Chemistry Case Study: Conjugated Bilirubin in Neonatal Jaundice

Case History

Patient was a 1-week-old infant in the level 2 NICU born at 37 weeks. This infant was initially born with indirect hyperbilirubinemia but now also has increasingly elevated level of direct bilirubin (see measurements in table below). Neonatologist requested conjugated and unconjugated bilirubin test due to increasing elevated level of direct bilirubin. Conjugated bilirubin test is not routinely performed in our hospital laboratory and needs to be send out.

Question: What’s the difference between conjugated bilirubin and direct bilirubin? When does conjugated bilirubin need to be assessed?

Ref Range 3/6/18 3/7/18 3/9/18 3/10/18 3/12/18
Bilirubin total, neonatal 1.0-10.5 mg/dL 9.2 8.7 10.8 10.2 8.6
Bilirubin direct, neonatal 0.0 – 0.6 mg/dL 0.5 0.7 1.8 1.8 2.1


Neonatal jaundice is commonly seen in newborns in the first few days of life, mainly due to increased bilirubin formation from break down of red blood cells and limited conjugation of bilirubin. Total bilirubin normally peaks at day 2-3 and should decline by day 4-5. Sample is collected via heelstick in green top tube and protected from light. Measurement of total bilirubin is interpreted based on the Bhutani Nomogram to assess risk of hyperbilirubinemia. Most often, unconjugated bilirubin is elevated in neonatal jaundice owing to hemolytic causes. In cases with prolonged jaundice, conjugated bilirubin needs to be determined to rule out cholestasis.

Conjugated bilirubin refers to bilirubin conjugated with one or two glucuronic acid, and this term “conjugated bilirubin” is often used interchangeably with direct bilirubin. Direct bilirubin refers to bilirubin fractions that can directly react with diazo reagent without the addition of accelerator, such as methanol or ethanol. This fraction usually includes conjugated bilirubin and delta bilirubin. Delta bilirubin is formed by covalent bonding between conjugated bilirubin and albumin, and has a similar half-life as albumin, 21 days. Therefore, direct bilirubin measurement overestimate conjugated bilirubin and in cases with persist or atypical jaundice, clear differentiation between conjugated and direct bilirubin is important. Clinician should know what the laboratory is measuring when interpreting the bilirubin fraction results.

In laboratories, conjugated bilirubin can be assessed by the VITROS BuBc dry slide, which simultaneously measures unconjugated (Bu) and conjugated (Bc) bilirubin by use of a mordant. In the presence of the mordant, the visible spectra of conjugated and unconjugated bilirubin are different, allowing measurement of both species from a single slide. Fractions of bilirubin can also be separated by HPLC, but this is not practical to use in a routine clinical laboratory. In this case, conjugated bilirubin was measured by VITROS BuBc slide test, and result came back elevated at 1.0 mg/dL (ref range: < 0.3 mg/dL).



-Megan Ketcham, MD is a 4th year anatomic and clinical pathology resident at Houston Methodist Hospital. She will be completing both hematopathology and dermatopathology fellowships. Her interests include pathology resident and medical student education and skin lymphomas.


-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.

Microbiology Case Study: A 79 Year Old Male with Rheumatic Heart Disease

Case History

The patient is a 79 y/o male with past medical history of rheumatic heart disease, permanent atrial fibrillation, mechanical aortic and mitral valves (2004), status post single chamber pace maker for bradycardia (2010), and prostate adenocarcinoma treated in 2000. He had new MRI compatible pace maker placed on Oct 19, 2017. During follow-up he was noted to have a hematoma over the incision site. He had a revision done on Nov 3, 2017. At that time, the blood from the incision site was sent for culture. 

Laboratory Identification

Gram stain showed moderate amount of polys with no bacteria seen. The isolate was a gram-negative rod that was identified on the MALDI-ToF as Burkholderia multivorans.


Image 1: Semi-mucoid, yellow-grey colonies on Chocolate agar and on Blood agar plates.


The Burkholderia genus appears as gram-negative medium-sized straight rods, with the exception being B. mallei which is a coccobacillus. The will grow on blood, chocolate, and MacConkey agar. Oxidative-fermentative-base-polymyxin B-bacitracin-lactose (OFPBL) agar can be used to isolate B. cepacia and Ashdown medium can be used to isolate B. pseudomallei. They are non-lactose fermenters on MacConkey, but B. cepacia can turn into a dark pink to red due to oxidation of lactose after 4-7 days.

