Medical Microbiology Gram-Positive Bacilli PDF

Medical Microbiology Gram-Positive Bacilli Prof. Dr. Hazem Aqel Basic Medical Sciences Dept. Faculty of Medicine Al-Balqa’ Applied University  Corynebacteria Group Pleomorphic Gram-positive Bacilli. Diphtheroid: Aerobic, Normal Flora - Respiratory-Urinary tract and Skin. M...

Medical Microbiology Gram-Positive Bacilli Prof. Dr. Hazem Aqel Basic Medical Sciences Dept. Faculty of Medicine Al-Balqa’ Applied University  Corynebacteria Group Pleomorphic Gram-positive Bacilli. Diphtheroid: Aerobic, Normal Flora - Respiratory-Urinary tract and Skin. Mostly Nonpathogenic. Corynebacterium diphtheriae: Diphtheria is an acute, serious, highly infectious disease. Strains are facultative aerobes, non-motile, non-sporing pleomorphic Gram-positive bacilli, producing Chinese-character arrangement. Three biotypes: Gravis, Mitis, and Intermedius. Human Pathogen. Spreads by Droplets (droplet infection). Carriers are asymptomatic. Clinical cases: Inflammation and Necrosis in the throat, pharynx, and larynx (pseudomembranous). If toxigenic, Diphtheria Toxin (Lysogenic Strains) is released, High Fatality.  Diphtheria Toxoid (Triple Vaccine, DTP): given to children at 2, 4, and 6 months of age. Lab Diagnosis: Albert's and Gram stain - Direct Smear and Throat culture on Blood Tellurite Medium and Loeffler’s serum slope. Toxin production is tested by guinea pig inoculation or by gel precipitation (Elek) test. Treatment: Diphtheria antitoxic serum and antibiotics.  Listeria monocytogenes: Gram +ve Small Bacilli, flagellated, feebly motile at 37°C , but active tumbling motility at 25°C. Asymptomatic Human Carriers: Intestines, Vagina. Common in Animals. It causes Invasive Infection (listeriosis), Septicemia, Meningitis and Abortion. CSF direct smear: typical tumbling motility. Corynebacteria Bacillus species  Spore Forming Bacilli Gram+ve Spore-forming small/Large Bacilli, Aerobic or Anaerobic, Survive for a long period in dryness. Common in Nature: Soil, Dust, water and air and on Vegetations. Human / Animal Intestines and Feces. They are mostly Saprophytes. Few are pathogenic for humans and Animals. Aerobic Bacilli Group: Bacillus cereus: Contamination of Food ( Rice, Meat). Produces a heat- stable Enterotoxin causing food poisoning: Incubation Period: 1-24 hrs, causing Vomiting & Diarrhea. Treatment: conservative, no need for antibiotics. Aerobic Bacilli Bacillus subtilis: Small, short, thin bacillus with rounded ends. Motile and non-capsulated. Opportunistic Pathogen, can cause wound infection and Sepsis in Infants and in Immunocompromised Patients. Its spores are used as a test of the efficiency of sterilization for ethylene oxide. B. stearothermophilus – heat, B. pumilus – ionizing radiation. Bacillus anthracis: Gram-positive, Large, non-motile, rectangular bacilli, arranged in chains. Spores are oval and central. Aerobe and facultative anaerobe. Vegetative cells-readily destroyed by heat, Spores-highly resistant to heat. Man is infected from animals and its products: Cutaneous Anthrax- Wound Infect, Hemorrhagic Pneumonia & Septicemia by Inhalation, High Fatality. Biological War Agent. Animal - Intestinal Anthrax.. Fatal Lab Diagnosis: Culture of Specimens. Skin Ulcer, Rare Blood / Sputum , Culture on Blood & Chocolate Agar.  Clostridia Anaerobic, sporing, Gram-positive bacilli. Most sp. Are soil saprophytes, and few are pathogens. Anaerobic Clostridia Group: Produce Exo & Enterotoxins: High Fatality without Treatment. Clostridium tetani Tetanus is a highly fatal disease with a High Mortality rate, Localized infection/Surface or Deep in Tissues, Release potent neurotoxin (Tetanus toxin/tetanospasmin) produced when spores germinate, and vegetative cells grow in necrotic tissues. The organism multiplies locally, and symptoms appear remote from the infection site. Treatment: Surgical Debridement. Antibiotics (pen, clindamycin, metronidazole, Resistant to Aminoglycosides), Antitetanic serum, Tetanus toxoid (Vaccine). Lab Diagnosis: Specimens or Damaged Tissues: Gram-stain and Culture. Spores: usually terminal-bulging (wider than the bacterial body) Clostridium tetani Cl. perfringens  Neonatal tetanus: Fatal… Common in developing countries… failure of aseptic technique during the delivery of babies… Umbilical Stump. Clostridium other Species: Toxigenic & Invasive, produces Toxins (enterotoxin) and Enzymes (Collagenase, Hyaluronidase, α-Toxin). Contamination Deep Wounds - Bacteremia. Gas gangrene, Myonecrosis- Cellulitis.. Treatment: Surgical Debridement/ Amputation & Antibiotics. No Preventative Vaccine. A common cause of food poisoning.. Enterotoxin… Incubation: 6-24 Hrs, causing Intense Watery diarrhea, but No Fever. Lab Diagnosis: Culture of Specimens: Aspirated Fluid Wound/Blood. Wound Infection with Mixed Clostridia & Other Bacteria C.botulinum: Food-borne botulism is intoxication.. Ingestion of food containing preformed Clostridial Toxin (which prevents the release of acetylcholine at motor nerve ending), a Heat- Stable Exotoxins-Protein (20min /100C). Contamination of Canned Food: Meat, Fish, Beans. Botulism: Clinical symptoms begin 18-36 hours after toxin ingestion with weakness, dizziness, dryness mouth, Nausea, Neurologic features.. blurred vision, inability to swallow, difficulty in speech, weakness of skeletal muscles and Respiratory Paralysis.. Inhibition of the release of the neurotransmitter acetylcholine.. No Fever. Diagnosis: Clinical Features.. Rare Toxin Detection  Clostridium difficile: Habitat: Faeces of Healthy Adults (Carriers). Produces two toxins: Toxin A is enterotoxin, which causes fluid accumulation in the intestines. Toxin B is an extremely lethal (cytopathic) toxin. Pseudomembranous colitis.. Bloody Diarrhea… AntibioticAssociated diarrhea (Lincomycin-Clindymicin, Cephalosporines), Treatment: Stop antibiotics and give Vancomycin. Lab Diagnoses: Identification of toxins in stool specimens.