bacterial pathogens affecting respiratory tract

What type of pathogens affect the respiratory tract?

Commensals/opportunistic

What is the route of infection for contagious pathogens?

Inhalation

-also direct contact

What is the Gram stain and morphology of the Pasteurellaceae bacteria?

Gram-negative bacillus; facultative anaerobe

Which bacteria lacks a cell wall?

Mycoplasma spp.

-does not gram stain

-facultative anaerobe

What type of bacteria is the genus Rhodococcus, and what does it produce?

-Gram + bacillus (coccobacillus)

-obligate aerobe

-produces capsules (mucoid colonies)

Where is Rhodococcus found?

Found in soil, carrier animals (shed in feces)

-aerosol ± oral transmission

-enzootic on some farms

What disease does Rhodococcus equi cause?

Foal pneumonia

What are preferred samples for diagnosing Rhodococcus?

• Culture

  • transtracheal wash (TTW), bronchoalveolar lavage (BAL) > nasal swab

  • PCR on cultured isolate

How is Rhodococcus treated?

• antimicrobial therapy

  • Macrolide (erythromycin, clarithromycin, azithromycin) + rifampin because of synergism

Is Rhodococcus equi zoonotic?

• Yes, in immunocompromised

  • Virulence associated protein A (VapA), carried on a plasmid (prevents macrophages from destroying bacteria in phagolysosomes)

What does foal pneumonia cause?

• Pyogranulomatous, abscess-forming; chronic/subclinical infections possible
• Major economic impacts on horse industry
• Hematogenous spread to other parts of the body (e.g. septic arthritis)
• Failure of passive transfer is a risk factor

How do you prevent Rhodococcus equi?

-limit overcrowding in foals; good farm biosecurity/hygiene

-ensure adequate colostrum intake for neonates

T/F: no licensed vaccines are available for Rhodococcus equi.

True

How do you address lung abscesses in Rhodococcus?

May need to be surgically removed

What are key features of Bordetella?

• Gram-negative bacillus

• obligate aerobe

• inhalation or direct contact

• coinfection with Pasteurella spp.

What animals does Bordetella bronchiseptica infect?

dogs, rabbits, pigs

What disease does Bordetella bronchiseptica cause in dogs?

Kennel cough

• usually multifactorial (other bacteria + viruses also implicated in disease process)

• coughing ± nasal discharge

• similar disease in cats (coughing)

What disease does Bordetella bronchiseptica cause in rabbits?

Snuffles (rhinitis)

• ocular and nasal discharge, dyspnea

• subclinical infections (carrier animals)

What disease does Bordetella bronchiseptica cause in pigs?

Atropic rhinitis

• Sneezing, nasal turbinate destruction

• Economically important disease

What are appropriate diagnostic methods for Bordetella?

Culture; TTW/BAL; nasal swabs; PCR

T/F: antimicrobial susceptibility interpretations in Bordatella exist only for pigs.

True

What is Bordetella rx and prevention for dogs and cats?

• Usually self-limiting, upper airway disease → supportive care
• Antimicrobial therapy only if there is evidence of pneumonia
• Vaccination (live intranasal or oral) + vaccination against respiratory viruses
• Kennel/boarding facilities

What is Bordetella rx and prevention for rabbits?

• highly likely to relapse

• uncommon in commercial production systems due to vaccination

What is Bordetella rx and prevention for pigs?

• usually culled

• uncommon in commercial production systems due to vaccination

What are key features of the Family Pasteurellaceae?

• Gram-negative, short bacilli

• facultative anaerobes

What are Pasteurellaceae bacteria commensals of?

• upper airway/oral mucous membranes

  • Disease when they get into the lower airway

  • Secondary infections after primary viral infections; viral infections due to stress/management issues

  • Pasteurella spp. → animal bite wound infections

What diseases are caused by major Pasteurellaceae members?

• Contagious pleuropneumonia (Actinobacillus pleuropneumonia)

• Glässer's disease (Glaesserella parasuis)

• BRDC (Mannheimia haemolytica)

• Pasteurellosis (Pasteurella multocida)

What differentiates Actinobacillus pleuropneumoniae from Glaesserella parasuis?

• APP:

  • age 2-6 months

  • Clinical signs:

    • coughing common

    • bloody nasal/oral discharge

    • disease possible in adult pigs (abortions)

• G. parasuis

  • age 1-2 months

  • clinical signs:

    • coughing uncommon

    • polyarthropathy (swollen joints)

    • neuro signs

Which disease in pigs causes this?

Actinobacillus pleuropneumonia (APP)

Which disease in pigs causes this? (fibrinous polyserositis)

Glaesserella parasuis (Glasser’s disease)

What is the same between Actinobacillus pleuropneumoniae from Glaesserella parasuis?

