Chapter 19 The Gram-Positive Bacilli of Medical Importance

Chapter 19

The Gram-Positive Bacilli of Medical The Gram-Positive Bacilli of Medical ImportanceImportance

Medically Important Gram-Positive Bacilli

The gram-positive The gram-positive bacilli include about a bacilli include about a dozen genera of dozen genera of medically significant medically significant bacteriabacteria

They are differentiated They are differentiated on the basis of on the basis of endospores, acid-endospores, acid-fastness, and cell fastness, and cell morphologymorphology

Aerobic, Sporogenous Gram Positive Rods

Bacillus anthracisBacillus anthracis is the most prominent is the most prominent member of the genus member of the genus

Causative agent of antrax, a zoonosis that Causative agent of antrax, a zoonosis that exists in both cutaneous and pulmonary exists in both cutaneous and pulmonary formsforms

Clinical significance - B. anthracis = anthrax (seen primarily in cattle)

Human infections follow exposure to infected animals or Human infections follow exposure to infected animals or animal products - spores reside in soil & on plantsanimal products - spores reside in soil & on plants

Forms in humansForms in humans Pulmonary - follows inhalation of spores; usually observed Pulmonary - follows inhalation of spores; usually observed

in workers in woolen mills (woolsorter’s disease)in workers in woolen mills (woolsorter’s disease) Cutaneous = malignant pustule - follows cutaneous Cutaneous = malignant pustule - follows cutaneous

inoculation of spores; lesion is small initially but enlarges inoculation of spores; lesion is small initially but enlarges with formation of black eschar; self-limitingwith formation of black eschar; self-limiting

Gastrointestinal = follows ingestion of contaminated food; Gastrointestinal = follows ingestion of contaminated food; begins with nausea, abdominal pain & vomiting followed begins with nausea, abdominal pain & vomiting followed by bloody diarrhea, toxemia & shockby bloody diarrhea, toxemia & shock

Septicemia - may follow any formSepticemia - may follow any form

Cutaneous antrax

Epidemiology

Habitat - spores in soil & on plantsHabitat - spores in soil & on plants Routes of transmission - aerosols, direct Routes of transmission - aerosols, direct

contact, ingestioncontact, ingestion Prevention & control - difficult; vaccine for Prevention & control - difficult; vaccine for

susceptible individualssusceptible individuals Treatment - penicillinTreatment - penicillin

Anaerobic, Sporogenous Gram Positive Rods

ClostridiumClostridium C. tetaniC. tetani C. botulinumC. botulinum C. perfringensC. perfringens & other gas-producing & other gas-producing

clostridiaclostridia C. difficileC. difficile

General characteristics Gram positive, spore-forming rods - some are easily Gram positive, spore-forming rods - some are easily

decolorized; cells are usually large; should be suspected if decolorized; cells are usually large; should be suspected if large cells (either gram + or -) seen in Gram stainslarge cells (either gram + or -) seen in Gram stains

Virulence factorsVirulence factors Toxins Toxins

Neurotoxins of Neurotoxins of C. botulinum & C. tetaniC. botulinum & C. tetani Lethal toxins of Lethal toxins of C. perfringensC. perfringens - especially alpha toxin; - especially alpha toxin;

actually a lecithinaseactually a lecithinase Enterotoxin of Enterotoxin of C. perfringens & C. difficileC. perfringens & C. difficile

Enzymes - numerous including hyaluronidase, Enzymes - numerous including hyaluronidase, collagenase, proteases, RNAse, DNAse, lecithinasecollagenase, proteases, RNAse, DNAse, lecithinase

Clinical manifestations: C. tetani - tetanus (lockjaw)

Toxic disease associated with 2 toxins – Toxic disease associated with 2 toxins – tetanospasmintetanospasmin (neurotoxin) & tetanolysin (neurotoxin) & tetanolysin (hemolytic toxin)(hemolytic toxin)

Spores of organism found in feces of humans & Spores of organism found in feces of humans & variousvarious animals; found in soil, dust - survive for animals; found in soil, dust - survive for yearsyears

