MICR20 SJSU HAWKINS CHP 19

three groups of gram+ bacilli

- endospore formers

- non-endospore formers

- irregular shaped & staining properties

endospore

- dense survival unit that develops in a vegetative cell in response to nutrient deprivation

- resistant to heat, drying, radiation, & chemicals

general characteristics of genus Bacillus

- gram positive

- endospore-forming

- motile rods

- mostly saprobic

- aerobic & catalase positive

- source of antibiotics

- primary habitat is soil

- versatile in degrading complex macromolecules

saprobic

feed on dead organic matter

Bacillus anthracis

- large, block-shaped angular rods

- nonmotile

- central spores develop under all conditions in living body

- virulence factor = polypeptide capsule & exotoxins (edema, cell death)

- cases in livestock from Africa, Asia, & Middle East

- 3 types: cutaneous, pulmonary, gastrointestinal

cutaneous

- spores enter through skin

- black sore; eschar (dead tissue on skin)

- least dangerous

pulmonary

inhalation of spores from animal products or soil

gastrointestinal

- ingested spores

- rare

- lethal

general characteristics of Clostridium

- gram positive

- spore-forming rods

- anaerobic

- catalase negative

- 120 species

- synthesize organic acids, alcohols, & exotoxins

- cause wound infections, tissue infections, & food intoxications

Clostridium perfringens

- most frequent clostridia involved in soft tissue & wound infections

- virulence factors: alpha toxin, collagenase, hyaluronidase, DNase

gas gangrene/myonecrosis

- 2 forms: anaerobic cellulitis & true myonecrosis

- caused by Clostridium spp. (most commonly Clostridium perfringens)

anaerobic cellulitis

bacteria spread within damaged necrotic muscle tissue, producing toxins & gas, but infection remains localized

true myonecrosis

- More destructive, extensive gas gangrene/myonecrosis

- spore germination, vegetative growth & release of virulence factors

- fermentation of muscle carbohydrates results in the formation of gas & further tissue destruction

treatment & prevention of gas gangrene

- immediate cleansing of dirty wounds, deep wounds, compound fractures, & infected incisions

- debridement of disease tissue

- large doses of cephalosporin or penicillin

- hyperbaric oxygen therapy

- no vaccines

debridement

removal of dead or damaged tissue from a wound to promote healing

tetanus/lockjaw

- neuromuscular disease

- produced by Clostridium tetani

- spores enter body through accidental puncture wounds, burns, umbilicus, frostbite, & crushed body parts

- anaerobic environment required for vegetative cells to grow & release toxin

- "lock jaw" due to early effect of disease on jaw muscle

tetanospasmin

- neurotoxin causes paralysis by binding to motor nerve endings

- blocks release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably

- death most often due to paralysis of respiratory muscles

Clostridium difficile Infection

- caused by Clostridium difficile

- produces enterotoxins

- major cause of diarrhea in hospital

- 2nd most common intestinal disease after salmonellosis

enterotoxins

toxin produced that target intestinal tract

Clostridial food poisoning

- Clostridium botulinum

- Clostridium perfringens

Clostridium botulinum

- spore-forming anaerobe

- inhabits soil & water

- spores present on food when gathered & processed

- Botulinum toxin

Clostridium perfringens FP

- mild intestinal illness

- 2nd most common form of FP

Botulism

- intoxication associated with inadequate food preservation

- Botulinum toxin carried to neuromuscular junctions

- block release of acetylcholine

- double or blurred vision, difficulty swallowing, neuromuscular symptoms

acetylcholine

- neurotransmitter that plays a crucial role in physiological processes

- muscle movement, heart rate regulation & cognitive functions

infant botulism

- caused by ingested spores that germinate & release toxin

- most common type of botulism in US

- immature state of neonatal intestine & resident microbiota allow spores to gain a foothold, germinate & produce neurotoxin

- results in baby flaccid paralysis (floppy baby syndrome)

wound botulism

- spores enter wound & cause FP symptoms

- increased cases of this reported in injecting drug users

treatment & prevention of botulism

- determine presence of toxin in food, intestinal contents or feces

- administer antitoxin; cardiac & respiratory support

- infectious botulism treated w/ penicillin

- proper method of preserving & handling canned foods; preservatives

Clostridial Gastroenteritis

- caused by Clostrium perfringens

- spores contaminate food that has not been cooked well enough to destroy spores

- spores germinate & multiply

- when consumed, toxin produced in intestine; acts on epithelial cells, acute abdominal pain, diarrhea, & nausea

