Microbiology Case Studies
Terms in this set (73)
-Caused by staphylococcus aureus
-infected hair follicles
Scalded Skin Syndrome
-Upper layer of skin seperates and peels due to exfoliatins
-most common in infants
Most common skin infection
Signs and symptoms: local
infections, characterized by
isolated pustules that become
crusted and rupture
Causative agent: Staphylococcus aureus, Streptococcus pyogenes
Easily treated with penicillin.
Usually heals without scarring, but pigment can be permanently lost (hypopigmentation)
Most common causes of skin infections are Staphylococcus aureus and Streptococcus pyogenes .
Caused by fast-spreading infection in the dermis and in the subcutaneous tissues below
Symptoms = pain, tenderness, swelling, fever, lymphangitis (red streaks leading away from the area
Causative agent: usually Streptococcus pyogenes; MRSA
Symptoms: extreme pain at infection site, then discolored, hot and rash. Fever, confusion, nausea and malaise.
May cause systemic shock so that all systems fail. Fatalities are high
Pathology: Bacteria attack the subcutaneous connective tissue which then becomes necrotic; infection moves swiftly under the skin.
Infected tissue must be removed; if diagnosed early, tissue loss is less severe; in more advanced cases, limb amputation is necessary
Rocky Mountain Spotted Fever
An infectious disease caused by Rickettsia rickettsii.
Transmitted to humans by the bite of ticks.
2 to 4 days incubation
First symptoms: sustained fever, chills, headache, and muscular pain
Distinctive spotted rash (petechiae) within 2 to 4 days after the prodrome. Starts and wrists and ankles.
In most severe untreated cases, enlarged lesions merge and become necrotic
Other manifestations: cardiovascular disruption; conditions of restlessness, delirium, convulsions, tremor, and coma
Causative agent is Clostridium perfringens, an anaerobe and endospore former.
Often a mixed infection
Pain then darkening of the skin, then a "snap, crackle, and pop" sound in crepitant tissue (distorted tissue caused by gas bubbles), high fever, brown, frothy pus and horrible smell from gas produced. Sepsis danger.
Antibiotics administered and dead tissue must be removed
Caused by different strains of human papilloma viruses; > 100 strains of HPV known.
Transmitted by direct contact (skin to skin)
Virus causes cells to multiply
can be removed or immune system will eventually clear most.
Varicella-Zoster Virus- part of the Herpes family (ds DNA, enveloped viruses; latent).
Spread by inhalation of virus
Slight fever, rash (vesicles) on trunk and back that spreads to face, neck and limbs. Rash crusts over and heals.
Weakened immune system, virus travels down nerve ganglia and causes rash/nerve pain.
Caused by Measles virus- ss, enveloped RNA virus
Infection of respiratory tract spreads to blood then to skin
Highly contagious via respiratory droplets
Syncytia formation of infected cells
Dry cough, Fever, Sore throat
Maculopapular (raised, red) rash develops on
head, progresses to trunk and extremities
Spots coalesce and fade to brown
Subacute Sclerosing Panencephalitis
a fungal infection of the
skin in humans and domestic animals.
Fungi feed on keratin, the material found in the outer layer of skin, hair, and nails.
These fungi thrive best on skin that is
warm and moist.
Medically are classified as Tinea and the area they are infecting.
Symptoms are red, itchy, flakey skin.
Organisms are actively multiplying in the blood
Many different bacteria and a few fungi can cause this condition
Fever, patient appears very ill, may have an altered mental state, shaking, chills, and gastrointestinal symptoms. Increased heart rate and breathing.
Can progress rapidly to septic shock=low blood pressure, low body temp, organ failure, increased heart rate, death
Inflammation of the endocardium; usually refers to an infection of the valves of the heart
Fever, anemia, abnormal heartbeat
Sometimes symptoms similar to heart attack
Abdominal or side pain may be reported
Petechiae over the upper half of the body and under the fingernails may be present
In subacute cases, may have enlarged spleen
Caused by Brucella species
CDC possible bioterror agents
Primarily a disease of animals
Bacteria is carried into the bloodstream by phagocytic cells, creating focal lesions in the liver, spleen, bone marrow, and kidney
Fluctuating pattern of fever accompanied by chills, profuse sweating, headache, muscle pain and weakness, and weight loss. Can have chronic symptoms of recurrent fevers, joint pain, and fatigue.
