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Cerebral abscess usually occur when bacteria or fungi enter your brain either through your bloodstream or from an infected area in your head, such as your ears or sinuses. Additionally, an injury sustained to your head can allow germs to enter leading to an abscess ("Cerebral Abscess", 2023).

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A 66 year old man with suspected lung cancer was admitted due to 3 weeks of dizziness, headaches, and gait instability in the setting of a cerebellar brain mass.

A computerized Tomography (CT) scan revealed a 3.7 cm mass that was rapidly enlarging compared to previous scans.

A suboccipital craniectomy which involves removing a section of the skull behind the ear ("Suboccipital", 2021) was performed to biopsy the mass. During this time yellow purulent material was collected and sent to the microbiology lab.

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CT scan of the brain shows a tumor in the cerebellum (Sakurai et al. 2014)

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Bacteroides fragilis

Klebsiella pneumoniae

Listeria monocytogenes

Mycobacterium tuberculosis

Nocardia spp.

Peptostreptococcus spp.

Prevotella spp.

Propionibacterium acnes

Pseudomonas aeruginosa

Staphylococcus spp.

Streptococcus spp.

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Cryptococcus spp.

Fusarium spp.

Aspergillus

Zygomycetes

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Toxoplasma gondii

Naeglaria fowleri

Acanthamoeba

Balamuthia mandrillaris

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After the identification of Nocardia farcinica from the brain abscess, infectious disease doctors hypothesized that the mas seen in the lung was in fact pulmonary nocardiosis and not lung cancer.

The patient was started on IV Bactrim and Imipenem for 6 weeks and will be discharged on oral antibiotics for an additional year.

The patient is currently recovering well and is expected to make a full recovery.

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Many branching weakly Gram positive bacilli

Beaded appearance

This suggests Nocardia spp.

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Consistent with Nocardia spp.

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After discovering the bacterial infection was caused from Nocardia farcinica an antimicrobial susceptibility test (AST) was performed in order to predict how an organism will respond to antimicrobial therapy in the infected host.

This testing not only helps a clinician select the appropriate antimicrobial agent but it further aids in developing antimicrobial use policy, provides data for epidemiological surveillance, and to detect the emergence and/or the dissemination of resistant strains.

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1.) Disk Diffusion
The diffusion of an antimicrobial agent from disks, tablets, or strips, into the solid culture medium that has been seeded with the selected inoculum isolated in a pure culture. Generally, the larger the zone of inhibition, the lower the concentration of antimicrobial required to inhibit the growth of the agent ("Laboratory Methodologies").

2.) Broth Dilution
Antibiotics are serially diluted in a microtiter plate and then a suspension of bacteria is added. The first concentration of antibiotic where there is no growth is called the minimum inhibitory concentration (MIC) ("Laboratory Methodologies").

3.) Agar Dilution
Involves incorporating varying concentrations of antimicrobial agent into an agar medium using serial dilutions, followed by the application of a defined bacterial inoculum to the agar surface of the plate ("Laboratory Methodologies").

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Results of antimicrobial susceptibility tests

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Imipenem and Bactrim (Trimethoprim/Sulfamethoxazole) were used to treat the patient as the microbial agent was susceptible to them at the lowest concentrations.

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allows for quick visualization of organisms directly from the sample

Gram Stain: A differential staining technique that distinguishes organisms as Gram negative (stained pink) or Gram positive (stained purple) based off either cell membrane structure (Leboffe, 2015).

Procedure:

1. Begin with a heat-fixed emulsion on one slide

2. Cover the smear with crystal violet for one minute over a staining tray

3. Gently rinse the slide with distilled water into the staining tray

4. Cover the smear with Gram iodine stain for one minute

5. Gently rinse the slide with distilled water into the staining tray

6. Decolorize with ethanol by allowing it to trickle down the slide until the runoff is clear

7. As soon as the runoff is clear, immediately rinse the slide with distilled water

8. Counterstain the smear with safranin for one minute

9. Gently rinse the slide with distilled water

10. Gently blot dry in bibulous paper. Once dry, observe under oil immersion

Acid Fast Stain: A staining procedure that differentiates between bacteria based on their ability to retain a dye when washed with an acid alcohol solution. Bacterial cells that are not easily decolorized by acidified alcohol are said to be acid-fast (stain red), while nonacid-fast bacteria are easily decolorized (stain blue).

Procedure

1. Prepare a slide with a drop of sheep serum and mix in bacterial cells before allowing to air dry and then proceed to heat-fix the smear

2. Cover the smear with a strop of bibulous paper and apply ZN carbolfuchsin stain while on a steaming apparatus. Heat the slide for 5 minutes while keeping the paper moist

3. Remove the bibulous paper, and gently rinse both sides of the slide with distilled water

4. Decolorize the stain with acid-alcohol until the runoff is clear and immediately rinse with distilled water

5. Counterstain with methylene blue for one minute

6. Gently rinse the slide with distilled water and blot dry with bibulous paper. Once dry, observe under oil immersion

Kinyoun (modified acid fast): uses a slightly more lipid-soluble and concentrated carbolfuchsin as the primary stain. This allows the stain to penetrate the acid-fast walls without the use of heat

Procedure

1. Prepare a slide with a drop of sheep serum and bacterial cells. Mix together and then heat fix

2. Apply Kinyoun carbolfuchsin for 5-10 minutes but do not heat the slides

3. Gently rinse the slide with distilled water

4. Decolorize with acid-alcohol until the run-off is clear and immediately rinse with distilled water.

5. Counterstain the smear with methylene blue for 1 minute

6. Gently rinse the slide with distilled water and blot dry with bibulous paper. Once, dry, observe under oil immersion (Leboffe, 2015).

