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Microbio > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Saprophytes

A

AKA saprobes
Microbes that feed off dead/decaying tissues
Not a true “pathogen” because the host/tissue was already damaged

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2
Q

Pathogenic heterotrophs

A

Pathogens that feed off living cells/tissues
In process of feeding, will cause damage to the host
damage to cells releases more nutrients
Pathogens live in or on the host
can be outside the host cell or live inside the host cell

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3
Q

Intracellular pathogens

A

Intracellular pathogens exist inside the host cell
All viruses are intracellular pathogens
Only some bacteria are intracellular pathogens

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4
Q

How much damage can a pathogen cause

A

Pathogens have a negative relationship with their host
Host is being damaged while the pathogen is benefiting
The most successful pathogens have evolved to cause a limited amount of damage to the host
If the host dies, the pathogen no longer benefits
Exception is pathogens that can easily spread to and infect other hosts
These can kill their current host and move on

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5
Q

Primary pathogens

A

Disease-causing microbes with the means to breach the defenses of a healthy host
Can survive natural defensive barriers and initial attack by the immune system and begin replicating

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6
Q

opportunistic pathogens

A

Only cause disease in a host whose immune system is compromised
Very sick, malnourished, internal parasites, on immunosuppressive drugs (steroids, chemotherapy), poor hygiene, pregnant, neonates
Have some ability to cause disease, but require either:
Large number of bacteria to be able to cause damage
A compromised immune system
Opportunistic pathogens are often part of the normal flora in healthy individuals
If the host is immune suppressed, the numbers of microbes cannot be controlled
can easily overwhelm and start to cause disease
Can also be microbes acquired from the environment or from others that normally cause minimal to no disease
cause severe disease because the host is immunosuppressed

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7
Q

Steps of microbial transfer

A

Transmission
Infection
Entry→Attachment→Colonization
Replication
Tissue damage
Spread within host
Spread outside host (transmission to others)

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8
Q

Trasmission

A

SPREAD OF DISEASE
First step of the infectious disease process
Normal flora that can cause disease does not need to be transmitted (already in the host)
All other infectious pathogens must be ACQUIRED through TRANSMISSION

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9
Q

Direct tranmsission

A

Animal to animal
Requires physical contact between the infected animal and the susceptible animal
Microbe does not spend any significant time in the environment
dies readily if away from a host (usually because of drying)
Same household, herd

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10
Q

Types of direct transmission

A

Touching
Kissing
Sexual contact
Contact with body lesions
Contact with bodily fluids
Saliva, blood, vaginal fluids, semen
Aerosol transmission
Respiratory droplets are small drops of nasal or respiratory secretions that travel short-distances
Contain microbes
Usually inhaled or can land on mucous membranes (conjunctiva; nasal mucosa)

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11
Q

Indirect transmission and types

A

Microbe is acquired from a contaminated surface/environment
Microbe has spent some time surviving in the environment
usually microbes are quite resistant
Types of indirect transmission:
Water-borne transmission
Air-borne transmission
Vector-borne transmission

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12
Q

Fomites

A

Any inanimate object that conveys a pathogen from one individual to another
Household
Water and food bowls, contaminated bedding, sinks, toilet bowls
Clinic/Vet
Stethoscopes, thermometers, contaminated wash bottles, intubation tubes, rubber boots, needles, weigh scales, kennels, truck tires
Environment
Dirt, wood, floors, milking equipment, straw bedding

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13
Q

Air-borne transmission

A

Pathogens are carried in evaporated droplets or dust from one location to another through the air
Can travel many kilometers
Usually land on a fomite
Very small, very resistant to drying
Eg. anthrax, influenza, foot-and-mouth

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14
Q

Vector borne transmission

A

Vector = small animal capable of transmitting disease
Usually refers to insects
Most common is mosquito
Also ticks, fleas, flies
Vector itself does not undergo pathology
Carries pathogen from infected to susceptible animal
Cause vector-borne diseases

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15
Q

Fecal oral transmission

A

Organisms found in feces are ingested because of fecal contamination
Can be direct OR indirect
Grooming (grooming fur, anal region, feet)
Ingestion of contaminated food
Ingestion of contaminated water
Ingestion of contaminated soil
Common reason for spread of pathogens from animal feces to people
Parvovirus, Salmonella, pathogenic strains of E. coli

