Gruesome Gram-positive BacilliThis is a featured page

  • Chapter Objectives:
    • Medically improtant gram-positive bacilli.
    • Gram-positive spore-forming bacilli.
    • Gram-positive regular non-spore-forming bacilli.
    • Gram-positive irregular non-spore-forming bacilli.
    • Actinomycetes: Filamentous bacilli.





  • Division of gram-positive bacilli


  • Medically Important Gram-Positive Bacilli
    • The organization of these bacillus is based on traditional classification of gram-stain, shape, oxygen utilization, etc. More recent work has shown that these groups often do not reflect true lineages (the most related species are not necessarily grouped together).

    • There are more rod-shaped bacteria (bacilli) that cause disease than there are cocci

  • Gram-Positive Rods

  • Endospore-formers

    Non-endospore-formers
    Bacillus
    bacillus

    Listeria
    Listeria Monocytogenes
    Clostridum
    c. tetani

    Erysipelothrix
    Erysipelothrix Rhusiopathiae



    Irregular shape and staining properties




    Non-acid-fast



    Corynebacteruim
    Corynebacterium diphtheriae



    Propionibacterium
    Chapter 19 - Microbiowiki



    Acid-fast



    Mycobacterium
    tb



    Actinomycetes



    Actinomyces
    Actinomyces Israelii



    Nocardia
    Chapter 19 - Microbiowiki


  • Gram-Positive Spore-forming Bacilli
  • Characteristic of the Genus Bacilli:
  • Endospore-forming
  • Gram-positive
  • Motile
  • Rod-shaped
  • Aerobic
  • Catalase-positive
  • Not fastidious (most are saprobes)
  • Common in soils


  • Specific Bacteria
  • Bacillus anthracis and Anthrax:

    • Chapter 20 - Microbiowiki

  • Anthrax has been know for centuries as a zootonic disease
  • Robert koch used to form his postulates(disease and bacteria)
  • Louis Pasteur demonstrated benefits of vaccination by injecting live anthrax into 25 sheep that had been vaccinated and 25 that had not been vaccinated.
  • 89 know strains, with different degrees of virulence.
  • The result of infection depend largely upon the portal of entry
    • Cutaneous anthrax: most common and least dangerousChapter 20 - Microbiowiki
      • many people expose never develop disease
      • forms large black lesions on the skin
      • enter through skin, black sore forms.

    • Pulmonary anthrax: most dangerous
      • bacilli grow in the lungs and releases exotoxins in the blood stream, these exotoxins cause clotting (thrombosis) in capillaries and shock
      • 95% mortality rate, and death can occur within a few hours
      • lethal dose is considered 10.000-20.000 spores
        Pulmonary anthrax-associated with the inhalation of airborn spores, either from animal products or from contaminated soil. Infectous dose is small 8,000-50,000 spores. The bacilli grow in the lungs and release endotoxins into the blood stream. These endotoxins cause clotting (thrombosis) in capillaries. Mortality rate is about 95%, and death can occur in only a few hours. Can be used as a bioweapon.

  • Gastrointestinal anthrax:Chapter 20 - Microbiowiki


  • ingesting spores
  • Gastrointestinal form-rare but deadly form that follows a similar course as pulmonary anthrax. It is caused by infected meat. severe diarrhea and vomiting of blood are a symptom.
  • Q: What kind of vaccine is the anthrax vaccine?


  • a. attenuated bacteria
  • b. inactivated toxin (toxoid)
  • c.recombinant
  • A: inactivated toxin (toxoid)Other Bacillus Species Involved in human disease are Bacillus cereus, spores contaminate grain (mostly grain)


  • Q: What is the primary habitat for the Bacillus species?