Sometimes called rabbit fever
Natural reservoirs include small mammals such as voles, mice, water rats, squirrels, rabbits and
Tick bites: most frequent arthropod vector
Incubation period of a few days to 3 weeks
Caused by Francisella tularensis.
red spot on the skin, enlarging to an ulcer
enlarged lymph nodes of groin or armpits
shortness of breath
One of the most infectious pathogenic bacteria known
requires inoculation or inhalation of as few as 10 organisms to cause disease.
hardy non-spore forming organism
It is considered to be a potential biological weapon because of its extreme infectivity, ease of dissemination, and substantial capacity to cause illness and death.
F. tularensis is so infective that examining an open culture plate can cause infection.
Humans can contract Tularemia in the following ways:
direct contact with an infected animal or carcass via broken skin
the bite of an infected flea, deer fly, or tick
ingesting infected meat (rare)
Nonfatal. Evolves into a slowly progressive syndrome that mimics neuromuscular and rheumatoid conditions
Early symptom: rash at the site of a tick bite (erythema migrans)
Other early symptoms: fever, headache, stiff neck, and dizziness
Second stage: cardiac and neurological symptoms develop
is caused by Borrelia burgdorferi is a species of Gram negative bacteria of the spirochete class.
It is a zoonotic, vector-borne disease transmitted
Ebola virus infects phagocytes and epithelial cells lining blood vessels.
Uses phagocytes to spread around body to the lymph nodes, liver, lungs, and spleen.
Death to these wbc's results in massive inflammation.
Death to epithelial cells results in vascular instability and coagulation problems.
Incubation period is generally 5-18 days
Rapid onset of fever, malaise, muscle pain, headache, and pharyngitis.
Vomiting and bloody diarrhea
Six days later individuals develop hemorrhagic rash with bleeding at needle sites and bodily orifices.
is a vector-borne infectious
disease caused by protists of the genus Plasmodium.
It is widespread in tropical and
subtropical regions, including parts of
the Americas, Asia, and Africa.
Each year, there are approximately
350-500 million cases of malaria,
killing between one and three million
people, the majority of whom are young
children in Sub-Saharan Africa.
Spread by mosquitos
Protist multiplies in rbc= rbc rupture=fever, swollen spleen and kidney problems
New protists invade new rbc= cyclic
Leads to anemia
caused by the protozoan Toxoplasma gondii.
primary host is the feline.
Animals are infected by eating infected
meat, by ingestion of feces of a cat
that has itself recently been infected, or
by transmission from mother to fetus.
Produces flu-like symptoms
Can progress to encephalitis in immunocompromised
Psychiatric effects? Esp. schizophrenia
Trypanosomiasis (Chagas Disease)
Caused by Trypanosoma cruzi.
Early= mild, local swelling at the site of infection.
Many years later= heart
disease or malformation of the
If untreated, it is often fatal.
Vector: Kissing Bugs
Thin, often segmented
A few medically important examples are:
Schisotosoma mansoni, also called a blood fluke, targets organs that are fed by blood.
Symptoms include fever, diarrhea and fatigue. May progress to include fibrous lesions in many organs.
97% to 100% of the population has some manifestation of it by age 45
Most are due to bacterial colonization and varying degrees of inflammation
Caused by Bacteroides gingivalis & other species
Heliobacter pylori thrives in the acidic environment of the stomach by producing an enzyme that converts urea to ammonia, raising the pH in the cell's vicinity.
G(-) bacillus; flagellated
Gastritis: sharp or burning pain emanating from the abdomen
Gastric ulcers are actual lesions in the mucosa of the stomach
Severe ulcers can be accompanied by bloody stools, vomiting, or both
Long-term infection with H. pylori might be a contributing factor to stomach cancer
Treatment - antibiotics!!!!!
People with type O blood are more susceptible
Cryptosporidiosis is a parasitic disease caused by Cryptosporidium parvum, protozoan
One of the most common waterborne diseases and is found worldwide.
Fecal-oral route, through cyst contaminated
Symptom: self-limiting diarrhea in people with intact immune systems.
