Microbiology Case Study: 92-year-old with Itchy Rash

A 92 year old female nursing home resident presented to her primary care physician with an itchy rash between her fingers and at her waist. A skin scrape revealed the following:

Sarcoptes scabiei  (the itch mite) from skin scraping.
Sarcoptes scabiei (the itch mite) from skin scraping.

Laboratory identification:

It is critical that an appropriate specimen is collected for identification of the organism. A fresh unopened papule on the skin should be selected for skin scraping. A scalpel coated in mineral oil should be used to vigorously scrape the papule and transfer the scrapings to a glass slide. A well collected skin scraping draws blood.

Female mites are 330-450 microns long; males are slightly smaller at 200-240. The eggs are thin shelled and approximately 150 x 100 microns in size. It is also possible to see fecal pellets in scrape specimens.

Discussion:

Sarcoptes scabiei is transmitted by direct contact. The gravid female mite burrows into the epidermis leaving behind a trail of up to 40 eggs. The burrowing process is enhanced by the presence of suckers and specialized cutting surfaces on the organism. The larvae hatch in 3-4 days, leave the burrow, and reach adulthood in hair follicles. The typical patient presentation is intense pruritis, often in folds of skin, with possible secondary bacterial infection due to itching and excoriation.

Scabies is treated with aqueous solutions of malathion or permethrin.

-Lauren Pearson, D.O. is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

You Never Know What You Might Find on Peripheral Smear Review

A 15 month patient was seen in the Pediatric Hematology-Oncology clinic in June 2014 for mild normocytic anemia.

Review of Systems

Negative 12 system review. No history of pallor, jaundice or high colored urine.

Ref. Range 6/14
WBC 6-17 K/uL 11.4
Hemoglobin 10.5-13.5 g/dL 8.9 (L)
Hematocrit 33-39 % 25.4 (L)
Platelets 150-400 K/uL 648 (H)
RBC 3.7-5.3 M/uL 3.57 (L)
MCV 70-86 fL 71.2
MCH 23-30 pg 24.9
MCHC 31-36 % 34.9
RDW 11.5-14.5 % 16.4 (H)

His serum iron profile was normal, serum lead levels were normal. Reticulocyte percentage and absolute reticulocyte count were also both not elevated.

Review of peripheral smear revealed moderate anisopoikilocytosis with presence of numerous elliptocytes.

he1

he2

Molecular studies demonstrated a heterozygous mutation in the EPB41 gene associated with HE.

Patient was diagnosed with Hereditary Elliptocytosis (HE).

He has been followed up at the hematology clinic for a year now. His follow up CBC results are as follows. He has reached his age appropriate milestones and continues to grow well.

Ref. Range 7/14 10/14 12/14 4/15
WBC 6-17 K/uL 10.3 11.3 7.4 10.0
Hemoglobin 10.5-13.5 g/dL 9.3 (L) 9.9 (L) 9.7 (L) 11.0
Hematocrit 33-39 % 26.5 (L) 28.7 (L) 28.1 (L) 33.6
Platelets 150-400 K/uL 599 (H) 570 (H) 403 (H) 447 (H)
RBC 3.7-5.3 M/uL 3.74 3.91 3.87 4.58
MCV 70-86 fL 70.8 73.3 72.6 73.5
MCH 23-30 pg 24.8 25.4 25.1 23.9
MCHC 31-36 % 35.0 34.7 34.5 32.6
RDW 11.5-14.5 % 16.9 (H) 17.7 (H) 18.2 (H) 18.0 (H)

Hereditary elliptocytosis (HE) is an inherited hemolytic anemia, secondary to red cell membrane defect more commonly assembly of spectrin, spectrin-ankyrin binding, protein 4.1 and glycophorin C with a clinical severity ranging from asymptomatic carriers to a severe hemolytic anemia. It is more common in individuals from African and Mediterranean decent – neither applies to our patient.It is inherited in an autosomal dominant pattern, typically individual who are heterozygous are asymptomatic while those who are homozygous or compound heterozygous have a mild to severe anemia. Occasional patients with more severe hemolysis may require splenectomy.

Regardless of the underlying molecular abnormality, most circulating red cells are elliptical or oval. They still have an area of central pallor, since there is no loss of the lipid bilayer (as seen in Hereditary spherocytosis).

