Serological testing is based on which principle?

Serological (immunologic) tests are based on antibodies specifically binding to an antigen

How are Ab-Ag reactions measured?

Must be visible or measurable - visible by clumps, precipitates, color changes or release of radioactivity

What substance are you testing if you are testing for the antibody?

What about when you are testing for the antigen?

An isolated colony or swab from the patient that contains antigen

What is specificity?  

able to react with a very small amount of ab or ag 

What are some types of immunologic assays?

Agglutination tests; Precipitation reactions; Immunoelectrophoresis; Complement fixation; Fluorescent antibody tests; Immunoassay tests

A urine pregnancy test is which type of test?

Latex aggultination - latex particles that are coated with the antigen 

What type of sample is used for testing in the RPR, cold agglutinin, and Weil-Felix test?

The patient’s serum – testing for antibodies

What is the difference between agglutination and precipitation?

The size, solubility and location of the antigen – agglutination=whole cells (RBCs) or bacteria; precipitation=the antigen is soluble.  Both will form a insoluble aggregate

What is the tube agglutination test used for?

Determining how many antibodies are in a patients serum – a titer

What is being testing in precipitation testing?

Usually performed in an agar gel medium; Ouchterlony method is a double diffusion method – Ag and Ab are placed in wells in the agar; Antigen and antibody diffuse toward each other, forming a line of precipitate on contact

What are some examples of precipitation tests?

VDRL, oucherlony method, immunoelectrophoresis, western blot

What is complement fixation testing for? 

Can be testing for the antigen or the antibody

What is the visible result if the Ab-Ag complex is present?

There will be NO hemolysis of the sheep RBCs

How is the test interpreted if lysis does occur?

As a negative response – no immune complexes were formed

How is the presence of an immune complex visualized in the fluorescent antibody test?

a monoclonal antibody labeled by a fluorescent dye and interacts with antigens and antibodies

What is the difference between direct and indirect testing with fluorescent antibody testing?

Direct=testing for antigen; indirect=testing for antibody

Give an example of each type (direct & indirect).

Direct – syphilis, gonorrhea, chlamydia, pertussis, plague; indirect - FTA-ABS

What types of tests are RIA and ELISA tests?

Immunoassays - Extremely sensitive testing that permits rapid and accurate measurement of trace antigens or antibodies

What is principle of Radioimmunoassay (RIA)?

RIA - Ags or Abs are labeled with radioactive isotopes and measured

What is the principle of Enzyme Linked Immunosorbent assay (ELISA)?

ELISA - A positive result is visualized when a colored product is released by an enzyme-substrate reaction (Ab or Ag)

Give examples of ELISA testing.

Antibody testing for HIV, Hep A & C, cholera, helicobacter, and rickettsia; antigen testing - useful for measuring nanogram (ng) amounts of hormones, drugs, and serum proteins

Which test is useful in following HIV patients?

Specific testing for CD4 and CD8 t-cells

Which test is an example of in vivo testing?

TB skin testing - PPD

Which types of cocci bacteria are the most clinically important?

Staph, strep and neisseria.

Which are gram positive and gram negative?

Staph and strep; neisseria 

What test will differentiate staph species from streptococcus species?  Which one is positive?

Catalase – staph is catalase positive

What species appears as gram + cocci in chains?  Gram + cocci in clusters?

Streptococcus

staphylococcus

 Why are cocci called pyogenic?

They produce pus

 What substance aids S. aureus in tissue destruction?

Hemolysins – most alpha

Where is S aureus isolated from in patients who are carriers of the organism?

Anterior nasal pharynx (nares)

What are some local diseases that are caused by S. aureus?  Systemic?  Toxic diseases?

Localized – abscess, folliculitis, furuncle, carbuncle, impetigo

Systemic – osteomyelitis, pneumonia, meningitis, bacteremia

Toxigenic disease – food poisoning, scalded skin syndrome, toxic shock syndrome

You have a 2 y/o patient with yellow blisters and some erythema on his arm – what is the DX and the bacterial agent?

Bullous impetigo – S. aureus 

 What substance is responsible for food poisoning from S aureus?

Enterotoxins

What substance is responsible for a painful bright red rash occurs over the entire body then causes desquamation of the epidermis?

Exfoliative toxin

 Which species of staphylococcus can cause wound infections?

