Ch. 19 - The Gram-Positive Bacilli of Medical Importance

What are the 3 types of anthrax?

- Cutaneous: spores enter through skin, black sore (eschar), least dangerous - Pulmonary: inhalation of spores - Gastrointestinal: ingested spores

Symptoms of Botulism

- Double or blurred vision - difficulty swallowing - neuromuscular symptoms

Please select all correct characteristics of Actinomyces israelii. Gram-positive Possesses large flagella Macroscopic appearance similar to molds Produces endospores Filamentous rather than regular-shaped cell

- Gram-positive - Macroscopic appearance similar to molds - Filamentous rather than regular-shaped cell

Please select the possible transmission methods for botulism. - Ingestion of contaminated food - Aerosols - Contaminated soil or dust gets into a wound - Bite of insect vector - Sexual intercourse

- Ingestion of contaminated food - Contaminated soil or dust gets into a wound

Characteristics of Corynebacterium diptheriae

- Irregular non-spore-forming Bacilli - pleomorphic, granules, palisades arrangement • Reservoir: healthy human carriers; potential for diphtheria is always present • Most cases occur in non-immunized children living in crowded, unsanitary conditions • Acquired via respiratory droplets from carriers or actively infected individuals

The presence of Corynebacterium bacteria in the nasal passages and throat is not necessarily an indicator of diphtheria. Please choose all answers that relate to this statement. - Nonpathogenic Corynebacterium species are commonly found in these areas in all people. - It depends on the health of the person carrying the bacteria; healthy people do not get diphtheria. - A person can harbor C. diphtheriae without actually having diphtheria. - A person having less than 100 cells of C. diphtheria will not have the disease, whereas more than 100 cells will cause the disease.

- Nonpathogenic Corynebacterium species are commonly found in these areas in all people. - A person can harbor C. diphtheriae without actually having diphtheria.

Diseases of Listeria monocytogenes

- Often mild or subclinical in normal adults - More serious for elderly or immunocompromised - VERY SERIOUS for pregnant women: will be asymptomatic or resemble a cold, bacteria crosses the placenta and infects the fetus, results in still birth or infection of the brain and meninges of neonates, 20% death rate

What is the difference between regular and irregular non-spore-forming bacilli?

- Regular: stain uniformly and do not assume pleomorphic shapes - Irregular: don't stain uniformly and have pleomorphic shapes

Lepromatous leprosy

- a deeply nodular infection that causes severe disfigurement of the face and extremities - widespread disemination

Tuberculoid leprosy

- assymmetrical, shallow lesions, damage nerves - results in local loss of pain reception

General Characteristic of the Genus Bacillis

- gram-positive, endospore-forming, motile rods - mostly saprobic aerobic and catalase positive versatile in degrading complex macromolecules - source of antibiotics - primary habitat = soil

What are predisposing factors of tuberculosis?

- inadequate nutrition (homeless, IV-drug users) - debilitated or immunocompromised - poor access to medical care, lung damage, and genetics (homeless)

What does Mycobacterium leprae infect?

- incubation from 2-5 years - if untreated, bacilli grow slowly in the skin macrophages and Schwann cells of peripheral nerves - coller body parts: fingers, toes, nose, ears

Pathology of gangrene

- not highly invasive, requires damaged and dead tissue and anaerobic condition - Conditions stimulate spore germination, vegetative growth and release of exotoxins, and other virulence factors - Myonecrosis - fermentation of muscle carbohydrates results in the formation of gas and further tissue destruction

How is Bacillus anthracis treated?

- penicillin, tetracycline, or ciproflozacin - vaccines

Characteristics of Clostridium botulinum

- spore-forming anaerobe -commonly inhabits soil and wate • Spores are present on food when gathered and processed • If reliable temperature and pressure are not achieved air will be evacuated but spores will remain • Anaerobic conditions favor spore germination and vegetative growth • Potent toxin, botulin, is released

Gas Gangrene

- spores found in soil, human,skin, intestine, and vagina - predisposing factors: surgical incisions, compounds fractures, diabetic ulcers, septic abortions, puncture wounds, gunshot wounds

What are the clinical stages of tuberculosis infection and disease progression?

