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USMLE 1 > Microbiology- Systems > Flashcards

Microbiology- Systems Flashcards

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1
Q

Normal flora: dominant

Skin 
Nose 
Oropharynx 
Dental plaque 
Colon 
Vagina
A

S epidermidis

S epidermidis; colonized by S aureus

Viridans group streptococci

S mutans

B fragilis > E coli

Lactobacillus; colonized by E coli and group B strep

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2
Q

Bugs causing foodborne illness

A 
B cereus
C botulinum
C perfringens
E coli O157:H7
L monocytogenes
Salmonella 
S aureus
V parahaemolyticus and V vulnificus
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3
Q

Bloody diarrhea

A 
Campylobacter
E histolytica
Enterohemorrhagic Ecoli
Enteroinvasive E coli
Salmonella (nontyphoidal)
Shigella
Y enterocolitica
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4
Q

Watery diarrhea

A 
C difficile
C perfringens
Enterotoxigenic E coli
Protozoa
V cholerae 
Viruses (Rotavirus, norovirus, enteric adenovirus)
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5
Q

Common causes of pneumonia

Children (4 weeks - 18 years)

A

“Runts May Cough Chunky Sputum”

Viruses (RSV)
Mycoplasma
C trachomatis (infants–3 yr)
C pneumoniae (school-aged children)
S pneumoniae
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6
Q

Common causes of pneumonia

Adults (18 - 40 years)

A

Mycoplasma
C pneumoniae
S pneumoniae
Viruses (eg, influenza)

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7
Q

Common causes of pneumonia

Adults (18 - 40 years)

A

Mycoplasma
C pneumoniae
S pneumoniae
Viruses (eg, influenza)

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8
Q

Common causes of pneumonia

Adults (40 - 60 years)

A 
S pneumoniae
H influenzae
Anaerobes
Viruses
Mycoplasma
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9
Q

Common causes of pneumonia

Adults (more than 60 years)

A 
S pneumoniae
Influenza virus
Anaerobes
H influenzae
Gram ⊝ rods
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10
Q

Common causes of pneumonia (Special groups)

Alcoholic

A

Klebsiella, anaerobes usually due to aspiration (eg, Peptostreptococcus, Fusobacterium, Prevotella,
Bacteroides)

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11
Q

Common causes of pneumonia (Special groups)

  • IV drug users
  • Aspiration
A
  • S pneumoniae, S aureus

- Anaerobes

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12
Q

Common causes of pneumonia (Special groups)

Atypical

A

Mycoplasma, Chlamydophila, Legionella, viruses (RSV, CMV, influenza, adenovirus)

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13
Q

Common causes of pneumonia (Special groups)

Cystic fibrosis

A

Pseudomonas, S aureus, S pneumoniae, Burkholderia cepacia

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14
Q

Common causes of pneumonia (Special groups)

Immunocompromised

A

S aureus, enteric gram ⊝ rods, fungi, viruses, P jirovecii (with HIV).

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15
Q

Common causes of pneumonia (Special groups)

Nosocomial (hospital acquired)

A

S aureus, Pseudomonas, other enteric gram ⊝ rods

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16
Q

Common causes of pneumonia (Special groups)

Postviral

A

S pneumoniae, S aureus, H influenzae

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17
Q

Common causes of meningitis
- newborn (0- 6months)

  • Children (6months- 6 years)
  • 6-60 years
  • +60 years
A
  • Group B streptococci, E coli, Listeria
  • S pneumoniae, N meningitidis, H influenzae type b
    Enteroviruses
  • S pneumoniae, N meningitidis (#1 in teens), Enteroviruses, HSV

S pneumoniae, Gram ⊝ rods, Listeria

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18
Q

Viral causes of meningitis:

A

enteroviruses (especially coxsackievirus), HSV-2 (HSV-1 = encephalitis), HIV, West Nile virus (also causes encephalitis), VZV.

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19
Q

Cerebrospinal fluid findings in meningitis: opening pressure, cells, protein, glucose

  • Bacterial
  • Fungal/TB
  • Virus
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A
  • high, PMNs, High, Low
  • High, Lymphocytes, High, Low
  • Normal/high, Lymphocytes, High/normal, Normal
20
Q

Infections causing

brain abscess

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A

Most commonly viridans streptococci and Staphylococcus aureus. If dental infection or extraction
precedes abscess, oral anaerobes commonly involved.

