Microbiology Case Study: A 58 Year Old Female with Fever, Headache, and Vomiting

Case History

A 58 year old female presented to the emergency department with complaints of a fever (reaching 102.9°F) and headache with associated nausea and vomiting for the past 24 hours. Her past medical history was significant for a resection of a recurrent hemangiopericytoma by the neurosurgery service three weeks prior. The patient also noted clear drainage from this surgical site which had begun 5 days ago. Other symptoms noted at presentation included decreased appetite and dehydration. She denied back & neck pain, photophobia or stroke and seizure-like symptoms. Her vital signs were all within normal limits. On physical exam, a healing surgical wound was noted in the posterior auricular area with clear drainage, but no blood or exudates were visualized.  She had no tenderness when her spine was palpated and neurologic exam showed a left sided facial droop and tongue deviation which were noted previously and attributed to her multiple central nervous system surgeries. Complete blood count (CBC) showed a mild increase in white blood cells and anemia. An external ventricular drain was placed and cerebral spinal fluid (CSF) was sent to the microbiology lab for culture. Blood cultures and a swab from the surgical wound were also collected.

Laboratory Identification

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Image 1. Gram stain of the cytospin CSF showed many acute inflammatory cells and numerous Gram negative bacilli (1000x).

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Image 2. Growth of large, glossy, reddish-orange colonies on sheep blood agar (image taken after 72 hours of incubation).

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Image 3. Growth of large, deep red colonies on MacConkey agar (image taken after 72 hours of incubation).

 

Gram stain of the CSF showed numerous acute inflammatory cells and many Gram negative bacilli (Image 1). Culture of the CSF and wound swab showed large, glossy red colonies on sheep blood and MacConkey agars (Images 2 & 3). Analysis of the colony by matrix assisted light desorption ionization time of flight mass spectrometry (MALDI-TOF MS) identified the organism as Serratia marscescens.

Discussion:

Serratia marscescens is a facultative Gram negative bacillus that is a member of the Enterobacteriaceae family. S. marscesens is ubiquitous in the environment and the most frequent and clinically important species in the genus. Although S. marscesens usually doesn’t cause infection in healthy individuals, it is notorious for colonizing and causing infections in hospitalized patients, particularly those who are immunocompromised, in intensive care units (especially intubated patients) and those with indwelling catheters.  While respiratory infection are most common, S. marscesens has also been implicated in numerous other opportunistic infections such as urinary tract infections, wound infections and septicemia. Brain abscesses and meningitis are less common. S. marscesens has been implicated as the cause of outbreaks in hospitals and can often be traced back to pieces of medical equipment including nebulizers, bronchoscopes, laryngoscopes and contaminated solutions. Person to person transmission is also recognized and thought to be predominantly transmitted via direct contact.

In the laboratory, S. marscesens can be identified by its characteristic non-diffusible red pigment, prodigiosin. Care should be taken when interpreting the lactose reaction on MacConkey agar, as the red pigment may be confused with a positive reaction, while S. marscesens is known to be lactose negative.  As a member of the Enterobacteriaceae family, S. marscesens is able to ferment glucose, reduce nitrate to nitrite and has a negative oxidase reaction. A unique feature of this genus is that all Serratia spp. produce three proteolytic enzymes: lipase, gelatinase, and DNase. Commercial systems, including MALDI-TOF MS, are helpful in the identification of S. marscesens as well.

Treatment of Serratia marscescens infections can be difficult due to various antimicrobial resistance mechanisms, such as expression of extended spectrum beta lactamases (ESBLs), AmpC cephalosporinases and carbapenemases, exhibited by the organism. In the case of our patient, she was empirically started on vancomycin and piperacillin-tazobactam and taken to surgery for wound wash out, removal of hardware and repair of CSF leak. Her antibiotics were changed to meropenem and gentamicin. She was discharged to a rehabilitation facility and received meropenem for a total of 6 weeks.

 

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-David Marbury, MD, is a 3rd year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center.

