Normal Lab Values

Microbiology Cases

 

Microbiology/Pathology Case Descriptions

Micro Case 1

Clinical history: Over the course of 1 week, a 6-year-old boy develops 0.5- to 1.0-cm pustules on his face. During the next 2 days, some of the pustules break, forming shallow erosions covered by a honey-colored crust. New lesions then form around the crust. The boy's 40-year­old uncle develops similar lesions after visiting for 1 week during the child's illness.

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(Summary of Gross and Lab Findings - click here)
The photograph shows a particularly severe case of impetigo bullosa. It is highly contagious and frequently seen in otherwise healthy children and occasionally in adults who are in poor health. The blood agar plate shows colonied with beta hemolysis typical of Staphylococcus aureus. The organism is catalase and coagulase positive. A positive coagulase test is shown. Most organisms that cause imptetigo are antiobiotic sensitive. The technique for perfoming antiobiotic sensitivity is illustrated. Examples of antiobiotic sensitive and methicillin resistant Staph aureus are shown.
(Summary of Microscopic Findings - click here)
A swab taken from the lesion and gram stained shows gram positive cocci. Gram stain from the culture plate shows gram positive cocci in clusters.

m1-1. What is the MOST LIKELY diagnosis?

ANSWER

 

m1-2. The Gram stain from a skin pustule showed gram positive cocci in clusters. The organism grew on sheep blood agar (SBA) and was catalase positive. What is the most likely microorganism?

A. Staphylococcus aureus
B. Staphylococcus epidermidis
C. Streptococcus pyogenes
D. Streptococcus pneumonia

ANSWER

 

 

 

 

Micro Case 2 (Path Slide 18)
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Clinical History: This 29-year-old male's illness began 10 weeks prior to death, with an episode of "flu". Two weeks later his urine became "smoky". He was found to have hematuria, albuminuria and elevated BUN (180 mg/dl). He died from a pulmonary embolus.

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(Summary of Gross and Lab Findings - click here)
A photograph of the pharynx at at initial presentation shows enlarged erythematous tonsils which are covered with purulent material. A throat culture was obtained by swabbing the pharynx. The material was then swabbed onto a blood agar plate and incubated at 37 degrees overnight. Beta hemolysis typical of Streptococcus pyogenes is shown. A gram stained smear of the culture shows gram positive cocci in chains. The kidneys were enlarged (230 gm each). The surface was granular and covered with pinpoint hemorrhages in the fresh state. The external surface with capsule removed is illustrated.
(Summary of Microscopic Findings - click here)
A swab taken from the lesion and gram stained shows gram positive cocci. Gram stain from the culture plate shows gram positive cocci in clusters.
(Review Normal Histology - click here)
Norm No. 2 Kidney
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The kidney excretes soluble waste from the body and controls electrolyte balance. It consists of the cortex and the medulla. Within the outer cortex, glomeruli with delicate capillary loops are seen.  The basement membrane is thin and without inflammation or thickening. Bowman’s capsule that surrounds the glomerulus is thin. The interstitium demonstrates no evidence of inflammation or fibrosis.  In the areas between the glomeruli, tubules and arterioles are seen. The tubules are intact.  The vessels exhibit no narrowing or wall thickening. The inner medulla of the kidney contains only tubules and blood vessels. Larger arteries and veins are located at the interface between cortex and medulla.

 

m2-1. What is the BEST diagnosis at the time of death?

ANSWER

 

m2-2. The throat culture obtained exhibited gram positive cocci in chains. It also showed beta-hemolysis on sheep blood agar (SBA) and was catalase negative. What was the most likely organism?

  1. Streptococcus pyogenes
  2. Streptococcus viridans
  3. Staphylococcus aureus
  4. Streptococcus pneumonia

    ANSWER

 

m2-3. An elderly wheelchair bound man had a history of recurrent urinary tract infections. He presents with new onset of fever, chills, and confusion. Blood cultures were drawn. The organism grown was non-hemolytic, catalase negative, and PYR positive. Gram stain showed gram positive cocci. What is the most likely organism?

  1. Streptococcus viridans
  2. Staphylococcus epidermidis
  3. Staphylococcus saprophyticus
  4. Enterococcus species

ANSWER

 

m2-4. An elderly wheelchair bound man had a history of recurrent urinary tract infections. He presents with new onset of fever, chills, and confusion. Blood cultures were drawn. The organism grown was non-hemolytic, catalase negative, and PYR positive. Gram stain showed gram positive cocci. What is the MOST LIKELY organism?

