the routine culture media and incubation requirements for Corynebacterium isolates?

media: Blood agar, selective blood agar, and MacConkey agar.Temperature: 37°C.Atmosphere: Aerobic.Time: 24 to 48 hours.

True or False: Corynebacterium species typically show robust growth on MacConkey agar.

False. The absence of growth on MacConkey agar is a key identification criterion for this genus.

Which specific test is used to identify C. pseudotuberculosis by demonstrating the interaction between toxins?

The Enhancement of Haemolysis Test (Synergistic hemolysis). The zone of hemolysis is enhanced when C. pseudotuberculosis is grown in the presence of Rhodococcus equi.

What molecular technique can be used for the direct detection of C. pseudotuberculosis in pus specimens without waiting for culture?

Multiplex PCR

Which specific biotype of C. pseudotuberculosis causes Caseous Lymphadenitis, and which species are primarily affected?

The non-nitrate reducing biotype (Ovine/Caprine biotype). It primarily affects sheep and goats, and rarely cattle

causes Caseous Lymphadenitis

C. pseudotuberculosis

Describe the characteristic appearance of a chronic C. pseudotuberculosis lymph node abscess in cross-section.

"It exhibits encapsulated abscesses with a distinctive ""onion ring"" appearance (concentric layers of fibrous tissue and pus)"

How does the consistency and color of the caseous material in Caseous Lymphadenitis (CLA) change over time?

The material is caseous (cheesy). It is initially greenish and later becomes putty-coloured

What are the three main ways sheep become infected with C. pseudotuberculosis?

1. Contamination of shearing wounds. 2. Arthropod bites. 3. Contaminated dips. (Note: Spread also occurs via pus from ruptured abscesses or nasal/oral secretions).

"Differentiate between the ""superficial"" and ""visceral"" forms of Caseous Lymphadenitis"

Superficial: Enlargement of external lymph nodes (common in goats, head/neck). Visceral: Haematogenous spread to internal lymph nodes/organs; often results in ill-thrift and pneumonia (may not be detectable ante-mortem)

Why do goats typically develop abscesses in the head/neck while sheep lesions are more widespread?

Due to behavior and management: Goats: Head-butting and grooming behaviors. Sheep: Related to shearing practices and wounds over the body.

Caseous Lymphadenitis incubation period

~3 months.

What are the two primary targets for antibodies in the ELISAs used to detect C. pseudotuberculosis?

1. Cell wall antigens. 2. Phospholipase D (PLD) (the exotoxin). (Note: The PLD-based sandwich ELISA is highly specific at 99%)

Which cytokine-based test shows promise for the eradication of CLA in sheep flocks?

The Interferon-gamma (IFN-gamma) test

Why is antibiotic therapy for CLA usually ineffective, despite the bacteria being susceptible in vitro?

1. The chronic, encapsulated nature of the lesions (poor drug penetration). 2. The ability of the organism to survive intracellularly

Which biotype of C. pseudotuberculosis causes Ulcerative Lymphangitis, and how does it differ from the one causing Caseous Lymphadenitis?

The nitrate-reducing biotype (Equine/Bovine biotype). (Note: Caseous Lymphadenitis in sheep/goats is caused by the non-nitrate reducing biotype)

1. How is Ulcerative Lymphangitis transmitted to horses and cattle? 2. When is the peak incidence in the USA

1. Skin wounds, arthropod bites (specifically houseflies), or contaminated harnesses. 2. Autumn and early winter.

What are the two primary clinical forms of C. pseudotuberculosis infection in horses?

"1. Lymphangitis of the lower limbs: Swollen, firm lymphatics with nodules and edema. 2. Pectoral abscesses: (Sometimes called ""Pigeon Fever"")"

Beyond lymphangitis, what are two less common clinical syndromes caused by nitrate-reducing biotype of C. pseudotuberculosis in dairy cattle?

1. Mastitis. 2. Coronary band lesions (leading to lameness)

Why is laboratory isolation and identification essential for a definitive diagnosis of ulcerative lymphangitis?

Because lymphangitis can also be caused by other pyogenic bacteria; clinical signs alone are not pathognomonic

What is the recommended treatment protocol for an animal with Ulcerative Lymphangitis?

