VETM3450 - Term Test 5 (Module 5: Bacteriology)

Pre antibiotics, what happened to people?

People died from avoidable infections (chemo complications, pregnancy)

What is the main driving force for antimicrobial resistance?

Antimicrobial use (use creates selective pressure)

Why do we care about antimicrobial resistance?

As a society:

- Treatment failures/delays

- Morbidity/mortality

- More expensive treatments

- Outbreaks can/will happen (these are expensive)

As veterinarians:

- We are currently not regulated in our antibiotic use - we want to keep it this way (in Europe vets are regulated)

The more a bacteria reproduces, what risk increases?

The risk of a mutation to occur and potentially resistance to occur

What do we use antibiotics for in live stock versus companion animals and horses?

Livestock:

- Therapeutic

- Prophylactic

- Disease control

- Growth promotion

- Feed efficiency

Companion animals/horses:

- Mainly therapeutic

- Sometimes prophylactic

We use antibiotics differently and different antibiotics depending on the species

What is the main route of administration of antibiotics to animals in Canada?

In feed

Is antibiotic resistance a virulence mechanism?

No! It is not worse for the infection, it just means the bacteria is harder to kill. The outcome of the infection should be no worse if the resistance is promptly detected and proper treatment is initiated.

How do we reduce the use of antimicrobials?

By improving animal health, through:

- infection prevention and control

- vaccination

- sanitation/hygiene

- equitable access to high quality therapeutics

Infection prevention is better than infection treatment for everyone (animal health, welfare, economically, food safety, public relations)

How does psychology play into antimicrobial use

A lot of times, physicians or veterinarians think 'just in case'. Some will say 'lets try an antibiotic first' instead of doing proper diagnostic testing. And if treatment doesn't work, instead of stopping one antibiotic, sometimes they tend to start another one on top of it.

Two bacteria of note in the spirochaetales family

1. Leptospira

2. Borrelia

General characteristics of spirochaetales

- Slender, helically coiled

- Wrapped around internalized flagellum

- Move corkscrew, flexing or serpentine

- Don't stain well with gram stain

- Use dark field or silver stain

Leptospirosis clinical signs in dogs

- Fever

- Vomiting

- Painful and reluctant to move

- Anorexic

- Diarrhea

- Increased drinking

- Jaundice

- DIC

- Haemorrhage

Acute renal damage and hepatitis:

- Elevated creatinine

- Elevated blood urea

- Elevated creatine phosphokinase and muscle enzymes

- Elevated bilirubin, alkaline phosphatase

Are cats at risk of leptospirosis?

No, and it is not known why

Leptospirosis clinical signs in large animals

- Uveitis (horses)

- Abortion and other fertility problems

- Genital and urinary track colonization

- Mastitis

- Chronic nephritis

Maintenance versus non-maintenance hosts for leptospira

Maintenance: different serovars adapted to animal reservoir (rodents and other small animals like cats), characteristically shedding for a life time (kidney*, +/- genital tract), no clinical disease

Non maintenance: accidental or incidental hosts, a few weeks in the kidneys*

*Proximal convoluted tubule of kidneys and shed in urine

What type of environment will leptospira survive in?

Wet, warm environments (water, mud, soil)

What type of animals are susceptible to leptospira

- Dogs

- Cattle

- Horses

- Small ruminants and pigs

- Humans

Two leptospirosis serovar in pigs. What do they cause?

1. Pomona

- Abortion, chronic nephritis

2. Bratislava

- Small litters, infertility, still births

Two leptospirosis serovar in cows. What do they cause?

1. Pomona

- Abortion, haemoglobinuria, mastitis

2. Hardjo

- Abortion, stillborn, weak calves, mastitis

One leptospirosis serovar in horses. What do they cause?

1. Pomona

- Abortion, recurrent uveitis (periodic opthalmia)

Three leptospirosis serovar in dogs. What do they cause?

1. Canicola

- Acute or chronic renal failure (interstitial nephritis)

2 and 3. Grippotyphosa and pomona

- Fever, hepatitis, acute renal failure

How to diagnose leptospirosis

- Serology used paired serum samples

- Microscopic agglutination test

- SNAP test to detect IgM (a positive test in a healthy animal could mean they are vaccinated or exposed but not diseased)

- PCR of blood and urine

Control of leptosporosis

- Vaccines

- Vector control

- Treatment with antibiotics (doxycycline or ampicillin)

- Try not to let your dog drink out of puddles

Bacterial cause of lyme disease

Borrelia (in Canada most common/significant is borrelia burgdorferi)

Clinical signs of lyme disease in dogs

- Dull, depressed

- Anorexic

- Lame and swollen joints

- Protein losing glomerulopathy

- Rarely progressive renal failure

Clinical signs of lyme disease in horses

- Uvetitis

- Swollen joints

- Skin masses or nodules

- Neuroborreliois (rare - but can present as fever, muscle wasting, difficulty eating, skin sensitivity and neurologic signs)

Morphology of borrelia

Gram negative, spiral shape, rods

Where is lyme disease a problem

Eastern, central and western USA

Vector of borrelia burgdorferi

- A tick called 'ixodes scapularis' also known as the black legged deer tick in eastern/central USA

- A tick called 'ixodes pacificus' in western USA, south western BC

Main host of larvae and nymph ticks carrying borrelia?