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Four-sectored plate containing four different media

Used for differentiating and identifying Nocardia spp.

("BD BBL Nocardia ID Quad")

Quadrant 1 contains Casein agar

There should be growth with no clear zones

Quadrant 2 contains Starch agar

There should be growth with blue or purple zones

Quadrant 3 contains Tyrosine agar

There should be growth with no clear zones

Quadrant 4 contains Xanthine agar

There should be growth with no clear zones

("BD BBL Nocardia ID Quad")

Growth pattern consistent with Nocardid asteroides complex

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2+ growth on blood agar and chocolate plates after 48 hours

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16s sequencing involves sequencing the 16s rRNA gene that codes for the small subunit (SSU) of the ribosome found in prokaryotes such as bacteria and archaea

with PCR analysis, BLAST technology, and the GenBank database sequence homology identified the organisms as Nocardia farcinica

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Provides a wide range of supplements to encourage growth of any organism present in the sample

Aerobic/Anaerobic

Fungal

Acid Fast Bacilli

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From already working at a hospital and going into the medical field I have always found diseases and viruses to be very interesting. As I learn about different bacteria and viruses I can further understand some of the diseases patients have and the overall pathogenesis of these agents. I look forward to expanding my knowledge about bacterial infections, diseases, and viruses. In addition, being able to see the different cell structures, and categories different types of bacteria fall into. It is one thing to read about them but another to look through a microscope and see what you have read about. Just from going through this case study you discover the connections between what we are learning and real life experiences.

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"BD BBL Nocardia ID Quad." , Becton, Dickinson and Company. Accessed 9 Feb. 2023. Path: https://www.bd.qarad.eifu.online/bdx/US/all; https://www.bd.qarad.eifu.online/bdx/US/all?keycode=8813481JAA.

"Cerebral Abscess." , John Hopkins Medicine, 2023, www.hopkinsmedicine.org/health/conditions-and-diseases/cerebral-abscess#:~:text=A%20cerebral%20abscess%20usually%20occurs,that%20can%20cause%20an%20abscess. Accessed 9 Feb. 2023.

Ding, Juanjuan, et al. "Detection of Nocardia by 16s Ribosomal RNA Gene PCR and Metagenomic Next-Generation Sequencing (mNGS)." Frontiers in Cellular and Infection Microbiology, vol. 11, 2022, https://doi.org/10.3389/fcimb.2021.768613. Accessed 9 Feb. 2023.

Laboratory Methodologies for Bacterial Antimicrobial Susceptibility Testing. OIE Reference Laboratory, https://www.woah.org/app/uploads/2015/02/guide-2-1-antimicrobial.pdf.

Leboffe, Michael J., and Burton E. Pierce. Microbiology laboratory Theory & Application. fourth ed., Morton Publishing, 2015.

Lu S-H, Qian Z-W, Mou P-P, Xie L. Clinical Nocardia species: Identification, clinical characteristics, and antimicrobial susceptibility in Shandong, China. Biomol Biomed [Internet]. 2020Nov.2 [cited 2023Feb.10];20(4):531-8. Available from: https://www.bjbms.org/ojs/index.php/bjbms/article/view/4764

McMurray DN. Mycobacteria and Nocardia. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 33. Available from: https://www.ncbi.nlm.nih.gov/books/NBK7812/

Sakurai, Katsunobu & Muguruma, Kazuya & Murata, Akihiro & Toyokawa, Takahiro & Amano, Ryosuke & Kubo, Naoshi & Tanaka, Hiroaki & Yashiro, Masakazu & Maeda, Kiyoshi & Ohira, Masaichi & Hirakawa, Kosei. (2014). Early gastric cancer with suspected brain metastasis arising eight years after curative resection: a case report. BMC research notes. 7. 818. 10.1186/1756-0500-7-818.

"Suboccipital surgery for acoustic neuroma." Mayfield Brain & Spine, edited by Vince DiNapoli, Mayfield Brain & Spine, Jan. 2021, d3djccaurgtij4.cloudfront.net/pe-acousticsurgery.pdf. Accessed 9 Feb. 2023.

Willey, Joanne, et al. Prescott's Microbiology. twelfth ed., McGraw, 2022.

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Aerobic, Gram-positive, branching/filamentous, weakly acid-fast bacteria (Ding, 2022)

Saprophytic and found in water, dust, and soil (Ding, 2022)

capable of causing either a localized or disseminated infection in both immunocompetent and immunocompromised hosts (Lu, 2020)

human infection results mainly from the inhalation of airborne bacilli or the traumatic inoculation of organisms into the skin (McMurray, 1996)

characterized by a variety of clinical manifestations involving the lungs, central nervous system, skin, and other organs (Lu, 2020)

Nocardiosis is usually associated with T-cell dysfunctions, immunoglobulin deficiencies, or leukocyte abnormalities (McMurray, 1996)

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Disseminated disease occurs frequently

One study noted CNS involvement in one third of cases studies

Most patients have a compromised immune status