Koch’s Postulates

1.      isolate the suspected agent from a disease victim.

2.      grow the agent in pure culture.

3.      infect a healthy host and show that the organism

produces the classical clinical disease.

4.      Isolate the "same" organism from the new victim.

Cytoplasmic membranes are similar to eukaryotic membranes but do not contain steroids (e.g., cholesterol). 

Which are the exception to this rule?

Most have signature teichoic and lipoteichoic acids in the thick peptidoglycan wall

Which type of bacteria?

Teichoic acids:

·         Strong negative charge.

·         Covalently linked to the peptidoglycan

·         Strongly antigenic

Generally absent in gram-negative bacteria.

·         Believed to aid in concentrating metal ions from the surroundings.

Characteristics of Lipoteichoic acids

Lipoteichoic acids:

·         Attached to fatty acids and anchored in the cytoplasmic membrane.

·         Antigenic, cytotoxic and can be involved in adherence 

Mechanical disruption of the cell wall of Gram-positive organisms or its enzymatic removal with lysozyme 

Also, old starved bacteria and those treated with antibiotics.

_________ and _________ do not have cell wall and therefore cannot be differentiated by Gram stain.

Peptidoglycan polysaccharides are made up of repeating disaccharides of ________ and _________

·         Cross-linking in peptidoglycans occurs between the ______ amino acid and another amino acid at the ______ position of another chain.

In peptidoglycan synthesis passing through the membrane, activated units are attached and assembled in the _________ _________ membrane pivot.

The region of the LPS that is essential for viability of almost all gram negative bacteria

Which region of the LPS allows distinguishing of serotypes (strains) of a bacterial species and is the antigenic portion of the LPS?

gram positive

Bacillus and Clostridium

Cells that lack rigid shape, assume spherical shape.

if gram-negative cell, then _________

If gram-positive, then __________ 

spheroplasts

protoplasts

Cocci are what shape?

Spherical

The position of the plane of successive cell divisions.

g = 

give both equations

                  ______ t_______                  

 3.3 [logNt -logN0]

or

t/n

1.      Algae

2.      Protozoa

3.      Fungi

4.      Bacteria

5.      Archaea

6.      Viruses

The minimum requirements for bacterial growth are sources of:

Carbon

Nitrogen

Energy

H2O

Ions

Bacterial pathogens are almost always _________. 

This means what?

chemoheterotrophs

they are unable to fix carbon and form their own organic compounds

Respiration requires ___ as a terminal electron acceptor and is _____ efficient at generating energy

O2

most

Coenzyme A structural groups:

Anaerobic respiration uses compounds other than oxygen (_____. _____. ______) as terminal electron acceptors, produces less ATP per mole of glucose than aerobic respiration

Glycolysis produces ___ ATP and ___ NADH

for a total of ___ ATP after ETC

2, 2

8

The Krebs cycle produces ___ GTP, ___ NADH, and ___ FADH2

This yields a total of ___ ATP

2 GTP, 6 NADH, 2 FADH2

Total of 24 ATP.

Plasmid pTP10 is found in the clinical isolate of which bacteria

E.coli

“λ lysogen”

Example of a secretion pathway that is dedicated to virulence

Bacterial adherence is often mediated by adhesins:

o   Fimbrial adhesins

o   Afimbrial adhesins

Streptococcus mutans

            Adhesin: 

            Receptor: 

            Attachment site: 

            Disease: 

glycosyl transferase

salivary glycoprotein

pellicle of tooth

dental caries

Streptococcus salivarius

            Adhesin: 

            Attachment: 

            Disease:

lipoteichoic acid

buccal epithelium of tongue

no disease

Bacterial invasion factors:

Ex 1: Listeria invasion and cell-to-cell spread is mediated by a protein named ______.

Which other bacteria has a homolog for protien?

Internalin

Porphyoromonas gingivalis (Pg)

Bacterial invasion factors:

Salmonella uses ____ to secrete effectors that induce “_______  ________” (macropinocytosis)

T3P

membrane ruffling

Endotoxin is released upon lysis or through “_______” of outer membrane vesicles.

Endotoxins bind to specific receptors and stimulate release of ________   (e.g., IFN-g, IL-1, TNF-a, IL-6, histamine, prostaglandins), stimulate growth of _______, and induce ______ followed by ________.

Broad classes of exotoxins

2 types of intracellular targets 

o   A-B dimeric exotoxins (B, binding; A, active)

o   ADP-ribosylation of intracellular target host molecule

Broad classes of exotoxins

Cellular targets

Cytolytic exotoxins (usually degradative enzymes) or cytolysins

1)      Hydrolyze membrane phospholipids (phospholipases). 

2)      Thiol(-SH)-activated cytolysins alter membrane permeability by binding to cholesterol.

((3)      Detergent-like activity on cell membranes; rapid rate of lysis.

These are types of ___________

3 Examples of Two-Component A-B Exotoxins with Intracellular Targets

·         Anthrax toxin (PA, EF, LF)

·         Shiga toxin, A-5B

·         Cholera toxin, A-5B

___________ is considered to be the initiating organism and ________ the secondary invader of dental caries.

MS (mutans streptococci) 

LB (lactobacilli)

E.coli & K. pneumoniae

New Dehli metallo-β-lactamase (NDM) 

1^st colonizers come from saliva:

1)      Streptococcus sanguinis and Streptococcus mitis (gram +, facultative)

2)      Actinomyces (gram +, most are obligate anerobes)

In pregnancy gingivitis women often suffer from advanced gingivitis associated with high levels of an alleged opportunistic pathogen in the subgingival biofilm:

Which pathogen?

