Microbiology Final: Case Studies
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Diagnosis using Symptoms and History: -slight fever -frequent urination -vaginal discharge -lesion on labia -sexually active -high pH of urine -vaginal secretion smear shows gram negative cocci
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Diagnosis: Neisseria gonorrhea
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clinical features most critical to diagnosis of Neisseria gonorrhea
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gram negative cocci, high pH of urine, lesions on labia
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What medication should be prescribed for Neisseria gonorrhea?
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antibiotics penicillin, doxycycline if Chlamydia coinfection
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What further actions after medication should the patient take for Neisseria gonorrhea?
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Abstain from sexual activity until all symptoms are gone, let partners know of the infection and request that they get tested.
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Diagnosis using Symptoms and History: -diabetic man -wound with foul, rotton odor -brownish fluid containing bits of tissue seeping out of wound -got dirty wound from caught leg in manure spreader -swelled leg
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gas gangrene caused by Clostridium perfringens
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How should the gas gangrene would be treated?
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medical removal of the dead tissue, possible amputation, intravenous antibiotics
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Is gas gangrene from infection of Clostridium perfringens a life threatening condition?
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Yes. If the bacteria spreads to the blood stream, it could cause septicemia.
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What is the significance of diabetes in the gangrene study?
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diabetes already causes reduced blood supply to limbs so this would encourage cell death and the resulting gangrene because white blood cells cannot get to the infected area to fight the infection.
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Diagnosis using Symptoms and History: -muscle pain -back spasms -headache -nail puncture wound from old barn -microscope and culture results show gram-positive anaerobic bacilli
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tetanus caused by Clostridium tetani
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What is the scientific name for the organism that causes tetanus?
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Clostridium tetani
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What is the proper treatment for tetanus?
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tetanus antitoxin (antibody) and muscle relaxers
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How could the tetanus been prevented?
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An up to date tetanus booster shot
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Diagnosis using Symptoms and History: -bloody diarrhea -fever -vomiting -not passed urine in 12 hours -blood samples show reduced kidney function andlysed red blood cells -ate ground beef at fast food restaurant 4 days ago
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hemolytic uremic syndrome (hamburger disease)
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What is the organism responsible for the hemolytic uremic syndrome?
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Enterohemorrhagic Escherichia coli O157:H7
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What pathogenic feature causes the severity of the E. coli O157:H7 that causes hemolytic uremic syndrome?
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the shiga-like toxins
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What were the critical features to the diagnosis of hemolytic uremic syndrome caused by E. coli O157:H7
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lysed red blood cells, reduced kidney function, bloody diarrhea, fever, ground beef
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Diagnosis using Symptoms and History: -have worn artificial nails for months -one artificial nail keeps falling off -nail and skin around nail are looking white and chalky
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nail fungus (tinea unguium)
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What would you suggest be done for a more definitive diagnosis for the nail fungus?
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a potassium hydroxide microscopy test or look for hyphae under microscope
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Can you treat the nail fungus yourself or shoudl you see a physician?
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You should see a physician and get prescribed an oral systemic antifungal drug because a topical will only treat the surface and the fungus is deeper under the skin
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What other conditions are caused by dermatophytes?
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scalp ringworm (tinea capitis), athletes foot (tinea pedis), jock itch (tinea cruris)
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What is special about dermatophytes that makes them capable of thriving in their anatomical niche of their hosts?
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They obtain nutrients by breaking down keratin found in nails with the enzyme keratinase, nail beds and feet are also dark, moist and warm
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What is the name for a transmissible agent that contains only protein and has no genetic material?
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prion
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What is the formal name for mad cow disease? Explain the name.
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Bovine (cow) spongiform (makes brain look like a sponge by making holes) encephalopathy (related to brain and spinal cord)
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The human form of mad cow disease is called something other that Bovine spongiform encephalopathy. What is it?
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Variant Creutzfeldt Jakob disease (VCJD)
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Scientists suspect that the humans infected during this outbreak acquired the disease from eating meat from diseased animals. Even when meat is well cooked, it transmits the infection. What does this say about the infectious agent?
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The prion is very difficult to kill and is resistant to heat
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Livestock control measures have been in place in Britain for several years now. can we expect more human cases with links to the British cattle epidemic, or is it behind us? Defend your answer.
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Because the disease has a long incubation period (10 years) and long half life, more cases may appear if not all infected have had symptoms.
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Diagnosis using Symptoms and History: -dizziness -headache -tooth extraction several days earlier -heart murmur -rheumatic fever -petechial hemorrhages under finger nails
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subacute bacterial endocarditis (endocarditis- inflammation of the endocardium)
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What is the most likely causative agent of the subacute bacterial endocarditis and the route of transmission?
