Microbiology Case Study: An 8 Month Old Female with Vomiting and Diarrhea

Clinical History

An 8-month-old female presented to the pediatric emergency department (ED) due to vomiting and diarrhea for the past 10 days.  Per mother, the baby has had a fever and 6-8 episodes of diarrhea & 2-3 episodes of vomiting each day. On the day of admission, the mother noted the diarrhea was like mucous and contained blood and the baby was unable to tolerate anything by mouth. Past medical history was not significant and sick contacts included a sibling with a recent viral illness. In the ED, the baby had a fever of 103.1°F and was tachycardic. On physical exam, the baby was weak & lethargic with dry mucous membranes and a capillary refill of 2-3 seconds. Mom noted the baby did not produce tears when she cried and had decreased urinary output for the past 24 hours, consistent with dehydration. Initial labs revealed an elevated white count of 20.0 TH/cm2 and a C-reactive protein of 6.60 mg/dL, suggestive of an infectious process. Blood, urine, and stool cultures were sent to the microbiology laboratory and the baby was received IV fluids and ceftriaxone. 

Laboratory Identification

Blood culture signaled positive after 36 hours of incubation on the automated instrument and revealed gram negative rods.

Image 1. Whitish gray colonies on sheep blood and MacConkey agars after 48 hours of incubation at 35°C in ambient air.
Image 2. “Bull’s eye” colonies with a pink center and white outer edge on cefsulodin-Irgasan-novobiocin (CIN) agar after 48 hours of incubation at 22°C in ambient air.

MALDI-TOF mass spectrometry identified the isolate as Yersinia enterocolitica. The urinalysis was positive and the urine culture grew >100,000 CFU/ml of Escherichia coli. Stool culture was negative for Salmonella, Shigella, E. coli O157:H7, Aeromonas, and Plesiomonas. Antigens for Shiga toxin and Campylobacter jejuni were both negative. Stool culture for Y. enterocolitica was not ordered. A multiplex PCR panel for gastrointestinal pathogens also identified Y. enterocolitica

Discussion

Yersinia enterocolitica is a member of the Enterobactericeae family and when transferred via the fecal oral route, can cause gastroenteritis, terminal ileitis, and mesenteric lymphadenitis, particularly in young children, the elderly, and immunocompromised patients, who consume raw or undercooked pork, chitterlings, or drink unpasteurized milk products. Because Y. enterocolitica can survive and multiple at refrigerated temperatures, prepackaged lunchmeats and packed red blood cells can be common sources for infection as well. Rarely, septicemia can result from migration of the organisms into the lymph nodes and then the blood.

Stool, blood, and lymph node cultures are often submitted to the microbiology laboratory for the detection of Y. enterocolitica. The organism is a gram-negative rod that can grow well on routine media such as sheep blood, chocolate, and MacConkey agars at 22°C and 35°C in ambient air. When there is a clinical concern for gastroenteritis caused by Y. enterocolitica, a selective media such as cefsulodin-Irgasan-novobiocin (CIN) agar should be added to the stool culture to enhance isolation. Y. enterocolitica grows as “bull’s eye” colonies with a pink center and surrounding clear to white border on CIN agar.

The organism ferments glucose & sucrose, is positive for catalase & urease, and is oxidase negative. Y. enterocolitica is able to be identified by manual and automated biochemical systems, such as API 20E and Vitek as well as MALDI-TOF mass spectrometry. Culture independent multiplex PCR panels for the diagnosis of gastrointestinal syndromes are gaining popularity due to sensitivity & improved turnaround times; however, reimbursement and the necessity for the isolated organism for susceptibility testing and typing the in the case of outbreak investigations continue to be items of concern.

The majority of cases of Y. enterocolitica gastroenteritis do not require antimicrobial treatment. In the case of severe disease and those that are immunocompromised or with systemic disease should receive treatment with a fluorquinolone or trimethoprim sulfamethoxazole. While Y. enterocolitica produces beta lactamases, it is still uniformly susceptible to extended spectrum cephalosporins as well.    

