4: moraxella and actinobacillus

What are the Oxidase and Catalase results for most Moraxella species?

Usually positive for both.

Does Moraxella bovis grow on MacConkey agar?

No. Growth requires enrichment with blood or serum.

How do the colonies of virulent strains of M. bovis behave on agar?

They are fimbriated, haemolytic, and tend to grow into the agar.

What is the primary biochemical characteristic of Moraxella regarding nutrient utilization?

They are proteolytic but generally unable to utilize sugars

What is the common name for the disease caused by Moraxella bovis?

"Infectious Bovine Keratoconjunctivitis (IBK) or ""Pinkeye."""

Where is M. bovis normally found in carrier cattle?

On the mucous membranes (e.g., conjunctiva, nasal mucosa).

"Why is M. bovis considered ""short-lived"" in the environment?"

It is highly susceptible to desiccation (drying out)

Which virulence factor is essential for M. bovis to attach to the cornea?

Fimbriae (pili).

The genus Moraxella is divided into which two subgenera:

Moraxella and Branhamella.

What age group of cattle is most commonly affected by IBK (Pinkeye)?

Usually animals under 2 years of age (older animals often have age-related immunity).

Where do asymptomatic carriers harbor M. bovis

The nasolacrimal ducts, nasopharynx, and vagina.

What are the three primary routes of transmission for IBK?

1. Direct contact. 2. Aerosols. 3. Flies acting as vectors.

Distinguish between the two types of fimbriae (pili) in M. bovis.

Q fimbriae: Specific for colonization (initial attachment). I fimbriae: Allow for local persistence of infection.

What is Mbx A, and what is its specific function?

An RTX toxin (haemolysin/cytolysin) that is calcium-dependent and forms pores in neutrophil cell membranes

How do neutrophils paradoxically contribute to corneal damage in IBK?

When M. bovis cytotoxins kill neutrophils, they release hydrolytic enzymes that break down the corneal collagen matrix.

Which two factors must be present for a strain of M. bovis to be considered virulent

It must possess both cytotoxin (haemolysin) and fimbriae.

What specific deficiency in bovine lacrimal secretions may explain their high susceptibility to M. bovis?

A deficiency of lysozyme (an enzyme that normally breaks down bacterial cell walls).

Virulence Factors of Moraxella bovis

• Q piliI pili

• Mbx A (RTX Toxin) Kills neutrophils and causes haemolysis.

• LPS (O Antigens)- Plays a role in the general inflammatory response/virulence.

• Lytic Enzymes- Includes hyaluronidase and aminopeptidase; degrades host tissue.

List the clinical progression of IBK from earliest sign to most severe outcome.

1. Blepharospasm, conjunctivitis, lacrimation. 2. Keratitis and corneal ulceration. 3. Opacity and abscessation. 4. Panophthalmitis and permanent blindness.

"What is ""coning"" in the context of IBK?"

A weakening of the cornea that causes it to bulge or take on a cone-like shape due to pressure/damage

Why can an animal be immune to one strain of M. bovis but get sick from another?

Fimbrial-mediated antibodies are type-specific; if the new strain has a different fimbrial type, the previous antibodies won't block adherence.

What is the most suitable specimen for Moraxella bovis diagnosis, and how must it be handled?

Lacrimal secretion (tears). It must be processed promptly (ideally within 2 hours) or placed in sterile water because the organism is highly susceptible to desiccation

Contrast the immunity provided by anti-haemolysin vs. anti-fimbrial antibodies.

Anti-haemolysin: Cross-protective against other strains. Anti-fimbrial: Type-specific (non-cross-protective).

How do virulent Moraxella bovis strains behave when placed in a saline solution?

They autoagglutinate.

How many fimbriate serogroups of M. bovis have been identified?

7

What are the two preferred routes for administering antimicrobials for IBK?

Subconjunctival or topical administration (early in the disease).

Which systemic antibiotic can be used prophylactically for animals at risk

Oxytetracycline (intramuscular)

"Why are fimbriae-only vaccines often considered to have ""uncertain efficacy""?"

Because of fimbrial type-switching; vaccines incorporating both cytotoxin and fimbriae generally provide better protection.

