Corynebacterium Presentation PDF

CORYNEBACTERI UM BY DR NWAFIA IN  To Know the microbiology of Corynebacterium species  To Understand the epidemiology  To Understand the pathogenesis and clinical features  To understand the clinical and laboratory diagnosis of Corynebacterium infection  To know the treat...

CORYNEBACTERI UM BY DR NWAFIA IN  To Know the microbiology of Corynebacterium species  To Understand the epidemiology  To Understand the pathogenesis and clinical features  To understand the clinical and laboratory diagnosis of Corynebacterium infection  To know the treatment of the infection  Introduction  Greek word - koryne- club - Bacterion- little rod  It has a clubbed shaped appearance.  1884-Edwin Klebs  Consists of a diverse group of bacteria including animal and plant pathogens, as well as saprophytes.  Some are part of the normal flora of humans.  Can cause respiratory tract, wounds. skin infection  Can infection in immuno-compromised hosts  Metachromatic granules - best seen with methylene blue staining  Introduction continued…..  The genus contains the species  - Corynebacterium diphtheriae - clinical important  -Nondiphtherial corynebacteria, collectively referred to as diphtheroids. - C. ulcerans, C. pseudotuberculosis and C. xerosis  Nondiphtherial corynebacteria, were originally thought to be mainly contaminants, but is now recognized as pathogenic, especially in immuno-compromised hosts  Diphtheria toxin is extraordinarily potent. The lethal dose for humans is about 0.1 μg of toxin/kg BWT  A massive release of toxin into the body will likely cause lethal necrosis of the heart and liver.  Introduction continued  4 strains of C. diphtheriae C. gravis- More virulent C. intermedius C. mitis C. belfanti  These strains all produce an identical toxin, which is responsible for many of the clinical manifestations of the disease .  Microbiology  Aerobic or facultative anaerobic  Gram-positive rods - 0.5- to 1.5µm in diameter  Clubbed shaped appearance.  Non motile and non-spore forming  Catalase-positive  Non-motile rods  Haemolytic or non-haemolytic  Club shaped appearacnce  Chinese letters- Stained bacterium tends to lie parallel or at acute angles with one another  Epidemiology  Asymptomatic nasopharyngeal carriage is common in regions where diphtheria is endemic  Transmission- droplets or direct contact.  Infection is spread solely among humans, although toxigenic strains have been isolated from horses.  In regions where immunization programs are maintained, isolated outbreaks of disease are often associated with a carrier who has recently visited a subtropical region where diphtheria is endemic. Large-scale outbreaks of disease may occur in populations where active immunization programs are Pathogenesis  Pathogenesis  Exotoxin composed of two segments: A and B  B binds to specific receptors on susceptible cells and allows the Segment A to enter into the cytosol by endocytosis process  Fragment A catalyses the transfer of ADP-ribose from NAD to the eukaryotic elongation factor-2 (EF-2)  Loss of this enzyme prevents the protein synthesis  The toxin affects all cells in the body, but the most prominent effects are on the heart, nerves and kidneys  Pathogenesis continued…..  Within the first few days of respiratory tract infection, toxin elaborated locally induces a destruction and superficial inflammatory response. The necrotic epithelium becomes embedded on exhibiting fibrin and RBC and WBC forming a greyish Pseudomembrane commonly over the tonsils, pharynx or larynx  Removal of this adherent gray-brown pseudomembrane reveals a bleeding edematous submucosa.  The underlying soft tissue edema and cervical adenitis can be intense  The regional lymph nodes in the neck enlarge and there may be marked edema of the entire neck. Pathogenesis continued…..  In both adults and children, a common cause of death is suffocation after aspiration of the membrane.  The diphtheria bacilli continue to multiply and produce toxin which absorption result in distant toxic damage particularly in heart muscle, liver, kidneys and adrenals sometimes accompanied by gross hemorrhage.  The toxin also produces nerve damage often resulting in paralysis of the palate, eye muscles or extremities.  Clinical features  The incubation period is 2-5 days ( 1-10days)  Patients initially presents with malaise, sore throat and moderate fever. A thick adherent pseudo membrane is present in one or both tonsils or adjacent pharynx.  In severe cases, it can involve nasal mucosa, pharyngeal wall and soft palate, resulting to edema involving the cervical lymph glands.  The patient is gravely ill with a weak pulse, restlessness and confusion.  Clinical features  Laryngeal movement leads to obstruction of the larynx and lower airways.  Myocarditis, peripheral neuritis, Visual disturbances, difficulty in swallowing, paralysis of arms and legs occur but usually resolve spontaneously.  In cutaneous cases, the lesion is usually characterized  by an ulcer covered by a necrotic pseudo membrane and may involve any area of the skin.  Laboratory diagnosis Specimen  Swabs from the nose, throat, skin  Biopsy. Microscopy  Smears of the swab stained with methylene blue or Gram stain show typical beaded rod in Chinese letter arrangement Culture- blood agar, Tellurite, Loefflers slant  Culture Media Tellurite Blood Agar Blood agar Tinsdale agar  Eleks test  Detection of toxigenic strain  Schick test  A Schick negative person is immune and need not be immunized  Lab. diagnosis  Molecular- PCR  ELISA  Immuno-chromatographic  Guinea pig assay  Treatment  Treatment of diphtheria rests largely on rapid suppression of toxin production and the early administration of specific antitoxins against the toxin formed  Antitoxin  Antibiotics - Penicillin - Erythromycin  Prevention  Immunization with diphtheria toxoid is extraordinarily effective- Pentavalent vaccine