Incubation period = 1-54 daysIncubation period = 1-54 days Signs & symptoms = cramps & twitching in muscles Signs & symptoms = cramps & twitching in muscles

around wound, irritability, tachycardia & anxious around wound, irritability, tachycardia & anxious facialfacial expressions later progressing to lockjaw, expressions later progressing to lockjaw, spasms of the jaw and finally spasticity of neck, spasms of the jaw and finally spasticity of neck, trunk & limbstrunk & limbs

Clinical manifestations: C. tetani - tetanus (lockjaw)

Spores enter body through wound contaminated with soilSpores enter body through wound contaminated with soil or feces - require or feces - require relative deep wound to provide anaerobicrelative deep wound to provide anaerobic conditions for sporulation & toxin conditions for sporulation & toxin formulation formulation

Toxin reaches CNS through blood, lymph or travelingToxin reaches CNS through blood, lymph or traveling through tissue spaces through tissue spaces of peripheral nervesof peripheral nerves

Neurotoxin blocks neurotransmitter release preventing muscle contraction Neurotoxin blocks neurotransmitter release preventing muscle contraction when the opposing muscle contractswhen the opposing muscle contracts causing uncontrolled contraction of causing uncontrolled contraction of musclemuscle

Clinical manifestations: C. botulinum - botulism

Toxic disease associated with a Toxic disease associated with a neurotoxin - divides organisms into neurotoxin - divides organisms into serogroups based on antigenic type ofserogroups based on antigenic type of toxintoxin Botulinum toxin is most powerful Botulinum toxin is most powerful

toxin knowntoxin known Acts on neuromuscular junctions Acts on neuromuscular junctions

of peripheralof peripheral nervous system nervous system blocking release of nerve impulseblocking release of nerve impulse causing a “flaccid (floppy)” causing a “flaccid (floppy)” paralysisparalysis

Recovery of nerve function occurs Recovery of nerve function occurs only when newonly when new toxin-free nerve toxin-free nerve endings regeneratedendings regenerated

Antitoxin has no effect on bound Antitoxin has no effect on bound only free toxinonly free toxin


Foodborne botulismFoodborne botulism Follows ingestion of preformed toxinFollows ingestion of preformed toxin Foods most commonly involved = vegetables or Foods most commonly involved = vegetables or

condiments prepared from vegetables & fish (inadequately condiments prepared from vegetables & fish (inadequately processed home-canned food is mostprocessed home-canned food is most common source in common source in US)US)

Nausea, vomitting & diarrhea are first clinical signs - Nausea, vomitting & diarrhea are first clinical signs - neurologic symptoms usually appear 18-36neurologic symptoms usually appear 18-36 hours after hours after consumption of contaminated foodconsumption of contaminated food characterized by characterized by descending paralysis that beginsdescending paralysis that begins with ocular muscles with ocular muscles (diplopia) rapidly progressing to pharyngeal muscles (diplopia) rapidly progressing to pharyngeal muscles (dysphagia, hoarseness) & muscles of neck, trunk & limbs(dysphagia, hoarseness) & muscles of neck, trunk & limbs

Death occurs through paralysis of respiratory musclesDeath occurs through paralysis of respiratory muscles


Infant botulismInfant botulism Follows ingestion of spores which germinate in Follows ingestion of spores which germinate in

intestine & produce toxin in intestineintestine & produce toxin in intestine Foods most commonly involved - honeyFoods most commonly involved - honey Only infants under 1 year are affected - no stable Only infants under 1 year are affected - no stable

gut flora to inhibit germination of ingested sporesgut flora to inhibit germination of ingested spores Symptoms range from subclinical to deathSymptoms range from subclinical to death


Wound botulismWound botulism Follows contamination of a traumatic Follows contamination of a traumatic

wound with organism or as complication of wound with organism or as complication of chronic drug abusechronic drug abuse

Toxin released, absorbed & travels via Toxin released, absorbed & travels via lymph & blood to nerve terminalslymph & blood to nerve terminals

Symptoms similar to foodborne botulismSymptoms similar to foodborne botulism

C. perfringens & other gas-producing clostridia

Anaerobic cellulitisAnaerobic cellulitis Follows invasion of Follows invasion of

necrotic wound by necrotic wound by proteolytic clostridiaproteolytic clostridia

Characterized by gas Characterized by gas accumulation, accumulation, discoloration of discoloration of underlying skin and underlying skin and presence of malodorous, presence of malodorous, brownish, purulent brownish, purulent dischargedischarge

