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58 Cards in this Set
- Front
- Back
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Corynebacterium
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Gram + rods, not acid fast, pleomorphic shapes, coccobacilli look like irregular rods, clubbed ends on rods, sometimes look like chinese letters.
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Clinical relevance of Corynebacterium
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Pathogens: C.diphtheriae, Opportunistic pathogens: Corynebacterium jeikeium, Corynebacterium ulcerans; other species, non pathogens: Coryneforms rarely cause disease.
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Coryneform diptheriae: second type of disease
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Impetigo like skin lesions, lesions progress from small to larger, rarely fatal, little or no toxin effect, most common in tropics occasionally in American Indians and other groups with no immunizations and poor hygiene. Spread by direct contact with skin.
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Corynebacterium diptheriae causes diphtheria in humans.
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toxin produced by the organism spreads throughout the body from the pharyngeal or nasal area.
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Pathogenesis of diptheria
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Local infection of the throat; bacteria carries a phage that encodes a protein exotoxin; exotoxin spreads systemically; one molecule of exotoxin can halt protein synthesis of an entire cell.
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Diptheria exotoxin
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B subunit binds to cell receptor; b subunit facilitates movement of toxin into the cell, A subunit actively shuts off protein synthesis. The target is PROTEIN ELONGATION FACTOR 2; A subunit can recycle form ribosome to ribosome until all are shut down.
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Diptheria prevention and Immunity: The D in DPT
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Diptheria toxin is antigenic; Formalin converts the toxin to "toxoid," toxoid retains antigenicity, no toxicity, toxoi is used to immunize
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What does Diptheria immunization prevent?
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It prevents the disease not the Corynebacterium diptheria infection; classic diptheria disease still occurs in unimmunized populations.
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Clinical aspects of diptheria
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Incubation period is 2-4 days; presents as pharyngitis or tonsillitis with malaise, sore throat and fever; grey-white patch of exudate or membrane develops on tonsils, uvula, soft palate or pharyngeal wall. (The membrane is composed of coagulum of fibrin, leukocytes and cellular debris. Cervical adenitis produces neck edema.
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Treatment if diptheria
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must begin immediately with antitoxin and antibiotics, cannot wait for culture results days later. Can't use lab culture to visualize b/c you can't tell normal flora of the same genus from an infection.
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What are some antibiotics commonly used to treat diptheria?
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erythromycin, penicillin, cephalosporins and tetracycline, also use antitoxin (toxin can effect the heart) and keep the airway open.
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C. ulcerans infection
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Intermediate in pathogenicity; may carry toxin producing phage, toxin same as diptheria toxin but greatly reduced, milder systemic symptoms. Infects throat, pharynx and skin.
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C. jeikeium
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Most common pathogen from this genus causing nosocomial infection; opportunistic pathogen; Infects immunosuppressed patients
Bacteremia Catheter infection Artificial heart valve infection |
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What are the two most common causes of death in diptheria?
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asphyxiation, 2nd myocarditis.
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Listeria monocytogenes
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gram positive rod, resemble diptheroids with oval form, short gram positive rods, no spores produced, often seen intracellularly, pathogenicity based on ability to grow intracellularly.
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Colony Information about Listeria Monocytogenes
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Beta hemolytic narrow zone, catalase positive, tumbling motility
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Listeria monocytogenes
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reservoirs: soil, water, decaying vegetation; animals, especially dairy animals, asymptomatic carriers 5-10%
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How is Listeria acquired?
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Via ingestion; becomes intracellular organism in the body this aids in pathogenicity and spread.
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What diseases can be caused by Listeria?
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meningitis in immunocompromised individuals, also it can cross the placenta and cause neonatal meningitis.
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Epidemiology of Listeroisis II
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food borne outbreaks; survives and grows in the cold 4 degrees C, dairy food contamination; affects cheese cole slaw and deli meats
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Pathogenisis of Listeria M
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Intracellular, grows in macrophages which helps with transportation around the body; Internalin: cell attachment molecule, listeriolysin: aids movement within the cell; actin: used to move new cells, protective immunity is cell mediated.
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Listeria monocytogenes in CSF
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Gram stain: intracellular, gram positive rods and coccobacilli
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Clinical aspects of Listeroisis
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Infects immunosupressed; also preggers, may cause spontaneous abortion; neonates: meningitis, bacteremia.
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Lab Diagnosis of Liseria monocytogenes
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intracellular gram positive rods (in macrophages and neutrophils) blood culture to agar subculture to agar, looks like beta strep but is catalase positive, sensitive to streptomycin and may see tumbling motility.
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Unusual motility of Listeria M.
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In motility agar stabs, it forms an umbrella of turbidity in motility agar, in broth it produces tumbling motility.
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Erysipelothrix rhusiopathiae
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Gram positive diphtheroid-like rod.
Found in animals, meat, and sea food |
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E. rhusiopathiae Infection
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Disease: Erysipeloid: Painful slowly spreading skin infection, Follows traumatic inoculation of skin
Fishermen, butchers, veterinarians Treatment: Penicillin or erythromycin |
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Characteristics of E. rhusiophahiae
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Positive for hydrogen sulfide, “Test-tube brush” motility
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Lactobacillus
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Long Gram positive rods in chains, Classified as “aerotolerant” anaerobe
Many strains tolerate a bit of oxygen, Many species Most common in man: L. acidophilus Colony looks like viridans streptococci Normal flora of vagina, gut, mouth. Not considered to be pathogens Isolated in rare cases of infection in extremely immunosuppressed. |
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Normal Vaginal Gram Stain
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Seen are:
Vaginal epithelial cells Lactobacilli |
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Gardnerella vaginalis
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it is associated with vaginitis; found with increased gram negative anaerobes; found with decreased lactobacilli; so is it a marker or a cause of infection?
