What stain would you use when looking for organisms like Borrelia, Trypanosomes, Rickettsiae, Chlamydia and Plasmodium?
A patient presents with an infected wound after abdominal surgery. The pus is very stinky. What type of antibiotic would be ineffective in treating this condition?
He likely has an anaerobic infection. Aminoglycosides require O2 to enter the bacteria and would be ineffective against anaerobes because they grow in oxygen poor environments.
What makes a bacteria an obligate anaerobe? List 3 bacteria that fall into this category.
The bacteria cannot use O2 as the final electron acceptor in the ETC. They lack catalase and cannot dispose of H2O2 produced in the presence of oxygen. They lack superoxide dismutase and accumulate reactive oxygen species in the presence of oxygen. Examples include clostridium, bacteroides and actinomyces.
Why is Rickettsiae an obligate intracellular bacteria?
It cannot make its own ATP
Why are asplenic patients at increased risk for meningococcal meningitis?
They cannot opsinize N. meningitides as well and the bacteria persist longer.
A patient presents with oral and facial abscesses that drain through the sinus tracts. Labs show gram positive filamentous anaerobic bacteria with sulfur granules. What is causing his condition? How do you treat him?
Actinomyces israelii. Treat with penicillin.
A sheep farmer presents with a black eschar on his arm with edema surrounding the lesion. Labs are shown below. What bacterial exotoxin is responsible for this lesion? What other presentations can be caused by this bacteria?
Edema factor from B. anthracis (boxcar-shaped gram + rod) is like adenylate cyclase, increases cAMP and causes fluid accumulation. In addition to cutaneous anthrax, inhalation of spores can cause pulmonary anthrax (fever, pulmonary hemorrhage, mediastinitis and shock) and GI anthrax (ulcers, regional, edema, hemorrhage, sepsis, 50% mortality)
A 10 year old boy presents with muscle spasticity and lock jaw a few weeks after stepping on a nail in the yard. What bacterial exotoxin is responsible for his symptoms?
Tetanospasmin from C. tetani prevents release of inhibitory neurotransmitters (GABA and glycine) from Renshaw cells in the spinal cord.
A 7 month old girl presents with flaccid paralysis after eating some honey with her sandwich. What bacterial exotoxin is responsible for her symptoms?
Botulinum toxin prevents release of excitatory neurotransmitters (ACh) from neuromuscular junctions.
A patient presents after being shot in the leg with bubbles forming around the wound. Labs show a double zone hemolytic pattern on blood agar. What bacterial exotoxin is responsible for his condition?
C. perfringes produces an alpha toxin which is a phospholipase (lecithinase) that degrades tissue and cell membranes.
A patient presents with fever, vomiting, desquamation of the skin, rash, hypotension and shock. Symptoms resolve after a tampon was removed that had been left in for a week. Staph aureus is cultured. What toxin was mediating his symptoms?
TSST-1. This locks the CD4 and MHC II receptors together, resulting in overproduction of IFN-gamma and IL2.
A patient presents with a skin rash. Streptococci are cultured after the patient died of septic shock. What toxin caused him to die?
Exotoxin A. This locks the CD4 and MHC II receptors together, resulting in overproduction of IFN-gamma and IL2.
A patient presents with a fever and neck stiffness. Physical exam reveals hypotension, edema and petechiae. CSF shows gram negative diplococci in pairs. How might a toxin be causing his symptoms?
Endotoxin activates macrophages and they secrete IL-1 (fever), TNF-alpha (hypotension, fever) and NO (hypotension). It activates complement and C3a (hypotension, edema) and C5a (PMN chemotaxis) are released. It activates tissue factor, the coagulation cascade and causes DIC.
Gram positive anaerobic spore-forming rods
Clostridium. Bacillus are gram positive AEROBIC spore forming rods
A patient who was admitted to the hospital for cardiac failure develops diarrhea and abdominal cramps. Pseudomembranes are seen on flexible sigmoidoscopy. Lab analysis shows a gram positive spore forming anaerobe. How should you treat him?
He has C. difficile colitis. The bacteria secrete toxin A (binds to brush border of gut) and toxin B (disrupts cytoskeleton via actin depolymerization). Treat with oral vancomycin or metronidazole.