  1. Streptococcus viridans
  2. Staphylococcus epidermidis
  3. Staphylococcus saprophyticus
  4. Enterococcus species

ANSWER

 

 

Micro Case 3 (Path Slide 51)
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Clinical History: A 45-year-old male became ill approximately 2 to 3 weeks ago following an alcoholic spree. He had nausea, vomiting, dehydration, confusion and high fever. He died suddenly shortly after admission.

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(Summary of Gross and Lab Findings - click here)
Gram stain of sputum obtained before death shows Gram positive cocci in pairs. The right lung was heavy weighing 700 grams. Its lower lobe showed diffuse gray consolidation. The trachea and bronchi contained a great deal of mucus, and the mucosa was dark red.
(Summary of Microscopic Findings - click here)
The alveoli are distended and contain a large amount of inflammatory exudate, which consists of many polymorphonuclear leukocytes, a few RBC's, macrophages and strands of fibrin. Many RBC's have been phagocytosed by the macrophages and are undergoing disintegration. The alveolar septa are delicate and well preserved, but markedly congested.

 

What is the MOST LIKELY diagnosis AND the likely causative agent?

ANSWER

 

m3-1. These images depict pneumonia in the stage of:

  1. Congestion
  2. Red hepatization
  3. Gray hepatization
  4. Resolution
  5. Abscess formation

ANSWER

 

m3-2. Community acquired atypical pneumonia can be caused by which of the following organisms?

  1. Legionella pneumophilia
  2. Staphylococcus aureus
  3. Klebsiella pneumoniae
  4. Mycoplasma pneumoniae
  5. Pseudomonas aeruginosa

ANSWER

 

 

 

Micro Case 4 (Path Slide 195)
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Clinical History: A 67-year-old male had rheumatic heart disease for thirty years. Three months prior to death he began to have episodes of fever and chills accompanied by signs of worsening congestive heart failure. Splinter hemorrhages and purpuric skin rashes were noted three weeks before death.

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(Summary of Gross and Lab Findings - click here)
Blood cultures grew alpha-hemolytic streptococci. Gram stain shows gram positive cocci in chains. The heart weighed 400 grams. There was thickening of the mitral valve leaflets and the chordae tendineae. Many friable calcified pink-gray granular verrucae were present on the valve. In addition, a large vegetation of the same type was found on the left auricular endocardium.
(Summary of Microscopic Findings - click here)
The section represents a portion of mitral valve, left atrium and left ventricle. The valve is greatly thickened and damaged. It is infiltrated with acute and chronic inflammatory cells, and shows a zone of necrosis and fibrosis in the central portion of the valve. The myocardium shows slight focal fibrosis, and focal acute inflammatory infiltration in some sections.

 

m4-1. What is the MOST LIKELY diagnosis?

ANSWER

 

m4-2. Most cases that present with these findings are caused by:

  1. Chlamydiae
  2. Rickettsiae
  3. Fungi
  4. Bacteria

ANSWER

 

m4-3. In this particular patient the MOST LIKELY causative organism was:

  1. Group A Streptococci
  2. Viridans Streptococci
  3. Staphylococcus aureus
  4. Staphylococcus epidermidis

ANSWER

 

m4-4. The organism MOST LIKELY to infect normal heart valves is:

  1. Group A Streptococci
  2. Group B Streptococci
  3. Viridans Streptococci
  4. Staphylococcus aureus

ANSWER

 

m4-5. The organism MOST OFTEN associated with infective endocarditis in IV drug abusers is:

  1. Group B Streptococci
  2. Viridans Streptococci
  3. Staphylococcus aureus
  4. Staphylococcus epidermidis

ANSWER

 

m4-6. The heart valve MOST OFTEN affected by infective endocarditis in IV drug abusers is the:

  1. Aortic valve
  2. Mitral valve
  3. Pulmonic valve
  4. Tricuspid valve

ANSWER

 

m4-7. Which of these organisms are normal flora of the throat and are associated with dental caries, brain abscesses, and endocarditis?

  1. Staphylococcus epidermidis
  2. Streptococcus viridans
  3. Streptococcus pneumoniae
  4. Peptostreptococcus species

ANSWER

 

m4-8. A patient with suspected infectious endocarditis has a St. Jude’s prosthetic aortic valve and a fever of 38.6°C (101.5°F). Blood culture shows non-hemolytic, small, white colonies. The organism was Gram positive, catalase positive and coagulase negative. What is the MOST LIKELY organism?