B. multivorans is a species within the Burkholderia genus, which are normal to plant, soil, and water, but not normally considered common human flora. Formerly of the Pseudomonas genus, B. cepacia, B. mallei, and B. pseudomallei are the most commonly seen as infections in humans. Further, B. cepacia and B. mallei are not typically human pathogens in a healthy human host. Because of the rarity of this genus to infect humans, their pathogenicity is not well known; but, importantly, they are intrinsically resistant to many antibiotics and can thus be associated with hospital acquired infections.

Of this genus, very little literature is present on B. multivorans specifically, and of the literature that does exist, most of it is in relation to cystic fibrosis patients. Taxonomic advances has shown that B. cepacia complex is a cluster of nine closesly related genomic species or genomorvars (1).  B. multivorans represents genomorvar II. Hospital acquired clinical infections from this complex (but perhaps not specifically from this particular genomorvar) has been seen following catheterization, cystoscopy, heart surgery, and with contaminated ventriculoatrial shunt (2). B. multivorans biochemically is oxidase positive, catalase positive, lipase positive, nitrate-reducing, urease positive, resistant to colistin, and can grow at 42C (3, 4).

A recent comparative genomic study showed that B. multivorans is a highly evolutionarily preserved genome with genomic characteristics from the environment and isolated from cystic fibrosis patients to be similar, and that isolates from different continents are also similar (5). Further, a murine model for pulmonary infections showed that B. multivorans could persist in the host by establishing an intracellular presence within macrophages, which could explain the persistence of this pathogen in cystic fibrosis patients (6). Importantly though, due to the conserved and common genomic structure, there rests a possibility for potential vaccination for cystic fibrosis patients against B. multivorans.

The patient was prescribed a single dose of oral Bactrim and then advised to come into the hospital for admission for IV antibiotics. IV ceftazidime was started with pending blood cultures, which are negative at the time of this documentation.


  1. Coenye T. et al. Taxonomy and identification of the Burkholderia cepacia complex. J Clin Microbiol 2001;39:3427-3436.
  2. Pallent LJ. et al. Pseudomonas cepacia as contaminant and infective age. J Hosp Infect 1983;4:9-13.
  3. Henry DA. et al. Phenotypic methods for determining genomovar status of Burkholderia cepacia complex. J Clin Microbiol 2001;39:1073-1078.
  4. Vandamme P. et al. Occurrence of multiple genomovars of Burkholderia cepacia in patients with cystic fibrosis and proposal of Burkholderia multivorans sp. nov. Int J Syst Bacteriol 1997;47:1188-1200.
  5. Peeters C. et al. Comparative genomics of Burkholderia multivorans, a ubiquitous pathogen with a highly conserved genomic structure. PLoS One. 2017, 21; 12 (4): e0176191.
  6. Chu KK. et al. Persistence of Burkholderia multivorans with the Pulmonary Macrophage in the Murine Lung. Infect Immun 2004; 72 (10): 6142-6147.


-Jeff Covington, MD, PhD, is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.


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

Microbiology Case Study: A Middle-Aged Man with Malaise, Shaking, and Chills

Case history

A middle-aged male presented to the hospital emergency room with the complaints of malaise, shaking and chills for the last two days. He denied any runny nose, cough, abdominal pain, nausea, vomiting, headache or known sick contacts. His past medical history was significant for alcohol use disorder. Imaging of the abdomen revealed an ill-defined region of decreased attenuation in the right lobe of the liver measuring 4.8 x 4.7 x 2.2 cm. The Gram stain of the abscess showed 4+ WBCs (PMNs) and 4+ gram negative rods with a very large capsule surrounding them (Image 1).  The organisms grew very mucoid colonies on 5% sheep blood, chocolate, and MacConkey agars (Image 2).  A string test performed on the mucoid bacterial colonies was >5 mm (Image 3).

Image 1. Gram stain of abscess showing 4+ WBCs and 4+ GNR with large capsule.
Image 2. Cultures showed mucoid colonies on the chocolate and MacConkey agars.
Image 3. A string test was performed on the mucoid colonies and was positive (mucoid capsule “string” > 5mm).


The organism was identified as Klebsiella pneumoniae by MALDI-TOF MS.  Based on the mucoid capsule and positive string test, this organism was further identified as hypermucoviscous K. pneumoniae.