C. perfringens & other gas-producing clostridia

Myonecrosis (gas gangrene)Myonecrosis (gas gangrene) Involves invasion of normal healthy muscle surrounding Involves invasion of normal healthy muscle surrounding

traumatic woundtraumatic wound Associated with deep wounds (e.g. warfare) containing Associated with deep wounds (e.g. warfare) containing

foreign bodies, having blocked blood supplies and/or foreign bodies, having blocked blood supplies and/or presence of necrotic tissuepresence of necrotic tissue

Symptoms include drowsiness, fever, tachycardia & a Symptoms include drowsiness, fever, tachycardia & a painful edematous wound with a sweet or foul-smelling painful edematous wound with a sweet or foul-smelling discharge - gas is present but not as obvious as in cellulitis discharge - gas is present but not as obvious as in cellulitis - may be fatal- may be fatal

C. perfringensC. perfringens most common clostridial species involved most common clostridial species involved

C. difficile

Associated with 90-100% Associated with 90-100% of pseudomembranous of pseudomembranous enterocolitis following enterocolitis following antimicrobial therapy antimicrobial therapy especially following especially following clindamycin, clindamycin, cephalosporins & cephalosporins & ampicillinampicillin

C. difficile

Components of disease - disturbance of normal Components of disease - disturbance of normal bowel flora by antimicrobial agents, a source of bowel flora by antimicrobial agents, a source of C. C. difficiledifficile (endogenous or exogenous) & organism (endogenous or exogenous) & organism must have potential for producing toxinmust have potential for producing toxin

Sources of Sources of C. difficileC. difficile = hospital environment & = hospital environment & endogenous (normal intestinal flora of 3% healthy endogenous (normal intestinal flora of 3% healthy adults and 10-20% hospitalized patients)adults and 10-20% hospitalized patients)

Associated with two toxins - toxin A = enterotoxin Associated with two toxins - toxin A = enterotoxin causing diarrhea & toxin B = cytotoxin causing causing diarrhea & toxin B = cytotoxin causing cellular damagecellular damage

Epidemiology

HabitatHabitat Intestinal flora (Intestinal flora (C. perfringens, C. tetani C. perfringens, C. tetani

& C. difficile& C. difficile)) Environment - soil & animalsEnvironment - soil & animals

Routes of transmissionRoutes of transmission Traumatic woundsTraumatic wounds IngestionIngestion EndogenousEndogenous

Epidemiology

Prevention & ControlPrevention & Control Vaccine - tetanus toxoid (DPT)Vaccine - tetanus toxoid (DPT) Properly canning foodsProperly canning foods Avoid giving honey to child under 1 year (Avoid giving honey to child under 1 year (C. C.

botulinumbotulinum)) TreatmentTreatment

Tetanus & botulism - specific antitoxinTetanus & botulism - specific antitoxin Debridement of woundDebridement of wound Supportive therapy (respiratory assist)Supportive therapy (respiratory assist) Antibiotic therapy (antibiogram)Antibiotic therapy (antibiogram)

Gram-Positive Regular Non-Spore-Forming Bacilli

Non-spore-forming rods are divided among Non-spore-forming rods are divided among those that have regular and irregular shapes those that have regular and irregular shapes and staining propertiesand staining properties

Straight, nonpleomorphic rods stain evenly Straight, nonpleomorphic rods stain evenly and include the genera and include the genera ListeriaListeria and and ErysipelothrixErysipelothrix

Listeria Species of medical importance - Species of medical importance - L. L.

monocytogenesmonocytogenes; only species pathogenic for man; only species pathogenic for man Clinical manifestations - restricted to several Clinical manifestations - restricted to several

defined populationsdefined populations NeonatesNeonates

Early onset - acquired in utero or during birthEarly onset - acquired in utero or during birthGranulomatosis infantiseptica - fetus often Granulomatosis infantiseptica - fetus often

stillborn; multiple granulomasstillborn; multiple granulomasMeningitis and sepsisMeningitis and sepsis

