-the number of microbes (Salmonella, need a lot; Shigella need a few)

-the environment - heat and an acid environmnt help kill microbes

-time of exposure - spores take longer to kill

-microbial characteristics - gram pos. organisms are easier to kill than gram neg because gram neg have very selective pores. Psuedomonas and Mycobacterium have a waxy cell wall (mycolic acid). Prions are very hard to kill - must be incinerated

-damage the plasma membrane

-damage proteins and nucleic acids (heat & radiation)

-heat

-filtration

-low temperature

-high pressure

-dessication

-osmotic pressure

-radiation

autoclave

pasteurization

sterilization

steam under pressure

121°C at 15 psi for 15 minutes

(may increase some factors to decrease others, ex increase temperature to decrease time)

15 min @ 72°C 

used for milk

-flaming

-hot air sterilization (oven)

-used in ORs and burn wards

membrane filters - the size of the pore dictates which organisms are retained

-Refrigeration is a bacteriostatic for most pathogens. Listeria is an exception

-Freezing can kill some bacteria, but can cause dormancy in others. They can be thawed and grow.

Freezing for 30 days at -5ºC will kill trichinella in pork.

used for juices

spores resist pressure

-removal of water

-many bacteria can survive lyophilization or freeze-drying

-Gonorrhea dies quickly out of the body

-TB can live much longer

-Viruses resist desiccation

-Endospores can live for many years

-high sugar or salt concentration causes water to leave bacterial cells and they die

-molds resist osmotic pressure

mutates DNA

-UV lights are used in hospitals

-microwaves do not destroy bacteria, the heat does

silver - used in impregnated dressing for burns

zinc - mouthwash & dandruff shampoo

sulfur dioxide - in wine

sodium nitrate in hot dogs, ham, sausage, bacon - excellent for preventing growth of Clostridium botulinum spores. May be carcinogenic, so levels have been reduced in foods.

-ethylene oxide + CO₂ used in closed chamber for sterilizing mattresses

-chlorine dioxide used to fumigate buildings infected w/anthrax

compressed CO₂ at 45°C kills bacteria & spores

used on medical implants of bone, tendon & ligament

an organism may be normal flora in one part of the body but pathogenic in another part of the body

an organism, E. coli, is normally found in the intestines, but can cause an infection if it invades the bladder

infection can be latent (inactive)

chicken pox and herpes virus can remain latent in nerve cells for years without causing disease

-Babies are sterile

-Adults can have 1 x 10¹⁴ bacterial cells living in and on them, 10 times more than the number of cells we have!!

-"Normal" varies from person to person

-skin

-eyes (you will never get "normal eye flora" on an eye culture report, tears usually wash away bacteria)

-nose, throat, upper respiratory system

-lungs

-mouth

-intestines

-reproductive system in females

-stomach (sometimes)

-antagonism

-symbiosis

competition between normal flora and pathogens

ex. - E. coli produces proteins that inhibit the growth of Salmonella and Shigella

ex. - Acidophilis spp. lower the pH of the vagina to ~pH 4 so yeast cannot grow

-competing for nutrients

-producing harmful substances

-affecting pH

-affecting oxygen availability

-yeast (Candida) may colonize the mouth and vagina

-Clostridium difficil can infect the intestines (common nocosomial infection)

-commensalism

-mutualism

-parasitism

live bacteria that are ingested or applied that have a beneficial effect

ex - lactic acid bacteria in the intestine inhibit growth of pathogens

-suitable location: bacteria in the intestine can cause infection when in the urinary tract or wounds

-immunosuppressed state: chemotherapy or AIDS. Organism normally present become pathogenic

-after broad spectrum antibiotics

Pnemuocystis jirovecii - in AIDS.  Carriers have a potentially pathogenic organism as normal flora, when passed to another person it is a pathogen and causes pneumonia

Mycobacterium tuberculosis

Neisseria meningitidis (respiratory tract)

Strep. pneumoniae (throat)

A) some diseases are only caused by one organism (ex. syphilis-Trepanoma pallidum, leprosy-Mycobacterium leprae, tetanus - Clostridium tetani)

