med microbio MODULE 12. ANAROBIC BACTERIA

Describe 3 (2nd one brings the first and last together) laboratory identification methods for anaerobes.

• purpose of gram stain and when done in relation to other tests

• what does presence of leukocytes indicate; presence of neutrophils means what type of infection, presence of mononuclear cells means what infection

• what biochemical test ID bac based on metabolic end prod

1. Microscopic exam

   1. First, a direct Gram stain– directly from patient sample– to get idea of what we are handling

      1.  number, types of bacteria

         1.  single organism

         2.  polymicrobic site of infection ( suggestive of anaerobes because doesn't necessarily follow the rule of one microbic to one disease)

      2.  morphology of bacteria maybe suggestive of bacteria present

         1.  Large, barrel shaped gram positive rods with spores is highly suggested of Clostridium

   2. Helps know what to look for and can repeat culture if no growth occurs and can be attributed to error

   3. Presence or absence of leukocytes: suggestive of host response to infection

      1.  presence of neutrophils suggests acute inflammation

      2.  presence of mononuclear cells such as lymphocytes, monocytes, macrophages suggest chronic infection or inflammation 

2. Bacterial identification

   1.  correlate gram stain, presence or absence of leukocytes with culture results to provide a complete and cohesive final report to the attending physician 

3. First grow organism on plates→ then ID organisms by biochemical testing

   1.  gas liquid chromatography is used to ID anaerobic bacteria based upon their metabolic and products

      1.  use a control sample that has all anaerobic and products and compare to Patient sample

      2.  Vitek 2 can also be used to ID anaerobes

Define “anaerobic bacteria” and relate “anaerobic” to oxidation-reduction potential (Eh) of body tissues.

• why is O2 poisonous to some bac

• Eh measure what

• dec [O2] means what Eh

• blood Eh vs anaerobic pref Eh

• Molecular oxygen itself can be toxic to some anaerobes, but substances produced when oxygen becomes reduced or even more toxic→ during oxidation reduction reactions, molecular oxygen is reduced in a stepwise manner by the addition of electrons as shown here:

• Anaerobic bacteria don't have enzymes that act on the reduced oxygen species

  • aerobic bacteria have superoxide dismutase and glutathione peroxidase catalase that eliminate ROS (catalase test that detects H2O2→ O2 + H2O)

• hydroxyl radical is the most toxic because it can't move far from the location it was formed and thus causes severe damage to that location

• Atm req: anaerobic bac are those for which O2 is either inhibitory or toxic (varying degree of anaerobism; some can tolerate, some not at all)

• anaerobic bac are those that req low ox-red potential (Eh)

  • “Measure of amt of available O2”

  • Inc [O2]= inc Eh; dec [O2]= dec Eh

  • Expressed in mv from -400 to +400 mv

  • Anaerobic bac grow best at Eh of -400–150 mv

  • Eh necessary for growth of anaerobic bac varies w the organism (one may grow at an Eh value a diff bac doesn’t)

• Circulating blood has an Eh range of +125→+250 mv (which approx the range w/in tissues)

  • Most anaerobic bac won’t grow in these conditions

  • Regions that do support growth of anaerobic bac are: intestinal lumen, necrotic tissue, abscess cavities, microenv

• Many areas of the body (skin, lungs, mouth, teeth) appear to be hostile env for anaerobic bac due to O2 abundance, however, anaerobic bac are present due to microenv

Distinguish between exogenous and endogenous means of acquiring anaerobic infections and identify examples of each.— 2 reasons for endogenous infect; only 1 example/reason for exogenous

1. exogenous– acquired from source outside the body: 

• Trauma: soil contam of wound site, human or animal bite (mouth of human or animal has large amt of normal anaerobic flora); anaerobes tend to be rez to antimics and difficult to manage

2. Endogenous– acquired from source inside the body:

• Regions of the body where anaerobic bac survive are intestinal lumen, necrotic tissue, abscess cavities, microenv

• Abnormal site– intro of an organism into area outside its normal habitat

  • Leakage of intestinal flora leakage (abdom surgery/injury leading to ruptured appendix (intestinal protrusion full of intestinal content–aerobic and anaerobic bad) spilling fecal contents into peritoneal cavity (supposed to be sterile)