S. aureus, S. epidermidis, S. hominis, S capitis 

Which species of staphylococcus can cause UTI’s especially in sexually active adolescent females?

S. Saprophyticus 

Are penicillins effective against staph infections?  Why?

No – they produce penicillinase 

 What is a common initial presentation of MRSA? 

“spider bite” or small pimple type lesion

 What types of classification systems are used for streptococcus species?

Lancefield and the hemolysis reaction on blood agar

Which species are Beta hemolyic?  

Alpha hemolytic?

A,B,C,G & some D strains;

S. pneumoniae  and the viridans group

Which strep species causes the most serious disease?  Why?

Group A (S. pyogenes) – enzymes and toxins

What are some diseases caused by strep Gp A?

Pharyngitis, scarlet fever, impetigo, erysipalis, necrotizing fasciitis, pneumonia, rheumatic fever, glomerulonephritis 

Why is Gp B streptococcus medically significant?

May cause premature delivery of the fetus and neonatal septicemia, meningitis and pneumonia

Why is the viridans group of bacteria medically significant?

May cause subacute bacterial endocarditis 

What is the most common pathogen of bacterial pneumonia?  What else is it commonly seen in?

S. pneumoniae; otitis media

What is unique about the structure of S. pneumoniae?

Several strains form capsules providing virulence

Are there vaccines available for S. pneumoniae?  Which ones?

The capsular vaccine is for older patients and the new conjugate vaccine is for children.

Describe the gram stain results from the discharge in a patient with gonorrhea.

Intracellular gram negative diplococci 

What other disease commonly occurs with gonorrhea?

Chlamydia 

 What is a serious disease seen in neonates born to moms with gonorrhea?  How is it prevented?

ophthalmia neonatorum – antibiotic eye drops given at birth to all babies

What is meningococcus?  Why is it medically significant?

N. Meningitis – epidemic bacterial meningitis - very rapid onset; endotoxin causes hemorrhage and shock; can be fatal quickly. 

A 45 y/o male is complaining of fevers/chills, productive cough, and pleuritic chest pain.  On exam, he has crackles/rales in his LLL.  What is the most likely bacterial pathogen?

S. Pneumoniae 

What type of skin lesions may be seen with bacterial meningitis?  Why does it occur?

Endotoxin causes vascular collapse, hemorrhage, clotting disorders and visible petechiae on the body.

Which species of bacteria form endospores?

Bacillus spp and Clostridium spp 

What is the causative agent of anthrax?  

Bacillus anthracis 

What form of anthrax is most common and the least pathogenic?

Cutaneous anthrax

Describe a lesion of cutaneous anthrax.

Starts as a papule that becomes necrotic which ruptures and becomes a painless black eschar 

What is the major pathogenicity of pulmonary anthrax?

Exotoxins that produce toxemia which results in capillary thrombosis and cardiovascular shock.  Death can occur in a few hours.

How is it treated?  Is there a vaccine?

Treated with penicillin or tetracycline which is effective against the bacteria however does not resolve the effects of the toxins. Vaccine – purified toxoid given in 6 injections over 1.5 years with annual boosters

What are the 2 forms of illness seen with B. cereus?

Emetic form and diarrheal form

What is the causative agent of gas gangrene?  What type of environment is needed for optimal growth?

C. Perfringens 

What causes the RBC rupture, edema & tissue destruction seen in gas gangrene?

Alpha toxin

How can it be prevented?

rigorous cleansing of wounds, decubitus ulcers and surgical sites

C. Difficile 

Treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow - Produces entertoxins that damage intestine – necrosis of the intestinal mucosa

Clostridium tetani ; Tetanospasmin 

Tetanospasmin stops the inhibition of contractions resulting in uncontrollable severe muscle contractions

How is tetanus treated?  Is there a vaccine?

Antitoxin – tetanus immune globulin (TIG); PCN or TCN and removing infected tissue; Vaccine – 5 doses during infancy/childhood with boosters every 10 years

What is the causative agent of botulism?  What 3 diseases are caused by this agent?

Clostridium botulinum – food poisoning, infant botulism, wound botulism

What is the most potent microbial toxin known?  How does it cause disease?

Botulin - prevents the release of acetylcholine preventing muscle contraction – death occurs from respiratory compromise

Is there a vaccine for botulism?