In the case of our patient, she received 8 days of ceftriaxone and was transitioned to oral trimethoprim sulfamethoxazole and discharged home to finish the 21-day course of antibiotics due to bacteremia from Y. enterocolitica. Mother was counseled to fully cook pork products before feeding to the baby.    

-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 60 Year Old Woman with Endometrial Cancer and Uterine Bleeding

Case History

A female in her 60s with no significant past medical history presented to the emergency department with continued abnormal uterine bleeding for the past two months. She reported never entering menopause. Patient complained of recent unintentional weight loss, shortness of breath, urinary frequency, and new-onset night-time fever and severe fatigue. Physical exam was notable for large uterus and left lower quadrant abdominal tenderness on palpation. Sterile speculum exam revealed a friable tissue extruding from the uterus and malodorous mixture of thin white purulent discharge and blood. Endometrial biopsy, tissue and blood cultures were collected. Labs were notable for normocytic anemia and leukocytosis. Urine analysis was suggestive of urinary tract infection. Pelvic ultrasound showed an enlarged uterus, thickened endometrium with mixed echogenicity. The patient was admitted to the hospital for work up of potential gynecological malignancy and was started on empiric antibiotic therapy for possible urinary tract infection.

The patient’s tissue Gram stain was notable for 2+ WBCs (PMNs) and 4+ gram negative rods. The predominant organism grew on 5% sheep blood and chocolate agars but there was no growth on the MacConkey agar (Image 1).

Image 1. Pasteurella multocida grows on blood (A) and chocolate (B) agar plate.
Image 2. Gross cross section of the friable fungating endometrial lesion. (A) Microscopic pathological findings consistent with undifferentiated carcinoma. (B)

Discussion

The predominant organism was identified by MALDI-TOF MS as Pasteurella multocida. Given the microbiological findings, patient was further questioned but she denied having pet at home or contact with animals. The patient underwent a surgery to remove her uterus, both ovaries and Fallopian tubes. The gross pathological examination of her uterus revealed an exophytic endometrial lesion with extensive area of necrosis surrounding the lesion (Image 2A). Final microscopic pathological diagnosis was significant for a highly malignant and invasive tumor of the uterus (Image 2B) and active infection of her left Fallopian tube.

Here we present a rare case of a P. multocida intrauterine infection lacking history of animal exposure in the context of gynecologic malignancy. P. multocida is a small, non-motile, non-spore forming, aerobic and facultative anaerobic gram negative coccobacillus that is associated with animal exposure. [1] This organism is found in the digestive and respiratory tract of domesticated animals (cats, dogs, cattle, sheep etc.) as well as wild animals (lions, buffaloes, panthers etc.). The suggested hypothesis for transmission of Pasteurella to human involves close contact with the infected animal’s oral cavity. Thus, the most likely route of infection in humans is through direct animal bites or scratch, depositing the bacteria on compromised skin or if an infected animal lick on an exposed human mucosal surface [1, 2]. In the general population, P. multocida causes local infection that may progress to abscess formation, but bacteremia is uncommon. However, elderly patients and those with associated immunosuppressed states from chronic disease or cancer are at higher risk of more complicated severe infections [2].

The presented case highlights the importance of clinical microbiology in the setting of obtaining detailed history and conducting physical examination.  Uncommon cases of P. multocida infection secondary to pet scratches or bite inducing genital infection and causing tubo-ovarian abscess have been reported. Similarly, rare cases of immune-compromised P. multocida bacteremia without history of animal contact have been described. The most likely explanation is the re-activation of previously asymptomatic colonization of the respiratory and gastrointestinal tract in the context of immunosuppression. As such, patients presenting with systemic Pasteurella infection without a documented animal exposure should undergo extensive evaluation in order to exclude the presence of an underlying immunodeficiency [1, 3-4].

