Bacteriology and Mycology Flashcards
Campylobacter
– Gram – rods
– Curved (“Vibrios”)
– Spiral when grouped
– Aerobes or microaerophilic
– 3-15% O2, 3-5% CO2
– Some grow optimally at 42°C
– Flagella
– Darting or corkscrew motility
– Wet mounts useful in diagnostics
* Hanging drop
– Commensals
– Obligate parasites
– Mucosa of GIT
– Glandular crypts of genital tract and GIT
Important Campylobacter
– C. jejuni
– Enteritis in many (including man)
* Abortion and hepatitis
– C. coli
– Similar to C. jejuni
– Organism seen commonly in pigs
– C. fetus subsp. venerealis
– Bovine venereal campylobacteriosis
* Endometritis, infertility and abortions
– C. fetus subsp. fetus
– Abortion in cattle and sheep
– L. intracellularis
– Proliferative enteritis in pigs
Campylobacter spp. (Parasitic properties)
– Attach
– Fibronectin binding proteins
– Pili (F antigens) ?
– Lipoproteins
– Flagella (H antigen) ?
* Colonisation
– LPS (O antigen) ?
– Invade
– Strain dependent (serovars)
– Capsule (S layer)
– Cause inflammation
– Enterotoxins
* Cholera Toxin and Heat Labile toxin
* Hypersecretory diarrhoea similar to ETEC
– Cytotoxins
* Shiga-like toxins – cell death and
haemorrhage similar to EHEC
– Endotoxins
– Intracellular survival
– C. jejuni can survive within macrophages
* Disease severity, duration of symptoms
and relapse
C. jejuni
– Found in the intestinal tract of normal and diseased
animals
– Causes mild to moderate febrile (fever), enteritis with diarrhoea in several animals including humans.
– Occasional cause of abortion in sheep and other species and vibrionic hepatitis in chickens
– Vibriosis = diseased caused by curved bacteria
C. jejuni (Host Factors)
– Young, pregnant and immunocompromised
– Superficial erosive colitis and ileitis
– Fluid loss
– Water, mucus and blood stained diarrhoea
– Extracellular immune arm important
– Local IgA to H antigen
– Intestinal immunity
– Colostrum in newborns important
– Humoral antibody (IgG and IgM) to surface antigens (mainly O antigens) important in systemic immunity
– Recovered can sometime still shed ?
– Commensal versus carrier ??
– Vaccine ??
– Care with antimicrobial therapy
– Worry about antimicrobial resistance
development
* Animal and public health
– Treat in severe cases ?
C. jejuni (Environmental Factors)
– Faecal-oral transmission
– Direct or indirect (exogenous)
– Stress and physiological status can facilitate
endogenous disease in carriers
* Reduce stress and improve
husbandry/nutrition
– Can be shed in milk and contaminate meat
during slaughter
* Zoonoses
– Close contact
– Reduce stocking density
– Poor hygiene
– Improve to control and prevent
– Survive in water
– Faecal contamination
– Treatment of water to control and prevent
* Chlorination
* Filtration
C. jejuni (Zoonoses)
– Self limiting diarrhoea in humans
– Various sequelae
* Guillain-Barre-Stohl Syndrome
– Severe neurological disease
– Acute immune-mediated
demyelination of peripheral nerves
– Follows infection with serotype O19
(20-40%)
– Genetic predisposition in the
individuals
– Illness often lasts months and in
some cases is associated with
permanent incapacitation or even
death
– Food safety issue in poultry, pigs and cattle
Path of C. jejuni
Ileum and large intestine –> susceptible animal –> attrated to and colonise mucus —> localise in glandular crypts –> invade intestinal epithelial cells –> mild (usually) to severe GIT illness –> Bacteraemia:
EITHER:
- Guillain-Barre syndrome (human)
- Abortion (sporadic to outbreak)
OR:
Recovery and shedding
C. fetus subsp. venerealis
– OBLIGATE PARASITE
– Bovine reproductive tract
* Preputial crypts of older bulls
* Vagina of carriers
– 1-2 years of carriage
– Endometritis, temporary infertility and occasional
abortion
– Serotype/subsp. intermedius also recognised
– Also known as serotype A-sub 1
* Serotype A-1 refers to subsp. veneralis
– S-layer
C. fetus subsp. venerealis (Factors)
Parasitic properties
– Obligate parasite bovine reproductive tract
– Surface array proteins (S layer)
* Repetitive array of proteins on the outer cell wall
– Antiphagocytic, inhibits complement and
provides antigenic variation
Host factors
– Asymptomatic infections common
* Preputial crypts in bulls > 5 years old protect
organisms and result in prolonged carrier
state.