  • Tooth extraction–see tooth surface, gingival crevice, saliva

  • Aspiration of oral contents or vomit (gastric aspiration)

  • Genital tract surgery or trauma–endocervix and vagina

• Reduced ox-red potential of tissue 

  • Usually associated with altered immune response of host

  • The body’s major defense against anaerobic infection is the normal tissue oxidation red pot of +120 mv or greater

  • Most anaerobic bac req lower Eh around -200 mv

State the two major groups into which anaerobic bacteria are classified (spore-forming or non-spore-forming).

• which bac genus is all spore forming and why

• All clostridium are spore forming, but not many other bac are

  • Mechanism of survival esp in harsh environments

Compare the relative number of anaerobic bacteria to the relative number of facultative bacteria in respect to normal flora.

• ratio and which bac predom in normal flora

• bc of this, are anaerobic infect communicable? 

• Anaerobic bac constitute the predom part of our normal flora; anaerobes outnumber facultative bac of the GI 1000:1

  • Bc of this endogenous characteristic, anaerobic infect are usually non communicable but are usually associated with altered host defenses

• Saliva 1:1

• Tooth surface 1:1

• Gingival crevice 1000:1

• Colon 1000:1

• Endocervix 3-5:1

• Vagina 3-5:1

Generally, describe the type of clinical specimens that would be appropriate for anaerobic culture. Describe those that are inappropriate and state why (4—and which stool sample bac species is exception).

Since medically significant anaerobic bacteria constitute a major portion of the normal flora, clinical specimens are usually considered meaningless unless taken from a site that is normally sterile:

•  normally sterile body fluids such as plural, joint, CSF, blood

•  surgical specimens such as ovarian cysts, tissue sections

•  wound / abscess aspirates

•  transtracheal aspirates

• Biopsies

• Essentially any body part that should be sterile and has presence of bacteria 

Inappropriate specimens: 

• Expectorated septum (Coughed up from lungs and thus travels through the mouth so it picks up bacteria and we wouldn't know if it came from the mouth or lung)-- contains an abundance of normal flora which decreases the chance of recovering anaerobic pathogens if present

•  swabs from superficial sites ( wounds / vagina)-- Arabs tend to be in microenvironments which are deeper, would primarily recover aerobic organisms

•  voided urine– chance of contamination with normal skin Flora is great

•  stool– has abundance of normal facultative, anaerobic, aerobic Flora

  • * notable exception= stool samples appropriate for anaerobic culture of Clostridium difficile infection 

Handling and specimen collection: 4 ways of transport/isolation mech, optimal temp

Handling and specimen collection

• Special transport in isolation media that are pre-reduced ( already anaerobic environment because of special packaging), anaerobically sterilized are required for successful transport of samples from bedside to laboratory to isolation to ID of pathogenic microbe

  • Pre-reduced anaerobically sterilized plated media (PRAS)

  • Commercially avail anaerobic bag (no pores)

  • Anaerobic jars (smaller hosp)

  • Glove box (larger hosp, can handle more plates and has internal gloves to allow anaerobic handling)

•  temperature– it is desirable that a minimum amount of time be allowed for specimen to be exposed to room temperature: recovery of anaerobic bacteria is best at 37° C;  don't want a dramatic change in temperature because if bacteria dies, we can't culture and would miss ID

•  maintenance of anaerobic conditions is required for successful culture of anaerobes: 

  •  anaerobic chamber, and aerobic jar /bags

  •  when taken out of body to aerobic conditions, decrease this amount of time

Discuss what is meant by “polymicrobic disease” and how it relates to anaerobic bacterial infections.

