Microbiology Case Study: A Man with History of ALL Presents with Fever and Diarrhea

Clinical History

A man in his 40’s with a past medical history of acute lymphoblastic leukemia/lymphoma (in remission), multiple infections including bacteremia and pulmonary aspergillosis, presented to the hospital with fever and diarrhea. Over the course of his stay, he had worsening renal function and developed profound hypotension and shock, which prompted initiation of two vasopressors and high-dose steroids. Eventually he developed acute hypoxic respiratory failure, requiring intubation. Complete blood count demonstrated an absolute eosinophilia of 8.58 x109/L (reference range 0.04-0.62 x109/L). Imaging revealed bilateral pulmonary infiltrates and a pleural effusion. Respiratory culture with gram stain was ordered for his tracheal aspirate, which revealed few polymorphonuclear cells, many gram-negative rods, yeast, and larvae of Strongyloides stercoralis (Image 1A). Wet mounts of the tracheal aspirate revealed numerous larvae and a few eggs of S. stercoralis (Image 1B-C); many of the larvae were motile (Movie 1). Stool examination of ova and parasites (O & P) were positive for larvae. Given the burden of organisms and prior administration of steroids, he was diagnosed with severe strongyloidiasis, consistent with hyperinfection. Concurrent blood cultures grew Enterococcus faecalis and Stenotrophomonas maltophilia; the respiratory culture also grew S. maltophilia, and tracks from the migrating larvae were observed on respiratory culture bacterial media (Image 1D).

Image 1. Tracheal aspirate Gram stain with S. stercoralis larvae, 100x objective magnification (A). Wet mount of tracheal aspirate revealing larvae (B) and eggs (C), 40x objective magnification. Blood agar plate growing S. maltophilia in an abnormal pattern, indicating motile larvae tracking through the agar (D).

Discussion

Strongyloidiasis is a spectrum of clinical disease caused by the nematode Strongyloides stercoralis.1,2 Descriptions of acute infection have been described in other Lablogatory entries here,3,4 and the full lifecycle is described in detail on the CDC DPDx website.5

Severe strongyloidiasis includes the syndromes of hyperinfection and disseminated disease. Hyperinfection is when there is an elevated burden of the typical autoinfection cycle involving the lungs and GI-tract. Usually there is an antecedent immunosuppressive event, such as administration of corticosteroids. Within the GI-tract lumen, increased numbers of rhabditiform larvae transform into the infective filariform larvae, which traverse the GI mucosa, migrate to the lungs via bloodstream/lymphatics where they enter alveolar air spaces, then ascend the respiratory tract, and are coughed up by the host and swallowed to re-enter the GI tract. In the GI tract adult females lay eggs through parthenogenesis, which give rise to further rhabditiform larvae. In extreme cases of hyperinfection, adults can be found in the lungs, where they may also lay eggs. Finding eggs in respiratory specimens is unusual, and may be related to the burden of disease.6

Disseminated disease is when larvae can be found in any additional organs/organ systems, such as the central nervous system, kidneys, liver, adrenals, etc. Invasive sampling is not typically performed, and larvae can be observed at autopsy.

Laboratory diagnosis of S. stercoralis involves identification of rhabditiform larvae in stool O &P exam; the presence of adults or eggs in stool is rare. Rhabditiform larvae have short buccal cavities and an ovoid genital primordium structure midway through the body (Movie 2). O&P exams can be performed on other body fluids, such as sputum and CSF. Serology can be useful to identify past exposure, especially prior to initiating immunosuppressive therapeutics such as corticosteroids. A nonspecific finding can be observed, as in this case, in the complete blood cell count and differential. Relative and absolute eosinophilia can be found in patients with parasitic infections; therefore, it is reasonable to rule out parasitic infection in this subset of patients. In the case presented here, the absolute eosinophilia was likely due to a persistent S. stercoralis infection, since these nematodes can live in the human host for decades.