Stempak

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

Microbiology Case Study: A 64 Year Old with Coronary Artery Disease

Case History

The patient is a 64 year old man with a past medical history significant for coronary artery disease, chronic systolic heart failure, poorly controlled type 2 diabetes mellitus, atrial fibrillation, chronic respiratory failure on home oxygen, squamous cell carcinoma of the larynx status post chemotherapy, and radiation and lung adenocarcinoma status post microwave ablation. On the morning of presentation, the patient’s wife was unable to wake him and found him to have low oxygen saturation with a home monitor. Three days prior to presentation, the patient had been evaluated in the emergency department for leg and back pain for which he was prescribed hydromorphone. He had also been experiencing nausea for several days, with fever (101° F) and chills. His wife endorses several sick contacts at home. He has been admitted to the hospital numerous times within the past year for respiratory failure, most recently 6 months ago. The patient also was given a course of antibiotics one month prior for a “cold.”

Enroute to the emergency department, EMS administered naloxone without significant response. Upon arrival to the hospital, his vital signs were: temperature 97.9° F, heart rate 69, respiratory rate 23, blood pressure 104/57, 95% SpO2. He was found to have a white blood cell count of 15,690/cm2 and a chest x-ray showed diffuse patchy airspace opacities concerning for multifocal pneumonia. A viral swab was collected and blood cultures were drawn. He was started on levofloxacin for suspected community acquired pneumonia.

His blood cultures were found to be growing gram negative coccobacilli.

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Figure 1. Gram stain from a positive blood culture illustrating small Gram negative coccobacilli (100x, oil immersion).

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Figure 2. Chocolate agar illustrating the convex, smooth and gray colonies.

MALDI-TOF identified the organism as Pasteurella multocida. Further investigation revealed that the patient recently acquired a puppy (4-month-old) that bit him while playing. Antibiotics were switched to IV ceftriaxone and the patient recovered. He was later discharged on IV antibiotics and home healthcare.

Discussion

Pasteurella multocida is a non-motile gram negative coccobacillus that is oxidase-positive and glucose fermenting. Most isolates don’t on MacConkey agar. It is a known cause of disease amongst humans and animals, but is commonly a commensal organism found in domesticated and wild animals. It is most notably found in the oropharynx of cats, dogs, pigs, and birds. The majority of P. multocida infections are due to animal exposure, either from traumatic inoculation or proximity. Soft tissue infections are most common, resulting from animal bite or scratch. It has also been known to cause pulmonary disease in the form of multifocal pneumonia in those with pre-existing chronic lung disease. It is also a rare cause of septic arthritis, osteomyelitis, endocarditis and meningitis in those with disseminated disease.

P. multocida virulence factors include an endotoxin and an antiphagocytic capsule. It grows well on routine laboratory media but not on MacConkey. Colonies appear convex, smooth, gray and nonhemolytic. Mucoid variants can also occur. It has been described as having a musty or mushroom odor, although sniffing plates is not recommended. Susceptibility testing is usually not required as it is universally susceptible to β-lactams. However, CLSI does provide breakpoints for suggested drugs should the need for testing arise.

References

Tille, P. M., & Forbes, B. A. (2014). Bailey & Scott’s Diagnostic Microbiology (Thirteenth edition.). St. Louis, Missouri: Elsevier.

Kuhnert P; Christensen H, eds. (2008). Pasteurellaceae: Biology, Genomics and Molecular Aspects. Caister Academic Press.

 

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

 

 

Help Researchers Tackle Antimicrobial Resistance in Tuberculosis

Researchers at the University of Oxford are researching antibiotic resistance in Tuberculosis, and they want help reading MIC plates. You don’t have to fly to England, though–you can do it online! Visit the project Bash the Bug on Zooniverse to learn more, view a short tutorial, and get started.

You can read more about the Bash the Bug project here.

 

 

Microbiology Case Study: An 11 Year Old with Abdominal Pain

Case History

An 11 year-old patient with a history of a relapsed lymphoma presented to the hematology/oncology clinic with worsening abdominal pain. The patient was recently started on metronidazole to treat a C. difficile infection. In the clinic, the patient was found to be hypotensive, hypoxemic and pancytopenic. Blood cultures were drawn and the patient was admitted directly to the pediatric ICU and started on empiric antibiotics.

The blood cultures turned positive with Gram-positive cocci, which went on to produce small, gray, alpha-hemolytic colonies on the blood agar plate (Image 1). The colonies were catalase negative and PYR negative. The isolate was analyzed by a Bruker MALDI-TOF mass spectrometer and was identified as Streptococcus lutetiensis (score 2.19). Susceptibility testing revealed the isolate susceptible to ceftriaxone, penicillin, and vancomycin.

