Medicinally Important Bacteria: Gram Negatives Part 1

Questions and Answers

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?

Fimbriae

Hemolysin

Capsule

Cholera toxin (correct)

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?

Capsule Signup and view all the answers

Which of the following is a characteristic feature of Pseudomonas aeruginosa?

Motility by polar flagella Signup and view all the answers

What is the main consequence of untreated meningitis caused by Neisseria meningitidis?

Mental confusion and potentially death Signup and view all the answers

The characteristic appearance of Neisseria cells under crystal violet staining is:

Purple Signup and view all the answers

Which of the following is NOT a characteristic of Vibrio species?

Causes infections primarily from freshwater sources Signup and view all the answers

What is the primary virulence factor of C.tetani that leads to muscle rigidity?

Tetanospasmin Signup and view all the answers

What characteristic of Neisseria gonorrhoeae is used for diagnosis?

Microscopic examination Signup and view all the answers

Which organism is responsible for causing botulism?

C.botulinum Signup and view all the answers

What characteristic do Staphylococcus and Streptococcus bacteria share?

Both are G+ve cocci. Signup and view all the answers

Which disease is associated with Rickettsia prowazekii?

Epidemic typhus Signup and view all the answers

What is the lethal dose of botulinum toxin, making it one of the deadliest poisons?

1 microgram Signup and view all the answers

What is the primary habitat for Bacteroides species in the human body?

Gut Signup and view all the answers

What is a significant characteristic of Treponema pallidum?

Uses axial filaments for corkscrew motility Signup and view all the answers

Which species is classified as a facultative anaerobic, heterotrophic G+ve non-sporing rod?

Lactobacillus acidophilus Signup and view all the answers

Which of the following best describes Chlamydia?

Obligate aerobic parasites that cannot be grown on agar Signup and view all the answers

Which organism is an opportunistic pathogen commonly associated with nosocomial infections?

Staphylococcus aureus Signup and view all the answers

What type of genome do Bacteroides species have?

Small degenerate genome Signup and view all the answers

What is a common transmission method for Rickettsia?

Bites or feces from arthropods Signup and view all the answers

What role do Bacteroides species play in the human gut?

Beneficial organisms that assist in digestion Signup and view all the answers

What characteristic distinguishes Gram-positive bacteria from Gram-negative bacteria?

Presence of a thick peptidoglycan layer Signup and view all the answers

What virulence factor significantly increases the virulence of encapsulated strains of S.pneumoniae?

Capable of alpha-haemolysis Signup and view all the answers

Which of the following statements about Escherichia coli is true?

Most strains are beneficial and part of normal flora. Signup and view all the answers

Which genera of bacteria is classified under the Proteobacteria phylum?

Pseudomonas Signup and view all the answers

Which of the following diseases is NOT caused by a species of Mycobacterium?

Scarlet fever Signup and view all the answers

What is a common source of infection for Salmonella enterica?

Uncooked eggs and chicken Signup and view all the answers

What characteristic is associated with Mycobacterium tuberculosis that aids in its identification?

Waxy cell wall and acid-fast staining Signup and view all the answers

What type of agar is used for identifying Enterobacteriaceae?

Selective and differential agar Signup and view all the answers

Which of the following correctly describes the growth characteristics of M.tuberculosis?

Obligate pathogen with slow growth and no environmental reservoir Signup and view all the answers

What role does E. coli play in the synthesis of vitamin K?

Biosynthesizes vitamin K Signup and view all the answers

What type of bacteria primarily make up the Actinobacteria group mentioned?

Gram-positive filaments or rods Signup and view all the answers

Which virulence factor is common to both E. coli and Salmonella?

Enterotoxin Signup and view all the answers

What is a distinguishing feature of Gram-negative bacteria's cell wall?

Presence of an outer membrane Signup and view all the answers

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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Description

This quiz explores the characteristics of medicinally important Gram-negative bacteria, focusing on their unique cell wall structure and pathogenicity. It covers classification based on phenotypic traits such as Gram reaction, morphology, and other factors. Test your understanding of this essential topic in microbiology.