28 Questions
What is one important evasive strategy for a successful pathogen to evade the host's immune system?
Change its surface antigens
What is the term for an organism that is unable to cause disease in healthy, immunocompetent individuals but can infect those with impaired defenses?
Opportunistic pathogen
Highly communicable diseases such as cholera are noncommunicable.
False
Which staining technique is primarily used for classifying bacteria into Gram positive and Gram negative?
Gram staining
Name one example of a Gram positive cocci bacteria.
Staphylococcus
Exotoxins are primarily produced by Gram-negative bacteria.
False
______ are pathogenic microorganisms that cause or are capable of causing disease.
Pathogenic microorganisms
Match the following bacterial classification based on shape with the correct description:
Cocci = Spherical or oval shape; may be arranged in pairs, clusters, or chains Bacilli = Rod-shaped; may show different arrangements like coccobacilli, streptobacilli, comma shaped, and spirella Spirochetes = Slender, spiral-shaped bacteria Actinomyces = Branching filamentous bacteria
What is a key characteristic of Gram-positive bacteria based on staining?
Have a thick peptidoglycan layer
What type of staining is used to identify acid-fast bacteria?
Acid-fast staining
Bacteria that appear pink/red after Gram staining are classified as ________.
Gram negative
Exotoxins are released by gram-positive bacteria only.
False
Match the following terms with their definitions:
Endotoxins = Heat-stable lipopolysaccharides released from gram-negative bacteria Exotoxins = Proteins secreted by bacteria that cause harmful effects Invasiveness = Ability of bacteria to penetrate host cells or mucosal surfaces Pathogenicity = Capacity of a microorganism to cause disease
What is one important evasive strategy for pathogens to evade the host's immune system?
Changing its surface antigens
What is the term for a harmless member of the normal skin flora that can cause an infection in necrotic tissue?
Opportunistic pathogen
Who is the nineteenth century German microbiologist known for defining Koch's postulates?
Robert Koch
What is the term used for highly communicable diseases that tend to occur as localized epidemics?
Contagious diseases
What is the term used for diseases that can lead to a worldwide epidemic?
Pandemics
What are the two types of toxins produced by bacteria that cause disease?
exotoxins and endotoxins
What is the precise target of diphtheria toxin?
Protein synthesis
Endotoxins are components of the cell walls of gram-negative bacteria.
True
Bacteria that have an outer poly-saccharide capsule have a better chance of surviving ____________ host defenses.
primary
Match the following stages of the infectious process with their descriptions:
Entry into the host = Evasion of host primary defenses Adhesion of the microorganism to host cells = Preventing bacteria from being carried away by mucus Propagation of the organism = Spreading from the initial site of infection Damage to host cells by bacterial toxins or inflammatory response = Resulting in pus formation or inflammatory lesions Evasion of host secondary defenses = Overcoming host defenses to establish itself
What is one important evasive strategy for a successful pathogen to evade the host's immune system?
Changing its surface antigens
What is one mechanism that allows certain bacteria to turn off and on the expression of genes coding for surface antigens?
Phase variation
Opportunistic pathogens can cause disease in immunocompetent individuals.
False
What did Robert Koch define to confirm the identity of the causative microbial agent of a disease?
Koch's criteria
What term is used to describe diseases that are highly communicable and easily spread?