The treatment of choice for severe strongyloidiasis is oral ivermectin, though albendazole is an alternative therapy. In some instances, subcutaneous ivermectin administration may be used.7

Follow-up

Oral ivermectin was administered to treat the strongyloidiasis and antibiotics were administered to treat the bacterial infections. Over the coming days, serial tracheal aspirates continued to reveal many larvae and eggs, so therapy was escalated to subcutaneous ivermectin. Over the course of therapy, the patient developed a fungemia with Candida guilliermondii. Despite aggressive antimicrobial therapy and intensive care, the patient remained hypoxemic and hypotensive. The family decided to transition to comfort measures and the patient passed away.

References

  1. Maguire JH. Intestinal Nematodes (Roundworms), in Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, B. Mandell, Dolin, Editor. 2010, Elsevier: Philadelphia, PA. p. 3577-3586.
  2. Parasitology, in Koneman’s Color Atlas and Textbook of Diagnostic Microbiology, Procop et al., Editors. 2017, Lippincott Williams & Wilkins: China. p. 1452-1454.
  3. Kaur J, Stempak L. An 81 Year Old Female with Persistent Fevers. Lablogatory 2019 [cited 2019 11/5/2019]; Available from: https://labmedicineblog.com/2019/04/23/microbiology-case-study-an-81-year-old-female-with-persistent-fevers/.
  4. Mohammed M, Wojewoda C. A 47 Year Old Male with Abdominal Pain and Diarrhea. Lablogatory 2016 [cited 2019 11/5/2019]; Available from: https://labmedicineblog.com/2016/05/16/microbiology-case-study-a-47-year-old-male-with-abdominal-pain-and-diarrhea/.
  5. Centers for Disease Control. Strongyloidiasis. DPDx 2019 [cited 2019 11/5/2019]; Available from: https://www.cdc.gov/dpdx/strongyloidiasis/index.html.
  6. Keiser PB and Nutman TB. Strongyloides stercoralis in the Immunocompromised Population. Clin Microbiol Rev, 2004. 17(1): p. 208-17.
  7. Hurlimann E and Keiser J, A single dose of ivermectin is sufficient for strongyloidiasis. Lancet Infect Dis, 2019. 19(11): p. 1150-1151.

-IJ Frame, MD, PhD, Microbiology Fellow, University of Texas Southwestern Dallas, Texas

-Clare McCormick-Baw, MD, PhD is an Assistant Professor of Clinical Microbiology at UT Southwestern in Dallas, Texas. he has a passion for teaching about laboratory medicine in general and the best uses of the microbiology lab in particular.

Microbiology Case Study: An 18 Year Old with Fever, Chills and Abdominal Pain

Clinical History

An 18 year old male presented to the emergency department (ED) with fever, chills, and generalized lower abdominal pain. He noted the fever began 6 days ago and had been intermittent since that time. He also reported nausea and vomiting with a decrease in appetite. The patient was from India and was treated for malaria 8 months ago, directly prior to arrival in the United States. He stated he received three days of intravenous medications with resolution of symptoms. In the ED, his vitals were blood pressure 129/75, heart rate 133, temperature 104.1°F, respirations 20, and 99% oxygen saturation on room air. On physical exam, patient had mild jaundice and scleral icterus and severe right lower quadrant pain on palpation. CT scan of the abdomen showed mesenteric adenitis, but no appendicitis. Initial laboratory testing showed a mild anemia and thrombocytopenia (hemoglobin 12.1 g/dL, hematocrit 35.9%, platelets 78,000 TH/cm2) and increased indirect bilirubin (2.67 mg/dL). The patient received piperacillin-tazobactam while blood and urine cultures as well as a malaria smear were pending.  

Laboratory Identification

The BinaxNOW lateral flow immunochromatographic assay for Plasmodium spp. was performed.

Image 1. The BinaxNOW assay was positive for malaria protein antigen, representing P. vivax, P. ovale, P. malariae, or a mix of these species.
Image 2. A thin smear showed amoeboid gametocytes in enlarged red blood cells as compared to uninfected cells (Giemsa stain, 100x oil immersion).
Image 3. A thin smear showed very rare trophozoites with thick chromatin bands and single, large chromatin dots (Giemsa stain, 100x oil immersion).

The positive BinaxNOW results and morphologic findings on smear review were most consistent with a P. vivax infection. The level of parasitemia was approximately 0.2%. Blood and urine cultures were negative.

