QStream Flashcards
A 22 year-old woman experiences a crushing leg injury in an automobile accident Within 72 hours of the accident, she develops a bluish red margin near the site of injury that moves toward her trunk. Her attending physician makes a presumptive diagnosis of myconecrosis and performs a biopsy of muscle in the area of the injury. The results of that biopsy reveal muscles cells and Gram positive organisms but no neutrophils. The MOST LIKELY organism seen in the biopsy specimen is:
- Propionibacterium acnes
- Clostridium perfringens
- Actinomyces israelii
- Streptococcus agalactiae
- Staphylococcus aureus
- Propionibacterium acnes
- Clostridium perfringens
- Actinomyces israelii
- Streptococcus agalactiae
- Staphylococcus aureus
The link between myonecrosis and the absence of PMNs is a hallmark of Clostridial infection (particularly C. perfringens). Also, C.perfringens is the leading cause of gas gangrene.
Which of the following tissue samples is most likely to abundantly grow anaerobic bacteria in the laboratory?
- A biopsy of an unusual skin lesion next to the anus in a 70 year old man.
- A biopsy of a stomach ulcer obtained during an upper GI tract endoscopy performed on a 28 year old woman.
- A biopsy of inflamed gingival (gum) tissue from a 47 year old heavy smoker
- A trans-urethral biopsy of an enlarged prostate gland in a 63 year old man.
- A biopsy of an unusual skin lesion next to the anus in a 70 year old man.
- A biopsy of a stomach ulcer obtained during an upper GI tract endoscopy performed on a 28 year old woman.
- A biopsy of inflamed gingival (gum) tissue from a 47 year old heavy smoker
- A trans-urethral biopsy of an enlarged prostate gland in a 63 year old man.
A biopsy of an unusual skin lesion next to the anus in a 70 year old man while the anus is the terminus of the distal GI tract where anaerobes flourish, the external skin would be much less likely to harbor anaerobic bacteria.
A biopsy of inflamed gingival (gum) tissue from a 47 year old heavy smoker, as a biopsy of inflamed gingival (gum) tissue from a 47 year old heavy smoker would likely contain many species of anaerobic bacteria. Oral gingival tissues and their associated spaces have been found to contain several hundred different species of anaerobes, which often play a significant role in dental and other oral infections. (correct answer)
A biopsy of a stomach ulcer obtained during an upper GI tract endoscopy performed on a 28 year old woman. as the stomach generally has among the lowest numbers and diversity of anaerobes within the long course of the GI tract. Once might however find Helicobacter species (aerobic gram negative bacteria), which have a proven association with gastric and duodenal ulcers.
A trans-urethral biopsy of an enlarged prostate gland in a 63 year old man as the male genito-urinary tract is much less likely than the female GU tract to have an anaerobic flora.
A 59-year-old homeless man is found deceased in Rock Creek Park by the side of the road. His body and clothing are blood-soaked and the clothing is torn in multiple places. The police suspect he was a victim of assault. On autopsy external examination, no wounds are identified. On internal examination, the liver is markedly cirrhotic and there is blood in the esophagus and stomach. There are no other significant findings, and his toxicology is negative for ethanol and drugs of abuse. What is best classification of the manner of death?
- Accident
- Natural
- Manslaughter
- Homicide
- Suicide
- Accident
- Natural
- Manslaughter
- Homicide
- Suicide
Natural death resulted from ruptured esophageal varices from cirrhosis is a natural disease, no evidence of any unnatural process, (i.e., external or internal trauma or substance ingestion). Note that Manslaughter is not an accepted manner of death.
You are an intern reporting for duty in the ICU. Your resident tells you that an 85-year-old patient in shock just arrived from the Emergency Department. The patient received no fluid resuscitation, but has an elevated central venous pressure (CVP) reading of 19 cm H2O. Which of the following causes of her shock state is most likely.
- Splenic laceration
- Myocardial infarction
- GI Bleed
- Pneumonia
- Pelvic Fracture
- Splenic laceration
- Myocardial infarction
- GI Bleed
- Pneumonia
- Pelvic Fracture
A patient in cardiogenic shock from an acute myocardial infarction would likely have a normal or elevated CVP. The patient is not volume depleted (as in hypovolemic shock), but has an impaired cardiac output. The fluid “backs up” through the circuit and the CVP would be abnormally high. If the patient were experiencing hemorrhagic shock (a type of hypovolemic shock), you would expect a low CVP. The total body fluid would be low and this would manifest as low central venous pressure which would be the case in a GI bleed, a pelvic fracture or a splenic laceration. A patient with pneumonia would have septic shock and would likely have a low CVP (vasodilation from the inflammatory cascade decreases CVP).