In immunocompromised individuals, such as AIDS patients, the symptoms are severe and often fatal
infection of the small intestine
by a protozoan, Giardia lamblia
Drinking groundwater polluted by the
feces of infected animals.
It attaches itself to the walls of the
small intestine and there multiplies
Lots of diarrhea
Greasy, malodorous stool
Entamoeba histolytica is the
causative agent of protozoan (amoebic) dysentery.
Fecal- oral transmission from cysts in contaminated food/water
Can leave GI= hepatitis
Gastroenteritis caused by infection of Salmonella enterica.
nausea and vomiting
can develop into severe dehydration or systemic bloodborne infection
Transmission - poultry, eggs, unpasteurized milk are the main source (estimated that about 1 in 4 chickens are contaminated)
is also transmitted through exposure to reptiles, farm animals, and turtles
Caused by Salmonella enterica serotype Typhi (referred to as S. typhi)
Symptoms same as Salmonellosis plus:
high fever (>104) continues for days or weeks, diarrhea, abdomen pain
Can develop enlarged lymph nodes, liver and spleen and ulcerated intestine
Pathogenesis: deeply invasive (unlike Shigella) and leads to septicemia
Transmission: fecal-oral route
antibiotics (chloramphenicol is drug of choice)
Enterocolitis (dysentery) by infection of Shigella dystenteriae
Bacteria cause lysis of infected colon cells =patchy areas of destruction and inflammation
Shiga toxin = damage to blood vessels in intestinal wall and intense inflammation.
Transmission - fecal -oral route (usually person to person, but can be by flies, food, water, fomites)
Rare in the US, but important in the developing world
enterocolitis (stools are streaked with blood and contain strings of mucous composed of many neutrophils)
can be life threatening due to dehydration!!
bacteria invades cells of large intestine, produces Shiga toxin= causes inflammation, diarrhea= damages cells= bleeding
fluid therapy; antibiotics
Caused by Campylobacter jejuni infection of colon epithelial lining with exotoxin production
Most common bacterial cause of diarrhea in the U.S.
Frequent watery stools
Symptoms may last beyond 2 weeks but usually self-limiting.
Transmission -human infection probably occurs from ingesting contaminated meat or milk; direct person-to-person transmission may occur
Causative Agent: Vibrio cholerae
Gram negative vibrio found in brackish (salty) waters
Abrupt vomiting, rice water stools
Progresses to sunken eyes, cramps, coma, hypotension, death
If left untreated death can occur within 48 hours
Grows in small intestine and produces an exotoxin = the secretion of electrolytes from cells= loss of water due to osmosis.
Excess water, mineral electrolytes and flecks of mucus are excreted taking on the appearance of "rice water stools"
Vaccine available but only produces short term immunity
Treatment: tetracycline and replacement of lost fluids
55% mortality rate in 48 hrs
Issue with poor sanitation
Food Poisoning by Clostridium perfringens
G+ bacillus; endospore former
onset 8-16 hrs; duration 24-48 hours
lives in the g.i. tract of animals, humans
common in feces-rich soil
spores usually contaminate meat, so when food is left unrefrigerated after cooking, spores germinate and new cells produce toxin which is then ingested.
Food poisoning by Bacillus cereus
gastroenteritis is usually mild and brief
There are 2 forms of illness associated with 2 enterotoxins; one form causes vomiting, the other causes diarrhea.
present in soil, water, g.i. tract of humans and animal, so often found in food
when food is left unrefrigerated after cooking, spores germinate and new cells produce enterotoxins which are then ingested.
Vomiting form frequently linked to fried rice, especially when cooked and kept warm for long periods of time
Diarrheal form associated with cooked meats or vegetables that are held at a warm temperature for long periods of time
Food poisoning by Staphylococcus aureus
2-6 hours (rapid onset)
vomiting & diarrhea ("running at both ends")
crampy abdominal pain
exotoxin; toxin can't be destroyed by refrigeration/ cooking
most frequently reported food poisoning in the U.S. - occurs in large outbreaks at picnics or social gathering
usually introduced into food from skin of person preparing it (part of normal skin flora); toxin is produced because food is not kept at proper temps
illness is usually brief and self-limiting, but antibiotics can be used if disease is severe; fluid replacement may be necessary.
