Microbiology Final

(study other sets for cumulative section)

Pathogenesis

process by which pathogen causes a disease

Pathogenesis

entry into the host, attachment colonization, avoidance of immune system, cause damage to host, exit from host, virulence factors

Virulence factors

various features which help pathogen accomplish these goals

Genomic Island

A region of a bacterial chromosome that was acquired recently through horizontal gene transfer; possess a GC content that is different from the rest of the genome

Pathogenicity Island

A genomic island that contains virulence factors; absent in closely related non-pathogens

clearance

pathogens must bind to specific target tissues to avoid __

Pili (fimbriae)

a protein extension made up of the subunit pilin; tip is an adhesion protein that binds to host cell receptors; tip is assembled first, then extended away from the cell by addition of monomers at the bottom

Type I Pili

static hair like appendages only used for attachment

Type IV Pili

can extend and retract; used for twitching motility

Non-pili adhesions

other molecules that can attach to surfaces but are not composed of pilin; a mixture of protein, carbohydrate, and lipid molecules

Biofilm

can help organisms adhere surfaces; matrix sticks to surfaces and protects bacteria from harmful chemicals; are difficult to remove from surfaces, which is a contributing issue for hospital-acquired infections

Capsule prevents phagocytosis, vary surface antigen structure to evade detection, bind antibodies, secrete fake cytokines, manipulate cytokine production

Factors that help hide pathogens from the immune system

Intracellular pathogens

some pathogens grow within host cells to avoid the immune system; some replicate within phagosomes since they possess enzymes that neutralize digestive enzymes; some break out of phagosomes; some prevent digestive enzymes contained in lysosomes from fusing with phagosome

Facultative pathogens

can survive inside or outside of host cells (ex. Salmonella); intracellular

Obligate pathogens

Intracellular; can only reproduce inside of host cells (ex. Rickettsia)

Immunopathology

damage to host tissue caused by the immune response

Exotoxins

secreted molecules that have a wide variety of effects on target cells; proteins; can disrupt plasma membrane, protein synthesis, adhesion, signal transduction, and cell cycle; block exocytosis; redirect vesicle traffic

AB toxin

an exotoxin composed of two distinct protein molecules; A is toxic; B delivers A into target cell; have 5 B subunits around 1 A

Anthrax toxin (Bacillus anthracis)

has two separate A subunits; B antigen is called the protective antigen; edema factor causes fluid loss from target cells; lethal factor cripples the immune response

Type II toxin secretion system

evolved from type IV pili (twitching motility); toxin molecule is loaded into the system, which then acts like a piston to push the molecule out of the cell

Type III toxin secretion system

Syringe system used to directly inject toxin into host cells; Samonella uses this system to disrupt intestinal epithelial cell ion regulation

Type IV toxin secretion system

evolved from conjugation system; tube that allows toxin to diffuse out of the cell from the cytoplasm

Endotoxins

Lipopolysaccharides part of the outer membrane of Gram-negative cells; released upon death; induce fever, activate clotting factors, vasodilation, shock and death may occur if endotoxins enter blood

Alter cytokine production, interfere with MHC-I presentation, inhibit apoptosis, increase host cell division, enter latency to hide from immune system, infect immune cells directly

Ways viruses have evolved to subvert the immune system

Rhinovirus

Naked ssRNA+; pathogen that causes colds; over 100 serotypes that have distinct antigens compared to other serotypes

Antigen variation

immunity to one serotype does not grant immunity to others (antibodies will not bind)

Influenza virus

Enveloped ssRNA; segmented genome (8 discrete pieces of DNA); different strains can infect various mammals and birds

Antigenic drift

random mutations during genome replication result in small changes in virus proteins that add up over time; viruses mutate much faster than cells because they lack repair enzymes

Antigenic shift

unique to influenza; different strains of the virus can co-infect the same cell

HIV

enveloped ssRNA+; retrovirus converts RNA to a DNA molecule which integrates into host genome; infects TH cells by binding to CD4 and CCR-5 receptors

