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What is the shape of individual cocci in Neisseria species?
What is the shape of individual cocci in Neisseria species?
Which antibiotic is ineffective against Neisseria species?
Which antibiotic is ineffective against Neisseria species?
What is the medium used for culturing Neisseria species?
What is the medium used for culturing Neisseria species?
What is the characteristic of Neisseria gonorrhea colonies?
What is the characteristic of Neisseria gonorrhea colonies?
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What is the habitat of Neisseria gonorrhea?
What is the habitat of Neisseria gonorrhea?
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What is the gold standard test for diagnosing Neisseria gonorrhea?
What is the gold standard test for diagnosing Neisseria gonorrhea?
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What is the characteristic of Neisseria meningitidis colonies?
What is the characteristic of Neisseria meningitidis colonies?
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What is the most severe form of meningococcemia?
What is the most severe form of meningococcemia?
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What is the factor required by Haemophilus influenzae for growth?
What is the factor required by Haemophilus influenzae for growth?
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What is the result of the Quellung reaction?
What is the result of the Quellung reaction?
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What is the characteristic of Haemophilus influenzae growth?
What is the characteristic of Haemophilus influenzae growth?
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What is the disease caused by Haemophilus ducreyi?
What is the disease caused by Haemophilus ducreyi?
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What is the characteristic of Haemophilus influenzae colonies?
What is the characteristic of Haemophilus influenzae colonies?
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What is the factor that can be replaced by nicotinamide adenine dinucleotide (NAD) in Haemophilus influenzae growth?
What is the factor that can be replaced by nicotinamide adenine dinucleotide (NAD) in Haemophilus influenzae growth?
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What type of agar is used to culture Pseudomonas aeruginosa?
What type of agar is used to culture Pseudomonas aeruginosa?
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Which of the following is a characteristic of Pseudomonas aeruginosa?
Which of the following is a characteristic of Pseudomonas aeruginosa?
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What is the habitat of Influenza?
What is the habitat of Influenza?
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What is the mode of transmission of Influenza?
What is the mode of transmission of Influenza?
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What is a characteristic of Pertussis?
What is a characteristic of Pertussis?
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What is the vaccine used to prevent Pertussis?
What is the vaccine used to prevent Pertussis?
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What type of medium is used to culture Salmonella spp.?
What type of medium is used to culture Salmonella spp.?
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What is a characteristic of Salmonella spp.?
What is a characteristic of Salmonella spp.?
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What is the mode of transmission of Salmonella enteritidis?
What is the mode of transmission of Salmonella enteritidis?
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Which of the following bacteria is non-lactose-fermenting and urease-positive?
Which of the following bacteria is non-lactose-fermenting and urease-positive?
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What is the characteristic of the colonies of Shigella spp. on XLD agar?
What is the characteristic of the colonies of Shigella spp. on XLD agar?
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What is the characteristic of the swarming motility of Proteus mirabilis?
What is the characteristic of the swarming motility of Proteus mirabilis?
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What is the most common cause of bacterial gastroenteritis?
What is the most common cause of bacterial gastroenteritis?
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Which of the following bacteria is associated with the formation of staghorn calculi?
Which of the following bacteria is associated with the formation of staghorn calculi?
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What is the characteristic of the colonies of Escherichia coli on EMB agar?
What is the characteristic of the colonies of Escherichia coli on EMB agar?
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Which of the following bacteria is associated with the formation of Guillain-Barré syndrome?
Which of the following bacteria is associated with the formation of Guillain-Barré syndrome?
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Study Notes
Gram-Negative Organisms
Diplococci
Neisseria species
- Aerobic, Gram-negative, nonmotile, kidney bean-shaped diplococci
- Oxidase test positive
- Oxidize carbohydrates
- Culture: Thayer-Martin/Modified Thayer-Martin on Mueller-Hinton Agar with 5% chocolate sheep blood
- Antibiotics: Colistin (inhibits growth of other Gram-negative bacteria except Neisseria), Vancomycin (inhibits Gram-positive), and Nystatin (inhibits yeast)
Neisseria gonorrhea
- Small, mucoid, oxidase-positive colonies
- Ferments glucose only
- Culture Appearance: "Opaque Colonies" (specimen from symptomatic male), "Transparent Colonies" (specimen from asymptomatic male)
- Habitat: human genital tract
- Transmission: sexual contact or during passage through birth canal
- Specimens: urethra, cervix, rectum, conjunctiva, throat, synovial fluid
- Gram stain: many diplococci within PMNS (presumptive diagnosis)
- Gold standard test: Nucleic Acid Amplification Tests (NAATs)
Spectrum of Disease
- Gonococcal urethritis: urethritis and epididymitis in men
- Ophthalmia neonatorum: purulent conjunctivitis in newborns
- Cervical gonorrhea: can progress to pelvic inflammatory disease
Neisseria meningitidis
- Encapsulated with large polysaccharide capsule
- Ferments glucose and maltose
- Oxidase-positive colonies on chocolate agar
- Habitat: URT
- Transmission: via respiratory droplets
- High carriage rate in close quarters (dormitories, camps, travel)
Spectrum of Disease
- Meningitis: most common cause among 2-18 years old
- Meningococcemia: meningococci disseminates into the bloodstream, multiorgan disease, consumptive coagulopathy, petechial or purpuric rash (purpura fulminans)
- Waterhouse-Friderichsen Syndrome: most severe form of meningococcemia, high fever, shock, widespread purpura, disseminated intravascular coagulation, thrombocytopenia, adrenal insufficiency
Coccobacilli
Haemophilus influenzae
- Found in the upper respiratory tract
- Non-motile, small Gram-negative (coccobacillary) rods
- Fastidious organism
- Flat, grayish, translucent colonies on chocolate agar
- Satellite phenomenon around S. aureus colonies
- Hemolysis by S. aureus liberates factor V needed by H. influenzae
- Positive quellung test
Quellung Test
- A biochemical reaction in which antibodies bind to a bacterial capsule, allowing species with a positive Quellung reaction to be visualized under a microscope.
