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USMLE STEP 2 and 3 > Internal Medicine_Infectious Diseases_10 > Flashcards

Internal Medicine_Infectious Diseases_10 Flashcards

Bacteria_Neisseria, Moraxella, Haemophilus, Acinetobacter baumannii

1
Q

What are the common clinical syndromes caused by Neisseria meningitidis?

A

Meningitis and meningococcemia (septicemia). High-risk presentations include purpura fulminans and Waterhouse-Friderichsen syndrome.

The classic triad of meningitis includes:
fever, neck stiffness, and altered mental status.

Look for petechial rash in meningococcemia.

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2
Q

What complement deficiency increases the risk of meningitis due to infection with Neisseria?

A

Terminal complement factors
(C5 to C9)

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3
Q

What type of bacteria is Neisseria?

A

gram-negative diplococci

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4
Q

Metabolically, what differentiates Neisseria gonorrhoeae and meningitiidis?

A

Neisseria gonorrhoeae can metabolize glucose.

Neisseria meningitidis is capable of metabolizing glucose and maltose.

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5
Q

What enzyme is present in both Neisseria gonorrhoeae and meningitiidis?

A

oxidase.

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6
Q

What agar is used for Neisseria?

A

chocolate agar and Thayer-Martin agar, which contains vancomycin, polymyxin, nystatin, and trimethoprim.

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7
Q

What key virulence factor exists with Neisseria?

A

Pili

Promotes nasopharyngeal colonization.

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8
Q

What enables Neisseria to colonize mucosal surfaces more easily that aids in mucosal ahderence.

A

IgA protease.

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9
Q

What highly-inflammatory compound is possessed by Neisseria that is similar to endotoxins?

A

lipooligosaccharides (LOS) —> allows for blebbing

OPA (opacity proteins)

Found on Neisseria’s outer surfaces, which help form tight bonds with each other and host cells.

These pro-inflammatory agents lead to DIC (capillary leakage, fluid extravasation, hypovolemia, thrombocytopenia, and thrombosis).

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10
Q

How is Neisseria meningitiidis spread?

A

****respiratory droplets

**Use a face mask in the hospital setting for PPE. **

Places that commonly experience outbreaks are college dormitories and military barracks.

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11
Q

What key virulence factor exists with Neisseria that prevents phagocytosis?

A

capsule.

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12
Q

What endocrine organ is commonly implicated with Neisseria meningitiidis?

A

Adrenal glands

Adrenal involvement in meningococcemia can lead to a syndrome of adrenal insufficiency known as Waterhouse-Friderichsen syndrome.

Adrenal insufficiency → metabolic derangements → hypoglycemia, hyponatremia, HYPERkalemia.

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13
Q

What sequelae is commonly seen with an infection with Neisseria meningitiidis?

A

Sequelae of Neisseria meningitidis infection include immune-complex mediated complications (e.g., pericarditis, arthritis).

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14
Q

What prodrome is seen with Neisseria meningitiidis?

A

Febrile, flu-like illness with myalgias.

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15
Q

What can Neisseria meningitiidis mimic?

A

Neisseria meningitidis infection can resemble strep throat by manifesting as pharyngitis.

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16
Q

What skin symptom suggests DIC secondary to Neisseria meningitiidis?

A

Neisseria meningitidis infection can manifest as a petechial rash due to DIC.

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17
Q

Neisseria meningitidis is the _____ most common cause of bacterial meningitis.

A

2nd.

Streptococcus pneumoniae is usually the most common in patients older than 1 month and in neonates, Group B Streptococcus (Streptococcus agalactiae) is the most common cause.

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18
Q

What is an effective antibiotic against Neisseria meningitidis?

A

Ceftriaxone

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19
Q

What antibiotic is used for Neisseria meningitidis in penicillin and beta-lactam allergic patients?

A

Chloramphenicol

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20
Q

What antibiotics are used for post-exposure prophylaxis against Neisseria meningitidis?

A

Rifampin, ciprofloxacin, or ceftriaxone.

Ideally given within 24 hours of exposure.

Children can be given ceftriaxone or Rifampin.

Adults can receive rifampin (600 mg twice daily for two days), ciprofloxacin (single oral 500 mg dose), or ceftriaxone (single IM dose). Ciprofloxacin is not recommended for children or pregnant women due to risks of cartilage toxicity.

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21
Q

What antibiotics should be used for post-exposure prophylaxis against Neisseria meningitidis in children?

A

Drug of Choice for children:
Rifampin alternative is ceftriaxone).

Dose for older children:
10 mg/kg twice daily for two days.

Dose for infants:
5 mg/kg for infants <1 month.

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22
Q

What antibiotics should be used for post-exposure prophylaxis against Neisseria meningitidis in pregnancy?

A

Pregnant patients should be given ceftriaxone.

Azithromycin: A secondary option if ceftriaxone is contraindicated.

