Infectious Disease

Question 1

Incubation period

Answer 1

The phase during which the pathogen begins active replication
No sign or symptoms of infection

Salmonella incubation 6-8 hr
Hepatitis B 50-180 days

Question 2

Prodromal Stage

Answer 2

Initial appearance of clinical manifestation, which are normally mild.

Question 3

Invasion

Answer 3

Rapid multiplication of the organism and activation of the immune and inflammatory responses.

Person will begin having organism specific clinical manifestations and inflammation.

Question 4

Convalescence

Answer 4

Characterized by containment of the infection and resolution of clinical manifestations.

Question 5

Bacteria structure

Answer 5

Prokaryote, unicellular
Have a cytoplasm, ribosomes, lipid plasma membrane and outer cell wall made of peptidoglycan (sugar and peptides), single DNA strand and RNA

Multi shaped
Capsules extra layer of protection
Plasmids: extra DNA for genes that are drug resistant and toxin production
Pili and glycocalyx layer to attach to host
Spores allow for bacteria to become dormant

Question 6

Gram negative bacteria

Answer 6

Bacteria that is resistance to gram stain, thin cell walls that lyse and release endotoxins and cause fever, hypotension, DIC and septic shock and not neutralized by antibiotics.

Gram negative bacteria is more resistance to antibiotics —> have an extra cell membrane layer

Ex: Neisseria, gonorrhea, meningitis, salmonella, shigella, and Klebsiella.

Question 7

Gram positive bacteria

Answer 7

Retain purple stain, lack of extra cell membrane and release exotoxins : type I, type II and type III.

Type I: exotoxins react with MCH class II proteins and stimulate over production and release of pro inflammatory cytokines. Responsible for food poisoning, toxic shock syndrome, scarlet fever.

Type II: exotoxins cause damage to the cellular membrane. Responsible for gangrene.

Type III: toxin enter the cell and cause damage this can be found in clostridium species and shigella.

Ex: staph, strep bacillus (anthrax) and clostridium (tetanus)

Teichoic acid which helps to protect from the complement mediated lysis.

Question 8

Acid fast bacilli

Answer 8

Extremely thick cell wall, grow extremely slow due to lack of nutrients
Ex: TB, (M. Leprae) leprosy, M. Avium ( mycobacterium avium complex)

Question 9

Group A Beta Streptococcal

Answer 9

Streptococcus pyogenes

Causes: strep throat, scarlet fever, rheumatic fever, and post strep glomerulonephritis.

-Hyaluronic acid capsules —> prevent phagocytosis
-M protein in cell membrane —> prevent phagocytosis
-Streptokinase —> activates plasmin —> dissolves clots and prevent clot formation
-Streptolysin O —> kills RBCs and WBCs 

Exotoxin A: cause toxic shock syndrome and scarlet fever

Extremely virulent bacteria diffuse into tissues —> lymph system and blood

Question 10

Group B Beta Streptococcal

Answer 10

Found in the vagina and lower GI tract

Causes: neonatal meningitis, bacteremia of the skin and soft tissues, respiratory tract infections and genitourinary infections.

Risk factors: elderly, immune compromised, CA, DM, age, cirrhosis, corticosteroid use and HIV.

Question 11

Enterococci streptococci bacteria

Answer 11

Two types Faecalis and faecium apart of normal flora.
Transmitted via direct contact mainly HC personae
Site of infection: urinary tract, wounds, biliary tract, and blood.

This bacteria contains penicillinase —> resistant against PCN, cephalosporins, and monobactams.

Treatment: Ampicillin and an aminoglycoside

Question 12

Vancomycin Resistant Enterococci (VRE)

Answer 12

Resistant to vancomycin —> due to multiple phenotypes
Common nosocomial infection
Risk factors: recent vancomycin use, cephalosporin or fluoroquinolones, ICU admit, critically ill and prolonged hospitalization

Question 13

Staphylococcus Aureus / MRSA

Answer 13

Methicillin Resistant Staphylococcus Aureus
Gram positive bacteria usually causes HAIs and skin and soft tissue infections.
Part of normal flora and transferred via direct contact, found on nares and skin.

Surface proteins that attach to the epithelium and tissues causing infection. Protein A binds with IgG and mask bacteria from antibody.

Makes coagulase which makes clots on the exterior —> hiding from immune system

Risk factors: recent antibiotic use, prolonged hospitalization, nursing home, invasive medical devices and dialysis patients.

Makes B-lactamase, mecA gene, AMEs, vanA gene and spontaneous rRNA mutations

Resistant against penicillin, methicillin, aminoglycosides, and vancomycin

Question 14

Escherichia coli (E. Coli)

Answer 14

Gram negative bacteria found in normal gut flora
Causes many infections in multiple organs
Ex: diarrhea, hemolytic uremic syndrome and UTI

E. Coli leading cause of infant meningitis

EPEC (Enteropathogenic E. Coli)
-diarrhea in infants in developing countries

Enterotoxigenic E. coli —> traveler’s diarrhea

Shiga toxin (STEC) —> hemorrhagic colitis

Question 15

Antibiotic resistance

Answer 15

Using antibiotics for viral infections and eating antibiotic fed meats

B- lactamase enzymes —> ESBL, carbapenemases, Amp C. B-lactamase
All bacterial enzymes decrease B- lactamase antibiotic effectiveness.