  1. Streptococcus viridans
  2. Streptococcus pyogenes
  3. Stapylococcus epidermidis
  4. Staphylococcus aureus

ANSWER

 

m4-9. A throat culture grows normal oropharyngeal flora. What alpha-hemolytic organism is most likely to be isolated on the blood agar?

A. Staphylococcus epidermidis
B. Staphylococcus viridans
C. Streptococcus pneumoniae
D. Peptostreptococcus species

ANSWER

 

m4-10. A throat culture grows normal oropharyngeal flora. The coagulase test for the organism is positive. What is the genus and species of the organism?

A. Staphylococcus aureus
B. Streptococcus agalactiae
C. Streptococcus pyogenes
D. Staphylococcus epidermidis

ANSWER

 

 

Micro Case 5

Clinical history: A 33-year-old female dairy farmer develops a severe headache and neck stiffness. On physical examination, her temperature is 38.2°C.  She has no papilledema.  A lumbar puncture is performed, and a Gram stain of the CSF obtained shows many short, gram-positive rods.

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(Summary of Lab Findings - click here)
Gram stain of the CSF obtained shows many short, gram-positive rods.

m5-1. Based on the clinical findings presented, what is the most likely causative agent in the case above?

ANSWER

 

m5-2. A sputum gram stain of an elderly person with cough and fever shows gram positive cocci in pairs. What is the most likely organism?

  1. Haemophilus influenzae
  2. Streptococcus pyogenes
  3. Enterobacter species
  4. Streptococcus pneumoniae

    ANSWER

 

m5-3. A 10-month-old child of a family from Mexico living in Durham was noted by his mother to have a grand mal seizure with shaking of arms and legs by the description given to the EMT. The EMTs found the child limp and unresponsive. In the emergency room the child’s fever was 39.5°C (103.1°F). Blood cultures and lumbar puncture were performed. CSF findings were as follows:

  • cell count of 4000
  • 95% PMNs
  • glucose 20mg/dl
  • protein 125mg/dl.

Gram stain showed PMNs and occasional Gram-negative coccobacillary organisms. The organism grew on chocolate agar but not on sheep blood agar or MacConkey’s agar. What is the most likely organism in this case?

  1. Haemophilus influenzae
  2. Neisseria meningiditis
  3. Moraxella catarrhalis
  4. Streptococcus pneumonia

ANSWER

 

 

 

Micro Case 6 (Path Slide 123)
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Clinical History: A 25 year-old woman had pelvic pain, fever, and vaginal discharge for 3 weeks. On physical examination, she has lower abdominal adnexal tenderness and a painful, swollen left knee.  Laboratory studies show WBC count of 11,875/mm3 with 68% segmented neutrophils, 8% bands, 18% lymphocytes, and 6% monocytes.

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(Summary of Gross and Lab Findings - click here)
The uterine tubes were markedly distended and thickened with adhesions between the fimbriated end and the ovaries. On sectioning, pus exuded from the lumen. Cultures grown in chocolate agar and Thayer-Martin agar (TMA contains antibiotics that permit the growth of certain species) yielded colonies. The organisms were small gram negative cocci in pairs.
(Summary of Microscopic Findings - click here)
The villi of the uterine tube are plump and edematous, with marked dilation and congestion of capillaries. The mucosa is heavily infiltrated by polymorphonuclear leukocytes, which have broken through foci of necrotic mucosa, producing the purulent exudate. Besides this acute phase, there are chronic features evidenced by plasma cell, lymphocytic and macrophage infiltration and fibroblastic proliferation. The muscular layers are edematous and infiltrated by acute and chronic inflammatory cells. This probably represents gonorrheal infection, the mucosa being predominantly involved, in contrast to other pyogenic infections which more frequently involve the outer layers and relatively spare the mucosa.
(Review Normal Histology - click here)
Norm No. 20 Uterine (fallopian) tube (aka oviduct)
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The fallopian tube is lined by ciliated columnar epithelium that aid in transport of the ovum to the uterus. The epithelium is arranged in fronds that project into the lumen. The wall consists of smooth muscle and connective tissue.

 

 

m6-1. What is the MOST LIKELY diagnosis AND the likely causative agent?

ANSWER

 

m6-2. What is a likely complication of this disease?

