Microbiology: Chapter 13 Microbe-Human Interactions: infection and disease

When microbes colonize the body, they ____

-can becomes part of the normal flora

-can cause infection and disease`

What is normal flora?

native microbes that hang out in the body

What are examples of normal flora?

bacteria, fungi, viruses

When do humans start to aquire microbes?

newborns

Where does normal flora like to hang out?

skin, mucous membranes, upper respiratory tract, Gi, vagina, external ear canal, external eye

Where is normal flora microbe free?

all internal tissue and organs

Usually, the effects of normal flora can be ____ or ____

protective, nutritional

Most microbes are harmless as long as they _________

don’t penetrate superficial skin barriers

Members of normal flora become infectious when?

the health of the host is compromised (AIDS)

When is the uterus and contents sterile?

during embryonic and fetal development

When does comprehensive exposure to microbes occur during the birthing process?

when the baby comes into contact with the birth canal

Within 8 to 12 hours after delivery, the newborn has been colonized by what bacteria?

streptococci, staphylococci, lactobacilli

Normal resident flora-

always present regardless of hygiene

Normal translet flora-

influenced by hygiene

Normal resident flora in SKIN

staphylococcus, micrococcus, mycobacterium. fungi= malassezia yeast

Normal resident flora in ORAL CAVITY

streptococcus, staphylococcus, lactobacillus, treponema. Fungi= candida species

Normal resident flora in LARGE INTESTINE RECTUM

Bacteroides, decal streptococci, lactobacillus, E. coli. Fungi= Candida

Normal resident flora in UPPER RESPIRATORY TRACT

same as oral cavity

Normal resident flora in GENITAL TRACT

lactobacillus, streptococcus, mycobacterium. Fungi = candida

Normal resident flora in URINARY TRACT

staphylococcus, streptococcus, E.coli

Oily skin -

bacteria growth

Dry skin -

cracks and allows microbes in

Transient population -

clings to the skin but does not ordinarily grow there

How is transient population formed?

acquired by routine contact, influenced by hygiene

Resident population -

lives & multiplies in the deeper layers of the epidermis and in the glands and hair follicles

Where are microbes found in the mouth?

cheek epithelium, tongue, floor of mouth, tooth enamel

What bacteria is found in the mouth?

streprococcus species (S.salivarius)

Is mouthwash effective?

No

Why is the human bite dangerous?

the mouth has many microbes, when the bite goes through the skin microbes from your mouth can enter into the bloodstream

What is the predominant flora of bacteria found in the colon?

Bacteroides, clostridium

What are coliforms?

gram negative, lactose fermenting microbes, facultatively anaerobic

What are the events in an infection?

1. Microbes enter the body

2. attaches itself

3. invades (crosses host barriers)

4. multiplies in a target tissue

5. released

The type and severity of an infection depends on what two factors?

-Microbes potential to cause an infection or disease

-The condition of the host

What is a true pathogen?

capable of causing infection and disease in healthy persons with normal immune defenses

What is an opportunistic pathogen?

causes disease when the hosts defenses are compromised or when they become established in a part of the body that is not natural to them

Factors that weaken Host defenses: Old age & extreme youth

Co-morbidities and other health issues

Factors that weaken Host defenses: Genetic defects in immunity

T helper cells destroyed by HIV

Factors that weaken Host defenses: Surgery and organ tranplants

Recieves amino suppressant drugs

Factors that weaken Host defenses: Cammcer, liver issues, diabetes

Uncontrolled diabetes= too much glucose

Factors that weaken Host defenses: Chemotherapy/immunosuppressive drugs

chemotherapy suppresses bone marrow, can’t make white blood cells

Factors that weaken Host defenses: Physical and mental stress

Increase production of cytokines when asleep

What is the CDC Biosafety Categories for Pathogens?

system based on their degree of pathogenicity and relative danger in handling them

CDC categories: Level 1

microbes that do not cause disease (micrococcus luteus)

CDC categories: Level 2

moderate risk agents (staphylococcus aureus)

CDC categories: Level 3

readily transmitted & virulent agents (mycobacterium tuberculosis)

CDC categories: Level 4

deadly pathogens (rabies & Ebola fever viruses)

What is pathogenicity?