  • a. humans and other large primates
  • b. water
  • c. soil
  • A: soilIt can infect eyes but in most cases does not cause blindness.
  • Treated with penicillin or tetracycline

  • Chapter 19 - Microbiowiki

  • Bacillus cereus

  • Common airborne and dust borne
  • Grows in foods, spores survive cooking and reheating
  • Ingestion of toxin-containing food causes nausea, vomiting, abdominal crams and diarrhea; 24 hour duration
  • no treatment
  • Spores abundant in the environment
  • contamonate grains (mostly rice)
  • Chapter 19 - Microbiowiki

  • Clostridium
  • gram positive, spore forming rods
  • strictly anaerobic and catalase negative
  • 120 species
  • oval or spherical spores produced only under anaerobic conditions
  • synthesize organic acids, alcohols, and exotoxins
  • cause wound and tissue infections & food intoxications
  • lives in the dirt




  • Clostridium perfringens

  • Causes gas gangrene in damaged or dead tissues and causes food poisoning.
  • Almost all of us have antibodies against C. perfringens, implying ll of us have been infected with it at one time.
  • Gas Gangrene
  • Causes food poisoning
  • -Virulence factors

  • -toxins: alpha toxin-cause RBC rupture, edema, and tissue destruction
  • - Collagenase
  • - Hyaluronidase
  • - DNase
  • - Treatment of gangrene- debridement of disease tissue
  • - large doses of cephalosporin or penicillin
  • - hyperbaric oxygen


  • gas gangrene



  • Maggot Therapy:
  • The intentional application of dressing live fly larvae inside a wound to heal it. This technique was widely used in the 16th
  • century and in WWI. It is now making a comeback due to antibiotic resistance. This therapy was sanctioned (after 20 years of research) in November of 2004 by the U.S. government as a safe wound treatment/therapy. Dr. Ronald Sherman of the University of California, Irvine is the only licensed physician able to breed maggots. He says there are 3 primary actions of maggot therapy:
  • 1. "Maggots clean dead tissue by liquefying it."
  • 2. "The maggot saliva disinfects the wound by killing the germs."
  • 3. "Maggot therapy stimulates wound healing causing healthy tissue to grow faster."

  • Process of cultivating a maggot:
  • The eggs are put in chemical disinfectants and transferred into steril bottles, in which the eggs will hatch in 2 days. They are ready to use as soon as they hatch.


  • Clostridium difficile
  • Normal resident of the colon in low numbers
  • Can be difficult to treat because of its resistance to antibiotics and as well as physiologic factors such as spore forming and protective effects of the pseudomembrane.
  • Overgrowth of C diff leads to pseudomembranous colitis
  • Produces entertoxins that damage the intestine
  • Major cause of diarrhea in hospitals
  • treated with specific antiobiotics such as vancomycin and montronidazole


  • Clostridium tetani:
  • C. tetani is a rod-shaped, endospore-forming, anaerobic soil bacterium responsible for an estimated 200 cases of tetanus (spastic paralysis) every year in the U.S. and an additional 350,000 worldwide. The organism is found in soil, animal feces and, occasionally, human feces. Spores are often deposited in dead (oxygen-free) tissue through a wound, burn, or ulcer where there is an anaerobic enviroment. The lesion of infection often goes unnoticed allowing spores to germinate and spread long before treatment can be obtained.Growing cells release tetanospasmin which is a potent neurotoxin, This neurotoxin inhibits the release of a neurotransmitter that normally inhibits muscular contraction.The result is uncontrollable muscle contraction. Death is caused by paralysis of the respiratory muscles.
  • Treatment and prevention of Tetanus-
  • Get vaccinated against tetanus toxin


  • Clostridium botulinum:
  • This bacteria causes botulism poisoning from improperly preserved food or contaminated food that is left out for a long time. The name comes from the Latin word for "sausage," not due to the shape of the bacteria but because historically the poisoning were commonly associated with poorly-prepared sausages. In home canning, some foods such as fruit or tomatoes can be canned with a "hot water bath" because boiling kills the vegetative bacteria, and the acidity of the food prevents C. botulinum endospores from germinating. However, if a family wants to can their own beans, meats, or other "low acid" food a pressure cooker must be used to increase the processing temperature to the point where
  • C. botulinum endospores are destroyed. Commercial canning procedures are designed specifically to kill C. botulinum endospores. If a person does get sick with botulism poisoning, the treatment consists of antitoxin administration and artificial ventilation. If initiated on time these are quite effective, though a person may have to be on artificial ventilation for several weeks to months.

  • Botulism toxin is the most toxic substance known to man. 10 g (the weight of two U.S. nickels) is sufficient to kill the population of Los Angeles, and less than half a kilogram could theoretically kill every human on the planet (in comparison, it would take over 350,000 kilograms of the rat poison strychnine to accomplish the same thing). Happily it is not considered useful for chemical warfare because it is difficult to grow the bacteria and isolate the toxin, plus the toxin degrades quickly when exposed to air.

