Gram Positive Bacteria - Microbiology - Lecture Slides, Slides for Microbiology. Aliah University
jojy30 January 2013

Gram Positive Bacteria - Microbiology - Lecture Slides, Slides for Microbiology. Aliah University

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Gram Positive Bacteria, Medical Importance, Endospores, Clostridium, Perfringens, Bacillus Anthracis, Central Endospores, Clostridium Tetani, Bacillus Anthracis, Bacillus Cereus are some points from these slides of Micro...
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The Gram-Positive Bacteria

Chapter 19

The Gram-Positive Bacilli of Medical Importance


Bacillus anthracis With central endospores

Clostridium perfringens With subterminal endospores

Clostridium tetani With terminal endospores

A reminder: Some Gram- positive soil bacteria are capable of producing endospores.


• gram-positive, endospore-forming, motile rods • mostly saprobic • aerobic & catalase positive • versatile in degrading complex macromolecules • source of antibiotics • primary habitat is soil • 2 species of medical importance

Bacillus anthracis Bacillus cereus


Bacillus anthracis • large, block shaped rods • central spores that develop under all conditions

except in the living body • virulence factors – capsule & exotoxins • 3 types of anthrax

Cutaneous – spores enter through skin • black sore- eschar; least dangerous

Pulmonary –inhalation of spores – Gastrointestinal – ingested spores

• treated with penicillin or tetracycline • vaccine – toxoid 6X over 1.5 years; annual boosters • dead livestock burned/chemically decontaminated

before burial to prevent soil contamination 5

Bacillus anthracis

• Biological warfare threat. • Letter attacks of 2001

– Resulted in only 22 cases of anthrax and five deaths

– Great disruption and concern – More than 32,000 people who

may have come into contact with the letters were given prophylactic antibiotics.


Anthrax- Domestic Bioterrorism • Starting one week after the 9/11/2001 attack letters

containing weaponized anhtrax were sent to media offices and to Democratic Senators Tom Daschle and Patrick Leahy -- the two individuals expected to resist passage of the USA PATRIOT ACT.


•The attacks came in two waves of letters with Trenton, New Jersey postmarks:

•the first, with postmarks of Sepmtember 18, were sent to ABC, NBC, CBS, the New York Post, and the National Equiror at American Media Inc. •the second, with postmarks of October 9, were sent to Senators Daschle and Leahy.


Cutaneous anthrax showing the eschar

Bacillus cereus • common airborne & dustborne • grows in foods, spores survive cooking &

reheating • ingestion of toxin-containing food causes

nausea, vomiting, abdominal cramps & diarrhea; 24 hour duration

• no treatment • spores abundant in the environment



• gram-positive, spore-forming rods • anaerobic & catalase negative • over 120 species • oval or spherical spores produced only under

anaerobic conditions • synthesize organic acids & alcohols (useful for some

biotechnology application) & exotoxins • cause wound & tissue infections & food intoxications


Clostridium perfringens

• causes gas gangrene in damaged or dead tissues

• 2nd most common cause of food poisoning, worldwide

• virulence factors – toxins – alpha toxin – causes RBC rupture, edema & tissue

destruction – collagenase – hyaluronidase – DNase


12 C. perfringens


C. perfringens wound infection

Clostridium perfringens • treatment of gangrene – debridement of diseased tissue large doses of cephalosporin or penicillin hyperbaric oxygen


Hyperbaric treatment chamber

Exposure to increased oxygen levels inhibits anaerobes and speeds healing

Clostridium difficile

• normal resident of colon, in low numbers • causes antibiotic-associated colitis

– treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow

• produces entertoxins that damage intestine

• major cause of diarrhea in hospitals



Mild Severe pseudomembranous colitis

C. difficile infection. Lining of the colon as seen via a sigmoidoscope

Clostridium tetani

• common resident of soil & GI tracts of animals • causes tetanus or lockjaw, a neuromuscular

disease • spores usually enter through accidental

puncture wounds, burns, umbilical stumps, frostbite, & crushed body parts

• tetanospasmin – neurotoxin causes paralysis • vaccine booster needed every 10 years



Tetanospasmin (a potent neurotoxin). Toxin inhibits release of neurotransmitter from neurons controlling inhibition of skeletal muscle contraction

Patient with Tetanus

Figure 19.17

20 Neonatal tetanus

Clostridium botulinum

Causes 3 diseases 1. food poisoning – (an intoxication) spores are in soil,

may contaminate vegetables; improper canning does not kill spores & they germinate in the can producing botulinum toxin – toxin causes paralysis by preventing release of


2. infant botulism – caused by ingested spores that germinate in the body & release toxin

3. wound botulism – spores enter wound & cause food poisoning symptoms (although GI tract is not colonized) 21



Clostridium botulinum Botox

• In 2007, almost 4.6 million procedures were performed with FDA-approved BOTOX® Cosmetic.

• BOTOX® Cosmetic works by temporarily reducing the contractions of the muscles that cause the persistent frown lines that have develop over time.

• The benefits may last up to 4 months

• Over 11 million people have used botox

Listeria monocytogenes • non-spore-forming gram-positive • primary reservoir is soil & water • can contaminate foods & grow during refrigeration • Most cases are from contaminated dairy products,

poultry and meat • Disease is often mild/subclinical …may have fever,

diarrhea • Listerosis in immunocompromised patients, fetuses &

neonates affects brain & meninges – 20% death rate

• ampicillin & trimethoprim-sulfamethoxazole • Prevention – pasteurization & cooking


Listeria monocytogenes

• Pathogen isolated from: – 12 % of ground beef – 25-30% of

chicken/turkey carcasses – 6% of luncheon meats – also in dairy products


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