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Streptococcus viridans transmitted through the wound to the bloodstream as a result of the tooth extraction.
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What's the connection of subacute bacterial endocarditis with rheumatic fever?
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Rheumatic fever was the cause of the man's heart murmur because the endocardium (lining of heart muscle that covers heart valve) was damaged. A damaged heart valve makes a person more susceptible to bacterial endocarditis because the bacteria easily lodges onto the heart valve.
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Why did you look at the fingernails when diagnosing the subacute bacterial endocarditis?
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Petechial hemorrhages are a result of capillary hemorrhaging caused by bacterimia
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What type of culture would a physician most likely order for detecting bacteria causing suspected subacute bacterial endocarditis and why?
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a blood culture looking for alpha hemolysis because Streptococcus viridans is alpha hemolytic and this would detect the presence of the bacteria in the blood.
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Diagnosis using Symptoms and History: -lung congestion -tired -fever -no response to antibiotic -just moved from Arizona to Ohio -park ranger
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Histoplasmosis
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What components of the history support your tentative diagnosis for histoplasmosis?
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He recently moved from Arizona to Ohio so is related to change in air, possibly Ohio River Valley Fever, no response to antibiotic so either not bacteria or resistant strain, works outdoors so related to outside maybe bat and bird droppings that leave fungal spores in air.
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His condition (histoplasmosis) has not responded to the antibiotic. What are two possible reasons why this is so.
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1) Either it is not a bacterial infection but possibly fungal infection 2) Could be a resistant strain of bacteria
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Should family members worry if histoplasmosis can be contagious?
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No because the infectious organism can only be contracted through the air containing fungal spores.
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What precautions can be taken by other workers who may be regularly or heavily exposed to bat or bird droppings?
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Wear mask and protective clothing.
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-international traveler -intermittant fever in waves every three days
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Malaria
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What should be the first question about the patient's history suspected of malaria?
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Did you travel outside the country before symptoms began?
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What is the most likely causative organism of the malaria?
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If fever waves are every three days- Plasmodium malariae If every 24 hours- Plasmodium vivax
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Is Plasmodium eukaryotic or prokaryotic?
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It is a Protozoan so it is a eukaryote.
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What are the two main places in the human body that are exploited by the causative organism in malaria?
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liver and circulatory system
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-insect bite -use old aloe lotion on bite -bite hot to touch -go to lake after insect bite -sweating and crying, shivering (fever) -pale blue, red patches on legs
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Septicemia
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Explain symptoms in the last paragraph of the case for septicemia.
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high fever shows systemic infection no longer localized, blue skin shows lack of oxygen
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What organism causes septicemia in this case?
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Streptococcus pyogenes or Staphylococcus aureus
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Why "secondary to cellulitis"?
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The septicemia was an infection that occurred after a case of cellulitis. Bug bite caused cellulitis (inflammation of skin). The lake water or aloe allowed dirty bacteria to enter and cause secondary infection.
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How should the septicemia condition be treated at this point?
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Intravenous antibiotics like penicillin
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Why would a fertility specialist recommend a rubella vaccine? Why does he suggest a waiting period after the vaccination before conceiving?
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Without immunity to rubella, a mother's contraction of rubella could cause detrimental effects to the baby called congenital rubella syndrome. Should wait because the MMR vaccine used is a live attenuated virus that could potentially cause the baby to contract CRS if conceived before incubation period ends.
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Why doesn't Kate's disease sound like rubella?
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It lasted much longer than rubella lasts which is only a few days. It probably was regular measles.
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To test immune status, what should the test be for: IgG or IgM? Explain.
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The test should be for IgG because tests detecting IgM are for detecting a new infection. IgG tests immunity.
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If checking for a new rubella case and only has IgG test, how can they determine if it is new w/out IgM test?
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Do two tests where you detect presence of IgG antibodies at one point,then wait and see in next test if the count increases which shows new infection.
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-meningococcal disease What type of organism would you look for in a Gram stain of blood or cerebrospinal fluid in these cases?
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gram negative diplococci
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What is Neisseria meningitidis's portal of entry?
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respiratory tract, nose
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Can you swab the portal of entry to detect presence of the meningococcus?
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Yes but this is normal flora so it doesn't detect if is became pathogenistic in spinal fluid.
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What symptoms are associated with meningitis?
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stiff neck, headache, back pain, fever, confusion
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How should remaining students possibly affected by meningococcal disease be protected?