No vaccine available

What types of patients are most susceptible to Listeria monocytogenes?

immunocompromised patients, fetuses (mother infected and passes through the placenta harming fetus) & neonates

What is the causative agent of erysipeloid?

Erysipelothrix rhusiopathiae 

Corynebacterium diptheriae 

What physical exam findings may be seen with diphtheria?

sore throat, enlarged lymph nodes and severe swelling of the neck – Pseudomembrane of the oropharynx 

What is the causative agent of acne?

The Mycobacteria species have which type of staining properties? 

 Which Mycobacteria species causes TB?  Leprosy?  Pneumonia in HIV patients?

Mycobacterium tuberculosis, Mycobacterium leprae, Mycobacterium avuim-M. intracellular complex

If a patient is exposed to TB, what is the likelihood that he will get the disease?

Only 5% infected people develop clinical disease – generally humans are resistant to TB

 Which organs may be affected by TB?

Majority of cases (85%) are pulmonary but can occur in any organ of the body

What type of lung lesions may be seen in TB?

What is secondary TB?

What is the screening test for TB?  What are some other tests?

tuberculin skin testing, Chest x-rays, Direct identification of acid-fast bacilli in specimen, Laboratory cultural isolation

What are some contraindications to PPD testing?

previous + reactions, history of BCG vaccine

Is the PPD test reliable in all patients?

 Which medications are used for the treatment of TB?  Is there a vaccine?

 How is M. Leprae cultured?  What are the 2 forms of the disease?  Which is worse?

Which areas of the body are more prone to disfiguring lesions of leprosy?

What type of neurological symptoms are seen in leprosy?

 What causative agent is involved with a complication of tooth extractions, necrotizing lung disease, peritonitis after trauma, ulcers and appendicitis?

What causative agent is causes a lung disease very similar to TB?

Which gram negative bacilli are aerobic?  Which of those are opportunistic pathogens?

What are some of the diseases caused by pseudomonas species?  Is it easy to treat?

What is the causative agent of undulant fever?  How is it contracted?

What is the causative agent of tularemia?

What is the causative agent of pertussis?  What are the 2 phases of the disease? 

Why is the incidence of pertussis increasing?

What is the causative agent of Legionnaires disease & Pontiac fever?  What is a common reservoir for this agent?

What are some of the clinical features of Legionnaires disease?

Which bacterial species are considered enteric pathogens?  Do they cause disease in the GI tract?

What is a coliform?  Non-coliform?

 Which strain of E.coli causes hemorrhagic syndrome & permanent kidney damage?

What are some diseases caused by E.coli?

traveler’s diarrhea, UTIs, neonatal meningitis, pneumonia, septicimia and wound infections

Which coliform causes pneumonia and produces a red pigment?

Which non-coliform lactose-negative enterics are true pathogens?

What is the causative agent of typhoid fever?

Which part of the GI tract is affected by salmonella species?  Shigella species?

What is the causative agent of dysentery?

What is the causative agent of plague?  What is the most common vector for plague?

What the 3 types of plague?  Is there treatment available?  Vaccine available?

Bubonic, pneumonic, septicemic; 95% survival rate with antibiotic Tx; Killed or attenuated vaccine available but only lasts for a few months

What pathogen is implicated in animal bites?

What is the common causative agent of acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, & bronchitis?

What is the causative agent in bacterial conjunctivitis?

                                                               ·      Hemophilus ducreyi

Treponema, Leptospira, Borrelia

1. Treponema had 8-20 evenly spacced coils

Lives in the oral cavity, intestinal tract and perigenital regions of humans and animals, strict parasites that can only be cultivated in live cells

2. Leptospira has numerous fine, regular coils and one or both ends curved

3. Borrelia has 3-10 loose irregular coils

T. Pallidum

Other pallidum subspecies cause yaws and non-vernereal endemic syphilis

Yes

A common characteristic of late congenital syphilis is notched, barrel shaped incisros 

RPR, VDRL, FTA-Abs, dark field microscopy

screening are RPR and VDRL; confirm with FTA-Abs

high doses of penicillin

parental PCN G is the drug of choice in all stages

                                                               ·       generalized lymphadenopathy and rash; flu like symptoms

                                                               ·      About 6 weeks after chancre heals, 2^ndary signs will appear, fever, headache, sore throat, generalized lymphadenopathy and a red/brown rash (doesn’t hurt or itch) on the palms and soles, lesions also have spirochetes present; can affect bones, hair follicles, joints, liver, eyes and brain

neurological symptoms and gummas

tender tumor that can be errosive gumma apears on the nose of the pts 

      What is unusual about the rash of secondary syphilis? 