  • The botulism toxin inhibits muscular contraction by blocking acetylcholine transmission at the neuromuscular synapse. The toxin has been isolated and used for medical and cosmetic purposes. The FDA approved the use of "Botox" to treat strabismus ("wandering eye") and facial spasms in 1989, and approved its use cosmetically in 2002. There are ongoing studies for its use with migraines, asthma, and many other conditions. One vial of Botox contains far less than a lethal dose of the toxin.

  • Q: How does botulism affect the body?
  • a. destroys the liver
  • b. Botox destroys the tissues
  • c. block acetylcholine transmission
  • d. destroys nerves
  • A. block acetlycholine transmission


  • Gram positive regular non-spore-forming bacilli:
  • These bacilli are considered regular because they stain uniformly and do not assume pleomorphic shapes.

  • Listeria monocytogenes:
  • Chapter 19 - MicrobiowikiChapter 19 - Microbiowiki

  • Listeria monocytogenes is the agent of listeriosis, a serious infection caused by eating food contaminated with the bacteria. Listeriosis has been recognized as an important public health problem in the United States. The disease affects primarily pregnant women, newborns, and adults with weakened immune systems. Listeria monocytogenes is presumably ingested with raw, contaminated food.(usually dairy products) An invasion secreted by the pathogenic bacteria enables the listeriae to penetrate host cells of the epithelial lining. The bacterium is widely distributed so this event may occur frequently.
  • Normally, the immune system eliminates the infection before it spreads.
  • Microscopically, Listeria species appear as small, Gram-positive rods, which are sometimes arranged in short chains.

  • tumbling motility, with one to four flagella
  • do not produce capsules
  • non fastidious and resistent to coldn heat, salt, pH extremes, and bile.
  • Replicates in the cytoplasm of a host cell
Listeria Monocytogenes
  1. ranges in morphology from coccobacilli to long filaments in palisades formation
  2. cells show tumbling with one to four flagella and do not produce capsules or spores
  3. Listeria is not fastidious and is resistant to cold, heat, salt, pH extremes, and bile


  • ranges in morphology from coccobaccilli to long filaments in palisades formation


  • Erysipelothrix rhusiopathiae:

  • Gram Positive Rod widely distributed in animals.
  • Primary resevoir is tonsils of healthy pigs. It is also a normal flora of other vertebrates.
  • Causes epidemic of swineerysipelas and sporadic infections in other domestic and wild animals.
  • The common entry way into a human is through a scratch while dealing with an infected animal. Produces a disease know as erysipeloid in humans. (Swollen, inflammed, dark red lesions that burn and itch)
  • Can be treated with antibiotics.

  • Gram Posotive irregular non spore forming bacilli:
  • tend to be pleomorphic and stain unevenly.
  • Corynebacterium, Mycobacterium, and Nocardia have the greatest clinical significance.
  • -produce catalase
  • -posses mycolic acids and a unique type of peptidoglycan call wall
  • Corynebacterium diphtheriae:
  • Chapter 19 - MicrobiowikiChapter 19 - MicrobiowikiDiphtheria
  • C. diphtheriae is an aerobic gram-positive bacillus.Toxin production (toxigenicity) occurs only when the bacillus is itself infected (lysogenized) by a specific virus (bacteriophage) carrying the genetic information for the toxin (tox gene). Only toxigenic strains can cause severe disease.
  • There are three biotypes of C. diphtheriae — gravis, intermedius, and mitis. The most severe disease is associated with the gravis biotype, but any strain may produce toxin. Susceptible persons may acquire toxigenic diphtheria bacilli in the nasopharynx. The organism produces a toxin that inhibits cellular protein synthesis and is responsible for local tissue destruction and membrane formation. The toxin produced at the site of the membrane is absorbed into the bloodstream and distributed to the tissues of the body. The toxin is responsible for the major complications of myocarditis and neuritis and can also cause low platelet counts (thrombocytopenia) and protein in the urine (proteinuria). A pseudomembrane can develop, which can block the airway and cause asphyxiation.
  • Treatment and prevention
  • Vaccination
  • treatment with antitoxin, heart medication, tracheostomy, and antibiotics
  • Propionibacterium:
  • This genus in aerotolerant or anaerobic and nontoxigenic.
  • Most prominent is
  • P.Acnes: common resident of the pilosecaceous glands of human skin. Produces acne vulgaris lesions common in adolescence. complex syndrome influenced by genetic and hormonal factors .


