Ch2

Question 1

What organism causes human plague and how is it transmitted?

Answer 1

Yersinia pestis, transmitted by flea bites from rats and rodents; pneumonic plague spreads via droplets from person to person.

Question 2

What are the three types of plague caused by Y. pestis?

Answer 2

Bubonic, pneumonic, and septicemic plague.

Question 3

What is the preferred diagnostic method for Y. pestis?

Answer 3

Polymerase chain reaction (PCR), due to handling hazards of cultures.

Question 4

What antibiotics are commonly used for treating plague?

Answer 4

Aminoglycosides and chloramphenicol.

Question 5

What are the key virulence factors of Y. pestis?

Answer 5

Type III Secretion System (YopH, YopE, YopJ/P), F1 gene, Pla gene, endotoxins, exotoxins, serum resistance, and iron absorption mechanisms.

Question 6

What are the clinical signs of bubonic plague?

Answer 6

Fever, painful bubo, bacteremia, and potentially death. Incubation ≤7 days.

Question 7

What characterizes pneumonic plague?

Answer 7

Rapid pulmonary infection, high mortality, hemoptysis, chest pain, dyspnea. Incubation 2–3 days.

Question 8

What other diseases can Y. pestis cause?

Answer 8

Plague meningitis, tonsillar/pharyngeal plague, and plague carbuncle.

Question 9

How is Y. pestis diagnosed?

Answer 9

Clinical suspicion, serology or immunofluorescence, and ‘safety pin’ staining (Wright/Wayson).

Question 10

How is Y. pestis prevented?

Answer 10

Animal control, avoid sick/dead animals, military vaccine available.

Question 11

Historical pandemics of Y. pestis?

Answer 11

1st: 541–750 AD, 2nd: 1320s (Black Death), 3rd: 1860s from China.

Question 12

What does Y. enterocolitica typically cause?

Answer 12

Enterocolitis with diarrhea, fever, abdominal pain.

Question 13

What serious syndrome mimics appendicitis in children?

Answer 13

Pseudoappendicitis (mesenteric lymphadenitis) from Y. enterocolitica.

Question 14

What condition is linked to transfusion-related Y. enterocolitica?

Answer 14

Grows at 4°C in stored blood → bacteremia and endotoxic shock.

Question 15

What does Y. pseudotuberculosis cause in humans?

Answer 15

Gastrointestinal infection; can lead to septicemia, arthritis, abscesses, hepatitis, and osteomyelitis.

Question 16

How is Y. pseudotuberculosis transmitted?

Answer 16

Through contaminated food and water.

Question 17

Who is more at risk of Y. pseudotuberculosis complications?

Answer 17

Immunocompromised patients, or those with haemochromatosis or liver cirrhosis.

Question 18

What are the characteristics of Pasteurella?

Answer 18

Small, facultative anaerobic coccobacilli with hyaluronic acid capsule.

Question 19

Common Pasteurella species infecting humans?

Answer 19

P. multocida (most common), P. canis (dog bites).

Question 20

Main transmission mode of Pasteurella?

Answer 20

Animal bites, scratches, and shared food.

Question 21

What clinical conditions does Pasteurella cause?

Answer 21

Localized cellulitis, chronic respiratory disease exacerbation, systemic infections.

Question 22

What are the lab culture features of Pasteurella?

Answer 22

Grows on blood and chocolate agar, poor on MacConkey, buttery colonies with musty odor.

Question 23

What is the antibiotic of choice for Pasteurella?

Answer 23

Penicillin.

Question 24

Alternatives to penicillin for Pasteurella?

Answer 24

Cephalosporins, macrolides, tetracyclines, fluoroquinolones.

Question 25

Which antibiotics show poor activity against Pasteurella?

Answer 25

Semisynthetic penicillins, 1st-gen cephalosporins, aminoglycosides.

Question 26

What is Francisella tularensis and what disease does it cause?

Answer 26

A highly infectious gram-negative coccobacillus causing tularemia.

Question 27

What are the subspecies of F. tularensis?

Answer 27

Type A: F. tularensis subsp. tularensis (high virulence), Type B: F. tularensis subsp. holarctica, F. mediaasiatica.

Question 28

Transmission routes of F. tularensis?

Answer 28

Ticks, deerflies, infected animals, inhalation, and ingestion.

Question 29

What are the pathogenesis features of F. tularensis?

Answer 29

Inhibits phagosome-lysosome fusion, replicates in cytosol, capsule resists complement, weak endotoxin.

Question 30

What are the clinical types of tularemia?

Answer 30

Ulceroglandular, oculoglandular, glandular, typhoidal, pneumonic, oropharyngeal, and gastrointestinal.

Question 31

How is tularemia diagnosed?

Answer 31

Culture (chocolate or BCYE), serology (≥1:160 titer), PCR/NAATs.

Question 32

What is the treatment for tularemia?

Answer 32

First-line: Gentamicin; Alternatives: Doxycycline, ciprofloxacin; Beta-lactams are ineffective.

Question 33

How is tularemia prevented?

Answer 33

Avoid wild animals, insect repellent, BSL-3 precautions; no vaccine currently available.

Question 34

Where are non-sporing anaerobes found in the body?

Answer 34

On mucosal surfaces as normal flora.

Question 35

What diseases do anaerobic Gram-negative rods cause?

Answer 35

Wound infections, periodontal disease, abscesses, endogenous infections.

Question 36

What are common anaerobic pathogens?

Answer 36

Bacteroides fragilis, Fusobacterium nucleatum, Porphyromonas, Prevotella.

Question 37

Key virulence factors of Bacteroides?

Answer 37

Capsule, fimbriae, weak endotoxin, oxygen tolerance, proteases, SCFAs.

Question 38

What infections are caused by anaerobic Gram-negatives?

Answer 38

Respiratory, brain abscess, intraabdominal, gynecologic, skin/soft tissue, bacteremia, gastroenteritis.

Question 39

How are these organisms diagnosed?

Answer 39

Gram stain, anaerobic culture, mass spectrometry, 16S rRNA.

Question 40

What antibiotics are effective against anaerobic Gram-negatives?

Answer 40

Metronidazole, carbapenems, β-lactam–β-lactamase inhibitors; avoid clindamycin and β-lactams.