MIC 401 Module 3

Clostridium

spore forming anaerobic gram positive rods; ubiquitously present in soil, water and sewage; act as normal GI microbiota; most are harmless saprophytes; cause food poisoning, tetanus, botulism, myonecrosis (gas gangrene), diarrhea, and colitis

Clostridium Disease Causing Attributes

form spores (survive in hostile environments); grow rapidly in oxygen deprived conditions; produce toxins

Clostridium Perfringens

large, rectangular, gram positive rod with spores; produces inner and outer zones of hemolysis on blood agar; produces one or more major lethal toxins and enterotoxin; commonly inhabits intestines of humans and animals

C.perfringens Diseases

soft tissue infections, food poisoning, necrotizing enteritis, and septicemia

C.perfringens Alpha Toxin

lyse erythrocytes, platelets, leukocytes, and endothelial cells; results in hemolysis, increased vascular permeability and bleeding

C.perfringens Beta Toxin

responsible for intestinal stasis, loss of mucosa with formation of necrotic lesions/necrotizing enteritis (inflammation of small intestine)

C.perfringens Epsilon Toxin

increases the vascular permeability of the GI wall

C.perfringens Iota Toxin

has necrotic activity towards endothelial cells and increases vascular permeability

C.perfringens Theta Toxin

cholesterol binding cytolysin that lyse the target cell and plays a key role in the tissue destruction and vascular injury

C.perfringens Enterotoxin

binds to receptors on the brush border membrane of the small intestine and leads to pore formation, altered membrane permeability, and loss of fluids/ions

C.perfringens Soft Tissue Infections

cellulitis, fasciitis, myonecrosis

Clostridial Myonecrosis/Gas Gangrene

life threatening disease that illustrates the full virulence potential of histotoxic clostridia; onset characterized by intense pain, generally develops within a week after bacteria is introduced deep into the tissue by trauma or surgery; onset followed rapidly by extensive muscle necrosis, shock, renal failure, death (often within two days); hydrogen/carbon dioxide found in the tissue due to metabolic activity of the dividing bacteria

Clostridial Myonecrosis/Gas Gangrene - Diagnosis

gram stain of tissue or exudate from a patient will reveal abundant rectangular gram-positive rods with the absence of inflammatory cells (resulting of lysis by toxins)

Clostridial Myonecrosis/Gas Gangrene - Initial Treatment

immediate surgery (debridement) to remove all dead and infected tissue; high dose IV antibiotics (commonly penicillin plus clindamycin); hyperbaric oxygen therapy in selected cases

Clostridial Myonecrosis/Gas Gangrene - Amputation

may be required if infection has extensively destroyed muscle and soft tissue, continues to spread despite aggressive debridement, blood supply to the limb is severely compromised, limb salvage would endanger the patient’s life; limb salvage is possible when the diagnosis is made early and surgeons can completely remove the infective tissue

C.perfringens Food Poisoning

characterized by short incubation period, abdominal cramps and watery diarrhea but no fever, nausea, or vomiting, and clinical course lasting less than 24 hours; results from ingestion of meat products contaminated with large numbers of enterotoxins

C.perfringens Necrotizing Enteritis

rare process in the jejunum characterized by acute abdominal pain, vomiting, bloody diarrhea, ulceration of the small intestine, and perforation of the intestinal wall, leading to peritonitis and shock; mortality approaches 50%; beta toxin is responsible; managed by oral rehydration and IV electrolytes; common in Papua New Guinea

Clostridium Tetani

large, motile, spore forming rod; produces round, terminal spores that give it the appearance of a drumstick; proteolytic and are unable to ferment carbohydrates; produces tetanolysin and tetanospasmin toxins