Human Papillomavirus (HPV)

naked dsDNA; common cause of genital warts; viral proteins E7 inhibits regulation of mitosis, which can lead to cancer; most common cause of cervical cancers

Herpes simplex virus (HSV-1 and 2)

enveloped dsDNA; cause of cold sores (1) or genital herpes (2); during primary infection, can become latent in host neurons or white blood cells; 50% of humans have a latent infection of this

Protozoan Pathogenesis

exhibit antigen variation, with different life cycle stages of the same pathogen often presenting different antigens; others coat themselves in host antigens to evade immune detection; others induce secretion of anti-inflammatory cytokines to reduce the effectiveness of the host immune response b

Integumentary system

skin, hair, nails, cutaneous glands

Epidermis

region of the skin; superficial, avascular, multiple layers of keratinocytes, some immune cells

Dermis

region of the skin; deep thick area containing accessory organs

Exanthem

widespread skin rash accompanied by systemic symptoms

Enanthem

rash on mucous membranes

Macular

flat and red rash

Papular

small, solid, and elevated

Maculopapular

a reddened popular rash

Vesicular

formation of small blisters

Cutibacterium acnes

pathogen causing acne

Acne

an immune response to the presence of cutibacterium acnes, excessive oil production, and hormones; more common during adolescence when hormone production is high

Black/Whiteheads

blockage of hair follicles and sweat/oil glands on the skin cause __

Staphylococcus app or S. aureus

pathogen that causes staphylococcal diseases

Staphylococcal Diseases

various lesions or boils that form as immune cells attack pathogens that have invaded areas of the dermis through either pores/hair follicles, or damaged areas of the skin

Abscess

(Staphylococcus) confined, pus-filled skin lesion

Folliculitis

(Staphylococcus) lesion at the base of a hair follicle

Furuncle

(Staphylococcus) larger, painful boil

Carbuncle

(Staphylococcus) multiple, connected furuncles

Impetigo

(Staphylococcus) superficial blisters, highly contagious (S. aureus)

Scalded skin syndrome

(Staphylococcus) most common in children less than 5; toxins cause desquamation (S. aureus)

Desquamation

shedding of outer layer of skin, superficially looks like 2nd degree burns

Toxic Shock Syndrome

(Staphylococcus and Streptococcus) a systemic disease which occurs when S. aureus toxins enter the blood stream; massive inflammatory response causes fever, vomiting, diarrhea, aches, sunburn, rash, sudden low blood pressure, and heart failure

Various Streptococcus spp.

pathogen causing streptococcus diseases

Cellulitis

(Streptococcus disease) severe, fast spreading infection of dermis and subcutaneous tissue

Erysipelas

(Streptococcus disease) Superficial cellulitis (upper dermis)

Necrotizing fasciitis

(Streptococcus disease) destruction of muscle, fat, and soft tissue by strep toxins; amputation may be required to prevent spread

Clostridium perfringens

pathogen causing Gas Gangrene

Gas Gangrene

acquired from soil contaminating wound; multiple toxins cause tissue death, gas production by microbes produce foul smell

Herpes Simplex

dsDNA viruses; 1 causes cold sores, fluid filled blisters on the skin; enters nerves of haw and goes dormant; can reactivate due to stress/trauma

Chickenpox

varicella-zoster virus, vesicular rash with blisters filled with fluid

Shingles

reactivation of VZV in adults, icepick pains and vesicular rash encircling trunk, can cause long term pain (years) if virus enters nerves

measles virus (paramyxoviridae family, RNA)

pathogen causing measles

Measles

hacking cough, runny nose, high fever, Kolpik spots in mouth, full body rash; highly contagious through respiratory droplets; capable of destroying immune memory cells, adaptive immunity

Rubella virus (+ sense RNA)

pathogen causing rubella (German measles)

Rubella (German measles)

fever, runny nose, swollen lymph nodes, full body rash; can induce miscarriage or birth defects in pregnant women