• Infections due to anaerobic bacteria are commonly associated with localized, necrotizing abscesses, Each of which may yield up to 13 different species of bacteria

•  because of the multiple species present at the site, the term polymicrobic disease is used to refer to anaerobic bacterial infections→ presence of multiple microbes in saliva from a bite

•  therefore diseases caused by anaerobic bacteria are in sharp contrast to the “ one microorganism– one disease” Concepts that characterizes many infections, such as typhoid fever, cholera, UTIs 

Describe a microenvironment and its importance to anaerobes—how can they survive in it; dental plaque example

A closer look at the skin and lungs reveals a microenv formed by crevices and pits in the tissue surface from which O2 is excluded

• This microenv provides req for a low Eh and thus anaerobic bac may be present

• Low Eh possible (ex: periodontal pocket has Eh -50 mv and dental plaque Eh= -200 mv

• the deeper the probe, the lower the O2 content of the pocket

Dental plaques: 

• Biofilm-associated

• Normal gingiva: healthy gums and bone anchor teeth firmly in place

• Gingivitis: plaque and its byproducts irritate the gums, making them tender, inflamed, and likely to bleed

• Periodontitis: unremoved, plaque hardens into calculus (tartar); as plaque and calculus continue to build up, the gums begin to recede from the teeth and pockets from between the teeth and gums

• Advanced periodontitis: gums recede further, destroying more bone and the periodontal ligament; teeth–even healthy ones– become loose and need to be extracted

List and recognize the clinical clues associated with anaerobic infections (6)

• Because anaerobic bacteria are often difficult to isolate (because of specialized techniques necessary), certain clinical clues are helpful for the clinician and recognizing anaerobic infections:

  • foul smelling / putrid odor of discharge (especially in burn patients)

  •  necrotic tissue (tissue dying at such a fast rate the body can't remove in thus results in stacking of dead tissue), gangrene

  •  gas and tissues or to discharges

  •  dark color of blood- containing exudates

  •  polymicrobial flora

  •  failure to grow aerobically in the lab 

Describe the morphology of B. fragilis when Gram stained.

• how common is it isolated

Most commonly isolated anaerobic bacteria in the genus bacteroides

•  Gram-negative bacilli ( rod)

• Bacteroides fragilis is the most commonly isolated anaerobic bacteria

•  more than half of anaerobes isolated

what is most commonly isolated anaerobic bac

C. Bacteroides fragilis

Classify B. fragilis as non-spore-forming or spore-forming and state its normal location. (normal flora in what 4 places)

• opportunistic or obligate patho

• common endogenous infection where

• isolated from indiv w?

• Non spore forming

•  is abundant and normal flora, especially in the intestinal, genital urinary, and upper respiratory tracts, as well as the mouth

  •  is an opportunistic pathogen– in the right conditions

  • Common endogenous source of infection is intestinal tract (feces)

•  isolated from individuals with:

  •  mixed infections and tissue necrosis

  •  mucosal ulcers, lung abscesses, brain abscesses

  •  abdominal surgery complications

  •  liver abscess

  •  diabetes mellitus related ulcers

  •  Malignancies

  •  basically anywhere where it gets out of the normal flora

Relate B. fragilis bacteremia to endotoxic shock.

• what do these infections typically lead to (2)

Due to being gram-negative, cell wall has endotoxin capabilities

•  infections are often associated with both tissue necrosis and septicemia

•  septicemia results in blood clot formation and release of endotoxin, producing endotoxic shock and possible death

Identify consequences of use of bactericidal antimicrobics for treatment of infection.

• As is true for all gram-negative infections being treated with antibacterial agents, especially bactericidal drugs, bacterial killing leads to release of endotoxin which can lead to endotoxic death and shock 

Describe hyperbaric oxygen therapy as a treatment option.

• which bac and infection is it used for typically

• its first applications

• B. fragilis— abscesses, soft tissue infections and diarrheal illnesses (endogenous intestinal patho)

• HBOT is intermittent treatment of the entire body with 100% oxygen at greater than normal atmospheric pressures

  • Significantly increases arterial and tissue oxygen tension 

  •  the O2 rich environment is lethal to anaerobes

•  patient is placed in a pressurized chamber and administered 100% O2, thereby producing a high O2 therapy that has been effective in some cases by directly inhibiting growth of anaerobes

  • however, results of controlled studies for this application of HBOT is not available

•  was first used to recompress divers

•  later, HBOT was used to treat gas gangrene (clostridium infection)

•  HBOT was first used to assist wound healing when it was noted in 1965 that burns of victims of a coal mine explosion treated with HBOT for their CO2 poisoning healed faster

•  there have been reports of HBOT enhancement of wound healing processes including increased host defense against infection, increased rate of killing of bacteria by phagocytes, and potentiation of antibiotic effects

•  in addition, HBOT alone is bactericidal for certain anaerobes

Describe treatment options for anaerobic infections.