Vajpayee,Neerja2014_small

-Neerja Vajpayee, MD, is an Associate Professor of Pathology at the SUNY Upstate Medical University, Syracuse, NY. She enjoys teaching hematology to residents, fellows and laboratory technologists. 

Microbiology Case Study: 38-Year-Old with Intermittent Straight Catheterization

Case History:

A 38 year old man with history of secondary progressive multiple sclerosis complicated by neurogenic bladder requiring intermittent straight catheterization presented with fevers, chills, and weakness. Clinical evaluation revealed hypotension and leukocytosis concerning for sepsis. His urinalysis was positive for 3+ blood, 1+ leukocyte esterase and nitrites. Urine was sent to our laboratory for culture and grew bacteria with the below gram stain and colony morphology.

Gram stain showing gram negative bacilli.
Gram stain showing gram negative bacilli.
Sheep blood agar growing nonhemolytic grey-yellow mucoid bacterial colonies.
Sheep blood agar growing nonhemolytic grey-yellow mucoid bacterial colonies.
MacConkey agar growing mucoid lactose fermenting (pink) bacterial colonies.
MacConkey agar growing mucoid lactose fermenting (pink) bacterial colonies.

 

Laboratory identification:

Klebsiella and Raoultella both are gram negative bacilli that form lactose fermenting, yellow, mucoid bacterial colonies. The bacterial colonies appear mucoid because of the bacteria’s polysaccharide capsule. Distinguishing these two types of bacteria requires molecular analysis as their morphology can be identical. In our initial identification process, only one type of bacteria was detected on the urine culture. Given the gram stain and colony morphology, our differential included Klebsiella, Enterobacter, and Roaultella. The bacteria was verified as Roaultella species using mass spectrometry. However, our laboratory also received two sets of blood cultures which showed the same morphology as above but the bacteria was identified as K. oxytoca. This prompted a review of the urine culture in which a subtle second bacterial colony morphology was seen and confirmed as K. oxytoca.

Discussion:

In summary, our patient had a urinary tract infection caused by Roaultella and Klebsiella which was the source of the patient’s sepsis. Only the Klebsiella was detected in his blood stream. Raoultella and Klebsiella are both gram negative, oxidase negative, non-motile, capsulated, facultative anaerobic bacilli within the Enterobacteriaceae family. Raoultella was initially classified within the Klebsiella genus, but reclassified based on comparative analysis of the 16S rRNA gene and rpoB gene which encodes the β subunit of bacterial RNA polymerase. Members of the Raoultella genus include R. electrica, R. terrigena, R. planticola, and R. ornithinolytica and are found in the environment, specifically in plants, soil, and water. Raoultella species are rare in human disease but have been documented to cause bacteremia, urinary tract infection, conjunctivitis and cholecystitis.

Klebsiella causes human disease much more frequently than Roaultella. Klebsiella are part of human oropharynx and gastrointestinal flora that act as opportunistic pathogens. Mode of transmission may occur endogenously or through person to person spread, hence nosocomial infections are common. K. oxytoca and K. pneumoniae are the most frequently implicated species in human disease and may cause a wide spectrum of infections such as urinary tract infections, respiratory infections, enteritis, meningitis and bacteremia.

For our patient, we reported antibiotic sensitivities that were susceptible to both types of bacteria. The patient was treated with ceftriaxone and then transitioned to cefpodoxime with resolution of his urosepsis. In general, Raoultella’s susceptibility to antimicrobial agents are not well studied and should be based on the antibiotic sensitivities of each strain. In contrast, Klebsiella is well documented to have increasing antimicrobial resistance. Most clinical strains are resistant to ampicillin, carbenicillin and ticarcillin as well as extended spectrum beta-lactam drugs. Resistance to beta-lactam drugs is the result of Klebsiella bacteria that harbor plasmids which produce beta-lactamase enzymes.

 

-Jill Miller, MD is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

 

 

Microbiology Case Study–35-Year-Old with a Puncture Wound

Case History:

A 35 year old healthy man presented with a puncture wound of the left hand. He was bit by his neighbor’s dog. Fluid expressed from the wound was sent to the microbiology laboratory with the following gram stain and colony morphology.

past1
Gram stain showing small gram negative coccobacilli.
Sheep blood agar with smooth, gray, non-hemolytic bacterial colonies.
Sheep blood agar with smooth, gray, non-hemolytic bacterial colonies.