Malaria parasites first enter which cells after they infect a human being?
- Hepatocytes
- Lymphocytes
- Sensory nerve cells
- Intestinal epithelial cells
- Red blood cells
- Hepatocytes
- Lymphocytes
- Sensory nerve cells
- Intestinal epithelial cells
- Red blood cells
Malaria sporozoites injected into the bloodstream from mosquitoes first invade hepatocytes. There, over 1-2 weeks they produce thousands of haploid forms called merozoites. These rupture out of liver cells and invade circulating red blood cells, where they then enter a cycle of repeat red bood cell infections through asexual replication and rupture out of red blood cells. A fraction of merozoites leave the red cell cycle by developing into sexual forms (male and female gametocytes) which remain in circulation and are infectious for mosquitoes. In mosquitoes, the human RBCs break up and release the gametocytes, which develop further and then fuse to become diploid zygotes in the mosquito. These zygotes develop into oocysts which produce haploid sporozoites, which are infectious for humans (completing the cycle). Of note, in P. vivax and P. ovale, a some parasites in hepatocytes can enter a dormant or latent phase called a hypnozoite, allowing for release of merozoites and development of clinical disease at repeated distant time intervals from initial infection.
The following is seen on a peripheral blood smear. Which of the following is the most likely diagnosis?
- Plasmodium ovale
- Plasmodium falciparum
- Plasmodium malariae
- Plasmodium vivax
- Plasmodium knowlesi
- Plasmodium ovale
- Plasmodium falciparum
- Plasmodium malariae
- Plasmodium vivax
- Plasmodium knowlesi
The slide shows banana-shaped gametocytes. These are diagnostic for Plasmodium falciparum.
A 22 year-old male presents to the emergency department with an erythematous and swollen right hand following a cat bite that occurred less than 24 hours ago. He is otherwise healthy without other medical problems. Ultrasound of the dorsum of the hand revealed a fluid collection, and frank purulence was extracted on incision and drainage. Cultures revealed growth of Pasteurella multocida.
All of the following antibiotics would provide appropriate coverage for this organism EXCEPT:
- Clindamycin
- Amoxicillin-clavulanate
- Doxycycline
- Piperacillin-tazobactam
- Clindamycin
- Amoxicillin-clavulanate
- Doxycycline
- Piperacillin-tazobactam
Clindamycin is the correct answer, as P. multocida is inherently resistant to clindamycin. This is important to note, as clindamycin is often provided as an oral option for coverage of infections when MRSA or other staphylococci or streptococci species are possible culprits. However, it has poor gram negative coverage and should not be used for cat or dog bites were Pasteurella multocida (a Gram negative) is a frequent problem .
Doxycycline is incorrect, as doxycycline has excellent activity against P. multocida.
Amoxicillin –clavulanate is the drug of choice for outpatient management of animal bite infections, as it has excellent coverage for P. multocida as well asCapnocytophaga canimorsus.
Piperacillin-tazobactam is an IV β-lactam antibiotic with similar coverage as amoxicillin-clavulanate and therefore covers P. multocida.
Cathy is a military infectious disease physician who has traveled extensively during the last 2 months to launch a multi-center field study of diarrhea therapy. She has visited sites in sub-Saharan Africa, rural Peru, and along the Thailand-Cambodia border. She presents with malaise and shaking chills, with fever to 104°F. When evaluating an initially unexplained in a returning global traveler, the best practice is to:
- Obtain a chest X-ray as soon as possible to rule out tuberculosis.
- Send off a complete blood count and differential exam of white cell morphology to look for eosinophilia which might indicate tropical parasitic diseases.
- Draw blood during the night to look for filaria, and send the sample to an experienced parasitologist.
- First look for serious or potential fatal treatable diseases such as malaria or typhoid fever, if at all possible based on the travel pattern.
- Evaluate at least 3 stool exams for eggs of intestinal parasites, and then consider empiric therapy with albendazole.
- Obtain a chest X-ray as soon as possible to rule out tuberculosis.