A patient presents with a fever and neck stiffness. Physical exam reveals hypotension, edema and petechiae. At the end of the day he is dead and autopsy shows necrotic adrenal glands. What was likely causing his condition? How could he have been treated and how should you proceed form here?
N. meningitides causes meningococcemia, meningitis and Waterhouse-Friderichsen syndrome (when the adrenals are involved). He could have been treated with ceftriaxone or penicillin G early in the infection. Close contacts should be given prophylactic rifampin, ciprofloxacin or ceftriaxone.
3 types of spirochetes? What is the only type that can be visualized with dye?
Borrelia, Leptospira and Treponema: Only Borrelia can be visualized with Giemsa-Wright staining.
A 40 year old man returns from surfing in Hawaii with yellow skin, altered mental status, photophobia, conjunctival suffusion, anuria, fever and hemorrhage. Labs reveal anemia. What is likely causing his condition?
Water contaminated with animal urine can cause infection by leptospira interrogans. The symptoms this man is presenting with is classic of Weil’s disease.
A 29 year old woman presents with a flu-like illness and symptoms resolved after 10 days. 5 weeks later she returns with migratory polyarthritis, confusion, facial nerve palsy and polyneuropathy. ECG shows a right heart block. She says she enjoys hiking a lot. What is the likely cause of her condition? How do you treat it?
Lyme disease: B. burgdorferi is transmitted to humans by the tick I. scapularis from its natural reservoir in the mouse. Patients do not always notice a tick bite and do not always present with erythema migrans (below). Treat with doxycycline or ceftriaxone.
A patient with syphilis gets really bad flu symptoms after being treated with penicillin. What happened?
Jarisch-Herxheimer reaction: killed bacteria release a lot of pyrogens and induce an inflammatory response.
What other disease is transmitted by the same tick that transmits lyme disease? What would you expect to see on histology?
Anaplasma, on histology you would see berry-like inclusion bodies in granulocytes.
What zoonotic bacterial infection can cause bacillary angiomatosis in an immunocompromised patient?
Bartonella henselae (Cat Scratch Disease)
What zoonotic bacterial infection causes relapsing fever? Vector?
Borrelia recurrentis can continually vary its surface antigens. It is from louse.
What zoonotic bacterial infection causes undulant fever?
Brucella from unpasteurized dairy
What zoonotic bacterial infection can cause bloody diarrhea and is given to you by puppies?
A patient presents with pneumonia and fever. He has exposure to tick feces, aerosolized sheep and cattle amniotic fluid. What is the likely cause of his pneumonia?
Coxiella burnetii = Q fever
Zoonotic bacterial infection transmitted by lone star ticks? What would you expect to see on histology?
Ehrlichia chaffeensis. Since the bacteria infect monocytes you get berry-like inclusion bodies.
Bacterial infection that can cause cellulitis and osteomyelitis? Vector?
Pasteurella multocida from cats and dogs
A patient presents with a central rash that is beginning to spread outward. What bacterial infection causes epidemic typhus? Vector?
Rickettsia prowazeki from louse
A 14 year old boy from North Carolina presents with fever, headache and a rash that started on his hands and feet but has now moved to his legs and arms. What microbe is likely causing his condition and what is the vector?
Rickettsia rickettsii from Dermacentor tick
A patient presents with a central rash that is beginning to spread outward. What bacterial infection causes endemic typhus? Vector?
Rickettsia typhi from fleas.
Bacterial infection that causes plague? Vector?
Yersinia pestis from fleas.
Treatment for all rickettsial and vector borne diseases?
A hiker from Canada presents with bloating, flatulence and fatty foul-smelling diarrhea. Results of stool ova and parasite analysis are shown below. How should you treat him?
He has giardia, likely from ingesting cysts in the water. This is treated with metronidazole. Note the cyst and flagellated trophozoite.
A hiker from Candida presents with blood diarrhea, RUQ pain and colon biopsy shows flask-shaped ulcers in the colonic mucosa. CT shows a liver abscess that likely has an anchovy paste exudate. Stool O&P results are shown below. How should you treat this patient?
He has entamoeba histolytica, likely from drinking cysts in the water. Note the trophozoite with an RBC in the cytoplasm and the cyst with multiple nuclei. Treat with metronidazole.