• in pigs

• normal flora of tonsil/upper resp tract

  • transmitted by direct contact or fomites

  • clinical disease when stressed

• clinical signs:

  • rapid onset, severe resp signs (open-mouth breathing)

  • high fever

  • sudden death

  • reduced growth rates in recovered pigs

Post mortem findings of Actinobacillus pleuropneumoniae
(Contagious Pleuropneumonia)

• Severe bronchopneumonia on necropsy with fibrinous pleuritis/pericarditis

• Extra-thoracic lesions are uncommon

Post mortem findings of Glaesserella parasuis (Glässer’s disease)

• Severe bronchopneumonia on necropsy
• Fibrinous polyserositis, polyarthritis, and meningitis (secondary to sepsis)

What is Bovine Respiratory Disease Complex (BRDC)?

• shipping fever

• Enzootic pneumonia of calves (6-12 mos)

• multifactorial; stress + viral + secondary bacterial infection

• significant cost to beef industry in US

What are clinical signs of Mannheimia haemolytica?

Fever, lethargy, reduced growth rate

-severe, acute, hemorrhagic and fibrinonecrotic pneumonia

What diseases are caused by Pasteurella multocida?

BRDC, atrophic rhinitis, snuffles, fowl cholera, bite wound infections

What are features of Histophilus somni?

• Component of BRDC
  • Fever, lethargy, reduced growth, bronchopneumonia

• Thrombotic meningoencephalitis (TME)
  • Neurologic signs (ataxia, recumbency, blindness),
  sudden death

• Myocarditis, proliferative endocarditis
  • Sudden death

what is the sample type for culture of Histophilus somni?

Lung

what is the sample type for culture of myocarditis, proliferative endocarditis? (Histophilus somni)

heart/valves

what is the sample type for culture of Thrombotic meningoencephalitis? (Histophilus somni)

Brain

How is Pasteurellaceae diagnosed?

• Culture

  • oxidase-positive

  • PCR

    • resp disease panels

    • subtyping

  • susceptibility testing

    • increasing resistance in BRDC pathogens

  • some species have requirements for X- and V-factor (found inside RBCs → cells must be lysed for bacteria to access)

Pasteurellaceae Prevention

• Vaccination, when available
  • Pigs: Actinobacillus pleuropneumoniae, Glaesserella parasuis
  • Cattle: BRDC pathogens (viral and bacterial)

• Preconditioning (cattle)
  • Staging stressful procedures (vaccines, dehorning, etc.)
  • Weaning at least 45 days before sale/shipment
  • Bunker training

• Bite prevention

What are key characteristics of Genus Mycoplasma?

• Does not Gram stain (lacks cell wall)

  • pleomorphic

  • 0.3-0.8 um

  • plasma membrane contains sterols (e.g. cholesterol) → aid in stability

• facultative anaerobe

Why is Mycoplasma difficult to culture?

(depending on species)

• requires specialized transport and growth media

• slower growing (~2 weeks)

• “fried egg” colonies

• PCR is a better bet for diagnosis

What animals are affected by Pasteurella multocida?

cattle/ruminants, pigs, rabbits, birds

How are cattle/ruminants affected by Pasteurella multocida?

component of BRDC

How are pigs affected by Pasteurella multocida?

atrophic rhinitis; indistinguishable from Bordetella

How are rabbits affected by Pasteurella multocida?

snuffles (rhinitis); indistinguishable from Bordetella

How are birds affected by Pasteurella multocida?

fowl cholera (sudden death without clinical signs; respiratory signs and swelling of wattles, joints, tendon sheaths)

Which type of cell wall contains a plasma membrane and peptidoglycan?

Gram-positive bacterial cell wall

Which type of cell wall contains a plasma membrane, peptidoglycan, and outer membrane?

Gram-negative bacterial cell wall

Which type of cell wall contains just a plasma membrane?

Mycoplasma spp. cell wall

What diseases are caused by Mycoplasma spp. in pigs?

Porcine enzootic pneumonia

• grower/finisher pigs

• complications with secondary Pasteurella infection

What diseases are caused by Mycoplasma spp. in poultry?

• upper resp tract disease, sinusitis

• turkeys especially susceptible

What diseases are caused by Mycoplasma spp. in cattle/small ruminants?

• can be part of the bovine respiratory disease complex (shipping fever)

• systemic spread → arthritis, meningitis, otitis, mastitis, abortion

How is Mycoplasma diagnosed?

• PCR

  • lung, tracheal/bronchial/sinus aspirates

• culture

• serology

How is Mycoplasma prevented and treated?

• Commensal organism of mucous membranes

• Vaccination

  • does not prevent infection

• Antimicrobial therapy

  • Medicated feed/water (tetracyclines)

  • Beta-lactam antibiotics do not work!! (target the cell wall)

• Culling

  • Somes Mycoplasma spp. are reportable

Which disease do beta-lactam antibiotics NOT work in?

Mycoplasma spp.

-target cell wall