38. Strep Pneumoniae and Enterococcus Flashcards
streptococcus pneumoniae microbiology?
catalase -
gram +
cocci in pairs and chains
a-hemolysis
susceptible to optochin
soluble in bile salts
strep pneumoniae virulence?
- evasion of host immunity (polysaccharide capsule = antiphagocytic esp for ppl w/no spleens, pneumolysin mediates destruction of phagocytic cells)
- adherence to host tissues (phosphocholine binds to receptors on endothelial cells, leuks, platelets, tx; surface adhesion proteins binds to squamous epith cells in orpharynx)
- few toxins
strep pneumo abx resistance?
- some resistance to PCNs (93% susceptible)
- resistance via PBP2
- acquired from other streptococci like S.mitis
- less of a problem w/streptococcus than enterococcus
- some resistance to macrolides (85% susceptible, due to ermB or mefA)
- little to no resistance to fluoroquinolones
- 35% resistance to TMP-SMX
strep pneumo pathogenesis
- diseases occur when bug in oropharynx migrates to sterile areas: lower airways (pna), paranasal sinuses (sinusitis), ears (otitis), meninges (meningitis)
- bacteremia assoc w/infections of lungs/meninges (rare in pts w/sinusitis or otitis)
- preceded by viral respiratory infection (can led to trapping of S.pneumo)
strep pneumo epi?
- colonizes nasopharynx (prevalence of colonization 40-60% of adults)
- most cases of pneumococcal bacteremia in adults caused by pna
strep pneumo RFs?
- lack of receipt of pneumoccal vaccine
- splenectomy
- inability to form antibody (multiple myeloma or AIDs)
- rare immune deficiencies
- poorly functioning PMNs (alcoholism, cirrhosis, diabetes, glucocorticoid tx, renal insuffic)
- prior resp infec
- inflammatory conditions (COPD, asthma, smoking)
common clinical presentations of strep pneumo?
otitis, sinusitis, bronchitis, pneumonia, meningitis, bacteremia
otitis media?
strep pneumoniae is the most common bacterial isolate, but can be hemophilus influenzae
Abx not needed initially
if persistant fever, then amoxicillin
acute sinusitis
virus is precipitating factor
abx?
- persistant and not improving (>10days)
- severe (>3 days)
- worsening (>3 days)
amoxicillin+clavulanate (covers H.influenza and M.cattarhalis better)
respiratory fluoroquinolones
macrolides - increaseing S.pneumo resistance
pneumococcal meningitis
most common cause of bacterial meningitis (second is neisseria meningitis)
direct extension from sinuses or middle ear or bacteremia
abx of choice: ceftriaxone (good CSF penetration) PLUS vancomycin until susceptibilities
gram stain of CSF makes Dx
must obtain LP
must start Abx ASAP
pneumonia
acute onset
fever, chills, myalgias, pleuritic chest pain, dyspnea, productive cough
typical pathogens: S.pneumo, S.aureus, H.influenzae, M. cattarhalis
…….more likely to be dense lobar or multi-lobar consolidation
atypical pathogens: viruses, mycoplasma, chlamydia, legionella, fungi
……more likely to be patchy or bilateral
tx:
empiric tx includes atypical coverage
outpt: macrolide or doxycycline (incl s.pneumo resistance)
…if comorbidities or recent prior abx give respiratory fluroquinolone (not ciprofloxacin re: poor s.pneumo activity) like moxifloxacin
inpt: ceftriaxone (or other beta lactam) + atypical coverage, or respiratory fluoroquinolone
strep pneumo vaccination?
pneumococcal polysaccharide vaccine (pneumovax = PPSV 23)
- ppl 65+
pneumococcal protein-conjugate vaccine (Prevnar 13 = PCV13)
- kids to prevent invasive pneumococcal disease (bacteremic or sequelae)
- ppl 65+
enterococcus microbiology?
catalase -
gram+
cocci in pairs and short chains
facultative anaerobes
grows readily on most lab media
PYR positive
live in GI tract
enterococcus virulence?
surface adhesions: binds to host cells
tissue damage by cytolysins and protease (doesn’t cut through fascial planes)
ABX RESISTANCE
enterococcus abx resistance?
abx alter gut flora so increased growth of enterococci and abx-resistant like VRE
inherent resistance to cephalosporins, oxacillin
acquired resistance to aminoglycosides, FQ, vancomycin
enterococcus epidemiology
2nd most common cause of nosocomial infections in the US 9Drains, cental lines, urinary catheters, other prosthetics)
if you use a drain to take a culture, can only do so when you FIRST place it because it will be colonized with enterococcus quickly no matter what
VRE = 30% of above infections
clinical presentations of enterococcus?
bacteremia
endocarditis
UTI
intra-abd and pelvic infection
enterococcus bacteremai
usu due to IV catheters
secondary to infeciton at other sites (UTI, drain, etc)
need to differentiate from endocarditis (tx and outcomes are very different, echocardiogram to eval heart valves)
tx: 2 week course
enterococcus endocarditis
fever, malaise, rigors, myalgias, often of prolonged duration
echocardiographic evidence of vegetation
higher concern w/prosthetic valves
sequala of metastatic disesa:
- pulm emboli
- abscess
- janeway lesions, roth spots, osler nodes, splinter hemorrhages
enterococcus UTI
commmon in hospitalized males
urinary tract instrumentization or foley catheter
tx w/single abx
enterococcus intra-abdominal and pelvic infections
enterococci are commensals of GI and GU tracts
frequently isolated from abdominal and pelvic infections/cultures (usually polymicrobial w/GNRs and anaerobes)
role of enterococci in these infections in terms of pathogens is contoversial
- could be colonizer, could be pathogen
in many serious infections, if isolated on culture, abx chosen should cover these bacteria
skin and soft tissue enterococcus infections?
in skin and soft tissue cultures, it is often a colonizer, so DON’T TREAT
if isolated from a deep/sterile culture, eg bone culture in diabetic foot infection, then treat
antibiotic resistance of E.faecalis
abx of choice: ampicillin
ampicillin preferable to vancomycin (re VRE)
for endocarditis need to abx: ampicillin and aminoglycoside
B-lactams used for enterococcus (ampicillin, ampicillin-sulbactam, or piperacillin-tazobactam)
carbapenems and cephalosporins w/limited to NO activity
Abx resistance to E.faecium?
not susceptible to ampicillin!
agent of choice: vancomycin
for endocarditis need 2 abx:
- vancomycin and aminoglycoside (both nephrotoxins but have to use it)
VRE treatment options?
linezolid (oral or IV, covers MRSA or VRE but not cidal drug, but still approved for bacteremia - an exception to the norm)
daptomycin (cidal and covers VRE but expensive)
tigecycline (black box warning because good tissue penetration and not good [ ] in the bloodstream)
ceftaroline?