Hypermucoviscous K. pneumoniae is a relatively newly recognized hypervirulent variant of K. pneumoniae. It was first described in the Asian Pacific rim and is now increasingly recognized in Western countries. Defining clinical features include serious, life-threatening community-acquired infection in younger healthy hosts, an unusual feature for enteric gram negative bacilli in the non-immunocompromised population. It can cause a variety of diseases including, but not limited to liver abscess, pneumonia, meningitis, osteomyelitis, necrotizing fasciitis and endophthalmitis.

Intestinal colonization, appears to be a critical step leading to infection. It is seen mostly in Asians, raising the issue of a genetic predisposition vs. geospecific strain acquisition.  The increased virulence might be due to the ability to more efficiently acquire iron and perhaps an increase in capsule production, which confers the hypermucoviscous phenotype to the organism. The vehicles for acquisition and subsequent colonization appear to be food and water, person-to-person transmission (e.g., close contacts such as family members or sexual partners) or animal-to-person transmission (e.g., between pets and their owners).

To date, most strains of hypermucoviscous K. pneumoniae have been very susceptible to antimicrobials except ampicillin.  However, in recent literature, propensity for hypermucoviscous Klebsiella pneumoniae to become multi-, extreme or pandrug-resistant, including the acquisition of extended-spectrum β-lactamases (ESBL) and carbapenemases has been reported. Since hypermucoviscous K. pneumoniae strains often cause abscesses, source control is a major aspect of the overall management plan and a need to drain abscesses and closed space infections is essential for optimal outcome.


  1. Alyssa S. Shon, Rajinder P.S. Bajwa and Thomas A. Russo; Hypervirulent (hypermucoviscous) Klebsiella pneumonia: A new and dangerous breed; Virulence 4:2, 107–118; February 15, 2013; 2013 Landes Bioscience
  2. Bonnie C Prokesch, Michael TeKippe, Jiwoong Kim, Prithvi Raj, Erin McElvania TeKippe, David E Greenberg; Primary osteomyelitis caused by hypervirulent Klebsiella pneumonia; The Lancet Infectious Diseases , Volume 16 , Issue 9 , e190 – e195



-Muhammad Ahmad, MD is a 2nd year anatomic and clinical pathology resident at University of Chicago (NorthShore) program based at Evanston Hospital, Evanston, IL. His academic interests include breast pathology and cytopathology.

-Erin McElvania, PhD, D(ABMM), is the Director of Clinical Microbiology NorthShore University Health System in Evanston, Illinois.

Microbiology Case Study: A 28 Year Old Female with Cough.

Case History

A 28 y/o female with a past medical history of chronic eosinophilic pneumonia, chronic persistent asthma, and elevated IgE status post Xolair therapy presented with a cough. She is a former smoker and a former IV drug user. She has been having a productive cough since March and has not improved despite multiple courses of antibiotic therapy. She coughs mostly in the morning and describes her sputum as thick and greenish. She does not have any associated fevers and does not feel that her rescue inhalers help much. She was given a course of doxycycline for 10 days, and sputum was sent for culture.

Laboratory Identification

Image 1: Gram stain showed many polys, moderate mixed gram positive and gram negative organisms. Sputum culture was reported out as mixed gram negatives.
Image 2: Chocolate and blood agar plates of the mixed gram positive and gram negative organisms.

One of the gram negative rods was identified by the MALDI-ToF as Pasteurella multocida.


The genus Pasteurella consists of multiple identified species with the one most commonly seen in the clinical setting as Pasteurella multocida. As a genus, they are typically gram-negative straight bacilli that are nonmotile, oxidase-positive, catalase-positive, nitrate reducing, and ferment glucose. They will grow on blood and on chocolate agars, but importantly will not grow on MacConkey. Their colony morphology on blood agar is generally convex, smooth, and nonhemolytic.

Infections with Pasteurella are classically associated with animal bites, such as from a dog or cat. However, prior cases in the literature have shown that pulmonary infection with Pasteurella can be associated with other chronic pulmonary diseases such as COPD (1). The choice for using doxycycline is supported in the literature and was specifically discussed in a prior case with improvement (2).


  1. Klein NC. et al. Pasteurella multocida pneumonia. Semin Respir Infect 1997; 12 (1): 54-56.
  2. Bhat S. et al. A case of lower respiratory tract infection with canine-associated Pasteurella canis in a patient with chronic obstructive pulmonary disease. J Clin Diagn Res 2015; 9 (8): DD03-DD04.


-Jeff Covington, MD, PhD, is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.


