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Microbiology Exam 3 > Chapter 20: Objectives > Flashcards

Chapter 20: Objectives Flashcards

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1
Q

List three structural features of Neisseria that contribute to its pathogenicity.

A
  • Fimbriae
  • Capsules
  • Variable cell wall antigens composed of lipooligosaccharide
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2
Q

Compare and contrast the symptoms of gonorrhea in men and women.

A

Gonorrhea in men:
- Painful urination and pus filled discharge

Gonorrhea in women:
- Often asymptomatic
- Can trigger pelvic inflammatory disease, proctitis, gingivitis, pharyngitis
Infection of children can result during childbirth (ophthalmia neonatorum)

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3
Q

Gonorrhea in men

A
  • Painful urination
  • Pus filled charge
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4
Q

Gonorrhea in women

A
  • Often asymptomatic
  • Can trigger pelvic inflammatory disease, proctitis, gingivitis, pharyngitis
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5
Q

Discuss the difficulties researchers face in developing an effective vaccine
against Neisseria gonorrhoeae

A
  • Treatment is complicated due to resistant strains
  • Broad spectrum antimicrobial drugs like cephalosporins
  • Long term immunity does not develop due to variable surface antigens
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6
Q

What is cultured in Thayer-Martin agar

A

Neisseria gonorrhoeae

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7
Q

Diagnosis of Neisseria gonorrhoeae

A
  • Asymptomatic cases identified with genetic probes
  • Gram negative diplococci in pus
  • Can be cultured in Thayer-Martin agar
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8
Q

Describe how meningococci: Neisseria meningitidis survive and thrive in humans

A
  • 13 antigenic strains cause disease; A, B, C, and W135
  • Can survive in neutrophils and macrophages
  • Polysaccharide capsules resists lytic enzymes of phagocytes
  • Neisseria meningitidis causes blebbing - a process of shedding outer membrane
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9
Q

What is blebbing

A
  • A process in which the bacterium sheds extrusions of outer membrane
  • Much of the damage caused by N. meningitidis results from blebbing
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10
Q

How is meningococcus: Neisseria meningitis transmitted?

A
  • By respiratory droplets
  • Bacteria transmitted among people living in close contact
  • Most common cause of meningitis in individuals under 20 years
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11
Q

Meningococcal meningitis

A

Can cause death within 6 hours of symptoms:
- Abrupt sore throat
- Fever
- Headache
- Stiff neck
- Vomiting
- Convulsions

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12
Q

Petechiae

A
  • Minute hemorrhagic skin lesions on the trunk and lower extremities, can combine together to form large black lesions
  • Caused by Meningococcal
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13
Q

Meningococcal septicemia

A
  • Also known as blood poisoning can also be life threatening
  • LOS may trigger shock
  • Petechiae - minute hemorrhagic skin lesions on the trunk and lower extremities, can combine together to form large black lesions
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14
Q

Discuss the epidemiology of meningococcal diseases

A
  • Most common cause of meningitis in individuals under 20 years
  • Respiratory droplets transmit the bacteria among people living in close contact, especially families, soldiers living in barracks, prisoners, and college students living in dormitories
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15
Q

Diagnosis of Neisseria meningitidis

A
  • Gram negative diplococci in phagocytes of the cerebrospinal fluid
  • Physician obtain a sample of cerebrospinal fluid using a needle inserted into the lower spinal canal; spinal tap
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16
Q

How to distinguish between Neisseria gonorrhoeae and N meningitidis

A
  • N. gonorrhoeae is cultured on Thayer-Martin agar
  • N. meningitidis can oxidize maltose in laboratory culture
17
Q

Neisseria meningitidis treatment

A
  • Intravenous antibiotics like ceftraxone, a cephalosporin
18
Q

Prevention of Neisseria meningitidis

A
  • Asymptomatic carriers are common which make eradication of meningococcal disease is unlikely
  • Vaccination against strains A, C, Y, and W135
19
Q

Describe how members of the family Enterobacteriaceae are distinguished from
members of the family Pasteurellaceae.