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16
Q

Fecal oral transmission can be reduced by

A

Thorough cooking of food
Frequent and thorough handwashing after handling feces
Protection of water supplies
Keeping feed away from areas with large volume of feces (feed alleys in dairy barns)
Picking up dog feces

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17
Q

Vertical transmission

A

Spread of disease from mother to child
Eg: Bovine viral diarrhea, FIV,
Hepatitis B, Chlamydia, parvovirus
Can be very difficult to control

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18
Q

In utero transmission

A

Pathogen spreads from mother’s blood, via the placenta, to the fetus

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19
Q

Trans-vaginal transmission

A

Neonate is exposed to microbes in the birthing canal
Normal flora and pathogens of the urogenital tract and from any fecal contamination of the birthing canal
Enters via swallowing, through mucous membranes

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20
Q

Nursing vertical transmission

A

Some pathogens can enter the mammary glands and are secreted in colostrum/milk → ingested by neonate

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21
Q

Horizontal transmission

A

Pathogens that are spread by routes other than mother to child
Includes direct and indirect routes
Example: feedlot

22
Q

Nosocomial infection

A

Diseases acquired while in a hospital/clinic
Can be direct or indirect
Aerosols from another patient
Fomites including contaminated bedding, kennels, thermometers
Contaminated fluids (ear washes, saline squirt bottles,reusing IV fluids bags, WATER BATHS)
Nosocomial infections are ALWAYS a concern

23
Q

Nosocomial infections are harder to treat because

A

Microbe has a greater chance of having antimicrobial drug resistance
Bacteria in hospital settings have often been previously exposed to antibiotics at low levels and survived the exposure
Greater chance that the susceptible animal/patient is immunocompromised
Patient more likely to get infected
Patient immune system is compromised so more dependent on drugs to treat

24
Q

Zoonosis

A

Diseases are that passed from ANIMALS TO HUMANS
Can be direct or indirect
Coming into contact with the saliva, blood, urine, or feces of an infected animal
Being bitten by a tick or mosquito (vector)
Eating or drinking something unsafe
Unpasteurized milk, undercooked meat, or unwashed fruits and vegetables that are contaminated with feces from an infected animal
According to the Centers for Disease Control (CDC)
60% of human infectious disease are potential zoonoses
75% of new “Emerging” diseases are zoonotic

25
Q

Important zoonosis

A

Rabies
Salmonella, E. coli, Campylobacter
Toxoplasma gondii, Giardia
Roundworms

26
Q

Endemic

A

An infectious disease that is ALWAYS present in a population at an EXPECTED, LOW LEVEL
Predictable
Continuous
Not major changes
Eg.Seasonal flu, common cold, rabies, distemper

27
Q

Epidemic

A

When there is a sudden increase in the number of cases in a period of time within a population
More cases
Rapidly spreading
Stays within the community

28
Q

Pandemic

A

Widespread epidemic
More cases in short period of time
Spread within the community
Moves to adjacent communities
Pandemics (and epidemics) are usually due to the appearance of a new infectious disease
New species that has entered a different host
New strain that the immune system can’t recognize
New strain with increased pathogenicity
Population lacks prior exposure
Does not have immunity and is much more susceptible

29
Q

Entry stage of infection

A

Whether or not there is infection depends on the number of pathogens that enter the host
Body is surrounded by protective barriers (skin, tears, gastrointestinal mucosa, stomach acid, normal GI flora) that prevent entry
Disruption of barriers (scratches, wounds, inflammatory damage to the respiratory/ urogenital tract, injection, disruption of normal GI flora) increases the chance of entry and adhesion
A minimum number of microbes must enter for disease to occur

30
Q

minimum infectious dose

A

The minimum number of microbes that must enter the host for disease to occur
Eg. Inhaling 5 particles of cold virus will not cause disease but inhaling 10,000 particles of cold virus will
The minimum infectious dose required to cause disease depends on:
Pathogenicity of the microbe
Immune state of the host

31
Q

Attachment stage of infection

A

After microbe enters body →must attach to cells and body surfaces before replication can occur
Bacteria that do not adhere can be washed out (i.e., flushed by urination, peristalsis, tears)
Bacteria attach by:
Fimbriae, pilli, lipopolysaccharide, slime layers
Receptors located on the surface of bacteria recognize and bind to specific receptors on the surface of specific host cells

32
Q

Establishment/colonization stage of infections

A

Once the microbe has attached, it can start to multiply
If the immune system can attack and eliminate the infection faster than the bacteria can replicate, the animal will not become sick
In most cases, if the animal received the minimum infectious dose, the immune system will not be able to clear it fast enough

