40 Questions
What type of bacteria obtains nutrition from a host organism by offering something in return?
Symbiotic Bacteria
Which type of bacteria obtains nutrition from dead and decaying matter?
Saprophytic Bacteria
What is the term for bacteria that have a single polar flagellum?
Monotrichous
Which of the following bacteria is an example of a Non-motile bacterium?
Staphylococcus
What is the term for organisms that cannot reproduce outside the cell?
Obligate Intracellular Organism
Who are particularly susceptible to intracellular pathogens?
People with T-cell deficiencies
What is defined as a microorganism that causes or is capable of causing disease?
Pathogenic microorganism
Under what conditions can some pathogens cause disease?
When the host is immunocompromised
What is the basis of classification of Gram Positive bacteria into Cocci and Bacilli?
Shape and arrangement
Which of the following bacteria is an example of Gram Negative Cocci?
Neisseria meningitidis
What is the characteristic of Streptococcus pneumonia?
Alpha hemolytic
Which staining method is used to identify Mycobacterium tuberculosis?
Acid-fast staining
What is the characteristic of Corynebacterium diphtheriae?
Positive to Albert’s staining
Which of the following bacteria is an example of Gram Negative Bacilli?
Escherichia
What is the basis of classification of bacteria into Enteric and Non-Enteric groups?
Source of isolation
Which of the following bacteria is an example of Gram Positive Bacilli?
Bacillus
What is the primary function of bacterial adhesion molecules?
To prevent bacteria from being carried away by mucus or washed from organs with significant fluid flow
Which of the following bacterial enzymes facilitates invasiveness by degrading components of the extracellular matrix?
Collagenase
What is the main difference between pyogenic and granulomatous inflammation?
The type of immune cells involved
What is the characteristic of exotoxins secreted by bacteria?
They are proteins secreted by both gram-positive and gram-negative bacteria
What is the role of bacterial cell surface adhesion molecules in the formation of microcolonies?
They allow attached bacterial cells to form microcolonies
What is the characteristic of strains of Neisseria gonorrhoeae that lack pili?
They are not pathogenic
What is the type of inflammatory response that involves the formation of pus?
Pyogenic
What is the estimated amount of tetanus exotoxin that can kill an adult human?
1 microgram
What is the function of the two polypeptide components of exotoxins?
One is responsible for binding the protein to the host cell and the other is responsible for the toxic effect
What is the effect of moderate heating on most exotoxins?
It rapidly inactivates them
What is the function of dilute formaldehyde treatment on exotoxins?
It inactivates their toxic activity but does not affect their antigenicity
What is the role of the Tox gene in Corynebacterium diphtheriae?
It is a gene that encodes the diphtheria exotoxin
What is the primary component of the outer membranes of gram-negative bacteria?
Lipopolysaccharide (LPS)
What is the physiologic effect of LPS endotoxins?
Fever, shock, hypotension, and thrombosis
What is the mechanism of action of LPS endotoxins?
Activating macrophages and releasing cytokines
What is the term for the inactivated toxin that can be used in vaccine preparation?
Toxoid
What is the main difference between LPS and peptidoglycan fragments of gram-positive bacteria?
Peptidoglycan fragments are less potent than LPS.
What can happen when antibiotics are used to eliminate the causative bacteria?
There will be a sudden massive release of endotoxin into the circulation.
What is the purpose of antigenic switching in bacteria?
To evade the host's immune system.
What is the result of phase variation in bacteria?
The expression of genes coding for surface antigens is turned on and off.
What is the consequence of antigenic variation in bacteria?
The expressed surface antigen can assume many different antigenic structures.
What is the limitation of isolating a microorganism from infected tissue?
The isolated organism may not be the causative agent of the infection.
What is the difference between an opportunistic pathogen and a harmless member of the normal flora?
An opportunistic pathogen is a harmless member of the normal flora that becomes pathogenic in certain conditions.
What is the result of death due to multiple organ failure?
The infection can lead to shock syndrome.
Study Notes
Classification of Bacteria
- Bacteria can be classified based on staining, shape, and other characteristics.
- Gram staining:
- Gram positive: Cocci (e.g. Streptococcus, Staphylococcus), Bacilli (e.g. Bacillus, Clostridium)
- Gram negative: Cocci (e.g. Neisseria meningitidis), Bacilli (e.g. Escherichia, Salmonella)
- Acid-fast staining:
- Example: Mycobacterium tuberculosis, Mycobacterium leprae, Nocardia
- Albert's staining:
- Example: Corynebacterium diphtheriae
Shape of Bacteria
- Cocci: oval or spherical; may be arranged in pairs, tetrads, chains, or clusters
- Symbiotic Bacteria: obtain nutrition from host organism by offering something in return
- Pathogenic Bacteria: obtain food from host but are harmful to the host, causing diseases
- Saprophytic Bacteria: obtain nutrition from dead and decaying matter
Presence of Flagella
- A. With flagella:
- Monotrichous (single polar flagellum): Vibrio cholerae
- Lophotrichous (multiple polar flagella): Spirilla
- Peritrichous (flagella distributed over the entire cell): Salmonella, E. coli
- Amphitrichous (single flagellum at both ends): Spirillum minus
- B. Without flagella: Atrichous bacteria
Motility
- Motile bacteria: Salmonella, Vibrio cholerae, Pseudomonas
- Non-motile bacteria: Staphylococcus, Shigella
Obligate Intracellular Organisms
- Organisms that cannot reproduce outside the cell
- Examples: viruses, bacteria (Chlamydia, Rickettsia, Coxiella), protozoa (Plasmodium spp.), fungi (Pneumocystis jirovecii)
Pathogenicity of Bacteria
- A pathogenic microorganism is defined as one that causes or is capable of causing disease
- Factors that influence pathogenicity: adhesion, invasiveness, bacterial toxins
- Adhesion: bacteria have cell surface adhesion molecules or hydrophobic cell walls that allow them to adhere to the host cell membrane
- Invasiveness: bacteria that can enter host cells or penetrate mucosal surfaces
- Bacterial toxins: exotoxins and endotoxins
Exotoxins
- Proteins secreted by both gram-positive and gram-negative bacteria
- Examples: tetanus exotoxin, diphtheria toxin
- Mechanism of action: bind to host cell, inactivate protein synthesis
- Inactivation: moderate heating (60°C), treatment with dilute formaldehyde
Endotoxins
- Lipopolysaccharide components of the outer membranes of gram-negative bacteria
- Released into the host's circulation following bacterial cell lysis
- Mechanism of action: activation of macrophages, release of cytokines, activation of complement and coagulation cascade
- Physiologic effects: fever, shock, hypotension, thrombosis, septic shock
Elimination of Causative Bacteria
- Antibiotics can initially exacerbate symptoms by causing sudden massive release of endotoxin into the circulation
Antigenic Switching
- Mechanism of evading the host's immune system: phase variation, antigenic variation
- Phase variation: genetically reversible ability of certain bacteria to turn off and turn on the expression of genes coding for surface antigens
- Antigenic variation: modification of the gene for an expressed surface antigen by genetic recombination with one of many variable unexpressed DNA sequences
This quiz covers the classification of bacteria based on staining methods, including Gram staining and Acid-fast staining. It also explores the different types of bacteria, including Gram positive and Gram negative bacteria.
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