- Send off a complete blood count and differential exam of white cell morphology to look for eosinophilia which might indicate tropical parasitic diseases.
- Draw blood during the night to look for filaria, and send the sample to an experienced parasitologist.
- First look for serious or potential fatal treatable diseases such as malaria or typhoid fever, if at all possible based on the travel pattern.
- Evaluate at least 3 stool exams for eggs of intestinal parasites, and then consider empiric therapy with albendazole.
The correct answer is to quickly consider and investigate lifethreatening tropical diseases such as malaria or typhoid fever. Although it is true that such travel may put one at risk of parasitic infections like filaria and intestinal helminths, the consequences of such diseases are chronic and not immediately life-threatening. Similarly, tuberculosis is a risk in a traveler, but the presentation of a high fever and shaking chills is much more indicative of malaria or typhoid.
Which of the following simple history and physical findings is more likely to help you differentiate between the common categories of diseases causing FUO?
- A measured height of fever greater than 104°F is rarely associated with an immunologic disease.
- Regular periodicity of fever is a hallmark of infectious diseases.
- Response to an antipyretic non-steroidal agent eliminates serious causes of FUO.
- Recurring fevers which have occurred for several months or longer are rarely due to malignancy.
- Fever without tachycardia is most common with immunologic disease.
- A measured height of fever greater than 104°F is rarely associated with an immunologic disease.
- Regular periodicity of fever is a hallmark of infectious diseases.
- Response to an antipyretic non-steroidal agent eliminates serious causes of FUO.
- Recurring fevers which have occurred for several months or longer are rarely due to malignancy.
- Fever without tachycardia is most common with immunologic disease.
There are many qualitative characteristics about the patterns of fever associated with unexplained febrile syndromes, including the periodicity, height of fever, duration of each episode, associated symptoms, response to anti-pyretics, etc. However, these descriptive characteristics have not been very specific at predicting the likely category for the cause of a particular presentation of a fever of unknown origin (infectious, immunologic, neoplastic).
Of much greater use for differentiating the more likely major category has been the duration of persistent or recurrent fever over a long period of time. To state this in simple language, infectious causes generally are self-limited (fevers which occur for a few weeks or months at most), while those associated with malignancies usually steadily progress to a stage where the neoplasm has become apparent as an obvious serious illness. Conversely, fevers which persist or reoccur for many months without obvious signs of a fatal illness, are more likely to be due immunologic (rheumatologic) disorders.
A week after an 18-year-old returns from a backpacking trip in Idaho, he develops an abrupt onset of shaking chills, fever of 103ºF, and muscle aches. His fever breaks at three days. A week later he has another episode of fever and chills and seeks medical attention. Splenomegaly is noted on examination. On history, the patient reveals that he acquired multiple bites on the trip. Spiral shaped microorganisms are seen on a blood smear from the febrile patient. The MOST LIKELYcause of the patient’s illness is
- Treponema pallidum
- Yersinia pestis.
- Franciscella tularensis.
- Bartonella quintana.
- Borrelia hermsii.
- Treponema pallidum
- Yersinia pestis.
- Franciscella tularensis.
- Bartonella quintana.
- Borrelia hermsii.
Clues here are backpacking, periodic fever, insect bites, and spiral shaped organism in his blood. The only spiral shaped organisms are given in Borrelia and Treponema pallidum, the agent of syphilis; this presentation is not that of a sexually-transmitted infection. Moreover T.pallidum would not be visible on blood smear (too thin).
During a heavy-weight title boxing competition, a boxer is bitten on the left ear by his opponent. Within 24 hours, his ear becomes swollen, erythematous, and tender to touch. A culture yields a Gram negative bacillus that produces small colonies on blood agar that appear to etch or erode into the surface of the medium and produce a faint smell of bleach. The most likely agent is:
- Staphylococcus species
- Peptostreptococcus species
- Eikenella corrodens
- Pasteurella multocida
- Streptococcus species
- Staphylococcus species
- Peptostreptococcus species
- Eikenella corrodens
- Pasteurella multocida
- Streptococcus species
Eikenella corrodens is commonly found in the human mouth and has been shown to be a causative organism in human bite infections as well as an agent of bacterial endocarditis.
P. multocida is most notably found in infections following animal bites, most commonly dog and cat bites. It is not usually found in human bite infections.