References

  1. Weber DJ., Wolfson JS., Swartz MN., Hooper DC. Pasteurella multocida infections – report of 34 cases and review of literature. Medicine. 1984;63(3):133-54.
  2. Raffi F, Barrier J, Baron D, Drugeon HB, Nicolas F, Courtieu AL. Pasteurella multocida bacteremia- report of 13 cases over 12 years and review of the literature. Scand J Infecti Dis. 1987; 19:385-93.
  3. Kimura K., Hagiya H., Yamamoto N., Yoshida H., Akeda Y., Nishi I., Tomono K. Pasteurella multocida multiple intrapelvic abscesses in a young woman with uterine cervical cancer. J Infect Chemother (2018).
  4. Lukban JC., Baker MS. Pasteurella multocida isolation from a tuboovarian abscess. A case report. J Reprod Med 1995;40:603-5.

– Pouya Jamshidi, MD is a 1st year anatomic pathology resident at University of Chicago (NorthShore). Academically, Pouya has a particular interest in neuropathology and cellular basis of neuroplasticity. In his spare time, Pouya enjoys listening to classical music and opera.

-Erin McElvania, PhD, D(ABMM), is the Director of Clinical Microbiology NorthShore University Health System in Evanston, Illinois. Follow Dr. McElvania on twitter @E-McElvania. 

Microbiology Case Study: A 54 Year Old Woman with Fever

Patient History

A 54 year old woman is seen by her oncologist with complaints of rigors and fevers for the past two months. Her past medical history is significant for Stage IV Follicular Lymphoma. Previous treatment included rituximab and bendamustine that was completed a year prior. Currently her therapeutic plan is to receive rituximab maintenance therapy every two months (her most recent dose was 2 days prior to this visit) via a port. She has two dogs, both of which had a diarrheal illness three months prior. She has chickens and spent the summer RV camping around New England. She has not had diarrhea or noticed any rashes. Her travel history includes a trip to Europe  4 years prior. A blood culture was collected due to her fevers and rigors and was found to be positive 29 hours post incubation.

Gram stain of the blood culture bottle showed small, faintly staining gram negative, curved rods (Image 1). The patient was started on ciprofloxacin and referred to the infectious disease clinic. After 3 days of incubation, small slightly mucoid yellow gray colonies grew on 5% sheep blood and chocolate agar (Image 2). There was no growth on the MacConkey agar. Initial Gram stain revealed similar gram negative rods to the Gram stain performed on the blood culture media. MALDI-TOF identified the organism as Campylobacter jejuni. The patient was asked to stop taking ciprofloxacin and start azithromycin. She also had her port removed on this day. Four days after her oncology visit, the patient’s blood was negative for organisms. Her fever and rigors resolved as well. Susceptibility testing showed the organism to be resistant to ciprofloxacin and susceptible to azithromycin.

Image 1. Gram stain from the blood shows faintly staining curved gram negative rods.
Image 2. Growth on chocolate agar after 3 days (Not in a microaerophilic environment).

Discussion

Campylobacter jejuni is a small, gram negative, curved rod. It is the most common cause of bacteria-mediated diarrheal disease globally (1). In immunocompromised patients, it can cause a variety of extraintestinal diseases: septicemia, meningitis, septic arthritis, and endocarditis (2). Infection can also lead to Guillain-Barre syndrome. This is an autoimmune disease of the peripheral nerves that is thought to be due to antigenic cross reactivity between the surface lipopolysaccharides of the bacteria and the patient’s peripheral nerve gangliosides (3). Of patients diagnosed with Guillain-Barre syndrome, 20-40% will have had a history of Campylobacter jejuni infection (2).

Campylobacter jejuni grows best at 42°C in a microaerophilic environment (5% O2,10% CO2, and 80% N2). It displays a darting motility in broth and will not grow in 3.5% NaCl. Almost all are oxidase and catalase positive. On Campy-BA, a selective blood agar plate for Campylobacter jejuni, colonies will be peach colored. This media is made up of a Brucella agar base, sheep red blood cells, and various antibiotics that suppress the growth of normal fecal flora(2).

