Unit 4 - Bacterial Pneumonia: Pseudomonas/Burkholderia and Chlamydia Flashcards
what are the Pseudomonad bacteria?
also called Burkholderia
- P. aeuroginosa
- B. cepacia
- B. pseudomallei
- B. mallei
explain P. aeuroginosa bacteriology?
- growth?
- use of Ab?
- G- rods, strict aerobes and non-fermenters
- oxidase+
- produces pyocyanin (exotoxin, bright green color) and pyoverdin (siderophore)
- glycocalyx (antiphagocytic slime layer)
- resistant to detergents and disinfectants (can live in just distilled H2O)
- extremely Ab resistant
explain P. aeruginosa pathogenesis?
-growth requirements?
fairly common saprophyte (opportunistic)
- usually free-living environmental that can be normal flora (skin surface) or opportunistic pathogen (in lungs)
- -ability to grow in water + Ab resistance + vulnerable patients = nosocomial pathogen
- minimal growth requirements (IV fluid, irrigation solutions)
who are “vulnerable” patients to P. aeruginosa?
- extensive burns
- chronic respiratory disease (CF)
- immunosuppression
- long-term catheterization
- IVs
- neonates
explain P. aeruginosa community-acquired pathogenesis?
- endocarditis in IV drug users
- otitis externa/folliculitis in underchloerinated hot tubs
- osteochondritis in puncture wounds through soles (most common in children)
- corneal infection in contact lens wearers
what are P. aeruginosa virulence factors?
- endotoxin: cell wall component (when bloodborne –> sepsis)
- exotoxin: can be released into tissue (ExoA, similar to diptheria) or injected into host cells (T2SS, ExoS, damages cytoskeleton)
- enzymes: elastase, protease (histotoxic, facilitate invasion of bloodstream)
- pyocyanin: interferes w/ terminal electron transfer system
- glycocalyx: antiphagocytic
- efflux pumps: toss antibiotics back out of cytoplasm
- outer membrane is 10-100x less permeable to antibiotics than E. coli
where can P. aeruginosa infection be? in healthy VS immunocompromised?
anywhere
- predominantly nosocomial UTI, CF pneumonia, burns
- local infections in previously healthy hosts
- if neonate or immunocompromised: sepsis, pneumonia, endocarditis, meningitis, acthyma gangrenosum has >50% mortality
what is ecthyma gangrenosum?
patch of destroyed tissue in immunocompromised due to P. aeruginosa
what does nonbacteremic pneumonia show on CXR?
resembles S. aureus
- diffuse bronchopneumonia
- -usually bilateral with distinctive nodular infiltrates with small areas of radiolucency
- pleural effusions
what does bacteremic pneumonia show on CXR?
progresses rapidly
- poorly-defined, hemorrhagic, subpleural, nodular areas with small central area of necrosis
- multiple, 2-15 mm, necrotic, umbilicated nodules with hemorrhagic parenchyma
what does P. aeruginosa lab show?
very easy to culture; must make aerobic and anaerobic (2nd will fail)
- culture relevant fluids (lung sputum, joint biopsy/aspirate, CNS CSF, blood for sepsis)
- nonfermenting, oxidase+, beta-hemolysis
- metalic sheen on triple-sugar-iron (TSI) agar
- green color on nutrient agar (pyocyanin)
- fruity aroma
what is P. aeruginosa treatment?
- remove/change catheters/IVs
- begin antibiotics immediately, with sensitivity testing (repeating during treatment; extremely antibiotic resistant)
- for uncomplicated UTIs, use ciprofloxacin
- for everything else, must use combo antibiotics
what is prevention of P. aeruginosa
- keep neutrophil count up
- remove/change catheters/IVs
- burn unit precautions
- handwashing
- experimental vaccines for CF patients
what is the bacteriology of B. cepacia?
similar to P. aeruginosa (grows easily in IV, irrigation)
- unlike P. aeruginosa, limited ability to infect healthy patients (“colonizing” instead of “infecting”)
- no pyocyanin
what is the relationship between B. cepacia and CF? how is this related to cepacia syndrome?
- CF/cepacia pneumonia is more common as CF survival improves
- cepacia pneumonia in CF centers forms outbreaks
- cepacia syndrome: accelerated pulmonary course with rapidly-fatal bacteremia
what is the pathogenesis of B. cepacia?
- CF pneumonia
- pneumonia if preexisting disease with neutropenia
- catheter-associated UTIs
- IV-associated septicemia
- wound infections (foot rot in swamp-deployed)
what is treatment of B. cepacia?