White footed mouse, many bird species (first and second host)

Major source of adult ticks that carry borrelia?

Deer

Diagnosis of lyme disease

- History + clinical signs

- SNAP test

Why is it difficult to diagnose lyme disease in endemic areas

Since subclinical infection (exposure) is common, it causes a lot of false negatives if you use a PCR

Control of lyme disease

Vaccination for dogs in endemic areas

Morphology of fusobacterium necrophorum

Filamentous gram negative rods

Characteristics of fusobacterium necrophorum

- Obligate anaerobes

- Create opportunistic, mixed infections (may co-occur with facultative anaerobes that help reduce the redox environment for their growth or have synergistic effects)

- Disease often follows trauma to anatomical barriers

What is fusobacterium necrophorum commensal to?

- Mucous membranes

- GI tract

What three things does fusobacterium necrophorum cause in cattle

1. Calf diphtheria which presents as necrotic pharyngitis/laryngitis and if untreated, may progress to fatal necrotizing pneumonia

2. Digital dermatitis (foot rot in cattle)

3. Hepatic abscesses also called necrobacillosis (secondary to rumenitis)

Pathogenesis of hepatic abscesses in cattle

High grain diet - acidosis - rumenitis - invades liver - causes abscesses

Sequelae of hepatic abscesses in cattle

It can rupture - LPS - endotoxemia - sudden death

What does dichelobacter nodosus cause and in what species

Primary causal agent of foot rot in sheep (starts as interdigital dermatitis and then progresses) and digital dermatitis in cattle

How does dichelobacter nodosus cause foot rot in sheep?

Fusobacterium necrophorum initiates the lesion, but does not progress without a virulent strain of D. nodosus

Three virulence factors of dichelobacter nodosus

1. Fimbriae for adherence

2. Proteases

3. Elastases that damage the tissue

How to prevent ovine foot rot

- Cull infected animals

- Vaccinate

- Reduce disease challenge by quarantining and treating

Are mycoplasma gram positive or gram negative

They are neither! They do not have a cell wall (smallest free living bacteria)

Characteristics of mycoplasma

- Poor environmental survival

- Obligate parasites (extracellular)

- Very fastidious (hard to grow) and therefore under diagnosed

- Causes predisposition to secondary bacterial infections

How is mycoplasma spread

Close contact (and aerosols in short distances)

Where in the body does mycoplasma cause disease

- Respiratory tract mainly

- Also: conjunctiva, genital tract, udder and sometimes causes septicemia

Why is mycoplasma diagnosis difficult?

- Inconsistent disease expression

- Many spp. are commensal

- Conventional culture based diagnostic tests don't work

- PCR identification not offered in routine PCR panels

- Antimicrobial susceptibility testing does not exist for all species of mycoplasma

- Secondary infections often present

- Haemotropic mycoplasmas generally uncultivable

Four mycoplasma species that affect poultry

1. M. gallisepticum (main one we discussed)

2. M synoviae

3. M. meleagridis

4. M. iowae

What does M. gallisepticum cause and in what type of birds

Chicken: chronic respiratory disease

Turkey: infectious sinusitis

Note: it is the most pathogenic avian mycoplasma and infected animals are carriers for life

How is M. gallisepticum transmitted

Vertical (egg transmitted) and horizontal transmission

Where does M. gallisepticum first infect

Conjunctiva and nasal passages first, may progress to bronchi and lungs

What does M. synoviae cause and in what type of birds

Infectious synovitis in chickens and turkeys

What does M. meleagridis cause and in what type of birds

Mucous membrane disease and air saculitis and bursitis in turkeys

What does M. iowae cause and in what type of birds

Air sacculitis, stunting, leg demoformities and mortality embryos in turkeys

Three mycoplasma species that affect pigs

1. M. hyopneumoniae (main one we discussed)

2. M. hyorhinis

3. M. hyosynoviae

What does M. hyopnemoniae cause in pigs

Enzootic pneumonia

What does M. hyorhinis cause in pigs

Arthritis and polyserostis

What does M. hyosynoviae cause in pigs

Polyarthritis

Distribution of characteristic lung lesions of M. hyopneumoniae in pigs

Chronic antroventral bronchopneumonia, lesions are on the tips of the lung lobes

Characteristics of M. hyopneumoniae infection in pigs

- Persists for months

- Adheres to ciliated epithelium in bronchi and bronchioles - this impairs bacterial clearance and predisposes to secondary bacterial infections

- Mostly spread by direct contact and aerosols as well

- Acquired from the sow and spread in weaner-grower pigs

Control of M. hyopneumoniae in pigs

- Monitor at slaughter or serologically in herds

- Maintain good biosecurity

- A vaccine is available

- Deal with secondary bacterial infections

Note: it is complicated to treat

Two mycoplasma species that affect cattle

1. M. mycoides subsp. mycoides

2. M. bovis

What does M. mycodies subsp. mycoides cause in cattle

Contagious bovine pleuopneumonia - this is an exotic disease and reportable in Canada (very rare to see in Canada)