Contagious
Study Notes
Classification of Bacteria
- Bacteria can be classified based on:
- Staining: Gram positive, Gram negative, Acid-fast, and Albert's staining
- Shape: Cocci, Bacilli, Spirochetes, Actinomyces
- Growth and nutrition: Oxygen requirements, Carbon dioxide requirements, Temperature, pH, Light, Osmotic pressure, and Carbon source
- Presence of flagella: With flagella (Monotrichous, Lophotrichous, Peritrichous, Amphitrichous) and Without flagella (Atrichous)
- Motility: Motile and Non-motile
Gram Staining
- Gram positive bacteria:
- Cocci: Streptococcus, Staphylococcus
- Bacilli: Bacillus, Clostridium, Corynebacterium
- Gram negative bacteria:
- Cocci: Neisseria
- Bacilli: Enteric, Non-Enteric, Respiratory, and Animal source bacteria
Acid-fast Staining
- Examples of acid-fast bacteria: Mycobacterium tuberculosis, Mycobacterium leprae, Nocardia, Actinomyces
Albert's Staining
- Example of bacteria that can be stained using Albert's stain: Corynebacterium diphtheriae
Shape
- Cocci: oval or spherical, may be arranged in pairs, tetrads, chains, or clusters
- Bacilli: rod-shaped, may show arrangements like coccobacilli, streptobacilli, comma-shaped, or spirella
- Spirochetes: slender, flexuous, spiral
- Actinomyces: branching filamentous
Growth and Nutrition
- Oxygen requirements:
- Aerobic: Obligate aerobe, Facultative aerobe, Microaerophilic
- Anaerobic: Obligate anaerobe, Aerotolerant anaerobe
- Carbon dioxide requirements:
- Capnophilic bacteria: require higher amount of CO2 for growth
- Temperature:
- Psychrophiles: microbes that grow within 0-20°C
- Mesophiles: microbes that grow within 25-40°C
- Thermophiles: microbes that grow within 55-80°C
- pH:
- Acidophile: microbes that grow at acidic pH
- Alkaliphile: microbes that grow at alkaline pH
- Neutrophile: microbes that grow at neutral pH
- Light:
- Phototrophs: bacteria that derive energy from sunlight
- Chemotrophs: bacteria that derive energy from chemical sources
- Osmotic pressure:
- Halophiles: microbes that can survive at high salt concentration
- Osmophiles: microbes that can survive at high sugar concentration
- Carbon source:
- Autotrophs: microbes that reduce inorganic carbon into organic compounds
- Heterotrophs: microbes that grow by using the carbon reduced by autotrophs
Motility
- Motile bacteria: Salmonella, Vibrio cholerae, Pseudomonas
- Non-motile bacteria: Staphylococcus, Shigella
Obligate Intracellular Organism
- Organisms that cannot reproduce outside the cell:
- Viruses
- Bacteria: Chlamydia, Rickettsia, Coxiella, Mycobacterium leprae
- Protozoa: Plasmodium spp., Toxoplasma gondi, Leishmania spp., Trypanosoma cruzi
- Fungi: Pneumocystis jirovecii
Pathogenicity of Bacteria
- Pathogenic microorganisms are those that cause or are capable of causing disease
- Factors that influence pathogenicity:
- Entry into the host
- Adhesion to host cells
- Propagation of the organism
- Damage to host cells by bacterial toxins or an inflammatory response
- Evasion of host secondary defenses
Virulence Factors
- Characteristics of bacteria that enhance their pathogenicity:
- Entry into the host
- Adherence to host cells
- Invasiveness
- Bacterial toxins
- Evasion of host defenses
Bacterial Toxins
- Exotoxins: proteins secreted by bacteria, can be inactivated by heat
- Endotoxins: lipopolysaccharides, integral components of gram-negative bacteria, heat-stable
- Exotoxins:
- Bind to host cells
- Have a toxic effect
- Can be inactivated by moderate heating
- Can be formaldehyde-inactivated to form toxoids
- Endotoxins:
- Release into the host's circulation following bacterial cell lysis
- Cause fever, shock, hypotension, and thrombosis
- Can be activated by macrophages, releasing cytokines, activating complement, and activating the coagulation cascade
Infections in Human Populations
- Bacterial diseases can be communicable or noncommunicable
- Communicable diseases:
- Spread from person-to-person
- Can occur as localized epidemics
- Can become worldwide pandemics
- Noncommunicable diseases:
- Not spread from person-to-person
- Do not occur as epidemics or pandemics
Classification of Bacteria
- Bacteria can be classified based on:
- Staining: Gram positive, Gram negative, Acid-fast, and Albert's staining
- Shape: Cocci, Bacilli, Spirochetes, Actinomyces
- Growth and nutrition: Oxygen requirements, Carbon dioxide requirements, Temperature, pH, Light, Osmotic pressure, and Carbon source
- Presence of flagella: With flagella (Monotrichous, Lophotrichous, Peritrichous, Amphitrichous) and Without flagella (Atrichous)
- Motility: Motile and Non-motile
Gram Staining
- Gram positive bacteria:
- Cocci: Streptococcus, Staphylococcus
- Bacilli: Bacillus, Clostridium, Corynebacterium
- Gram negative bacteria:
- Cocci: Neisseria
- Bacilli: Enteric, Non-Enteric, Respiratory, and Animal source bacteria
Acid-fast Staining
- Examples of acid-fast bacteria: Mycobacterium tuberculosis, Mycobacterium leprae, Nocardia, Actinomyces
Albert's Staining
- Example of bacteria that can be stained using Albert's stain: Corynebacterium diphtheriae
Shape
- Cocci: oval or spherical, may be arranged in pairs, tetrads, chains, or clusters
- Bacilli: rod-shaped, may show arrangements like coccobacilli, streptobacilli, comma-shaped, or spirella
- Spirochetes: slender, flexuous, spiral
- Actinomyces: branching filamentous
Growth and Nutrition
- Oxygen requirements:
- Aerobic: Obligate aerobe, Facultative aerobe, Microaerophilic
- Anaerobic: Obligate anaerobe, Aerotolerant anaerobe
- Carbon dioxide requirements:
- Capnophilic bacteria: require higher amount of CO2 for growth
- Temperature:
- Psychrophiles: microbes that grow within 0-20°C
- Mesophiles: microbes that grow within 25-40°C
- Thermophiles: microbes that grow within 55-80°C
- pH:
- Acidophile: microbes that grow at acidic pH
- Alkaliphile: microbes that grow at alkaline pH
- Neutrophile: microbes that grow at neutral pH
- Light:
- Phototrophs: bacteria that derive energy from sunlight
- Chemotrophs: bacteria that derive energy from chemical sources
- Osmotic pressure:
- Halophiles: microbes that can survive at high salt concentration
- Osmophiles: microbes that can survive at high sugar concentration
- Carbon source:
- Autotrophs: microbes that reduce inorganic carbon into organic compounds
- Heterotrophs: microbes that grow by using the carbon reduced by autotrophs
Motility
- Motile bacteria: Salmonella, Vibrio cholerae, Pseudomonas
- Non-motile bacteria: Staphylococcus, Shigella
Obligate Intracellular Organism
- Organisms that cannot reproduce outside the cell:
- Viruses
- Bacteria: Chlamydia, Rickettsia, Coxiella, Mycobacterium leprae
- Protozoa: Plasmodium spp., Toxoplasma gondi, Leishmania spp., Trypanosoma cruzi
- Fungi: Pneumocystis jirovecii
Pathogenicity of Bacteria
- Pathogenic microorganisms are those that cause or are capable of causing disease
- Factors that influence pathogenicity:
- Entry into the host
- Adhesion to host cells
- Propagation of the organism
- Damage to host cells by bacterial toxins or an inflammatory response
- Evasion of host secondary defenses
Virulence Factors
- Characteristics of bacteria that enhance their pathogenicity:
- Entry into the host
- Adherence to host cells
- Invasiveness
- Bacterial toxins
- Evasion of host defenses
Bacterial Toxins
- Exotoxins: proteins secreted by bacteria, can be inactivated by heat
- Endotoxins: lipopolysaccharides, integral components of gram-negative bacteria, heat-stable
- Exotoxins:
- Bind to host cells
- Have a toxic effect
- Can be inactivated by moderate heating
- Can be formaldehyde-inactivated to form toxoids
- Endotoxins:
- Release into the host's circulation following bacterial cell lysis
- Cause fever, shock, hypotension, and thrombosis
- Can be activated by macrophages, releasing cytokines, activating complement, and activating the coagulation cascade
Infections in Human Populations
- Bacterial diseases can be communicable or noncommunicable
- Communicable diseases:
- Spread from person-to-person
- Can occur as localized epidemics
- Can become worldwide pandemics
- Noncommunicable diseases:
- Not spread from person-to-person
- Do not occur as epidemics or pandemics
Classification of Bacteria
- Bacteria can be classified based on:
- Staining: Gram positive, Gram negative, Acid-fast, and Albert's staining