– More common in beef herds
* Natural mating
– Immunity and immune response important
* Humoral as it is extracellular in nature
– Immune status of the herd dictates clinical signs
* Acute (no previous exposure), chronic
infection (if local vaginal antibodies
produced)
C. fetus subsp. venerealis (Immunity)
– Protective immune responses develop between 6-12 weeks after infection
– Recovery is antibody mediated
* Immobilsation and opsonisation of the
bacteria
Uterus response
– IgG1 predominant Ig in uterus and is derived
from serum
– IgG1 immobilises and opsonises the bacteria
– Once engulfed by phagocytic cells it is rapidly
destroyed
– Bacteria are gradually eliminated from uterus
and fallopian tubes within 6 months
– Vaginal response
– Locally produced IgA is the predominant Ig in
the vagina
– IgA immobilises but does not opsonise
bacteria.
– IgA binding blocks the opsonising function of
IgG
* This my account for the persistence
of bacteria in the cervix and vagina
for up to 2 years
– Incidence of carrier cows that retain infection from one gestation to the next is
low, it is often enough to permit disease to persist in large beef herds.
– There is a period of convalescent immunity
following recovery in which they are protected
from re-infection
– However, cows eventually become susceptible
to re-infection
C. fetus subsp. venerealis (vaccination)
– Bivalent killed vaccine containing the two serotypes;
veneralis and intermedius
– Has a preventive effect
– Immunity lasts <12 months
– May also be of assistance in treatment and cure
of carriers ?
* IgG1 ✓
Pathogenesis of Bovine venereal campylobacteriosis
Preputial cavity
Venereal infection
Infection of vagina, cervix and uterus
endometreosis
THE EITHER:
1. sporatic abortion
2. Infertility (extended cycles and repeat breeding)
3. Development of immunity (IgA or IgG1)
IgA –> Vagina Cervix –> carrier 1-2 years
IgG1 –> Uterus —> Resistance to reinfection
C. fetus subsp. venerealis (Control and prevention)
– Good husbandry
– The use of young bulls that have tested negative
– Culture and antibody !!
– PCR useful
– Breed virgin heifers to young negative tested bulls
– Replacement heifers or cows
– Culture/PCR and antibody tested negative
before entering the breeding herd
– If endemic
– Annual vaccination
* Immunity is short-lived
* Boosters in bulls and cows 1 month prior
to joining
– Cull bulls
– Rest the herd for a breeding season
* Eliminating the bacteria
– Use of Artificial Insemination (AI) (with semen
treated with antimicrobials) can eliminate the
organism
Order Spirochaetales
– Slender, flexible and helically coiled
– Motile by rapid rotation around long axis and by flexing
– Anaerobes, microaerophilic or aerobes
– Differentiations based on morphology and antigenic
properties rather than biochemical tests
– Gram negative but stains poorly
– Darkfield and silver stains work best
– 4 pathogenic genera
– Brachyspira (formerly Serpulina)
– B. hyodysenteriae → swine dysentery
– Borrelia
– B. anserina → avian spirochaetosis
– B. burgdorferi → Lyme disease
– B. theileri → tick spirochaetosis in cattle
– Leptospira
– Leptospira serovar Hardjo → abortion and
agalactica in cattle
– Leptospira serovar Pomona → abortion and
stillbirth in pigs
– Leptospira serovar Icterohaemorrhagiae →
mild disease in rodents, fulminant (sudden and
severe) leptospirosis in various incidental hosts
including humans tick spirochaetosis in cattle
– Treponema
– T. pallidum → syphilis in humans
Leptospira
– Strict aerobe
– Grow best at 30°C
– Morphologically and physiologically similar
– Thin spiral organisms
– Occur in many animal species and humans
– Considerable heterogeneity amongst the genus
– Serological (antigenic) classification has been used for many years
– The organism is excreted in the urine (leptospiruria) as it tends to colonise in the kidney tubules
Leptospirosis
– In the incidental (dead-end) host
– Acute and subacute disease
– Severe to moderate disease
– Septicaemia and endotoxaemia
* Haemorrhages and fever
– Nephritis, hepatitis, agalactica and meningitis
– In the reservoir host
– Chronic or subclinical disease
* Abortion, stillbirth, infertility, nephritis and
inflamed iris (iridocyclitis)
– Obligate parasites
– Disease ➔ Localisation and proliferation
Leptospirosis factors
Parasitic properties
– Haemolysins
* Cytotoxin
– Endotoxins
* Gram negative LPS cell wall
* Low potency
– LPS may mediate adherence of neutrophils to endothelial cells and platelets
* Role in thrombocytopaenia
– LPS is immunogenic and responsible for serovar specificity
– Glycoprotein cytotoxins ?