A 23 year old medical student on a rotation in Africa develops recurring fevers, somnolence and enlarged lymph nodes. Someone brings him to you in a coma. Peripheral blood smear is shown below. What is the vector for his condition?
Note the trypanosome on blood smear. He has African sleeping sickness. This is caused by T. brucei gambiense or T. brucei rhodesiense. It is transmitted by the bite of the tsetse fly.
You see a patient in Ghana with fever, headache, anemia and splenomegaly. Results from his peripheral blood smear are shown below. What are the different ways his fever could present with this condition?
He has malaria, note the schizont and merozoites on blood smear. P. vivax and P. ovale present with tertian fever (every 48 hours, every 1st and 3rd day). These species have the dormant form, hypnozoite, that can cause recurring fevers for years. P. falciparum has severe and irregular fever patterns accompanied by cerebral malaria, renal and lung failure. P. malariae has quartan fever (every 72 hours, every 1st and 4th day).
How do you treat malaria?
Chloroquine: blocks heme polymerization. If resistant, use mefloquine or atovaquone-proguanil. If life threatening test patient for G6PD and use IV quinidine. If P. vivax or P. ovale, test for G6PD and add primaquine.
A 35 year old woman presents with fever and hemolytic anemia. She is from the northeastern US and has a past medical history significant for splenectomy. Peripheral blood smear is shown below. What was the likely vector by which she got this disease? How should you treat her?
Note the “maltese cross” and ring on peripheral blood smear, indicating Babesia. This protozoa is transmitted by I. scapularis, the same agent in Lyme disease. Treat with atovaquone and azithromycin.
A 28 year old woman from Mexico presents with difficulty swallowing food. She also complains of abdominal pain and shortness of breath. Physical exam reveals a bloated abdomen, halitosis and JVD. Peripheral blood smear is shown below. What was the likely vector by which she got this?
She has Chagas disease transmitted by the reduviid bug (kissing bug) which poops in its bite and transmits T. cruzi. Presentations include achalasia, megacolon and dilated cardiomyopathy.
A 45 year old man returned from the Middle East with spiking fevers and hepatosplenomegaly. Labs show pancytopenia. Peripheral blood smear is shown below. What is the vector for this disease?
Note the macrophage full of amastigotes, indicating visceral leishmaniasis (kala-azar). The vector is the sand fly.
Most common intestinal parasitic infection worldwide
A 16 year old girl presents with vomiting, diarrhea and ulcer-like epigastric pain. She claims that she does not wear shoes and walks around in the dirt all day. Why should you make sure you nail down a diagnosis before giving her steroids?
She may have been infected by strongyloides stercoralis, which penetrates the skin through the soil. Giving steroids suppresses the immune system and can cause hyper infection syndrome with this parasite.
What is the only nematode that can complete its lifecycle inside humans?
A 50 year old woman who lives near the Congo river presents with hyper pigmented skin and blindness. Physical exam reveals punctate keratitis. What is the vector for her infection?
The black fly transmits onchocerca volvulus.
A 50 year old woman from Africa presents with skin swelling and a worm in her sclera. What is the vector for this infection?
Loa loa is transmitted by the deer fly, horse fly and mango fly.
A patient presents with elephantiasis. What is the likely vector for this infection?
Wuchereria bancrofti is transmitted by the female mosquito
A 30 year old woman from Mexico who eats a lot of pork presents with chronic headaches and seizures. MRI shows multiple cysts and calcified lesions in her brain. She has additional diarrheal symptoms. What is likely causing her condition?
Cysticercosis is caused by ingestion of taenia solium eggs in pork meat or fecal contaminated food. Intestinal involvement is caused by ingestion of larvae.
A 30 year old dog lover presents with RUQ abdominal pain. CT shows hydatid cysts in the liver. The pathology resident decides to biopsy the cyst and the patient goes into anaphylactic shock. What was the likely infection?
Echinococcus granulosus comes from ingestion of cysts in dog poop.
What are you likely to see on autopsy of a patient who died with chronic schistosomiasis infection?
S. japonicum and S. mansoni cause liver/spleen granulomas, fibrosis and inflammation. Infection with S. haematobium can cause bladder cancer.
What are the reoviruses? What type of viruses are they?
Coltvirus (causes Colorado tick fever) and rotavirus. These are linear, segmented dsRNA viruses.
What are the flaviviruses? What type of viruses are they?
