Test#1 – Microbiology – Flashcards

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

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

An isolated colony or swab from the patient that contains antigen

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

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

Latex aggultination - latex particles that are coated with the antigen 

The patient’s serum – testing for antibodies

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

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

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

VDRL, oucherlony method, immunoelectrophoresis, western blot

Can be testing for the antigen or the antibody

There will be NO hemolysis of the sheep RBCs

As a negative response – no immune complexes were formed

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

Direct=testing for antigen; indirect=testing for antibody

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

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

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

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

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

Specific testing for CD4 and CD8 t-cells

TB skin testing - PPD

Staph, strep and neisseria.

Staph and strep; neisseria 

Catalase – staph is catalase positive

Streptococcus

staphylococcus

They produce pus

Hemolysins – most alpha

Anterior nasal pharynx (nares)

Localized – abscess, folliculitis, furuncle, carbuncle, impetigo

Systemic – osteomyelitis, pneumonia, meningitis, bacteremia

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

Bullous impetigo – S. aureus 

Enterotoxins

Exfoliative toxin

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

S. Saprophyticus 

No – they produce penicillinase 

“spider bite” or small pimple type lesion

Lancefield and the hemolysis reaction on blood agar

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

S. pneumoniae  and the viridans group

Group A (S. pyogenes) – enzymes and toxins

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

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

May cause subacute bacterial endocarditis 

S. pneumoniae; otitis media

Several strains form capsules providing virulence

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

Intracellular gram negative diplococci 

Chlamydia 

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

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

S. Pneumoniae 

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

Bacillus spp and Clostridium spp 

Bacillus anthracis 

Cutaneous anthrax

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

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

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

Emetic form and diarrheal form

C. Perfringens 

Alpha toxin

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

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

Clostridium botulinum – food poisoning, infant botulism, wound botulism

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

No vaccine available

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

Erysipelothrix rhusiopathiae 

Corynebacterium diptheriae 

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

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

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

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

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

previous + reactions, history of BCG vaccine

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

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

                                                               ·      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 

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

It can also be painful or itchy

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

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

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;

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;

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