Macrolides (erythromycin, azithromycin) are considered the treatment of choice, however it has been reported that resistance approaches 1.7% (1 and 2). Fluoroquinolones like ciprofloxacin can be used, however resistance is higher due to widespread use of this drug in medical and veterinarian practices and agricultural businesses.

References

  1. Yang W, Zhang M, Zhou J, Pang L, Wang G, Hou F. The Molecular Mechanisms of Ciprofloxacin Resistance in Clinical Campylobacter jejuni and Their Genotyping Characteristics in Beijing, China. Foodborne Pathog Dis. 2017;14(7):386-392.
  2. Tille P. Bailey & Scott’s Diagnostic Microbiology. Fourteenth Edition. Elsevier;2017.
  3. Murray P. Medical Microbiology. Seventh Edition. Elsevier; 2013.

-Angela Theiss, 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.

Microbiology Case Study: A 14 Year Old Female with 3 Day History of Abdominal Pain

Case History

A 14 year old Caucasian female was transferred to the pediatric emergency department from an outside hospital due to a 3 day history of abdominal pain. The pain was concentrated in the right lower quadrant and was accompanied by nausea and two episodes of vomiting. Her vital signs were normal and physical exam demonstrated tenderness and guarding upon palpation of the right lower quadrant of the abdomen. Her white blood cell count was elevated at 21.1 TH/cm2 and showed 91% neutrophils. Abdominal ultrasound was unremarkable and CT scan was inconclusive for appendicitis. The patient was taken to surgery for an exploratory laparotomy and her appendix was removed.

Laboratory Identification

Image 1. Microscopic review revealed a female nematode with characteristic cephalic inflations, numerous eggs in the uterine cavity, and an intestinal cavity at the posterior end (H&E, 20x).
Image 2. Numerous oval shaped eggs with a thick shell that are slightly flattened on one side were observed (H&E, 200x). The eggs measured 55 x 25 um in dimension.

Gross examination of the appendectomy specimen showed an unremarkable appendix that measured 5.7 cm in length by 0.7 cm in diameter. There was no evidence of perforation. On sectioning, a small, white, “worm-like” structure (0.6 x 0.1 cm) was identified at the tip of the appendix and submitted for histologic examination. Microscopic review identified a female nematode with many eggs characteristic of Enterobius vermicularis. There was no acute inflammatory process identified upon microscopic review of the appendix.

Discussion

Enterobius vermicularis, commonly referred to as pinworm, is a nematode infection that frequently presents as perianal itching in young children or those living in crowded settings, with symptoms most prominent in the evening and night time. Adult female worms reside in the cecum of the large intestine and migrate to the perianal area during the night to lay eggs, resulting in irritation. Often, infections can be asymptomatic as well. E. vermicularis is one of the most common helminthic infections in the United States.  

Humans are the only known host of E. vermicularis and become infected by ingesting embryonated eggs from feces or handling contaminated materials such as clothing, bed linens or from bathroom surfaces. Pinworm has a direct lifecycle and the larvae hatch in the small intestines and develop into adult worms that occupy the colon. It takes about one month from ingestion of infective eggs for E. vermicularis eggs then to be shed on the perianal folds.

Laboratory identification of E. vermicularis is usually made by using a piece of scotch tape or an adhesive paddle applied to the perianal skin in the morning and then visualizing the eggs microscopically. The eggs of pinworm are oval in shape & are flattened on one side with a thick capsule and measure between 50-60 x 20-30 um in size.On occasion, the eggs can be seen on pap smears as well. E. vermicularis worms can sometimes be visualized during colonoscopy, gastrointestinal & pelvic surgeries, and are capable of being identified by histology. Histologic sections of adult E. vermicularis worms usually show prominent lateral alae on the outer surface, testis or ovaries depending on the sex of the worm, and the intestinal tract. In gravid female worms, the characteristic eggs are numerous and can be helpful in the identification. 