Yellow fever, Dengue, St. Louis Encephalitis, Japanese Encephalitis and Hep C. These are +ssRNA viruses.
What are the togaviruses? What type of viruses are they?
Rubella, EEE, WEE. These are +ssRNA viruses.
What type of virus is SARS?
What are the paramyxoviruses? What type of viruses are they?
Parainfluenza, measles, mumps and RSV. These are -ssRNA viruses.
What type of virus is rabies?
What type of virus is ebola?
What are the arenaviruses? What type of viruses are they? How are they spread?
LCMV and Lassa. Segmented circular ambisense viruses. Transmitted by mice.
What are the bunyaviruses? What type of viruses are they?
California encephalitis, Sandfly/Rift Valley fevers, Crimean-Congo Hemorrhagic Fever and Hantavirus. Segmented -ssRNA viruses.
A 21 year old man comes back from SE Asia with a high fever, jaundice and black vomit. What is the vector that likely transmitted this infection?
The Aedes mosquito transmits yellow fever.
A 3 year old child presents with cough, coryza and conjunctivitis. Physical exam reveals a maculopapular rash that started at his head and moved downwards, pneumonia and bright red spots with a blue-white center in the mouth. What cells are pathogmonic for this condition? What are possible sequelae of this infection?
Paramyxoviruses have fusion proteins that cause fusion of respiratory epithelial cells to form multinucleate cells. Subacute sclerosing panencephalitis (SSPE) is a rare sequelae of measles infection.
A 3 year old child presents with swollen glands on the side of his face, nuchal rigidity and swollen testis. What is causing his condition?
A 71 year old woman was bitten by a raccoon but did not tell anyone. Initially she has a fever and malaise. As her symptoms progressed to agitation, photophobia, hydrophobia and paralysis her daughter took her to the ED where she went into a coma and died. What would you expect to see on EM microscopy and autopsy?
This is rabies. The virus travels to the CNS by migrating retrograde up axons. On EM you would see “bullet-shape” rhabdoviruses. On autopsy you would see Negri bodies in Purkinje cells of the CNS.
Food poisoning from reheated meat dishes
Empiric treatment for a patient presenting with severe neurologic symptoms and nuchal rigidity
Ceftriaxone and vancomycin
A 9 year old boy presents with bone pain a week after being bitten by a cat on his hand. What is likely causing his symptoms?
Pasteurella multocida can cause deep seeded osteomyelitis and is a common pathogen in cat and dog bites.
Preferred treatment of P. falciparum malaria
Artemether-Lumefantrine. IV quinidine or artesunate if malaria is life-threatening.
Criteria for diagnosis of a substance abuse disorder
2 or more of the following: Tolerance, Withdrawal, Persistent desire to quit w/o success, Lots of energy spent obtaining/using/recovering, Reduced activity, Continued use despite knowledge of problems, Craving, Use in despite physical danger, Failure to fulfill obligations, Social conflicts.
What are the stages of change?
1) Precontemplation 2) Contemplation 3) Preparation 4) Action 5) Maintenance 6) Recovery/Relapse
4 categories of depressants
Alcohol, Opiates, Benzodiazepines, Barbiturates
What are the symptoms of alcohol intoxication?
Emotional lability, blackouts, slurred speech, ataxia and coma.
What are the symptoms of alcohol withdrawal?
Mild: anxiety, tremors, seizures, insomnia. Severe: autonomic hyperactivity and delirium tremens (severe CNS changes)
What lab value are useful in determining alcohol use?
GGT (gamma-glutamyl transferase) and AST
An alcoholic presents to the ED with tachycardia, tremors, anxiety, confusion, disorientation, hallucinations and seizures. You find out that he has not had a drink in 72 hours. How do you treat him?
Treat delirium tremens from alcohol withdrawal with benzodiazepines. Symptoms peak 2-5 days after drinking cessation.
What are the signs/symptoms of opioid intoxication? How can you treat it?
Euphoria, respiratory/CNS depression, pinpoint pupils, decreased gag reflex, and seizures. Treat with naloxone or naltrexone.
What are the signs/symptoms of opioid withdrawal? How can you treat it?
Sweating, dilated pupils, piloerection, fever, rhinorrhea, nausea, stomach cramps, diarrhea and yawning. Treat with methadone, buprenorphine and long-term support.