Moraxella boevrei may be isolated from…

Isolated from the upper respiratory tract of healthy goats

Moraxella bovoculi may be isolated from…

Isolated from animals affected by infectious bovine keratoconjunctivitis

Moraxella canis may be isolated from…

member of the oral fl ora of dogs. Has been isolated from dog bite wounds in humans

Moraxella caprae may be isolated from…

Isolated from the upper respiratory tract of healthy goats

Moraxella caniculi may be isolated from…

Isolated from infectious bovine keratoconjunctivitis in association with other organisms

Moraxella equi may be isolated from…

Conjunctivitis in horses

Moraxella lacunata may be isolated from…

Isolated from a number of pathological conditions in animals including goats, dogs, pigs and aborted equine foetuses. Pathogenicity unknown

Moraxella ovis may be isolated from…

Isolated from healthy animals and those with keratoconjunctivitis

Moraxella phenylpyruvica may be isolated from…

isolated from a number of sites in farm animals but pathogenicity uncertain

what concurrent infections may exacerbate IBK

Infection with bovine herpesvirus 1 or Thelazia species

What unique physical property do colonies of Actinobacillus lignieresii, A. equuli, and A. suis exhibit on blood agar?

"They exhibit cohesive properties (they stick together or ""clump"") when touched with an inoculation loop."

Which three Actinobacillus species/subspecies are typically haemolytic?

1. A. pleuropneumoniae 2. A. suis 3. A. equuli subsp. haemolyticus

Which two Actinobacillus species of veterinary importance do not grow on MacConkey agar?

A. pleuropneumoniae and A. seminis

How do A. equuli and A. suis appear on MacConkey agar?

As pink colonies (because they ferment lactose).

What is the basis for serotyping A. pleuropneumoniae?

Differences in capsular polysaccharide antigens.

"Actinobacillus: ""Wooden Tongue"""

A. lignieresii

"Actinobacillus: ""Sleepy foal disease"""

A. equuli

What is the primary clinical manifestation of bovine actinobacillosis?

(A. lignieresii) Timber tongue (Wooden tongue): a chronic pyogranulomatous inflammation of the tongue.

How does A. lignieresii enter the soft tissues of cattle?

Through erosions or lacerations in the mucosa or skin (often caused by rough feed)

In addition to the tongue, which two areas are clinically important lesion sites of A. lignieresii?

1. Oesophageal groove (leading to tympany/bloat). 2. Retropharyngeal lymph nodes (leading to swallowing/breathing difficulty).

"What are the clinical signs of an animal with ""timber tongue""?"

Drooling saliva and difficulty eating due to the hard, indurated (stiffened) tongue.

What are the growth characteristics of A. lignieresii on Blood Agar?

Small, sticky, non-haemolytic colonies.

How does A. lignieresii appear on MacConkey Agar

It shows slow lactose fermentation (colonies start pale and turn pink after 48 hours).

What is the definitive method for identifying A. lignieresii isolates today?

Analysis of 16S rRNA gene sequences.

True or False: A. lignieresii is a hardy organism that survives for months in the environment

False. It is a commensal that survives for only about 5 days in hay or straw.

"What are the traditional ""iodide"" treatments for Actinobacillosis?"

Sodium iodide (parenterally) or Potassium iodide (orally).

Which antibiotics are generally effective against A. lignieresii?

Potentiated sulphonamides or a combination of penicillin and streptomycin

What drug is used for 30 days in animals with refractory (stubborn) lesions?

Oral isoniazid.

A. lignieresii in sheeps, sows, dogs, and horses

sheep: Cutaneous actinobacillosis of sheep presents as granu lomatous lesions mainly on the head without tongue involvement.sows: Granulomatous mastitisdogs: bite woundshorse: glottis

Why is A. pleuropneumoniae unique compared to other species in its genus?

It is the only species considered a primary pathogen (capable of causing disease in healthy hosts).

What age group is most susceptible to APP, and what triggers outbreaks?

Pigs under 6 months of age; outbreaks are precipitated by poor ventilation and sudden temperature drops.

Describe the characteristic respiratory signs of acute APP.

Dyspnoea, blood-stained froth at the nose/mouth, and cyanosis (blue tint to skin).

What are the hallmark gross lesions of APP seen at post-mortem?

Necrotizing fibrino-haemorrhagic pneumonia with pleuritis and pericarditis.

What are the most significant virulence factors produced by A. pleuropneumonia?

RTX (repeat-in-toxin) cytotoxins (designated ApxI to IV).

ApxI

a highly hemolytic and cytotoxic RTX (repeats-in-toxin) of APP that causes cell damage and apoptosis in alveolar macrophages by activating mitogen-activated protein kinases (MAPKs) via integrins.

a highly hemolytic and cytotoxic RTX (repeats-in-toxin) of APP that causes cell damage and apoptosis in alveolar macrophages by activating mitogen-activated protein kinases (MAPKs) via integrins.

ApxI

Which RTX toxin is produced by all serovars of APP?

ApxIV. (contributing to the severe, often fatal, lung damage in pigs.)

