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Questions and Answers
What is the primary mode of transmission for Vibrio cholerae?
What is the primary mode of transmission for Vibrio cholerae?
- Direct contact with infected individuals
- Contaminated seafood
- Airborne droplets
- Fecal contamination of water (correct)
Which virulence factor of Vibrio cholerae leads to severe diarrhea?
Which virulence factor of Vibrio cholerae leads to severe diarrhea?
- Fimbriae
- Hemolysin
- Capsule
- Cholera toxin (correct)
What kind of infections is Pseudomonas aeruginosa most commonly associated with?
What kind of infections is Pseudomonas aeruginosa most commonly associated with?
- Foodborne illnesses
- Viral infections in children
- Nosocomial infections, particularly in burn patients (correct)
- Respiratory infections post-surgery
What structural feature of Neisseria meningitidis helps it evade the immune response?
What structural feature of Neisseria meningitidis helps it evade the immune response?
Which of the following is a characteristic feature of Pseudomonas aeruginosa?
Which of the following is a characteristic feature of Pseudomonas aeruginosa?
What is the main consequence of untreated meningitis caused by Neisseria meningitidis?
What is the main consequence of untreated meningitis caused by Neisseria meningitidis?
The characteristic appearance of Neisseria cells under crystal violet staining is:
The characteristic appearance of Neisseria cells under crystal violet staining is:
Which of the following is NOT a characteristic of Vibrio species?
Which of the following is NOT a characteristic of Vibrio species?
What is the primary virulence factor of C.tetani that leads to muscle rigidity?
What is the primary virulence factor of C.tetani that leads to muscle rigidity?
What characteristic of Neisseria gonorrhoeae is used for diagnosis?
What characteristic of Neisseria gonorrhoeae is used for diagnosis?
Which organism is responsible for causing botulism?
Which organism is responsible for causing botulism?
What characteristic do Staphylococcus and Streptococcus bacteria share?
What characteristic do Staphylococcus and Streptococcus bacteria share?
Which disease is associated with Rickettsia prowazekii?
Which disease is associated with Rickettsia prowazekii?
What is the lethal dose of botulinum toxin, making it one of the deadliest poisons?
What is the lethal dose of botulinum toxin, making it one of the deadliest poisons?
What is the primary habitat for Bacteroides species in the human body?
What is the primary habitat for Bacteroides species in the human body?
What is a significant characteristic of Treponema pallidum?
What is a significant characteristic of Treponema pallidum?
Which species is classified as a facultative anaerobic, heterotrophic G+ve non-sporing rod?
Which species is classified as a facultative anaerobic, heterotrophic G+ve non-sporing rod?
Which of the following best describes Chlamydia?
Which of the following best describes Chlamydia?
Which organism is an opportunistic pathogen commonly associated with nosocomial infections?
Which organism is an opportunistic pathogen commonly associated with nosocomial infections?
What type of genome do Bacteroides species have?
What type of genome do Bacteroides species have?
What is a common transmission method for Rickettsia?
What is a common transmission method for Rickettsia?
What role do Bacteroides species play in the human gut?
What role do Bacteroides species play in the human gut?
What characteristic distinguishes Gram-positive bacteria from Gram-negative bacteria?
What characteristic distinguishes Gram-positive bacteria from Gram-negative bacteria?
What virulence factor significantly increases the virulence of encapsulated strains of S.pneumoniae?
What virulence factor significantly increases the virulence of encapsulated strains of S.pneumoniae?
Which of the following statements about Escherichia coli is true?
Which of the following statements about Escherichia coli is true?
Which genera of bacteria is classified under the Proteobacteria phylum?
Which genera of bacteria is classified under the Proteobacteria phylum?
Which of the following diseases is NOT caused by a species of Mycobacterium?
Which of the following diseases is NOT caused by a species of Mycobacterium?
What is a common source of infection for Salmonella enterica?
What is a common source of infection for Salmonella enterica?
What characteristic is associated with Mycobacterium tuberculosis that aids in its identification?
What characteristic is associated with Mycobacterium tuberculosis that aids in its identification?
What type of agar is used for identifying Enterobacteriaceae?
What type of agar is used for identifying Enterobacteriaceae?
Which of the following correctly describes the growth characteristics of M.tuberculosis?
Which of the following correctly describes the growth characteristics of M.tuberculosis?
What role does E. coli play in the synthesis of vitamin K?
What role does E. coli play in the synthesis of vitamin K?
What type of bacteria primarily make up the Actinobacteria group mentioned?
What type of bacteria primarily make up the Actinobacteria group mentioned?
Which virulence factor is common to both E. coli and Salmonella?
Which virulence factor is common to both E. coli and Salmonella?