Diagnosis
- Requires factor X (hemin) and V (NAD) for growth
- X -- hemin
- V - NAD (can be replaced by nicotinamide adenine dinucleotide)
- Grown on IsoVitaleX-enriched chocolate agar
- Satellite phenomenon: grows around colonies of Staphylococci
Spectrum of Disease
- Sinusitis, otitis media, pneumonia
- Meningitis
- Epiglottitis
- COPD exacerbations
Haemophilus ducreyi
- Small Gram-negative rods in strands
- Requires X factor but not V factor
- Causes chancroid
Bordetella pertussis
- Minute, Gram-negative coccobacilli resembling H. influenza
- Bordet-Gengou agar or Regan-Lowe charcoal medium
- Habitat: URT
- Transmission: via respiratory droplets
- Spectrum of Disease: pertussis (hacking coughs accompanied by production of copious amounts of mucus, that end with an inspiratory "whoop")
Bacilli
Pseudomonas aeruginosa
- Obligate aerobe
- Oxidase-positive, non-lactose-fermenter
- Culture: grown on Cetrimide agar
- Greenish, metallic colonies on blood agar
- Produces pyocyanin, pyoverdin
- Sweet grape-like odor
- Habitat: environmental water sources (e.g., humidifiers)
- Inhabits skin, URT, and colon of people
- Transmission: via water aerosoles, aspiration, fecal contamination
- Spectrum of Disease:
- Skin and Soft Tissue Infections: burn wound infections, hot tub folliculitis, green nail syndrome
- Ear Infections: otitis externa, swimmer's ear, chronic suppurative otitis media
- Pneumonia: ventilator-acquired pneumonia, high-risk CAP in immunocompromised
- Urinary Tract Infection: one of the most common causes of nosocomial UTIs
Salmonella spp.
- Facultative anaerobes
- Non-lactose-fermenting
- Produces H2S
- Motile
- Widal test detects antibodies in patient's serum
- Cultured in XLD medium
- Habitat: human colon (S. typhi), enteric tract of humans and animals (S. enteritidis)
- Transmission: via fecal-oral route
- Spectrum of Disease:
- Enterocolitis: nausea and vomiting, then progresses to abdominal pain and non-bloody diarrhea
- Typhoid fever
Shigella spp.
- Slender, non-motile Gram-negative rods
- Facultative anaerobes
- Oxidase-negative
- Non-lactose-fermenter
- H2S non-producer
- Culture medium: XLD
- Convex, circular, transparent colonies with intact edges
- Spectrum of Disease: enterocolitis
Proteus Mirabilis
- Facultative anaerobic gram-negative rods
- Non-lactose-fermenting
- Urease-positive
- Swarming motility
- Wave-like pattern extending from the point of inoculation
- Spectrum of Disease: complicated UTI, UTI associated with nephrolithiasis
Escherichia coli
- Facultative gram-negative rods
- Lactose-fermenting colonies on EMB or MacConkey agar
- Green metallic sheen on EMB agar
- Habitat: human colon
- Colonizes vagina and urethra
- Transmission: ascending infection in UTI, during birth in neonatal meningitis, fecal-oral route in diarrhea
- Spectrum of Disease:
- UTI: most common cause
- Intestinal infection: 4 strains (ETEC, EPEC, EHEC, EIEC)
- Neonatal meningitis: 2nd most common cause
- Hemolytic Uremic Syndrome: triad of hemolytic anemia, thrombocytopenia, and uremia
- Pyogenic liver abscess
Klebsiella pneumoniae
- Urease positive
- Facultative, non-motile, gram-negative rods with large polysaccharide capsule
- Habitat: URT and GIT
- Transmission: aspiration/inhalation or ascending spread of fecal
- Spectrum of Disease:
- Lobar Pneumonia
- UTI
Campylobacter jejuni
- Comma- or S-shaped
- Microaerophilic
- Positive oxidase and catalase tests
- Grows well at 42°C on Skirrow agar
- Habitat: human and animal feces (cattle, chickens, and dogs)
- Transmission: via fecal-oral route
- Spectrum of Disease: one of the most common causes of bacterial gastroenteritis, watery, foul-smelling diarrhea followed by bloody stools accompanied by fever and severe abdominal pain
- Disease association: Guillain-Barré syndrome, reactive arthritis (Reiter syndrome)
Vibrio cholerae
- Comma-shaped gram-negative rods
- Motile
- Shooting star motility
- Oxidase-positive
- Ferments sucrose and mannose but not arabinose
- Spectrum of Disease: cholera, one of the most common causes of bacterial gastroenteritis
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Description
This quiz covers the characteristics of Neisseria species, a type of gram-negative diplococcus. It includes information on their growth conditions, shape, and reactions to oxidase tests and antibiotics.
