Microbiology Case Study: A 14 Year Old Immunocompromised Male with Pneumonia

Case History

A 14 year old male with a history of selective IgG deficiency, asthma, and GE reflux s/p Nissen Fundoplication, presented to the pediatric pulmonary clinic with 2 weeks of cold like symptoms that progressed to a wet sounding cough productive of sputum and chest pain. 5 days prior he had seen his primary care physician who diagnosed him with pneumonia and started him on amoxicillin and 5 days of prednisone (60mg daily). He is using his albuterol nebulizer every 3 hours, and feels as though his asthma may be contributing to his symptoms but is not the main cause as he has not had a wet cough and chest heaviness and pain with previous asthma attacks. He has had low grade fevers for the past several days but denies chills, sweats, or hemoptysis.  Of note his immune deficiency is treated with IVIG and long term Bactrim which was recently stopped. Pediatric pulmonology elected not to restart the Bactrim but changed his antibiotic to Augmentin. The patient continued to have chest pain and coughing, so the decision was made to proceed with bronchoscopy

Laboratory Identification

zygo-1
Image 1. Scotch tape prep showing broad hyphae with rare septation and round sporangia.
zygo-2
Image 2. Colonies with growth at 30° and 37° C showing “fluffy” growth with darkening in the center of the colony.

Cultures from the BAL revealed a rapidly growing fungi with broad hyphae (5 to 15 micron diameter) that are irregularly branched, and have rare septations. These features, paired with the morphology of the sporangia are diagnostic for a Zycomycete; further identification was attempted however, rhizoids characteristic of Rhizopus, and branching characteristic of Mucor were not identified in this culture.

Discussion

Zygomycetes (Mucormycetes) are widely distributed in the environment in soil and vegetation and infection is through inhalation of spores. Typically, the spores are transported by the muco-cilliary escalader to the pharynx, are swallowed, and then are broken down by the GI tract. In immunocompromised patients, the spores can settle in the nasal turbinates and alveoli causing disease (1). The most common sites of infection are rhino-orbital-cerebral and pulmonary and typically occur in immunocompromised hosts and diabetics (2). The Zygomycetes are also known to invade blood vessels making tissue infarction and necrosis one of the hallmarks of the disease (3). These fungi grow rapidly and are often referred to as “lid lifters” when cultured. Because of this rapid growth, infection with Zygomycetes typically progress quickly and cause periorbital edema, proptosis, and blindness. Facial numbness can occur if there is infarction of sensory branches of the fifth cranial nerve. Infection can spread from the ethmoid sinus to the frontal lobe and result in obtundation. If infection spreads from the sphenoid sinuses to the adjacent cavernous sinus, it can result in cranial nerve palsies, thrombosis of the sinus, and involvement of the carotid artery (4). When the spores are inhaled into the lung, pneumonia with infarction and necrosis results. The infection can spread to contiguous structures, such as the mediastinum and heart, or disseminate hematogenously to other organs such as the GI tract, kidney, and brain (5). Infections are treated with a combination of antifungal drugs such as Amphotericin B, and aggressive surgical debridement. In some situations removal of the palate, nasal cartilage, and orbit are necessary for cure. In patients with pneumonia, often lobectomy is needed for cure (5).

The genera most commonly found in human infections are Rhizopus, Mucor, and Rhizomucor. Rhizopus organisms have an enzyme called ketone reductase, which allows them to thrive in high glucose, acidic conditions, such as in individuals with diabetic ketoacidosis. Rhizopus will have root like rhizoids and are typically located near the sporangiophores. The post-mature sporangiophores can undergo “umbrella like” collapse which is characteristic of Rhizopus. Mucor is more likely to have branching and is often identified when all other species are ruled out; they do not produce a rhizoid.
References

  1. Ferguson BJ. Mucormycosis of the nose and paranasal sinuses. Otolaryngology Clinics of North America. 2000;33(2):349.
  2. Kauffman CA, Malani AN. Zygomycosis: an emerging fungal infection with new options for management. Current Infectious Disease Reports. 2007;9(6):435.
  3. Greenberg RN, Scott LJ, Vaughn HH, Ribes JA. Zygomycosis (mucormycosis): emerging clinical importance and new treatments. Current Opinions in Infectious Diseases. 2004;17(6):517.
  4. Yohai RA, Bullock JD, Aziz AA, Markert RJ. Survival factors in rhino-orbital-cerebral mucormycosis. Survey of Ophthalmology. 1994;39(1):3.
  5. Tedder M, Spratt JA, Anstadt MP, Hegde SS, Tedder SD, Lowe JE. Pulmonary mucormycosis: results of medical and surgical therapy. Annals of Thoracic Surgery. 1994;57(4):1044.

