Infectious Dz Flashcards by Olivia Rice

Basis of skin’s resistance to infx (2):

physicochemical barriers

innate immunity

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Risk factors/ initiating events for SSTIs (2) (→ ↓ ID50 by ≥ 100x)

breaks in the skin

foreign bodies lodged in the skin

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Cytokine profile for acute inflammation:

TNFα
IL-1
IL-6
IL-8

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Cytokine profile for chronic inflammation:

INFƔ
IL-2
IL-4
IL-5

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Hallmark of acute inflammation:

pus (= PMNs)

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Hallmark of chronic inflammation:

granulomas (nodular collections of epithelioid m∅s and giant cells)

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Which type of microbes cause acute inflammation?

extracellular bacteria

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Which type of microbes cause chronic inflammation?

intracellular bacteria

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Most SSTIs (esp. community acquired) are caused by which 2 microbes?

Staph Aureus
Strep pyogenes (GAS)

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Special circumstances when the spectrum of causative microbes responsible for SSTIs is broader (3):

puncture wounds
penetrating
trauma
bites

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Special pt. pops. when the spectrum of causative microbes responsible for SSTIs is broader (6):

young people
old people
underlying skin dz
Diabetics
Pts. in HC facilities
Immunocomprimised

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Principles of Rx for SSTIs (3):

local hygienic care
Incision &amp; Drainage (I&amp;D)
Abx coverage for organisms only if:
 systemic ssx are present on PE 
 in special circumstances (e.g. puncture)
 in special pt. pops.

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Most SSTIs present acutely/chronically

acutely → rubor, calor, tumor, dolor

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Key components of innate immunity (5):

AMPS
cytokines
dentritic cells
PMNs
complement

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Signaling molecules that are an important component of the skin in preventing S. aureus and C. albicans infx (4):

IL-17
IL17R
STAT1
STAT3

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Name that microbe:
clinical pres:
rapidly spreading rash, cellulitis lymphangiitis, or adenopathy

S. pyogenes

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Name that microbe:
clinical pres.:
abscess formation
organ involvement may include: skin, blood, heart and bone

S. aureus

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Name that microbe:
gram(+) coccus in chains
catalase(-)
β-hemolytic
Bacitracin sensitive

S. pyogenes

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Name that microbe:
gram(+) coccus in clusters
coagulase (+)
catalase(+)

S. aureus

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Abx of choice for S. pyogenes

penicillin

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Post-streptococcal complications

acute rheumatic fever

post-strep. glomerulonephritis

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Exotoxin superAg that contribute to TSS and rash of scarlet fever (S. pyogenes) (2)

Pyrogenic exotoxin A

Pyrogenic exotoxin C

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Exotoxin involved in staphylococcal scalded skin syndrome (SSS)

Exfoliative toxin

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Bacteriophage encoded exotoxin found in methicillin resistant S. aureus strains

Panton-Valentine Leukocidin (PVL)

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SuperAg exotoxin involved in staph mediated TSS

TSST-1

You suspect this microbe in a pt. presenting w/ lymphedema or disrupted lymphatics

S. pyogenes

Normal flora can potentially cause an SSTI in which setting?

indwelling percutaneous catheters

Anatomic determination of the upper urinary tract:

above the uretero-pelvic junction

Anatomic determination of the lower urinary tract:

the bladder and below

A women w/ (+) hx of dysuria and frequency w/o vaginal irritation or discharge has > ___% probability of a UTI.

> 90%

If a women w/ (+) hx of dysuria and frequency w/o vaginal irritation or discharge presents to your clinic, is further diagnostic testing indicated?

NO!! | Even if tests are negative the probability of a UTI is still sufficiently high to indicate tx

MC microbe that causes a UTI

Uropathogenic E. Coli (UPEC)

Rx of choice in uncomplicated UTI

TMP sulfa or Nitrofurantoin

Characteristics of uncomplicated UTI (5):

``` comprise majority of UTIs occur in women microbe = UPEC ascending route of infx readily treatable ```

Characteristics of complicated UTI (5)

``` systemic findings (VS) occur in males or Diabetics may be caused by atypical organisms obstruction, instrumentation, and in-patient setting are common causes/RFs imaging is indicated ```

3 lab studies that may be used to help dx a UTI

Urinalysis Culture and Abx sensitivity testing Imaging studies

2 dipstick urinalysis tests used to dx a UTI

esterase: (+) → presence of PMNs nitrite: (+) → presence of bacteria

ssx that ↑ likelihood of UTI dx (4):

dysuria frequency CVA tenderness hematuria

ssx (or lack thereof) that ↓ likelihood of UTI dx (4):

absence of dysuria absence of back pain presence of vaginal irritation presence of vaginal discharge