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23
Q

what are the common medications that increase susceptibility of getting meningitis by Neisseria?

A

Eculizumab (Soliris): Inhibits C5, blocking MAC formation; used in PNH and aHUS.

Ravulizumab: Similar mechanism to eculizumab but with longer duration of action.

Corticosteroids: High doses can transiently impair complement function.

Immunosuppressive Drugs: Rituximab, mycophenolate mofetil, and cyclophosphamide may indirectly impair complement activity.

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24
Q

What are the countermeasures for preventing Neisseria meningitidis when taking immunpsuppressing medications?

A

Vaccination: Meningococcal vaccines (MenACWY and MenB) prior to starting therapy.

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25
Q

How is the vaccination for Neisseria formulated?

A

A vaccine with capsular polysaccharides of four serotypes of meningococcus with capsular antigens linked to a carrier protein (e.g., diphtheria toxoid).

By conjugating the bacterial polysaccharides to a protein carrier, it elicits a robust T-cell-dependent response, leading to longer-lasting immunity. Conjugate vaccines also reduce nasopharyngeal carriage, contributing to herd immunity.

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26
Q

What serogroups does the meningococcal conjugate vaccine (MenACWY) protect against?

A

Serogroups A, C, W, and Y.

Administer at age 11-12 years, with a booster at 16 years. It is mandatory for military recruits and travelers to the meningitis belt of sub-Saharan Africa.

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27
Q

Who should receive the MenB vaccine?

A

Adolescents aged 16-18 years (clinical discretion) and high-risk groups (e.g., during outbreaks, individuals with complement deficiencies, or asplenia).

Serogroup B is responsible for outbreaks in developed countries, especially in close-living settings like dormitories.

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28
Q

What is a mnemonic to remember the Neisseria meningitidis vaccine schedule?

A

“11-16-Boost”:

11 years: First MenACWY dose.
16 years: Booster dose.
Boost every 5 years if high-risk.
29
Q

Who requires booster doses of the MenACWY vaccine?

A

Individuals at persistent high risk (e.g., asplenia, complement deficiencies, microbiologists exposed to N. meningitidis). Boosters are given every 5 years.

College freshmen living in dormitories are at increased risk and may also need vaccination.

30
Q

What vaccination is recommended for travelers to sub-Saharan Africa?

A

MenACWY vaccine, as serogroup A outbreaks are common in the meningitis belt. The vaccine is required for Hajj and Umrah pilgrims in Saudi Arabia.

31
Q

What is the public health strategy for managing meningococcal outbreaks?

A

Targeted vaccination campaigns with MenACWY or MenB vaccines based on the serogroup causing the outbreak.

Prophylactic antibiotics (e.g., rifampin, ciprofloxacin) are also used for close contacts of infected individuals.

32
Q

What are the contraindications for meningococcal vaccines?

A

Severe allergic reaction (e.g., anaphylaxis) to a prior dose or vaccine component. Minor illnesses (e.g., cold) are not contraindications; vaccination should proceed in these cases.

33
Q

What is the gram staining and morphology of Neisseria gonorrhoeae?

A

Gram-negative diplococci.

34
Q

What type of intracellular presence does Neisseria gonorrhoeae exhibit?

A

Facultative intracellular within polymorphonuclear cells (PMNs).

35
Q

Is Neisseria gonorrhoeae encapsulated?

A

No, Neisseria gonorrhoeae is not encapsulated.

36
Q

How is Neisseria gonorrhoeae transmitted?

A

Sexually transmitted infection (STI).

37
Q

What is the significance of asymptomatic carriers in Neisseria gonorrhoeae infection?

A

They can transmit the infection without showing symptoms.

38
Q

How can Neisseria gonorrhoeae affect newborns?

A

It can be transmitted during birth, causing neonatal eye infections
(ophthalmia neonatorum).

39
Q

What are common manifestations of Neisseria gonorrhoeae in men?

A

Urethritis, prostatitis, and epididymitis.

40
Q

What are common manifestations of Neisseria gonorrhoeae in women?

A

Cervicitis, pelvic inflammatory disease (PID), and salpingitis.

Intermenstrual bleeding, such as post-coital spotting, is an alarming symptom of gonococcal cervicitis

41
Q

What is the name of the syndrome associated with liver capsule inflammation due to Neisseria gonorrhoeae?

A

Fitz-Hugh-Curtis syndrome.

42
Q

What are symptoms of disseminated gonococcal infection?

A

Purulent arthritis, tenosynovitis, and dermatitis.

43
Q

What diagnostic test is preferred for Neisseria gonorrhoeae?

A

Nucleic acid amplification testing (NAAT).

44
Q

What is the drug of choice for treating Neisseria gonorrhoeae?

A

Ceftriaxone.

45
Q

Why is doxycycline or a macrolide added to Neisseria gonorrhoeae treatment?

A

To cover potential Chlamydia co-infection.