  • Mycobacteria: Acid Fast Bacilli-Chapter 20 - Microbiowiki
  • Distinguished by its complex layered structure composed of high-molecular-weight mycolic acids and waxes.
  • high lipid content is responsible for the resistance of the group to drying, acids, and various germicides.
  • Long slender (straight or curved) rods....tend to be branching.
  • Usually contain granule and vacuoles
  • No capsules, flagella or spores
  • Strict aerobes
  • Many are free living in soil and water...highly significant human pathogens.
  • Mycobacterium tuberculosis:
  • Unlike many bacteria tuberculosis produces no exotoxins or enzymes that contribut to infectiousness.
  • Contains complex waxes and cord factors that prevent it from being destroyed.
  • -transmitted almost exclusively by fine droplets of respiratory mucus suspended in the air.
  • -very resistant and can survive for 8 months in fine aerosol particles.
  • PRIMARY TB
  • -min. infectious dose for lung infection is around 10 cells.
  • -phagocytosed by alveolar macrophages and multiply intracellularly. (usually asymptomatic during this period)
  • SECONDARY REACTIVATION TB
  • -live bacilli remain dormant and become reactivated weeks, months, or years after the infected recovers from the primary infection.
  • -voilent coughing, greenish or bloody sputum, fever, anorexia, weight loss, extreme fatigue, and chest pain. (gradual wasting of the body)
  • EXTRAPULMONARY TB
  • -during secondary TB the bacilli spread to other sites; Most commonly the regional lymph nodes, kidneys, long bones, genital tract, brain, and meninges.
  • -renal TB results in necrosis and scarring of the renal medulla and the pelvis. Causes painful urination and the presence of blood in urine.
  • Genital TB often affects reproductive function in both sexes.
  • -TB of bone and joints is common. Infects the spine and results n abnormal curvature of the thoracic region or lumbar region.
  • -tubercular menigitis is the result of an active brain lesion seeding bacilli into the meninges. Causes mental retardation, blindness, and deafness.
  • Mantouz test: involves local injection of purified protein derivative into the forearm to produce an immediate small bulb. After 48-72 hrs the site is observed for a red wheal called an induration, which is measured and classified.
  • Treatment of TB involves administering drugs for a sufficient period of time to kill the bacilli (usually 6-24 months)
  • A vaccine based on the BCG strain of m. bovis is often given to children in countries that have high rates of tb.

  • Q: What is the virulence factor in Mycobacterium tuberculosis that prevents the organisms' destruction by lysosomes within macrophages?
  • a. Cord factor
  • b. Exotoxin
  • c. M protein
  • A: Cord Factor

  • Mycobacterium Leprae (leprosy):
  • M. Leprae is a strict parasite that has not been grown in artificial media or human tissue cultures. It is also the slowest growing of all species.
  • Leprosy is a chronic, progressive disease of the skin and nerves.
  • Most people who come in contact with this disease will not contract it.
  • -The earliest signs of leprosy appear on this skin of the trunk and extremities.
  • tuberculoid leprosyTuberculoid leprosy:
  • -characterized by shallow skin lesions containing very few bacilli. Causes nerve damages resulting is loss of pain reception.
  • -easier to treat than other forms
  • LleprosyChapter 20 - MicrobiowikiChapter 19 - Microbiowiki
  • epromatous leprosy:
  • -responsible for disfigurations commonly associated with the disease.
  • - Advanced cases causes loss of sensitivity that predisposes the patient to trauma and mutilation, secondary infections, blindness, and kidney failure.
  • In many cases there is a loss of fingers and toes.
  • Leprosy can be controlled by drugs....multi drug therapy is necessary due to resistant strains.
  • infections by non- TB Mycobacteria


  • Disseminated Mycobacterial infection in AIDS:
  • Mycobacterium avium complex frequently causes secondary infections in AIDS patients.
  • Enters through the respiratory tract, and multiply rapidly. Treatment is many months or even years of drug therapy.
  • Misc. Mycobacterial Infections:
  • - M. marinum is a hazard in swiming pools. Localized nodule on the elbows, knees, toes, or fingers which then enlarges, ulcerates, and drains.
  • - M. Scrofulaceum causes an infection of the cervical lymph nodes in children
  • - M. Paratuberculosis is in strong association with Crohn disease. found in cows milk.