 

-Casey Rankins, DO, is a 1st 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 Associate Professor at the University of Vermont.

Microbiology Case Study: A 10 Month Old Female with Fever and Shoulder Pain

Case History

A 10 month old African American female presented to the emergency department with fever (101.9°F) and a two day history of left shoulder pain. Her mother reported guarding and refusal to move the left arm. There was no history of trauma and no other relevant past medical history. On examination, there was tenderness with gentle manipulation of left shoulder but no erythema or swelling were noted. She had full range of motion of elbow, wrist and finger joints with adequate sensation and pulses. Lab work showed a normal white blood cell count and increased ESR (52mm/hr, normal range: 0-20 mm/hr) and CRP (1.5 mg/dL, normal range: <1.00 mg/dL), suggestive of an infectious or inflammatory process. X-ray of the shoulder showed no bony abnormalities. Orthopedic surgery ordered an MRI which revealed a joint effusion concerning for septic arthritis. She underwent an aspiration with irrigation of the glenohumeral joint with drain placement and was subsequently started on clindamycin. The fluid was sent to the microbiology laboratory for Gram stain and bacterial culture. Multiple blood cultures were also collected.

Laboratory Identification

kingking1
Image 1. Two gray colonies grew in the first quadrant of the chocolate agar after 48 hours of incubation at 35°C in 5% CO2.
kingking2.png
Image 2. A sub from the above plate grew as small, grayish white colonies on blood and chocolate agars after 24 hours incubation at 35°C in 5% CO2. There was no growth on the MacConkey agar plate.
kingking3
 Image 3. Gram stain prepared from the chocolate agar plate showed gram negative bacilli in pairs (100x oil immersion).

The initial direct Gram stain from the fluid showed rare white blood cells and no organisms were identified. Two colonies of the organism grew on chocolate agar as small, grayish colonies after 48 hours incubation (Image 1). Upon subculture, the organism failed to grow on MacConkey agar (Image 2). Gram stain identified the isolate as gram negative bacilli, predominantly arranged in pairs (Image 3). The isolate was positive for oxidase and negative for catalase. MALDI-TOF MS identified the isolate as Kingella kingae. All blood cultures were negative.

 Discussion

Kingella kingae is a short, gram-negative bacilli that occur in pairs or short chains and require increased CO2 for optimum growth. K. kingae is the most common species responsible for human infections and is characterized as a fastidious gram negative rod of the HACEK group. K. kingae is a component of the normal flora in the oral cavity, throat, and upper respiratory tract of children and adults.

Bone and joint infections are the most common clinical manifestations of K. kingae infection in children and can present as bacteremia, septic arthritis, osteomyelitis and discitis. Children usually show symptoms including fever, swollen joints and decreased mobility with a recent preceding history of an upper respiratory tract infections or stomatitis with K. kingae gaining access to the bloodstream through damaged mucosa. In adults, those with poor dental hygiene, immunosuppression, or recent chemotherapy with mucositis are at risk for subacute bacterial endocarditis.

In the microbiology laboratory, K. kingae are facultative anaerobic gram negative bacilli that grow well on blood and chocolate agar plates after 48 hours. There is a small but distinct zone of beta-hemolysis on blood agar.  Unlike enteric organisms, K. kingae does not grow on MacConkey agar. Biochemical tests for K. kingae show a negative catalase reaction, positive oxidase positive reaction and they are non-motile. K. kingae is negative for indole and urease reactions. Automated identification instruments and MALDI-TOF mass spectrometry are able to identify K. kingae.