B) some dieases can be caused by many different organisms (pneumonia, UTIs, sepsin, meningitis)

-acute

-chronic

-latent

develops slowly and lasts

ex. TB, Hep B

symptoms disappear and resurface later

ex. malaria, herpes, checkenpox

-local

-systemic

-septicemia

-primary infection

-secondary infection

-subclinical

in one area

ex. boil, MRSA

spread throughout the body

ex. chickenpox

-bacteremia - bacterial infection in blood

-toxemia - toxins in blood (ex. Strep. pyogenes, E. coli O157:H7, tetanus, botulism)

-viremia - viral infection in blood

opportunist sets in when the body is weak

ex. Pneumocystis jirovecii

genetics

gender

nutrition

age

preexisting illness

chemotherapy

environment - humidity

stress

development of disease:

stage - time - signs & symptoms

incubation - time varies - no symptoms

prodromal - short duration - mild symptoms

illness - time varies - all signs and symptoms

decline - 1 day to several days - symptom decrease

convalescense - can last for years - carriers

humans

animals (zoonoses)

soil

water

Pasturella multocida - cat bites

Rabies - mammals

Malaria - mosquitoes

Tularemia -hamsters

Tapeworms

Leprosy - armadillos

tetanus

Necator americanus (hookworm)

-contact

-vehicles

-vectors

animals that carrry pathogens from one host to another

ex. hoof & mouth disease

-mechanical - insect carry disease on wings or feet

-biological - arthopod bites an infected animal, draws blood. Organism matures. Arthopod bites an uninfected animal and transmit the disease or defecate in open wound

-kill 20,000/yr in the US

-affect 5 - 15% of all hospitalizations

-many bacteria in hospitals are drug resistant

-compromised hosts - broken skin or weak immune systems

hospital personnel

ventilation systems

Pseudomonas

Staph. aureus-MRSA

Clostridium difficil

Enterococcus-multiple drug resistants strains

-urinary tract

-surgical sites

-lower respiratory infections

-handwashing!!!

-alcohol based hand sanitizers not effective agains noroviruses which cause gastroenteritis

-sterile technique

-genetic recombination

-evolution ex. Vibrio cholera O139

-widespread use of antibiotics

-global warming - expanding range of reservoirs

-transportation

attempts to find the cause

compare 2 populations, 1 group with diease and 1 without disease

-mucous membranes

-skin

-parenteral

respiratory tract

GI tract

genitourniary tract

conjuctiva

unbroken skin usually cannot be penetrated

exceptions - Necator americanus (hookworm), fungi - grow in the skin (keratin)

most bugs only cause disease when they enter through this portal

ex. Strep. : resp tract, causes disease; GI tract, no disease

Infectious Dose - number of bus needed to cause disease in 50% of the population

ex. Anthrax:

skin-ID₅₀=10-50 spores

respiratory-ID₅₀=10,000 spores

GI-ID₅₀=1/2 million spores

Lethal Dose

botulism toxin LD₅₀=0.03 ng/kg

staph LD₅₀=1400 ng/kg

surface molecules are called adhesins or ligands

usually glycoproteins or lipoproteins that attach to receptors on host cells

Strep. mutans - on teeth

S. mutans converts glucose to dextran

dextran becomes bugs glycocalyx 

Actinomyces uses fimbrae to attach to S. mutans glycocalyx

This forms plaque on our teeth

capsules

cell walls

enzymes

antigenic variation

penetration into the host cell cytoskeleton

inhibit ability of phgocytosis

found on: Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilis influenzae, Yersinia pestis

Strep. pyogenes makes M protein that helps attachment and avoid phagocytes

Neisseria gonorrhoeae has protein called Opa to attach, invade, and grow inside WBC. Opa attaches to CD4-lymphocyte, it prevents production of "memory cells" (lifelong immunity where we "remember" antigens we were exposed to)

Mycobacterium have waxy cell wall (mycolic acid) to resist phagocytosis

coagulase

streptokinase

hyaluronidase

collagenase

Staph makes coagulase

coagulase causes the formation of fibrin clots which wall off the infection

Strep. pyogenes (Group A Strep) makes streptokinase which breaks clots and helps infection spread

streptokinase is given to heart attack and stroke victims to prevent formation of clots.