What does M. bovis cause in cattle

- Bronchopneumonia (bovine respiratory disease complex)

- Mastitis with gland fibrosis and purulent plugs

- Arthritis concurrent with pneumonia and mastitis

Where is M. bovis commensal to

Upper respiratory tract, genital tract and udder

Type of lesions seen on post mortem caused by M. bovis

Caseous necrotic lesions

Two mycoplasma species that affect sheep

1. M. ovipneumoniae

2. M. ovis

Two mycoplasma species that affect goats

1. M. capricolum spp. capripneumoniae

2. M. mycoides spp. capris

What does M. ovipneumoniae cause in sheep

Pneumonia

What does M. ovis cause in sheep

Hemolytic anemia

What does M. capricolum subspecies capripnemoniae cause in goats

Contagious caprine pleuropnemoniae

What does M. mycosides spp. capris cause in goats

- Mastitis

- Arthritis

- Keratitis

- Pneumonia

- Septicemia

Mycoplasma species that affects dogs

M. cynos

What does M. cynos cause in dogs

Pneumonia/kennel cough

Mycoplasma species that affects cats

M. felis

What does M. felis cause in cats

- Conjunctivitis

- Upper respiratory tract disease

Length of duration of mycoplasma infections in dogs and cats

Usually chronic

How to diagnosis mycoplasma in dogs and cats

- PCR/qPCR + Sanger sequencing

- MALDI-TOF used for mycoplasma bovis and avian mycoplasma

- Fluorescent antibody testing

Why is mycoplasma difficult to treat

- Inconsistent disease expression, secondary infections often present

- Lack of comprehensive treatment guidelines

- Intrinsically resistant to beta-lactams (because they do not have a cell wall, and beta-lactams inhibit cell wall synthesis)

- Some emerging resistance to other drug classes

Treatment of mycoplasma in dogs and cats

Tetracyline (doxycycline) - often disappointing

Haemotropic mycoplasma in various species cause what?

Anemia with variable severity. Even after treatment animals may remain carriers and infection can recrudesce.

Haemotropic mycoplasma diagonsis

Blood smears or PCR

Characteristics of M. haemofelis? When should this bacteria be on your differential list?

- Infectious anemia in cats

- Incubation period is 2-30 days and anemia lasts for 3-4 weeks, with some animals being chronically infected with normal PCV

- Consider this on your differentials for any anemic cat with evidence of regeneration

Treatment of M. haemofelis in cats

- Doxycycline or enrofloxacin

- May need a blood transfusion

The three main principles of infection control

1. Decrease exposure

2. Decrease susceptibility

3. Increase resistance of host

What happens if a person is bitten by a dog or a cat? What part of government is in charge?

Public health is in charge

- Animal must be in a 10 day quarantine OR euthanized and tested for rabies (irrespective of vaccine status)

- Legally, if a DVM knows about an animal biting a person they must report it

What happens if a dog is bitten by a rapid animal? What part of government is in charge?

OMAFRA is in charge

- Observation period/precautionary confinement period depends on the animal's vaccination status

Difference between an observation period and a precautionary confinement period (PCP)?

Observation period:

- Minimize the animal's contacts outside the household

- Dogs are allowed off the property with an age appropriate handler, but must remain on-leash

- Cats must remain indoors

Precautionary confinement period (PCP):

- A quarantine

- Animal must remain on owner's property at all times

- No contact with other people or animals

- Contact is limited to one age appropriate care taker

- Dog can only go outside on leash with a fence (double barrier)

- When indoors the animal must be kept in a secluded area with double door entry that allows the caretaker to observe the animal before direct contact and prevents accidental escape

What animals need to be legally vaccinated for rabies in Ontario? At what age?

- Dogs

- Cats

- Ferrets

Age: 12 weeks (considered protected 28 days post-vaccine)

Note: horses, cows and sheep need to be vaccinated if they interact with the public

Incubation period of rabies in animals versus people?

- 2-3 months in animals

- 2 weeks-6 years in people

When is rabies considered infectious

Up to 10 days before onset of clinical signs

How is the rabies virus shed?

In the saliva of infected animals (saliva in the eye, blood stream or mucous membrane is considered an exposure)

What is a DVM's role in zoonotic disease education?

We should be educating our clients on the potential of catching zoonotic diseases from their pets. Especially first time pet owners. Educate them on basic practices to reduce risk.

Bacteria that causes rat bite fever in humans

Streptobacillus moniliformis

Why is banning extra label antimicrobial drug use tricky

- Minor species will suffer

- Sometimes the label instructions are inappropriate for our situation

Why is stopping surgical prophylaxis tricky

Antimicrobial prophylaxis at surgery is a lot better than full course after surgery if the animal gets an infection

Are PPE and clothes the same?

No, PPE you should be able to remove after you're done

Three bacteria in the anaplasmataceae family

1. Anaplasma

2. Ehrilichia

3. Neorieckettsia