Treatment options of an E. vermicularis infection include an initial dose of albendazole, mebendazole,or pyrantel pamoate followed by a second dose two weeks later to prevent possible reinfection. Family members and other close contacts may be treated as well ensure eradication. In the case of our patient, her post-surgical course was uneventful and her white blood cell count trended down to 7.0 TH/cm2 after surgery. She was discharged home the following day. 

-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 31 Year Old Man with History of IV Drug Use

Case History

The patient is a 31 year old man with a history of intravenous drug use with last reported use nine months previous, who reports low back pain. The patient’s symptoms started as a mild pain and progressively worsened over two weeks to the point that he was unable to stand or ambulate. He also developed intermittent radiation of pain to the bilateral lower extremities and associated symptoms of chills and diaphoresis. Blood cultures were sent. MRI showed an epidural abscess at the level of L5-S1. The patient underwent lumbar spinal decompression surgery, and intra-operative cultures were sent for evaluation.

Laboratory Identification

Gram smear of blood cultures showed gram negative bacilli (Image 1). Culture of the abscess specimen and blood cultures showed growth on chocolate, blood, and MacConkey agar; growth on MacConkey plates did not show lactose fermentation (Image 2,3). MALDI-TOF identified this organism as Serratia marcescens.

Image 1. Gram stain of blood culture showing gram negative rods.
Image 2. Blood agar showing large colonies without hemolysis.
Image 3. MacConkey agar showing non lactose fermenting colonies.

Discussion

Serratia marcescens is a motile, facultatively anaerobic, gram negative bacillus of the Enterobacteriaciae family. Some strains of Serratia produce a distinctive brick red pigment, prodigiosin (Image 4), although non pigmented strains are frequently isolated from human infection sites. Serratia marcescens is one of the few Enterobacteriacea that produces DNAse, lipase, and gelatinase. It does not usually ferment lactose. This species is widely present in the environment, including in animals, insects, plants, water, and soil, but unlike other Enterobacteriaciae species it is not a typical component of normal human fecal flora.

Image 4. Colonies of Serratia marcescens producing red pigment. Photo from the CDC Public Health Image Library (https://phil.cdc.gov/Details.aspx?pid=10544).

Eight species of Serratia have been found to cause infections in humans. Of these, >90% are caused by Serratia marcescens (1). This is a rare cause of infection in immunocompetent hosts but can cause opportunistic nosocomial infections, especially following invasive procedures such as such as intravenous catheterization, respiratory intubation, and urinary tract manipulations. The most common infections caused by Serratia marcescens are urinary tract infections, pneumonia,surgical wound infections, eye infections, and bacteremia. Multiple hospital outbreaks of Serratia have been reported, with sources of infection including tap water, soap, blood transfusion products, and injected medications (2). It has also been described as a cause of endocarditis in injection drug users (3).

Serratia is intrinsically resistant to ampicillin, ampicillin-sulbactam, and 1st and 2nd generation cephalosporins due to an inducible, chromosomal AmpC beta-lactamase. Resistance to later-generation cephalosporins may be induced through exposure to these antibiotics, despite not being detected on initial antibiotic susceptibility tests. Thus, susceptibility testing is misleading and thirdgeneration cephalosporins (such as ceftazidime, ceftriaxone, and cefpodoxime) should be avoided for the treatment of Serratia species regardless of in vitro susceptibility.

References

  1. Laupland KB, Parkins MD, Gregson DB, Church DL, Ross T, Pitout JD. Population-based laboratory surveillance for Serratia species isolates in a large Canadian health region. Eur J Clin Microbiol Infect Dis. 2008; 27: 89–95.
  2. Mahlen SD. Serratia infections: from military experiments to current practice. Clin Microbiol Rev. 2011; 24:755.
  3. Mills J., Drew D. Serratia marcescens endocarditis: a regional illness associated with intravenous drug abuse. Ann Intern Med. 1976; 84:29–35.

