GRAM POSITIVE RODS. Dr Hamed Al-Zoubi Ass. Prof. / Department of Microbiology

Transcription

1 GRAM POSITIVE RODS Dr Hamed Al-Zoubi Ass. Prof. / Department of Microbiology

2 Bacterial infections of GIT Corynebacterium Bacillus cereus and anthracis Clostridium

3 Corynebacterium Aerobic, non motile GPR, club shape, Chinese letters L V shapes 1 - C. diphtheria 2 - Others: low pathogenic ability e.g diphtheroids (skin, urogenital and commensals)

4 C. diphtheria: Corynebacterium Virulence and pathogenesis: Local invasion heat stable exotoxin bacteriophage tox gene A and B parts: Inhibit EF2 and protein synthesis leading to cell necrosis and death

5 Clinically: Transmission by respiratory route, skin contact Incubation 1-10 days, infectivity 2-4 weeks if untreated or 4 days if treated 1 Local inflammation in nasal, oral, pharyngeal, laryngeal areas <thick adherent green psuedomembrane < airway obstructionand death 2 systemic: Toxin tropism to brain, heart and adrenal glands Paralysis, heart failure low platelets

6 This child has diphtheria resulting in a thick gray coating over back of throat. This coating can eventually expand down through airway and, if not treated, the child could die from suffocation CDC 6

7 Diagnosis: Swab:Not from the membrane.. and tell the lab: Blood agar Loeffler medium for chromogenic granules Tensdale agar: has K tellurtite medium reduction by bacteria tellurium precipitation black colonies Toxin detection ELEK test or PCR

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9 Treatment: start ASAP antitoxin, penicillin plus gentamicin Prevention: toxoid vaccine DIPHTHERIA TETANUS AND PERTUSIS ( DTP) 2m,3m,4m,1y,6y

10 BACILLUS: GPR, aerobic, spore centrally located 1- Anthracis Non motile, glutamic acid capsule Plasmid toxin: increase vascular permeability and shock Zoonosis Inhalation: hemorrhagic pneumonia and sepsis Ingestion: bloody diarrhea and death skin scratch: vesicles that rupture leaving malignant black eschar

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12 Motile but 2 --Bacillus cereus : no capsule food poisoning by enterotoxin Cases in which vomiting, occurring within 1-6 h of ingestion, is the main symptom. Caused by preformed toxin, which is a low molecular weight, heat- and acid-stable toxin that can withstand intestinal proteolytic enzymes (similar to s. aureus). A diarrhoeal form of food poisoning, occurring 8-24 h after ingestion of spores caused by heat labile enterotoxins formed in the intestine.

13 Bacillus diagnosis: blood agar: (medusa head) grey wavy with projections Gram stain: String of pearls Appears G neg in old culture

14 TREATMENT Anthrax: penicillin Cereus: Symptomatic : fluids If antibiotic needed: Cindamycin or erythromycin Prevention : Human vaccines for Anthrax Cellualr antigen from culture supernatan Anthrax genetically engineered antigen

15 Clostridi Characteristics: um Gram positive anaerobic rods (appear as gram negative in old cultures) Spore forming, dust water soil... Anaerobics May appear G neg in old culture C. Botulinum and Tetanus : neurotoxins C. Perfringens and Difficile: enterotoxins

16 Clostridium botulinum Seven main types A-G: A, B and E are the commonest Each secretes antigenically distinct but functionally similar toxin (very potent) The toxin (heat labile): 1. Preformed in food that is badly preserved and processed (hygiene and heat) > food borne botulism (canned, smoked..) 2. Spores ingestion e.g Honey > germinate in the gut > toxin production > infantile or (intestinal) botulism

17 Clostridium Spores: botulinum Oval and subterminal

18 Clostridium botulinum Pathogenesis: Neurotoxin production > stomach absorption > circulation > neuromuscular junction (NMJ) > inhibition of acetylcholine release at the NMJ > flaccid descending motor paralysis

19 Clostridium botulinum Clinically (food borne and wound botulism ): Incubation period 12-48hrs in food borne Early: nausea, vomiting, weakness, dizziness but no fever Late: double vision, difficulty in swallowing, speaking and respiratory failure (descending motor paralysis) Infantile: weakness, altered cry, loss of appetite, loss of head control, Floppy child syndrome and sudden infant death syndrome

