lectures 8-11-bacillus anthracis; b. cereus, clostridium perfringens, cl. tetani; cl. botulinum; cl....

بسم الله الرحمن الرحيمبسم الله الرحمن الرحيم

FAMILY: BACILLIACEAEFAMILY: BACILLIACEAEProf. Khalifa Sifaw GhengheshProf. Khalifa Sifaw Ghenghesh

1. GENUS: 1. GENUS: BACILLUSBACILLUS

• Gram +ve bacilli

• Aerobic

• Spore-Forming

i. i. Bacillus anthracisBacillus anthracis• >> Anthrax.

• Large, Square - ended Rods, Arranged in Chains.

• Non-Motile.• Spores:• Capsule: – Purple Stained >> McFadyan's Method

(Polychrome Methylene Blue).

• Colonies on BA: "Medusa Head Appearance"

Bacillus anthracisBacillus anthracis

An electron micrograph of spores from An electron micrograph of spores from the Sterne strain ofthe Sterne strain of Bacillus anthracisBacillus anthracis

Bacillus anthracisBacillus anthracis McFaydean capsule McFaydean capsule stain, grown at 35stain, grown at 35ooC, in defibrinated C, in defibrinated

horse blood.horse blood.

DISEASE:• In Animals: >> Septicaemia.

• In Humans: i. Cutaneous Anthrax > Malignant pustule

ii. Pulmonary Anthrax (Wool-Sorter'sDisease).

iii. Gastrointestinal Anthrax.

Cutaneous AnthraxCutaneous Anthrax

Anthrax lesion on the skin of the Anthrax lesion on the skin of the forearm caused by forearm caused by Bacillus anthracisBacillus anthracis

PATHOGENESIS• Capsule > Invasiveness– D-glutamic acid

• Exotoxin (Plasmid mediated)i. Protective Factor (Antigen).

ii. Oedema Factor.

iii. Lethal Factor.

Blocks the Adenyl Cyclase Pathway > Increases vascular Permeability > Shock

LABORATORY DIAGNOSIS:• Specimens obtained from:

a malignant pustule, sputum, blood.

- Gram stain + fluorescent-antibody stain.

- Motility

- Capsule formation: Sodium bicarbonate +CO2

- String-of-pearls reaction:

- Mouse test:

- API

>> Demonstration of Abs to the organism:

Bicarbonate agar and blood agar Bicarbonate agar and blood agar plate cultures of plate cultures of Bacillus anthracisBacillus anthracis

Negative encapsulation: Blood agar and Negative encapsulation: Blood agar and bicarbonate agar plate cultures of bicarbonate agar plate cultures of

Bacillus cereusBacillus cereus

• TREATMENT– Penicillin, Ciprofloxacin

• IMMUNIZATION–Animals > Live spore vaccine

(Sterne strain)

–Workers at Risk of Exposure >

Anthrax Vaccine Absorbed (AVA) >> “Alum precipitated toxoid”

ii. ii. Bacillus cereusBacillus cereus

• Food Poisoning.

• Clinical Syndromes:

i. Severe Nausea &Vomiting.

ii. Abdominal Cramps & Diarrhoea.

PATHOGENICITY:>> Due to an Enterotoxin.

• Also Causes Disease in Patients with Underlying Disease.

• TREATMENT:

>> Tetracycline, Erythromycin.

• iii. B. subtilis:

• iv. B. stearothermophilus.

2. GENUS: 2. GENUS: CLOSTRIDIUMCLOSTRIDIUM

• Gram +ve bacilli

• Anaerobic,

• Spore Forming

- Spores:

Ink Stain of Sporulating Ink Stain of Sporulating ClostridiumClostridium--spores appear clear, vegetative cells darkspores appear clear, vegetative cells dark

i.i. Clostridium perfringens Clostridium perfringens

• Nonmotile

• Spores Not Produced in Ordinary Media.

• Aerotolerant Anaerobe.

• 5 Types: A - E

Gram stain of Gram stain of Clostridium perfringensClostridium perfringens

Exudate smear of Exudate smear of Clostridium perfringensClostridium perfringens

Tissue smear of Tissue smear of Clostridium perfringensClostridium perfringens

DISEASE:

• Clostridial Myonecrosis.

• Less Severe Wound Infections.

• Food Poisoning.

Patient with gas gangrenePatient with gas gangrene

LABORATORY IDENTIFICATION

• In Chopped Meat - Glucose Medium:

• On BA:

• On Egg Yolk Agar: >> Precipitation (Opalescence).

• Milk Media: Stormy Formation.

• Nagler Reacrion:

Blood agar plate with Blood agar plate with Cl. perfringensCl. perfringens characteristic double zone of hemolysischaracteristic double zone of hemolysis

PATHOGENICITY & CLINICAL INFECTION-Toxin: Acts on Lecithin-Containing Lipo-

protein Complexes in the Cell Membrane.

• Predisposing Factors:i. Trauma with Deep and Lacerated or Crush

Wounds of Muscle Etc.

ii. Require a Reduced Oxygen Tension and

Reduced Oxidation Reduction Potential

for Growth.

