40. Pseudomonas and ICU GNRs Flashcards
pseudomonas microbiology?
- aerobic
- non-lactose fermenting
- oxidase positive
- GNR
- grows easily on many substrates
- characteristic sweet grape-like odor
- many strains produce diffusible pigments (fluorescein & pyocyanin)
pseudomonas epidemiology?
ubiquitous in the environment
- throughout hospital env’t:
- fluids (dialysis, ophthalmic, rinses, water taps)
- equipment (whirlpools, respiratory, endoscopes, humidifiers, catheters)
- Pseudomonas aureginosa is species most commonly encountered
- primarily opportunistic, nosocomial (disease when host defenses compromised, disturbed physical barriers, immune dysfunctions, chronic lung disease esp CF)
Hot tub folliculitis
Likely only CA-pseudomonas infection (8-24 hours post exposure to contaminated water, tender, purutic papules or pustules, low grade fever)
pseudomonas pathogenesis?
- pili, flagella involved in adherence
- LPS (endotoxin)
- polysaccharide capsule (slime, mucoid coat):
- interferes w/ phagocytes, Abs, C’, Abx
- aids adherence/ biofilm formation
- elicits inflamm cytokines
- mucoid strains very common in CF pt
pseudomonas virulence factors?
Exotoxin A (ETA)
- single chain polypeptide
- mode of action similar to diphtheria toxin (inhibits protein synthesis by transferring ADP-ribose to EF2)
- necrotizing activity in tissue; toxic for phagocytic cells; involved in local and systemic disease
Type III secreted toxins
- eg Exoenzyme S (ExoS) transfers ADP-ribose of NAD to GTP binding proteins of ras superfamily
Degradative enzymes:
- phospholipase C (breaks down lipids, lecithin, pulmonary surfactants, erythrocytes)
- elastase (degrades elastin, collage, IgG, etc)
- cytotoxin/leukocidine (damages PMN membranes)
- proteases
pseudomonas disease?
Pneumonia (HCAP, VAP)
- nosocomial
- esp w/acid destruction of resp epithelium (aspiration)
- fevers, chills, dyspnea
- Dx: syndrome and isolation from cs
- prognosis: prolonged hosp stay, high mortality
Bacteremia
- HA-BSI, higher in ICU
- primary infec from pna, cath, UTI, GI tract
- up to 39% mortality
- ¬¬ecthyma gangrenosum (usu immune compromised, perivascular bacterial invasion of media/adventitia, ischemic necrosis, ulceration w/punched out lesion, raised violaceous margins)
Endocarditis
- rare but high mortality (90% in IV drug users)
Skin/ST infections
- burn pts
- 49% mortality, 77% mortality w/bacteremia
- wound infections blue-green exudate w/fruity odor
Osteomyelitis
- rare, surgical site, high morbidity
UTI
- nosocomial cath, bacteremia poss
Eye infections
- rapidly destructive
- assoc w/contam contact lens solution
Otitis Externa
pseudomonas tx/prevention?
Piperacillin-Tazobactam
3rd-4th generation cephalosporins
- cefepime
- ceftazidime
Newer cephalosporins
- ceftazidime/avibactam (no real benefit)
- ceftolozane/ tazobactam (MDR)
Aminoglycosides (don’t use alone, but for synergy or combo re: MDR)
Carbapenems (except ertapenem)
Fluoroquinolones (esp ciprofloxacin)
Aztreonam (if PCN allergy)
acinobacter baumanii microbiology?
Gram(-) coccobacilli
- non-motile, aerobic
- non-lactose fermenter
- oxidase negative
acinobacter baumanii epidemiology?
- env’t, water, soil
- colonizes skin, resp tract, and GI tract
- nosocomial pathogen in the ICU
- historic assoc w/war wound infections
- not a pathogen of healthy individuals
acinobacter baumanii pathogenesis?
- can survive for long periods of time in dry conditions
- polysaccharide capsule that prevents complement activation
- colonizes damaged respiratory tract, can lead to invasive infection
- can dev resistance through accum of multiple diverse mechanisms
acinobacter baumanii disease?
- often MDR
- VAP, CAUTI, CLABSI, wound infections
acinobacter baumanii tx/prevention?
- broad spectrum cephalosporin
- carbapenem
- beta lactam/beta lactamase inhibitor: ampicillin/sulbactam (the sulbactam alone has activity vs acinetobacter!)
- fluoroquinolone
- aminoglycoside
- tigecycline (low bloodstream levels, not good for bacteremia)
- polymixins
- often MDR requiring combination therapy due to poor activity of available drugs
ESBL tx?
Extended Spectrum Beta Lactamases (ESBLs) – tx w/ carbapenems, aminoglycosides, tigecycline, ceftolozane-tazobactam
CRE tx?
carbapenem resistant Enterobacteraciae (CREs) – tx w/ aminoglycoside, polymixin, tigecycline, ceftazidime-avibactam
stenotrophomonas maltophila epi, disease and tx?
Often colonizes respiratory tract (CF, vents, etc)
Not very virulent but difficult to treat
TMP/SMX (tigecycline if need be)
burkholderia cepacia epidemiology and disease?
Mostly seen in CF
Similar to PSA