What is a distinguishing feature of Gram-negative bacteria's cell wall?
What is a distinguishing feature of Gram-negative bacteria's cell wall?
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Study Notes
Classification of Bacteria
- Gram Staining:
- Gram Positive: Purple, thick peptidoglycan layer.
- Gram Negative: Pink, thin peptidoglycan layer, more pathogenic potential.
- Classification Methods:
- Phenetic: Based on observable characteristics (morphology, metabolic type).
- Phylogenetic: Based on genetic information (ribosomal RNA, DNA sequences).
Important Gram-Negative Bacteria
- Proteobacteria:
- Contains many pathogenic genera including Escherichia, Salmonella, Vibrio, Pseudomonas, Neisseria, Rickettsia.
- Bacteroidetes:
- Notable genus: Bacteroides.
- Spirochaetes:
- Notable genus: Treponema.
Escherichia Infection Characteristics
- E. coli:
- Facultative anaerobic, heterotrophic, rod-shaped, commonly found in human and animal guts.
- Some strains: Pathogenic (O157, O111) causing foodborne illness.
- Beneficial strains: Produce vitamin K.
- Symptoms of pathogenic strains: Diarrhea, fever.
- Virulence factors: Endotoxins (common in all Gram-negative), enterotoxins (secreted).
Salmonella Infections
- Salmonella:
- Facultative anaerobic, heterotrophic, rod-shaped.
- S. enterica: Common foodborne infection (e.g., from uncooked eggs, chicken).
- S. typhi: Causes typhoid fever, potentially fatal; transmitted via contaminated water.
- Virulence factors: Endotoxins, enterotoxins, cytotoxins.
Identifying Enterobacteriaceae
- Selective and differential agars used for identification.
- E. coli: Ferments lactose leading to acidic pH.
- Salmonella: Produces iron precipitate, visible as black colonies on agar.
Vibrio Infections
- Vibrio:
- Curved, motile, facultative anaerobes primarily from marine environments.
- V. cholerae: Causes cholera, severe diarrhea; virulence factor cholera toxin— stimulates secretion of electrolytes leading to dehydration.
Pseudomonas Infections
- Pseudomonas aeruginosa:
- Aerobic, motile, opportunistic pathogen; commonly found in soil and water.
- Virulence factors include antibiotic resistance and enzymes that damage host tissues.
- Associated with nosocomial infections, particularly in burn victims and surgical patients.
Neisseria Infections
- Neisseria:
- Aerobic, heterotrophic diplococci found in human mucous membranes.
- N. gonorrhoeae: Causes gonorrhea; diagnosed via microscopic examination.
- N. meningitidis: Causes meningitis; has a rapid progression requiring immediate treatment.
Rickettsia Characteristics
- Rickettsia:
- Aerobic, heterotrophic coccobacilli; intracellular parasites requiring host cells for growth.
- Transmitted via arthropod bites or feces, causing various fever illnesses.
- R. prowazekii: Causes epidemic typhus with high mortality in overcrowded conditions.
Bacteroides and Their Functions
- Bacteroides:
- Obligate anaerobes, major component of normal gut flora, can be opportunistic pathogens.
- B. fragilis: Causes infections if the bacteria escape the gut; virulence factors include antibiotic resistance.
Treponema Infections
- Treponema:
- Anaerobic, obligate parasites requiring host for nutrition.
- T. pallidum: Causes syphilis; characterized by stages of symptoms affecting various body systems.
Gram Positive Bacteria Overview
- Both Gram-positive and Gram-negative bacteria have significant medical implications.
Chlamydia Infections
- Chlamydia:
- Aerobic, heterotrophic, obligate intracellular cocci; causes STIs and eye infections.
- Cannot be cultured on agar; relies on host cells for energy.
Botulinum and Tetanus Overview
- C. tetani: Causes tetanus characterized by muscle rigidity; virulence factor is tetanospasmin, requires deep wounds.
- C. botulinum: Causes botulism, a potent food poisoning due to botulinum toxin, present in soil.
Lactobacillus Function
- Lactobacillus:
- Non-pathogenic, facultative anaerobes crucial for yogurt and cheese production; beneficial gut flora competitor.
Staphylococcus Characteristics
- Staphylococcus:
- Includes both pathogenic species (like S. aureus) and normal flora.
- Known for antibiotic resistance and survival in stressful environments.
Streptococcus Overview
- Streptococcus:
- Includes beneficial species for dairy fermentation and harmful ones causing diseases like pneumonia and scarlet fever.
Mycobacterium Importance
- Mycobacterium:
- Includes M. tuberculosis (causes TB) and M. leprae (leprosy).
- Known for their waxy cell wall contributing to their virulence and resistance to stress.
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