Beta-lactamase testing should be performed on K. kingae isolates as production among members of the HACEK group is well known. If the isolate is beta-lactamase positive, this predicts resistance to ampicillin, penicillin and amoxicillin. In general, K. kingae is susceptible to 3rd generation cephalosporins (and combinations with beta-lactam inhibitors), macrolides, fluoroquinolones and trimethoprim-sulfamethoxazole.

In the case of our patient, pediatric infectious disease was consulted and her antibiotic therapy was changed to IV cefazolin. She was discharged home with PO cephalexin for 3 weeks. On return to clinic, she was healing well with no complications.

 

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-Anu Abraham, MD, is a first 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 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 24 Year Old Male with Painful Pustules

Case History and Laboratory Findings

A 24 year old male presented to an urgent care clinic with the complaint of painful pustules on his scrotum for the past 4-5 days. He claims that he had not had any recent exposure to sexually transmitted diseases (STD) or to new sexual partners. A month prior to presentation, he was seen for STD evaluation and was treated empirically for suspected exposure.  Testing at that time was negative.  The patient was unsure if these pustules were exacerbated by his work, in which he is in tight, hot spaces doing manual labor. His review of systems was otherwise negative. A swab of one of the pustules was sent for gram stain and culture which showed the following:

neissgonopust1.png
Image 1. Gram stain from a swab illustrating small intracellular Gram negative diplococci (100x, oil immersion).
neissgonopust2
Image 2. Chocolate agar showing small to medium, flat, grey-brown, and moist colonies.

MALDI-TOF identified the organism to be Neisseria gonorrhoeae.

Discussion

N. gonorrhoeae is a gram negative diplococci and the second most common cause of sexually transmitted infections in the United States. The diplococci are described as having adjacent flattened sides giving it the appearance of the letter “D”. N. gonorrhoeae is classically described as a fastidious organism, requiring specialized media (Chocolate, modified Thayer-Martin, Martin-Lewis, New York City agar, etc.) and an enhanced CO2 environment in order to grow, though it is also known to grow on blood agar. Colonies are small to medium in size and are described as flat, grey-brown, and moist. Biochemically, N. gonorrhoeae is catalase and oxidase positive, and is a glucose fermenter.

Neisseria gonorrhoeae can infect the epithelium of the urethra, cervix, pharynx, rectum, and conjunctiva. Infection at these sites results in pain, irritation, and purulent discharge. Dissemination to other locations, such as the skin and joints, can also occur. Though dissemination is uncommon, associated symptoms include: skin sores, fever, migratory polyarthritis, tenosynovitis, and pauciarticular septic arthritis.  N. gonorrhoeae infections typically present as acute urethritis with associated discharge.  Infections are symptomatic in 10% of males and upwards of 70% of females, putting females at a higher risk of developing ascending infections, and potentially, pelvic inflammatory disease. Disseminated infections occur much less commonly, happening in 0.5% to 3% of all gonococcal infections. Therapy guidelines recommend treating uncomplicated infections with intramuscular ceftriaxone and oral azithromycin. Treatment of disseminated infections is variable depending on patient symptoms, but can include a combination of ceftriaxone/cefotaxime and azithromycin/doxycycline, with variable route of administration and length of treatment times. Susceptibility testing is limited to testing for beta-lactamase activity, though in cases of suspected resistance, CLSI guidelines are available for further testing.

References

  1. McCormack WM, Stumacher RJ, Johnson K, Donner A. Clinical spectrum of gonococcal infection in women. Lancet 1977; 1:1182.
  2. Workowski KA, Bolan GA, Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep 2015; 64:1.
  3. Centers for Disease Control and Prevention. Sexually Transmitted Disease Surveillance, 2015. Atlanta, GA: US Department of Health and Human Services; October 2016.

 

-Clayton LaValley, 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 Associate Professor at the University of Vermont.

Microbiology Case Study: A 56 Year Old Man with Bacteremia

Case History

A 56 year old man with a history of hypertension, asthma and COPD, bladder stones, congenital bladder abnormality, and bladder exstrophy presented to the ED with fatigue, generalized weakness, poor appetite, fever, and nausea. He had intermittent right flank pain and generalized abdominal pain. The patient also reported he had passed bladder stones in the past year.