Caused by infection of the salivary glands by the Mumps Virus (ss enveloped RNA virus)
Spread by infected droplets
Incubation period is usually 12 - 24 days
Most commonly affects children 2 to 12 years
Syncytia formation of infected cells
Swelling of the parotid glands
Swelling of the temples or jaw
Testicle lump/ pain
Progression to other organs, like brain
Ingestion of Taenia solium
eggs shed in the feces of a tapeworm carrier by pigs and humans.
Humans are infected either by
ingestion of food contaminated
with feces containing eggs, or by
Cysts full of worms can deposit in muscles, the brain, the eyes and in subcutaneous tissues.
Infection caused by ingestion of eggs of Enterobius vermicularis , more commonly known as pin worms.
Lays eggs on the anus which causes a very itchy bum. Scratching deposits eggs under fingernails and eggs are spread or person re-infects.
Very common!! Generally considered a nuisance more than a serious health problem.
Toxic Shock Syndrome
Caused by Staphylococcus aureus
Bacteria enter blood and produce exotoxins (*superantigen)
Symptoms: (sudden onset)
low blood pressure (shock)
red rash on the trunk
Caused by Treponema pallidum, G- spirochette
Three distinct clinical stages:
primary (genital chancres)
secondary (rash can look like chicken pox or heat rash), hair falls out
tertiary (damage to all organs, death) Gummas develop
Latent periods of varying duration also occur
"great imitator"= heart valves, blood vessels, and meninges can be affected
mental illness accompanies neural damage
Treatable with penicillin
From a pregnant woman's circulation into the placenta and fetal tissues.
Inhibits fetal growth
notched incisors ("Hutchinson's teeth")
deformed shin bone
an aged face with a saddle-shaped nose
Caused by Nesseria gonorrhoeae
Hardy G(-) diplococci that possess pili that allow them to attach to epithelial cells and to sperm
can survive in dried masses of pus for 6-7 weeks
Endotoxin damages the reproductive tract mucosa and produce proteases that destroy IgA antibody
The areas most frequently
involved are the cervix, urethra,
rectum, pharynx, and conjunctiva
Possible vaginal discharge
Painful urination if urethra is affected
Major complications occur when the infection ascends from the vagina and cervix to higher reproductive structures
Pelvic inflammatory disease
Caused by Chlamydia trachomatis, obligate intracellular pathogen
Most common reportable infectious disease in the U.S.
Symptoms in males
Symptoms mimicking gonorrhea
Untreated infections may lead to sterility
Symptoms in females
Untreated infections may lead to PID- risk higher than Gonorrhea
Trichomoniasis is caused by a
Trichomonas vaginalis and is
passed almost 100% of the time
through sexual contact.
Trichomoniasis is primarily an
infection of women's vaginal and
urinary tracts= green/white frothy discharge.
Men also may carry the organism
unknowingly, since infection in men
may cause mild or no symptoms
Inflamed mucous membranes of the throat
Incubation time = 92 hours
Once infected, can pass the infection for up to 2 to 3 weeks even if they don't have symptoms.
throat may be red with white patches
Tender, swollen lymph nodes on the sides of your neck
tonsils are red and enlarged
may also have white craters or specks of pus on your tonsils or your tonsils may be covered with a gray or white coating.
general discomfort, uneasiness, or ill feeling
loss of appetite and nausea
Causative agent: Streptococcus pyogenes strains that produce an exotoxin (superantigen).
Pinkinsh-red rash covers the whole body except palms of hands and soles of feet; rash feels like sand paper (may peel after fading)
Tongue has spotted, strawberry appearance.
Causative agent: Streptococcus pyogenes
Develops two to three weeks after infection
Cross-reactivity of antibody to heart, joints, skin, and brain
Occurs often in Children
Gram-positive, Pleomorphic, rods
Used to say that it looked like Chinese characters
Eventual formation of a pseudomembrane that covers throat and nasal passages
Only certain strains of C. diphtheriae
Toxin = thick coating in the nose, throat, or airway
This pseudomembrane is gray or black and can cause breathing problems and difficulty in swallowing.
Treat with antibiotics and anti-toxin
Constant inflammation because capsule makes it hard to phagocytose.