1. Exposure to TB droplets 2. Inhaled into lungs 3. Lung macrophages engulf bacilli, infection occurs in 80-90% of cases 4. Primary TB disease with tubercles, symptoms occur in 5-10% of cases within 2 years 5. Latency; bacilli go dormant in lungs; carrier state without symptoms may last for many years 6. Recurrent disease; tubercles break down; bacilli are released into lung cavities and circulation 7. Disease spreads to extrapulmonary sites such as kidney, bones, brain with severe morbidity.

Order of events of the progression of tuberculosis

1. Inhalation of bacteria 2. Bacteria are localized within lung tissue by phagocytic macrophages 3. Immune cells migrate to the area and surround the macrophages and bacteria 4. Latent infection 5. Bacteria migrate out of tubercles into healthy lung tissue 6. Wasting of body

How is TB diagnosed?

1. Invivo or tuberculin testing [Mantoux test - local intradermal injection of purified protein derivative (PPD) ] 2. X-rays 3. Acid-fast staining: direct identification of bacilli in specimen 4. Cultural isolation and biochemical testing

What are the 2 stages of Corynebacterium diptheriae?

1. Local infection of upper respiratory tract - Inflammation - Sore throat, nausea, vomiting - swollen lymph nodes - Formation of a pseudomembrane (made up of bacteria, dead epithelial cells, dead white blood cells; can cause asphyxiation) 2. Diptherotoxin production - Leads to toxemia (toxins in the blood) - Target organs: primarily heart and nerves

Order of events in a tetanus infection

1. Necrotic tissue causes anaerobic conditions 2. Germination of spores 3. Production of tetanospasmin toxin 4. Excess skeletal muscle contraction 5. Respiratory muscles go into spastic, sustained contractions

Estimated ________ of world population and 15 million in US carry tubercle bacillus

1/3

For decades, the prevalence of TB was decliing; however, in the US, increase were seen in the ___________ due to the spread of ______.

1980s; HIV

Clinical tuberculosis divided into ______ phases:

3

In A-B toxins, A is the toxic part B is the toxic part Both A and B are toxic Neither A or B are toxic B is toxic only after A has allowed it to enter the cell

A is the toxic part

Please choose the normal biota organism that causes necrotizing lung disease, abdominal infections, and uterine infections. Propionibacterium acnes Mycobacterium avium Lactobacillus fermentans Actinomyces israelii Bacillus cereus

Actinomyces israelii

How does the toxin enter the cell? - After B binds to host cell receptors, A enters the host cell alone by endocytosis. - After B binds to host cell receptors, both A and B enter the host cell by endocytosis. - After A binds to host cell receptors, A enters the host cell by endocytosis. - After both A and B bind to host cell receptors, both A and B enter by endocytosis.

After B binds to host cell receptors, both A and B enter the host cell by endocytosis.

Please choose the correct statement comparing Bacillus cereus to Clostridium perfringens. Both bacteria are gram-positive rods. Both bacterial infections are mediated by ingested endospores. Similar foods can be the carrier material for the endospores of both organisms. The symptoms of the two diseases are similar. All of these are correct statements.

All of these

Please select the answer that describes the state of diagnostics for tuberculosis infections. Culturing and identifying the bacterium is very tedious and time-consuming. Genetic tests such as PCR and gene probes give accurate, fast molecular identification of the organism. The X-ray may not show small tubercles. The skin test is not a definitive test because it does not identify if the person has a present infection. All of these statements are true.

All of these

After the A-B toxin enters the cell, - an alkaline pH causes A and B to separate - A is removed by exocytosis - B is removed by exocytosis - B causes toxicity - both A and B prevent protein synthesis

B is removed by exocytosis

What are the 2 species of Bacillusof medical importance?

Bacillus anthracis and Bacillus cereus

Please choose the correct mechanism of botulinum toxin. Destroys the enzyme cholinesterase at the neuromuscular junction causing constant muscle contraction Blocks the release of acetylcholine neurotransmitter from the axon foot vesicles so muscle cannot get message to contract Inactivates brain neurotransmitters, such as dopamine and serotonin Damages motor neurons in the spinal cord so messages from brain cannot get to muscles for contraction

Blocks the release of acetylcholine neurotransmitter from the axon foot vesicles so muscle cannot get message to contract

Clostridium botulinum causes ___________.

Botulinum food poisoning

Please select the explanation for why cancer patients have a higher risk of getting more serious listeriosis infections. When chemotherapeutic medications are given to a patient, there is an increased possibility that those drugs are infected with bacteria. The radiation that cancer patients receive makes them more susceptible to bacterial infections. Cancer patients are immunosuppressed, and this increases the severity of this disease. Since cancer patients have a variety of home health care personnel as well as interaction with clinical professionals, they come in contact with the bacteria more often.

