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Medical Microbiology > Lecture 11 > Flashcards

Lecture 11 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What are the main characteristics of the Bordetella species?

A

super small gram– coccobacillus (short rods), strictly aerobic and non-invasive but produces many toxins

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2
Q

What is the reservoir for Bordetella?

A

humans and some animals

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3
Q

What are the 3 species of Bordetella bacteria discussed?

A

B. pertussis, B. parapertussis, B. bronchiseptica

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4
Q

Which of the 3 species discussed is the most important?

A

B. pertussis

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5
Q

What is B. parapertussis?

A

a species of Bordetella similar to B. pertussis that causes a milder form of pertussis || “para” = resembling=similar

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6
Q

What does “pertussis” mean?

A

“per” = severe and “tussis” = cough&raquo_space; severe cough

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7
Q

What does “bronchiseptica” stand for?

A

“bronchi” = bronchus=trachea and “septica” = septic=infection&raquo_space; infection of bronchus

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8
Q

What is B. bronchiseptica?

A

species of Bordetella that causes respiratory infection in animals which can be passed onto humans causing a -pertussis-like disease || zoonotic

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9
Q

What are the main characteristics of B. pertussis?

A

same as all Bordetella but: non-motile and not easy to grow; very sensitive to sunlight and dry environments

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10
Q

What kind of media can B. pertussis only grow on and why?

A

complex media with presence of blood because it is nutritionally fastidious

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11
Q

What is the reservoir for B. pertussis? What microenvironment is it part of?

A

humans, part of the normal flora in adults

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12
Q

What kind of pathogen is B. pertussis considered to be and why?

A

mucosal pathogen because it colonizes the mucosal epithelial membranes of the respiratory tract

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13
Q

What is one of the most contagious and easily transmitted respiratory disease known?

A

pertussis

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14
Q

What is the mode of transmission with B. pertussis?

A

airborne (droplet nuclei) and direct contact

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15
Q

What disease does B. pertussis cause?

A

pertussis aka: whooping cough | respiratory disease in kids over 5yo more commonly and in some adults

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16
Q

Is pertussis a new or old disease and why?

A

old disease, first epidemic reported around 1500s

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17
Q

Who isolated B. pertussis and when?

A

1901 - Bordet and Gengou @ Pasteur Institute (France)

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18
Q

What is the origin of pertussis? (theoretically) What supports this?

A

originally infection of ducks but passed on to humans after the domestication of ducks — supported by evolutionary evidence

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19
Q

How many pertussis cases/year in the US?

A

~25,000

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20
Q

What continent does pertussis commonly occur at?

A

Africa

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21
Q

What are the causes of a significant increase in pertussis in older children and adults in recent years after the introduction of vaccine?

A

anti-vaccination and the vaccine wears off over time and booster-shots are not always taken = susceptible to infection

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22
Q

What is the incubation period for patients with pertussis disease?

A

1-2 weeks

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23
Q

What is the first (1st) stage symptom of pertussis? How long does it last for?

A

cold-like lasting for 1-2 weeks | will see a peak in bacterial numbers but declines

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24
Q

What is the second (2nd) stage symptom of pertussis? How long does it last for?

A

more specific symptoms to pertussis: dry cough, excess mucus, vomiting, cyanosis, weight loss | several weeks

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25
Q

What is the sequence of events of B. pertussis infection?

A

bacterium enters host &raquo_space; multiplies &raquo_space; spreads to parts of respiratory tract &raquo_space; colonize and produce toxins

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26
Q

What are the 2 modes of pathogenesis of B. pertussis?

A

colonizes respiratory ciliated epithelial cells but doesn’t invade and causes damage to localized tissue by producing toxins along with other virulence factors

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27
Q

What are the 8 major virulence factors of B. pertussis?

A

FHA, peractin, pili, 3 toxins: pertussis, tracheal cytotoxin, adenylate cyclase, and LPS A and X

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28
Q

What does FHA stand for? What is it?