Late onset - begins 2-3 weeks after birth; Late onset - begins 2-3 weeks after birth; acquired from environment = meningitis and acquired from environment = meningitis and sepsissepsis

Listeria

Pregnant women - puerperal sepsis & bacteremiaPregnant women - puerperal sepsis & bacteremia Immunocompromised - particularly with Immunocompromised - particularly with

malignancies or renal transplantmalignancies or renal transplant Meningitis - common cause in renal transplantsMeningitis - common cause in renal transplants EndocarditisEndocarditis

Fatalities - greater in newborn under 4 weeks & Fatalities - greater in newborn under 4 weeks & adults over 50adults over 50

Epidemiology Natural habitat - primarily Natural habitat - primarily

zoonotic but also found in zoonotic but also found in soil, water, vegetation & soil, water, vegetation & intestine of humansintestine of humans

Routes of transmissionRoutes of transmission Ingestion - esp. milk Ingestion - esp. milk

products (not always products (not always killed by killed by pasteurization), meat & pasteurization), meat & cabbagecabbage

Direct - female to Direct - female to infants or with infants or with environmental sourceenvironmental source

Prevention and control - Prevention and control - difficult (organisms are difficult (organisms are ubiquitous)ubiquitous)

Treatment - penicillinTreatment - penicillin

Erysipelothrix

Species of medical importance - Species of medical importance - E. E. rhusiopathiaerhusiopathiae

Clinical manifestations Clinical manifestations Septicemia and endocarditisSepticemia and endocarditis

Uncommon but seen together when Uncommon but seen together when they occurthey occur

Most susceptible = persons with Most susceptible = persons with previously damaged heart valvespreviously damaged heart valves

Erysipelothrix ErysipeloidErysipeloid

Inflammatory Inflammatory condition of skin; condition of skin; usually fingers & usually fingers & hands; suppurationhands; suppuration

Lesions usually Lesions usually erythematous with erythematous with raised edge; spread raised edge; spread peripherallyperipherally

Spontaneous cure = Spontaneous cure = usualusual

Epidemiology

Natural habitat - ubiquitous; primarily zoonotic Natural habitat - ubiquitous; primarily zoonotic (mammals, birds, & fish); pigs = main source of (mammals, birds, & fish); pigs = main source of human infection; also in soil where infected human infection; also in soil where infected animals grazeanimals graze

Modes of transmission = trauma (enter via Modes of transmission = trauma (enter via abrasions); usually occupational (esp. butchers, abrasions); usually occupational (esp. butchers, meat processors, farmers, poultry workers, meat processors, farmers, poultry workers, fisherman, vets)fisherman, vets)

Prevention and control - protective clothing when Prevention and control - protective clothing when handling infected sourceshandling infected sources

Treatment - penicillinTreatment - penicillin

Gram-Positive Irregular Non-Spore-Forming Bacilli

CorynebacteriumCorynebacterium Species of medial Species of medial

importanceimportance C. diphtheriaeC. diphtheriae C. ulceransC. ulcerans C. pseudotuberculosisC. pseudotuberculosis Group JKGroup JK

Clinical manifestations - C. diphtheriae

DiphtheriaDiphtheria Incubation period = 2-4 daysIncubation period = 2-4 days Begins as pharyngitis (toxigenic Begins as pharyngitis (toxigenic

& non-toxigenic strains)& non-toxigenic strains) Only toxigenic strains produce Only toxigenic strains produce

pseudomembrane (toxin causes pseudomembrane (toxin causes membrane; contains fibrin, membrane; contains fibrin, WBC’s, cellular debris & bacteria WBC’s, cellular debris & bacteria - forms on pharynx but may - forms on pharynx but may extend into trachea); cervical extend into trachea); cervical adenitis common = bullneck adenitis common = bullneck appearanceappearance

Uncomplicated diphtheria = Uncomplicated diphtheria = resolves; membrane is coughed resolves; membrane is coughed upup

Clinical manifestations - C. diphtheriae

Complications and mortality caused by respiratory Complications and mortality caused by respiratory obstruction or systemic effects of toxinobstruction or systemic effects of toxin