Genes made by bacteria
NDM gene, colistin resistant 1 gene (mcr-1)

Changes in cell wall permeability preventing antibiotics from entering cells

Question 16

Virus Structure

Answer 16

Small pathogens, can infect any cell including other microbes and viruses
Protein coat called capsid that protects viral DNA/RNA and facilitates attachment to host cell.

Don’t have their own metabolism unable to replicate without a host, viruses incorporate their own genetic material into the host and force them to replicate.

Viral replication can be immediate or dormant inside the cell.
Ex: herpes virus, varicella chicken pox —> shingles

Question 17

Vaccines

Answer 17

Designed to induce immunity to an antigen

MMR and Hep B vaccine not effective in 10% of those who get it
Flu vaccine only protects 30-40% of adults 65 or older

Vaccination immunity not long lasting vs getting actual antigen, boosters may be needed due to this

Vaccines eradicated small pox and polio through herd immunity —> 85% of the population needs to be vaccinated for the whole population to be protected

Measles and whopping cough outbreak —> antivaxers thinking thimerosal causing autism

Attenuated/live vaccines can cause person to shed the virus and infection someone else

Vaccines also protect against bacterial infections
—> pneumococcus, diphtheria, cholera, pertussis, and tetanus.

Question 18

Fungi structure

Answer 18

Large organisms found in every habitat on earth and live on human flora
Single celled with thick cell walls —> resistant against PCN and cephalosporins

Mycosis disease are usually mild except when they are caused by opportunistic infections.

When they invade the hair, skin, or nails they are called dermatophytes
—> disease called Tineas
—>Capitis (scalp), tinea pedis (feet) tinea cruis (jock itch)

Main types are yeast and mold

Question 19

Candida (yeast)

Answer 19

Candida Albicans —> most common fungal infection, part of normal flora: skin, GI and mucous membranes
Reproduces by budding —> cell dividing into two identical daughter cells

Invasive candida —> indwelling catheters, IV’s or PD Caths

Candida infections can be local or disseminated
—> causing abscesses on the kidneys, brain or liver. Shock, DIC, and death.

Special adhesion factors which permit it to bind to implanted devices, epithelium, extracellular matrix, leukocytes which facilitate tissue invasion

Question 20

Mycotoxicosis

Answer 20

Disease via ingestion of fungal toxins
Amanita mushrooms —> hepatotoxins —> liver failure (more common in foreign countries)
Trt: liver transplant and dialysis

Aspergillus Flavus produces aflatoxins which are hepatotoxic and tumor causing
—> infected by eating spoiled grains and peanuts

Question 21

Influenza

Answer 21

Acute self-limiting, febrile viral illness of the upper and lower respiratory tract

At risk: very young, old, chronically ill, debilitated, and immunocompromised
H1N1 - surface viral proteins (neuraminiase and hemagglutinin)

Flu virus is a single stranded RNA virus
Transmitted through airborne respiratory droplets and direct contact with infected items

Viral shedding
Adults 3-5 days
Kids 10 days

Incubation 1-4 days

S/S: fever, myalgias, malaise, dry cough, and headaches.

Bacterial PNA—> bronchitis, viral PNA, febrile seizures, encephalitis, and myocarditis

Question 22

Measles

Answer 22

Viral infection caused by rubeola virus
Systemic infection causing immunosuppression
Human are the only known host
Incubation 6-19 days
Contagious 5 days before rash and 4 days after rash
Spread via respiratory droplet and survives in the air/surface for 2 hours

S/S: fever, malaise, anorexia, conjuntivitis, cough, rash, & photophobia

Complications: diarrhea, encephalitis, systemic immune suppression, PNA —> leading cause of death
Rash starts in buccal mucosa opposite of molars and face to truck spread
Risk groups: pregnant women and immunosuppressed population

Question 23

Colonization

Answer 23

Presence of a microbe in a host with growth and replication without interaction between the microbe or host (no immune response)

Question 24

Invasion

Answer 24

Entry of a microorganism into a non-phagocytic cell (epithelial, endothelial etc.) benefiting the pathogenic bacteria/organisms

Question 25

Multiplication

Answer 25

A virus/organism must first infection a cell to multiply

Question 26

Spread

Answer 26

How a microorganism infections other host or infects other cells through out the body

Question 27

Communicability

Answer 27

The time during which an infective agent is spread directly or indirectly from an infected person to another

Question 28

Immunogenicity

Answer 28

The ability of cells/tissues to provoke an immune response

The ability for a foreign substance to provoke an immune response (usually undesirable)