 

Laboratory Identification:

Bacterial colonies, as shown above, grew on sheep blood and chocolate agars. No growth was present on CNA or MacConkey agars which in combination with the gram stain indicated a type of fastidious gram negative bacteria. Additionally, the bacterial colonies were oxidase positive, catalase positive and indole positive. These findings were consistent with Pasteurella species and confirmed to be P. multocida by mass spectrometry.

Discussion:

Pasteurella species are nonmotile, gram-negative, facultative anaerobic coccobacilli or rods. P. multocida is the most common species involved in human disease. P. multocida is part of the normal oropharyngeal flora in multiple animals including cats, dogs, cattle, horses, rodents and other animals. This bacteria has been reported in up to 70-90% cats and 40-60% of dogs. Humans who have frequent exposure to animals may also harbor P. multocida as part of their normal flora.

Pasteurella are opportunistic pathogens that require mechanical disruption of host barriers. The vast majority of P. multicida related diseases are wound infections and/or cellulitis as a result of a cat bite or scratch. Transmission of Pasteurella also occurs in partially healing wound or regions of poor skin integrity that are licked by a cat or dog. Pasteurella infections may be complicated by septic arthritis and osteomyelitis if wounds are deep and inoculate the underlying soft tissue. Patients who are immunocompromised may develop bacteremia with more widespread infections. The majority of Pasteurella species are susceptible to penicillin, cephalosporins and tetracycline. Our laboratory does not report antibiotic sensitivities for P. multocida for a few reasons: Pasteurella is rarely resistant to penicillin, and bite wounds are generally mixed infections.

 

-Jill Miller, MD is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

Make the Diagnosis–A 58 Year Old Male with Abdominal Pain

A 58-year-old male presents with abdominal pain and bloody diarrhea which had a gradual onset over the last 3 weeks. He has lost 8 pounds during this period of time. A cecal biopsy is performed, and a representative section is shown here. What is the most likely diagnosis?

amoebiasis1

  1. Amoebiasis
  2. Ascariasis
  3. Candidiasis
  4. Cryptosporidiosis
  5. Giardiasis

The diagnosis in this case is amoebiasis. The most common cause of amebic enterocolitis is Entamoeba histolytica, an organism spread through ingestion of cysts in contaminated food or water. The trophozoite forms are round, and frequently show intracytoplasmic red cells.

Amoeba with intracytoplasmic red cells
Amoeba with intracytoplasmic red cells

Occasionally, the organisms invade other organs, such as the liver, lung, and heart. Most patients may be treated on an outpatient basis, unless there is severe colitis or extraintestinal disease.

The organisms frequently invade through the mucosa and into the submucosa, often with lateral extension.

"Flask-shaped" ulcer in amoebiasis
“Flask-shaped” ulcer in amoebiasis

Occasionally, the organisms invade other organs, such as the liver, lung, and heart. Most patients may be treated on an outpatient basis, unless there is severe colitis or extraintestinal disease.

Krafts

-Kristine Krafts, MD, is an Assistant Professor of Pathology at the University of Minnesota School of Medicine and School of Dentistry and the founder of the educational website Pathology Student.

Microbiology Case Study–Upper Thigh Pain

An 85 year old man presented with right medial upper thigh pain and swelling.  Imaging revealed a large pseudoaneurysm in the right superficial femoral artery with evidence of rupture. The patient was taken to the operating room for placement of a gortex stent graft. His postoperative course was complicated by development of a large hematoma at the surgical site. Incision and drainage of the hematoma was surgically performed and fluid from the hematoma was sent to the microbiology laboratory.

Gram stain with multiple gram negative bacilli.
Gram stain with multiple gram negative bacilli.
White-grey bacterial colonies growing on blood agar plate.
White-grey bacterial colonies growing on blood agar plate.
Grey semi-translucent non-lactose fermenting colonies growing on MacConkey agar.
Grey semi-translucent non-lactose fermenting colonies growing on MacConkey agar.

 

Laboratory Identification:

The gram stain and plates confirmed the bacteria were non-lactose fermenting, non-hemolytic gram negative bacilli which is consistent Salmonella. Salmonella species was confirmed by mass spectrometry. Another feature helpful in the identification of Salmonella is its ability to produce hydrogen sulfide. Although not performed in this case, Salmonella will produce colonies with black centers when grown on Xylose lysine deoxycholate agar (selective agar that has thiosulfate which Salmonella metabolize to hydrogen sulfide).