• rel susceptibility to antimic

• is there a gold standard treatment option?

• 2-step treatment (second step has 2 options)

• what must be watched for in terms of bactericidal action

Treatment– options are limited

• Surgical drainage/resection of necrotic tissue at the site, in conjunction with:

•  supportive antimicrobic therapy

  •  early administration of antimicrobials is imperative, however anaerobic bacteria tend to be very resistant

  •  no gold standard for susceptibility testing of anaerobic bacteria– treatment strategies frequently rely upon previously reported sensitivity results of antibiograms from hospitals that perform susceptibility testing; CDC recommendations and published antimic sus results also used

  • Be aware that too much bactericidal action can lead to endotoxin shock and death

• Use of hyperbaric oxygen therapy

Classify Clostridium species as non-spore-forming or spore-forming anaerobes.

Describe the morphology of Clostridium species when Gram stained.

spore-forming

Gram positive rod with a spore 

State the source (2) and mode of transmission (2) of the Clostridium species.

• what disease has had reports of spontaneous occurances

• 2 body locations (and the general one)

• risk population

• soil, intestinal tract

• clostridium species have been isolated from mucous membranes of humans, such as the GI tract and also may colonize the skin

• infection occurs when contaminated soil is introduced to a wound or when fecal material escapes from the intestines as in abdominal trauma or surgery

  • farmers and gardeners at risk

• there are reports of spontaneous gas gangrene occurrences

State the clinical condition and symptoms of C. perfringens infection.

• ca of what main disease state

  • 2 names

• fatality

• hallmark symptom mechanism

• source and clinical infection of food poisoning

  • symptoms and duration of incubation and illness

  • is it self limiting?

  • are antibi needed?

• C. perfringens is the causative agent of clostridial myonecrosis (gas gangrene)

• The terms gas gangrene and clostridial myonecrosis (muscle tissue destruction) are used interchangeably and referred to infection of muscle tissue by toxin-producing clostridia 

• Gas gangrene is one of the most fatal infections

  • without treatment, gas gangrene is fatal within 48 hours

  •  with treatment, reported mortality rates vary widely from as low as 25% in recent studies to 100% in patients with spontaneous development of gas gangrene or with patients of delayed treatment

• Clinical infection 

  • Introduction of C. perfringens into tissue

  •  bacteria multiplication

  •  gas production, accumulated gas tears tissue apart, tissue death (necrosis) follows, disease is rapidly progressive with involvement of more tissues, amputation may be performed to stop the progressive spread of infection, death 

  • Is a severe form of of tissue death that generally occurs at a wound or surgical site causing painful swelling (not just from edema inflammation response, but bc of gas buildup that blows muscle tissue/ separates fibers apart) and destruction of involved tissue

• Food poisoning

  • Source

    • Ingestion of enterotoxin-producing C. perfringens in contam food (implicated foods are beef, poultry, gravy, fish)

  • Clinical infect

    • 8-22 hr incubation period

    • Patient experiences diarrhea, cramping, abdom pain for 24 hrs

    • A rel mild and self-limiting GI tract illness

    • treatment= fluid replacement, usually other therapy is not needed

what clostridium bac species can cause food poisoning

C. perfringens, tetani, botulism, difficile

C. perfringens

State the mechanism of the disease C. perfringens produces.

• what allows for necrotizing properties (fermentation of___)

Toxin

•  production and release of at least 20 exotoxins, many of which have necrotizing and/or tissue dissolving properties (ferments muscle sugars)

• additionally, hydrolysis of key cell membrane components occurs causing lysis of erythrocytes, leukocytes, platelets, fibroblasts and muscle cells

• some of the exotoxins are lethal

Discuss the laboratory diagnosis of gas gangrene.