Multiple abscesses are usually from bacteremia; single lesions from contiguous sites: otitis media and mastoiditis Žtemporal lobe and cerebellum; sinusitis or dental infection Žfrontal lobe.

Toxoplasma reactivation in AIDS.

21
Q

Osteomyelitis, Risk factor:

  • Assume if no other information is available:
  • Sexually active:
  • Sickle cell disease:
  • Prosthetic joint replacement:
  • Vertebral involvement:
  • Cat and dog bites:
  • IV drug abuse:
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A
  • S aureus (most common overall)
  • Neisseria gonorrhoeae (rare), septic arthritis more common.
  • Salmonella and S aureus
  • S aureus and S epidermidis
  • S aureus, Mycobacterium tuberculosis (Pott disease)
  • Pasteurella multocida
  • S aureus; also Pseudomonas, Candida
22
Q

Osteomyelitis Diagnosis

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A

MRI is best for detecting acute infection and detailing anatomic involvement.

23
Q

Cystitis

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A

presents with dysuria, frequency, urgency, suprapubic pain, and WBCs (but not WBC casts) in urine. Primarily caused by ascension of microbes from urethra to bladder.

Ascension to kidney results in pyelonephritis, which presents with fever, chills, flank pain, costovertebral angle tenderness, hematuria, and WBC casts.

24
Q

Urinary tract infections Predisposing factors

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A

Obstruction, kidney surgery, catheterization, GU malformation, diabetes, pregnancy.

Males—infants with congenital defects, vesicoureteral reflux.
Elderly—enlarged prostate.