A

filamentous hemagglutination adhesin | a protective antigen that is already used in vaccine production

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29
Q

What is peractin?

A

autotransporter adhesin, also a protective antigen

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30
Q

What physiological effect does FHA have on the host?

A

adherence and alter’s host’s innate immunity

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31
Q

What physiological effect does peractin have on the host? Is this being used for treatment?

A

adherence, not used for treatment

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32
Q

What function does the pili serve for B. pertussis?

A

adherence to respiratory epithelium

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33
Q

What kind of toxin is and what physiological effect does the pertussis toxin have on the host? What toxin does it resemble?

A

AB toxin, impairs immunoresponses against bacterium | resembles cholera toxin

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34
Q

What physiological effect does the adenylate cyclase toxin have on the host?

A

mimics pertussis toxin, increases capillary permeability thus leads to edema, hemolytic activity

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35
Q

What endotoxin does B. pertussis have? What is it’s physiological effect on the host? What can this endotoxin be used for?

A

LPS-A and LPS-X | fever; used as an adjuvant

36
Q

What physiological effect does the tracheal cytotoxin have?

A

kills ciliated respiratory epithelial cells; cytopathological damage to tracheal epithelia

37
Q

What is the tracheal cytotoxin of B. pertussis? What can this toxin be used for?

A

murein, part of cell wall that when the bacteria is lysed/cell wall breaks down = cytotoxin is released | used as an adjuvant

38
Q

What is an adjuvant?

A

substance that helps the host’s immune system

39
Q

What system is unique to B. pertussis? What is it used for?

A

2-component regulatory system for signal transduction

40
Q

What are the 2 components of the 2-component regulatory system?

A

sensor and regulator

41
Q

What is the function the 2-component regulatory system?

A

controls the expression of the virulence factors and pertussis toxin

42
Q

What is the “sensor” component of the 2-component regulatory system? Where is it located?

A

located on cytoplasmic membrane | protein kinase that senses the environmental for a signal

43
Q

What is the “regulator” component of the 2-component regulatory system? Where is it located?

A

located in the cytoplasm | transcription factor that interacts with specific genes on DNA

44
Q

How does the 2-component regulatory system work? (sequence of events)

A

Environmental signal activates “sensor” (protein kinase) &raquo_space; “sensor” phosphorylates “regulator” &raquo_space; “regulator” interacts with specific gene on DNA (of B. pertussis) to stimulate or reduce expression of speciic gene

45
Q

In which Gram+ bacteria species is found to have the 2-component regulatory system?

A

Salmonella

46
Q

In which Gram– bacteria species is found to have the 2-component regulatory system?

A

S. aureus and S. pyogenes

47
Q

How do we diagnose for pertussis?

A

take a swab that has penicillin on it &raquo_space; let bacteria grow on special media &raquo_space; identification is done via antibody assay or PCR

48
Q

What is the name for the media used to culture B. pertussis?

A

Bordet-Gengou media

49
Q

What is required prior to diagnosing a patient for pertussis? Why?

A

patient needs to be suspected to have the infection because diagnosis process is not easy

50
Q

Why must we add penicillin onto the swab prior to sampling a patient’s throat?

A

to kill the other bacteria present in the respiratory system

51
Q

What is a mode of treatment against pertussis?

A

antibiotics: erythromycin and chloramphenicol (= ErythChlor)

52
Q

What is used in efforts to prevent pertussis?

A

vaccines

53
Q

What vaccines are available against pertussis?

A

DPT (diphteria, pertussis, and tetanus) and DT(alpha)P

54
Q

What is the difference between DPT and DT(alpha)P?

A

DT(alpha)P contains inactive components of pertussis toxin and FHA (filamentous hemagglutination adhesin)

55
Q

What are the general characteristics of Legionella pneumophila?

A

Gram– rods that don’t stain well, doesn’t grow on general bacterial media, facultative (optional) intracellular pathogen, motile = has flagella; LPS is less toxic compared to other bacteria

56
Q

What is the reservoir for Legionella pneumophila?

