Microbiology Case Study: A 52 Year Old Woman’s Routine Colonoscopy Results

A 52 year old woman with no significant past medical history presented for a routine colonoscopy screening. During the colonoscopy, the mucosa of the colon was abnormal with a vascular pattern that was distorted. There were whitish punctate lesions, particularly in the right colon and a biopsy was taken.

H&E stain of colon biopsy
H&E stain of colon biopsy
H&E stain of colon biopsy
H&E stain of colon biopsy

Based on the microscopic morphology, a diagnosis of schistosomiasis was made. Evaluation of the morphology reavealed lateral spines which is consistent with the diagnosis of Schistosoma mansoni.

Schistosomiasis is a disease caused by infection with parasitic blood flukes. The parasites that cause schistosomiasis live in certain types of freshwater snails. The infectious form of the parasite is known as cercariae. Individuals can become infected when skin comes in contact with contaminated water and is penetrated by cercariae.

Five schistosome species can cause infection in humans:

  • Schistosoma mansoni (Africa and South America)
  • S. japonicum(East Asia)
  • S. haematobium(Africa and Middle East).
  • S. mekongi(Laos, Cambodia)
  • S. intercalatum(West and Central Africa);

The adult worms travel against portal blood flow to the mesenteric venules of the colon. The male schistosome forms a groove for the female in which mating occurs, and in 1-3 months, the females deposit eggs in the small venules of the mesenteric or perivesical systems. The eggs of S. mansoni and S. japonicum move toward the lumen of the intestine while the eggs of S. haematobium move toward the bladder and ureters. They leave the body in feces or urine. Adult worms have an average lifespan of 5-7 years but have been known to survive up to 30 years

S. mansoni and S. japonicumgenerally cause intestinal tract disease and S. haematobiumcauses genitourinary tract disease. More than 200 million people have been infected, leading to approximately 200,000 deaths per year.

Most people infected do not develop symptoms, however infection can lead to swimmer’s itch, acute schistosomiasis syndrome (sudden onset of fever, urticaria and angioedema, chills, myalgias, arthralgias, dry cough, diarrhea, abdominal pain, and headache), and intestinal schistosomiasis (abdominal pain, poor appetite, and diarrhea).

The acute phase of infection is treated with corticosteroids. Praziquantel should be started after acute symptoms have resolved and should be given with corticosteroids.

 

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

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-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: Asymptomatic 12 Year Old Girl

A 12 year old girl who recently emigrated from Nepal was seen in clinic to establish care. She was entirely asymptomatic. Stool ova and parasite exam was performed and on the permanent trichrome-stained section, the following parasites were identified.

 

Image (A)
Image (A)
Image (B)
Image (B)
Image (C)
Image (C)
Image (D)
Image (D)
Image (E)
Image (E)

Laboratory Identification:

The first image (A) is morphologically diagnostic for Dientamoeba fragilis trophozoites. They are approximately 10 microns in diameter and have 1-2 nuclei, which appear fractured. The next two images are diagnostic for Endolimax nana cysts (B) and trophozoites (C). The cysts are approximately 7 microns in diameter and most have 4 nuclei with blot-like karyosomes that are red on trichrome stain with clearing around the nuclei. The trophozoites are approximately 10 microns in diameter with a single large blot-like karyosome that is red on trichrome stain. The last two images are diagnostic for Entamoeba coli cysts (D) and trophozoites (E). The cysts are approximately 20 microns in diameter and have five to eight nuclei with karyosomes that are red on trichrome stain. The trophozoites are approximately 22 microns in diameter and have a single nucleus with a large kayosome that is darkly staining on trichrome stain. There is peripheral chromatin that is ring-like or clumped.

Discussion:

Dientamoeba fragilis, an ameboflagellate, is a potential pathogen that can be associated with diarrhea, vomiting, abdominal pain, and anorexia, particularly in children. Transmission is via ingestion of contaminated food and water. Some studies postulate co-transmission via helminth eggs, particularly with Enterobius vermicularis. Historically, this intestinal parasite is only known to have a trophozoite form. However, there are now case reports describing the presence of cysts and precysts in humans.1 Treatment is with metronidazole or paromomycin in patients who are symptomatic.