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Image 1. 5% sheep blood agar growing small, grey, alpha-hemolytic colonies

 

Discussion

S. lutetiensis is part of the complex of organisms previously identified as the Streptococcus bovis group. This group of organisms, which possess the Lancefield Group D antigen, has undergone considerable reclassification schemes as phenotypes and genotypes have been investigated. The original biochemical classification schemes were based on their ability to ferment mannitol as well as the presence or absence of beta-glucuronidase activity. Early observations of the DNA properties from these organisms, such as %-GC base content and DNA-DNA hybridizations, identified six unique clusters of Group D streptococci [1]. One cluster group (cluster group #4) had heterogeneous biochemical phenotypes. A subcluster of this cluster group #4 was separated from the other members of the cluster based upon esculin hydrolysis. This subcluster would later go on to be named S. infantarius, so named as several isolates originated from the feces of human infants [2].

Further DNA-DNA hybridizations and ribotyping analysis led to the declaration of two S. infantarius subspecies: subsp. infantarius and subsp. coli [3]. The 16S rRNA ribotyping was problematic, however, as several species in this genus are 97-99% sequence identical.

In an attempt to address some of the limitations of relying on the 16S rRNA gene, one group analyzed the features of the conserved gene encoding the manganese-dependent superoxide dismutase gene (sodA). They observed substantial differences between S. infantarius subsp. infantarius and S. infantarius subsp. coli [4]. Thus, for the latter organism, a new species of streptococci was proposed: S. lutetiensis. It was named for Lutetia, a historical name for the city of Paris [4].

The species designation S. lutetiensis was not widely accepted, however. Based on further DNA-DNA hybridization experiments and the prior studies of the 16S rRNA, others have rejected the species name “S. lutetiensis” and maintain that it is a subspecies of S. infantarius as previously described [5].

So which name is correct? There appears to be no clear consensus about the designation of these streptococci, whether it is S. infantarius subsp. coli or whether it is another species altogether as S. lutetiensis. The Judicial Commission of the International Committee on Systematic Bacteriology reportedly met to discuss the name changes, however no resolution appears to have been determined [6]. Both names are seen in the literature as well as the names for reference organisms.

The important clinical aspect to recognize is that this organism, as well as the S. bovis group in general, can be a cause of bacteremia, endocarditis, and meningitis in children. Treatment with beta-lactam antibiotics is generally sufficient to cover these organisms.

References

  1. Farrow, J., et al., Taxonomic Studies on Streptococcus bovis and Streptococcus equinus: Description of Streptococcus alactolyticus sp. nov. and Streptococcus saccharolyticus sp nov. System. Appl. Microbiol, 1984. 5: p. 467-482.
  2. Bouvet, A., et al., Streptococcus infantarius sp. nov. related to Streptococcus bovis and Streptococcus equinus. Adv Exp Med Biol, 1997. 418: p. 393-5.
  3. Schlegel, L., et al., Streptococcus infantarius sp. nov., Streptococcus infantarius subsp. infantarius subsp. nov. and Streptococcus infantarius subsp. coli subsp. nov., isolated from humans and food. Int J Syst Evol Microbiol, 2000. 50 Pt 4: p. 1425-34.
  4. Poyart, C., G. Quesne, and P. Trieu-Cuot, Taxonomic dissection of the Streptococcus bovis group by analysis of manganese-dependent superoxide dismutase gene (sodA) sequences: reclassification of ‘Streptococcus infantarius subsp. coli’ as Streptococcus lutetiensis sp. nov. and of Streptococcus bovis biotype 11.2 as Streptococcus pasteurianus sp. nov. Int J Syst Evol Microbiol, 2002. 52(Pt 4): p. 1247-55.
  5. Schlegel, L., et al., Reappraisal of the taxonomy of the Streptococcus bovis/Streptococcus equinus complex and related species: description of Streptococcus gallolyticus subsp. gallolyticus subsp. nov., S. gallolyticus subsp. macedonicus subsp. nov. and S. gallolyticus subsp. pasteurianus subsp. nov. Int J Syst Evol Microbiol, 2003. 53(Pt 3): p. 631-45.
  6. Beck, M., R. Frodl, and G. Funke, Comprehensive study of strains previously designated Streptococcus bovis consecutively isolated from human blood cultures and emended description of Streptococcus gallolyticus and Streptococcus infantarius subsp. coli. J Clin Microbiol, 2008. 46(9): p. 2966-72.