How does APP obtain essential iron from the porcine host?

By utilizing heme products from haemolysis and obtaining iron directly from porcine transferrin

How does the host's immune system respond to APP?

Both neutrophils and macrophages phagocytose it, but only neutrophils can effectively kill it; APP can survive inside macrophages.

What causes the localized ischaemic necrosis and microthrombi in the lungs?

Damage to endothelial cells and activation of Factor XII by LPS, which initiates coagulation and fibrinolysis.

function of LPS as a virulence factor

Facilitates adhesion and triggers the inflammatory/coagulation cascade.

RTX cytolysin of APP that is of pathogenic significance

ApxI and ApxII

Virulence Factors of A. pleuropneumonia

• capsule

• Apx Toxins (I-IV)

• LPS

• fimbriae

• SOD

Where do subclinical carrier pigs harbor the organism?

In the tonsillar tissues and the respiratory tract.

What are the growth requirements for Biotype 1 vs. Biotype 2 of APP?

Biotype 1: Requires V factor (NAD) for growth. Biotype 2: NAD-independent.

How does APP behave in a CAMP test with Staphylococcus aureus?

It is CAMP-positive (it shows enhanced haemolysis in the presence of S. aureus).

Does A. pleuropneumoniae grow on MacConkey agar

No. (This helps distinguish it from A. suis and A. equuli)

What is a DIVA vaccine?

A vaccine that allows for Differentiating Infected from Vaccinated Animals.

What are the two subspecies of A. equuli, and which one possesses an RTX toxin?

1. subsp. equuli 2. subsp. haemolyticus (possesses the eqx gene for RTX activity)

Where is A. equuli normally found in carrier mares?

In the reproductive and intestinal tracts.

What are the two primary routes of infection for a newborn foal?

1. In utero (congenital infection). 2. Post-birth via the umbilicus (navel).

"Why is it called ""Sleepy Foal Disease""?"

"Affected foals are febrile and recumbent (extreme lethargy), often appearing ""sleepy"" or unable to stand."

What classic kidney lesion is found in foals with sleeping disease that survive the first 1–3 days?

Pin-point suppurative foci (embolic nephritis) throughout the kidneys.

If a foal recovers from the acute septicaemic phase, what secondary conditions might develop?

Polyarthritis (joint ill), nephritis, enteritis, or pneumonia.

How does A. equuli appear on MacConkey agar?

It grows well and produces pink colonies (lactose fermenter).

"What are the ""sticky"" colony characteristics of A. equuli on blood agar?"

They are non-haemolytic (subsp. equuli) or haemolytic (subsp. haemolyticus) and highly cohesive/sticky.

Which antibiotics are typically effective against A. equuli if detected early

Streptomycin, tetracyclines, and ampicillin.

What does supportive treatment for an Sleepu Foal Disease affected foal usually include?

Blood transfusions and bottle-feeding with colostrum (to ensure passive immunity).

How does A. suis differ from A. pleuropneumoniae in terms of invasiveness?

A. suis is more invasive; while it causes pneumonia, it also causes septicaemia, meningitis, metritis, and abortion.

What are the clinical signs of A. suis in affected litters?

Fever, respiratory distress, prostration, and paddling of the forelimbs (due to meningitis).

What unusual clinical sign can A. suis cause in mature pigs?

Skin lesions that resemble swine erysipelas (diamond-skin disease).

which RTX toxins are produced by A. suis?

ApxI and ApxII.

What is the primary route of transmission for piglets?

Aerosols from the upper respiratory tract of sows or through skin abrasions.

What are the growth characteristics of A. suis on blood agar?

It produces sticky, haemolytic colonies.

how does A. suis appear on MacConkey agar?

It grows well and produces pink, lactose-fermenting colonies.

How can you distinguish A. suis from A. pleuropneumoniae in the lab?

MacConkey growth: A. suis grows and ferments lactose; A. pleuropneumoniae does not grow on MacConkey.

What is the definitive method for identification of A. suis?

Analysis of 16S rRNA gene sequences.

Which antibiotics is A. suis usually susceptible to?

Ampicillin, carbenicillin, potentiated sulphonamides, and tetracyclines.

What is the primary clinical condition caused by A. seminis?

Epididymitis in young rams.

Which age group of rams is most commonly affected by A. seminis?

Virgin rams between 4 and 8 months of age

What is the suspected route of infection for A. seminis?

An ascending opportunistic infection from the prepuce (where the organism is found).

What are the hallmark clinical signs of A. seminis infection in the scrotum?

Abscess formation in the epididymis and purulent discharge through fistulae on the scrotal skin.