- Shape: Cocci, Bacilli, Spirochetes, Actinomyces
- Growth and nutrition: Oxygen requirements, Carbon dioxide requirements, Temperature, pH, Light, Osmotic pressure, and Carbon source
- Presence of flagella: With flagella (Monotrichous, Lophotrichous, Peritrichous, Amphitrichous) and Without flagella (Atrichous)
- Motility: Motile and Non-motile
Gram Staining
- Gram positive bacteria:
- Cocci: Streptococcus, Staphylococcus
- Bacilli: Bacillus, Clostridium, Corynebacterium
- Gram negative bacteria:
- Cocci: Neisseria
- Bacilli: Enteric, Non-Enteric, Respiratory, and Animal source bacteria
Acid-fast Staining
- Examples of acid-fast bacteria: Mycobacterium tuberculosis, Mycobacterium leprae, Nocardia, Actinomyces
Albert's Staining
- Example of bacteria that can be stained using Albert's stain: Corynebacterium diphtheriae
Shape
- Cocci: oval or spherical, may be arranged in pairs, tetrads, chains, or clusters
- Bacilli: rod-shaped, may show arrangements like coccobacilli, streptobacilli, comma-shaped, or spirella
- Spirochetes: slender, flexuous, spiral
- Actinomyces: branching filamentous
Growth and Nutrition
- Oxygen requirements:
- Aerobic: Obligate aerobe, Facultative aerobe, Microaerophilic
- Anaerobic: Obligate anaerobe, Aerotolerant anaerobe
- Carbon dioxide requirements:
- Capnophilic bacteria: require higher amount of CO2 for growth
- Temperature:
- Psychrophiles: microbes that grow within 0-20°C
- Mesophiles: microbes that grow within 25-40°C
- Thermophiles: microbes that grow within 55-80°C
- pH:
- Acidophile: microbes that grow at acidic pH
- Alkaliphile: microbes that grow at alkaline pH
- Neutrophile: microbes that grow at neutral pH
- Light:
- Phototrophs: bacteria that derive energy from sunlight
- Chemotrophs: bacteria that derive energy from chemical sources
- Osmotic pressure:
- Halophiles: microbes that can survive at high salt concentration
- Osmophiles: microbes that can survive at high sugar concentration
- Carbon source:
- Autotrophs: microbes that reduce inorganic carbon into organic compounds
- Heterotrophs: microbes that grow by using the carbon reduced by autotrophs
Motility
- Motile bacteria: Salmonella, Vibrio cholerae, Pseudomonas
- Non-motile bacteria: Staphylococcus, Shigella
Obligate Intracellular Organism
- Organisms that cannot reproduce outside the cell:
- Viruses
- Bacteria: Chlamydia, Rickettsia, Coxiella, Mycobacterium leprae
- Protozoa: Plasmodium spp., Toxoplasma gondi, Leishmania spp., Trypanosoma cruzi
- Fungi: Pneumocystis jirovecii
Pathogenicity of Bacteria
- Pathogenic microorganisms are those that cause or are capable of causing disease
- Factors that influence pathogenicity:
- Entry into the host
- Adhesion to host cells
- Propagation of the organism
- Damage to host cells by bacterial toxins or an inflammatory response
- Evasion of host secondary defenses
Virulence Factors
- Characteristics of bacteria that enhance their pathogenicity:
- Entry into the host
- Adherence to host cells
- Invasiveness
- Bacterial toxins
- Evasion of host defenses
Bacterial Toxins
- Exotoxins: proteins secreted by bacteria, can be inactivated by heat
- Endotoxins: lipopolysaccharides, integral components of gram-negative bacteria, heat-stable
- Exotoxins:
- Bind to host cells
- Have a toxic effect
- Can be inactivated by moderate heating
- Can be formaldehyde-inactivated to form toxoids
- Endotoxins:
- Release into the host's circulation following bacterial cell lysis
- Cause fever, shock, hypotension, and thrombosis
- Can be activated by macrophages, releasing cytokines, activating complement, and activating the coagulation cascade
Infections in Human Populations
- Bacterial diseases can be communicable or noncommunicable
- Communicable diseases:
- Spread from person-to-person
- Can occur as localized epidemics
- Can become worldwide pandemics
- Noncommunicable diseases:
- Not spread from person-to-person
- Do not occur as epidemics or pandemics
Classification of bacteria based on gram staining, acid-fast staining, and Albert's staining, including characteristics of gram positive and gram negative bacteria.
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