general characteristics of Mycobacteria: acid-fast Bacilli

- gram positive irregular bacilli

- acid-fast staining

- obligate aerobes

- catalase positive

- doesn't form capsules, flagella, or spores

- grow slowly

Mycobacterium tuberculosis

- tubercle bacillus (long, thin rod that grows in curvy masses

- no exotoxins or enzymes that contribute to infectiousness

- virulence factors = contain complex waves & cord factor that prevent destruction by lysosomes or macrophages

tuberculosis

- inadequate nutrition

- debilitation of immune system

- poor access to medical care

- lung damage

- genetics

- transmitted by airborne respiratory droplets

tuberculosis divisions

- primary tuberculosis

- secondary TB

- disseminated/extrapulmonary TB

primary TB

- infectious dose: 10 cells

- after 3-4 weeks, forms tubercules

- if center of tubercle breaks down into necrotic caseous lesions, they heal by calcification

detecting TB

- tuberculin sensitivity in-vivo (Mantoux test)

- in vitro TB test (QuantiFERON-TB Gold test, T-SPOT TB test)

- chest x-rays (non-diagnostic, used to rule out pulmonary TB)

- acid-fast staining (Ziehl-Neelsen stain; Fluorescence stain)

- cultural isolation & biochemical testing (most accurate diagnosis)

in-vivo

within living organism

management & prevention of TB

- 6 to 24 months of at least 2 drugs from 11 listed

- stains of M. tuberculosis resistant to at least 1 of 11 listed

Mycobacterium leprae

- Hansen's bacillus/Hansen's Disease

- obligate parasite

- slowest growing of all species

- multiplies within host cells in large packets called globi

- causes leprosy

- macrophage phagocytize bacilli, but weakened macrophage or slow T cell may not kill it

leprosy

chronic disease that begins in skin & mucous membranes & progresses into nerves

epidemiology & transmission of leprosy

- endemic regions throughout world

- transmission not fully verified

- not highly virulent

endemic

regularly occurring within a area or community

Tuberculoid/paucibacillary leprosy

- few bacilli in lesions

- shallow skin lesions in many areas

- dermal nerve damage; loss of pain sensation in lesions

- no skin modules

- occasional mutilation of extremeties

- reactive to lepromin

- lymph nodes not infiltrated by bacilli

- well developed cell-mediated response

- more easily treated

Lepromatous/multibacillary leprosy

- many bacilli in lesions

- numerous deeper lesions concentrated in cooler areas of body; causes severe disfigurement

- sensory loss more generalized; occurs late in disease

- gross skin modules

- mutilation of extremities common

- not reactive to lepromin

- lymph nodes massively infiltrated by bacilli

- poorly developed T-cell response

lepromin

extract of the leprosy bacillus injected intradermally to detect delayed allergy to leprosy

diagnosing leprosy

- combination of symptomology, microscopic examination of lesions, & patient history

- numbness in hands & feet, loss of heat & cold sens., muscle weakness, thickened earlobes, chronic stuffy nose

- detection of acid-fast bacilli in skin lesions, nasal discharges, & tissue samples

treatment of leprosy

- long-term combined therapy

- prevention requires constant surveillance of high-risk pop.

- no vaccine for leprosy

Disseminated Micobacterial Infection in AIDS

- caused by Mycobacterium avium complex bacilli

- 3rd most common cause of death in AIDS patients

nontuberculous lung disease

- Mycobacterium kansasii causes pulmonary infections in adult white males w/ emphysema or bronchitis

Mycobacterium marinum

- water inhabitant

- lesions develop after scraping on swimming pool concrete

- disease: fish tank granuloma

Mycobacterium scrofulaceium

- infects cervical lymph nodes in children living in Great Lakes region, Canada & Japan

Mycobacterium paratuberculosis

- raw cow's milk

- recovered from 65% of individuals diagnosed w/ Crohn's disease

bacteria that produce endospores

Bacillus & Clostridium

detecting endospores

- staining techniques & phase contrast microscopy

- culture methods

- biochemical tests

- molecular techniques

difference b/w Bacillus & Clostridium

- bacillus is aerobic & clostridium is anaerobic

- both rod-shaped & form endospores

- bacillus forms large, colonies; clostridium form smaller, irregular colonies

- bacillus spores typically located centrally; clostridium spores are often terminal, causing bulges

Mantoux test (tuberculin skin test)

- to determine if a person has been exposed to Mycobacterium tuberculosis

- 0.1 mL of purified protein derivative tuberculin injected under skin in forearm

- injection site examined 48 to 72 hrs later

- positive if there is induration at injection site

induration

raised, hardened area of skin

non-tuberculosis mycobacteria

- M. marinum

- M. scrofulaceium

- M. paratuberculosis

- M. avium complex

- M. kansasii