Sputum is often rust-colored from blood coughed up from lungs
Culture of Gram + Diplococci from sputum that is optochin sensitive
Vaccine available, usually for children and elderly patients
Gram negative rod
Destroys lungs= currant jelly sputum (blood)
Associated with alcoholics
Causes milder type of pneumonia (Atypical / walking pneumonia)
No cell wall - no treatment with Penicillin
Causative agent: Mycobacterium tuberculosis
Chronic infection of lower respiratory
Low grade fever
Treatment for TB uses antibiotics to kill the bacteria.
The two antibiotics most commonly used are rifampicin and isoniazid.
Instead of the short course of antibiotics typically used to cure other bacterial infections, TB requires much longer periods of treatment (around 6 to 24 months) to entirely eliminate mycobacteria from the body.
Multi-drug-resistant tuberculosis (MDR-TB): resistance to rifampicin and isoniazid.
Extensively drug-resistant tuberculosis (XDR-TB): also resistant to three or more of the six classes of second-line drugs
60% death if untreated
Active Mycobacterium tuberculosis
Macrophages spread through the bloodstream to other tissues where secondary TB lesions can develop. Such as in kidneys, brain, bone marrow and spinal chord.
Inactive Mycobacterium tuberculosis
Organism growing in the lungs but no symptoms.
Bacteria live inside macrophages= tubercules.
Necrotic tissue healed by calcifiying
When tubercules are ruptured the infection is re-activated
Pertussis (whooping cough)
Caused by Bordetella pertussis bacteria.
Interfere with the respiratory tract's normal ability to eliminate germs.
Destroy the ciliated cells of the trachea and lungs thus inhibiting the flushing mechanism out of the lungs.
Transmission is contaminated droplets.
Incubation is 3 days to 21 days.
Flu-like (Catarrhal stage)
After about 1 to 2 weeks, the dry cough becomes a wet cough that brings up thick, stringy mucus.
At the same time, coughing begins to occur in long spells that may last for over a minute, child turns red from effort or blue from lack of oxygen.
Severe coughing can also cause petechiae in the skin of the upper body, as well as small areas of bleeding in the whites of the eyes. (Paroxysmal stage)
Influenza virus is a ss, enveloped RNA virus
Signs and symptoms
Fever, sore throat, nonproductive cough, myalgia, headache, and malaise
Lasts 3-7 days (or longer)
Complications depend on age of patient
-Possible pneumonia, middle ear infection
-Susceptible to secondary bacterial infections due to damage to cilia in respiratory tract
Droplet (sneezing and coughing)
Short incubation period (1-4 days)
Antigens frequently mutate causing new strains, this is called an antigenic drift.
Flu vaccine is based on the strains that affect the other side of the world during their flu season.
Coccidioides immitis resides
in the soil in certain parts of
the southwestern United States.
It can cause coccidioidomycosis (Valley Fever), a diseases that infects the lungs and skin but can spread to CNS in immunocompromised persons.
also known as Darling's disease, is a
disease caused by the fungus
Symptoms of this infection vary
greatly, but the disease primarily
affects the lungs
is common among AIDS patients because of
their lowered immune system.
In US found associated with feces of the European Starling and in bat guano.
infection caused by the bacterium Neisseria meningitidis.
Gram negative diplococci
Teenagers and adults over 50 having the highest risk of death.
Can kill within 6 hours of first symptoms
normal plus petechiae
Increased spinal fluid pressure
Myocarditis (inflammation of the heart)
Hydrocephalitis (blockage of spinal fluid in brain)
Paralysis of various muscles
Haemophilus influenzae meningitis
children under 5 years of age.
most frequently in 1 month up to 4 years with a peak at 6 to 9 months.
Spreads from respiratory tract to bloodstream to the meninges.
Once the leading cause of meningitis, but Hib vaccine has drastically reduced incidence
Gram negative bacilli
Symptoms - standard meningitis symptoms
Roughly 20% of patients may experience some hearing loss.
Some patients will have brain damage, which can include seizures, mental retardation, learning disorders, abnormalities in speech and language development, and behavioral problems
Streptococcus pneumoniae most common cause of meningitis in adults, and the second most common cause of meningitis in children older than 6 years old.