The other organisms are all commonly found in the mouth and have been culprits in human bite infections, but they are Gram positive.
A 19-year-old arrives at his physician’s office with a history of fever and a skin lesion shown below. On history you learn that he has just returned from serving as a counselor at summer camp on the Maryland eastern shore. The vector that transmits the organism responsible for the lesion below is a
- rodent flea (genus Xenopsylla)
- mosquito (genus Aedes)
- deer tick (genus Ixodes)
- dog tick (genus Dermacator)
- body louse (genus Pediculus)
- rodent flea (genus Xenopsylla)
- mosquito (genus Aedes)
- deer tick (genus Ixodes)
- dog tick (genus Dermacator)
- body louse (genus Pediculus)
The skin lesion in the picture is classic erythema migrans. That clinical presentation with fever plus a history of camping on the Eastern Shore of Maryland strongly indicate Lyme disease. The vector for Lyme disease is Ixodes scapularis or the deer tick).
Approximately 3 days after a sheep farmer jabs himself with sheers used to removing wool from a ewe, he notices an erythematous papule that he assumes is an insect bite. However, the papule begins to form vesicles and finally ulcerates day 7. The physician who examines his arm notices the edema around the blackish scab in the center of the lesion. The physician orders a Gram stain and culture of a scraping from the lesion. A single organism is isolated. Which one of the following traits correctly describes the agent that MOST LIKELY infected the farmer ? It
- contains lipid A.
- is an obligate anaerobe.
- contains mycolic acid.
- can only grow intracellularly.
- is heat resistant.
- contains lipid A.
- is an obligate anaerobe.
- contains mycolic acid.
- can only grow intracellularly.
- is heat resistant.
This is a likely case of cutaneous anthrax (farmer, wool, cut, eschar, edema). Spores, which are heat-resistant (best answer) are the infectious form the disease. Other answers are wrong because Bacillus is an extracellular pathogen, Bacillus is Gram positive and has no lipid A, it does not contain mycolic acid that are associated with the cell wall of Mycobacterium tuberculosis, and Bacillus is an aerobe.
Large Gram- positive rods are observed on a blood smear from a 60-year –old patient with a severe flu-like illness accompanied by the chest X-ray as below. The virulence of this organism is associated with its capacity to survive in the blood stream and to the production of two toxins, one of which is a/an
- adenylate cyclase
- hemolysin.
- hyaluronidse.
- super antigen.
- cytotoxin that inhibits protein synthesis.
- adenylate cyclase
- hemolysin.
- hyaluronidse.
- super antigen.
- cytotoxin that inhibits protein synthesis.
This is a likely case of pulmonary anthrax. The main clues here are the widening of the mediastinum on Xray (think inhalational anthrax) supported by the fact that the disease is severe and the organism can survive in the blood stream. The causative agent of anthrax, Bacillus anthracis makes two toxins: lethal toxin and edema toxin (an adenylate cyclase).
The arrow in the figure below points to an inclusion in a human polymorphonuclear leukocyte in a bone marrow aspirate from a 9 year old Maryland boy with fever, headache, and a faint rash and history of a deer tick bite. The organism is MOST LIKELY
- Bartonella henselae.
- Rickettsia rickettsii.
- Anaplasma phagocytophilum.
- Erlichia chaffeensis.
- Borrelia burgdorferi.
- Bartonella henselae.
- Rickettsia rickettsii.
- Anaplasma phagocytophilum.
- Erlichia chaffeensis.
- Borrelia burgdorferi.
Anaplasma phagocytophilum is correct because of the intracytoplasmic inclusion (also called a morulae) in a PMN in the picture combined with the link to a deer tick.Borrelia burgdorferi, the agent of Lyme Disease, has the same vector but would not cause inclusions in PMNs. The vector of B. henselae is a flea, and rash is not part of the presentation of cat scratch fever. In Erlichia, the inclusion would be in a monocyte or macrophage and the vector is the Lone Star tick. Rock Mountain spotted fever, would cause a more fulminate rash, and the vector is the dog tick.
A 10-year old who lives in a wooded rural area of North Carolina presents in the Emergency room with 103.5 ºF fever, a full body macular rash, severe headache, and muscle aches. His mother states that he has recently picked ticks from his dog. The patient’s hematological findings are normal. Furthermore, no abnormalities are noted in the appearance of the boy’s white cells on a peripheral blood smear or in a smear of a bone marrow aspirate obtained after hospitalization of the severely ill child. The cause of this child’s infection is MOST LIKELY
- Rickettsia prowazekii.