  • Actinomycetes: Filamentous Bacilli:
  • Non- Motile filamentous rods that may be acid fast. Prodce granulomatous diseases. Main generas involved in human disease are ACTINOMYCES and NOCARDIA
  • ACTINOMYCES:
  • an endogenous infection of the cervicofacial, thoracic, or abdominal regions.
  • Cervicofacial form is caused by a tooth extraction, and poor oral hygeine. A. Israelii enters a damaged area of the oral mucous membrane and begins to multiply.
  • NOCARDIOSIS:
  • a genus of bacilli widely distributed in the soil. N.brasiliensis is a primary pulmonary pathogen and
  • N. asteroides and N. caviae are opportunists.
  • Pulmonary nocardiosis is a form of bacterial pneumonia with pathology and symptoms similar to TB. The lung develops abcesses and nodules.



  • flashcards for this chapter are at www.flashcardexchange.com under kevin young's micro chapter 19




  • Content that was accidentally placed on Ch 20 page but belongs here--please integrate it into this chapter! ~K



  • Questions: Q&A Page~~Home Page~~Top of Page

  • 1. How do bacteria divide?
  • a. Mitosis
  • b. Binary Fission
  • c. Meiosis
  • d. Microbial Fission

  • 2. How many spores do you need to inhale of anthrax to become fatal?
  • a. 8,000 - 50,000
  • b. 100,000 - 200,000
  • c. 1,000 - 5,000
  • d. 150 - 200

  • 3. Which is the most common form of anthrax, and the least dangerous?
  • a. Pulmonary anthrax
  • b. Cutaneous anthrax
  • c. Gastrointestinal anthrax

  • d. Clostridium anthrax

  • 4.What bacteria is associated with antibiotic-associated colitis that causes major diarrhea is hospitals?
  • a. Bacillus cereus
  • b. Bacillus anthracis
  • c. Clostridium perfringens
  • d. Clostridioum difficile

  • 5. What group of people are most affected by Corynebacterium diptheriae?
  • a. drug users
  • b. homeless
  • c. non immunized children
  • d. Native Americans

  • 6. Pseudomembrane from Corynebacterium diptheriae cause
  • a. A greenish gray film in the pharynx
  • b. forms in the airways
  • c. causes asphyxiation
  • d. all of the above

  • 7. What treatments are used for Corynebacterium diptheriae
  • a. antitoxins derived from horses
  • b. antitoxins derived from pigs
  • c. antibiotics
  • d. a & c

  • 8. Clostridium perfringens causes
  • a. severe diarrhea
  • b. food poisoning
  • c. capillaries to leak
  • d. a & b

  • 9. What are the virulence factors of Bacillus anthracis?
  • a. catalase
  • b. cytokinase
  • c. polypeptide capsule and endotoxins
  • d. phagocytosis

  • 10. All are characteristics of the genus Bacillus except:
  • a. They are endospore forming
  • b. They are catalase negative
  • c. They are gram-positive
  • d. They are rod shaped

  • 11. The species perfringens, difficile, tetani, and botulinum all belong to the genus:
  • a. clostridium
  • b. bacillus
  • c. propionibacterium
  • d. listeria

  • 12. All of these are possible methods of Anthrax control except:
  • a. treatment with penicillin and other antibiotics
  • b. getting an anthrax vaccine
  • c. gas-sterilization of imported animal hides
  • d. treatment with antitoxin from horses, mechanical respirator, and cardiac support

  • 13. The organization of medically important gram-positive bacilli is based on a traditional classification of:
  • a. gram stain
  • b. shape
  • c. oxygen utilization
  • d. all of the above

  • 16. This infection requires dead tissue and exposure to spores and spreads by bacteria releasing exotoxins that kill adjacent tissue.
  • a. botulism
  • b. tetanus
  • c. gas gangrene
  • c. antibiotic-associated colitis