The bacterial isolates of Salmonella were forwarded to the public health laboratories where serotype is determined based on serologic reactions to O and H antigens. The O antigen is the most external component of the lipopolysacccharide of gram negative bacteria and the H antigen is the antigenic determinant that makes up the flagellar subunits . This Salmonella species was identified to be S. enteritidis. Two sets of the patient’s blood cultures also grew S. enteritidis.

Discussion:

Salmonella are motile, gram negative bacilli that are widely disseminated in nature. Various animals such as turtles, lizards, snakes and birds are associated with Salmonella. Salmonella may infect humans via ingestion of contaminated food products that are typically of poultry or dairy origin. Person to person transmission may also occur by fecal-oral route. Salmonella has multiple virulence factors that allow it to evade the immune system. One of its virulence factors is the polysaccharide capsule that surrounds the O antigen. The O antigen is highly immunogenic and shielding the O antigen prevents its recognition by antibodies. Additionally, Salmonella can periodically change its H antigen as another protective mechanism against antibodies.

 

Jill Miller, MD is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

Christi Wojewoda, MD, is certified by the American Board of Pathology in AP/CP and Medical Microbiology. She is currently the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

 

Microbiology Case Study–Abdominal Pain

A 60 year old man presented with abdominal pain and bloody diarrhea. He denied fever, chills, nausea, vomiting or recent travel. A stool culture was sent to the microbiology laboratory.

Colony Gram stain showing Gram-negative bacilli
Colony Gram stain showing Gram-negative bacilli
Grey-white bacterial colonies growing on a blood agar plate.
Grey-white bacterial colonies growing on a blood agar plate.
Fuschia colonies growing on CHROMagar O157.
Fuschia colonies growing on CHROMagar O157.

 

Laboratory Identification:

E. coli O157:H7 is most likely to be detected in the acute phase of illness and may be missed after 5-7 days from onset of symptoms. In general, laboratory identification is based on the detection of Shiga toxin-producing strains or detection of the O157:H7 serotype through various methodologies. In our laboratory, we identified E. coli O157 based on the above gram stain and colony morphology in combination with growth with the appropriate color on a selective plate for E. coli O157, CHROMagar O157. We used our automated microbial identification system, Vitek 2, which performs multiple biochemical reactions to confirm the bacteria as E. coli O157:H7. Additionally, we identified the presence of Shiga toxin through an immunochromatographic lateral flow rapid test using monoclonal antibodies specific to Shiga toxins.

 

Discussion:

E. coli are gram negative rods that are beta hemolytic, indole positive and lactose fermenters. E. coli is part of the normal colon flora but certain types of E. coli can cause disease depending on their virulence factors. Enterohemorrhagic E. coli (EHEC), also known as Shiga toxin producing E.coli (STEC), is one of six major groups of E. coli that causes diarrhea. EHEC produce a Shiga toxin that inhibits protein synthesis of intestinal epithelial cells via inhibition of the 60S ribosome. The most common serotype is E. coli O157:H7. Transmission occurs through ingestion of raw milk or uncooked ground beef. Hamburgers have been the cause of many outbreaks of infection in the United States although majority of E. coli O157:H7 infections are not associated with outbreaks.

Clinical manifestations from E. coli O157:H7 infection usually occurs at three days from time of exposure but may vary from one to eight days. Clinical symptoms typically begin with abdominal cramps, vomiting, and bloody diarrhea without fever. However, patients may experience a spectrum of disease ranging from asymptomatic infection (less common) to hemorrhagic colitis with progression hemolytic-uremic syndrome (HUS). HUS is the most common cause of acute renal failure in children and results from toxin-mediated damage of endothelial cells in the kidney. HUS is characterized by the triad of acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia. Supportive therapy is recommended for treatment of E. coli O157:H7 infections. Antibiotics are not recommended because of the potential to increase Shiga toxin production. For this reason, we do not report antibiotic sensitivities for E. coli O157:H7.

 

Jill Miller, MD is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

Christi Wojewoda, MD, is certified by the American Board of Pathology in AP/CP and Medical Microbiology. She is currently the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.