25
Urinary tract infections Diagnostic markers:
⊕ Leukocyte esterase = evidence of WBC activity. ⊕ Nitrite test = reduction of urinary nitrates by bacterial species (eg, E coli). ⊕ Urease test = urease-producing bugs (eg, S saprophyticus, Proteus, Klebsiella)
26
Urinary tract infections Agents
- Escherichia coli - Staphylococcus saprophyticus - Klebsiella pneumoniae (3rd leading cause of UTI) - Serratia marcescens (Some strains produce a red pigment) - Enterococcus - Proteus mirabilis ( causes “swarming” on agar; associated with struvite stones) - Pseudomonas aeruginosa (Blue-green pigment and fruity odor)
27
Common vaginal infections
Bacterial vaginosis: No inflammation. Thin, white discharge with fishy odor. Clue cells. Metronidazole or clyndamicin. Trichomonas vaginitis: Inflammation (“strawberry cervix”). Frothy, yellow-green, foulsmelling discharge. metronidazole (treat sexual partner) Candida vulvovaginitis: Inflammation. Thick, white, “cottage cheese” discharge. Pseudohyphae. Azoles
28
ToRCHeS infections
Transmission is transplacental in most cases, or via delivery (especially HSV-2). Nonspecific signs common to many ToRCHeS infections include hepatosplenomegaly, jaundice, thrombocytopenia, and growth retardation. Toxoplasma, Rubella, Cytomegalovirus, HIV, Herpes simplex virus-2, Syphilis
29
ToRCHeS infections: | Toxoplasma gondii
Classic triad: chorioretinitis, hydrocephalus, and intracranial calcifications, +/− “blueberry muffin” rash. *mother asymptomatic
30
ToRCHeS infections: | Rubella
Classic triad: abnormalities of eye (cataract) and ear (deafness) and congenital heart disease (PDA); ± “blueberry muffin” rash. *mother: Rash, lymphadenopathy, polyarthritis, polyarthralgia
31
ToRCHeS infections: | Cytomegalovirus
Hearing loss, seizures, petechial rash, “blueberry muffin” rash, chorioretinitis, periventricular calcifications *mother: Usually asymptomatic; mononucleosis-like illness
32
ToRCHeS infections: | HIV
Recurrent infections, chronic diarrhea
33
ToRCHeS infections: | Herpes simplex virus-2
Meningoencephalitis, herpetic (vesicular) lesions * mother: Usually asymptomatic; herpetic (vesicular) lesions
34
ToRCHeS infections: | Syphilis
Often results in stillbirth, hydrops fetalis; if child survives, presents with facial abnormalities (eg, notched teeth, saddle nose, short maxilla), saber shins, CN VIII deafness. *mother: Chancre (1°) and disseminated rash (2°)
35
Red rashes of childhood (pag 183)
Coxsackievirus type A: Hand-foot-mouth disease Human herpesvirus 6: Roseola (exanthem subitum) Measles virus: Measles (rubeola) Parvovirus B19: Erythema infectiosum (fifth disease) Rubella virus: Rubella Streptococcus pyogenes: Scarlet fever Varicella-Zoster virus: Chickenpox
36
Sexually transmitted infections Disease and Agent - AIDS - Chancroid - Chlamydia - Condylomata acuminata - Genital herpes
- Opportunistic infections, Kaposi sarcoma, lymphoma. HIV - Painful genital ulcer with exudate, inguinal adenopathy. Haemophilus ducreyi (it’s so painful, you “do cry”). - Urethritis, cervicitis, epididymitis, conjunctivitis, reactive arthritis, PID. Chlamydia trachomatis (D–K) - Genital warts, koilocytes. HPV-6 and -11 - Painful penile, vulvar, or cervical vesicles and ulcers; can cause systemic symptoms such as fever, headache, myalgia. HSV-2, less commonly HSV-1
37
Sexually transmitted infections Disease and Agent - Gonorrhea - Granuloma inguinale (Donovanosis) - Hepatitis B - Lymphogranuloma venereum
- Urethritis, cervicitis, PID, prostatitis, epididymitis, arthritis, creamy purulent discharge. Neisseria gonorrhoeae - Painless, beefy red ulcer that bleeds readily on contact. Klebsiella (Calymmatobacterium) granulomatis; cytoplasmic Donovan bodies (bipolar staining) seen on microscopy. - Jaundice. HBV - Infection of lymphatics; painless genital ulcers, painful lymphadenopathy (ie, buboes). C trachomatis (L1–L3)
38
Sexually transmitted infections Disease and Agent - Primary syphilis - Secondary syphilis - Tertiary syphilis - Trichomoniasis
- Painless chancre. Treponema pallidum - Fever, lymphadenopathy, skin rashes. condylomata lata - Gummas, tabes dorsalis, general paresis, aortitis, Argyll Robertson pupil - Vaginitis, strawberry cervix, motile in wet prep. Trichomonas vaginalis
39
Pelvic inflammatory disease
Top bugs—Chlamydia trachomatis (subacute, often undiagnosed), Neisseria gonorrhoeae (acute). Signs include cervical motion tenderness, adnexal tenderness, purulent cervical discharge. PID may include salpingitis, endometritis, hydrosalpinx, and tubo-ovarian abscess. Can lead to perihepatitis (Fitz-Hugh–Curtis syndrome)—infection and inflammation of liver capsule and “violin string” adhesions of peritoneum to liver.
40
Nosocomial infections Risk factors: - Antibiotic use - Aspiration (2° to altered mental status, old age) - Decubitus ulcers, surgical wounds, drains - Intravascular catheters
- Clostridium difficile. Watery diarrhea, leukocytosis - Polymicrobial, gram ⊝ bacteria, often anaerobes. Right lower lobe infiltrate or right upper/ middle lobe (patient recumbent); purulent malodorous sputum. - S aureus (including MRSA), gram ⊝ anaerobes(Bacteroides, Prevotella, Fusobacterium). Erythema, tenderness, induration, drainage from surgical wound sites. - S aureus (including MRSA), S epidermidis (long term) , Enterobacter. Erythema, induration, tenderness, drainage from access sites
41
Nosocomial infections Risk factors: - Mechanical ventilation, endotracheal, intubation - Renal dialysis unit, needlestick - Urinary catheterization - Water aerosols
- Late onset: P aeruginosa, Klebsiella, Acinetobacter, S aureus. New infiltrate on CXR,  sputum production; sweet odor (Pseudomonas). - HBV, HCV - Proteus spp, E coli, Klebsiella. Dysuria, leukocytosis, flank pain or costovertebral angle tenderness. - Legionella. Signs of pneumonia, GI symptoms (diarrhea, nausea, vomiting), neurologic abnormalities
42
Bugs affecting unvaccinated children: | Rash
Beginning at head and moving down with postauricular lymphadenopathy. Rubella virus Beginning at head and moving down; rash preceded by cough, coryza, conjunctivitis, and blue-white (Koplik) spots on buccal mucosa. Measles virus
43
Bugs affecting unvaccinated children: | Meningitis
Microbe colonizes nasopharynx. H influenzae type b Can also lead to myalgia and paralysis. Poliovirus
44
Bugs affecting unvaccinated children: | Respiratory
Epiglottitis. H influenzae type b Pharyngitis. Corynebacterium diphtheriae
45
Bugs hints
pag. 186

USMLE 1 (73 decks)

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