the potential to cause an infection

Virulence-

takes into account the ability of microbes to invade a host and produce toxins (properties = virulence factors)

To initiate an infection, a microbe ____

enters the tissues of the body by a characteristic route, the portal of entry

Exogenous -

originating from a source outside the body (environment, person, animal)

Endogenous -

already existing on or in the body (normal flora or latent infection)

Where are the portals of entry on the skin?

nicks, punctures (herpes simplex)

Where are the portals of entry on the GI tract?

pathogens in food, drink, adapted to survive digestive enzymes & pH changes (salmonella)

Where are the portals of entry on the respiratory tract?

oral and nasal cavities (streptococcal sore throat, common cold, PN= streptococcus)

Where are the portals of entry on the urogenital tract?

contracted by sexual means, chlamydia, HIV

What are virulence factors?

the adaptions a microbe uses to invade & establish itself in a host

Virulence factors include:

exoenzymes, toxins, antiphagocytic factors

Why do many pathogenic bacteria like fungi, protozoa and worms secrete exoenzymes?

to break down and inflict damage on tissues or enzymes that dissolve the hosts defense barriers

What are examples of exoenzymes?

keratinase: breaks down keratin

collagenase: breaks down collagen

Specialized receptors are _______

glycoprotein spikes

What is a toxin?

A specific chemical product of microbes that is poisonous to other organisms

What is an exotoxin?

an unbound toxin molecule secreted by a living bacterial cell into the infected tissue

What is an endotoxin?

A toxin that is not secreted but is released only after a cell is damaged or lysed

Exotoxins toxicity-

minute amounts

Endotoxins toxicity-

high doses

Exotoxins effect on body-

specific to a cell type (blood, liver, nerve)

Endotoxins effect on body-

systemic: fever, inflammation

Exotoxins manner of release-

secreted from live cell

Endotoxins manner of release-

released by cell during lysis

Exotoxins sources-

Gram positive and negative

Endotoxins sources-

all gram negative (E.coli)

Exotoxins immune response-

stimulate antitoxins

Endotoxins immune responde-

do not stimulate antitoxins

   How does Streptococcus pneumonia escape phagocytosis?

Secretes an extracellular surface layer that makes it difficult for the phagocyte to engulf them

How do streptococcus & staphylococcus escape phagocytosis?

they produce leukocidin, substances that are toxic to white blood cells

What are Anti phagocytosis factors?

used by some pathogens to avoid certain white blood cells called phagocytes

What is necrosis?

cell death due to a disease

What is a localized infection?

when the microbe enters the body & remains confined to a specific tissue (boils, skin infections)

What is a sysemic infection?

when the infection spreads to several sites & through tissue fluids like the bloodstream

What is an acute infection?

infection that comes on quickly, with severe BUT short lived effects

What is a chronic infection?

persists over a long period of time

What is a primary infection?

intial infection, chicken pox

What is a secondary infection?

another infection caused by a different microbe (staphylococcus aureus)

What happens at the incubation period?

initial contact with the infectious agents to the appearance of the first symptoms (2-30 days), multiplies at portal of entry

What happens at the prodromal stage?

earliest notable symptoms (1-2 days), discomfort

What happens at the period of invasion?

infectious agents multiply at high levels (fever, more specific signs, length varies)

What happens at the convalescent period?

Immune system fights back to become health again

What happens at the terminal period?

infection results in death

What are latent viruses?

Viruses that switch from active → inactive then back again

Describe the herpes zoster virus-

1st get = chicken pox

Inactive state, hides in neurons

Goes back into active state = shingles

What is a sign?

any objective evidence of disease as noted by an observer

What is a symptom?

subjective evidence of a disease as sensed by a patient

Signs and symptoms of inflamattion-

signs: edema, swollen lymph nodes

symptoms: fever, pain

Signs and symptoms of an infection in blood-

signs: leukocytosis, leukopenia

symptoms: headache

Define asymptomatic/subclinical-

terms used to describe an infection that produces no noticeable symptoms

Pathogens depart by a specific avenue called the _____

portal of exit

What are the exits for microbes to leave the host?

coughing, sneezing, skin cells, urine, insect bite, blood, feces, vaginal discharge or semen