Discussion

Malaria classically presents with fever and chills, weakness, headache, myalgias, nausea, and vomiting in patients who live in tropical and subtropical regions. The four most common species that infect humans through transmission by the female Anopheles mosquito include P. falciparum, P. vivax, P. ovale, and P. malariae. If malaria is not diagnosed and treated in a timely manner, complications including anemia, thrombocytopenia, renal failure, acute respiratory distress syndrome (ARDS), and cerebral malaria can result. P. falciparum is the most deadly species due to the parasite’s ability to cause high levels of parasitemia.  

In laboratories in the United States, malaria testing often times incorporates Plasmodium spp. antigen detection via the BinaxNOW assay and peripheral blood smears. While the performance of the BinaxNOW is acceptable, particularly for P. falciparum, thick and thin peripheral blood smears remain the gold standard for malaria diagnosis, especially when the parasitemia level is low. The thick blood smear allows for screening a large amount of blood for malarial parasites and the thin smear allows for species identification and assessment of parasitemia. Ideally, multiple blood smears obtained from different times of the day should be collected in order to exclude the diagnosis. The window prior to a febrile spike is the best time to obtain the specimen, as the number of circulating parasites is greatest.

Clinically, the most important distinction is between P. falciparum and all other species. A number of features including the morphology of the trophozoites, schizonts, and gametocytes, size of the infected red cells, the presence of multiply infected red blood cells, and the region that the patient lives in or traveled to are helpful in determining species level identification.

P. vivax infects enlarged, young red blood cells and multiple trophozoites may be present in one red blood cell. The trophozoites have thick, blue cytoplasm and usually one, large chromatin dot. The schizont can contain 12 to 24 merozoites and the gametocyte is large and oval in shape. Schuffner’s stippling and malarial pigment are common. It is important to correctly identify P. vivax and P. ovale as they have hypnozoite forms in the liver and patients can relapse unless they are treated with an additional medication to eradicate these forms.

In the case of our patient, he received chloroquine, the treatment of choice for P. vivax arising in India. Primaquine and tafenoquine are both options for eradication of the hypnozoite form in the liver. These medications can cause hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency so quantification of the enzyme is required prior to administering therapy. Our patient had normal G6PD levels and received tafenoquine as well. 

-Karla Perrizo, MD, is a clinical pathology resident at the University of Mississippi Medical Center.

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the Director of Clinical Pathology as well as the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement, and resident education.

Microbiology Case Study: An 81 Year Old Female with Persistent Fevers

Case History

The infectious disease service was consulted on an 81 year old female for persistent fevers. She initially presented a few weeks prior with cough & shortness of breath which was diagnosed as an acute chronic obstructive pulmonary disease (COPD) exacerbation for which she received levofloxacin and steroids. The patient continued to have a persistent cough and dysphagia after discharge. Her respiratory status and cough worsened and she was readmitted and intubated. Vancomycin, piperacillin/tazobactam and levofloxacin were started as well as fluconazole for suspected esophageal candidiasis. Her past medical history was significant for breast cancer, atrial fibrillation, and diabetes mellitus. Of note, patient was originally from Puerto Rico but moved to the United States 40 years ago and denied recent travel and any known tuberculosis exposures. She formerly worked in a deli packing cheeses. A bronchoscopy was performed and a brochoalveolar lavage (BAL) specimen as well as blood and stool specimens were submitted for bacterial culture and ova and parasite exam.

Laboratory Identification

Image 1. Multiple larval forms in the stood specimen from an ova and parasite exam. (Iodine stain, 100X).
Image 2. High power of the larvae with a short buccal cavity (red arrow) and prominent genital primordium (blue arrow), (Iodine stain, 1000x).

The bronchoscopy revealed a bloody fluid admixed with clots which was clinically consistent with diffuse alveolar hemorrhage. The roundworms depicted above were identified in both the BAL and stool O&P exam. Based on the presence of the short buccal cavity and the prominent genital primordium and the absence of eggs, the identification of Strongyloides stercoralis was made. Given the large amount of larvae present in both the lungs and gastrointestinal tract, the patient was diagnosed with a strongyloidiasis hyperinfection.  