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Give Rifampin to all and families
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Diagnosis: -girl with severe pain -"break bone" -fever -in blood
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Dengue fever
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What is the most common vector of Dengue fever?
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Aedes aegypti
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What connection does Dengue fever have to broken bones?
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severe muscle and joint pain
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what other infection is transmitted by the same vector (Aedes aegypti mosquito) as Dengue fever?
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yellow fever
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Girl begins hemorrhaging internally. Is this consistant to original diagnosis?
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Yes. The disease has progressed into Dengue hemorrhagic fever, because of capillary permeability, bleeding internally can occur
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Can you be comforted that the Dengue fever is not found in the U.S.?
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No. It actually is not present in the Southest because mosquitos have traveled north because of increasing temperatures.
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Why does the TB test take 36-48 hours to show up?
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It is a delayed hypersensitivity reaction and caused by T cell reaction that takes longer to respond.
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If you have a TB infection, why doesn't the whole body react when injected with the antigen from the test?
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The antigen is only injected subcutaneous/localized and does not enter bloodstream.
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Why would being born in the Netherlands cause you to have a positive TB test reaction?
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You were vaccinated with tthe BCG vaccine for TB as a child b/c this is a country that does these vaccinations while the US doesn't. You already have the antibodies.
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Why is the Tb skin test not recommended for HIV-positive people?
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Because they already have low T cell counts, they may be positive for TB but not show a result because the test shows T cell reactions but with them it may not show up.
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Why should you choose to eat steaks instead of hamburger meat to avoid E coli O157:H7 infection?
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Steak meat is pure slab of meat and would only have bacteria on surface and could be cooked off but hamburger meat could have E coli throughout because it uses lots of parts ground up.
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Does ordering a salad guarantee safety is trying to avoid E coli O157:H7?
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No. The salad may have been grown using fertilizer with infected manure.
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Should your friend stop giving apple juice to baby? Explain.
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If is is pasteurized, no because the bacteria is killed.
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What are the symptoms of E coli O157:H7?
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kidney failure, fever, hemolytic uremic syndrome, bloody diarrhea
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Sould your friend keep eating raw hamburger meat even if his grandfather used to and was fine?
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No. His grandfather was more safe than he is now because E coli O157:H7 is a new strain that is endangering his tradition!
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Is the husband correct that Hepatitis B is mainly transmitted by sexual contact and drug use?
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Yes, but it has been seen to be spread by saliva due to a bite and contact with blood.
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How severe is Hepatitis B for children.
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It may not have severe symptoms but if children get it, they may have it for life (chronic). This could also lead to permanent liver scarring or liver cancer.
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Pam relates Hepatitis B to the recent outbreaks of Hepatitis in restaurants. Is this true?
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No. She is confusing Hepatitis B with Hepatitis A.
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Is the Hep B vaccine safe? How is it made?
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It is a subunit vaccine where only a portion of the DNA is extracted, protein is produced in yeast culture, and injected. There is no way this can cause the disease.
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Most likely causative organism? -People die from tainted meat -symptoms: muscle pain, fever, diarrhea, nausea -high infection rate in pregnant women and dangerous to fetus -source is hotdogs and prepackaged meats
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Listeria monocytogenes
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Why is the infection associated with processed meats but not with hamburger or cuts of meat like chicken?
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These meats are processed in such a way that they provide the desired environment of very salty, high pH, moist. Uncooked when eaten so spread this way.
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Considering that the people at high risk are immune compromised, pregnant, or fetus, does the organism have high or low pathogenicity?
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Low pathogenicity because healthy people are generally unaffected.
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Diagnosis based on: -stomach pain -watery diarrhea with white flecks -constant diarrhea -recently moved from Peru
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Cholera caused by Vibrio cholerae
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How did you come to your conclusion about Cholera?
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The woman is from Peru where Cholera is endemic, white flecks in watery diarrhea
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Why was the doctor initially dubious and why does their recent immigration status convince her that your diagnosis is correct?
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Initially doubtful because Cholera is not endemic to the U.S. but it is endemic to Peru so possible
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What is the first intervention for Cholera when the patient arrives at hospital?
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re-hydration
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The incubation period is 1-4 days. How could the mother have been infected so recently if she's been in country for 6 weeks?
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he could have been asymptomatic carrier until now or someone in family was a carrier and she got it from them or she was an asymptomatic carrier until now.
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Patient is currently receiving a course of ciprofloxacin for Cholera though it won't help her. Why is this done?
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Because she is in the convalescence stage, the drug has no effect on her but because she is still infectious, it is used to make sure she doesn't infect others.