C.tetani Tetanolysin

oxygen labile hemolysin

C.tetani Tetanospasmin

plasmid-encoded, heat labile neurotoxin; released when the cell is lyses and is responsible for the clinical manifestations of tetanus; an A-B toxin with a disulfide bond holding the two chains together; inactivates proteins that regulate the release of glycine and GABA; leads to unregulated synaptic activity in the motor neurons resulting in spastic paralysis

Generalized Tetanus

involvement of the masseter muscles (trismus or lockjaw); characteristic sardonic smile results from sustained contraction of the facial muscles (risus sardonicus); other early signs are drooling, sweating, persistent back spasms (opisthotonos); more severe symptoms include cardiac arrhythmias, fluctuations in blood pressure, profound sweating, and dehydration

Localized Tetanus

disease remains confined to the musculature at the site of primary infection; cephalic variant is when the primary site is the head; relatively rare in the unties states because of vaccine induced immuntiy

Neonatal Tetanus

associated with an initial infection of the umbilical stump that progresses to become generalized; mortality in infants exceeds 90% and developmental defects are present in survivors; almost exclusive to developing countries

Tetanus Management

primary challenge is preventing violent, agonizing muscle spasms; patients kept in dark quiet rooms to minimize sensory triggers; given high doses of continuous sedatives and muscle relaxants; in severe cases, full neuromuscular blocking drugs are administered

Clostridium Botulism

large, fastidious, spore forming anaerobic rods; common in soil and water; eight antigenically distinct toxins (human disease is associated with A, B, E, and F); toxin binds specific glycoproteins on the surface of excitatory neurons and stimulates endocytosis of the toxin muscle; acidification inactivates the proteins that regulates the release of acetylcholine; results in flaccid paralysis (floppy limbs, muscle weakness, difficulty breathing, and eating)

Classic or Food Borne Botulism

associated with consumption of home-canned foods; the food may not appear spoiled, but even a small taste can cause full-blown clinical disease

Infant Botulism

more common and has been associated with consumption of foods (honey, milk powder) contaminated with spores and ingestion of spore-contaminated soil and dust

Wound Botulism

seen in black tar heroin suers through contaminated needles, or deep puncture wounds, gunshot wounds, surgery wounds

Inhalation Botulism

rare man made form and is a major concern of bioterrorism; toxin concentrated for purposes of aerosolization as a biological weapon; when administered in this manner; rapid onset and high mortality

Botulism Prognosis

complete recovery in patients requires many months to years, or until the affected nerve endings regrow

C.botulism Detection

confirmed if toxin activity is demonstrated in implicated foods or in the patient’s serum, feces, or gastric fluid; isolation from specimens contaminated with other organisms (feces, wounds) can be improved by heating the specimen for 10 minutes at 80 degrees to kill all non spore forming bacteria

C.botulism Treatment

adequate ventilatory support and use of antitoxin to inactivate unbound toxins circulating in the bloodstream; ventilatory support is extremely important in educing mortality; use of antibiotics (metronidazole, penicillin) may be helpful in wound form but not others because lysis of bacterial may release more toxin

C.botulism Prevention

maintain food in acid pH or store at 4 degrees or cooler to prevent spore formation; or destroying the preformed toxin (all toxins are inactivated by heating at 60-100 degrees for 10 minutes)

Clostridium Difficile

large, anaerobic spore-forming rod; produces a variety of volatile fatty acids that produce a barnyard/horse manure smell in culture; surface layer priteins are important for binding in the intestinal epithelium, leading to toxin production and subsequent tissue damage; part of the normal intestinal flora, disease develops in people taking antibiotics and organisms proliferate in the colon and produce toxins

C.difficile Toxin A

chemotactic for neutrophils, stimulating the infiltration of neutrophils into the ileum with release of cytokines resulting in inflammation; also produces cytopathic effect, resulting in disruption of the tight cell to cell junction, increased permeability of the intestinal wall, and subsequent diarrhea

C.difficile Toxin B

cytotoxin that causes actin to depolymerize, with resultant destruction of the cellular cytoskeleton

