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 material Pseudomonas Lecture 14 Classification Classification Family Genera Species Pseudomonadaceae Pseudomonas/Pseudomonads P. aeruginosa General 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 Morphology In vitro growth Sputum CF patient Organization of Flagella Organization of Flagella specific staining procedure required to visualize flagella Structure Flagellum Structure Flagellum (not exam material) E. Coli Movement E. Coli Movement http://www.rowland.harvard.edu/labs/bacteria/showmovie.php?mov=swimming_ecoli Peritrichous Flagellar Peritrichous Flagellar Slow motion http://www.rowland.harvard.edu/labs/bacteria/showmovie.php?mov=fluo_bundle_500hz Peritrichous Flagellar http://www.rowland.harvard.edu/labs/bacteria/showmovie.php?mov=fluo_cell_near Ubiquitous (Soil, Water, Asymptomatic carriage on skin) 37OC optimal growth temperature but growth well between 4°C42°C Special media (Pseudomonas P or F agar) to produce blue or green colonies (pyocyanin vs. pyoverdine pigments) Colonies after 12days P. aeruginosa Culture P. aeruginosa grown on: P. aeruginosa
Pseudomonas agar F Pseudomonas agar P Pathogenesis Pathogenesis Extracellular 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 cells Pathogenesis Exotoxins and secreted enzymes Pyocyanin (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 receptor Pathogenesis Exotoxins and secreted enzymes Exoenzyme 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 S
Epithelial cells Wildtype bacteria ExoS mutant bacteria Pathogenesis Exotoxins and secreted enzymes Elastases (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 complement Pathogenesis Exotoxins and secreted enzymes Phospholipase C : heat labile hemolysine Rhamnolipid: heatstabile hemolysine Pseudomonas colonies are betahemolytic on blood agar Pathogenesis Pathogenesis Biofilm formation increases antibiotic resistance helps establish and maintain extracellular colonization Epidemiology/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 colonized Infections Caused by P. aeruginosa Biofilms Biofilms
Contact lens-associated corneal infection Catheter-associated infection Ventilator-associated pneumonia Chronic infection of cystic fibrosis patients Clinical Manifestation Clinical Manifestation Uncompromised Individuals
Swimmer’s 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 water P. aeruginosa P. aeruginosa Skin lesions Intensive Care Unit patient Tub Rash Skin lesion appear as round (1cm diameter) hardened, purple areas with ulcerated center Clinical Manifestation Opportunistic Infections 1) Due to tissue damage Eye Infections: initial trauma to the cornea, allows colonization by bacteria via contaminated water Corneal Ulcers develop prompt treatment necessary Clinical Manifestation Opportunistic Infections 1) Due to tissue damage Primary 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 bacteremia Burn Wound Infection Burn Wound Infection Clinical Manifestation Opportunistic Infections 2) Due to medical devices Urinary 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 devices Pneumonia: 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 pneumonia Clinical Manifestation Opportunistic Infections 3) Due to other disease Diagnosis Diagnosis Culture bhemolytic, pigmentation (P,F agar), sweet grape like odor Biochemical tests Nitrate reduction (anaerobic) Oxidase/catalase positive Drug resistance Drug resistance Drug Resistance Drug Resistance
Antibiotic β-Lactams Aminoglycosids Resistance Mechanisms β-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 Fluoroquinolones All of these resistance mechanisms have been found in P. aeruginosa isolates Treatment/Prevention Treatment/Prevention
Treatment: 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