A
  • Distinguish between members of the two families by preforming an oxidase test;
  • Enterobacteriaceae are oxidase negative
  • Pasteurellaceae are oxidase positive
20
Q

Discuss how to distinguish between members of the family Enterobacteriaceae in the laboratory

A
  • Biochemical tests
  • Motility
  • Colonial characteristics on a variety of selective and non-selective media (EX. MacConkey agar and blood agar)
21
Q

All enterobacteriaceae bacteria are:

A
  • Also known as enteric bacteria
  • Gram negative
  • Oxidase negative
  • Able to metabolize nitrate to nitrite

Outer membrane that contains lipopolysaccharide:
- A core polysaccharide (common antigen)
- O polysaccharide
- Lipid A

22
Q

Six virulence factors found in members of the family Enterobacteriaceae

A
  • Fimbria
  • Exotoxin
  • Adhesin
  • Plasmid (virulence genes)
  • Iron-binding protein
  • Hemolysin
23
Q

Enterobacteriaceae virulence factor: Exotoxin

A

Exotoxins that cause a variety of symptoms such as diarrhea frequently located on plasmids, which increases the likelihood that they will be transferred among bacteria

24
Q

Enterobacteriaceae virulence factor: Adhesin

A

Fimbriae and proteins called adhesins enable the bacteria to attach tightly to human cells

25
Q

Enterobacteriaceae virulence factor: Plasmid

A

Plasmid-encoded enzymes that degrade antimicrobial drugs conveying drug resistance

26
Q

Enterobacteriaceae virulence factor: Iron-binding protein

A

Also called siderophores that capture iron and make it available to the bacteria

27
Q

Enterobacteriaceae virulence factor: Hemolysins

A

Release nutrients such as iron by lysing red blood cells

28
Q

Four antigen factors found in members of the family Enterobacteriaceae

A
  • Outer membrane: common antigen, O antigen, lipid A
  • Type III secretion system
  • Capsular antigens (K, Vi in Salmonella)
  • Flagellar antigens (H)
29
Q

Antigen factor of Enterobacteriaceae: Type III secretion system

A
  • A complex structure composed of 20 different polypeptides that is synthesized by several pathogenic enteric species
  • Like a hypodermic needle, the system spans the two membranes and peptidoglycan of the bacterial cell and inserts through a host cell’s cytoplasmic membrane
30
Q

Diagnosis of Enterobacteriaceae

A
  • Enteric bacteria in urine, blood, and cerebrospinal fluid
  • Biochemical tests rapidly identify enteric bacteria
31
Q

Culturing members of Enterobacteriaceae from clinical specimen

A
  • Eosin methylene blue (EMB) agar
  • MacConkey agar
32
Q

Treatment of Enterobacteriaceae

A
  • Diarrhea typically self limited, expulsion of the organisms from the body is often more effective, which involves treating the symptoms with fluid and electrolyte replacement
  • Internal infections treated with antimicrobials
33
Q

Treatment of Enterobacteriaceae: Diarrhea

A
  • Self limited: Expulsion of the organisms from the body is often more effective
  • Involves treating the symptoms with fluid and electrolyte replacement
34
Q

Treatment of Enterobacteriaceae: Internal infections

A

Antimicrobials

35
Q

Prevention of Enterobacteriaceae

A
  • Good personal hygiene
  • Proper sewage control
36
Q

Compare and contrast Enterobacter, Hafnia, and Citrobacter

A
  • Coliforms
  • Reside in digestive tracts of animals, humans, soil, water, decaying vegetation and sewage
  • Involved in healthcare-associated infections of blood, wounds, surgical incisions, and urinary tracts of immunocompromised patients
  • Enterobacter can be a contaminant of dairy products
37
Q

Escherichia coli can cause:

A
  • Septicemia
  • Urinary tract infections (UTIs - urethritis, cystitis, pyelonephritis)
  • Meningitis
  • Gastroenteritis (most common)

Microbiology Exam 3 (6 decks)

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