Pseudomembranous Colitis

caused by antibiotic- associated c.diff; confirmed by demonstration of the enterotoxin or cytotoxin in a stool specimen from a patient with clinical symptoms; watery diarrhea, severe abdominal pain, fever, nausea, and blood/pus in the stool; advanced inflammation of the colon with formation of pseudomembranes (mucus, dead cells, clotted blood, immune cells)

Pseudomembranous Colitis Treatment

discontinuing the antibiotic, medications like vancomycin/fidaxomcin to clear c.diff infection, and electrolytes, fecal microbiota transplant

Listeria

aerobic, non spore forming, gram positive rods; total of 29 species and subspecies; leading cause of deaths attributed to food borne illnesses

L.monocytogenes

most significant listeria pathogen; short, non branching, gram positive, facultatively anaerobic rod; grows at a broad temp range (1-45 degrees) and in a high concentration of salt; motile at room temp (end over end turning motion); weak beta hemolysis

Listeriosis Susceptible Populations

neonates, elderly, pregnant women, immunocompromised

Sources of L.monocytogenes

consumption of contaminated food, but human to human transmission can occur primarily from mother to child in utero or birth; large outbreaks are associated with contaminated food products; focal epidemics and sporadic cases are associated with consumption of undercooked processed meat

Sources of L.monocytogenes - Reason

listera can grow in a wide pH range and at cold temperatures, foods with small numbers of organisms can become heavily contaminated during prolonged refrigeration

L.monocytogenes Pathogen

intracellular; able to survive exposure to proteolytic enzymes, stomach acid, and bile salts through stress response genes; able to adhere to host cells of the bacteria (InIA and InIB)

Internalin A InIA

interacts with the host E-cadherin receptor

Internalin B InIB

interacts with host Met tyrosine kinase receptor

L.monocytogenes Infection Initiated

in the enterocytes or M cells in peyer patches; after entry into cells, the acid pH of the phagolysosome activates bacterial pore forming toxin (listeriolysin O) and enzyme (phospholipase C) leading to release of the bacteria into the cell cytosol

ActA

bacterial protein; mediates L.monocytogenes movement into the cell membrane; coordinates assembly of actin

L.monocytogenes Trojan Horse Mechanism

entry into macrophages after passage through the intestinal lining carries the bacteria into the liver, spleen, and brain, leading to disseminated disease

Protrusion/Filopod

pushes L.monocytogenes bacteria into adjacent cells

Listeriosis - Neonates

early onset disease acquired transplacentally in utero (can lead to abortion, stillbirth, or premature birth); late onset disease is required soon after birth

Granulomatosis Infantiseptica

severe form of early onset listeriosis characterized by the formation of abscesses and granulomas in multiple organs and a high mortality rate unless treated promptly

Meningitis/Meningoencephalitis with Septicemia

late onset listeriosis that occurs 2 to 3 weeks after birth; fecal oral route due to cross xcontamination and lack of hygiene

Listeriosis - Infections in Pregnant Females

occur during the third trimester when cellular immunity is most impaired; contaminated food and beverages; influenza-like symptoms, low grade fever, and bacteremia

Listeriosis - Disease in Healthy Adults

most infections are asymptomatic or occur in a mild flu-like illness; an acute self limited gastroenteritis develops in some patients, characterized by 1 day incubation period followed by 2 days of symptoms (watery diarrhea, fever, nausea, headache, myalgias, and arthralgias)

Listeriosis - Disease in Elderly Patients/Immunocompromised

more severe; can result in meningitis with high mortality (20-50%)

Listeriosis - Survivors

experience significant neurologic sequelae

Listeriosis - Treatment and Prevention

the combination of gentamicin with penicillin or ampicillin is the drug of choice for serious infections; people at high risk of infection should avoid eating raw or partially cooked foods of animal origin, soft cheeses, and unwashed raw vegetables