Scenarios when culture and Abx sensitivity testing is indicated for a UTI (3):

recurrent infx lack of response to Rx complicated UTI

Scenarios when imaging studies are indicated for a UTI (3):

in males certain complicated UTIs when complications occur

DDX for dysuria ± frequency (4)

UTI STI (esp. in young adults) kidney stones chemical irritants

RFs for UTIs in males (3):

insertive anal intercourse female partner w/ active UTI non-circumcised

Abx w/ good prostate penetration (can use for male UTI tx) (2):

TMP-SMX | quinolones

mechanism of UTI in pt. w/ prostate dz

urinary retention/ stasis → bacteria able to multiply in residual urine and adhere to bladder to cause infx

U/A culture (+) for S. aureus in eval for UTI always means:

blood stream infx (e.g. endocarditis) → seeding of kidney and spill over into urine NEED TO FIND SOURCE OF SEEDING!!

Urease (+) microbe that can cause UTIs

proteus mirabilis

alkaline urine (↑ pH) should make you think about which organism in an eval for a UTI?

proteus! → urease (+)

DDx of dysuria in men (4):

urethritis prostatitis epididymitis UTI

GC and C. trachomatis are the MC pathogens for which STD syndromes in men and/or women(4)?

urethritis cervicitis epididymitis PID

3 characteristics of dysuria in urethritis seen in males:

may be most marked first thing in the AM (d/t ↑ acidity or solute content) May ↑ w/ EtOH consumption B/w micturitions may be perceived as pain, itching, frequency, urgency

MC ssx seen in male urethritis (2):

purulent/ mucopurulent urethral discharge (clear or cloudy) | often accompanied by dysuria

Specific ssx in hx during eval for a male w/ dysuria that suggest a different dx than urethritis (3):

discomfort only during ejaculation deep pelvic pain radiation of pain to back

Before you can perform a PE on a male suspected of urethritis, what must you instruct him to do?

Do NOT urinate for ≥ 2 hrs before exam

Incubation period of GC urethritis seen in males:

3-10 days

Discharge present at the urethral meatus w/o stripping stongly suggests what?

GC urethritis

If a man has sex w/ a chick that has GC, will he definitely become infected as well?

NO! | risk of infx w/ GC following a single episode of intercourse w/ an infected partner = 17%

(+) "sock sign" (so much discharge from penis, man has to put a sock on it to prevent staining)

GC Urethritis

Incubation period seen in non-GC urethritis

2-35 days (50% develop ssx w/in 4 days)

MC local complication of gonorrhea in males: | What is it usually assoc. with?

Epididymitis→ usually assoc. w/ overt or subclinical urethritis

MC offending microbe causing urethritis in older men w/o high-risk sexual activity? What 1º ssx can be misleading if present?

Gram (-) bacteria that cause UTIs; | Sometimes urethral ssx are absent and epididymal pain is the primary ssx

Epididymitis ssx (2):

unilateral testicular pain | unilateral testicular swelling

Findings on gram stain if urethral discharge consistent w/ urethritis

> 2 WBCs/ hpf

Typical urinalysis w/ microscopy of first-void urine seen in urethritis in a male

(+) leukocyte esterase | > 10 WBC/ hpf

lab test done for ID of C. trachomatis and N. gonorrhoeae

PCR

When evaluating a pt. w/ a suspected STI, which pathogens should you screen for?

``` GC Chlamydia Syphilis HIV (NOT HSV typically→ only if they have a painful ulcer) ```

If a dx of GC urethritis is made, what other pathogen should you tx empirically for?

Chlamydia; | co-infx not uncommon

Tx for N. gonorrhoeae

IV 3rd gen. cephalosporin

Tx for Chlamydia (2):

Doxycycline (tetracycline) or | azithromycin (macrolide)

An ulcer present on a sexually active man's urethral meatus points to which pathogen?

HSV

Possible pathogens responsible for urethritis in males (5):

``` GC (lots of purulent discharge) Chlamydia (clear discharge present only after stripping urethra) HSV (+ulcer) Trichomonas vaginalis (non-purulent) Mycoplasma genitalium (doxycycline has poor efficacy) ```

Possible pathogens that can cause cervicitis (3):

GC Chlamydia HSV

Which 3 pt. populations should be screened for chlamydia and gonorrhea?

sexually active women

Consequence of missing ongoing GC or Chlamydia infx in women

PID → severe infx and/or infertility

"Gold Standard" for HSV encephalitis dx

HSV PCR on CSF

Infectious Dz Flashcards

(75 cards)