What are the signs/symptoms of barbiturate intoxication? How do you treat it?
Respiratory depression because of low therapeutic window. Treat symptoms (intubate, pressors).
What are the signs/symptoms of barbiturate withdrawal?
Delirium and life-threatening cardiovascular collapse.
What are the signs/symptoms of benzodiazepine withdrawal?
Insomnia, depression, anxiety and seizures.
What are the signs/symptoms of benzodiazepine intoxication?
Ataxia, minor respiratory depression. Treat with flumazenil (benzodiazepine antagonist) and supportive care.
4 types of stimulants
Amphetamines, Cocaine, Caffeine, Nicotine
What are the signs/symptoms of amphetamine overdose?
Euphoria, grandiosity, pupillary dilation, prolonged wakefulness and attention, hypertension, tachycardia, anorexia, paranoia, fever. Severe: cardiac arrest, seizure.
What are the signs/symptoms of amphetamine withdrawal?
Anhedonia, increased appetite, hypersomnolence, existential crisis.
What are the signs/symptoms of cocaine overdose? How do you treat?
Impaired judgment, pupillary dilation, hallucinations (including tactile), paranoid ideations, angina, sudden cardiac death. Treat with benzodiazepines.
What are the signs/symptoms of cocaine withdrawal?
Hypersomnolence, malaise, severe psychological craving, depression/suicidality.
What are the signs/symptoms of caffeine overdose?
Restlessness, increased diuresis, muscle twitching.
What are the signs/symptoms of caffeine withdrawal?
Lack of concentration, headache.
What are the signs/symptoms of nicotine overdose?
What are the signs/symptoms of nicotine withdrawal? How can you relieve symptoms?
Irritability, craving and anxiety. Treat with patches, gum or lozenges that contain nicotine. Treat with partial nACh receptor agonists like varenicline or bupropion.
3 types of hallucinogens
LSD, Marijuana and PCP
What are the signs/symptoms of LSD intoxication?
Perceptual distortion (visual, auditory), depersonalization, anxiety, paranoia, psychosis, possible flashbacks.
What are the signs/symptoms of LSD withdrawal?
There are none
What are the signs/symptoms of PCP intoxication? How do you treat it?
Belligerence, impulsiveness, fever, psychomotor agitation, analgesia, vertical and horizontal nystagmus, tachycardia, homicidality, psychosis, delirium, seizures. Treat with benzodiazepine and rapid-acting antipsychotic.
What are the signs/symptoms of PCP withdrawal?
Depression, anxiety, irritability, restlessness, anergia, disturbances of thought and sleep.
What are the signs/symptoms of marijuana intoxication?
Euphoria, anxiety, paranoid delusions, perception of slowed time, impaired judgment, social withdrawal, increased appetite, dry mouth, conjunctival injection, hallucinations.
What are the signs/symptoms of marijuana withdrawal?
Irritability, depression, insomnia, nausea, anorexia. Most symptoms peak in 48 hours and last for 5–7 days.
What is dronabinol used for?
It is the pill form of marijuana used for nausea in cancer chemotherapy and appetite stimulant in AIDS
How long is marijuana detectible in the urine for?
An 18 year old man presents to the ED with respiratory and CNS depression, pinpoint pupils, decreased gag reflex, and seizures. After giving naloxone his symptoms improve and he is enrolled in a detox center. What medications might this center utilize to help this patient?
Methadone: occupies mu receptors for a long time, withdrawal is longer and more mild than heroin, so they will taper him off gradually. Naloxone + Buprenorphine: Buprenorphine mildly stimulates mu receptors, has fewer withdrawal symptoms than methadone and naloxone is inactivated when taken orally (prevents crushing or injecting abuse of suboxone). Naltrexone: long-acting opioid antagonist used once patient has recovered, prevents patient from getting high if relapse occurs.
A 65 year old man presents to the ED with delirium tremens, hepatitis, pancreatitis and cirrhosis. He is enrolled in a detox clinic. What medications might they use to help him overcome his alcoholism?
Disulfiram: inhibits alcohol dehydrogenase and increased acetaldehyde levels and making the patient feel really bad. Naltrexone: prevents reinforcing DA release with drinking. AA meetings to cope with psychological dependence.
Why might beer supplemented with vitamins be a good idea?