A

aquatic and soil habitats

57
Q

What toxins do Legionella pneumophila produce?

A

none have yet been identified

58
Q

Where does Legionella pneumophila multiply?

A

inside free-living amoebas, macrophages and other protozoa

59
Q

What type of secretion system does the Legionella pneumophila have?

A

Type IV (TYPE 4!)

60
Q

What diseases does Legionella pneumophila cause?

A

Legionnaire’s disease and Pontiac fever

61
Q

Is Legionnaire’s disease a new or old disease?

A

new

62
Q

What does it mean when a disease is a “new” disease?

A

the bacteria did not originally cause a disease but something provided the bacterium the opportunity to cause a disease

63
Q

What is Legionnaire’s disease?

A

a severe toxic pneumonia, infection in the lower respiratory system

64
Q

What is Pontiac fever?

A

milder self-limiting disease infecting the upper respiratory tract; not life-threatening

65
Q

How many cases/year of Legionnaire’s disease are there in the US?

A

25,000/year

66
Q

Where was the first outbreak of Legionnaire’s disease?

A

1976 Philidelphia at American Legion Convention

67
Q

What is the mode of transmission of Legionella pneumophila?

A

environmental source = gets into the water that is used in humidifiers and cooling systems &raquo_space; distributed via airborne route (infectious aerosols) | no person-person transmission detected

68
Q

How does Legionella pneumophila survive the water treatment (chlorination) and filtration system?

A

they form biofilms

69
Q

What are the early symptoms of Legionnaire’s disease?

A

flu-like = difficult to diagnose patient for Legionnaire’s disease

70
Q

What are the late/2nd stage symptoms of Legionnaire’s disease?

A

fever, cough, dyspnea, possible CP (chest pain) and/or secretory diarrhea

71
Q

Where does the Type IV secretion system evolve from?

A

pilus

72
Q

Where in the body does Legionella pneumophila survive in?

A

survives in macrophages

73
Q

Where does the Type III secretion system evolve from?

A

flagella

74
Q

Why does Legionella pneumophila use the Type IV secretion system? What is the benefit of this for the bacteria?

A

to prevent phagolysosomal fusion at the early stage of entry so bacteria is not destroyed and can multiply

75
Q

Does Legionella pneumophila invade?

A

not cells but invades only macrophages

76
Q

What is the problem in diagnosing for the presence of Legionella pneumophila?

A

not very sensitive and only 50% effective

77
Q

What are the 2 specimens collected from the patient to perform a diagnostic test?

A

sputum and urine

78
Q

What diagnostic test does not require specimen collection and how does it detect presence of Legionella pneumophila?

A

chest x-ray determines lung damage due to pathogen

79
Q

How can the sputum sample be used to detect presence of Legionella pneumophila? How sensitive is this method?

A

use sputum by direct fluorescent antibody staining (DFA); only 50% sensitive

80
Q

How can the urine sample be used to detect presence of Legionella pneumophila?

A

use urine to detect Legionella pneumophila sergroup 1 via ELISA

81
Q

Why is culturing Legionella pneumophila not an effective diagnosis?

A

incubation takes 3-5 days

82
Q

What is the media used to culture Legionella pneumophila?

A

charcoal yeast extract agar

83
Q

What vaccines are available against Legionella pneumophila?

A

none at the moment

84
Q

What antibiotics are available to treat Legionnaire’s disease?

A

azithromycin, fluoroquinolone, erythromycin = (Az-Fl-Er)

85
Q

Which antibiotics are not recommended for use against Legionella pneumophila and why?

A

betalactam antibiotics because most Legionella strains produce beta-lactamases = very resistant to beta-lactam antibiotics

86
Q

What are 3 prevention methods against Legionella?

A

check water systems regularly for Legionella | improve methods for decontaminating water systems | use sterile water

Medical Microbiology (20 decks)

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