Obstruction of airway due to membrane, edema & Obstruction of airway due to membrane, edema & hemorrhage; can lead to sudden & complete hemorrhage; can lead to sudden & complete suffocation - deathsuffocation - death

Toxin may cause myocarditis (cardiac Toxin may cause myocarditis (cardiac enlargement, weakness, arrhythmia & CHF) and enlargement, weakness, arrhythmia & CHF) and paralysis of peripheral & cranial nerves (affected paralysis of peripheral & cranial nerves (affected = soft palate, eyes & some muscles usually not = soft palate, eyes & some muscles usually not serious unless diaphragm involved)serious unless diaphragm involved)

Epidemiology Prevention and control - Prevention and control - C. diphtheriaeC. diphtheriae Immunization with vaccine containing toxoidImmunization with vaccine containing toxoid Schick test - uses intracutaneous injection of Schick test - uses intracutaneous injection of

toxin; detects immune statustoxin; detects immune status Positive reaction = local edema, necrosis & Positive reaction = local edema, necrosis &

desquamation = susceptible (no antitoxin)desquamation = susceptible (no antitoxin) Negative reaction = no reaction = immune Negative reaction = no reaction = immune

(toxin neutralized by circulating Ab = (toxin neutralized by circulating Ab = antitoxin)antitoxin)

Epidemiology TreatmentTreatment

Antitoxin (antiserum)Antitoxin (antiserum) Uses preformed Ab’s produced in horses or humans Uses preformed Ab’s produced in horses or humans

(hyperimmune IgG)(hyperimmune IgG) Must be administered early before toxin attaches to Must be administered early before toxin attaches to

target cellstarget cells Hypersensitivity & serum sickness may result from Hypersensitivity & serum sickness may result from

horse serum & complicate therapyhorse serum & complicate therapy Antibiotics - penicillins & erythromycinAntibiotics - penicillins & erythromycin Supportive therapy - removal of obstructions, minimize Supportive therapy - removal of obstructions, minimize

CHF, regulate respirationCHF, regulate respiration

Mycobacteria

General characteristicsGeneral characteristics Aerobic, non-sporogenous, non-motile rodsAerobic, non-sporogenous, non-motile rods Acid fast - cells resist acid decolorizationAcid fast - cells resist acid decolorization Possess high levels of mycolic acids and Possess high levels of mycolic acids and

other lipids in addition to peptidoglycan in other lipids in addition to peptidoglycan in their cell wallstheir cell walls

Slow growing (2 days - 6 weeks)Slow growing (2 days - 6 weeks) Highly resistant to disinfectant & Highly resistant to disinfectant &

sterilization proceduressterilization procedures

Clinical Manifestations

M. lepraeM. leprae - Hansen's disease - Hansen's disease Chronic infectious disease - over 200 new cases diagnosed Chronic infectious disease - over 200 new cases diagnosed

each year; approx. 13 million person infected world-wideeach year; approx. 13 million person infected world-wide Method of transmission from person-person unknown; Method of transmission from person-person unknown;

depends on a susceptible hostdepends on a susceptible host Children more susceptible than adults; males more than Children more susceptible than adults; males more than

femalesfemales Most persons probably cannot be infected by any meansMost persons probably cannot be infected by any means May be acquired through skin-skin contact or contact with May be acquired through skin-skin contact or contact with

nasal dischargenasal discharge

M. leprae - Hansen's disease

Presents clinically in either Presents clinically in either of two major forms - form is of two major forms - form is dependent on adequacy of dependent on adequacy of host's cell-mediated responsehost's cell-mediated response Tuberculoid leprosy - Tuberculoid leprosy -

usually self-limiting; may usually self-limiting; may regress spontaneously; regress spontaneously; single skin lesions and single skin lesions and nerve involvement nerve involvement producing patches of producing patches of anesthesia most common anesthesia most common feature (produced by feature (produced by inflammatory response to inflammatory response to organisms); organisms organisms); organisms are extremely rare in are extremely rare in tissuetissue

