Lecture 20- Bacteria & Human/Animal Disease Flashcards
What do we mean when we say bacteria are ubiquitous?
they are everywhere (soil,water,air,mud,saliva,skin,etc)
Are most bacteria beneficial or harmful?
vast majority are beneficial?
Explain the ways that bacteria can be beneficial
- some produce drugs &chemicals (ethanol, acetic acid, streptomycin- an antibiotic)
- some produce food products (cheese,butter,yogurt)
- Saprophytes break down organic matter
- legumenous bacteria fix N₂ to Nitrates, amino acids etc
What is infection?
the process of microbial invasion & multiplication in body of a human/animal
What is an infectious disease>
diseases caused by an infectious agent (spreads easily from person to person)
What are some of the way infectious diseases cons be spread?
- direct contact with body
- contact with contaminated items
- breathing in exhaled air
What type of bacteria are flora, where are get located, and how do they obtain energy?
- they are commensals heterotrophs
- live on skin,mucous membranes of (mouth,vagina,upper respiratory tract, intestines)
- contain energy from secretions/food residues
- Generally harmless but opportunistic when immune system impaired (may invade tissue & cause disease)
What are frank pathogens?
- true pathogens that overcome normal body defense& invade tissue
- ‘growth or production of toxins damages tissue, causing disease
Which. Bacterium did Koch test mice on?
Anthrax
What is Koch’s postulate?
a postulate establishing a causal relationship between a pathogen & a specific disease
- A Frank pathogen must be found in body of all cases of that disease
- should be isolated from a known animal that has disease and growin in pure culture in vitrio & characterized (study properties)
- inject pathogen into a healthy susceptible,animal
- reisolate organism & reidentify
What is a Localized and what is a systemic infection?
localized infection- confined to small body area
systemic infection- spreads throughout body
What is the difference between primary, secondary, and mixed infection?
primary infection is caused directly by organism
Secondary infection is an organism that causes a disease opportunistically (commensals)
mixed infection is an infection caused by 2+ Organisms
What is a Nosocomial infection?
An opportunistic infection acquired in the hospital
What is bacteremia and Septicemia?
Bacteremia- bacteria present in blood
Septicemia- bacteria & harmful products (toxins) present in blood
What are the primary defended against infection?
- Normal intact skin
- microbial flora
- mucous membranes
- fluid flow (tears,urine.saliva)
What are the chemical defenses the body has against infection?
- Enzymes (lysozymes in tears,saliva,human milk, mucous)
- Acidity (fatty acids on skin 3-5 , lactic acid in vagina, HCl I’m stomach)- low Ph retards bacterial growth
What are the frequent ports of entry of infectious agents?
- Respiratory tract
- GI(gastrointestinal) tract
- urinary & genital tracts
- cuts/burns in mucous membranes or skin
What must bacterial cells do in order to enter cells and multiply?
Adhere to cells, using Adherence factors (fimbriae, capsule)
then they produce hydrolytic enzymes (proteases,lipases,etc)
*some do both, some do one of these steps
What is another name for the properties of pathogenic bacteria that allow transmition of disease (easy transmissibility, adherence, etc)
Virulence factors
What are toxoids?
neutralized form of exotoxins, can be injected as a vaccine
What are exotoxins?
Proteins secreted by some G+ & G- bacteria that are
- heat sensitive
- highly toxic (Tetanus,Diptheria,Cholera)
- antigenic (stimulate cells to make antibodies )
- usually bind to specific receptors
- Include neurotoxins (Tetanus)
- include cytotoxins (Diptheria)
- include enterotoxins- toxic to intestine (Cholera)
What is an Endotoxin?
LPS (lipopolysaccharide of G- cell Wall) ONLY
- Moderately toxic- released when bacterial cell lysis
- heat stable
- cannot be converted to toxoids
Under what circumstance can endotoxic shock take place, and what are the consequences?
during septicemia, causing impaired functioning of essential organs
- heart
- brain
- kideney (etc)
What other cell components other than endo and exo toxins are toxic?
- PG monomers
- teichoic acid of Gram +
- mycolic acids of mycobacterium & other acid fast
What is the ability of the bacteria to change its fimbria called?
Antigenic variation
Is it possible to kill bacteria that have fully formed their spores?
No, they are dormant, not fully alive (not metabolizing )
What are the variables that control bacterial population?
- Competition for limited nutrients
- temp
- humidity
- Salinity
- presence of bacteriophages (T4 kills E coli)
Describe T4 bacteriophage cycle
- Attachment of Bacteriophage to specific outer surface receptors of É coli
- injection of DNA, by contraction of sheath tail
- Hydrolysis of DNA & synthesis of viral genomes & proteins
- Assembly of bacteriophage 3 sets of proteins heads, tails,and tail fibers- phage genome packaged in capsid while head forms
- lysis of bacterial cell by phage directing production of an enzyme that damages cell wall, allowing fluid to enter 100-200 phage exit
What are Disinfectants and antiseptics?
Disinfectants-chemicals used to kill vegetative bacterial cells from inanimate objects (chair,table.etc)
Antiseptics- Chemicals used on living tissue (skin) to inhibit growth or kill bacteria
What are antibacterial agents?
chemicals used to control bacterial growth during an infection
they are antibiotics and can be fully natural
semi-synthetic (made from natural)
Synthetic- made from man made drugs
What is the difference between broad and narrow spectrum antibiotics, and how can these antibacterial agents work (broadly)
Broad spectrum are effective against many gram + & gram -
narrow spectrum- kill only gram + or gram - or few bacteria
are either
Bactericidal- lysis kill bacteria
Bacteriostatic- inhibit growth for long enough for immune system to kill them
Give specific ways antibacterial agents can work
- inhibit cell wall synthesis - causing osmotic lysis- low toxicity (penicillin, cephalosporin)
- alter ribosomes - faulty protein synthesis
affect 30S (streptomycin)
affect 50S (erythromycin)
- inhibit Nucleic acid synthesis - topisomersde & DNA replication inhibition (quinolone)
- inhibit bacterial RNA synthesis (Rifampicin)
