Bacteriology Exam 1

define frank pathogens

capable of causing disease in any host; always considered a pathogen when isolate

define opportunistic pathogens

capable of causing disease given the opportunity; often a commensal and part of the normal host flora, but is capable of causing disease in normally sterile tissues

what group of pathogens is most common?

opportunistic pathogens

define non-pathogens 

even weak or non-pathogenic bacteria can cause disease in hosts with weakened immune systems

gram + bacteria appear what color?

purple/ blue

gram - bacteria appear what color?

pink/red

gram + bacteria have a _____ peptidoglycan cell wall

thick

gram - bacteria have a ______ peptidoglycan

thin

acid fast bacteria contain

mycolic acid

LPS is considered an

endotoxin

what receptors does LPS bind to

CD14, TLR4, MD2 receptor

define flagella

filamentous appendages (2-20um) composed for flagellin monomers that allow for motility

Flagella has ____ antigens that can be detected by specific antibodies 

H

define glycocalyx

capsule or slime layer that is composed of carbohydrates or glycoproteins

what is the purpose of glycocalyx

inhibits phagocytosis and antibiotic uptake

glycocalyx contains ___ antigens that are detect by specific antibodies

K

define pili

• filamentous appendages (0.5-2.0 um) composed of pilin monomers

• allow for adhesion (fimbriae) and specialized sex pili allow for transfer of DNA between a donor and a recipient

define thermophiles

optimal temperature 55-75 C

can survive from 40-80 C 

define mesophiles

optimal temperature 30-45 C

can survive from 10-47 C

define pyschrophiles

optimal temperature 15-18 C

can survive from -5 to 22 C 

define microaerophilic

requires reduced oxygen (low quantities)

define capnophilic bacteria

only grow in air with additional carbon dioxide

characteristics of a surface colony

• Surface: smooth & glistening; rough; glanular; wrinkled dry & powdery

• Whole colony: circular, filamentous; irregular; rhizoid; punctiform

• Elevation: flat; raised; convex; pulvinate; umbonate

• Margin: entire, undulate, curled, lovate, serrate, filamentous

• Size: diameter in mm; pinpoint; small, medium, and large

• Color: pigmentation

examples of motility tests

1. wet mount: direct microscopic observation

2. motility culture medium: soft agar stab 

O antigens can be found in

LPS

H antigens can be found in

flagella

K antigens can be found in

capsule

serological tests for bacterial identification

1. slide agglutination

2. counter-immunoelectrophoresis 

3. ELISA 

4. latex agglutination

5. western blotting 

6. radioimmunoassay 

7. complement fixation

8. fluorescent antibody

describe the process of detecting carbohydrate utilization

• broth culture medium containing specific sugar, pH indicator, and Durham tube 

• color change to yellow = acid production, able to ferment 

• color change and gas bubble = able to ferment and gas production

triple sugar iron medium can be used to 

differentiate enteric bacteria based on their ability to ferment surgars, produce H₂S and/or produce gas 

this test shows 

non-fermentor

this test shows

non-lactose fermentor 

this test shows 

lactose/ sucrose fermentor 

this test shows 

non-lactose fermentor, H₂S producer 

what does Bromthymol blue test for?

pH of a solution to determine if carbonic acid is formed

yellow solution on bromthymol blue test

acidic solution; carbonic acid formed

green solution on bromthymol blue test

neutral pH

blue solution on bromthymol blue test

basic solution

define decontamination

cleaning and any additional steps required to eliminate risk of infection while handling devices or attire. A reduction in potentially pathogenic organisms to a level that is safe to handle

define disinfection 

elimination of most if not all PATHOGENIC organisms, including spores. Most effective when preceded by cleaning

define sterilization

Elimination of ALL living organisms/ agents

describe autoclave

useful for sterilization of heat stable liquids and objects

• 121 C, 15 min 

describe dry heat 

• 160 C (320F) for 1-2 hours

• slower than moist heat

• limited to inanimate, heat resistant objects

describe incineration

• 300 C until completely oxidized

• fast but expensive

• useful in elimination of pathogen contaminated materials (bandages, carcasses, tissues)

for liquid filtration what size filter should be used?

0.2 micrometers

define HEPA (high efficiency particulate air filter)

99.999% of 0.12 micron particles are filtered

• face masks, sterile hoods, room air filters 

define cleaning

removal of foreign material

define minimum effective concentration (MEC)

concentration of a germicide require to achieve advertised microbicidal activity

define low-level disinfectants

germicide that kills most vegetative bacteria and lipid-enveloped and medium size viruses

define intermediate level disinfectant

kills all microbial pathogens except spores

define high level disinfectant

kills all microbial pathogens except large number of bacterial spores

what is the order of bacteria affected by disinfectants (most to least)?

1. gram +

2. gram -

3. acid fast

4. spore formers 

what is the concentration of ethanol that is most effective as a disinfectant?

70%

what is the role of alcohol as a disinfectant?

denature proteins and solubilize lipids

what is the role of alkalies as a disinfectant?

• destroys cell walls and membranes 

• used in inanimate objects not sensitive to alkaline pH 

what is the role of heavy metals (HgCl2 (0.001%), AgNO3, and copper) as a disinfectant?

1. metals poison enzyme activities by interacting with sulfhydryl groups of cysteine residues

2. the basis for merthiolate and mercurochrome uses as skin antiseptics; “burns” open tissue as it is solubilized in alcohol!!!

what are the different classes of chemical disinfectants?