• gram stain

• hemolysis

• litmus milk

• lecithinase test

• Gram pos rod with spore

• Double zone of beta hemolysis on blood based media

  • Grows on BAP
    First zone it total clearing, second with less clearing

• “Stormy fermentation” in litmus milk

  • Changes color from blue to pink bc pH change (ferments milk so more acidic)

  • Acid and enzymes coagulate in proteins in the milk and gas tears the curds apart–”stormy” bc of clumps

• Lecithinase positive 

  • White halo on egg-yolk agar

Discuss treatment strategies for gas gangrene.

• clinical

• antibi

• pain control

• HBOT?

• Prompt surgical removal of dead, damaged, and infected tissue by debridement

• Amputation of an arm or leg may be indicated to control spread of infection (ex: diabetics with foot ulcers that do not heal and infection progresses up the leg)

• Antibiotics, usually one of the “cillins”, are given with initial treatment admin IV

• Analgesics may be req to control pain

• Hyperbaric oxygen has been tried w/ varying degrees of success

State the clinical condition associated with infection with C. tetani.

• affects what body system

• another name

• what leads to death

• spores? toxins? 

• transmission/ contagious? 

• clinical course

Tetanus

• Disease caused by C.tetani that affects the nervous system 

• Contracted through a cut or wound that becomes infected with tetanus bacteria– bacteria get in through scratch, deep puncture wound, like those made by nails or knives, are susceptible to infections with tetanus

•  bacteria are present world– commonly found in soil, dust, manure

•  Infection causes severe muscle spasms needing to locking up the jaw so the patient cannot open mouth or swallow

  •  hence the name lockjaw 

• May lead to death by suffocation

•  not transmitted from person to person

• Clinical infection: 

  • Spores (main way organism survives bc can in bad env) or bacteria enter the wound: spores germinate

  •  bacteria multiply at wound site with no Invasion into deeper tissue

  •  toxins are produced

  •  muscle spasms occur

Identify the toxins associated with pathogenicity of C. tetani and state their mechanism of action. (2)

• which one causes muscle spasms, which one is a cytolysin

• Pathogenicity is due to 2 powerful toxins:

  • tetanospasmin= cause of tetanus and sometimes called tetanus neurotoxin, acts on the CNS by blocking release of inhibitory neurotransmitter

    •  this is what causes muscle spasms because muscles can't relax

  • tetanolysin=a cytolysin that increases permeability of cell membranes– lysis erythrocytes (RBS) and injures the heart 

Describe the characteristic symptoms associated with the C. tetani.

• when begin

• common first signs

• characteristic symp

• Symptoms usually begin 8 days after infection, but maybe 3 days- 3 weeks

•  common first signs of tetanus are:

  •  headache and muscular stiffness in the jaw (lockjaw)

  •  stiffness in the neck

  •  difficulty and swallowing

  • Sweating

  • Fever

  • Rigidity of abdom muscles

  • Spasms

    • Triggered by auditory and visual stimuli

    •  muscles spasming all over body and at same time 

    • Characterized by violent rigidity with all voluntary muscles in the body going into a contraction state:

      • Flexion of arms, extension of legs, clenched jaw (lockjaw), arched back

    • Spasms may be so intense as to cause bone fractures

    • If diaphragm contracts and chest becomes fixed and rigid, respiration may cease and death follows

    • Released from inhibition, muscles–even opposing members of a muscle group (extensor and flexor)–recieve constant stimuli and contract uncontrollably

    • Muscles contract spasmodically without regard for regulatory mechanisms or conscious control; clenched jaw typical of risus sardonicus (distorted grin)

    • Tetanospasmin signaling goes to brain

Tetanospasmin action

• is cause of most symptoms in tetanus

• Bacteria is noninvasive, but it secretes toxins that spread

• Blocks release of inhib neurotransmitter 

diagnosis of tetanus

• relies heavily on what

• morpho of bac

Diagnosis 

• Relies heavily on clinical presentation

• Lab diag: isolation of anaerobic GPR with terminal spores (tennis racket shape) isolated from wound site

State the recommended time period for adults to receive booster vaccinations against diphtheria, pertussis, tetanus (DPT).