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

Microbiology Case Study: A 59 Year Old Female with Fevers, Weakness, and Altered Mental Status

Case History

A 59 year old African American female presented to the emergency department with fevers, weakness, fatigue and altered mental status. Her past medical history was significant for hypertension, diabetes mellitus (type 2) with end stage renal disease and a recent cerebrovascular accident the month prior. Her surgical history included a mitral valve repair surgery three years ago and a renal transplant two years ago. Current medications included prednisone, mycophenolate and tacrolimus immunosuppressive agents. Physical examination was unremarkable except for a temperature of 101°F and she was oriented to person, place and time. Pertinent labs included a WBC count of 13.2 TH/cm2, microcytic anemia, and a creatinine of 1.51 mg/dL. Due to previous cardiac surgery, a transesophageal echocardiograph (TEE) was performed and showed a large vegetation (1.6 x 1.5 cm) on the mitral valve.  A diagnosis of endocarditis was made and the patient was started on broad-spectrum antibiotics & taken to surgery for a mitral valve replacement. Multiple blood cultures were negative to this point. Portions of the mitral valve were submitted to surgical pathology and the microbiology laboratory for bacterial, fungal and AFB cultures.

Laboratory identification

Surgical pathology received an aggregate of tan-yellow, fibrous tissue fragments (3.1 x 1.5 x 1.1 cm). Histologic assessment showed a confluent mass containing abundant narrow, septate hyphae consistent with a fungal infection (Image 1). No definitive pigment was identified. Grocott’s methenamine silver (GMS) stain also highlighted the narrow hyphae with numerous septations (Image 2). In the microbiology laboratory, a darkly pigmented mold grew after 5 days of incubation on Sabouraud dextrose agar (Image 3). Lactophenol cotton blue prep showed pigmented, curved conidia with 2-3 transverse septations consistent with Curvularia spp (Image 4). All blood cultures were finalized as no growth after 5 days. Fungitell was found to be greater than 500 pg/ml and Aspergillus galactomannan was negative (<0.5).

Image 1. Sections of mitral valve tissue showed a confluent mass of abundant hyphal elements (H&E, 4x).
Image 2. Special stains of the fungal mass highlighted narrow hyphae with numerous septations and acute angle branching (GMS, 4x).
Image 3. A darkly pigmented mold grew of Sabouraud dextrose agar after 5 days of incubation at 25°C.
Image 4. Many pigmented, curved conidia with multiple transverse septations were seen (lactophenol cotton blue prep, low power).


Curvularia spp. belong to a heterogeneous group of dematiaceous or black molds. The presence of pigment in this category of molds is due to melanin in the hyphae. Dematiaceous molds are ubiquitous in nature and can occasionally cause human infections.  These molds have a characteristic dark appearance on fungal media that is often dark gray, brown or black in color. In addition, when the reverse of the plate or slant is examined, the under surface is also pigmented. Based on their growth rate, the dematiaceous fungi are divided into the fast growers, such as Curvularia, Bipolaris and Alternaria spp., which are mature in 5-7 days. The second group is slow growers that take between 7-25 days to fully mature. Examples of slow growers include Phialophora, Exophila/Wangiella, Cladosporium, Fonsecaea and Rhinocladiella spp.

Most commonly, dematiaceous molds infections usually present as phaeophyphomycosis, chromoblastomycosis or mycetomas. These three entities are cutaneous or subcutaneous mycoses that are obtained by traumatic implantation but vary from one another based on clinical features and histologic features of the mold in tissues. They are most frequently cause infection in male agricultural workers in rural areas of tropical or subtropical climates.  These infections are indolent in nature but can lead to significant morbidity over time, as they are difficult to treat effectively.

In addition to the above superficial infections, Curvularia spp. has also be known to cause keratitis, sinusitis and wound infections. In immunosuppressed individuals, disseminated infections with spread to the lungs and brain have been documented. Endocarditis due to Curvularia spp. is quite rare with very few cases previously reported in the literature. On those documented, Curvularia spp. infections tend to have a predilection for prosthetic heart valves or occur after cardiac surgery. Diagnosis of infective endocarditis is difficult as symptoms are indolent and blood cultures do not have a high yield. Therefore, culture of the vegetation may be the only way to make a diagnosis.

In the microbiology laboratory, Curvularia spp. will grow on routine fungal media as a darkly pigmented mold in a relatively short time. On lactophenol cotton blue prep, Curvularia spp. produce large conidia that usually contain 4 cells that are divided by transverse septations. The conidia take on a curved appearance due to swelling of the subterminal cell, which is often the largest and most deeply pigmented. If identification is necessary beyond the genus level, panfungal PCR assays followed by sequencing of ribosomal genes may be useful in providing a species level diagnosis from fresh or paraffin embedded tissue.