Aggregatibacter actinomycetemcomitans is the only gram negative rod associated with periodontitis that is a _________ ________.

HIV-associated gingivitis and periodontitis:

Failed endontically treated teeth usually are dominated by Gram positive facultative anaerobes, and almost always include _______ ________, a species normally found in the human gut.

Infection bodies of fungi

Spores which are present on stalk-like projections or other 

Infectious bodies of fungi

 Septal fragments of the hyphae which separate to become reproductive entities

Pathogen causing Histoplasmosis 

 “Chicago disease” 

·         Pathogens remain viable in macrophages, which serve as vectors in disseminated disease to various organs

Pathogen causing Blastomycosis

Organisms phagocytize alveolar macrophages

·         Lung infection usually clears, but can form ulcerative skin and bone lesions in immunocompromised patents

Most prevalent in South America

Affects men vs women (78:1)

Primary lung infection, but can disseminate and cause mortality (16-25%) in immunodeficient.

Disseminated fungus produces painful ulcers on oral, nasal, and GI muscosa

American southwest, airborne from soil

Pathogenic organism of this disease exists only

in yeast form

 Pulmonary symptoms and radiographic lung nodules

  Second most common fungal infection in

immunosuppressed patients after candidiasis.

 Major veterinary pathogen affecting sheep and cattle

  Conidia of the fungus are inhaled from the environment

and produce localized lung infections associated with tubercular growths called mycetomas or “fungus balls”

 The pathogen also can spread via the blood and invade blood vessles causing necrosis and thrombosis, or invade organs including the brain. 

·         Aflatoxin, an extracellular protein elaborated by A. flavus (in most cases), can contaminate foodstuff, such as peanuts, and may induce hepatocellular carcinoma.

·         It is the most common opportunistic respiratory infection in late stage HIV patients and accounts for a 10-20% mortality rate in these individuals. 

The organism does not invade host cells but exists in pulmonary interstitial tissue as a sporocyst (spore case)

 Death occurs from asphyxiation. 

Treatment is administration of

trimethoprim-sulfamexoxazole or pentamidine

isethionate (both of which have side-effects) and

oxygen administration.

These two drugs form large pores in fungal cell membranes, which allow leakage of vital cell constituents. 

Drugs which affect ergosterol synthesis

Give two examples

Azole derivatives

ex:Imidazoles and Triazoles

________ is administered orrally and is taken up by the fungus, converted to 5-fluorouracil and then metabolized into compounds which are inhibitory to either RNA or DNA function. 

What is one advantage of this drug over amphotericin B

 5-flurocytosine

This drug is able to enter the CSF, whereas amphotericin B cannot

Drug that is administered orally and is active against dermatophytes, not has no effect on systemic mycoses

1) Prevention of the interaction between PBP and the antiobiotic

2) Modification of the interaction between PBP and the antibiotic

3) Hydrolysis of the antibiotic by B-lactamases

High-molecular-weight octapeptides that inhibit Gram-negative bacteria by interacting with the membrane and increasing cell permeability.

Polymyxins

 Gram negative bacteria are intrinsically resistant to the hydrophobic drug ________, because of decreased uptake of the drug

  Aminoglycosides

Aminoglycosides 

B-lactams increase their uptake.

Oxazolidinones,  Lincosamides,  Chloramphenicol, 

Macrolides, Streptogramins

 Oxazolidinones (linezolid)

What is the mechanism of action for  Chloramphenicol

Binds reversibly to the 50S ribosomal subunit

(Bacteriostatic)

Which drug has a broad similar spectrum to tetracyclines, but is not commmonly used in America?

 What is the mechanism of action for the macrolides

Binds reversibly to the 23S RNA component of the 50S ribosomal subunit 

(bacteriostatic)

Most gram negative bacteria are resistant to this class of drugs that is primarily used to treat pulmonary infections

Which class of drugs are cyclic peptides that are administered as a combination of two components.

Group A and Group B

For steptogramins

Group A component binds to the ______________ and facilitates binding of the _____________.

Group B component inhibits _____ _______.

50S ribosomal subunit

chain elongation

Bacteriostatic

Broad range

-p-aminosalicylic acid

isoniazid

folic acid

synergistically

Which cleaning method removes microorganisms from liquids that would be destroyed by heat

What are some examples of these liquids

Filtration

ex: enzymes, vaccines, antibiotics

What are the 3 methods of sterilization monitoring.

Give an example of each

Which is most accurate?

Mechanical, Chemical, and Biological

Mechanical: monitor cycle length, pressure, or temperature

Chemical: use external or internal chemical indicators

Biological: Directly assess killing of known highly resistant microorganisms once per week mininimum.

Biological is only one that proves sterility

One time use of critical instruments

Don't allow tissue to dry on instruments

Completely clean instruments and autoclave at 134 degrees Celcius for 18 minutes

These are precautions for which disease?

Protective antigen (PA)

Edema factor (EF)

Lethal factor (LF)

For which toxin does

B-subunit binds to Gb3 glycolipid receptor

A -subunit prevents binding of aminoacyl-transfer RNA by cleaving 28S rRNA from 60S ribosomal subunit resulting in inhibition of protein synthesis

Shiga toxin, from bacterium 

Shigella dysenteriae