1. Systemic antibiotic therapy. 2. Topical treatment (e.g., iodophor shampoos). 3. Isolation of affected animals and disinfection of the environment

What are the three primary reasons cows are predisposed to ascending urinary tract infections by the C. renale group

1. Stress of parturition (calving). 2. Short urethra (shorter distance for bacteria to travel). 3. Anatomical presence: Organisms are commensals in the vulva and vagina

Beyond fever and decreased milk production, what are the characteristic signs of renal pain and urinary involvement in bovine pyelonephritis?

Renal Pain: Restlessness, kicking at the abdomen, and an arched back. Urinary Signs: Dysuria (painful urination) and blood-tinged urine.

"1. Why is Penicillin particularly effective for C. renale group infections? 2. What is the ""treatment of choice"" for severe unilateral cases?"

1. Because penicillin is excreted in the urine, reaching high concentrations at the site of infection. 2. Unilateral nephrectomy (surgical removal of the affected kidney)

"1. What is the formal name for ""Pizzle Rot""? 2. How does C. renale cause the characteristic mucosal irritation and ulceration?"

1. Ulcerative (enzootic) balanoposthitis. 2. It produces urease, which hydrolyses urea into ammonia; the ammonia acts as a chemical irritant to the mucosa.

What nutritional factor and what environmental factor increase the risk of Pizzle Rot in sheep and goats?

Nutrition: High protein intake, which leads to high urinary urea levels. Environment/Management: Heavy wool/mohair cover around the prepuce and pastures with high oestrogen levels.

1. What are the early visual signs of Pizzle Rot? 2. What is a serious complication of untreated cases?

1. Ulceration around the preputial orifice with a brownish crust. 2. Total occlusion of the preputial orifice

pizzle rot

Ulcerative (enzootic) balanoposthitis caused by C. renale

Describe the Gram reaction, shape, and size of Listeria species

Gram Reaction: Gram-positive. Shape: Coccobacillary rods (small). Size: Up to 2um in length.

What are the five primary biochemical and physical characteristics of the genus Listeria? (catalase, oxidase, motility, O2, temp)

1. Catalase-positive 2. Oxidase-negative 3. Motile 4. Facultative anaerobe 5. Psychrotrophic (can grow at 4°C)

What are the temperature and pH ranges that Listeria monocytogenes can tolerate?

Temperature: 4°C to 45°C. pH: 5.5 to 9.6

1. Which Listeria species is the most important pathogen for humans and animals? 2. Which species is mainly a pathogen of ruminants (but less frequent)?

1. Listeria monocytogenes. 2. Listeria ivanovii. (Note: L. innocua is usually non-pathogenic but rarely found in sheep meningoencephalitis)

Where is Listeria found in the environment, and can it replicate outside of a host?

Yes, it replicates in the environment. It is widely distributed in: Herbage (grass/silage). Faeces of healthy animals. Sewage effluent. Fresh water.

What three laboratory methods are used to differentiate Listeria species?

1. Haemolysis pattern (on sheep blood agar). 2. CAMP tests. 3. Acid production from sugars

Describe the appearance of Listeria colonies after 24 hours of incubation.

Small, smooth, and transparent

"1. How many serotypes of L. monocytogenes exist? 2. What is the molecular ""gold standard"" used by CDC PulseNet for strain typing?"

1. 13 serotypes (based on cell wall and flagellar antigens). 2. PFGE (Pulsed-Field Gel Electrophoresis) after restriction endonuclease digestion.

Internalins

Surface proteins that facilitate adherence and entry into host epithelial cells

Surface proteins that facilitate adherence and entry into host epithelial cells

Internalins

Listeriolysin O (LLO)

A cytolytic toxin that destroys the phagosome membrane, allowing Listeria to escape into the cytoplasm

A cytolytic toxin that destroys the phagosome membrane, allowing Listeria to escape into the cytoplasm

Listeriolysin O (LLO)

ActA

"An actin-polymerizing protein that creates ""tails"" from host microfilaments to provide motility"

"An actin-polymerizing protein that creates ""tails"" from host microfilaments to provide motility"

ActA

Phospholipase

An enzyme that works with LLO to break down host cell membranes during escape.