Discussion

Strongyloides stercoralis is classified as a nematode (roundworm) and is the cause of strongyloidiasis in humans. The helminth is found worldwide, especially in warm climates and underdeveloped countries, and is the cause of 30-100 million infections. Infection is due to fecal contamination of soil, where free-living forms are found, or water. Infective filariform larvae penetrate intact skin, particularly bare feet, resulting in infection. The free living cycle begins with the rhabditiform larvae passed through the stool develops into the infective filariform larvae or when the  rhabditiform larvae mature into free living adult male & female forms that mate and produce eggs which then hatch and become infective filariform larvae that can infect humans. The parasitic life cycle begins with the infective filariform larvae penetrates human skin. The worm is then either coughed up from the lungs and swallowed or migrates to the small intestine where eggs are laid and hatch.

Patients may present with gastrointestinal symptoms such as abdominal pain, bloating, and diarrhea, pulmonary symptoms like dry cough and throat irritation, or skin rashes along points of entry (feet, ankles). When the larvae are in the lung, Loeffler’s syndrome, characterized by pneumonia symptoms with coughing and wheezing, may develop due to an accumulation of eosinophils in response to the parasitic infection. In patients who are immunocompromised, the rhabditiform larvae can develop into the filariform larvae in the host and can directly penetrate the bowel mucosa or perianal skin resulting in autoinfection, dissemination throughout the body, and high parasite burden. Symptoms of hyperinfection include bloody diarrhea, bowel perforation, destruction of lung parenchyma with bloody sputum, meningitis, and septicemia. Hyperinfection most commonly occurs after steroid administration for asthma or COPD exacerbation, but can also be seen in those receiving chemotherapy or who have had organ transplants.  

In the laboratory, the diagnosis of S. stercoralis is most often made by an ova and parasite exam of the stool, duodenal fluid, sputum or BAL specimens (Image 1). Most commonly the rhabditiform larvae are present and are identified by the presence of a short buccal cavity and prominent genital primordium (Image 2). These two features are helpful in distinguishing S. stercoralis from hookworms (Ancylostoma spp. and Necator americanus) which have a longer buccal cavity and indistinct genital primordium. The eggs of these two nematodes are also very similar, although typically S. stercoralis eggs hatch before they are passed in stool specimens. S. stercoralis can also be visualized on H&E histology sections in the crypts of intestinal biopsies where the adult female measures up to 2.2 mm in length. Finally, serologic testing can be helpful when there is a high suspicion of disease in the face of multiple negative stool exams, but cannot distinguish between a current or past infection. Most patients do not remember a specific exposure and prevention includes wearing gloves and shoes when handling or walking on soil that may contain contaminated fecal material. Treatment options for an acute or chronic S. stercoralis include a short course of ivermectin or albendazole. In the case of disseminated infection, ivermectin should be given until stool and sputum exams are negative for 2 weeks. In the case of our patient, she was started on ivermectin, but succumbed to the disease due to extensive pulmonary hemorrhage.   

-Jaswinder Kaur, MD, is a fourth year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center. 

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the Director of Clinical Pathology as well as the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement, and resident education.

Microbiology Case Study: A 55 Year Old Woman with Cough and Headache

Clinical History

A 55 year old female presented to the gastroenterology clinic with a chief complaint of cough and headache. She reported no recent fevers, abdominal pain, or diarrhea. On further questioning she revealed she was originally from the Philippines and had a past history of a parasitic infection that was treated twice with praziquantel. She did not remember the name of the parasite but was concerned for a recurrent infection. A stool specimen for ova & parasite exam and basic laboratory work, including an IgE level, were collected and the patient was scheduled for a screening colonoscopy. Findings from the colonoscopy revealed no gross evidence of neoplastic or infectious disease; however, random rectal biopsies were obtained. 

Laboratory Identification

Image 1. Rectal biopsy showing unremarkable colonic mucosa with many calcified structures deep in the epithelium (H&E, 40x).
Image 2. Rectal granuloma surrounding a calcified structure (H&E, 400x).
Image 3. Intact parasitic egg with a small, inconspicuous spine measuring approximately 90 um in greatest dimension (H&E, 1000x oil immersion).