For localized infections, surgical treatment alone may be adequate in some cases.  In infections that are extensive or if there is dissemination, treatment with newer triazoles, such as posaconazole or voriconazole, have shown a broad spectrum of activity against dematiceous molds. Amphotericin B is also another effective option. While susceptibility testing can be performed on clinically significant Curvularia spp. infections, interpretative breakpoints have not been defined and clinical correlation is lacking.

In the case of our patient, she remained on a ventilator following surgery and with the identification of mold on histology, she was started on micafungin. She was switched to amphotericin B after the mold was classified as Curvularia spp. Her condition did not improve despite therapy and she died 3 weeks after surgery.


-Azniv Azar, MD, is a fourth year anatomical 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 the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement, and resident education.

Hematology Case Study: The Race to Save a 48 Year Old Man from a Rare Disease

A 48-year-old Caucasian male presented to a Baltimore Emergency Room complaining of fever, chills, and aches. He stated he had not been feeling well for the past week. His symptoms had progressed rapidly over the last 3 days to include night sweats, nausea and excessive somnolence. History taken in the ER revealed the patient had returned 10 days prior from a Safari in Botswana and Zambia. The patient was admitted to the ICU, in shock, with a BP of 75/50. Even though the patient had taken anti-malarial medication, the doctors suspected malaria. Blood was sent to the lab for a blood parasite exam and treatment for malaria was started while the doctors waited for the confirmation.

In the Hematology laboratory, technologists perform microscopy of thick and thin blood smears to look for malarial parasites. The thin smear is a typical Wright Giemsa stained wedge smear, and the thick smears are prepared and stained so that the red blood cells are lysed, and the sample is concentrated, making examination easier. Thorough, careful examination of the thick smear is aimed to identify whether a particular parasite is present, but they require a long drying period and take several hours to prepare and read. Thin smears can detect the parasites but also permit identification of particular species of malaria. While the thick smears were drying the technologist examined the thin smear.

The technologist who examined this patient’s thin smears saw parasites (image 1) under her microscope. She consulted with a supervisor and pathologist to confirm, and the patient’s doctor was notified that the patient did not have malaria, but instead, had Trypanosoma! This was an exciting find in the laboratory, as there have been only 40 cases seen in the US in the past 50 years.

Image 1. This slide shows the parasite, in dark blue. The parasite causes
African trypanosomiasis, also known as sleeping sickness
(Courtesy of Greater Baltimore Medical Center).

The race for diagnosis and treatment did not stop there, as there are 2 types of African trypanosomiasis, or African sleeping sickness, and effective and appropriate treatment must be started in a timely fashion. Both types look identical on a blood smear and both are considered universally fatal, if not treated. West African trypanosomiasis and East African trypanosomiasis are caused by the tsetse fly, which only lives in rural Africa. The patient stated he did remember being bitten by tsetse flies, and because there had been such a short span of time between being bitten and the onset of symptoms, doctors concluded that the patient had the rarer and fast-acting East African trypanosomiasis, which can kill within months.

Epidemiologists at CDC were contacted, who then consulted other infectious disease specialists at CDC. There are 2 treatments depending the stage of the disease. Surinam is the first line of defense, but melarsoprol, which is arsenic-like and very toxic, must be used if the parasites have reached the central nervous system. Because of the urgent need to start treatment, emergency shipments of both drugs were flown to Baltimore. The patient was started on Surinam to reduce the number of parasites in his blood to a level low enough to allow a spinal tap to be performed. After confirming that the CSF showed no signs of the parasite, treatment with surinam was continued and the patient was discharged a week later and has made a full recovery.

Because of the excellent work done by the medical technologists who made the first discovery, the speed with which the critical calls were made, the actions of the doctors involved, and the cooperation of the CDC, this patient received his first dose of Surinam a little over 24 hours after his blood was sent to the lab. This case shows the importance of a thorough medical and travel history in differential diagnosis. It also illustrates the importance of the competency evaluations and surveys in which all laboratory professionals are required to participate. None of the technologists, doctors or scientists involved had ever actually seen a case of African Trypanosomiasis, they had only read about it in books and seen it on competency assessments.

This case is based on an actual case from 2016. My coworker, Gail Wilson, was the technologist who first saw the Trypanosoma on the slides. Many thanks to Gail for her keen eye and attention to detail!