An enzyme that works with LLO to break down host cell membranes during escape.

Phospholipase

How does Listeria enter macrophages

Receptors on the macrophage recognize lipoteichoic acid in the Listeria Gram-positive cell wall

How does Listeria avoid being digested by the phagolysosome?

It escapes the phagosome before it can mature and fuse with a lysosome

How does Listeria replicate so efficiently inside the host?

It expresses specific genes that allow it to utilize host cell nutrients for growth

What structure allows Listeria to move from one cell to the next?

Pseudopod-like projections (protrusions) that are pushed into and swallowed by adjacent cells.

"What is the main advantage of ""cell-to-cell"" transfer?"

It allows the bacteria to spread without being exposed to humoral defense mechanisms (like antibodies).

What is Autophagy in the context of infection?

A host process that degrades and recycles cellular components; it acts as a defense to digest intracellular pathogens

How does Listeria counter autophagy?

"It has evolved mechanisms to inhibit autophagy, preventing the cell from ""eating"" the bacteria while it is in the cytoplasm."

Which species is primarily linked to sporadic abortions in sheep/cattle?

L. ivanovii

"Why is ""poor-quality"" silage a risk factor for Listeria?"

It has a pH above 5.5, allowing the bacteria to replicate (up to $10^7$ CFU/kg).

"Why does ""good-quality"" silage inhibit Listeria?"

Acid produced by fermentation lowers the pH, inhibiting multiplication.

Neural Listeriosis

"caused by Listeria monocytogenes Also known as ""Circling Disease""; characterized by dullness, head tilting, and circling."

"caused by Listeria monocytogenes Also known as ""Circling Disease""; characterized by dullness, head tilting, and circling."

Neural Listeriosis

incubation period of neural listeriosis

14 to 40 days

incubation period of Septicaemic listeriosis

2 to 3 days

incubation period of abortion caused by listeriosis

12 days

How does the duration of neural listeriosis differ between species

Sheep/goats: Rapid death (within days); Cattle: Usually a longer duration of illness.

Which specific brain regions should be sampled for Listeria?

The Medulla and Pons.

What are the three primary specimens to collect? (abortion from listeriosis)

1. Cotyledons, 2. Fetal abomasal contents, 3. Uterine discharges

What are the two hallmark lesions seen in the brain stem? (listeriosis)

Microabscesses and heavy perivascular mononuclear cuffing.

What white cell and protein levels suggest neural listeriosis?

WBCs > 1.2 × 10⁷/L and Protein > 0.4 g/L.

Why and how is it used for brain tissue?

Used to isolate Listeria from the brain; tissue is held at 4°C and subcultured weekly for up to 12 weeks.

What do colonies of listeria look like on blood agar?

Small, smooth, flat, with a blue-green color (oblique light) and a narrow zone of β-haemolysis.

Which specimens (listeriosis) do NOT require cold enrichment?

Abortion and septicaemia cases (can go directly to blood agar/MacConkey).

How do you distinguish Listeria from Streptococci?

Listeria is Catalase positive (Streptococci are negative).

What is the characteristic motility of Listeria?

Tumbling motility when incubated in broth at 25°C for 2–4 hours

How does Listeria monocytogenes react in a CAMP test?

It is positive with Staphylococcus aureus (but negative with Rhodococcus equi).

"What is the ""Anton test""?"

A virulence test where broth culture is instilled in a rabbit’s eye to induce keratoconjunctivitis.

Which biochemical reaction is shared with many other soil bacteria?

Aesculin hydrolysis (it turns aesculin media black)

Outbreaks of listeriosis often related to …

silage feeding

forms of diseases caused by Listeria monocytogenes in Sheep, cattle, goats

Encephalitis (neural form) Abortion Septicaemia Endophthalmitis (ocular form)

forms of diseases caused by Listeria monocytogenes in cattle

Mastitis (rare)

forms of diseases caused by Listeria monocytogenes in Dogs, cats, horses

Abortion, encephalitis (rare)

forms of diseases caused by Listeria monocytogenes in pigs

Abortion, septicaemia, encephalitis

forms of diseases caused by Listeria monocytogenes in birds

Septicaemia