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Gardnerella vaginallis
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Clue cell in vaginitis infection; on gram stain vaginal epithelial cell coated with Garnderella and anaerobes, very few lactobacilli present.
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Diagnosis of vaginitis
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gram stain of vaginal sample (relative numbers of lactobacilli vs. other gram negative or gram variable rods), culture is NOT an effective way to diagnose; pH test of vaginal secretions (check for loss of acidity); sniff test of vaginal fluid, addition of KOH causes aromatic amines to be released if present
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Other Gram Positive Non-Sporeforming Rods
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Propionibacterium species, an anaerobe, slightly aerotolerant; Normal skin flora: opportunistic pathogen, common blood culture contaminant; how do you know when to treat? use similar criteria for coagulase negative streptococci
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Propionibacterium acnes
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“Anaerobic diphtheroid”
“Anaerobic coryneform” P. acnes is normal flora of skin: similar pathogenicity to staph epidermidis, can cause opportunistic infection; Has caused endocarditis. Infects implanted plastic devices Participates in multi-organism abscesses, and wound infections. Requires anaerobic culture. |
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All Bacillus species
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Spore forming Gram positive rods; grow best in air; catalase positive; non-pathogens are usually motile; old cells may stain as gram negative, can fool lab if spores are not seen.
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Common Bacillus Species are usually what?
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Non pathogenic. Occasionally they are pathogenic.
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Bacillus subtilis causes what?
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Wounds and bacteremias.
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Bacillus Cereus causes what?
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Wounds and bacteremias; food poisoning.
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Bacillus subtilis causes opportunistic infections where?
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In skin and soft tissue. Infects immunosuppressed, causing bacteremia and wound infections but NO food poisoning. ***Antibiotic susceptibility is unpredictable.
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Bacillus cereus colonies are characterized by what?
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motile with no capsule; beta hemolytic colonies on blood agar.
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What are the toxins produced by Bacillus cereus?
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Enterotoxins (2) act like cholera and toxigenic E. coli toxins; pyogenic toxins-destructive process in wounds and abscesses.
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What diseases are caused by Bacillus Cereus?
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Skin and soft tissue infections (diagnose by culture and identification); food poisoning (food warmer foods become overgrown) diagnose by culture of food and feces for B. cereus.
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What organisms are affected by anthrax?
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Cattle, horses and goats are infected by eating spores on grass.
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How are humans infected with anthrax?
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By skin contact with infected articles (most common form), by inhalation (most deadly form), eating spores or infected meat (common in animals, rare in man)
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Although anthrax is a rare disease in the USA, what populations are at risk?
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occasional outbreaks in southwest in cattle near Mexico; Occupational risk for farmers, ranchers butchers and vets; also risk for artists working to weave tapestries with imported wools that are sometimes contaminated with spores.
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What are the virulence factors of anthrax?
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capsule production (antiphagocytic); exotoxins: lethal toxin, edema toxin (protein carbohydrate complexes produce edema and death); immunity to exotoxin is protective
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What is the role of protective antigen in anthrax infections?
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binds and transports the two exotoxins into the host cell; antigen must be present for the exotoxins to work.
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What is the presentation of cutaneous anthrax?
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.5-12 days following spore entry into skin an erythematous papule forms resembling an insect bite. Lesion grows until black scab forms 7-10 days followed by healing.
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What are complication of cutaneous anthrax?
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local edema, toxemia, bacteremia, death. Death 1% if treated, 20% if untreated.
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What is the presentation of GI anthrax?
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Incubation period 1-7 days, lesion at base of tongue or tonsils, sore throat, fever, regional lymphadenopathy, inflammation and lesions of intestines, nausea, vomiting, fever, pain, vomiting blood and bloody diarrhea. Untreated fatality rate is 25-60%
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What is the presentation of pulmonary anthrax?
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worst form of the disease; symptoms begin 1-43 days after inhalation of spores, (typical incubation period 9-10 days), initial symptoms are sore throat, mild fever, malaise, cough, muscle aches.
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In inhalation anthrax spores do not immediately germinate within the alveolar recesses. They reside there and are taken up by what?
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Alveolar macrophages; spores then germinate and begin replication within the macrophages.
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What is a complication for giving antibiotics in inhalation anthrax?
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inactive spores are unaffected by antibiotics; once antibiotics are stopped any ungerminated spores could initiate an infection,
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What are the late symptoms of inhalation anthrax?
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severe difficulty breathing and shock; progressive respiratory distress with cyanosis; meningitis; massive edema of neck and chest (rapidly fatal once edema develops)
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Bacillus colonies not bacillus anthracis look like what?
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non pathogens are dry, wrinkled and rarely mucoid, most are beta hemolytic.
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Lab testing protocols for anthrax
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Culture only clinically ill people who have fever, myalgia and other non-specific findings.
Take BLOOD CULTURES and do X-Rays. Sputum cultures and nasal swabs are not appropriate testing since sputum is not produced in anthrax and spores disappear from upper airway quickly. |
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natural bacillus anthracis is sensitive to which antibiotic?
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penicillin G. Immunizations are available to military.
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