In the ED he had an elevated peripheral white blood cell count of 12.9 x103/μl with a differential of 81% neutrophils, 11% lymphocytes, and 6% monocytes. His creatinine was elevated at 5.4 mg/dl. CT imaging of the urogenital tract showed hydronephrosis with evidence of infection.

Blood and urine specimens were sent for culture. The urine culture grew 10-50,000 cfu/ml Aerococcus urinae. After 30 hours of incubation, the anaerobic blood culture was positive for small, coccoid-looking gram positive rods (Image 1). The following bacteria grew on solid media under anaerobic conditions after 48 hours of incubation (Image 2).

actscha1
Image 1. Gram stain showing small, coccoid-looking Gram-positive rods
actscha2
Image 2. Tiny colonies growing on non-selective anaerobic media after 48 hours.

Discussion

The organism growing in the blood culture was identified as Actinotignum schaalii. A. schaalii is a facultative aerobe that prefers enriched media and grows best in anaerobic or 5% CO2 environments. It is a non-hemolytic, non-motile, and non-spore forming Gram-positive rod. A. schaalii is negative for catalase, oxidase, CAMP factor, and nitrate reduction, but is hippurate positive. It is also negative for lactose, mannitol, raffinose, sorbitol, and trehalose acid production.

Actinotignum schaalii was formerly named Actinobaculum schaalii. The Actinotignum genus now consists of A. urinale, A. sanguinis, and A. schaalii. A. schaalii is part of urogenital microbiota in healthy adults and can cause urinary tract infections, especially as it thrives in the humid atmosphere of diapered children or elderly adults. Isolation of this organism is associated with urinary incontinence, bladder cancer, catherization, neurogenic bladder, renal failure, prostate cancer, and chronic renal failure. The presence of A. schaalii in the urogenital tract can progress to bacteremia and rarely it can also cause groin abscesses.

Actinotignum schaalii is an under recognized uropathogen due to its fastidious nature—it is slowly growing and prefers enriched media grown under anaerobic conditions. None of these conditions are met as part of a routine urine culture as urine cultures are often finaled in < 48 hours, they may not use enriched media, and they are incubated under aerobic rather than anaerobic conditions. Because of these factors, A. schaalii rarely grows in urine culture despite it being a known colonizer of the urogenital tract and occasional uropathogen. Instead it is most commonly recovered from blood cultures as a result of urosepsis. When colonies do grow from blood culture, they are very difficult to identify by biochemical methods. A. schaalii is often misidentified by biochemical panels as Arcanobacterium spp. or Gardnerella vaginalis (API Coryne system, bioMerieux), Actinomyces meyeri (Rapid ID32A system, bioMerieux), or Actinomyces israelii (Rapid ANA II system, Remel). In our lab Bruker Biotyper MALDI-TOF MS was able to identify A. schaalii with high confidence. Based on the most current literature, Vitek MS misidentifies A. schaalii as G. vaginalis or A. meyeri. This data is from 2015, so it’s possible the Vitek MS spectra database has been updated and now identifies A. schaalii.

A. schaalii is routinely susceptible to all β-lactams but requires an extended duration of antimicrobial treatment compared to other uropathogens. It is resistant to trimethoprim/sulfamethoxazole and quinolones, both of which are commonly prescribed for urinary tract infection. Therefore, patients with A. schaalii are at risk for recurrent urinary tract infections due to inappropriate or inadequate antibiotic treatment.

Our patient was prescribed ciprofloxacin for presumed urinary tract infection prior to his bacteremia. He was switched to ceftriaxone upon hospital admission. His bacteremia was cleared and the patient was discharged 5 days later on an oral β-lactam antibiotic. 

References

  1. Lotte, R., L. Lotte, and R. Ruimy. “Actinotignum schaalii (formerly Actinobaculum schaalii): a newly recognized pathogen—review of the literature.” Clinical Microbiology and Infection1 (2016): 28-36. Le
  2. Le Brun, Cécile, et al. “Urinary tract infection caused by Actinobaculum schaalii: a urosepsis pathogen that should not be underestimated.” JMM Case Reports2 (2015).
  3. Manual of Clinical Microbiology, 11th edition

 

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

Microbiology Case Study: A 62 Year Old Male with Productive Cough

Case History

62 year old male from Louisiana with a medical history of COPD presents with fever, productive cough, weight loss, and a red nodule on the left hand. Chest x-ray shows interstitial and lobar infiltrates. Patient reports no recent travel history. Mycobacterial culture of the sputum is positive for an organism. MALDI-ToF of the sputum culture confirms the result.

