Infectious Dz Flashcards
Basis of skin’s resistance to infx (2):
physicochemical barriers
innate immunity
Risk factors/ initiating events for SSTIs (2) (→ ↓ ID50 by ≥ 100x)
breaks in the skin
foreign bodies lodged in the skin
Cytokine profile for acute inflammation:
TNFα
IL-1
IL-6
IL-8
Cytokine profile for chronic inflammation:
INFƔ
IL-2
IL-4
IL-5
Hallmark of acute inflammation:
pus (= PMNs)
Hallmark of chronic inflammation:
granulomas (nodular collections of epithelioid m∅s and giant cells)
Which type of microbes cause acute inflammation?
extracellular bacteria
Which type of microbes cause chronic inflammation?
intracellular bacteria
Most SSTIs (esp. community acquired) are caused by which 2 microbes?
Staph Aureus Strep pyogenes (GAS)
Special circumstances when the spectrum of causative microbes responsible for SSTIs is broader (3):
puncture wounds
penetrating
trauma
bites
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
Principles of Rx for SSTIs (3):
local hygienic care Incision & Drainage (I&D) Abx coverage for organisms only if: systemic ssx are present on PE in special circumstances (e.g. puncture) in special pt. pops.
Most SSTIs present acutely/chronically
acutely → rubor, calor, tumor, dolor
Key components of innate immunity (5):
AMPS cytokines dentritic cells PMNs complement
Signaling molecules that are an important component of the skin in preventing S. aureus and C. albicans infx (4):
IL-17
IL17R
STAT1
STAT3
Name that microbe:
clinical pres:
rapidly spreading rash, cellulitis lymphangiitis, or adenopathy
S. pyogenes
Name that microbe:
clinical pres.:
abscess formation
organ involvement may include: skin, blood, heart and bone
S. aureus
Name that microbe: gram(+) coccus in chains catalase(-) β-hemolytic Bacitracin sensitive
S. pyogenes
Name that microbe:
gram(+) coccus in clusters
coagulase (+)
catalase(+)
S. aureus
Abx of choice for S. pyogenes
penicillin
Post-streptococcal complications
acute rheumatic fever
post-strep. glomerulonephritis
Exotoxin superAg that contribute to TSS and rash of scarlet fever (S. pyogenes) (2)
Pyrogenic exotoxin A
Pyrogenic exotoxin C
Exotoxin involved in staphylococcal scalded skin syndrome (SSS)
Exfoliative toxin
Bacteriophage encoded exotoxin found in methicillin resistant S. aureus strains
Panton-Valentine Leukocidin (PVL)
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