Endolimax nana and Entamoeba coli are protozoa that are considered non-pathogenic and therefore no treatment is necessary. However, when identified, they should be reported since their presence indicates exposure to contaminated food and water. Transmission is via ingestion of cysts. Once in the small bowel, they ex-cyst and migrate to the large bowel where they divide by binary fission and produce cysts. Both cysts and trophozoites are passed in stool.

Reference

  1. Stark D, Garcia LS, Barratt JLN, Phillips O, Roberts T, Marriot D, Harkness J, Ellis JT. Description ofDientamoeba fragilis cyst and precystic forms from human samples. Journ Clin Micro. 2014; 52: 2680-2683.

 

-Joanna Conant, MD is a 4th year anatomic and clinical pathology resident at the University of Vermont Medical Center.

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-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.

Doctor, There’s a Snake in My Poop

Case history:
A mother brought her 5 year old son into his pediatrician with a “snake” that she found in his stool. Otherwise, the patient was completely asymptomatic.

Specimen sent for ID:

ascaris1

ascaris2

Ascaris is the most common Helminth affecting humans. It is also the largest of the roundworms (nematodes), growing up to 35 cm in length. There are several species of Ascaris however only A. lumbricoides affects humans.

Epidemiology
Ascaris occurs in areas with poor sanitation, hygiene and solid waste practices. Worldwide it is most common in tropical and subtropical areas.

Transmission & Life Cycle
Ascaris is transmitted through the fecal-oral route, and is therefore most prevalent in areas with poor sanitation and waste practices. Transmission occurs when an uninfected person swallows a fertilized egg which was originally passed through the stool of an infected person.

The adult male and female forms live in the small intestine. The female passes up to 200,000 eggs per day. If there is also a male worm living in the small intestine, these eggs may then be fertilized. Both fertilized and unfertilized eggs are eventually passed in the stool.

Unfertilized eggs are not infective and do not cause disease if ingested. Fertilized eggs are only infective after approximately three weeks of maturation. The exact amount of time required before the fertilized egg becomes infective will depend on environmental conditions, such as temperature and humidity.

Once ingested, the fertilized egg travels to the small intestine, where it hatches and becomes a larva. The larval form invades the small intestinal mucosal wall and enters the bloodstream. Upon reaching the lung, the larva invades the capillary and alveolar walls and continues to grow within the alveoli. After about two weeks of maturation, the larva then migrates up through the airspaces and into the trachea, where it is eventually swallowed and transported back down into the small intestine. The fully mature larval forms are now adult worms and will continue to live in the small intestine for the rest of their lifespan (up to 1 to 2 years).

Laboratory Diagnosis
In most cases, Ascaris is diagnosed in the egg form on ova and parasite exam. The fertilized egg is round, 45-70 microns in diameter and has a thick, mammillated outer wall which stains brown with bile. The unfertilized egg is larger (90 microns), are has a more oval shape with a less regular mammillated contour. Patients may also pass adult worms in the stool or less commonly they may cough them up through the mouth. The adult worms have tapered ends with a three-lipped mouth (“tricuspid” mouth). The female is larger than the male (female: 20-35 cm, male: 15-30 cm).

Clinical Symptoms
Clinically, most people affected with Ascaris are asymptomatic. With a very high worm load however patients may begin to develop complications related to obstruction, including abdominal pain, constipation, appendicitis and obstructive cholangitis. In younger children infection with Ascaris may result in stunted growth. Of note, immune reaction to larva in the lung may result in an eosinophilic immunologic response known as Löffler’s pneumonitis.

Treatment
Ascaris is treated with anthelminthic medication (albendazole, mebendazole or ivermectin). Therapy for Ascaris extremely effective and rids the patient of all adult, larval and egg forms.

-Javier De Luca-Johnson, MD is a 2nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

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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.