Alcoholics take in empty calories and don’t get enough vitamins. This causes Wernicke (confusion, ophthalmoplegia and ataxia) Korsakoff (irreversible memory loss, personality change and confabulations) syndrome. These syndromes are associated with periventricular hemorrhage and mammillary body necrosis due to thiamine deficiency.
Opioid receptor agonists
mu = morphine. kappa = dynorphin. delta = enkephalin.
How do opioids mediate pain analgesia?
Binding of the mu receptor results in opening of K+ channels and closing of Ca2+ channels. This results in decreased peripheral synaptic transmission by decreasing release of ACh, NE, 5HT and substance P. Centrally they block GABA neurons and potentiate DA release.
How do barbiturates mediate sedation?
They potentiate GABAa action. This increases the DURATION of Cl-channel opening and decreases signal transmission.
How do benzodiazepines mediate sedation?
They potentiate GABAa action by increasing the FREQUENCY at which the Cl channels open. This decreases signal transmission.
What is the 1st sign of shock
What types of shock are included in the category of distributive shock?
Septic, neurogenic and anaphylactic.
Compare and contrast these categories in distributive shock vs. cardiogenic shock: cardiac output, peripheral resistance, venous return, pulmonary capillary wedge pressure, temperature of extremities and use of fluids.
A 22 year old college female presents with fever, photophobia, neck stiffness and a petechial rash. Her blood pressure is very low and she shows signs of adrenal insufficiency. What is your diagnosis?
Waterhouse-Friedrichsen syndrome is associated with N. meningitides meningitis and adrenal insufficiency due to adrenal hemorrhage.
A sexually active 14-year-old boy comes to the physician because of a rash on his trunk and genital area. Physical examination reveals pearly white skin-colored nodules with central umbilication on the genitals and trunk. What is the most likely cause of his condition?
Molluscum contagiosum (a poxvirus) is transmitted by sexual contact, clothes and towels.
Twenty-four hours after placement of a catheter, a hospitalized patient develops a fever and chills. Within 1 hour her systolic blood pressure falls 30 points and she develops swelling in her extremities. Despite valiant efforts by the hospital staff, the patient dies. X-ray of the patient’s lungs taken only hours before she passed away shows pulmonary edema. What mediators of this patient’s disease process is most likely responsible for the pathology described?
This patient suffered from endotoxic shock from gram negative bacteremia. LPS activates the alternative complement cascade. C3a causes hypotension and edema, C5a causes PMN chemotaxis, Hageman factor causes DIC by activating the coagulation cascade, IL-1 causes fever and NO causes hypotension.
Postive Weil-Felix reaction may mean the patient has a proteus infection or what other type of infection due to cross-reactivity of the test?
RMSF - R. rickettsia
Treatment for chagas disease
Treatment for babesia
Treatment for leishmaniasis
Eosinophilic debris from apoptosis in Yellow Fever
What is the mechanism of endotoxic shock?
LPS binds macrophages and macrophages release massive amounts of TNF-alpha from TLR stimulation.
Intracytoplasmic bacilli on Giemsa stain = B. bacilliformis.
Rat bite fever
Gram negative non-branching bacilli in chains Spirillium monoliformis
Only non-motile clostridia
Tick-borne relapsing fever
Louse-borne relapsing fever
B. recurrentis: from antigenic variation in progeny
P. ovale + P. vivax
P. malariae fever time
72 hours, may last for 16-36 hours straight
P. falciparum and P. vivax fever
Variant surface glycoproteins
Visceral larva migrans
Toxocara in dog feces
Dx for strongyloides
Lassa fever treatment
Meningoencephalitis in the US from a mosquito bite
St. Louis encephalitis
Encephalitis in an older person from a mosquito bite, crow host.
Undulant fever from cattle
Small pleomorphic gram negative rods that can cause bacillary angiomatosis
Bacteria that needs CO2 to grow, septicemia in periodontal disease and dog bites
2 parts of Carrion's disease
Oroya fever from hemolytic anemia and Verruga Peruana
4 types of disease from a bacteria that comes from rabbits and requires cysteine to grow.
Oculoglandular, ulceroglandular, pneumonic and typhoidal are all types of tularemia.
Vector and host of rickettsialpox
R. akari lives in mice and is transmitted by mites to people