-Erica Worswick is a pathology student fellow 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 54 Year Old Male with Shortness of Breath

Case History

A 54 year old male presented in the emergency room with worsening of shortness of breath and chest pain. He has a history of a bicuspid aortic valve that was treated with bio-prosthetic aortic valve replacement seventeen years ago and a second aortic valve replacement seven years ago. The patient’s echocardiogram showed severe aorticstenosis and moderate to severe mitral regurgitation. During hospital stay he started to show signs of low cardiac output syndrome and an intra-aortic balloon pump was placed. During sternotomy for aortic valve replacement and mitral valve repair they discovered a severely calcified and stenotic valve with additional debris that could be consistent with endocarditis. Tissue culture was sent.

Gram stain showed pink strings that could be gram negative rods, but could also be tissue debris due to tissue grinding (Image 1). After 3 days of incubation, some colonies grew on 5% sheep blood (Image 2) and chocolate agar plates with no growth on MacConkey selective medium.

Colony Gram stain made from these colonies (Image 3) was compared with the initial gram stain and showed similar type of pleomorphic gram negative rods. MALDI-TOF identified this organism as Cardiobacterium hominis.

Image 1. Tissue Gram stain showing pleomorphic gram negative rods or tissue debris (difficult to say which).
Image 2. Growth of organism after 3 days on 5% sheep blood agar.
Image 3. Colony Gram stain from shows same pleomorphic forms seen on primary tissue Gram stain, which is consistent with Cardiobacterium hominis.

Discussion

Cardiobacterium hominis is a fastidious, pleomorphic, non-motile, gram negative bacillus and member of the HACEK group which comprises Haemophilus species, Aggregatibacter, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae. C. hominis is present as normal flora of the oropharynx in most individuals but it has also been attributed to cause infective endocarditis.

C hominis is a fastidious bacterium that grows best in the presence of increased levels of CO2 and high levels of humidity and often takes several days to grow on solid media (1). It can be distinguished from other HACEK members by a positive oxidase reaction, the production of indole and the absence of catalase activity and nitrate production.

Some of the risk factors leading to C hominis endocarditis include dental work, structural cardiac abnormalities, previous valve replacement, dilated cardiomyopathy and past history of rheumatic heart disease and endocarditis (2). The illness usually follows a sub acute course with symptoms lasting for weeks or months (1). Patients will often report fever, myalgia, anorexia, and weight loss. C. hominis tends to form large, friable vegetations associated with cerebral embolization or mycotic aneurysm formation and this might be responsible for atypical presentation of endocarditis(1). The overall prognosis of endocarditis due to C. hominis is quite favorable, despite the frequent need fo rvalve replacement (3).

Third generation cephalosporin (ceftriaxone) is considered the drug of choice for C. hominis endocarditis. Ampicillin can be used after susceptibility testing. Ampicillin-sulbactam or ciprofloxacin are alternative therapeutic options.

References

  1. Currie, Codispoti, Mankad, et al. Late aortic homograft valve endocarditis caused by Cardiobacterium hominis: a case report and review of the literature. Heart 2000;83:579–581.
  2. Walkty A. Cardiobacterium hominis endocarditis: A case report and review of the literature. The Canadian Journal of Infectious Diseases & Medical Microbiology. 2005;16(5):293-297.
  3. Fazili T, Endy T, Javaid W, Amin M. Cardiobacterium Hominis Endocarditis of Bioprosthetic Pulmonic Valve: Case Report and Review of Literature. J Clin Case Rep. 2013;3:286.

-Kiran Manjee, MD, is a 1st year anatomic and clinical pathology resident at University of Chicago (NorthShore).

-Erin McElvania, PhD, D(ABMM), is the Director of Clinical Microbiology NorthShore University Health System in Evanston, Illinois. Follow Dr. McElvania on twitter @E-McElvania. 

Microbiology Case Study: A 21 Year Old With Chronic Kidney Disease

Case History

The patient is a 21 year old male with a history of developmental delay and chronic kidney disease secondary to posterior urethral valves, status post kidney transplant at age 14, who presents for a routine office visit with his pediatric nephrologist. In the past year, he has had chronic antibody-mediated transplant rejection despite immunosuppression. In addition, he drinks 1-1.5 gallons of water daily, self-catheterizes every three hours, and has an indwelling Foley at night. During the office visit, he denies any urinary symptoms, including dysuria, hematuria, cloudy urine, reduced output, or fever. However, given his significant risk factors for urinary tract infection, his provider orders a urinalysis and urine culture.