Human parvovirus B19

pathogen causing fifth disease (erythema infectious)

Fifth disease (Erythema infectiosum)

replicates within erythrocyte progenitor cells, then spreads via blood; slapped cheek rash is followed by popular rash on the throat or palate; maculopapular rash forms on body and limb (lace rash)

HHV-6, HHV-7

pathogen causing Roseola infantum

Roseola infantum

transmitted via saliva or respiratory secretions; symptoms in children less than 3 years old; high fever followed by maculopapular rash that blanches when touched; many people carry latent infection

HPV-1, HPV-2

pathogen causing warts

Warts

growths form at infected skin; area is typically frozen, and dead cells physically removed

Variola virus

pathogen causing smallpox

Smallpox

high fever, vomiting, weakness, macules on body; extinct; eradicated due to global vaccination campaign; achievable because the virus only infects humans, no other reservoirs

Dermatophytosis

fungal disease of skin, hair, or nails

Microsporum, trichophyton, epidermophyton spp.

pathogens causing fungal infections

ringworm

Leishmania spp (protozoan)

pathogen of leishmaniasis

Leishmaniasis

transmitted through insect bite (sand fly); painful sore around bite wound; resembles volcano

Many, both bacteria and viruses, can also be caused by chemicals or allergens

pathogens of conjunctivitis

Conjunctivitis

inflammation of the protective mucous membrane lining the eye (pink eye)

Bacterial conjunctivitis

primarily Staphylococcus and Streptococcus spp; dilation of blood vessels to make eye appear red, profuse pus production

Neonatal conjunctivitis

Neisseria gonorrhoea or chlamydia trachomatis, acquired vertically during childbirth, can potentially lead to blindness if not immediately treated

Trachomatis

chlamydia trachomatis, leading cause of preventable blindness, transmitted person to person, via flies, or through fomites, nodules form in conjunctiva

Upper respiratory tract

most common portal of entry for pathogens; includes nose, sinuses, pharynx, and larynx

pharynx

The ciliated epithelial cells of the URT perform mucociliary clearance; mucus traps particles including pathogens, cilia move mucus to the ___, where it is coughed or sneezed out

URT

home to a robust microbiome, that competes with pathogens for space and nutrients; antibiotic treatment can kill some native microbes allowing for potential pathogens to overgrow (dysbiosis)

Strep throat

inflammation of the pharynx (pharyngitis) can be the symptom of either viral or bacterial infections; 20% of cases are caused by Streptococcus pyogenes; transmitted via airborne droplets or contaminated fomites; headache, fever, swollen lymph nodes/tonsils

Scarlet fever

arises in 10% of cases of strep throat due to presence of erythrogenic toxins carried by some S. pyogenes strains; causes upper body rash and swollen strawberry tongue

Rheumatic fever

untreated strep throat can progress to this autoimmune disorder, which causes inflammation of the heart, joints, nervous system, and skin

Corynebacterium diptheriae

bacteria causing diphtheria

Diptheria

transmitted by airborne droplets or direct contact with infected skin/membrane; sore throat, fever, pseudomembrane forms on tonsils composed of dead tissue, immune cells, mucus, and connective tissue; damage to heart or nerves possible if bacteria spread; prevented by DTaP vaccine

Middle ear infection

ear cavities connected to nasopharynx via eustachian tubes; usually start as a viral infection, but bacterial pathogens can follow once the immune system is occupied dealing with the viruses; biofilm formation in ear fluid, inflammation of the ear drum, possible fever, headache

Common cold

most common infectious disease worldwide

Rhinoviruses

small, +sense RNA viruses with hundreds of different subtypes; sneezing, sore throat, runny/stuffy nose, mild aches, cough; transmitted through airborne droplets or contaminated fomites

Bordetella pertussis (bacterium)

pathogen of whooping cough

Whooping cough

cells bind to cilia, then secrete toxin that paralyzes cilia and prevents clearance; transmitted through airborne droplets

Catarrhal stage

most contagious stage of whooping cough, symptoms like cold