CAMP Test For The Identification Of Streptococcus Agalactiae (group B). 

Another Harry Potter Mnemonic (yayyy!!!)

So, whenever I read about this fungi Sporothrix schenckii I think about Bellatrix Lestrange… geti it? 

Sporothrix - Bellatrix

That evil deatheater that killed Sirius Black. But they actually got it wrong in the movie, she doesn’t “Avada Kedavra” him, she just knocked him through that veil where you could hear death people….

Ok, enough with the Harry Potter fact.

To diagnose an infection from Sporothrix schenckii, you have to see this cigar shaped yeasts (from the pus of the lesions), which are the tissue form of the fungi. 

So to remember this, just picture:

“Bellatrix Lestrange smoking a cigar”

(Sporothrix: cigar shaped yeast in pus)

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MRS.  V.Z.  FYI  MAP

M umps / M easles

R ubella

S mallpox

.

V aricella Z oster

.

F rancisella tularensis

Y ellow Fever

In fluenza (intranasal)

.

M icobaterium bovis (BCG)

A denovirus

P olio (sabin)

Antibodies (Human)

The ‘foot’ (bottom) of the antibody is known as the Fc fragment - binds to cells, binds to complement = effector function (kills or removes antigen)

The top (antigen binding) is the Fab fragment

Chains are held together with disulphide binds

Associated molecules allow intracellular signalling 

Normally 3X constant heavy chain domains per chain and a hinge region (except μ and ε which have 4 and no hinge region)

Classes of Immunoglobulins

The five primary classes of immunoglobulins are IgG, IgM, IgA, IgD and IgE,  distinguished by the type of heavy chain found in the molecule. 

IgG - gamma-chains

IgMs - mu-chains

IgAs - alpha-chains

IgEs - epsilon-chains

IgDs - delta-chains.

Differences in heavy chain polypeptides allow different types of immune responses. The differences are found primarily in the Fc fragment. There are only two main types of light chains: kappa (κ) and lambda (λ), and any antibody can have any combination of these 2 (variation).

IgG 

monomer

Gamma chains

70-85% of Ig in human serum. 

secondary immune response 

only class that can cross the placenta - protection of the newborn during first 6 months of life

principle antibody used in immunological research and clinical diagnostics

21 day half life

Hinge region (allows it to make Y and T shapes - increasing chance of being able to bind to more than one site)

Fc strongly binds to Fcγ receptor on phagocyte - opsono-phagocytosis

Activates complement pathway

IgM

Serum = pentamer 

Primary immune responses - first Ig to be synthesised

complement fixing 

10% of serum Ig 

also expressed on the plasma membrane of B lymphocytes as a monomer - B cell antigen receptor

H chains each contain an additional hydrophobic domain for anchoring in the membrane

Monomers are bound together by disulfide bonds and a joining (J) chain.

Each of the five monomers = two light chains (either kappa or lambda) and two mu heavy chains.

heavy chain = one variable and four constant regions (no hinge region)

can cause cell agglutination as a result of recognition of epitopes on invading microorganisms. This antibody-antigen immune complex is then destroyed by complement fixation or receptor mediated endocytosis by macrophages.

In humans there are four subclasses of IgG: IgG1, IgG2, IgG3 and IgG4. IgG1 and IgG3 activate complement.

IgD 

B cell receptor

<1% of blood serum Ig

has tail pieces that anchor it across B cell membrane

forms an antigen specific receptor on mature B cells - consequently has no known effector function (don’t kill antigens, purely a receptor) (IgM as a monomer can also do this)

IgE 

Extra rigid central domain

has the most carbohydrates

IgE primarily defends against parasitic invasion and is responsible for allergic reactions.

basophils and tissue mast cells express very high affinity Fc receptors for IgE - mast cells then release histamine

so high that almost all IgE is bound

sensitizes (activates) mucosal cells and tissues 

protects against helminth parasites

IgE’s main purpose is to protect against parasites but due to improved sanitation these are no longer a prevalent issue across most of the world. Consequently it is thought that they become over activated and over sensitive while looking for parasites and start reacting to eg pollen and causing allergies.

IgA

Exists in serum in both monomeric (IgA1) and dimeric (IgA2) forms (dimeric when 2 Fcs bind via secretory complex)

15% of the total serum Ig.

4-7 day half life

Secretory IgA2 (dimer) = primary defense against some local infections

Secreted as a dimer in mucous (e.g., saliva, tears)

prevents passage of foreign substances into the circulatory system

Isotype: class of antibody (IgD, IgM etc)

Allotype: person specific alleles 

Idiotype: (hyper) variable region - antibody specificity 

Satellite phenomenon of Haemophilus influenzae around Staphilococcus aureus in blood agar

volutin granules are an intracytoplasmic storage form of complexed inorganic polyphosphate, the production of which is used as one of the identifying criteria when attempting to isolate Corynebacterium diphtheriae on Löffler’s medium….look like chines letters…as given below

Slime mould

Clostridium botulinum

Gram+, anaerobe, spore forming, motile rods

Botulin toxin (botox) inhibits the release of ACh and produces a flacid paralysis.

