Non-Spore-Forming Gram-Positive Bacilli Corynebacterium C. diphtheriae Disease Diphteria Opportunistic infections by other Corynebacterium species (dipheroids)

Properties Club-shaped also V- or L-shaped Beaded appearance Methachromatic granules (Albert staining) Nonmotile no capsule Facultative anaerobic. Classified in CNM group.

Biotypes (based on colony shape, biochemical properties and virulence) Gravis Mitis Intermedius Belfanti

Clinical finding Common diphtheria (Nasopharyngitis) Incubation periodIncubation period of 2–5 days. Fibrinous exudate “pseudomembrane” Sore throat, fever, Enlargement of neck lymph nodes and neck edema. Irregulatory of cardiac rhythm, difficulties with vision, speech and swallowing. Corrosion of myelin sheaths in the central and peripheral nervous system leading to degenerating motor controlmyelincentralperipheral nervous system

Clinical finding Cutanous diphtheria (a secondary infection)secondary infection Antibody production: Blocking the fragment B and so preventing entry into the cell.

Transmission Humans the only natural host C. diphtheriae reside in the upper respiratory tract Transmitted by airborn droplet Infection at the site of a pre-existing skin lesion

Pathogenesis Invasivness Exotoxin

Invasivness Cord factor A glycolipid inhibits eukaryotic cell oxidation. Nuraminidase Removes N-acetyl nuraminic acid from musine membranes.

Exotoxin (Encoded by gen tox from a temperate phage) Fragment B. Binding of the toxin Fragment A. Enzymatic activity A B

Nicotinamide adenine dinucleotide phosphate (NAD) Exotoxin (A fragment) Nicotinamide ADP Reaction with EF2 ADP-EF2 Protein synthesis inhibition

Testing immunity (Schick’s test) Intradermal injection (0.1 mL): I. Cause inflammation (4-7 days later): No antitoxin in patient II. No inflammation: Antitoxin is present (Immune person)

Laboratory diagnosis Microscopic observation (differentiation from streptococcal and vansant nasopharyngitis) Isolating the organism Loffler’s medium a tellurite plate Tinsdal medium Demonstrating toxin production Animal inoculation Eleck test ELISA PCR to detect tox gene

Treatment Tracheostomy in children (to prevent croup) Tracheostomy Antitoxin unit (Intra muscular) Penicillin or erythromycin

Prevention Vaccination A combination of diphtheria toxoid, tetanus toxoid, and killed pertusis organism. Given at 2, 4 an 6 months of age, with a booster at 1 and 6 years of age and then each 10 years afterward. (DPT or DT) The toxoid is prepared by treating the exotoxin with 0.3% formaldehyde.

Listeria monocytogenes Small rod like “chinese character” No capsule, Facultative aerobic. Tumbling movement. Movement in 25 c Growing in 4c Small and smooth colony on blood with a narrow zone of beta-hemolysis Biochemical tests: Fermentation, Catalase + Oxidase +

Disease Meningitis and sepsis in 1.The fetus or newborn as a result of transmission across the placenta or during delivery. 2.Immunosuppressed adults (especially renal transplant patients) The infected mother: asymptomatic or influenzalike illness/ Abortion

Transmission The organism is distributed worldwide in animals, plants and soil. Transmission to human by contact with animals or their feces unpasteurized milk contaminated vegetables. Endogenously from gasterointestinal tract.

Pathogenesis InternalinE-cadherin Phagocytosis into epithelial cells Phagocytiosis By macrophages and hepatocytes Phagolysosome formation (acidic condition) Lysteriolysin O secretion Release from phagolysosome Inducing actin polymerization in cytoplasm Forming filopods

Lab. diagnosis Microscopic observation: Diphtheroids Isolation by culture: Blood and CSF samples on blood agar Colonies: Small, gray colonies with a narrow zone of beta hemolysis

Treatment Penicillin Resistant are rare Prevention Cell-mediated immunity is active but no immunization Limiting the exposure of immunosuppressed patients to potential sources

Spore-forming gram-positive bacilli Bacillus (Aerobic) B. antheracis, B.cereus Clostridum (Anaerobic) C. tetani, C. botulinum, C. perfringens, C. difficile

Bacillus anthracis Disease Anthrax (common in animal but rare in humans).

Properties A large rod with square ends. Frequently in chains A unique anti-phagocytic capsule is composed of D-glutamate. Non-motile (other members of the genus are motile.)

Transmission Spores persist in soil for years. Infection from animal products (hides, bristles and wool), contact with sick animal. Portals of entry: skin, mucous membranes, and respiratory tract.

Clinical findings A typical lesion: A painless ulcer with black, necrotic eschar. Local edema. Untreated cases progress to bacteremia and death. Woolsorter’s disease (pulmonary anthrax) is a life threatening pneumonia (by inhalation of spores).

Pathogenesis Invasiveness Exotoxin Anthrax toxin, has 3 components: -Protective antigen -Lethal factor: In the presence of protective antigen is rapidly fatal for mice. The action is unknown -Edema factor (an exotoxin): An adenylate cyclase dependent on protective antigen for its binding and entry into the cell.