Discussion

Schistosoma japonicum is a trematode that can infect humans through direct penetration of the skin by the cercariae when wading or swimming in infected waters in the Far East, such as China, the Philippines, Indonesia, and Thailand. Infection can initially present as swimmer’s itch and then develop into Katyama syndrome, which includes fever, eosinophilia, muscle aches, lymphadenopathy, abdominal pain, and diarrhea.

S. japonicum migrates through tissues and the adult male & female forms take up residence in the mesenteric veins that drain the small intestine. The female lays eggs which travel to the lumen of the intestines and can be shed in the stool. The host immune response to the eggs is the major cause of clinical disease which presents as inflammation & ulceration in the intestines, portal fibrosis in the liver & splenomegaly, and more rarely, lesions in the central nervous system. As with all trematodes, snails serve as the intermediate host. 

In the microbiology laboratory, diagnosis is usually made by identification of the eggs in stool specimens. The eggs of S. japonicum are ovoid in shape with a transparent shell and a small, inconspicuous spine. The eggs typically measure between 70-100 um in greatest dimension. These eggs can commonly be visualized in rectal biopsies as well. It is important to get an accurate measurement of the size of the egg and multiple sections to be able to detect the location and morphology of the spine. The eggs of S. japonicum must be distinguished from those of S. mekongi which is similar in appearance; however, the latter is found along the Mekong River in Southeast Asia and is smaller in size (50-70 um in greatest dimension). Serology is also a viable diagnostic test in those that have traveled to endemic regions, but sensitivity and specificity of the assays vary depending on how the antigen is prepared and the Schistosoma species of interest.

Treatment of choices for those infected with S. japonicum is praziquantel divided into three doses over the course of one day and it should be administered at least 6 to 8 weeks after the last exposure to contaminated freshwater. Since our patient admitted to a recent visit to the Philippines with potential exposure to infected waters, she received another course of praziquantel therapy.

-Anas Berneih, MD, is a fourth year Anatomic and Clinical Pathology chief resident at the University of Mississippi Medical Center. 

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the Director of Clinical Pathology as well as the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement, and resident education.

Hematology Case Study: A 51 Year Old Woman with Fever and Chills

A 51 year old patient presented to the emergency room with abdominal pain and fever. Fever was associated with diaphoresis, chills and headaches. Patient was in Tanzania for 3 months. She was admitted to the hospital while she was there for some unknown infection, details of which are not available.

CBC done revealed normocytic normochromic anemia with a hemoglobin of 9.2 g/dl and thrombocytopenia. Platelet count was 100 K/uL. On review of peripheral blood revealed presence of malarial parasite (ring forms).

mal1.PNG

mal2

Malaria is an infectious disease caused by Plasmodium parasites. These parasites are primarily spread by the bite of infected female Anopheles mosquitos. There are four main types of Plasmodium (P) species that infect humans:

  • Plasmodium vivax and Plasmodium ovale, which cause a relapsing form of the disease, and
  • Plasmodium malariae and Plasmodium falciparum, which do not cause relapses.

mal3

Malaria must be recognized promptly in order to treat the patient in time.

Microscopy (morphologic analysis) continues to be the “gold standard” for malaria diagnosis. Parasites may be visualized on both thick and thin blood smears stained with Giemsa, Wright, or Wright-Giemsa stains. Giemsa is the preferred stain, as it allows for detection of certain morphologic features (e.g. Schüffner’s dots, Maurer’s clefts, etc.) that may not be seen with the other two. Ideally, the thick smears are used to detect the presence of parasites while the thin smears are used for species-level identification. Quantification may be done on both thick and thin smears.

Various antigen kits are available to detect antigens derived from malarial parasites. These rapid diagnostic tests (RDT) offer a useful alternative to microscopy in situations where reliable microscopic diagnosis is not available.

Vajpayee,Neerja2014_small

-Neerja Vajpayee, MD, is the director of Clinical Pathology at Oneida Health Center in Oneida, New York and is actively involved in signing out surgical pathology and cytology cases in a community setting. Previously, she was on the faculty at SUNY Upstate for several years ( 2002-2016) where she was involved in diagnostic work and medical student/resident teaching.