20 Diagnosis: Clostridium botulinum Isolating the organism or toxin from gastric aspirates, blood or stool Detecting Toxin in the food n.b: toxin-antitoxin approach Alert the lab

21 Treatment: Gastric wash Antitoxin (A, B, E) Clostridium botulinum Supportive: ICU and respiratory support, wound cleaning and debridement Prevention: Proper cooking and heating of food? Avoid suspicious canned food Proper processing, preservation and canning of food vaccine

22 Clostridium perfringens: It causes gas gangrene and food poisoning (HL) subterminal spores Toxins: Alpha toxin (phospholipase C, lecithinase): Degrades lecithin in mammalian cell membrane leading to cell lysis Other toxins: collagenase, proteinase, hyaluronidase Identification: Nagler agar: based on neutralisation of alpha toxin by a specific antitoxin

23 Clostridium tetani Widely distributed in the environment especially in the soil Gram positive, motile anaerobic rods (GNR in old culture) Spore forming: round terminal (drumstick, tennis racket) Not commonly seen due to vaccine (DTP)

24 Clostridium tetani Not commonly seen due to vaccine (DTP) Produce two plasmid coded exotoxins: 1. Tetnospasmin: Neurotoxin Heavy (binding ) and light chain (neurotoxic part) One antigenic toxin 2. Tetanolysin (haemolysin): pathogenesis not clearly known but? RBCs haemolysis produced when spores germinate and vegetative cells grow in necrotic tissues. The organism multiplies locally and symptoms appear remote from the infection site

25 Clostridium tetani Pathogenesis: Spastic paralysis inhibition of the inhibitory neurotransmitter gamma aminobutyric acid (GABA) > loss of inhibitory action on motor and autonomic neurons>

26 Clostridium tetani / pathogenesis

27 Clostridium tetani Clinically (tetanus): Mode of transmission: Spores > wound contamination(low oxygen) > germination to bacilli that secrete the toxins Incubation period: 3days 3 weeks Source: Infected wound and abscesses (~65%), eg, wood or metal, thorns...) Chronic skin ulcers are the source in approximately 5% of cases in the remainder of cases, no obvious source is identified (cryptogenic)

28 Clostridium tetani 1. Local: Muscles spasm and pain at/near injury site 2. Generalised: Trismus (locked jaw): may bite the tongue Opisthotonus: flexion and adduction of the arms, clenching of the fists, extension of the lower extremities spasm is stimulated by noise and light the patient is afebrile, has intact sensation Meningitis, seizures and coma

29 Clostridium tetani

30 Clostridium tetani Diagnosis: 1. Clinical (very useful): Sign and symptoms Vaccination history History of a trauma 2. Wound smear staining: may help 3. Culture 4. Toxin-antitoxin test in mice

31 Clostridium tetani Treatment: Wound debridement Treat in In a dark quite room Sedation, Muscle relaxant (e.g diazepam) and artificial ventilation Antibiotics: may be given to kill any vegetative forms metronidazole Tetanus immunoglobulin TIG Vaccination: Toxoid vaccine: formalin inactivated VACCINE as per vaccination program and a booster every 10 years

32 C. difficile Secrete toxins A (enterotoxin) and B (cytotoxin). > exotoxins that cause inflammation and mucosal damage. Most common cause of nosocomial diarrhea. Colonizes the colon of up to 3% of healthy adults and it increases to 15 25% of debilitated and antibiotictreated hospitalized adults. present in environment. Spread primarily on hands of HCW.

33 Risk factors 1. Antimicrobial exposure 2. Acquisition of C. difficile 3. Advanced age 4. Underlying illness 5. Immunosuppression 6. Tube feeds / Enema.. All are Modifiable but not 3. 1 & 2 are major

34 Clinical picture and Complications Asymptomatic colonization Diarrhea (mild to severe) Colitis +/- pseudomembranes (endoscopy) Toxic megacolon (radiology) Colonic perforation/peritonitis Sepsis and acute abdomen without diarrhea

35 Diagnosis Clinically Enzyme-linked immunosorbent assay (ELISA) for toxins A and B Endoscopy (pseudomembranous colitis)

36 Management Resuscitate the patient; fluids, electrolytes Isolate the patient: Private room or cohorting Stop antibiotics and the just in case ones. Daily monitoring. ANTIBIOTICS: metronidazole / and or vancomycin

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