Environmental factors
– Host adaptive
– Survives in the environment for up to 6 weeks
(not a saprophyte as it doesn’t replicate)
* Prefers warm, moist, neutral or slightly
alkaline pH
– Contaminated water is an important infectious
source
Leptospirosis pathogenesis
– Entry via mucous membranes or damaged skin
– Pass into circulation via lymphatic
– Disease results from systemic infection and
localisation
– Disease spectrum depends on the serovar and the
host infected
– Incidental host → acute disease
* Damage to endothelium of small blood vessels
and leakage of blood and leptospires into
tissue
* Host develops a marked antibody response
and there is rapid elimination of the pathogen
* Or overwhelming infection can lead to death
– Reservoir host → chronic disease
* Passes into the kidney and resides in the
lumen of the proximal convoluted tubules
and shed in urine
* Weak antibody response which facilitates
persistent infection (months or years)
* Venereal transmission possible
Leptospirosis Immunity and Vaccination
– Protective antibody is serovar specific
– Agglutination and/or opsonisation
– Persistent infection may result from inability of
antibody to reach sites of infection in the
absence of inflammation
* More often related to reservoir host-
adapted poor antigenicity
– Vaccination (bacterin) is used for most prevalent
serovars in a species/region.
– Immunity lasts 12 months, therefore need
annual booster
– Passive acquired antibody is protective
(usually for the first 6 months)
– Can reduce the incidence of shedding,
particularly when vaccinated young animals
(reservoir host)
– Incidental host can be fully protective
Leptospirosis zoonosis
– Occupational zoonosis of dairy farmers and abattoir
workers
– Headache, fever, muscle pains and
conjunctivitis
– Vaccination of herd can reduce shedding and
zoonotic risk
– Dairy design can also reduce risk
– Wear protective equipment
– Disinfect the dairy and improved dairy hygiene
Leptospirosis (Control and Prevention)
– Ideally elimination of carriers
– Reduce environmental contamination
– Vaccination may help reducing shedding in reserve host
– Vaccinating dogs is effective (protects against
some serovars)
– Antimicrobial therapy not advisable in cattle or pigs
– Often not curative, can still culture the
organism from urine samples
– Companion animals and man use doxycycline
– Can be lengthy up to one month
– Deal with urine waste
– Disinfecting and clean the dairy regularly
– Water treatment and security
– Pest control
– Rodents can be reservoir or incidental hosts
and mechanical vectors
– Dairy design and farmer education
– Most cases in young dairy farmers 20-24 yrs
Genus Mycoplasma
– Class Mollicutes
– Obligate extracellular parasites of animals
and plants
– Smallest and simplest free living
– NO CELL WALL
– Cannot synthesis peptidoglycans
– Cytoplasm bound by a cytoplasmic
membrane
– VERY FRAGILE
* Do not survive long outside the host
* Susceptible to heat, desiccation,
disinfectants and detergents
– Resistant to antibiotics that interfere with cell
wall synthesis
* Penicillin
– PLEOMORPHIC
– Filamentous, spherical, hollow rings and pear
shape
– Facultative anaerobes and microaerophilic
– Even when given required nutrition supplements and optimal conditions, they grow SLOWLY
- require COMPLEX media for culture
– Some are impossible to grow in the lab
– PCR and serology are useful diagnostic
aids
“fried egg apperance”
Mycoplasma
No cell wall
Motile
– Commensal
– Host specific
– Chronic disease
* Respiratory
* Urogenital (including mammary
gland)
* Serosal surfaces (joints, peritoneum, pleura)
– Anaemia
* Parasites of erythrocytes
Mycoplasma epidemiology and properties
– Very fragile – easily inactivated
– Most spread by close contact
– Contagious
– Aerosols
* Piggeries, poultry sheds
– Vertical transmission
- Auto-immune disease
Mycoplasma key points
– Host and environmental factors may predispose
to disease caused by mycoplasmas
– Stress (eg. transport and overcrowding
– Husbandry practices
– Age (eg. young most susceptible)
– Immunity
– Concurrent disease
– Mycoplasmas often exacerbate disease initiated
by other pathogens and vice versa
– This is particularly true in the respiratory tract.