M. leprae - Hansen's disease

Lepromatous leprosy - Lepromatous leprosy - progressive & malignant; progressive & malignant; may be fatal; skin may be fatal; skin involvement extensive; involvement extensive; organisms found in every organisms found in every organ - major changes organ - major changes detected in skin, nerves & detected in skin, nerves & testes; lesions of skin & testes; lesions of skin & mm - hypopigmented or mm - hypopigmented or nodular skin lesions nodular skin lesions common - nose common - nose deformities caused by deformities caused by destruction of cartilaginous destruction of cartilaginous septum by organisms; septum by organisms; involvement of peripheral involvement of peripheral nerves not severenerves not severe

Staging of tuberculosis

M. tuberculosis - occurs in 2 forms

Primary tuberculosis - seen in individuals who have never Primary tuberculosis - seen in individuals who have never been exposed to organismbeen exposed to organism

Organisms enter host by several routes including skin, Organisms enter host by several routes including skin, genitourinary tract, alimentary tract - most acquire through genitourinary tract, alimentary tract - most acquire through respiratory tractrespiratory tract

Inhaled organisms become deposited in alveoli of the lung Inhaled organisms become deposited in alveoli of the lung and are phagocytized by alveolar macrophages where they and are phagocytized by alveolar macrophages where they multiplymultiply

Organisms generally encounter little host resistance; are Organisms generally encounter little host resistance; are carried to lymph nodes through the lymphaticscarried to lymph nodes through the lymphatics

If organisms escape lymph nodes, enter the blood via the If organisms escape lymph nodes, enter the blood via the thoracic duct - are disseminated throughout the body thoracic duct - are disseminated throughout the body producing numerous foci in various organsproducing numerous foci in various organs

Primary TB

Primary features of disease = tubercles & caseous Primary features of disease = tubercles & caseous necrosisnecrosis

Tubercles formed when macrophages surround Tubercles formed when macrophages surround organisms forming elongated epithelioid cells organisms forming elongated epithelioid cells arranged in concentric layers to form the arranged in concentric layers to form the granulomatous tubercles - tubercles are classically granulomatous tubercles - tubercles are classically surrounded by lymphocytes & fibroblastssurrounded by lymphocytes & fibroblasts

Caseous necrosis - characterized by disintegration Caseous necrosis - characterized by disintegration of tubercle forming a coagulated, homogenous, of tubercle forming a coagulated, homogenous, cheeselike masscheeselike mass

Progression of infection to disease depends on adequacy of CMI response - may be assisted by

humoral response

Good immune response - decreased multiplication Good immune response - decreased multiplication of organisms, cessation of dissemination and of organisms, cessation of dissemination and healing of lesions by fibrosis & calcification healing of lesions by fibrosis & calcification (Ghon complex) - organisms may remain viable in (Ghon complex) - organisms may remain viable in these lesions for many yearsthese lesions for many years

Poor immune response - progression to disease Poor immune response - progression to disease with liquification of caseous mass, rupture of with liquification of caseous mass, rupture of tubercle lesion and spread of organisms to other tubercle lesion and spread of organisms to other parts of lung and bodyparts of lung and body

Secondary or reactivation tuberculosis

Occurs in persons who have been previously Occurs in persons who have been previously infectedinfected

Associated with a breakdown in host’s cellular Associated with a breakdown in host’s cellular immune system (age, diabetes, obstructive immune system (age, diabetes, obstructive pulmonary disease or other diseases)pulmonary disease or other diseases)

Localized lesion becomes necrotic and liquifies - Localized lesion becomes necrotic and liquifies - may rupture into pulmonary vein and become may rupture into pulmonary vein and become disseminated to other body parts (miliary tb)disseminated to other body parts (miliary tb)

Mycobacteria Other Than Tuberculosis (MOTT)

Pulmonary diseasePulmonary disease Organisms most commonly involved include Organisms most commonly involved include M. M.

kansasiikansasii & & M. avium-intracellulareM. avium-intracellulare complex complex Usually occurs in middle-aged men with chronic Usually occurs in middle-aged men with chronic

lung diseaselung disease Predisposing conditions = pneumoconiosis (coal Predisposing conditions = pneumoconiosis (coal

miner’s disease), previous tb, chronic bronchitis, miner’s disease), previous tb, chronic bronchitis, chronic obstructive lung disease, lung malignancy, chronic obstructive lung disease, lung malignancy, AIDSAIDS


