This preview shows page 1. Sign up to view the full content.
Unformatted text preview: Midterm II Oct. 26th Midterm II Oct. 26th 40 questions Multiple choice Lectures 815 (Listeria to Pseudomonas) One question from lecture 14 Two questions from lab materialPseudomonasLecture 14Classification ClassificationFamily Genera SpeciesPseudomonadaceaePseudomonas/PseudomonadsP. aeruginosaGeneral Characteristics General Characteristics gramnegative Straight rods, sometimes slightly curved Arrange in pairs Single, polar flagellum (Motile) Capsule Nonfermentative (obligate aerobes) although it can use Nitrate as electron acceptor under anaerobic conditions Catalase and Oxidase positive Form biofilms!Morphology MorphologyIn vitro growthSputum CF patientOrganization of Flagella Organization of Flagellaspecific staining procedure required to visualize flagellaStructure Flagellum Structure Flagellum (not exam material)E. Coli Movement E. Coli Movementhttp://www.rowland.harvard.edu/labs/bacteria/showmovie.php?mov=swimming_ecoliPeritrichous Flagellar Peritrichous Flagellar Slow motionhttp://www.rowland.harvard.edu/labs/bacteria/showmovie.php?mov=fluo_bundle_500hzPeritrichous Flagellarhttp://www.rowland.harvard.edu/labs/bacteria/showmovie.php?mov=fluo_cell_nearUbiquitous (Soil, Water, Asymptomatic carriage on skin) 37OC optimal growth temperature but growth well between 4C42C Special media (Pseudomonas P or F agar) to produce blue or green colonies (pyocyanin vs. pyoverdine pigments) Colonies after 12daysP. aeruginosa CultureP. aeruginosa grown on: P. aeruginosaPseudomonas agar F Pseudomonas agar PPathogenesis PathogenesisExtracellular pathogen (see, EPEC)Pathogenesis Pathogenesis Adhesins: Pilus and non pilus adhesins, bind especially well to Basement Membrane component Laminin which is only exposed after damage of epithelium Capsule: antiphagocytotic, anticomplement, antiantibiotic LPS: Proinflammatory, leads to septic shock TTSS: transport of effector molecules into target cellsPathogenesis Exotoxins and secreted enzymesPyocyanin (Blue colony color): secreted in such large amounts that it colors sputum blue thought to inhibit ciliary movement of lung epithelium Exotoxin A (Protein synthesis inhibitor): AB toxin; structurally and functionally similar to diphtheria toxin but targets different receptorPathogenesis Exotoxins and secreted enzymesExoenzyme S+T: inhibit cytoskeleton polymerization (cell rounding) inhibit wound healing via inhibiting cell division (important for establishing colonization in epithelium)Effect of Exoenzyme S Effect of Exoenzyme SEpithelial cellsWildtype bacteriaExoS mutant bacteriaPathogenesis Exotoxins and secreted enzymesElastases (LasA and LasB): degrade elastin (major component of lung tissue, gives elasticity) induces tissue damage and thus helps establish and maintain colonization can also degrade complementPathogenesis Exotoxins and secreted enzymes Phospholipase C : heat labile hemolysine Rhamnolipid: heatstabile hemolysinePseudomonas colonies are betahemolytic on blood agarPathogenesis Pathogenesis Biofilm formationincreases antibiotic resistance helps establish and maintain extracellular colonizationEpidemiology/Transmission P. aerigunosa Ubiquitous in environment!!! Have minimal nutritional requirements and grow at wide variety of temperatures Persist on dry surface for months!! Ubiquitous within hospitals on all surfaces!!!! Epidemiology Epidemiology Opportunistic Pathogen; uncommon in healthy individuals Most common cause of opportunistic infections in Cystic Fibrosis patients (85% of patients are infected!) Important cause of nosocomial infections (10%) (Catheter, prosthetic devices and ventilators) 75% of all intensive care unit patients are colonizedInfections Caused by P. aeruginosa Biofilms BiofilmsContact lens-associated corneal infection Catheter-associated infectionVentilator-associated pneumoniaChronic infection of cystic fibrosis patientsClinical Manifestation Clinical Manifestation Uncompromised IndividualsSwimmers Ear: External otitis, treatment with topical antibiotics but sometimes more invasive form (Malignant External Otitis), requires more aggressive treatment (antimicrobial and surgical) Tub Rash: Folliculitis, usually benign and selflimiting Both are caused by exposure to contaminated waterP. aeruginosa P. aeruginosa Skin lesionsIntensive Care Unit patient Tub Rash Skin lesion appear as round (1cm diameter) hardened, purple areas with ulcerated centerClinical Manifestation Opportunistic Infections 1) Due to tissue damageEye Infections: initial trauma to the cornea, allows colonization by bacteria via contaminated water Corneal Ulcers develop prompt treatment necessaryClinical Manifestation Opportunistic Infections 1) Due to tissue damagePrimary Skin Infections: burn wounds expose deeper epithelial tissue which can be colonized by bacteria common in patients with sever burns leads to vascular damage and tissue necrosis and often also to bacteremiaBurn Wound Infection Burn Wound InfectionClinical Manifestation Opportunistic Infections 2) Due to medical devicesUrinary Tract Infections: mainly in patients with longterm catheters patient have undergone multiple rounds of antibiotic treatments for previous nosocomial infections, which selects for Pseudomonas (Resistance)Clinical Manifestation Opportunistic Infections 2) Due to medical devicesPneumonia: in immunocompromised patients (AIDS, Cancer therapy) with recent antibiotic treatment and currently on ventilator mortality as high as 70%Pneumonia: Cystic Fibrosis (defect in mucus expulsion from lung) or Chronic Granulomatous Disease (defect in phagocytic cells to kill bacteria) can lead to sever necrotizing pneumoniaClinical Manifestation Opportunistic Infections 3) Due to other diseaseDiagnosis DiagnosisCulture bhemolytic, pigmentation (P,F agar), sweet grape like odor Biochemical tests Nitrate reduction (anaerobic) Oxidase/catalase positiveDrug resistance Drug resistanceDrug Resistance Drug ResistanceAntibiotic -Lactams Aminoglycosids Resistance Mechanisms -Lactamase hydrolysis; decreased permeability; altered binding proteins Enzymatic hydrolysis by acetylation, adenylation, or phosphorylation; decreased permeability; altered ribosomal target Enzymatic hydrolysis by acetyltransferase; decreased permeability Altered target (DNA gyrase); decreased permeability FluoroquinolonesAll of these resistance mechanisms have been found in P. aeruginosa isolatesTreatment/Prevention Treatment/PreventionTreatment: Extremely difficult due to antibiotic resistance Even susceptible strains may become resistant during course of treatment Usually combination of two antibiotic with different targets are used Prevention: No vaccine available Due to ubiquitous nature of bacteria cannot be completely eliminated Maximal effort to avoid contamination of medical devices...
View Full Document
- Fall '08