Cancer patients are immunosuppressed, and this increases the severity of this disease.

A patient has a deep wound infection, and the specimen taken for microbial identification in the lab is a tissue sample from within the wound. Please choose the most likely organism causing the infection. Clostridium Bacillus E. coli Mycobacterium tuberculosis Poliovirus

Clostridium

____________________ is the most frequent clostridia involved in soft tissue and wound infections (Myonecrosis)

Clostridium perfringens

Please select the genera that are considered to be irregular gram-positive bacilli. Corynebacterium Propionibacterium Clostridium Mycobacterium Actinomyces

Corynebacterium, Propionibacterium, Mycobacterium, Actinomyces

T/F. A person with an active tuberculosis infection is placed on a single antibiotic because tuberculosis can be treated as well as any other respiratory infection.

FALSE

T/F. All A toxins work the same way.

FALSE

T/F. The best treatment for botulism is the botox vaccine given along with the other infant vaccines.

FALSE

Botulism is characterized by:

Flaccid Paralysis

Clostridium can cause:

Gangrene, Tetanus, Botulism

Clostridium perfringens causes ___________.

Gas gangrene

Please choose the reason why gas gangrene infections can be treated with oxygen therapy successfully. - The oxygen reacts with water within the cell producing hydrogen peroxide, which kills the bacterial cells. - The oxygen, delivered in low concentration, creates an anaerobic environment in which the Clostridium does poorly. - Oxygen poisons the clostridial cells. - The oxygen delivery produces a radioisotope of oxygen within the tissue, destroying the necrotic tissue. - High pressure oxygen is delivered to the infected tissue, creating an unfavorable habitat for anaerobic Clostridium.

High pressure oxygen is delivered to the infected tissue, creating an unfavorable habitat for anaerobic Clostridium.

What is botulism?

Intoxication associated with inadequate food preservation

Mycobacterium leprae causes _____________.

Leprosy Bacillus

Gangrene is characterized by :

Muscle Necrosisz

Tuberculosis is a respiratory infection caused by a member of genus ______________.

Mycobacterium

Tetanus is characterized by:

Spastic Paralysis

T/F. Clostridium botulinum endospores, when ingested by newborns and babies, can germinate and grow within the intestinal tract, whereas in adults, this is not the case.

TRUE

T/F. Clostridium perfringens infection is a leading cause of myonecrosis.

TRUE

T/F. In Corynebacterium diphtheriae, the A toxin produced carries out the transfer of ADP-ribose to elongation factor 2, inhibiting protein synthesis

TRUE

T/F. It is the exotoxin of Corynebacterium diphtheriae that is the common cause of death in the infected patient.

TRUE

Clostridium tetani causes _________________

Tetanus

Why is antibiotic use a common cause of Clostridium difficile infections? - The antibiotic wipes out the normal bacteria in the gut, allowing C. difficile to overgrow. - C. difficile requires antibiotics for its own metabolism, and therefore grows best in its presence. - Antibiotics are perishable drugs that are easily contaminated with C. difficile spores. - Antibiotics are usually given to immunocompromised patients ,and their low T cell count is favorable for C. difficile infection.

The antibiotic wipes out the normal bacteria in the gut, allowing C. difficile to overgrow.

Please select the statement that best explains why leprosy is mainly a skin disease. The bacterium M. leprae grows best at the cooler temperature of 30 degrees C. The bacterium is too large to enter the bloodstream, so it cannot be carried throughout the body. The bacterium uses keratin, found in the epidermis, as a nutrient source. The bacterium grows best in stratified squamous epithelial tissues.

The bacterium M. leprae grows best at the cooler temperature of 30 degrees C.

Please select the answer which describes why pulmonary anthrax is more deadly than cutaneous anthrax. The toxins from the bacteria destroy vital organs of the body. The destruction of macrophages reduces host resistance. The capsules around the bacterial cells reduce the effectiveness of phagocytosis. The bacterial cells attach permanently to host cells, making them immobile.

The destruction of macrophages reduces host resistance.

Please select the statement that best explains why leprosy patients have deformed extremities. - The nerves, damaged by the bacterium, cannot send sensory information to the brain, so the person does not even know when tissue damage has been done. - The bacterium eats away the tissues in the extremities first, leaving stumps where fingers and toes once were. - The person's immune system, attacking the tissues containing the bacterium, actually damages the host's tissues. - The drugs used to treat leprosy are extremely toxic and damage host tissues. - This bacterium is a thermophile, meaning that it thrives best in the colder extremities and damages these tissues.