 

IJF

-I.J. Frame MD, PhD, is a 1st year Clinical Pathology Resident at UT Southwestern Medical Center.

Erin McElvania TeKippe, PhD, D(ABMM), is the Director of Clinical Microbiology at Children’s Medical Center in Dallas Texas and an Assistant Professor of Pathology and Pediatrics at University of Texas Southwestern Medical Center.

Microbiology Case Study: A 28 Year Old Woman with Acute Onset Fever Post Delivery

Case History

A 28 year old woman at 37 weeks and 2 days presented in labor to our ED. After 22 hours, she delivered a healthy baby boy and sustained a second degree perineal laceration requiring repair. On hospital day 2, she reported feeling lightheaded, nauseous and “shaky.” She attempted to walk around the unit but became tremulous and unsteady, requiring assistance to get back into bed. Her vital signs were as follows: febrile at 38.8 C, BP 108/54, HR 104 and normal respiration rate at 12 breaths/min. On exam, she appeared pale and lethargic, and was noted to have a tender uterus on palpation. Based on her presentation and status post SVD, the diagnosis of endometritis was established. Blood cultures were obtained and within 16 hours, blood culture bottles were positive for gram-positive cocci. The patient was started on antibiotic therapy with ampicillin, gentamycin and clindamycin, and clinically improved within 36 hours.

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Image 1. Blood culture on blood agar.
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Image 2. Blood culture on chocolate agar.

Discussion

Streptococcus pyogenes is one of the most aggressive pathogens encountered in clinical microbiology. It is a beta hemolytic streptococcus and is notoriously associated with Streptococcal Toxic Shock Syndrome (STSS), necrotizing fasciitis, as well as more benign (yet still problematic) conditions, like Scarlet Fever, Impetigo, Rheumatic heart disease and Acute Post-streptococcal Glomerulonephritis. A gram-positive cocci, it possesses several virulence factors, including protein F, M protein (involved in antigen mimicry leading to valvular heart disease) hemolysins and exotoxins. These factors allow S. pyogenes to attach to and invade epithelial tissue, and in the case of hyalurondiase, potentially use hyaluron as a carbon food source. S. pyogenes agglutinates with Lancefield group A antisera and is pyrrolidonyl arylamidase (PYR) positive and VP, hippurate and CAMP test negative. Penicillin (PCN) remains the drug of choice in treating most S. pyogenes infections. Alternative antibiotic therapy includes macrolides and certain cephalosporins (e.g. cefixime, cefpodoxime). Vancomycin should be used in more severe infections such as sepsis or for patients with a PCN allergy.

 

-Christina Litsakos is a Pathology Student Fellow at University of Vermont Medical Center.

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

 

Microbiology Case Study: A 47 Year Old Woman with Three Day History of Fever

Case History

A 47 year old Caucasian female presented to her primary care physician with a three day history of fever (Tmax 102°F), chills and generalized body aches. Her rapid influenza test was negative, but she was treated with oseltamivir for suspected viral infection. Her past medical history was significant for severe mitral regurgitation for which she had had a prosthetic valve replacement two years prior, ischemic cardiomyopathy with recent pacemaker placement one month prior and an undifferentiated connective tissue disease. Her current medications included hydroxychloroquine (Plaquenil) and warfarin. Her symptoms persisted and upon return to clinic, a urinalysis was performed and blood cultures were collected. On physical exam, the pacemaker site was erythematous and tender to palpation. She was started on doxycycline and fluconazole for a presumed urinary tract infection. After 4 days of incubation on the automated instrument, the two aerobic blood cultures bottles were positive and the patient was admitted to the hospital for further workup and therapy.

Laboratory Identification

Microscopic examination from the positive blood culture bottle revealed slender, beaded Gram positive bacilli (Figure 1). No definitive branching was identified. Given the morphology on Gram stain, a Kinyoun stain was performed and revealed red-purple, beaded acid fast bacilli which were consistent with a Mycobacterium spp. (Figure 2). A Mycobacterial Growth Indicator Tube (MGIT), a Lowenstein Jensen slate and blood & chocolate agars were inoculated with specimen. Given that the organism grew after 2 days, a rapidly growing Mycobacterium spp. was suspected (Figure 3). High performance liquid chromatography (HPLC) identified the organism as M. fortuitum.