FOOD POISONING:

• Cl. perfringens Type A >> Enterotoxin.

> Acute Abdominal Pain and Diarrhoea.

LABORATORY DIAGNOSIS:• Important: Diagnosis of Clostridium

Myonecrosis Should Be Rapid and Made on Clinical Grounds.

i. Direct Smear and Gram Stain of Material

from Deep Within the Wound.

ii. Culture: Tissue Aspirates or Deep Swabs Taken from Affected Muscle.

TREATMENT:• Clostridium Myonecrosis:

i. Surgical Removal of All Infected and

Necrotic Tissue.

ii. Antibiotic and Antitoxin Therapy.

iii. Adminstration of Hyperbaric Oxygen.

• Food Poisoning:

Clostridia That May Be Associated

with Gas Gangrene:

• Cl. perfringens Type A• Cl. septicum• Cl. novyi Type A• Cl. histolyticum• Cl. Sordellii

Human case of malignant edema Human case of malignant edema caused by caused by Cl. septicumCl. septicum

ii. ii. Clostridium tetaniClostridium tetani

• > Tetanus.

• > Terminal Spores with Drumstick

Appearance.

• > Obligate Anaerobe.

Clostridium tetaniClostridium tetani Gram Positive RodsGram Positive Rods

Clostridium tetaniClostridium tetani

VIRULENCE FACTORS:• Tetanus Toxin (Tetanospasmin) >

Neurotoxin.

i. An Intercellular Toxin Released by

Cellular Autolysis.

ii. Inhibits the Release of Inhibitory

Transmitters.

iii. Toxoid.

CLINICAL INFECTION & PATHOGENESIS• "Tetanus is Generalized in Nature".

i. Unimmunized Rural Population.

ii. In Practice: Simple Puncture Wounds >

Nail, Splinter or Thorn.

iii. In Traumatic Wounds > Compound

Fractures, Dental Extractions, Etc.

iv. Tetanus Neonatrum:

v. Postoperative Tetanus:

Drawing of a Soldier dying of Drawing of a Soldier dying of Tetanus (Opisthotonos)Tetanus (Opisthotonos)

A patient presented with facial tetany. A patient presented with facial tetany. Note the contraction of the masseter and Note the contraction of the masseter and

neck musclesneck muscles

LABORATORY DIAGNOSIS:• > Diagnosis on Clinical Grounds.

TREATMENT:• i. Antitoxin.• ii. Debridement of Wound and Removal of • any Foreign Bodies.• iii. Pencillin >>> In Large Doses.• iv. Mild Tetanospasm: >>> Barbiturates.• v. Severe Cases: • >>> Use Curare - Like Agents.• >>> Tracheostomy.• >>> Careful Control of the

Environment.

PREVENTION:> Prompt and Adequate Cleaning of

Wounds.

i. Active Immunity.

ii. Passive Immunity.

iii. iii. Clostridium botulinumClostridium botulinum

• > Botulism.

• > Gram +ve, Spore Forming Bacilli.

• > Strict Anaerobe.

Gram Stain of Gram Stain of Cl. botulinumCl. botulinum, , Characteristic Long RodsCharacteristic Long Rods

A photomicrograph of A photomicrograph of Clostridium botulinumClostridium botulinum type A type A

Blood Agar Plate with Blood Agar Plate with C. botulinumC. botulinum

VIRULENCE FACTORS• Botulinum Toxin >>> Neurotoxin.–Serologically 8 Toxins >>

A, B, C1, C2, D, E, F & G.

> Affect the Cholinergic System > Blocks the Release of Acetylcholine (at Points in Peripheral Nervous System).

DISEASE IN HUMANS1. Food - Borne Botulism:> Incubation Period: 12-36 Hours to 8 days.

2. Infant Botulism:

LABORATORY DIAGNOSISi. Diagnosis Made Clinically.ii. Detection of Organism or Its Toxin in the Suspected Foodiii. Samples of Stool or Vomit

TREATMENT & PREVENTIONImportant: Specific Treatment Should

Begin as Quick as Possible.

>Polyvalent Antitoxin >>> Immediately.

>Physiological Support >>> ICU.

>NEVER Use a Swollen or Defective Can.

iv. iv. Clostridium difficileClostridium difficile

• Antibiotic Associated Colitis.

• Produce Two Major Protein Toxins

(A &B).

• Risk Factors: –Antibiotic Exposure.

–Old Age.

Clostridium difficileClostridium difficile

Scanning electron micrograph of Scanning electron micrograph of Clostridium difficleClostridium difficle

Intestinal Smear- Close Association Intestinal Smear- Close Association of of Cl. difficileCl. difficile with Neutrophils with Neutrophils

• Infection Can Be: –Endogenous or Exogenous.

• Nosocomial Spread: Due to Spores.

LAB DIAGNOSIS:1. Demonstration of Cytotoxin in Stool.

2. Isolation of the Microorganism.

TREATMENT:–Discontinuing Treatment.

–Vancomycin.