  1. Ectopic pregnancy
  2. Infertility
  3. Tubo-ovarian abscess
  4. ALL of the above

ANSWER

 

m6-3. What organisms are most likely to cause this disease?

  1. Bacteria
  2. Viruses
  3. Fungi
  4. Parasites

ANSWER

 

m6-4. Which of the following statement about this disease is FALSE?

  1. It is usually associated with endometriosis
  2. May be complicated by strictures and infertility
  3. May also involve the adjacent ovary
  4. May result in a hydrosalpinx
  5. May be complicated by septicemia
  6. ALL of the above statements are false regarding this disease.
  7. NONE of the above statements are false regarding this disease.

ANSWER

 

m6-5. The following organisms are commonly responsible for pelvic inflammatory disease EXCEPT:

  1. Gonococci
  2. Chlamydia
  3. Aspergillus
  4. Streptococcus
  5. Staphylococcus

ANSWER

 

m6-6. A 25-year-old male presents with urethritis. The Gram stain shows intracellular gram positive cocci. What is the most likely organism?

  1. Chlamydia trachomatis
  2. Ureaplasma species
  3. Neisseria gonorrhoeae
  4. Haemophilus ducreyi

ANSWER

 

 

Micro Case 7 (Path Slide 9)
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Clinical History: A 51-year-old male had a "neurogenic bladder", caused by a spinal cord tumor. He had multiple bladder infections which were treated with antibiotics. He had surgery to remove the tumor. Postoperatively, he developed fever and costovertebral angle tenderness which did not respond to antibiotics. He expired and an autopsy was performed.

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(Summary of Gross and Lab Findings - click here)
A catheterized urine specimen was obtained before death and submitted for culture studies. The organism grew on sheep blood agar (SBA) and on MacConkey agar with over 100,000 colony forming units/ml of urine. Gram stain of a blood culture showed gram negative rods. The bladder was distended, with a thickened, trabeculated wall. There was a bilateral hydroureter and hydronephrosis. The left kidney was swollen, and the cut surface showed soft foci of yellow streaks extending toward the pelvis.
(Summary of Microscopic Findings - click here)
Naked eye examination of the slide reveals dark streaks extending from the outer cortex to the inner medulla. Microscopically these are foci of acute inflammation, including necrosis and hemorrhage, with masses of polymorphonuclear leukocytes that are also found in many tubules.
(Review Normal Histology - click here)
Norm No. 2 Kidney
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The kidney excretes soluble waste from the body and controls electrolyte balance. It consists of the cortex and the medulla. Within the outer cortex, glomeruli with delicate capillary loops are seen.  The basement membrane is thin and without inflammation or thickening. Bowman’s capsule that surrounds the glomerulus is thin. The interstitium demonstrates no evidence of inflammation or fibrosis.  In the areas between the glomeruli, tubules and arterioles are seen. The tubules are intact.  The vessels exhibit no narrowing or wall thickening. The inner medulla of the kidney contains only tubules and blood vessels. Larger arteries and veins are located at the interface between cortex and medulla.

 

m7-1. What is the BEST diagnosis?

  1. Acute pyelonephritis
  2. Acute glomerulonephritis
  3. Chronic pyelonephritis
  4. Chronic glomerulonephritis

ANSWER

 

m7-2. ALL of the following are risk factors for this condition EXCEPT:

  1. Reflux nephropathy
  2. Congenital vesicoureteral reflux
  3. Posterior urethral valves
  4. Acetaminophen (Paracetamol) overdose
  5. Urolithiasis

ANSWER

 

m7-3. A urine culture from an 18-year-old woman with similar symptoms also grew a pure culture of more than 100,000 colonies/ml of an organism on sheep blood agar (SBA) and MacConkey’s agar. The gram stain also showed gram negative rods. What is the most likely organism?

  1. Escherichia coli
  2. Enterococcus species
  3. Staphylococcus epidermidis
  4. Staphylococcus saprophyticus

ANSWER

 

 

Micro Case 8 (Pathology Slide 39)
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Clinical History: 58-year-old African American female had been hemiplegic on the right side for 3 months prior to death. She developed malaise, fever and chills after visiting with her grandchildren. Her infection progressed. She developed dyspnea and expired.