Lab Identification

mycokans1
Image 1. Kinyoun stained long bacilli with a banded, ladder like pattern isolated from sputum culture.
mycokans2
Image 2. Bright lemon yellow colonies growing on LJ slant after exposure to light on the right compared with unpigmented control colonies on the left.
mycokans3
Image 3. Bright yellow colonies growing on 7H11 media after exposure to light on the right compared with unpigmented control colonies on the left.

Mycobacterium kansasii grows on 7H11 media and Lowenstein-Jensen (LJ) slants. The colonies appear smooth or rough and unpigmented when isolated in the dark. Upon exposure to light, colonies turn bright lemon yellow due to enhanced b-carotene production, which makes M. kansasii a photochromogen. M. kansasii stains positive with acid-fast stains. On Kinyoun stain, it shows long bacilli with a banded, ladder like pattern. M. kansasii is positive for nitrate reduction, catalase, urease, and tween hydrolysis. It is negative for niacin and pyrazinamindase. The identification of M. kansasii is confirmed by MALDI or DNA probe of an isolate.

Discussion

Mycobacterium kansasii is a slow growing photochromogen, an organism that grows unpigmented colonies in the dark but produces a bright lemon yellow pigment upon exposed to light3. It is also an acid-fast positive long bacillus that causes TB-like chronic pneumonia, which is the second most common non-TB mycobacterial infection after MAC in the AIDS population. There are five genotypes of Mycobacterium kansasii. Genotypes I and II infect humans, with I being the most prevalent. Because environmental sources of M. kansasii are rarely identified, isolation of M. kansasii from a culture is never considered a contaminant.

M. kansasii is usually found in the tap water in cities endemic for the infection. In the U.S., it is most prevalent in the central and southern states including Louisiana, Illinois, Texas, and Florida1. Internationally, it is most prevalent in Israel, Korea, France, Japan, Portugal, with the highest incidence in England, Wales, and among South American gold miners.

The majority of patients with M. kansasii infection have an underlying pulmonary disease such as COPD, bronchiectasis, or TB infection3. The clinical manifestation of M. kansasii infection includes a primarily unilateral cavitary infiltrate in the lungs without pleural effusions. Patients are generally older compared with those infected with TB. They present with productive cough, weight loss, fever, night sweats, and dyspnea. Symptoms are usually less severe but more chronic compared with those of TB pneumonia. M. kansasii can also present as cutaneous lesions similar to sporothrichosis. Lesions include nodules, pustules, red plaques, and ulcers1.

M. kansasii infection is diagnosed by chest X-ray or chest CT, positive respiratory culture, and clinical exclusion of other diagnoses2. The criteria for a positive culture include either two consecutive positive sputum cultures, one positive culture from bronchoscopy specimens, or one positive culture with compatible clinical symptoms2. The treatment of M. kansasii infection depends on the resistance of the organism to rifampin. Rifampin-sensitive organisms are treated with at least three drugs including rifampin, ethambutol, isoniazid, and pyridoxine1. Rifampin-resistant organisms are treated with three drugs including clarithromycin or azithromycin, moxifloxacin, ethambutol, sulfamethoxazole, or streptomycin1. Due to drug interaction, rifampin is contra-indicated among HIV patients taking protease inhibitors and nonnucleoside reverse transcriptase inhibitors. Because rifampin increases the metabolism of these HIV medications, it can lead to HIV drug resistance among these patients.