• major number of tetanus cases (age grp)

Prevension:

• Immunization with a tetanus toxoid is included in the DPT (diphtheria, pertussis, tetanus) series

• After initial 4-yr booster, immunity is maintained by booster shots every 10 yrs

• Major number of cases occurs in patients over 60 years of age

Treatment tetanus:

active vs passive immune, antibi and/or antitox, meds (2) for symp management, how to removes spores

• Cleansing of wounds to remove spores

• Passive immunotherapy (injection of tetanus antibodies and antitoxins) with HTIG–human tetanus immune globulin

• Active immunization (had disease and dev immune response for further protection) with tetanus toxoid (DTap vacc)

• Antibiotics: control infection but have no effect on toxins so must be used in conjunction with tetanus-specific antitoxin (target symp cause)

• Barbiturates may be used to reduce severity of spasms

• Medications that paralyze muscles may be admin to allow ventilation/respiration of patient during severe spasms

State the means by which man contracts botulism food poisoning.

• common sources (2)

• symp time to appear

• Due to ingestion of toxin

• Common sources: home-canned vegetables, meats

• Symptom appear 2-36 hrs after ingestion (toxin so fast)

botulism agent, source, types

• which types (2) is toxins prod in vivo

  • focus when comparing the 3 types on how infection is acquired

agent= C. botulinum

source= soil, decaying vegetation, contam food

Clinical infect: types

• Food botulism

  • Due to ingestion of toxin

  • Common sources: home-canned vegetables, meats

  • Symptom appear 2-36 hrs after ingestion (toxin so fast)

• Infant botulism 

  • Due to ingestion of spores that germinate in the colon causing production of toxin in vivo

  • Common source is contam honey (adults wont get even if eat same honey bc immune response dev; wind blows contam dust into beehive)

  • Usually infants under 6/12 mo–most common cause in US

  • Death rate is <1% of hosp children

• Wound botulism

  • Due to contamination of wound with spores (into open wound), bacteria germinates, produces toxin in vivo

Relate neurotoxin to mechanism by which C. botulinum causes botulism

• prev release of what

• normal state vs infected state

• how dangerous is toxin

  • special classification

pathogenicity= neurotoxin

• Botulinum is a neurotoxin that prevents release of acetylcholine

• Its effects are characterized by sudden onset, rapid disease course, muscle paralysis, and pulmonary arrest 

• In normal state, Ach released at the synapse crosses to the muscle and creates an impulse that stimulates muscle contraction; 

  • in botulism, toxin enters the motor end plate and attached to the presynaptic membrane where it blocks release of neurotransmitter, prev impulse transmission, and keeps muscle from contracting

• Most potent toxin known: 1 oz has the ability to kill the entire pop of the US

• Botulinum tox is classified as an agent of biological warfare

Medical use of botulinum toxin:

• what is basis for med use

• 2 eye-related cond that can be treated with it

• 2 names 

• Small doses of the toxin are injected into affected muscles

• As happens w botulism, toxin binds nerve endings and blocks release of Ach, which would otherwise signal the muscle to contract

• The toxin paralyzes or weakens the injected muscle but leaves other muscles unaffected

• Purified botulinum toxin is the first bac toxin to be used as a med

  • FDA licenced botulinum toxin as Oculinum in 1989 for treatment of 2 eye cond:

    • blepharospasm= spasm of orbicular muscle of eyelid, characterized by invol closing of the eyes

    • strabismus= deviation of visual axes (cross-eyedness), characterized by excessive muscle contractions

  • Is now marketed under “botox”--botulinum toxin

List two mechanisms by which botulism can be prevented.

1. Proper food processing that destroys spores: home canned food prod are treated at 120 deg C, 15 lbs of pressure for at least 15 min (similar to autoclave which can kill both spores and bac)

   1. High acid foods can use a water bath or pressure canner according to FDA bc acid helps kill some bac

   2. Cans can swell bc of gas production of bac→way to tell if botulism is present

2. Inactivate toxin by boiling food, esp home canned food (inactivates toxin) for 10 min before eating

Briefly describe the major manifestations of botulism from onset to death.