Skin & soft tissue infectionsSkin & soft tissue infections Associated with Associated with M. fortuitum, M. chelonae, M. fortuitum, M. chelonae,

M. marinumM. marinum & & M. ulceransM. ulcerans M. fortuitum-chelonaeM. fortuitum-chelonae complex cause local complex cause local

abscesses at site of injections or after trauma abscesses at site of injections or after trauma & surgical wounds, corneal infections after & surgical wounds, corneal infections after penetrating injury to eye and endocarditis penetrating injury to eye and endocarditis after heart surgeryafter heart surgery

M. ulceransM. ulcerans - cause a cutaneous ulcer called - cause a cutaneous ulcer called Bairnsdale (Australia) or Buruli (Africa) ulcerBairnsdale (Australia) or Buruli (Africa) ulcer


M. marinumM. marinum - found in - found in fresh & salt water; fresh & salt water; cutaneous granulomas cutaneous granulomas and ulcers associated and ulcers associated with swimming pools with swimming pools (swimming pool (swimming pool granulomas) and granulomas) and aquariums (fish tank aquariums (fish tank granulomas)granulomas)

Epidemiology HabitatHabitat

M. lepraeM. leprae - humans constitute major source; armadillos - humans constitute major source; armadillos recently implicatedrecently implicated

M. tuberculosisM. tuberculosis - humans constitute major source - humans constitute major source MOTT - environment (soil, plants, water)MOTT - environment (soil, plants, water)

TransmissionTransmission Leprosy - unclear; probably skin-skin contact or contact Leprosy - unclear; probably skin-skin contact or contact

with nasal secretions - requires susceptible host (most with nasal secretions - requires susceptible host (most humans not susceptible)humans not susceptible)

Tuberculosis - aerosols most common mode; may also be Tuberculosis - aerosols most common mode; may also be acquired by ingestion or direct skin contactacquired by ingestion or direct skin contact

MOTT - human to human transmission not involved; MOTT - human to human transmission not involved; requires contact with environmental sourcerequires contact with environmental source

Control & prevention

Leprosy - treatment of case contacts; long Leprosy - treatment of case contacts; long incubation period (3-10 years); isolation of incubation period (3-10 years); isolation of known cases no longer necessary for more known cases no longer necessary for more than 2 monthsthan 2 months


TuberculosisTuberculosis Identification & treatment Identification & treatment

of infected personsof infected persons Skin testing - tuberculin Skin testing - tuberculin

(purified protein (purified protein derivative = PPD) derivative = PPD) injected subcutaneously; injected subcutaneously; positive = exposure - not positive = exposure - not diseasedisease

Control & prevention Xray evidence - Xray evidence -

calcified lesions may be calcified lesions may be evident as radiopaque evident as radiopaque area of lungarea of lung

Persons thought to be Persons thought to be candidates for active candidates for active diseases are treated for diseases are treated for 1 year with INH1 year with INH


Vaccine = BCG (Bacille of Calmette & Vaccine = BCG (Bacille of Calmette & Guerin); uses laboratory strain of Guerin); uses laboratory strain of M. bovisM. bovis

Widely used throughout the world to Widely used throughout the world to immunize negative tuberculin reactorsimmunize negative tuberculin reactors

Rarely used in US - primarily because Rarely used in US - primarily because successful immunization causes conversion successful immunization causes conversion of person to positive tuberculin test of person to positive tuberculin test

Treatment

Leprosy - sulfones (esp. dapsone); infectivity Leprosy - sulfones (esp. dapsone); infectivity disappears in 50 days may need to take drug for disappears in 50 days may need to take drug for lifelife

Tuberculosis - isoniazid hydrazine (INH) = drug Tuberculosis - isoniazid hydrazine (INH) = drug of choice; multiple resistance common today; of choice; multiple resistance common today; known cases often treated with multiple drugs known cases often treated with multiple drugs including streptomycin, rifampin, ethambutol & including streptomycin, rifampin, ethambutol & amikacinamikacin

MOTT - usually highly resistant to drugs; often MOTT - usually highly resistant to drugs; often require surgical removal of lesions to treatrequire surgical removal of lesions to treat

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Chapter 19 The Gram-Positive Bacilli of Medical Importance