Laboratory Identification

The urine was noted to be cloudy, was positive for nitrites and leukocyte esterase, and had 11-50 white blood cells per high-powered field. 

Urine culture demonstrated the growth of two organisms, one of which was identified to be greater than 100,000 CFU of Proteus miribalis, and the second of which grew 10,000-100,000 CFU, was isolated, and is shown below:

Image 1. Appearance of the second organism’s growth on blood agar after the bile solubility test.
Image 2. Gram stain showing gram positive diplococci.

Mass spectrometry by MALDI-TOF confirmed that this second organism is Streptococcus pneumoniae, a bile-soluble gram positive diplococci. 

Discussion

S pneumoniae is implicated in a number of diseases, but it is an uncommon pathogen in the urine. Several case-series and case reports have been published demonstrating a predilection of pathogenic urinary S pneumoniae for pediatric patients with urinary tract abnormalities. In one series, 26 urine cultures from 18 patients were identified as growing S pneumoniae, with CFU counts ranging from 100 to 100,000. Sixteen of the 26 cultures grew only S pneumoniae. Of the 18 patients, only six were adults, eight had had a kidney transplant, and four others had chronic problems with their kidneys (1). In another series of three pediatric cases, one patient had congenital bilateral duplication of the renal collecting system, one had a “congenital imperforate anus (high type 1A) with a rectovesical fistula and grade 4 bilateral vesicoureteral reflux,” and the third had bilateral renal dysplasia (2). Neither case series was able to identify a specific serotype of S pneumoniae responsible for these infections.

As discussed by Choi et al, the altered flow dynamics of the abnormal urinary systems in these patients may be compromising normal host immune clearance mechanisms, thereby increasing the susceptibility to infection (2, 3). However, it is unclear why S pneumoniae infections have a predilection for congenital urinary tract abnormalities, as opposed to all urinary tract abnormalities. Choi et al postulate that some of the gene polymorphisms known to predispose individuals to UTI or pneumococcal infections could be genetically linked to genes responsible for urinary tract abnormalities, thus increasing the probability that an individual with a congenital urinary tract abnormality would have an S pneumoniae urinary tract infection (2,4).

Given the patient’s history and risk factors, the presence of S pneumoniae in his urine was found to be significant. Treatment of both organisms and appropriate follow-up was recommended.

References

  1. Burckhardt, Irene, Jessica Panitz, Mark van der Linden, and Stefan Zimmermann.  “Streptococcus pneumoniae as an agent of urinary tract infections – a laboratory experience from 2010 to 2014 and further characterization of strains.”  Diagnostic Microbiology and Infectious Disease.  2016; 86: 97-101.
  2. Choi, Rihwa, Youngeun Ma, Kyung Sun Park,  Nam Yong Lee, Hee Yeon Cho, and Yae-Jean Kim.  “Streptococcus Pneumoniae as a uropathogen in children with urinary tract abnormalities.”  The Pediatric Infectious Disease Journal.  2013; 32(12): 1386-1388.
  3. Bogaert, D, R de Groot, PWM Hermans.  “Streptococcus pneumoniae colonization: the key to pneumococcal disease.”  The Lancet Infectious Diseases.  2004; 4(3): 144-154.
  4. Yuan, Fang Fang, Katherine Marks, Melanie Wong, Sarah Watson, Ellen de Leon, Peter Bruce McIntyre, John Stephen Sullivan.  “Clinical relevance of TLR2, TLR4, CD14, and Fc gamma RIIA gene polymorphisms in Streptococcus pneumoniae infection.”  Immunology and Cell Biology.  2008; 86(3): 268-270.

-Fritz Eyerer, MD is a first 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.