What is the most signif disease of cattle worldwide?
M. mycoides subsp. mycoides
small colony type
Contagious bovine pleuropneumonia
M. hyopneumoniae
(Enzootic pneumonia of pigs (EPP))
– Obligate parasite of the respiratory tract of pigs
– Upper and lungs
– Associated with cilia and causes ciliostasis and
extensive loss of cilia
– The continuous nature of pig production ensures a self perpetuating cycle of infections from older to younger pigs
– Recovered pigs protected against re-infection
– Breakdown in EPP-free herds usually occurs following the introduction of infected animals, although windborne transmission is also suspected
– Wild boars ?
M. gallisepticum
– Respiratory tract of chickens, turkeys and other birds
– Nasal sinuses and tracheas
– Reproductive tract
– Causes respiratory disease
– Many factors influence the onset and severity of disease
– Subclinical to severe in complicated disease
– Exacerbated by:
* Concurrent infections (ILT and E. coli)
* Environmental factors which lower the
resistance in the bird Sinusitis
– Immune birds may remain carriers and
can transmit the disease horizontally
(aerosols) or vertically (egg)
Live attenuated vaccine
M. haemofelis
– Haemophilic mycoplasma
- cats
- Diagnosis by DiffQuik of blood smears
– Short rods or cocci which stain deep purple
– Associated with RBC
– Intravascular haemolysis resulting in anaemia and ill-thrift
– Feline Infectious Anaemia
– Fleas play a role as vectors
– Ectoparasite control is important !!!
Mycoplasma
Prevention, control and treatment
vaccination
live attenuation
eradicate through serological tsting and culling
Pathogen free herds and flocks
– General management factors can help reduce
severity and spread
– Stress, stocking density, nutrition and
concurrent disease
– Can’t use penicillin (no cell wall), drug of choice
is tetracycline (not reliant on cell wall synthesis
for its activity)
– Water medication in pigs and poultry common
when endemic to control spread
– Ectoparasite control for the haemophilic mycoplasma important
Coxiella burnetii
– Obligate intracellular parasite
– Small pleomorphic rods
– Non motile
endotoxins
From cattle, sheep and goats
- relativly resistant in the environment
Q Fever
Transmission
– Shed in birth fluid of cattle, sheep and goats
– Found in milk, urine and faeces
– Aerosol and ingestion result in human infections
Prevention and control
– Occupation hazard
– Protective clothing and masks
– Vaccine available for humans – single shot
* Live attenuate vaccine grown in eggs
* YOU ALL SHOULD BE VACCINATED AGAINST THIS
– Preventative tick treatment of pets and livestock
– Prophylactic treatment of pregnant or lactating animals ??
* Minimise exposure ??
* Infectious dose may be as low as 1 cell per
humans ??
Treatment
– Long term tetracyclines
– Acidic intracellular environment reduces antimicrobial efficiency ?
Genus : Bacillus
– Large Gram + rods
– Facultative anaerobes
– Catalase +
– Endospore forming
– Aerobic condition
– Centrally located
– Free – living in the environment
– Saprophyte
– 2 species of importance
– B. cereus
* Acute mastitis and food poisoning in humans
– B. anthracis
* Anthrax
Exotoxin complex
– Protective antigen (PA) channel forming protein
* Required for activity of other toxins
– Oedema factor (EF) calmodulin-dependent adenylate cyclase
* Increase cAMP → electrolytic and fluid loss
– Lethal factor (LF) metalloprotease cleaves MAPK (mitogen activated protein kinase)
* Disruption of signalling pathways of macrophages
* Massive IL-1 release from macrophages
* Inflammatory cascade
– LF together with PA form lethal toxin
– EF together with PA form oedema toxin
Anthrax host factors
Acute septicaemia
vaccination is effective in preventing disease