Image 2: L&R: Trypanosoma brucei in thin blood smears stained with Giemsa. Center: A close up of a tsetse fly. Credit: DPDx



  1. Jon E. Rosenblatt Barth Reller Melvin P. Weinstein.pages 1103-1108, Laboratory Diagnosis of Infections Due to Blood and Tissue Parasites Clinical Infectious Diseases, Volume 49, Issue 7, 1 October 2009; retrieved March 2018 from
  1. Ivo Elliott, Trupti PatelJagrit Shah, and Pradhib Venkatesan. West-African trypanosomiasis in a returned traveller from Ghana: an unusual cause of progressive neurological decline BMJ Case Rep. 2014; 2014: bcr2014204451. Published online 2014 Aug 14.doi: 1136/bcr-2014-204451; retrieved March 2018 from
  1. Lena H. Sun. Medical Detectives raced to save a man from a rare, ‘universally lethal’ disease; retrieved March 2018 from
  1. Parasites – African Trypanosomiasis (also known as Sleeping Sickness). Retrieved March 2018 from
  1. DPDx- Laboratory Identification of parasites of Public Health Concern; retrieved March 2018 from



-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.


Microbiology Case Study: A 52 Year Old Man with End Stage Renal Disease

Case History

A 52-year-old man with multiple medical issues including a history of end stage renal disease on hemodialysis, chronic pancreatitis status post distal pancreatectomy, intravenous drug use through dialysis catheter, and multiple types of bacteremia presented with chills and abdominal pain. Labs on admission included a white blood cell count of 28.64 k/cmm, hemoglobin 8.8 g/dL, and platelets 581 K. He was diagnosed with a pancreatitis flare and admitted for pain management, with further labs drawn. After one day, he felt much better and was discharged with a pending blood culture to follow up on. At 61 hours, one bottle flagged positive with yeast seen on gram stain.

Laboratory findings

Image 1: potato flake agar with creamy tan-white colonies.
Image 2: calcofluor white fluorescent stain showing round yeast forms.

The organism was identified as Cryptococcus laurentii via MALDI-ToF MS. A follow-up fungal culture was negative, however, repeat blood culture grew Stenotrophomonas maltophilia. His tunneled catheter was removed, and two days later the patient required urgent interventional radiology access for dialysis. He completed a two-week course of ceftazidime and was discharged. 


Cryptococcus laurentii is a very rare fungal pathogen. It is a psychrophilic organism, growing ideally at 15 °C, and is the most common yeast found in tundra.1 Major reservoirs include soil, food, and pigeon excrement.2 C. laurentii usually causes infection in immunocompromised hosts, although rare incidents of infection in immunocompetent patients have been reported. Reported manifestations have included fungemia, meningitis, peritonitis, pneumonia, pyelonephritis, keratitis, and skin infection.3

Cryptococcus laurentii is a urease-positive organism. Gram stain shows large budding yeasts without hyphae. The yeast grows on routine agar as whitish-yellow creamy colonies and on birdseed agar as whitish or greenish colonies. Staining with calcofluor highlights encapsulated yeast forms. Molecular diagnosis can be accomplished by ribosomal RNA sequencing of the internal transcribed spacer and D1/D2 regions. Treatment in most cases has been with fluconazole, although in one case of peritoneal dialysis catheter-related peritonitis, voriconazole was used due to low fluconazole susceptibility.4


  1. Molina-Leyva A, Ruiz-Carrascosa JC, Leyva-Garcia A, Husein-Elahmed H. Cutaneous Cryptococcus laurentii infection in an immunocompetent child. International Journal of Infectious Diseases. 2013;17(12). doi:10.1016/j.ijid.2013.04.017.
  2. Johnson, L. B., Bradley, S. F. and Kauffman, C. A. Fungaemia due to Cryptococcus laurentii and a review of non-neoformans cryptococcaemia. Mycoses. 1998;41: 277–280. doi:10.1111/j.1439-0507.1998.tb00338.x
  3. Furman-Kuklińska K, Naumnik B, Myśliwiec M. Fungaemia due to Cryptococcus laurentii as a complication of immunosuppressive therapy – a case report. Advances in Medical Sciences. 2009;54(1). doi:10.2478/v10039-009-0014-7.
  4. Asano M, Mizutani M, Nagahara Y, et al. Successful Treatment of Cryptococcus laurentii Peritonitis in a Patient on Peritoneal Dialysis. Internal Medicine. 2015;54(8):941-944. doi:10.2169/internalmedicine.54.3586.


-Prajesh Adhikari, MD is a 3rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.


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