Symptoms- standard meningitis symptoms
Gram positive diplococci (sometimes chains)
Early treatment of pneumonia and ear infections caused by pneumococcus may decrease the risk of meningitis. There are also two effective vaccines on the market to prevent pneumococcus infection.
The current recommendations are for people at high risk for pneumonia, children, and everyone over the age of 55 to be vaccinated.
With early treatment, the outcome is better. However, 20% of people who contract this disease will die of it and 50% have serious long-term complications
Mostly opportunistic- 2/3 of cases AIDS related
Found in pigeon feces
Standard meningitis symptoms plus:
skin lesions, lung masses or CNS involvement.
Causative agent: Mycobacterium leprae. Related to TB, intracellular pathogen
Development of multiple lesions on skin
Body's cell mediated response destroys the nerve endings.
Loss of sensory perception in areas of skin that have been infected- tends to be areas that are cooler than body temperature
Insensitive areas easily become infected with secondary infections
BCG - vaccine for TB, preventative for leprosy
Endemic in Texas & Louisiana - armadillos are reservoirs (may be spread by touching/eating armadillos)
Can be cured with antibiotics (same as with tuberculosis
Caused Clostridium tetani , G+ rod
Infection begins when the spores are introduced into an injury or wound.
The spores germinate, releasing active bacteria that multiply and produce a neurotoxin, called tetanospasmin.
Tetanospasmin selectively blocks inhibitory nerve transmission (GABA release) from the spinal cord to the muscles, allowing the muscles to go into severe spasm.
spasms and tightening of the jaw muscle (hence the name lockjaw)
neck and other muscles
back muscles, often causing arching (opisthotinosis)
Tetanic seizures (painful, powerful bursts of muscle contraction)
Control and reverse the tetany with antitoxin, vaccine and antibiotics
is caused by Clostridium botulinum; G+ bacillus, endospore-former, strict anaerobe, TOXIN
Food-borne infections, especially honey.
toxin blocks the normal messages between muscles and nerves.
Flaccid paralysis (muscle weakness); muscle paralysis starts with the eye muscles; no fever; usual cause of death is respiratory paralysis; many cases are subclinical
Most (95%) are subclinical infections, which may go unnoticed.
Virus = ss, naked RNA virus
Virus enters via GI tract and multiplies in throat and small intestine (=GI symptoms). Can get into blood and travel to brain=infect and destroy motor neurons.
Non paralytic polio
in neurons, but no damage
symptoms last 1 to 2 weeks
Excessive tiredness, fatigue
pain or stiffness of the back, arms, legs, abdomen; Neck pain
muscle tenderness and spasm in any area of the body
Skin rash or lesion with pain
fever, occurring 5 to 7 days before other symptoms
stiff neck and back
Muscle weakness, asymmetrical
Abnormal sensations of an area
sensitivity to touch, mild touch may be painful
Difficulty beginning to urinate
Bloated feeling of abdomen
Muscle contractions or muscle spasms
irritability or poor temper control
Slow, progressive disease characterized by fatal encephalitis
Incubation time: 1-2 months or more
headache, fever, nausea
partial paralysis near the bite site (persist for 2-10 days, then worsen); paralysis then becomes more general
throat muscles undergo painful spasms
confusion and hallucinations occur
10-14 days after onset, patient goes into a coma and dies
Observation of Negri bodies
in cytoplasm of neurons
2. Positive IFAT
Trypanosomiasis (African Sleeping Sickness)
is a caused by Trypanosoma gambiense and are transmitted to humans by tsetse fly (Glossina Genus) bites which have acquired their infection from human beings or from animals harboring the human pathogenic parasites.
Flu like symptoms and itching
Spreads through circulatory and lymphatics
Crosses blood-brain barrier and get CNS symptoms
Naegleria spp and Acanthamoeba spp. can cause amoebic keratitis and meningoencephalitis.
Meningoencephalitis is caused by
the amoeba entering cuts or
through the nares and
spreading to the central
nervous system. Classic meningitis symptoms.
is extremely contagious!
Due to S. aureus, S. pyogenes, Haemophilus influenzae, Pseudomonas sp., Neisseria gonorrhoeae.
Symptoms: dilated blood vessels, swollen eyelids, a stringy, grey or yellowish discharge.
Is mainly caused by viruses
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