If Chlamydia is negative following lab results, only treat Neisseria.

46
Q

What preventive method is emphasized for Neisseria gonorrhoeae?

A

Consistent condom use.

47
Q

What area is commonly implicated by isseminated gonococcal infection?

A

Achilles tendon.

48
Q

What is the morphology and Gram-staining of Moraxella catarrhalis?

A

Moraxella catarrhalis is a Gram-negative diplococcus.

49
Q

Where does Moraxella catarrhalis commonly colonize?

A

M. catarrhalis commonly colonizes the nasopharynx.

50
Q

What test results are characteristic of Moraxella catarrhalis?

A

M. catarrhalis is an aerobic bacteria that is catalase-positive, oxidase-positive, and forms biofilms.

The “hockey puck sign” refers to the smooth sliding of colonies across agar when nudged with a loop.

51
Q

What enzyme does Moraxella catarrhalis produce that enhances antibiotic resistance?

A

M. catarrhalis produces beta-lactamase, which breaks down beta-lactam antibiotics.

52
Q

What are common infections caused by Moraxella catarrhalis?

A

Otitis media (especially in children)

Bacterial sinusitis

COPD exacerbations (bronchopneumonia in adults)

53
Q

What are the treatments of choice for Moraxella catarrhalis infections?

A

Cephalosporins
Amoxicillin-clavulanate
Trimethoprim-sulfamethoxazole (TMP-SMX)
Fluoroquinolones

54
Q

Which 2 bacteria are the most common causes of pelvic inflammatory disease (PID)?

A

Chlamydia trachomatis (subacute; often undiagnosed)

Neisseria gonorrhoeae (acute)

55
Q

If gonorrhea/chlamydia is suspected, then treat _________ .

A

empirically

56
Q

Standard STI screening panel for common infections in both men & women includes:

A

Neisseria gonorrhea

Chlamydia trachomatis

HIV

Treponema pallidum

57
Q

What is the outpatient treatment regimen for pelvic inflammatory disease (PID)?

A

IM ceftriaxone (or other cephalosporin)

Oral doxycycline

Oral metronidazole

58
Q

What type of bacteria is Haemophilus influenzae?

A

Haemophilus influenzae is a gram-negative coccobacillus.

59
Q

What are the growth requirements for Haemophilus influenzae?

A

It requires chocolate agar enriched with factor V (NAD) and factor X (hemin).

60
Q

How is Haemophilus influenzae transmitted?

A

It is transmitted via respiratory droplets (aerosol transmission).

61
Q

What diseases are caused by Haemophilus influenzae?

A

Diseases caused by the encapsulated (type B) Haemophilus influenzae bacteria are epiglottitis, otitis media, pneumonia, septic arthritis, and meningitis.

Common symptoms of meningitis caused by Haemophilus influenzae include headache, neck stiffness, photophobia, nausea, and vomiting.

Nontypable Haemophilus influenzae illnesses are usually respiratory infections (otitis, pneumonia, and sinusitis).

62
Q

What are the characteristic symptoms of epiglotitis caused by Haemophilus influenzae?

A

Symptoms include rapidly progressive high fever, toxic appearance, dysphagia, dysphonia, drooling, and a cherry red epiglottis.

These patients tend to position themselves in a sniffing or tripod position.

These patients tend to have stridor (high-pitch on inspiration).

63
Q

Is Haemophilus influenzae the most common cause of epiglotitis or otitis media?

A

No, infection of the ear canal (otitis media) or the aryepiglottic area (epiglotitis) is most commonly secondary to Streptococcus pneumoniae due to increased vaccination compliance against Haemophilus influenzae type b.

Children who get epiglotitis secondary to Haemophilus influenzae infection are likely unvaccinated and might have other missing vaccines.

The most common causes of epiglotitis and otitis media is pneumococcus. The other causes are from Staphylococcus aureus and Group A Streptococcus.

64
Q

How is epiglotitis managed?

A

Manage airway and intubate (endotracheal intubation) if needed.

Antibiotics:
Augmentin (Amox-Clav) –> covers Haemophilus influenzae
Vancomycin or Ceftriaxone –> covers most other bacteria (including Haemophilus influenzae)

65
Q

What prophylactic treatment is recommended for close contacts of patients diagnosed with What prophylaxis is recommended for close contacts of Haemophilus influenzae type b infections (epiglottitis, otitis media, or meningitis, secondary to Haemophilus influenzae type b)?

A

Rifampin prophylaxis.

66
Q

Acinetobacter baumannii most commonly affects … ?

A

hospitalized patients

patients usually develop pneumonia or bacteremia

67
Q

Why is Acinetobacter baumannii hard to treat?

A

often this bacteria multidrug resistant

68
Q

How is Acinetobacter baumannii treated?

A

carbapenem

polymyxin

cefepime

USMLE STEP 2 and 3 (139 decks)

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