Image Gallery

(Summary of Gross and Lab Findings - click here)
A sputum gram stain showed small gram negative rods. This fastidious organism requires chocolate agar for growth. A gram stain of the cultured organism is also shown. There was a thrombosis of the left internal carotid artery with infarction of the left cerebral hemisphere. There was a massive embolus of the right pulmonary artery. Both lungs were firm with mucopurulent exudate in the bronchi. The left lower lobe was firm and gray-yellow with a shaggy fibrinous exudate over the pleura.
(Summary of Microscopic Findings - click here)
Bronchi and alveoli are filled with neutrophils. There are scattered masses of fibrin.

 

m8-1. Based on these clinical findings, what is the best diagnosis and likely causative agent?

ANSWER

 

m8-2. What is the most likely cause of this disease in most adults?

  1. Pseudomonas aeruginosa
  2. Mycoplasma pneumoniae
  3. Streptococcus pneumoniae
  4. Legionella pneumophilia
  5. Haemophilus influenzae

ANSWER

 

M8-2. What organism would be most likely to cause a persistent infection in cystic fibrosis?

  1. Pseudomonas aeruginosa
  2. Mycoplasma pneumoniae
  3. Streptococcus pneumoniae
  4. Legionella pneumophilia

ANSWER

 

Micro Case 9

Clinical history: A 52-year-old homeless, alcoholic man had a fever and a cough productive of thick sputum that worsened over several days. His temperature is 38.2°C.   Diffuse crackles are heard at the right lung base. Laboratory studies are as follows:

  • hemoglobin: 13.3 g/dL
  • hematocrit: 40%
  • platelet count: 291,8000/mm3
  • WBC count: 13,240/mm3 with 71 segmented neutrophils, 7% bands, 16% lymphocytes, and 6% monocytes.

Image Gallery

(Summary of Gross & Lab Findings - click here)
The sputum was thick and gelatinous. A gram stained smear shows gram negative rods.

 

m9-1. Based on these clinical findings, what is the likely causative agent?

ANSWER

 

m9-2. An 18-year-old Duke freshman presented to student health with severe headache, fever, and disorientation. A lumbar tap was performed with the following results:

  • cell count: 300 with 100% PMN
  • glucose: 10 mg/dl
  • protein: 100 mg/dl.

The gram stain of the spinal fluid revealed numerous PMNs with intracellular gram-negative diplococci. What is the most likely organism?

  1. Streptococcus pneumoniae
  2. Moraxella catarrhalis
  3. Haemophilus influenza
  4. Neisseria meningitides

ANSWER

 

 

Micro Case 10

Clinical history: A 66-year-old man incurs extensive thermal burns to his skin and undergoes skin grafting procedures in the surgical intensive care unit.  Two weeks later, he has increasing respiratory distress.  Laboratory studies show hemoglobin of 13.1 g/dL, hematocrit 39.2%, platelet count 222,200/mm3, and WBC count 4520/mm3 with 15% monocytes. A chest radiograph shows extensive bilateral infiltrates with patchy areas of consolidation.

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(Summary of Gross and Lab Findings - click here)
A photograph of burn patient is shown. There is a thick purulent exudate on the skin surface. Cultures of the wound on MacConkey and sheep blood agar (SBA) showed aerobic, lactose-negative, Gram-negative bacterium.

 

m10-1. Based on these clinical findings, what is the likely causative agent?

ANSWER

 

m10-2. A sputum specimen from a cystic fibrosis patient grew Gram negative rods on sheep blood agar and MacConkey’s agar. The organism was oxidase positive. What is the most likely organism?

  1. Streptococcus pneumoniae
  2. Klebsiella pneumoniae
  3. Pseudomonas aeruginosa
  4. Enterococcus species

    ANSWER

 

 

 

Micro Case 11

Clinical history: A suspicious envelope arrived for sorting at rural post office. The envelope was opened and found to contain white powder. Approximately two days later, the postal worker who handled the letter developed cutaneous boils, which were and 1 to 5 cm in diameter with central necrosis and eschars. He and his wife also developed a mild nonproductive cough with fatigue, myalgia for 72 hours, followed by severe dyspnea, diaphoresis and cyanosis.  Temperature of 39.5°C, pulse 105/min, respiration 25/min, and blood pressure 85/45mm Hg.  Crackles were heard at the lung bases. A chest xray shows a widened mediastinum and small pleural effusions. WBC count of 13,130/mm3, hemoglobin 13.7g/dL, hematocrit 41.2%, MCV 91 um3, and platelet count 244,000/mm3. Both died despite antibiotic therapy. Several cattle, horses, and sheep on the postal worker's farm also died.