Microbiology Case Study: A 62 Year Old Male with Epigastric Pain and Weight Loss

Case History

A 62 year old Caucasian male was referred to the gastroenterology clinic with complaints of epigastric pain, diarrhea and unintentional weight loss over the past couple of weeks. Travel history was significant for a recent mission trip to rural areas of the Philippines. During his time there, he participated in building chicken coops and scuba diving. He reported he mostly ate pork & vegetables but did note he consumed a “runny, undercooked duck egg.” He did not eat any seafood during the trip. About a month after his return, he developed epigastric pain and clinically significant diarrhea, with anywhere from 2-8 bowel movements per day. Testing for blood counts, hepatitis and HIV was performed and stool was collected for culture and ova & parasite exam (O&P). He also underwent a colonoscopy with multiple biopsies.

trictric1
Image 1. During colonoscopy, the mucosa of the cecum was erythematous with small areas of ulceration and multiple helminths were noted.

trictric2
Image 2. Histologic section of an adult helminth showed a thick cuticle with annulations, thin hypodermis and a layer of somatic muscle cells (H&E, 100x).

trictric3.png
Image 3: Histologic section of a female helminth with numerous barrel shaped eggs identified (H&E, 400x).

Laboratory Identification

CBC revealed a white blood cell count of 17.9 TH/cm2 with 63.5% eosinophils. Acute hepatitis panel and HIV screen were negative as were two sets of stool cultures and O&Ps. Colonoscopy showed multiple helminths at the ileo-cecal junction (Image 1) and histology of the worms revealed architecture and eggs consistent with Trichuris trichiura (Images 2 & 3).

Discussion

Trichuris trichiura is classified as a nematode (roundworm) and is the third most common round worm causing disease in humans. It has a worldwide distribution and infections are most frequent in areas with tropical climates and resource poor settings with inadequate sanitation practices, especially among children. It is estimated that 800 million people are infected worldwide. While most cases diagnosed in the United States occur in immigrants, travelers and military personnel, T. trichiura has also been documented in the southern United States. Clinical presentations are most frequently asymptomatic or mild. Heavy infections, especially in small children, can cause gastrointestinal problems (abdominal pain, diarrhea, rectal prolapse) and possibly growth retardation due to prolonged malnutrition and anemia.

Infection occurs when embryonated eggs are orally ingested with soil contaminated food & water or due to poor hygiene practices. T. trichiura larvae are released in the small intestine and then travel to the colon where they develop into adult forms. Females begin to produce large volumes of eggs (up to 20,000 per day) about 2-3 months after initial infection. Unembryonated eggs are passed in the stool and in warm, moist soil conditions become infective in 15-30 days.

In the laboratory, diagnosis of T. trichiura is most commonly made by identification of the barrel shaped egg with mucous plugs at either end. The eggs have a double shell and are approximately 50-55 um in length. For increased sensitivity, it is recommended that multiple stool specimens for O&P be collected over the course of 7-10 days as shedding is sporadic. Occasionally, adult worms are visualized on colonoscopy and have a long, thin anterior end which attaches to the mucosa and a thicker posterior portion giving the worm a “whip” like appearance. Adult worms typically measure between 3 to 5 cm in length.

Whipworm infections are routinely treated with albendazole or mebendazole. In the case of our patient, he received multiple doses of albendazole and responded well with resolution of symptoms.

 

JK

-Joy King, MD, is a fourth year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center. 

Stempak

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. Currently, she oversees testing performed in both the Chemistry and Microbiology Laboratories.  Her interests include infectious disease histology, process and quality improvement and resident education. 

 

Microbiology Case Study: A 19 Year Old Male with Fever and Chills

Case History

A 19 year old African American male presented to the emergency department (ED) with complaints of fevers, chills, nausea, vomiting, a “head-splitting” headache and abdominal pain. He reported that his fevers and chills had increased in severity, reaching a max of 104°F, and had 7-8 episodes of non-bloody emesis on the day of presentation. Travel history was significant for a recent return from a two year visit to his home country of Ghana. He did state he was bitten by mosquitos there about a week before his symptoms began. In the ED, vital signs showed a fever of 102.6°F, increased respirations (36 per minute) and a normal pulse and blood pressure (98 beats per minute and 120/65, respectively). Initial CBC showed a hemoglobin of 13.2 g/dL and a hematocrit of 37.3%. Platelet count was decreased (31,000 TH/cm2). A malaria screen was ordered to look for the presence of blood parasites.