 

References

  1. Akram SM, Bhimji SS. Mycobacterium Kansasii. StatPearls. 2018. https://www.ncbi.nlm.nih.gov/books/NBK430906/
  2. Johnston JC, Chiang L, Elwood K. Mycobacterium Microbiol Spectrum. 2017;5(1):TNMI7-0011-2016. doi:10.1128/microbiolspec.TNMI7-0011-2016.
  3. Meraz A, Raheem S. Pulmonary Mycobacterium Kansasii Infection –A Tale of a Right Upper Lobe Cavitary Lesion [abstract]. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/pulmonary-mycobacterium-kansasii-infection-a-tale-of-a-right-upper-lobe-cavitary-lesion/. Accessed March 12, 2018.

 

-Ting Chen, MD is a 1st 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 Associate Professor at the University of Vermont.

Microbiology Case Study: A 50 Year Old Man with Altered Mental Status

Case Histor

A 50 year old man presented to the emergency room with altered mental status, fever, and hypotension. His medical history was significant for quadriplegia, chronic indwelling urinary catheter with frequent urinary tract infections, and diabetes mellitus. The patient was intubated and started on vasopressors for presumed septic shock. CT scan of the abdomen showed dilated loops of bowel with possible ileus and pneumoperitoneum around the sigmoid colon.

Laboratory Identification

  • Clostridium difficile Fecal PCR: Negative
  • Fecal Bacterial Pathogen PCR: Negative for Salmonella spp., Shigella or Enteroinvasive E. coli spp., Campylobacter spp., or Shiga toxin producing genes
  • Urine culture: 2 strains of Pseudomonas aeruginosa and Klebsiella pneumoniae

Blood culture: At 41 hours, two of four blood culture bottles became positive (one aerobic bottle in each set). Gram stain showed budding yeast with pseudohyphae (Image 1). Growth of white, smooth colonies with foot-like projections was observed on agar (Image 2). MALDI-TOF analysis confirmed identification of the organism as Candida albicans.

candalbi1
Image 1: Gram stain of blood culture bottle demonstrating yeast form (left) and pseudohyphae (right).
candalbi2
Image 2: Colony morphology on chocolate agar demonstrating smooth white colonies with surrounding “feet.”

Discussion

Candida spp. are the most common yeast cultured from clinical specimens. Candida albicans is characterized macroscopically by growth of smooth, white colonies with surrounding “feet” which represent projections of pseudohyphae. The pseudohyphae are distinguished microscopically from true hyphae by constriction of the cells where they meet (with true hyphae, the cell walls will remain parallel). When incubated at 37 C for 2 hours C. albicans will produce germ tubes (extensions from the yeast cell representing an attempt at forming true hyphae).

Candida spp. are normal flora found in the gastrointestinal tract, mucous membranes, and skin. Invasive candidiasis is typically an opportunistic infection with the patient’s own, endogenous flora (although nosocomial spread also occurs). Although it can be normal skin flora, the growth of Candida spp. from a blood culture should be presumed to be pathogenic; treatment should be initiated, and attempts made to identify the source. Typically, invasive candidiasis arises from one of three sources: 1) colonization and biofilm formation on an indwelling intravenous catheter 2) dissemination from a deep nidus of infection (often urinary tract) or 3) translocation from the gastrointestinal tract. Patients in intensive care, those who are immunocompromised, at extremes of age, those who have been on broad spectrum antibiotics, and those with GI tract perforation or anastamotic leaks post-operatively are at greatest risk for developing invasive candidiasis.

C. albicans has historically been the most common species of yeast causing invasive disease. However, non-albicans species (C. glabrata, C. parapsilosis, C. tropicalis and C. krusei) now cause almost 50% of invasive candidiasis. This changing epidemiology is relevant because the different species demonstrate different susceptibility profiles to antifungal agents, including azoles and echinocandins. C. auris is another recently emerging species that shows resistance to multiple antifungal agents, and has been described as causing outbreaks of healthcare-associated infections.

Although the patient’s chronic indwelling urinary catheter raised suspicion for a urinary source of the candidemia, the urine culture failed to support that theory. Given the findings of the CT abdomen in this patient, translocation from the GI tract is favored as the source of the candidemia. The patient’s history of treatment with antibiotics for repeated urinary tract infections, however, may have placed him at greater risk for developing invasive candidiasis.

-Alison Krywanczyk, MD is a 4th 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 Associate Professor at the University of Vermont.

