Bacterial Infections of Soft Tissue: Anaerobes

Question 1

C. tetani bacteriology

Answer 1

spores are environmental. Gram +. transmitted to humans by soil contamination of wounds

Question 2

C. tetani pathogenesis

Answer 2

insertion beneath skin surface limits air contact. spores germinate and vegetative cells release exotoxin tetanospasmin.

Question 3

neonatal tetanus

Answer 3

contamination of umbilical cord + lack of maternal immunization. 90%+ mortality in second week of life. developmental delays common in survivors

Question 4

cephalic tetanus

Answer 4

rare, contamination of head wounds. patient presents with cranial nerve palsy.

Question 5

local tetanus

Answer 5

wound contamination -> rigidity in a single muscle group.

Question 6

generalized tetanus

Answer 6

bacteria form a locus of infection, and exotoxin tetanospasmin enters bloodstream. full-body symptoms cause morbidity. >50% untreated mortality from respiratory failure. 21-31% treated mortality

Question 7

tetanospasmin structure and function

Answer 7

2 subunits, large and small. large subunit is a ferry for the small unit. it opens a pore in the cell for the small unit to get in to the presynaptic motor neuron. cleaves synaptobrevin (VAMP) causing vesicles containing GABA and glycine not to be released. loss of inhibitory action = constant contraction

Question 8

C. tetani exam

Answer 8

sore throat, headache, local rigidity, strong muscle spasms. Trismus (lockjaw), grimace, opisthotonus (arching of back). spatula test: patients bite instead of gag when posterior pharyngeal wall is stimulated

Question 9

c. tetani lab

Answer 9

terminal spores give tennis racket on microscopy. bloodwork can confirm vaccination, rule out strychnine poisoning. no need for lumbar puncture. imaging studies unremarkable

Question 10

c. tetani treatment

Answer 10

tetanus antitoxin neutralizes toxin. metronidazole doesnt do much. valium to prevent spasms, other muscle relaxants can help

Question 11

C. tetani prevention

Answer 11

tetanus toxoid vaccine. booster every 10 years. adults can receive vaccine at any time. deep puncture should be cleaned and debrided and vaccine booster given. deep and clearly dirty wounds call for immune globulin and booster of vaccine

Question 12

c. botulinum bacteriology

Answer 12

environmental. gram +, spore forming. foodborne botulism is most common presentation. spores survive inadequate sterilization. germinating cells release one of 8 botulinum toxins: A-H. A and B are the most toxic.

Question 13

c botulinum pathogenesis

Answer 13

cooking inactivates toxin. germinating bacteria die in GI, but exotoxin is readily absorbed from the gut. carried in blood to peripheral nerve synapses. acts as protease cleaving synaptobrevin (VAMP). flaccid muscles.

Question 14

infant botulism

Answer 14

chile

Question 15

wound botulism

Answer 15

wound contaminated with soil. spores germinate and secrete exotoxin. IV drug use or immunosuppressed show this. rarely seen in C sections. infection may not be obvious at would site.

Question 16

c. botulinum exam

Answer 16

foodborne: descending weakness and paralysis. nausea, vomiting, diarrhea without fever. get history of suspect foods. check for trouble swallowing, double vision, fixed/dilated pupils, dry mouth

Question 17

c. botulinum lab

Answer 17

cultures not usually useful, can sometimes be grown from wound or GI tract. gram positivity may be lost after 18 hours in culture. toxin can be demonstrated in suspect food and patient samples. nerve studies usually unremarkable.

Question 18

c. botulinum treatment

Answer 18

admit for rigorous supportive care. respiratory support. for infant type A and B can get antitoxin. for adult and non AB, horse sourced antotoxin. can get serum sickness from antitoxin. induce vomiting / gastric lavage. enema. for wound also give IV penicillin

Question 19

c. botulinum long term treatment

Answer 19

full recovery in 1-12 months. physical and occupational therapy. psych consult and pastoral care for depression.

Question 20

what toxin is used in facial botox?

Answer 20

toxin A. small amounts!!!