- no treatment required if otherwise healthy patient
- pneumonia + CF, cancer, HIV need exotic antibodies
- -as hard to kill as aeruginosa (same extreme antibiotic resistance)
- experimental vaccines available for CF
what is bacteriology of B. pseudomallei?
motile G- rod (similar to P. aeruginosa)
-developing nation veterinary disease (Melioidosis)
how is B. pseudomallei transmitted?
direct contact with contaminated water or soil
-human-to-human transmission is rare, but take standard precautions with mask on patient
what is the pathogenesis of B. pseudomallei?
- initial: flu-like symptoms + muscle tightness and light sensitivity
- can progress from acute local infection to septicemia in all organs (fatal in 7-10 days if not treated)
- septecemia involves:
- -flushing
- -cyanosis
- -disseminated pustular erruption
- -high fevers
- -rigor
- -bloody, purulent sputum
- may resolve and reactivate from lung abscesses years later (Vietnam veterans)
what are risk factors for B. pseudomallei?
- diabetes
- renal dysfunction
- chronic pulmonary disease
how does one diagnose B. pseudomallei?
- look at patient history (travel, work with animals)
- culture and G-stain from blood, urine, skin lesions
- -“wrinkled” colony morphology
- abnormal CXR + multiple small abscesses in liver and spleen on sonogram
how does one treat B. pseudomallei?
long-term ceftazidime
what is the bacteriology of P. mallei?
(AKA glanders; developing world veterinary disease)
- nonmotile G- rod
- maintained in animal reservoirs (not environment) so may be possible to eradicate
explain the pathogenesis of B. mallei
- animal discharge passes through broken skin
- rare human-human transmission
- initial symptoms are flulike, but may progress:
- -acute localized: nodule at infection site
- -acute pulmonary: bronchitis, pneumonia
- -acute septicemic: fulminant, multiorgan
- -chronic infection: farcy
- if infectious dose is high, bacterial toxins may cause additional symptoms
what is the septicemia associated with B. mallei?
similar to B. pseudomallei
- flushing
- cyanosis
- disseminated pustular eruption
- fatal in 7-10 days
how to diagnose B. mallei?
patient history, culture, G-stain from urine, blood, skin lesions
-PCR and IF assays exist, but must go to CDC
what is treatment for B. mallei?
long-term amoxicillin and clavulanate
-reportable to FBI and CDC (as weaponizable)
what is the bacteriology for Chlamydia pneumoniae?
human-borne community-acquired
- respiratory secretions transmit from human to human
- causes 3-10% of adult community-acquired pneumonia
- pear-shaped elementary bodies
what is the bacteriology for Chlamydia psittaci?
bird-borne rare airborne zoonosis
- infected birds transmit via respiratory route through direct contact or aerosolization
- rare but serious
what is the bacteriology for Chlamydia trachomatis?
infant is infected at birth
-transmitted when infant passes through infected birth canal –> conjunctivitis and pneumonia
explain the history/exam of C. pneumoniae
3-4 week incubation period
- infection is common and asymptomatic or mild
- fever in first few days, likely absent by time of exam
- rhonchi and rales present in mild disease
- headache, sinus percussion tenderness
- symptoms may be prolonged
explain the history/exam of C. psittaci
exposure to sick birds
- 5-14 day incubation period, abrupt onset
- can be asymptomatic to severe pneumonia
- nonproductive cough, chest pain, splenomegaly
- fever is most common symptom (103-105)
- Horder spots: erythematous, blanching, maculopapular rash
- severe cases –> meningitis, encephalitis, endocarditis
explain the history/exam of C. trachomatis
birth-infected infant or severely immunocompromised adults
- nasal obstruction and discharge
- cough, tachypnea
- conjunctivitis
- middle ear abnormality
- scattered crackles with good breath sounds
- most patients afebrile, only moderately ill
explain lab results for C. pneumoniae
- MIF Ab tests, serology (pear shaped EB)
- cell culture impractical
- chest radiograph: single subsegmental infiltrate in lower lobes
explain lab results for C. psittaci
- complement fixing or MIF Ab tests, serology
- cell culture is hazardous (infectious)
- radiograph: consolidation in single lower lobe
explain lab results for C. trachomatis
- culture or hybridization like genital chlamydia
- radiograph: bilateral interstitial infiltrates with hyperinflation
explain treatment for C. pneumoniae
- doxycycline
- alt: erythromycin, azithromycin, clarithromycin, telithromycin
- most cases are mild and respond to outpatient treatment
explain treatment for C. psittaci
- tetracycline or doxycycline
- curable in 7-14 days with early diagnosis and treatment
explain treatment for C. trachomatis
- treat infants with oral erythromycin (not just eye ointment)
- most patients are moderately ill and respond to appropriate antibiotics
- course is protracted if untreated