B.anthracis Bioterrorism

one of the most feared agents of biological warfare; attack after 9/11

Bacillus

many aerobic/facultative anaerobic endospore-producing gram positive rods; catalase positive; ubiquitous in nature (found in decaying organic matter, dust, soil, vegetables, and water); produce multiple extracellular products, including antimicrobial substances, enzymes, and toxins

Risk Factors for Bacillus

IV drug use; foreign bodies including IV caths; immunosuppression from malignancy, neutropenia, corticosteroid use; AIDS

B.anthracis

large organism arranged in single or paired rods; spores are readily observed in 2 to 3 day old cultures but are not seen in fresh clinical specimens; major virulence factors are the capsule, edema toxin, and lethal toxin

B.anthracis - Polypeptide Capsule

consists of poly-d-glutamic acid; anti-phagocytic

B.anthracis - Edema Toxin

responsible for the fluid accumulation observed in anthrax; converts ATP → cAMP → elevates intracellular cAMP levels → disruption of water homeostasis → water leaks out → fluid accumulation in the tissue

B.anthracis - Lethal Toxin

disrupts the whole MAPK signaling pathway → disrupts metabolism, transcription, and translation → immune cell lysis resulting in inflammation and necrosis

B.anthracis - Other Virulent Effects

causes apoptosis of endothelial cells → internal hemorrhaging, uncontrolled systemic fluid leakage, systemic shock, cardiac failure

Anthrax

primarily a disease of herbivores; humans are infected through contaminated animals or animal products; serious problem in countries in which animal vaccination is not practiced

Anthrax - Toxiod Vaccine

given to high risk individuals like lab workers, animal handler, and deploying military personnel

Anthrax - Livestock Vaccine

live, dormant bacterial spores of an attenuated (weakened) steme strain (incapable of producing capsule)

Acquiring Anthrax

contact inoculation, ingestion, and inhalation

Cutaneous Anthrax

95% of naturally acquired anthrax; results from inoculation if spores through exposed skin from contaminated soil or infected animal products; starts with the development of a painless papule that rapidly progresses into an ulcer, then to a necrotic eschar; systemic signs, painful lymphadenopathy, and massive edema may develop; mortality rate is 20%

Gastrointestinal Anthrax

a rare and serious infection caused by eating raw or undercooked meat from an animal sick with B.anthracis bacteria; mortality rate is over 50%

GI Anthrax - Upper Intestinal Tract

ulcers form in the mouth or esophagus, leading to regional lymphadenopathy, edema, and sepsis

GI Anthrax - Lower Intestinal Tract

the patient presents with nausea, vomiting, and malaise, which rapidly progresses to systemic disease

Pulmonary Anthrax

spores reach the lower airways, in which alveolar macrophages ingest the inhaled spores and transport them to the mediastinal lymph nodes; pneumonia rarely develops; meningeal symptoms are seen in half of patients; almost all cases progress to shock and death within 3 days without treatment

Pulmonary Anthrax - Initial Symptoms

fever, myalgias, nonproductive cough, and malaise

Pulmonary Anthrax - Secondary Stage

rapidly worsening course of fever, edema, massive enlargement of the mediastinal lymph nodes (responsible for widened mediastinum observed on chest radiography); respiratory failure, sepsis

Cutaneous Anthrax Treatment

use of ciprofloxacin, doxycycline, or moxifloxacin

Severe Anthrax Treatment

IV triple therapy with a fluoroquinolone (a floxacin) combined with a beta lactam (meropenem) and protein synthesis inhibitor (linezolid, clindamycin, or rifampicin)

B.cereus

pathogen associated with gastroenteritis, ocular infections, and IV catheter related sepsis (associated with skin flora); emetic and diarrheal form

B.cereus Toxins

necrotic toxin (enterotoxin), cereolysin (hemolysin), and phospholipase C (potent lecthinase)