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(Summary of Gross and Lab Findings - click here)
An example of the skin lesions is shown. These are painless puritic papules that have developed into pustules. Edema surronds the pustule and an eschar has developed. A gram stained smear of material from the pustule is shown. The organisms are spore-forming, Gram-positive rods.

m11-2. In a somewhat related case, when Pharaoh did not heed Moses to the let the captive Hebrews go, a series of plagues fell upon the land of Egypt. In the fifth plague, large domesticated mammals including cattle, horses, and sheep died. This was followed by a plague in which the Egyptians developed cutaneous boils. Some developed a mild nonproductive cough associated with fatigue, myalgia, and low grade fever over 72 hours, followed by a rapid onset of severe dyspnea with diaphoresis and cyanosis. Despite antibiotic therapy with both ciprofloxacin and doxycycline (had they been available), many of those affected would die. Which of the following organisms is most likely to have produced these findings?

  1. Bacillus anthracis
  2. Herpes simplex virus
  3. Mycobacterium leprae
  4. Staphylococcus aureus
  5. Yersinia pestis

ANSWER

 

 

Micro Case 12 (UMich Slide 017)
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Clinical history: A 45-year-old woman is being treated in the hospital for pneumonia complicated by septicemia. She has required multiple antibiotics and was intubated and mechanically ventilated earlier in the course. On day 20 of hospitalization, she has abdominal distention. Bowel sounds are absent, and abdominal radiograph shows dilated loops of small bowel suggestive of ileus. She has a low volume of bloody stool.

Image Gallery

(Summary of Gross and Lab Findings - click here)
A pseudomembrane composed of an adherent layer of inflammatory cells and debris covers the injured bowel mucosa.
(Summary of Microscopic Findings - click here)
Damaged crypts are distended by a mucopurulent exudate.

 

m12-1. Based on these clinical findings, what is the likely causative agent?

ANSWER

 

m12-2. Which of the following are appropriate specimen samples for anaerobe culturing:

  1. blood, spinal fluid, abscess aspirate
  2. deep tissue biopsy, sputum, blood
  3. cerebrospinal fluid, tissue and debridement from decubitus ulcer, bile
  4. tissue swabs, blood, urine

    ANSWER

 

 

 

Micro Case 13

Clinical history: A 25-year-old man is involved in an accident in which he is ejected from the vehicle. He sustains a compound fracture of the left humerus and undergoes open reduction with internal fixation of the humeral fracture.  Several days later, he has marked swelling of the left arm and crepitus

Image Gallery

(Summary of Gross and Lab Findings - click here)
On the arms, there is marked swelling and tissue destruction with black discoloration. Boxcar shaped gram positive rods are seen in the gangrenous tissue. The organism requires anaerobic culture conditions and egg yolk agar for growth.

m13-1. In a similar case, a middle aged woman with type 2 diabetes presents to the emergency room with a very painful right lower leg. She has a wound on that extremity and stated that she stumbled on a fallen tree limb in her yard. You observe that her lower leg is discolored and swollen with several areas of crepitus. The abscess fluid was sent to the microbiology laboratory for aerobic and anaerobic culture. The organism grew best on anaerobic cultures and was lecithinase positive. Gram stain shows gram positive rods and the organism show anaerobic growth on egg yolk agar. What is the most likely organism?

  1. Fusobacterium nucleatum
  2. Bacteroides fragilis
  3. Clostridium perfringens
  4. Peptostreptococcus spp.

ANSWER

 

 

 

Micro Case 14 (Path Slide 451)
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Clinical History: A 4-year-old female had a gradual onset of fever, productive cough, anorexia and diarrhea about eleven days prior to death. The breath sounds were harsh, and a few cracking rales were heard over the right base posteriorly.

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(Summary of Gross and Lab Findings - click here)
Sputum smear showed acid fast bacilli. Sputum cultures results became available four weeks after death, showing the presence of slow-growing colonies. The lungs showed fibrinous exudates over the pleural surfaces. The cut surface of the lung revealed innumerable small, gray-white nodules 1-4 mm in size. A large caseous tubercle of 0.5 cm was present in the left lower lobe, eroding into a large pulmonary vessel.
(Summary of Microscopic Findings - click here)
A lower power examination reveals numerous poorly defined tubercles approximately of the same size and same stage of development. These tubercles show a slight caseous necrosis and consist predominantly of mononuclear cells, epithelioid cells, and a few giant cells. In alveoli there is a moderate amount of mononuclear cell infiltration. Some lymphocyte and plasma cell infiltration is diffusely present in the alveolar septa..