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Figure 1. Gram stain from the positive blood culture bottle showed slender, beaded Gram positive bacilli that were arranged in clumps (100x oil immersion).

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Figure 2. Kinyoun stain of the organisms was consistent with acid fast bacilli (100x oil immersion).

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Figure 3. Small, off-white colonies grew on chocolate agar after 3 days of incubation at 35°C in a CO2 incubator.

Discussion

M. fortuitum is a common rapid growing mycobacterial species that is ubiquitous in the environment and tap water. Most common infections due to M. fortuitum include post-traumatic or post-surgical wound infections and it can be associated with the insertion of prosthetic devices including heart valves, artificial joints and rods inserted after fractures. Of the rapid grower group (Runyon Group IV), which includes M. chelonae, M. abscessus and M. mucogenicum, it is M. fortuitum that accounts for approximately 60% of localized cutaneous skin infections and prosthetic device infections most frequently.

In the laboratory, M. fortuitum typically grows after two to five days incubation and appear as small, off-white colonies on a variety of different agars. The organism is typically slender, beaded Gram positive bacilli on Gram stain and positive for acid fast bacilli on a Ziehl-Neelsen or Kinyoun stain. As part of a traditional lab work up, M. fortuitum is arylsulfatase positive and is capable of reducing nitrates. Today a variety of methods, including HPLC, pyrosequencing, sequence analysis and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS), have become routine identification options. Susceptibility testing of isolates from clinically significant sites should be performed by broth microdilution and includes the following antimicrobials: amikacin, cefoxitin, ciprofloxacin, moxifloxacin, clarithromycin, doxycycline, linezolid, imipenem, meropenem, minocycline, trimethoprim-sulfamethoxazole and tobramycin.

In the case of our patient, it was discovered her pacemaker site was infected and upon further questioning it was discovered she wasn’t able to complete her antibiotic course after device placement due to nausea. A transesophageal echocardiogram showed no evidence of infective endocarditis and she was taken to the operating room for removal of the pacemaker and leads. The site was filled with pus and wound cultures obtained during surgery were consistent with M. fortuitum as well. Repeat blood cultures were negative and she was treated with intravenous amikacin and imipenem as well as oral levofloxacin for an anticipated 6-8 weeks before transitioning to oral therapy.

 

-Debbie Rigney Walley, MD, is a 1st year Anatomic and Clinical Pathology Resident at the University of Mississippi Medical Center.

Stempak

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

Microbiology Case Study: A 73 Year Old Man with Back Pain

Case History

A 73 year old man with a history of multiple back surgeries presented with bilateral lower extremity back pain of over greater than one month duration. Prior surgeries included L4/L5 fusion with pedicel screws and a decompression laminectomy one year prior to presentation. Imaging of his spine showed a fluid collection in his lumbar spine and he underwent several tissue biopsies over the course of a month which consistently showed no growth. Despite negative cultures he was treated with doxycycline and levoquin for 30 days. He was transferred to University of Vermont Medical Center (UVMMC) for IR drainage and tissue biopsy of this lumbar abscess as he continued to complain of back pain and had begun to develop bilateral lower extremity weakness. Cultures grow the organism below and close inspection revealed the presence of small feet. The organism was confirmed to be Candida albicans.

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Discussion

Vertebral osteomyelitis due to Candida is rare, however, a review of the literature reveals that most patients have lower thoracic or lumbar spine involvement and over 80% present with >1 month of lower back pain. An elevated white blood cell count is not as sensitive as an elevated erythrocyte sedimentation rate and of all patients, less than a quarter have neurologic signs. Candida albicans was responsible for almost 2/3 of cases and the remaining cases were caused by Candia tropicalis or Candida glabrata.1 Risk factors include IV drug abuse for patients under 25 years old; for elderly patients a central venous catheter, antibiotic use and immunosuppression .1

 

Reference

Miller, D and Mejicano, George. Vertebral Osteomyelitis due to Candida species: Case report and review of the literature. Clinical Infectious Diseases, 2001;33:523-530.

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

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