B.cereus - Emetic Disease

results from consumption of contaminated starch rich foods (pasta and rice); heat resistant spores survive in initial cooking; heat stable enterotoxin is not destroyed when reheated; symptoms show up within 1-6 hours and include vomiting, nausea, and abdominal cramps; fever and diarrhea are generally absent

B.cereus - Diarrheal Disease

true infection resulting from ingestion of bacteria in contaminated meat, vegetables, or sauces; longer incubation period where the organism multiples in the intestinal tract; release of heat-liable enterotoxin follows; responsible for diarrhea, nausea, and abdominal cramps

B.cereus - Ocular Infections

usually occur after traumatic, penetrating injuries of the eye with a soil-contaminated object

Bacillus Panophthalmitis

rapidly progressive disease that almost universally results in complete eye loss within 48 hours of the injury; must be treated rapidly with vancomycin, clindamycin, ciprofloxacin, and gentamicin

Corynobacterium

genus of non-spore forming pleomorphic gram positive rods; aerobic or facultatively anaerobic; non motile; catalase positive; club shaped L or V rods; normally colonize the skin, upper R tract, GI tract, and urogenital tract

Diphtheria Toxin

major virulence factor of C.diphtheriae; tox gene encodes for the exotoxin into strains of the disease by lysogenic bacteriophage (beta phage); an example of the classic AB exotoxin; receptor is the heparin-binding epidermal growth factor receptor (present in heart and nerve cells)

Diphtheria Toxin After Host Attachment

catalytic A region enters the cell cytosol; A subunit terminates host cell protein synthesis by inactivating elongation factor 2 (EF2)

EF2

required for the movement of peptide chains across the ribosome

Exposure to C.diphtheriae

may result in asymptomatic colonization in fully immune people; mild respiratory disease in partially immune patients; or a fulminant, sometimes fatal disease in nonimmune patients; organisms multiply locally in the epithelial cells in the pharynx or adjacent surfaces and initially cause localized damage as a result of exotoxin activity

Symptoms of Diphtheria

involve the respiratory tract; develop after a 2-4 day incubation period; onset is sudden, with malaise, sore throat, exudative pharyngitis, and a low grade fever; systemic complications primarily involve the heart and nervous system (myocarditis and neurotoxicity); majority of patients with severe disease develop neuropathy, initially localized to the soft palate and pharynx, later involving oculomotor and ciliary paralysis with progression to peripheral neuritis

Diphtheria Exudate

evolves into a thick pseudomembrane composed of bacteria, lymphocytes, plasma cells, fibrin, and dead cells that can cover the tonsils, uvula, and palate; difficult to dislodge

Cutaneous Diphtheria

acquired through skin contact with other infected people; organism colonizes the skin and gains entry to sub tissue through breaks into the skin; papule develops first and then evolves into a chronic, non healing ulcer, sometimes covered with a grayish membrane

Diphtheria Treatment

antitoxin (neutralizes the exotoxin); antibiotic therapy with penicillin or erythromycin; active immunization through DPT vaccine at ages 2, 4, 6, 15, to 18 months, and 4 to 6 years

Digestive System

primary purpose is to release food an nutrients for absorption and use; GI tract and organs (major entry/exit portal for pathogens); accessory digestion organs; immune related lymphoid tissues (70% of immune system, critical role against infections and disease)

Immune Components of Digestive System

small intestines, MALT, peyer’s patches, M-cells

Gastritis

stomach inflammation

Enteritis

intestinal inflammation

Barriers that Limit Pathogen Colonization/Infection of the GI Tract

protective mucus lining acts as a physical barrier, preventing microbes from attaching; microbial death/inactivation by enzymes, acidity of gastric juices, and bile salts; MALT; microbiota

MALT

GI tract immune cells and lymphatic tissue; sample the gI environment via phagocytosis; if invader detected, may result in initiation of inflammation followed by activation of adaptive immune responses (T and B lymphocytes)