33
Q

Patogenicity

A

Pathogenicity is the measure of how much tissue damage a microbe can cause
Microbes that do cause damage are called “pathogens”; tissue damage results in disease

34
Q

Direct damage of disease

A

Direct damage is due to an action of the microbe
Bacteria and fungi produce toxins that damage surrounding tissues to:
(1) release nutrients
(2) enable spread to other tissues
Hemolysis causes RBC breakdown to release nutrients
Collagenase breaks down connective tissue so bacteria can spread deeper
Enterotoxins damage the GI barrier so nutrients aren’t absorbed and remain in the GI tract for bacteria to use
Viruses use host cells as “factories for multiplication” and will often kill the cell in order to release the newly formed virus

35
Q

Indirect damage of an microbe

A

Indirect damage occurs when the immune system reacts to the presence of the infectious microbe
When the immune system is activated, there is some degree of inflammation
Inflammation is always non-specific and damage host tissues in the process of destroying the bacteria

36
Q

Disease course

A

The course of a disease is specific to both the pathogen and the host
All infectious diseases follow a similar overall clinical pattern
Infection - entry, attachment, start of multiplication
Incubation period
Prodromal period
Clinical (symptomatic) period
Resolution followed by Convalescence

37
Q

Exposure of infection

A

Animals are exposed to potential pathogens all the time
Exposure does not necessarily cause disease
Microbes have to enter, attach, establish
Possible for the immune system to clear the microbe before it can establish itself, replicate and cause pathology
Ability to cause disease depends on:
Infectious dose
Pathogenicity of the microbe
Immune status of the animal

38
Q

Incubation period of disease

A

TIme between exposure to the pathogen and when clinical signs first appear
Hours, days, weeks, months, years
There are NO clinical signs/symptoms
During this period, pathogen is establishing itself and multiplying - any damage is minimal
The incubation period is specific to every microbe
Eg. Parvovirus 4-7 days
Eg. Rabies virus up to 6 months
Microbes can be shed during incubation

39
Q

Prodromal period of disease

A

Period following incubation when there are non-specific clinical signs
Lethargy, fever, decreased appetite
Animal is “sick”, but clinical signs do not hint at type of disease process that is occurring or indicate where in the body disease is occurring
Pathogen has established itself, but numbers are still low

40
Q

Clinical period of disease

A

AKA Symptomatic period
Period with the highest numbers of infectious organisms
Clinical signs are specific to colonization of a specific tissue and/or specific pathogenic factors that are specific to that organism
Eg. Rabies virus causes neurological symptoms
Eg.Bordetella causes rhinotracheitis
Easiest stage to diagnose

41
Q

Resolution stage of disease

A

Decreasing numbers of the pathogen
a corresponding decrease in the severity of clinical signs
Through the activation of host immune defenses or treatment

42
Q

Convalescence period of disease

A

Period when specific symptoms are GONE
infectious organisms are still present in very low numbers (not sufficient to cause pathology)
Body is still returning to its normal state
At increased risk of re-infection
At increased risk of other disease
Infectious organisms are still present therefore animal can still shed infectious organisms
Shed = Can transmit to others

43
Q

Reinfection

A

The previous infection was completely resolved but same infection has started again from the transmission stage
Usually a sign of an underlying issue (hygiene, immune status, physiological stress)

44
Q

Recurrent

A

Reinfection at weekly to monthly intervals

45
Q

Resistant

A

The original infection was never completely resolved - still present due to failure to treat

46
Q

Chronic symptomatic

A

Infection persists with continued symptomatic disease
Occurs if the host immune response is unable to clear the infection

47
Q

Chronic asymptomatic

A

The infection persists at low levels, low levels of replication but there are no clinical signs
May or may not be able to transmit to others

48
Q

latent infection

A

A form of chronic asymptomatic infection
The infectious organism remains in the host but is not actively replicating nor producing pathogenic factors
Because it is not replicating, there is no risk of transmission
IF the infectious organism is reactivated (starts to replicate and produce pathogenic factors), will return to clinical stage and can transmit to others

49
Q

Remission

A

The clinical signs are temporarily absent
Can stay in remission for short or long periods
It was never cured

50
Q

Relapse

A

Periods when clinical signs are present
Eg. the infectious organism starts to replicate again if latent or starts to produce pathogenic factors

51
Q
A

Microbio (11 decks)

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