 

Microbiology Case Study: A 49 Year Old with HIV and CNS Lymphoma

Case History 

A 49 year old African American female was transferred from an outside hospital due to orbital cellulitis. Her past medical history was significant for HIV, CNS lymphoma, for which she was taking methotrexate & rituximab, and type II diabetes. Her vitals were: blood pressure 181/145, heart rate 145, temperature 98.6°F and respiratory rate 20. On physical examination, her right eye was bulging, with conjunctiva & eyelid swelling, and her iris was non-reactive. Scant serous drainage was noted. Admission labs showed a normal white blood cell count (9.8 TH/cm2), glucose of 211 mg/dL (normal: 74-106 mg/dL), hemoglobin A1C of 7.7% (normal: 4.2-6.0%) and platelets were low at 41,000 TH/cm2. An infection was suspected and the patient was started on vancomycin and piperacillin-tazobactam. She had a head CT scan which showed right periorbital cellulitis and diffuse sinus disease but no abscess formation. Nasal endoscopy was performed and extensive adhesions & black colored, necrotic tissue of the right nasal cavity was noted in addition to whitish debris, consistent with fungal overgrowth extending into the nasopharynx. Biopsies were taken for frozen section and bacterial & fungal culture and Infectious Disease was consulted for management of a probable rhinocerebral fungal infection.

Laboratory Identification

rhiz1
Image 1. Biopsy of the right nasal wall showed tissue invasion and necrosis with broad, ribbon like hyphae that were pauciseptate and branched at right angles (H&E, 40x).
rhiz2
Image 2. Fluffy, white fungal growth on Sabouraud Dextrose and Sabouraud Dextrose with Chloramphenicol agars at 72 hours of incubation at 25°C. There was no growth on the Mycobiotic agar slant.
rhiz3
Image 3. Tape prep showed a round sporangium containing small sporgangiospores located directly below the rhizoids of the mold which is consistent with the diagnosis of Rhizopus spp. (lactophenol cotton blue, 40x).

Discussion 

Rhizopus spp. belong to the order Mucorales, are ubiquitous in the environment and are the most common etiologic agents of mucormycosis. Rhizopus spp. typically cause invasive infections in the nasal sinus, brain, eye and lung, particularly in patients that have uncontrolled diabetes, HIV or are immunosuppressed. Mucorales are angioinvasive, exhibit perineural invasion and there is usually thrombosis, infraction and necrosis of surrounding tissue. As the illness can progress quite rapidly, prompt diagnosis and treatment is necessary.

If a Mucorales is suspected, tissue specimens obtained during a surgical procedure should be sent for frozen section, direct examination with calcofluor white/KOH and fungal culture. On histologic exam or microscopic exam in the microbiology laboratory, the hyphae of Rhizopus spp. are wide & ribbion-like with few to no septations (pauci- or aseptate) and wide angle branching (90°) (Image 1). Further classification requires culture.

If a Mucorales is suspected, the tissue submitted for fungal culture should be minced into small pieces and directly applied to the appropriate fungal media. Grinding of tissue will kill the hyphae and result in no growth from culture. Mucorales will not grow on media containing cycloheximide. Rhizopus spp. grow rapidly within 1-4 days and start as white, fluffy colonies that become grey or brown in color as they mature (Image 2). The Mucorales are described as “lid lifters” due to their rapid growth and “cotton candy” like colonies that fill the plate. On lactophenol cotton blue prep, Rhizopus spp. have unbranching sporangiophores that terminate in a round sporangium and arise directly under well-developed rhizoids (Image 3). The sporangium ruptures when mature and releases many oval sporangiospores.

Treatment of patients with mucormycosis is usually a dual approach with wide surgical excision and amphotericin B, which has been shown to be an effective anti-fungal drug in the majority of Mucorales. In contrast, voriconazole has poor activity against these isolates. If susceptibility testing is needed, CLSI provides reference broth microdilution guidelines. In the case of our patient, due to the grave prognosis of her condition, in addition to her other comorbidities, the family elected for comfort care measures only and board spectrum anti-fungals were not started.

 

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 Clinical Pathology as well as the Microbiology and Serology Laboratories.  Her interests include infectious disease histology, process and quality improvement and resident education.