- Ehrlichia chaffeensis.
- Rickettsia rickettsii.
- Borrelia burgdorferi.
- Bartonella bacilliformis.
- Rickettsia prowazekii.
- Ehrlichia chaffeensis.
- Rickettsia rickettsii.
- Borrelia burgdorferi.
- Bartonella bacilliformis.
The child’s rash and link to dogs and ticks suggest Rocky Mountain Spotted Fever, particularly in a state where the disease is endemic. Bartonella bacilliformis is wrong because it is the cause of a disease that is only seen in Peru. Borrelia burgdorferi is wrong because of the nature of the rash. Erlichiosis is unlikely because the child’s white cells in the periphery and bone marrow are normal (nothing inside monoctyes). Rickettsia prowazekeii is louse borne and not seen in the USA (epidemic typhus).
An outbreak of an illness that presents with fever, headache and rash occurs among refugees in a displaced persons camp in Somalia. Two of the ill individuals die, and their louse-infested clothes are burned to prevent further spread of the disease. The agent responsible for this potentially epidemic disease prefers to grow
- on mucosal epithelial cells.
- within red blood cells.
- within polymorphonuclear leukocytes (PMNs).
- in small vessel endothelial cells.
- in cerebrospinal fluid.
- on mucosal epithelial cells.
- within red blood cells.
- within polymorphonuclear leukocytes (PMNs).
- in small vessel endothelial cells.
- in cerebrospinal fluid.
The clinical description, the vector, and the site (Somalia, coupled with the epidemic nature of the disease, suggests Epidemic Typhus caused by Rickettsia prowazekii. That organism, like other Rickettsia species, prefers to grow in small vessel endothelial cells.
A 36-year-old returned Peace Corps volunteer from Ghana returns to the US for an extended family visit. While at home, he complains of not feeling well. During the course of one week, he develops symptoms of severe myalgias, abdominal discomfort, vomiting, diarrhea, fever, chills, and sweats. Because his symptoms are not improving, he goes to the local university hospital. On physical exam, enlarged lymph nodes are noted. Blood cultures are drawn, and thin/thick smears are prepared for Giemsa staining. A lymph node aspirate is also performed, and the fluid is sent for Gram staining, culture, and Giemsa staining. All cultures are negative, but the Giemsa stained peripheral blood smear shows the following results. Which organism is most likely to be the cause of this patient’s illness?
- Plasmodium falciparum
- Toxoplasma gondii
- Trypanosoma cruzi
- Trypanosoma brucei gambiense
- Trypanosoma brucei rhodesiense
- Plasmodium falciparum
- Toxoplasma gondii
- Trypanosoma cruzi
- Trypanosoma brucei gambiense
- Trypanosoma brucei rhodesiense
The picture shows an extracellular hemoflagellate protozoan, morphology typical of the genus Trypanosoma. The patient history tells us the patient has lived in West Africa, and the presentation of a sytemically ill patient with large lymph nodes (Winterbottom’s sign) is consistent with T. brucei gambiense. Subspecies rhodesiense causes a more acute and debilitating form of “sleeping sickness” and is endemic to East Africa. The South American T. cruzi is more often asymptomatic until later in life when one may experience cardiomyopathy, megacolon or megaesophagus. Anyone returning from a malaria endemic with fever should be tested for malaria, but this blood film does not show any malarial parasites are present. T. gondii is generally diagnosed in tissue, esp. brain, or by serological means.
This 67 y/o male with known lung cancer presents with hypotension. His heart (subxiphoid and parasternal long views), lung, and inferior vena cava images are shown. For the lung images, the same findings are present on both left and right sides throughout the entire lung fields. What is the most likely cause of his hypotension?
- septic shock
- cardiac tamponade
- tension pneumothorax
- massive pulmonary embolism
- septic shock
- cardiac tamponade
- tension pneumothorax
- massive pulmonary embolism
The ultrasound images show a pericardial effusion and a dilated inferior vena cava; this combined with the patient history are most consistent with cardiac tamponade. There is normal pleural sliding (sand on the seashore sign, eg – no pneumothorax), so this is not tension pneumothorax. With septic shock or hypovolemic shock, the IVC will be small.
