Chapter 14 microbio

Infection

Microbes enter and multiply in the body.

Disease

Infection causes changes to normal health.

Pathology

Study of disease

Pathogenesis

How a disease develops

Microbiome

Community of microbes living in and on the body.

Normal microbiota

Microbes that normally live in the body

Transient microbiota

Microbes that stay temporarily

Opportunistic pathogens

Normally harmless microbes that cause disease under certain conditions

Commensalism (Type of symbiosis)

One benefits; the other is unaffected.

Mutualism (Type of symbiosis)

Both benefit

Parasitism (Type of symbiosis)

One benefits while the host is harmed

symbiosis

a close, long-term interaction between two different species

Microbial antagonism

Normal microbes prevent harmful microbes from growing by competing for nutrients or producing inhibitory substances.

Koch's Postulates (used to connect a specific microbe to a specific disease)

1. Microbe is present in diseased hosts.

2. Isolate and grow it in pure culture.

3. Introduce it into a healthy susceptible animal; it causes the same disease.

4. Re-isolate the same microbe.

limitations of koch's Postulates

Some microbes cannot be grown in labs, some diseases have multiple causes, and ethical restrictions apply.

Signs

Objective, measurable changes (fever, swelling)

Symptoms

Subjective feelings (pain, fatigue)

Syndrome

Group of signs and symptoms occurring together

Communicable (disease pattern)

Can spread between hosts

Contagious (disease pattern)

Spreads easily.

Noncommunicable (disease pattern)

Does not spread between people

Incidence (how common is the disease?)

Number of new cases

Prevalence (how common is the disease?)

Total existing cases (old + new)

Sporadic

Occasional cases

Endemic

Constantly present.

Epidemic

Sudden increase in cases in an area.

Pandemic

Epidemic spread worldwide

Herd immunity

 Enough people are immune to slow disease spread.

Incubation ( 1st Stage of Infectious Disease)

Infection occurs; no symptoms yet.

Prodromal (2nd stage of infectious disease)

Mild, early symptoms

illness (3rd stage of infectious disease)

Most severe symptoms

Decline (4th stage of infectious disease)

Symptoms decrease

Convalescence (5th stage of infectious disease)

recovery

reserviors of infection

Places where pathogens live and multiply.

What are the reservoirs for humans?

Sick people or carriers.

What are the reservoirs for animals?

Animals that carry pathogens.

What are the reservoirs for nonliving things?

Soil, water, and food.

What are the reservoirs for a carrier?

Has a pathogen but may not show symptoms.

What are the reservoirs for zoonosis?

Disease transmitted from animals to humans.

Direct (contact transmission)

Touching, kissing, and sexual contact.

Indirect (contact transmission)

Contaminated objects (fomites)

Droplet (contact transmission)

Coughing or sneezing; short distances

waterborne (vehicle transmission)

Contaminated water

Foodborne (vehicle transmission)

Contaminated food

Airborne (vehicle transmission)

Tiny particles that travel through air over longer distances

Vector (vector transmission)

Living organism that carries pathogens.

Mechanical (vector transmission)

Passively carries microbes

Biological (vector transmisson)

Pathogen reproduces inside the vector

Healthcare-Associated Infections (HAIs)

Infections acquired in healthcare settings.

• Risk factors: Weakened patients, contaminated equipment, and transmission between people.

• Examples: MRSA and C. difficile.

disease prevention

• Hand hygiene.

• Gloves, gowns, and masks.

• Disinfect equipment.

• Follow standard and transmission-based precautions.

Contact precaution

Gloves and gowns.

droplet precaution

mask

airborne precautions

Special ventilation and N95 respirators.

Emerging diseases

New diseases or diseases increasing in frequency

causes of emerging disease

• Microbial mutations.

• Antibiotic resistance.

• Climate change.

• Travel and trade.

• Environmental changes.

• Decreased vaccination.

organizations that monitor disease

CDC, WHO, NIH

Epidemiology

Study of disease patterns, causes, and spread in populations.

John Snow (scientist)

Traced a cholera outbreak to contaminated water

Ignaz Semmelweis (scientist)

Showed handwashing reduced childbirth infections

Florence Nightingale (scientist)

Used statistics to improve hospital sanitation

Descriptive (types of epidemiology)

Who, where, and when?

Analytical (types of epidemiology)

Why did it happen?

Experimental (types of epidemiology)

Tests a possible cause or treatment.

Case-control study

Compares sick people with healthy people

Cohort study

Follows groups over time

Disease Reporting

• Certain infectious diseases must be reported to public health agencies.

• The CDC tracks disease patterns and outbreaks.

• MMWR: CDC report that tracks morbidity and mortality.