Lab. diagnosis Samples: Exudate, Blood, sputum. Direct smear: Large rods in chains. Spores not seen in smears of exudate. Culture and biological/biochemical tests (Sensitivity to penicillin (String of pearls test), Fermentation, gelatin hydrolysis, Motility) No serological tests are useful

Prevention Preventing soil contamination Sterilizing dead animals and animal products. Protecting persons at risk of exposure with special clothes. Vaccination with cell-free vaccine for persons at high risk.

Treatment Penicillin No resistant strain isolated

Motile No capsule Saprophyte Bacillus cereus

Disease Food poisoning Rare infections: Meningitis, Osteomyelitis, … Transmission Spores on grains survive during steaming and rapid frying. Spore germinated when rice is kept warm. Portal of entry is the gastrointestinal tract.

Pathogenesis B. cereus produces 2 enterotoxins. Their actions is unclear. Clinical findings 1.Emetic syndrome A short incubation period (4 hours) with nausea and vomiting similar to staphylococcal food poisoning. 2.Diarrheal syndrome Involves a long incubation period (18 hours) with diarrhea and resembles clostridial gastroenteritis.

Lab. diagnosis Not usually done Treatment No antibiotic is given. Only symptomatic treatment Prevention Grains (specially rice) should not be reheated

Clostridiums An aerobic bacteria Clostridiums tetani Peritricus flagella Terminal spore Disease Tetanus (Lockjaw)

Clinical findings Incubation period: 4-5 days – several weeks Violent muscle spasms in the site of infection and then jaw) Lockjaw (trismus) due to rigid contraction of the jaw muscles, which prevents the mouth from opening: a characteristic known as “risus sardonicus”’. Low blood pressure Respiratory failure

Neonatal tetanus

Transmission Spores are widespread in soil. The portal of entry is a wound site. Germination of spores is favoured by necrotic tissue and poor blood supply in the wound.

Pathogenesis Tetanus toxin (tetanospasmin) It is carried intra-axonally (retrograde) to the central nervous system, where it binds to ganglioside receptors and blocks release of inhibitory mediators (e.g. glycine, Gamma- aminobutiric acid) at spinal synapses leading to hyper reflection and spastic paralysis.

Diagnosis History of wound and clinical picyure There is no microbiologic or serologic diagnosis. Organisms are rarely isolated from the wound site. Treatment Antitoxin does have a low effect Penicillin Respiratory support Muscle relaxants

Prevention Immunization with toxoid in childhood (2, 4, 6, 12 months ages) and every 10 years thereafter. When trauma occurs deeply: 1. Wound should be cleaned and debrided. 2. Tetanus toxoid booster should be given. 3. Tetanus immune globulin should be given. 4. Penicillin administered.

Clostridium botulinum Disease Transmission Pathogenesis Clinical findings Laboratory diagnosis Treatment Prevention

Transmission In soil ---> Alkaline vegetables/meat ---> canned/vacuum-packed ---> Spore germination ---> Toxin production ---> ingestion

Pathogenesis Botulinus toxin Observing from the gut ---> Carrying via the blood to peripheral nerve synapses ---> Blocking release of acetylcholine ---> Paralysis

Clostridium perfringens Disease: Gas Gangrene / Food Poisoning Transmission Pathogenesis Clinical findings Laboratory diagnosis Treatment Prevention

Transmission Soil, vegetative cells are members of normal flora in colon and vagina. Is associated with war wounds.

Pathogenesis and clinical findings Alpha toxin: Lecithinase Glycogen metabolism: Gas in tissues: Crepitation Treatment Penicillin Wounds should be debrided H2O2

Crepitation

Lab diagnosis Smear of tissue and exudate samples: large positive rods. Cultured anaerobically identified with fermentation reactions

Food poisoning Transmission: Soil and food. Survives cooking and grows to large numbers in reheated food, especially meat. Pathogenesis: An enterotoxin (a protein in the spore coat) Clinical findings: Incubation: 8-16 hours, then watery diarrhea with cramps and little vomiting. Resolves in 24 hours.

Treatment and prevention Treatment: Symptomatic – No antimicrobial drugs Prevention: cooking well

Clostridium difficile Disease Transmission Pathogenesis Clinical Finding Laboratory diagnosis Treatment Prevention

Disease Antibiotic-associated pseudomembranous colitis Transmission It is a part of normal flora of gasterointestinal tract (3%)

Pathogenesis Antibiotic (Clindamycin and ampicillin) supress drug-sensitive normal flora, allowing C. difficile to multiply: produce toxin. Toxin mechanism is unclear

Clinical findings Diarrhea Pseudomembranes (yellow-white plaques) on the colonic mucosa. Visualised by sigmoidoscopy.

Lab diagnosis Toxin detectable in stool affecting on cell cultured cells. Inhibition of cytotoxicity by specific antibody.

Treatment Withdrew the antibiotic Oral vancomycin instead along with fluids.