  • 17. A cosmetic use for botulism includes:
  • a. botox for looks
  • b.treatment for muscle spasms
  • c. treatment of migraines
  • d. all of the above

  • 18. A large black lesion forms where you had a little cut on your arm. You can assume that:
  • a. you have been infected by Bacillus anthracis cutaneously
  • b. you have been infected by Clostridium difficile and can expect to start having serious diarrhea
  • c. you have been infected by pulmonary anthrax
  • d. you have ingested something bad and now have botulinum toxin in your body

  • 19.Formation of pseudomembrane in the back of the throat is caused by an infectio with:
  • a. Corynebacterium
  • b. Listeria
  • c. Mycobacterium
  • d. Streptococcus


  • In class, we were suggested to make a list of all food poisoning microbes:
  • Staphylococcus Aureus: produces an exotoxin (entertoxin as well) that inflames intestines. It takes 2-6 hours to activate and can last up to 48 hours. Found in pies, dairy, potato salad, and etc. Symptoms: Acute abdominal pain, projectile vomiting, nausea, and diarrhea. To prevent: refrigeration and personal cleanliness.
  • Botulism: produces an exotoxin (neurotoxin as well) that inhibits acetylcholine. It takes 18-36 hours to activate and can lead to death in 4-8 days if not treated. Its found in non acidic home canned foods such as green beans, corn, green peppers, etc. Symptoms: Headache, dizziness, difficulty in swallowing, and respiratory paralysis. To prevent: boil canned food for 10-15 minutes to inactivate the toxin.
  • Salmonella: S. Typhi not included. produces endotoxins. It takes 12-24 hours to acitvate and can take anywhere from 2-5 days to recover. Its found in improperly prepared foods such as meets, dairy, and especially eggs. Symptoms: Fever, nausea, vomiting, acute abdominal pain, and diarrhea with blood and mucus. To prevent: refrigerate foods and have personal cleanliness.
  • Shigella: bacteria dysentary. Can be found in infected foods. It is less invasive than Salmonella but can persist longer in stored foods. Symptoms: Fever, nausea, vomiting, acute abdominal pain, and diarrhea with blood and mucous. It causes sever dehydration in infants.
  • Vibrio Cholera: It is the causitive agent of cholera. The toxin produces Cholergen. It can be found in Shellfish in the Gulf Coast States and in stagnant brown water. Symptoms: It causes shredding of the lining in the small intestines. This causes small white flecks resembling rice grains to be passed in the feces "rice water stools."
  • Giardia Lamlia: It is a protozoal parasite. It can be found in contamited water from streams.Symptoms: It causes prolonged frothy diahrrea and malabsorption. The diarrhea is not bloody because the parasite does not invade the cells.
  • Enteroviruses: Rotavirus- major cause of diarrhea and dehydration in infants and young children. Poliomyelitis- caused by one of the polio viruses. Can range from asymptomatic to paralytic. Transmitter through fecal comtamination in foods and some oophayngeal secretion.
  • Amoebic Dysentery: Caused by Entamoeba Histolytica. Infected through the ingestion of cysts in food or water contaminated with fecal matter. Once in the intestine, the cysts rupture and release trophozites in the colon that feed on the normal flora of the colon. Symptoms: bloody stools and diarrhea.
  • Campylobacter Jejuni: Bacterial gastroenteritis, transmitted by bevverages and food, erach mucosa at the last segment of small intestine near colon; adhere, burrow through mucus and multiply. Symptoms: Headahce, fever, abdominal pain, bloody or watery diarrhea, heat labile enterotoxin
  • And of course the Helminths: Pinworms- ingested by feces in food, but mostly sandboxes and such. Creates a perianal nocturnal itch and insomnia. Ascariasis- ingestion from eggs of dog, cat feces. It has the scary life cycle (cough up larva and swallow). Trichinosis- round wor up to 1 mm long. Ingestion of encysted larbae in poorly cooked pork, bear, etc. Symptoms: ingestional discomfort, fever, muscle pain, chills, weakness. Can lead to respiratory and myocardial weakness. Tapeworm- Flat worm from 2-6 meters long. ingestion of encysted larva in poorly cooked beef, pork, or fish. Symptoms: usuall mild... diarrhea, epigastric pain, and weith loss.





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