It can affect the hands and feet and spirochetes are in lesions

It can also be painful or itchy

     What other symptoms may be present?

    How long can the latency period of syphilis be?

Leptospira interrogans

Bacteria shed in urine; infection occurs by contact (not human to human); targets kidneys, liver, brain, eyes 50-60 cases a year in US

Early tx with Penicillin or tetracycline reduces symptoms, vaccine for livesotck workers and military personnel 

an antigenic change occurs and a new immune response occurs causing a fever a few days later

2-15 day incubation; parasite changes and immune system tries to control it

Other sx: high fever, shaking, chills, headache & fatigue, nausea, vomiting, muscle aches, abdominal pain; extensive damage to lover, spleen, heart kidneys and cranial nerves

What is the causative agent of Lyme disease?

What is the vector?

Borrelia burgdorferi

non-fatal, slowly progressive syndrime that mimics neuromuscular and rheumatoid conditions

vectos is blacklegged (or deer) ticks

Fever, headache, stiff neck & dizziness with ccardiac damage, neurological s/x and polyarthritis

Tx: tetracycline or amoxicillin 

Vibrio cholerae

a gram negative rod, comma shaped that possess unique O and H Ags

Ingested with food or water

infects surface of small intesting, non-invasive, cholera toxin causes electrolyte and water loss through secretory diarrhea (rice water stool) resulting dehydration leads to muscle, circulatory and neurological sx

Oral rehydration and tetracycline

vaccines are available

Vibrio vulnificus and Vibrio parahaemolyticus

1. vibrio parahaemolyticus-gastroenteritis from raw seafood, shrimp, tuna, squid, crabs and others

2. Vibrio vulnificus-gastroenteritis from raw oysters, poor outcome in patients with diabetes or lover disease

Heat-liable enterotoxin CJT, one of most common from poultry

C, jejuni is an important cause of bacterial gastroenteritis, incubation period is 1-7 days; it is tranmsitted by food and beverages; once it reaches the muscosa at the ileum near the colon it adheres and burrows through the mucous to multiply

What bacterial agent causes 90% of stomach and duodenal ulcers?

How is it contracted?

H. pylori

Also a factor in gastric adenocarcinomas; natural of human stomach (resistant to gastric acid)

Probbly transmitted from person to person

Patients with type O blood and patients who take NSAIDS chronically 

Produces a large amount of urease which can be measured by a urea breath test 

How is H. pylori diagnosed? 

Tx?

biopsy, breath test or antibody test of serum

Tx: triple therapy provides a 95% cure rate-Proton pump inhibitor/ranitidine+amoxicillin+clarithomycin 

Rickettsia rickettsii

Dog and wood ticks are principal vectors

Ticks are infected from a mammalian reservoir during a blood meal

TRansovarial passage of Rickettsia rickettsii to tick eggs serves as a continual source of infection within the tick population

A tick attaches to a human, embeds its head in the sking, feeds and shreds rickettsias into the bite

Systemic involvement includes severe headache, fever, rash, coma and vascualr damage such as blood clots and hemorrhage 

Southeast and on eastern seaboard not often in the West

Coxiella burnetti

an intracellular parasite that produces an unusal resistant spore

Harbored by a wide assortment of vertebrates and arthropods especially ticks

Transmitted by air, dust unpasteurized milk and ticks 

What is cat-scratch fever?

What is the causative agent?

What are the symptoms?

lymphatic infection associated with a clawing injury by cats

Batonella henselae

a small gram negative fastidious, not obligate parasites and ca nbe cultured on a blood agar

Starts as a small patch of papules then progresses to tender lymph nodes

Elementry body and reticulate body

Elementry body-smallmetabolically inactive, extracellular, infectious form

Reticulate body-grows with host cell vacuoles, differentiate into elementry bodies

Primary basis of the immunologic testing is the binding of antigens with specific antibodies

The tests must involve some type of visible endpoint.

Visible agglutination or precipitation

Dry, fluroescent reagents and radioactive isotopes are also used

May also be read as a titer using dilutions of serum and observing the rxn at the lowest concentration