 

m14-1. Based on these clinical findings, what is the likely causative agent?

ANSWER

 

m14-1. Which of the following is the BEST diagnosis?

  1. Ghon complex
  2. Miliary (disseminated) tuberculosis
  3. Foreign body reaction to talcum powder
  4. Atypical pneumonia
  5. H1N1 influenza

ANSWER

 

 

 

Micro Case 15

Clinical history: A 35-year-old man with HIV complains that he has had a "bad" taste in his mouth and discoloration of his tongue for the past 6 weeks.

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(Summary of Gross and Lab Findings - click here)
There are areas of adherent, yellow-tan, circumscribed plaque on the oropharynx and the tongue. This plaque can be scraped off as a pseudomembrane to show an under­lying granular, erythematous base. The material is composed of organisms and inflammatory debris. Gram stained smear shows yeast with pseudohyphae. Culture shows pearly colonies typical of yeast. Germ tube test is positive. Invasive infections may occur in immunocomprised individuals. Pseudohyphae may be seen in tissue section with PAS stain.

 

m15-1. What is the MOST LIKELY diagnosis?

ANSWER

 

m15-2. In a separate case, a blood culture from a neutropenic (<100 neutrophils/ul) 50-year-old woman on broad spectrum antibiotics grew a yeast. Tests for germ tubes were positive in the microbiology laboratory. What is the likely organism?

  1. Candida albicans
  2. Candida tropicalis
  3. Candida pseudotropicalis
  4. Candida parapsilosis

ANSWER

 

 

 

Micro Case 16

Clinical history: A 44-year-old diabetic woman developed facial pain over the past 24 hours.  She has become lethargic and obtunded. There is swelling with marked tenderness over the left and right maxilla, bilateral exophthalmos, diffuse abdominal pain, poor skin turgor, and dry mucous membranes. Her temperature is 37.7°C. She has tachycardia, but no murmurs, and tachypnea; the lung fields are clear.

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(Summary of Gross and Lab Findings - click here)
Necrosis of the nares is evident along with marked maxillary and peri-orbital swelling. Broad, ribbon-like aseptate hyphae are seen in tissue section stained with PAS.

 

m16-1. What is the MOST LIKELY diagnosis and the best treatment option?

ANSWER

 

m16-2. In a separate case, A 22-year-old with non-Hodgkins lymphoma was profoundly neutropenic after induction chemotherapy and developed fevers. Broad spectrum IV antibiotic therapy was administered, but fevers continued. Chest x-ray showed new bilaterial fluffy pulmonary infiltrates. A bronchoscopy was performed which showed hyaline, septate hyphae with acute-angle branching. What is the MOST LIKELY organism?

  1. Blastomyces dermatitidis
  2. Mucor spp
  3. Candida species
  4. Aspergillus spp

ANSWER

 

 

Micro Case 17

Clinical history: A 50-year-old resident of Phoenix, Arizona, has a cough that has persisted for 1 month.  On physical examination, his temperature is 38.1°C. A chest radiograph shows 3.5-cm opacity with central cavitation in the right apical region.  An open lung biopsy is performed to exclude cancer.

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(Summary of Microscopic Findings - click here)
Microscopic examination of the biopsy specimen shows caseating granulomatous inflammation containing 60-um spherules filled with smaller, rounded structures.

 

m17-1. Which of the following organisms is MOST LIKELY to be responsible for these findings?

  1. Aspergillus fumigates
  2. Coccidioides immitis
  3. Histoplasma capsulatum
  4. Mycobacterium tuberculosis
  5. Pseudomonas aeruginosa

ANSWER

 

 

 

Micro Case 18

Clinical history: For the past 3 weeks, a 52-year-old man has had a chronic cough with a low-grade fever. On physical examination, his temperature is 37.4°C.  A chest radiograph shows bilateral, scattered, 0.3- to 2-cm nodules in the upper lobes and hilar adenopathy.  A fine needle aspirate of one of the nodules shows inflammation with mononuclear cells, including macrophages that, with PAS or silver stains, show intracellular, 2- to 5-um, rounded, yeast-like organisms.