The nerves, damaged by the bacterium, cannot send sensory information to the brain, so the person does not even know when tissue damage has been done.

The patient is a 34 year-old man, who is complaining of night sweats, weight loss, diarrhea, and fatigue. He is diagnosed with Mycobacterium avium complex. Please select the explanation that describes why this patient might have this disease. The patient picked up the organisms in large numbers from someone who had the disease. The patient has handled animals carrying the bacterium. The patient has just recovered from the flu and now has a secondary infection. The patient has AIDS.

The patient has AIDS.

What are the 2 forms of Leprosy?

Tuberculoiid and Lepromatous

Please select the correct explanation for why Erysipelothrix rhusiopathiae is considered to be an occupational pathogen. Workers handling animals or their wastes are at risk for transmission. Workers in office cubicles, in close proximity to each other, can transmit the bacterium via aerosols. Healthcare workers are at the greatest risk of contracting this organism from their patients. Flight attendants are at the highest risk of contracting the organisms because of recycled air in the planes.

Workers handling animals or their wastes are at risk for transmission.

How is Tuberculosis transmitted?

airborne respiratory droplet

Bacillus species commonly produce _________, which have been an important contribution to human health.

antibiotics

Please select the mammal population that receives the greatest percentage of anthrax vaccine because it is at the highest risk of getting the disease. Travelers Dogs Cattle Military personnel Veterinarians

cattle

These concerning infections have led to new control measures, including programs to ensure compliance in drug therapy such as ____________________ therapy

directly observed

Rates are once again declining, but a new concern has been the increase in ________________ strains of M. tuberculosis.

drug-resistant

This pulmonary infection is diagnosed by testing the skin for ________________ to a bacterial protein, using chest X-rays to observe tubercles in the lungs, or _____________ staining of sputum specimens.

hypersensitivty; acid-fast

infant botulism is caused by:

ingested spores that germinate and release toxin; flaccid paralysis

The majority of TB cases restricted to ___________.

lungs

MDR-TB refers to ___________________ tuberculosis, and XDR-TB stands for _____________________________________ tuberculosis

multidrug resistant; extensively drug resistant

Wound botulism is caused by:

spores enter wound and cause food poisoning symptoms

Pulmonary nocardiosis has symptoms that are very similar to ________.

tuberculosis

How is TB treated?

• 6-24 months of at least 2 drugs from a list of 11 • One pill regimen called Rifater (isoniazid, rifampin, pyrazinamide) • Vaccine based on attenuated bacilli Calmet-Guerin strain of M. bovis used in other countries

How is Corynebacterium treated?

• Antitoxin • Penicillin or erythromycin • Prevented by toxoid vaccine series and boosters

Pathogenesis of Botulism

• Botulin toxin - carried to neuromuscular junctions - Blocks release of acetylcholine - muscle cannot contract

How is leprosy diagnosed?

• Combination of symptomology, microscopic examination of lesions, and patient history • Numbness in hands and feet, loss of heat and cold sensitivity, muscle weakness, thickened earlobes, chronic stuffy nose • Detection of acid-fast bacilli in skin lesions, nasal discharges, and tissue samples

Characteristics of Clostridium tetani

• Common resident of soil and GI tracts of animals • Causes tetanus or lockjaw, a neuromuscular disease • Most commonly among geriatric patients and IV drug abusers; neonates in developing countries

Diagnosis and control of Listeria monocytogenes

• Culture requires lengthy cold enrichment process • Rapid diagnostic tests using ELISA, immunofluorescence, and DNA analysis • Ampicillin and trimethoprim/ sulfamethoxazole • Prevention - pasteurization and cooking

How is botulism treated?