• early (4), mild (3), late (4)

• when do distinct symps begin

Early:

• Severe nausea, vomiting, weakness, dizziness, constipation

Mild: when distinct C. botulism symps begin

• Diplopia (double vision)

• Dysphagia (diff swallowing)

• Dysphonia (diff speaking–slurred speech)

Late:

• Muscle weakness, esp in neck and extremities

• Weakness of resp muscles (such as the diaphragm)

• Paralysis and resp failure

Explain why an antitoxin is administered as treatment for botulism as opposed to treatment with antibiotics.

• mortality botulism if untreated

• antibi for infant and wound botulism

• what neutralized the tox

• Admin of immunoglobulins (passive immun with preformed antitox) neutralize the tox (BIG-IV)

• Washing of the intestinal tract to remove Clostridium 

• Antimic drugs to kill bac

  • For infant and wound botulism, penicillin is usually effective

• Admin antitoxin and antibi to address symptom and what is making/ releasing thing that causes symps (toxin), with supportive therapy such as respiratory monitoring

• If untreated, mortality rate is 100%

Clostridium difficile—Correlate the organism with disease incidence.

• common and clinical disease name

C. difficile is the most common cause of pseudomembranous colitis

• Aka Antibiotic-associated diarrhea

Relate toxin production of C. difficile to disease symptoms

• 2 toxins and what they cause

• clinical infect symps (3-4)

• Patho is due to 2 tox:

  • Toxin A: enterotoxin that causes diarrhea

  • Toxin B: cytotoxin that causes necrosis of intestinal mucosa

Clinical infection:

• Severe abdom pain

• Bloody diarrhea, necrosis of mucosa

• Colonic mucosa covered w/ fibrinous pseudomembrane (shiny appearance)

  • Multiple pseudomembranous lesions

Lab diag c. dificile

• specimin

• mic exam looks for what cells and morpho (spore location as well)

  • how is this diff from other clostridium

• culture on what media and cond

• antibi treatment of choice and why

Lab diag:

• specimen= fresh stool sample

• Microscopic exam of fresh stool

  • Presence of inflam cells and RBC

  • Presence of long, thin, gram pos rods with subterminal spores (as opposed to round, barrel shaped GPR common in genus clostridium)

• Culture:

  • Culture in strict anaerobic cond

  • Culture on selective and diff media: prereduced cycloserine-cefoxintin egg yolk fructose agar

• treatment= vancomycin

  • Rarely first choice bc of side effects, but usually only one effective in c. diff patients

Identify the cause and source of C. difficile infections.

• Constituent of normal intestinal flora in 20% of adults

• Antibiotic therapy shifts balance of intestinal flora and c. diff becomes predom organism in GI tract (then becomes infection)

  • Usually get bc of antibi use and its rez therefore must use vancomycin bc rez to most other antibi

barrel-shaped gram pos rods w spores are highly sugg of ___ genus (anaerobic)

clostridium 

most common lab test to ID anaerobic bac to genus and species

gas-liquid chromatography

common endogenous source of infect of B. fragilis

intestinal tract (feces)

does c. tetani invade tissues deep or superficially stay on wound, with toxins spreading?

superficial

what 2 types of botulism is tox produced in vivo

infant and wound botulism

bc anaerobes predom normal flora, what does this mean ab transmisability

mostly endogenous infect that is noncommunicable

what topical symp is anaerobic bac infections commonly associated w/ (rel numbers of species present)

localized, necrotizing abscess w multiple species present

what is notable exception for anaerobic stool sample that is inappropriate for most, but not this one species

Clostridium difficile

is the bac or tox what is dissem through body in anaerobic infections

tox

what are barbiturates

used to dec spasm severity in tetanus

what is BIG-IV

what is HTIG

antitoxin for botulism

tetanus immunoglobulin (passive immun)

which clostridium diarrheal disease is typically bloody bc cytotox

C. diff