Blood vessels get plaque made of cholesterol, fat, fibrin, and calcium. Platelets stick to plaque and initiate clot formation which contains fibrin. Streptokinase helps break up fibrin. (now TPA (tissue plasminogen activator) is used)

made by Strep. and Clostridium

hyaluronidase digests hyaluronic acids

hyaluronic acids holds cells together

hyaluronidase destroys tissue to help infection spread

Clostridium makes collagenase

collagenase destroys collagen, destroys tissue, & keeps antibiotics away (destroys blood vessels through which antibiotics travel to reach infection)

antigens trigger antibody production - proteins, sugars, nucleic acids

Antigenic variation - some pathogens can change surface antigens and our antibodies no longer recognize them

ex. Influenza, AIDS, Neisseria

Invasins - the pathogen's surface proteins disrupt the cytoskeleton of the host cell (actin & myacin - contractile proteins) and cause it to be engulfed

ex. Neisseria

-using host nutrients

-directly damaging tissue

1.      Pneumonia – Streptococcus pneumoniae

2.      Tuberculosis – Mycobacterium tuberculosis

3.      Whooping cough – Bordetella pertussis

4.      Influenza – Influenzavirus

5.      Measles (rubeola) – Measles virus (Morbillivirus)

6.      German measles – Rubella virus (Rubivirus)

7.      Infectious mononucleosis – Epstein-Barr virus (Lymphocrptovirus)

8.      Chickenpox – Varicella-zoster virus (Varicellovirus)

9.      Histoplasmosis  - Histoplasma capsulatum

10. Cold - Rhinovirus

1.      Shigellosis (bacillary dysentery) – Shigella spp.

2.      Brucellosis (undulant fever) – Brucella spp.

3.      Cholera – Vibrio cholera

4.      Salmonellosis – Salmonella enterica

5.      Typhoid fever – Salmonella typhi

6.      Hepatitis A – Hepatitis A virus (Hepatovirus)

7.      Mumps – Mumps virus (Rubulavirus)

8.      Trichinellosis – Trichenella spiralis

1.      Gonorrhea – Neisseria gonnorrhoeae

2.      Syphilis – Treponema pallidum

3.      Nongonococcal urethritis - Chlamydia trachomatis

4.      Herpes virus – Herpes simplex virus type 2

5.      AIDS – HIV

6.      Candidiasis – Candida albicans

7. Genital warts - HPV

1.      Gas gangrene – Clostridium perfringens

2.      Tetanus -  Clostridium tetani

3.      Rocky Mountain spotted fever – Rickettsia rickettsii

4.      Hepatitis B – Hepatitis B virus (Hepadnavirus)

5.      Rabies – Rabies virus (Lyssavirus)

6.      Malaria – Plasmodium spp.

7. AIDS - HIV

1.      fever

2.      cardiovascular disturbances

3.      diarrhea

4.      shock

5.      inhibition of protein synthesis

6.      destruction of blood cells and blood vessels

7.      spasms disrupting the nervous system

8.      damage of eukaryotic cell membranes

Diphtheria toxin    

Inhibits protein synthesis in eukaryotic cells, especially nerve, heart, and kidney cells

Erythrogenic toxins          

Damages the plasma membranes of blood capillaries under the skin and produce a red skin rash. Ex. Scarlet fever

Botulinum toxin     

Prevents transmission of impulses from nerve cell to muscle and causes paralysis where muscle tone is lacking

Exotoxin & Effects - Clostridium tetani 

Tetanus toxin

(tetanospasmin)                              

Blocks the nerve relaxation pathway causing uncontrollable muscle contractions, such as “lockjaw”

Exotoxin & Effects - Vibrio cholera        

Cholera toxin          

Causes cells to secrete large amounts of fluids and electrolytes resulting in severe diarrhea 

Staphylococcal enterotoxin    

Produces a superantigen that causes cells to secrete large amounts of fluids and electrolytes resulting in severe diarrhea. Toxic shock syndrome is caused by secretion of fluids and electrolytes from capillaries that decrease blood volume and lowers blood pressure