• Determine presence of toxin in food, intestinal contents or feces • Administer antitoxin; cardiac and respiratory support • Infectious botulism treated with penicillin • Practice proper methods of preserving and handling canned foods; addition of preservatives

Disseminated/ Extrapulminary TB

• During secondary TB, - bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain, and meninges - These complications are grave

Epidemiology and Transmission of Leprosy

• Endemic regions throughout the world • Mechanism of transmission is not fully verified • Not highly virulent; appears that health and living conditions influence susceptibility and the course of the disease • May be associated with specific genetic marker

Characteristics of Mycobacteria: Acid-Fast Bacilli

• Gram-positive irregular bacilli • Acid-fast staining • Strict aerobes • Produce catalase • Possess mycolic acids and a unique type of peptidoglycan • Do not form capsules, flagella, or spores • Grow VERY slowly

Characteristics of the Genus Clostridium

• Gram-positive, spore-forming rods • Anaerobic and catalase negative • 120 species • Oval or spherical spores produced only under anaerobic conditions • Synthesize organic acids, alcohols, and exotoxins • Cause wound infections, tissue infections, and food intoxications

Secondary TB

• If patient doesn't recover from primary tuberculosis, reactivation of bacilli can occur • Tubercles expand and drain into the bronchial tubes and upper respiratory tract • Gradually the patient experiences more severe symptoms - Violent coughing, greenish or bloody sputum, fever, anorexia, weight loss, fatigue • Untreated, 60% mortality rate

How is gangrene treated?

• Immediate cleansing of dirty wounds, deep wounds, compound fractures, and infected incisions • Debridement of disease tissue • Large doses of cephalosporin or penicillin • Hyperbaric oxygen therapy • No vaccines available

Primary TB

• Infectious dose = 10 cells • Phagocytized by alveolar macrophages • multiply intracellularly • After 3-4 weeks: - immune system attacks - forms tubercles and granulomas consisting of a central core containing bacilli surrounded by WBCs - tubercle • If center of tubercle breaks down into necrotic caseous lesions, they gradually heal by calcification

Characteristics of Bacillus anthracis

• Large, block-shaped rods - "box-car" • Central spores that develop under all conditions except in the living body • Virulence factors - polypeptide capsule and exotoxins

How is Clostridium difficile associated diseases treated?

• Mild uncomplicated cases respond to fluid and electrolyte replacement and withdrawal of antimicrobials • Severe infections treated with oral vancomycin or metronidazole and replacement cultures (poop tea) • Increased precautions to prevent spread

Characteristics of Clostridium difficile (C-diff)

• Normal resident of colon, in low numbers • Causes antibiotic-associated colitis (AAC) (Relatively non-invasive; treatment with broad-spectrum antibiotics kills the other bacteria, allowing C.difficile to overgrow) • Produces enterotoxins that damage intestines • Major cause of diarrhea in hospitals • Increasingly common in community-acquired diarrhea

Pathology of Listeria monocytogenes

• Primary reservoir is soil and water; animal intestines • Can contaminate foods and grow during refrigeration • Listeriosis - most cases associated with dairy products, poultry, and meat

How is Corynebacterium diagnosed?

• Pseudomembrane and swelling indicative • Stains • Conditions, history • Serological assay

Characteristics of Listeria monocytogenes

• Regular Non-spore-forming Gram-positive • Ranging from coccobacilli to long filaments • 1-4 flagella and lack capsules • Resistant to cold, heat, salt, pH extremes, and bile • Virulence attributed to ability to replicate in the cytoplasm of cells after inducing phagocytosis; avoids humoral immune system

Characteristics of Mycobacterium leprae

• Strict parasite - has not been grown on artificial media or tissue culture • Slowest growing of all species • Multiplies within host cells in large packets called globi • Causes leprosy, a chronic disease that begins in the skin and mucous membranes and progresses into nerves

Pathology of tetanus

• Transmission - Spores enter through accidental puncture wounds, burns, umbilical stumps, frostbite, and crushed body parts • Anaerobic environment is required for vegetative cells to grow and release toxin • Tetanospasmin - neurotoxin causes paralysis by binding to motor nerve endings; blocking the release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably • Death most often due to paralysis of respiratory muscles

How is tetanus treated?

• Treatment aimed at deterring degree of toxemia and infection and maintaining homeostasis • Antitoxin therapy with human tetanus immune globulin; inactivates circulating toxin but does not counteract that which is already bound • Control infection with penicillin or tetracycline; and muscle relaxants • Vaccine available; booster needed every 10 years

How is leprosy treated?

• Treatment by long-term combined therapy • Prevention requires constant surveillance of high-risk populations • WHO sponsoring a trial vaccine

Characteristic of Mycobacterium tuberculosis

• Tubercle bacillus • Produces no exotoxins or enzymes that contribute to infectiousness • Virulence factors: contain complex waxes and cord factor that prevent destruction by lysosomes or macrophages