Laboratory Identification

plasfal1
Image 1. The rapid detection test for malaria antigens showed a strong positive band for Plasmodium falciparum (T1) and a weak positive band for common malarial antigens (T2).   

plasfal2
Image 2. Giemsa blood smear revealed multiple intracellular trophozoites (ring forms) (100x oil immersion).

The BinaxNOW rapid malaria screening test was positive for both P. falciparum and common malarial antigens, making a possible mixed infection unable to be ruled out (Image 1). The thin blood smear revealed numerous trophozoites with multiple ring forms in one red blood cell and appliqué forms, findings characteristic of P. falciparum (Image 2). No advanced forms, including schizonts and gametocytes, were identified. The high level of parasitemia (approximately 5.5%) also supported the diagnosis of P. falciparum.

Discussion

Malaria is a disease infecting humans through the bite of the female Anopheles mosquito and affects many worldwide, particularly in the tropic and subtropic regions of Africa and Southeast Asia. According to the Centers for Disease Control and Prevention (CDC), an estimated 212 million cases of malaria occurred in 2015 with 429,000 deaths attributed to malaria. In the United States, the majority of cases are diagnosed in travelers and immigrants returning from endemic areas. Rapid diagnosis of malaria, especially in the most aggressive Plasmodium falciparum species, is of utmost importance in order to provide prompt treatment to the patient to minimize morbidity and mortality. Clinical findings can be non-specific, especially early in the disease course, and it is important to ask about travel and exposure history. In the case of P. falciparum, cyclic tertian fevers, chills, headache, nausea, vomiting and muscle aches are common.

Definitive diagnosis is achieved by examination of thick and thin blood smears in the clinical laboratory. These two Giemsa stained smears are prepared in order to recognize the Plasmodium organisms (thick smear) and identify the particular species causing infection (thin smear). This approach remains the gold standard for laboratory confirmation of malaria. In the case of P. falciparum, the most common microscopic findings include visualizing early intracellular trophozoites (two chromatin dots connected by a thin cytoplasm). Multiple rings in a single red cell and appliqué forms (trophozoites at the edge of the red cell) are common as well. The crescent shaped gametocyte is also a diagnostic form of P. falciparum, with schizonts being rare in peripheral blood smears.

Immunochromatographic testing is gaining popularity due to their ability to rapidly (10-15 minutes) detect malaria antigens. This makes them a useful alternative to microscopy where resources do not allow for adequate microscopic examination or trained staff is unavailable around the clock. Although these tests are useful in some clinical settings, cost, accuracy and overall performance need to be considered prior to implementation.

Following identification, another important aspect of the laboratory diagnosis is determining the level of parasitemia, as this aids in the classification of disease severity and how anti-malarial drugs should be administered and in what setting. This determined by the following equation using the thin smear: (number of infected RBCs/total number of RBCs) x 100. At least 500 RBCs should be counted, but in the case of lower levels of parasitemia upwards of 2,000 cells is recommended for the most accurate percentage. Other important points include that gametocytes should not be included in the count and red cells infected with more than one trophozoite should be counted as one infected cell.

In the case of our patient, his parasitemia level of approximately 5.5% classified him as a severe malaria infection and he was transferred to the intensive care unit for close monitoring and treatment with IV quinidine, as this drug is associated with hypoglycemia and QT prolongation. After 24 hours, his parasitemia level was 2.6% but due to significant prolongation of the QT interval on EKG from 407 ms to 560 ms, he was switched to oral atovaquone-proguanil (malarone) after consultation with experts at the CDC.  Parasitemia level was 0.4% after an additional 24 hours. The patient was discharged home after completion of therapy and was well at follow up outpatient visit.

ET

-Eric Tillotson, MD, is a second year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center.

Stempak

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the director of the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement and resident education.