Adults ingest the toxin from poorly heated canned food (labile toxin, 60° 10minutes): weakness, diplopia, flacid paralysis and respiratory muscles involved, vomiting, diarrhea.

Infants ingest the spore from the dust or honey and form the toxins in the gut: constipation, weak crying, weak feeding, flacid paralysis and rapid respiratory involvement

Wound: traumatic implantation (assoc. w/ IVDA; uncommon), same symptoms without GI symptoms. Debridement, no closure.

Cryptosporidium

Cryptosporidium is a microscopic parasite that causes the diarrhoeal disease cryptosporidiosis. Both the parasite and the disease are commonly known as “Crypto.”

The parasite is protected by an outer shell (oocyst)

Allows survival outside the body for long periods of time 

Very tolerant to chlorine disinfection.

Water is the most common form of spread

Poses serious risk to immunocompromised individuals, eg AIDS; cancer and transplant patients who are taking certain immunosuppressive drugs. 

Symptoms

Symptoms of cryptosporidiosis generally begin 2 to 10 days (average 7 days) after infection. 

Watery diarrhea

Stomach cramps or pain

Dehydration

Nausea

Vomiting

Fever

Weight loss

Some people with Crypto will have no symptoms at all.

Symptoms usually last about 1 to 2 weeks (with a range of a few days to 4 or more weeks) in persons with healthy immune systems. Occasionally, people may experience a recurrence of symptoms after a brief period of recovery before the illness ends. Symptoms can come and go for up to 30 days.

In immunocompromised persons Cryptosporidium infections could possibly affect other areas of the digestive tract or the respiratory tract.

Diagnosis & Detection

Cryptosporidium oocysts in a modified acid-fast stain. (CDC Photo; DPDx)

Examination of stool samples. 

Detection can be difficult - several stool samples over several days.

acid-fast staining, direct fluorescent antibody [DFA] , and/or enzyme immunoassays 

Molecular methods (e.g., polymerase chain reaction – PCR) are increasingly used in reference diagnostic labs,

Treatment

Most people who have healthy immune systems will recover without treatment. Young children and pregnant women may be more susceptible to dehydration resulting from diarrhoea. 

For those persons with AIDS, anti-retroviral therapy (improves the immune status) will also decrease or eliminate symptoms of cryptosporidiosis. However, even if symptoms disappear, cryptosporidiosis is often not curable and the symptoms may return if the immune status worsens.

Cryptosporidium and AIDS

Advanced immunosuppression — typically CD4 T lymphocyte cell (CD4) counts of <100 cells/µL — is associated with the greatest risk for prolonged, severe, or extraintestinal cryptosporidiosis. 

The three species that most commonly infect humans are Cryptosporidium hominis, Cryptosporidium parvum, and Cryptosporidium meleagridis. Infections are usually caused by one species, but a mixed infection is possible.

Up to 74% of diarrhoea stools in AIDS patients demonstrating the organism in less developed countries where potent antiretroviral therapy  is not widely available, 

cryptosporidiosis has decreased and occurs at an incidence of <1 case per 1000 person-years in patients with AIDS.4 Infection occurs through ingestion of Cryptosporidium oocysts. Viable oocysts in feces can be transmitted directly through contact with infected humans or animals, particularly those with diarrhea. Oocysts can contaminate recreational water sources such as swimming pools and lakes, and public water supplies and may persist despite standard chlorination (see Appendix: Food and Water-Related Exposures). Person-to-person transmission is common, especially among sexually active men who have sex with men.

Fever is present in approximately one-third of patients and malabsorption is common. 

The epithelium of the biliary tract and the pancreatic duct can be infected with Cryptosporidium, leading to sclerosing cholangitis and to pancreatitis secondary to papillary stenosis, 

Pulmonary infections also have been reported, and may be under-recognized.

Treatment 

ART with immune restoration to a CD4 count >100 cells/µL usually leads to resolution

Treatment of diarrhoea with anti-motility agents (AIII) may be necessary. 

Patients with biliary tract involvement may require endoscopic retrograde choledocoduodenoscopy for diagnosis. 

Immune reconstitution inflammatory syndrome (IRIS) has not been described in association with treatment of cryptosporidiosis.

No pharmacologic interventions are known to be effective in preventing the recurrence of cryptosporidiosis.

No therapy has been shown to be effective without ART.