Question 21

c. perfringens bacteriology

Answer 21

gas gangrene = myonecrosis = necrotizing faciitis. gram + spore forming rod. anaerobic environment required for replication and exotoxin production, relatively aerotolerant during host jumps

Question 22

c. perfringens pathogenesis

Answer 22

spores from soil or vegetative cells from GI enter wounds. necrotic tissue, foreign bodies, premature closure disrupt bloodflow and enhance germination. vegetative cells grow in deep tissue, especially muscle. produce >20 exotoxins. alpha toxin: lecithinase, necrotizing, hemolytic, cardiotoxic. degradative enzymes make gas in tissue. can lead to anemia and kidney failure.

Question 23

c. perfringens exam

Answer 23

pain, edema, and cellulitis at recent wound or surgical site. skin turns bronze then blue/black. site tender. short incubation but can be weeks. tachycardia. acute respiratory distress. shock, renal failure.

Question 24

c. perfringens radiology

Answer 24

feathering of gas in soft tissue. CT scan help in abdominal cases. ultrasound can see gas.

Question 25

myonecrosis

Answer 25

surgical exploration needed.

Question 26

c. perfringens lab

Answer 26

smears from tissue and exudate show large gram + rods. hemolytic anemia, increased lactate dehydrog, toxic shock. metabolic acidosis and renal failure. ELISA for alpha toxin and PCR for clostridial DNA. anaerobic culture can retroactively identify species.

Question 27

c. perfringens treatment and prevention

Answer 27

penicillin G + clindamycin. protein synth inhibitors shut down exotoxin production. additional antibiotics may be needed. ICU admit often needed. clean and debride wounds to prevent

Question 28

c. perfringens type A food poisoning

Answer 28

soil borne spores contaminate food. inadequate cooking doesnt kill. large numbers grow in reheated food. multiply in smal bowel. CPE enterotoxin of type A strains destroys tight junctions and causes diarrhea and ab pain.

Question 29

c. difficile bacteriology

Answer 29

gram + spore forming rod. causes pseudomembranous colitis = C. difficile associated diarrhea = antibiotic associated colitis = c. diff colitis. transmission: normal flora in 30% of hospitalized. fecal-oral.

Question 30

c. diff pathogenesis

Answer 30

recent antibiotics or chemo allow c. diff to overgrow. release exotoxin A, disrupting tight junctions. exotoxin B is major toxin, disrupts cytoskeleton by depolymerizing actin and killing surrounding cells.

Question 31

c. diff exam

Answer 31

nonbloody cramping diarrhea. green and smelly. fever, history of chemo or immunosuppressant/antibiotics. sigmoidoscopy shows patches of dead and dying cells as yellow/white plaques. focal necrosis of glandular crypts with neutrophilic infiltration and fibrin plugging of capillaries. can lead to abscesses

Question 32

c. diff lab

Answer 32

WBC and creatinine elevated. can be cultured from stool but is slow. ELISA for toxins A and B. not sensitive. cytotoxicty test. sensitive but slow (untreated stool filtrate kill human cells in culture). neutrophils in stool

Question 33

c. diff treatment

Answer 33

withdraw intitial antibiotic. replace fluids. give oral metronidazole or vancomycin. let toxins flush. surgical resection or removal of colon possible. fecal bacteriotherapy may prove effective

Question 34

actinomyces bacteriology

Answer 34

gram + folamentous rods. non spore forming. anaerobic to microaerophilic. normal flora of mouth and vag. cells form long branching filaments. polymicrobial infections. rare.

Question 35

actinomyces pathogenesis

Answer 35

bacteria escape proper compartment during accidental or surgical trauma. grow in hard filamentous nodules. slow and invasive growth. non-communicable

Question 36

actinomyces exam

Answer 36

head/neck: hard nontender swelling in neck/face/chest. untreated leads to more spots. pus draining through sinuses with hard yellow sulfur granules. history of dental work or bad teeth

abodmen: slow growing tumor. nonspecific abdominal symptoms. usually need surgery to rule out cancer. 8yrs + of IUD or bowel surgery

Question 37

actinomyces lab

Answer 37

biopsy or pus sample contains branching gram + rods with sulfur granules. can be cultured but takes 3 weeks to grow. IF testing available. PCR in pipeline

Question 38

actinomyces treatment

Answer 38

long course of penicillin G may suffice. surgical draining of nodule may be needed