1. alcohols 

2. alkalines

3. heavy metals

4. oxidizing agents

5. surface active agents

6. phenolic compounds

7. aldehydes

what is the role of oxidizing agents as a disinfectant?

inactivate enzymes by converting functional -SH groups to oxidized S-S forms; can attack -NH groups, indole groups and tyrosine residues

what is the role of surface active agents as a disinfectant?

induce a reduction of surface or interfacial tension (ex. wetting agents, detergents)

what are the most commonly used aldehydes?

glutaraldehyde, ortho-Phthalaldehyde, and formaldehyde

describe glutaraldehyde in disinfection 

high level disinfectant that is compatible with many materials, and so is the agent of choice for chemical disinfection of hospital materials

describe ortho-Phthalaldehyde as disinfectant

a 0.55% solution for 12 min is a high level disinfectant, is also compatible with many materials, is more active than glutaraldehyde against mycobacterium

describe formaldehyde as a disinfectant

high level disinfectant used as a liquid or gas. Not used as commonly as previously due to irritation and potential carcinogenicity

bacteria transfer DNA through 

• transformation

• conjugation

• transduction

define transformant

cell that have taken up recipient DNA by transformation

define competent

bacteria that can take up DNA naturally (ex. without artificial treatment)

define homologous recombination

identical or similar regions of DNA align and exchange each other by excision-repair

• also known as allelic exchange or strand replacement

define transfection

uptake of viral DNA

define complementation

the mutated DNDA expressed on a plasmid (in trans) will correct the mutation

define transduction

is the process of transferring DNA from one bacterium to another by a phage

virulence factor of Salmonella

O antigens (in LPS) can vary as a function of the phage lysogenizing them → serologically different!

virulence factors for Clostridium botulinum

types C and D are toxigenic only when infected with a specific phage

virulence factors for Escherichia coli

lysogenic lambda phage expresses a gene encoding a host cell envelope protein that provides serum resistance! (ex. resistance to antibodies and complement)

virulence factors for Corynebacteriym diphtheriae

the beta prophage carries the diphtheria toxin tox gene, which is expressed only when the bacterium infects its host

virulence factors for Vibrio cholera

cholera toxin genes are on a prophage (phage that has integrated into the genome). Such cells are known as lysogenes

define plasmids

genes of unknown origin and often not necessary for growth; others contain genes encoding virulence factors

define F-factor

fertility factor; genes promote replication and transfer of the factor to recipient cells (ex. conjugation)

define R-factor

F-factor + genes encoding resistance to specific antibodies

R-factor plasmid contained two types of genes including 

1. resistance transfer factor (RTF): encodes origin of replication, sex pilin genes

2. r-determinants: genes encoding antibiotic resistance, heavy metal resistance or other virulence factors (determinants), insertion sequences (IS)

define transposons

are mobile genetic elements designated as “Tn”

effects of transposon movement

• mutation resulting from insertion into middle of another gene

• neutral event; insertion next to an intact gene

• excision; can carry along a neighboring gene → virulence gene

what are the 5 bacteria classes based on cell wall structure?

1. mycoplasma 

2. gram +

3. mycobacterium 

4. gram -

5. chalmydia 

describe mycoplasma cell wall

• no cell wall 

• sterols in cell membrane

describe gram + cell wall

have a thick cell wall with peptidoglycan and lipoteichoic acid

describe the cell wall of mycobacterium

cover their cell wall with mycolic acid

describe cell wall of gram - bacteria

cover cell wall with lipopolysaccharides (lipid A and sugars or endotoxins)

describe the cell wall of chlamydia

have a cell wall with little to no peptidoglycan but covered with lipopolysaccharides (lipid A and sugars or endotoxins

what are the 6 mechanisms of actions of antimicrobials

(1) DNA gyrase/ topoisomerase responsible for DNA synthesis.

(2) RNA polymerase which is responsible for mRNA synthesis.

(3) 30S subunit of ribosome which is responsible for protein synthesis.

(4) 50S subunit of ribosome which is responsible for protein synthesis.

(5) metabolism which produced folic acid 

(6) cell wall synthesis

antimicrobials that act on DNA gyrase/ topoisomerase 

• Flouroquinolines

• Nitroimidazoles

antimicrobials that act on RNA polymerase

Rifamycins

antimicrobials that act on 30S subunit

• Tetracycline

• Aminoglycosides

antimicrobials that act on 50S subunit

• Mycolides

• Chloroamphenicol

antimicrobials that act on bacterial metabolism

• Sulfonamides

• Trimethoprim

antimicrobials that act on cell wall synthesis 

• B-lactams

• Penicillinis

• Cephalosporins

• Carbapenems

• Monobactams

define therapeutics

if an individual is sick, treat the patient to cute

define metaphylactics

if one patient is noticed in herd, treat the whole herd and control the spread

define prophylactics

seasonal prescription of drug to prevent the most susceptible population within a herd

what is the non-traditional use of antibiotics that has been banned?

growth promotion

mechanisms of bacterial resistance to antimicrobials 

1. reduced permeability: shrink/ narrow or close porins so that the antimicrobial drug can not enter

2. efflux pumping (vomiting): once the antimicrobial enters the cell, it will vomit to eject the antimicrobial

3. drug inactivation by enzymes: if the drug enters the cell, enzymes are present to break it down immediately

4. target site change, modification, or protection: binding site on the cell changes so drug can not recognize

5. biofilm formation: joining of several bacteria in order to fight against the drug

6. naturally become AMR depending on absence of cell wall structure (ex. mycoplasma): some bacteria naturally lack a cell wall, which is one less place in which a drug can act

tetracycline is blocked by

efflux pumping from bacteria