Image Gallery:

(Summary of Gross Findings - click here)
This gross section of lung shows a laminated granuloma.
(Summary of Microscopic Findings - click here)
This silver stained tissue section shows histiocytes in lung tissue.

 

m18-1. Which of the following infectious diseases is MOST LIKELY to produce these findings?

  1. Coccidioidomycosis
  2. Candidiasis
  3. Cryptococcosis
  4. Histoplasmosis
  5. Blastomycosis

ANSWER

 

 

 

Micro Case 19

Clinical history: For the past month, a 68-year-old patient has had painful oral abcesses, fever, and a cough productive of yellow sputum.  On physical examination, there is dullness to percussion at the left lung base. A chest radiograph shows areas of consolidation in the left lower lobe.  Despite antibiotic therapy, the course of the disease is complicated by abscess formation, and he dies.

Image Gallery:

(Summary of Gross Findings - click here)
Abcess observed on chest surface with purulent, granular discharge.
(Summary of Microscopic Findings - click here)
Tissue surrounding the abcess is contains nodules with basophilic cores surrounded by polymorphonuclear leukocytes.

 

m19-1. Based on these clinical findings, what is the BEST diagnosis AND the likely causative agent?

ANSWER

 

m19-2. In a separate case, a middle aged man presented to his physician with a persistent cough of two months following an extended overseas trip to visit relatives. He had also noted a 10 pound weight loss and night sweats. A sputum was sent to the microbiology laboratory for routine bacterial culture and AFB culture. Kinyoun stain of his sputum was positive. What is the likely causative agent?

  1. Mycobacterium tuberculosis
  2. Actinomyces spp
  3. Fusobacterium nucleatum
  4. Nocardia spp.

ANSWER

 

Micro Case 20

Clinical history: A 50-year-old man post lung transplant was admitted to hospital with fever, chills and cough. Chest x-ray showed multiple small abscesses within a right middle lobe infiltrate. The patient had been treated with prednisone and azathioprine daily for rejection. Gram stain of a bronchoalveolar lavage of the right middle lobe shows gram positive rods. Modified acid fast stain shows partially acid fast bacilli.

Image Gallery:

(Summary of Lab & Microscopic Findings - click here)
Gram stain of a bronchoalveolar lavage of the right middle lobe shows gram positive rods. Modified acid fast stain shows partially acid fast bacilli.

 

m20-1. What is the most likely organism?

  1. Mycobacterium tuberculosis
  2. Actinomyces spp
  3. Fusobacterium nucleatum
  4. Nocardia spp.

ANSWER

 

m20-2. Nocardia species are:

  1. branching, gram negative bacilli
  2. partially acid fast, beaded gram positive filaments
  3. acid fast, branching gram negative filaments
  4. partially acid fast, gram variable bacilli

ANSWER

 

 

 

Micro Case 21

Clinical history: An HIV positive male presented in clinic with confusion and disorientation. He had a fever 38.5°C and photophobia. His CD4 count was 80/ul. A lumbar puncture was performed. It showed 32 WBC/ul with 89% lymphocytes, and 6% monocytes, glucose of 22mg/dl, and protein of 89mg/dl. Gram stain showed yeast and India ink showed a thick capsule.

Image Gallery:

(Summary of Lab & Microscopic Findings - click here)
Encapsulated yeast may be seen on India ink stained preparation of cerebrospinal fluid.

 

m21-1. Which of the following is the most likely pathogen?

  1. Cryptococcus neoformans
  2. Hemophilus infulenzae
  3. West Nile virus
  4. Streptococcus pneumoniae

ANSWER


m21-2. In a separate case, A 35-year-old man who received kidney transplantation was being treated with cyclosporine, azathioprine, and high doses of corticosteroids.  While on this regimen, the patient began to experience headaches and became lethargic.  A clinical diagnosis of meningoencephalitis was made.  He died 7 days later.  Autopsy showed a gelatinous meningeal exudate, and on sectioning of the brain, multiple small cyst-like areas were seen.  Microscopic examination showed areas containing rounded structures with a prominent capsule that stained brightly with mucicarmine. 

Image Gallery:

(Summary of Lab & Microscopic Findings - click here)
An H&E-stained section shows granulomatous meningitis.

What is the most likely organism?

  1. Cryptococcus neoformans
  2. Hemophilus infulenzae
  3. West Nile virus
  4. Streptococcus pneumoniae

ANSWER

 

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Updated 02/13/13 - Velkey