Infectious Myositis

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Overview


By [Chris Santucci]

Infectious Myositis is an infection that can be caused by microbes of all domains. It is characterized by muscle inflammation and usually is seen in voluntary muscle. [1] It is an uncommon infection and is very diverse in the way it can come about. Infectious myositis can result from surgeries in which incisions allow microbes in, wounds that are contaminated, injectable drug needles that are unsterilized, undercooked foods, among other reasons, making it difficult to detect and prevent at first. Immunocompromised individuals are always at risk for myositis. Myositis is not caused by one microbial group, but rather can be caused by a broad range of microbes including bacteria, fungi, viruses, and parasites. The infection can be polymicrobial, but in many cases one organism dominates the infected site. In order to identify the specific microbe responsible, culturing is necessary. This page hopes to express the vast array of infection and treatments associated with the main types of myositis.

To the right is a photograph depicting a patient with myositis of the gastrocnemius. This is a typical case of myositis in voluntary skeletal muscle.

MRI of myositis of the gastrocnemius and multiple abscesses of the posterior compartment caused by community-acquired methicillin-resistant Staphylococcus. [1].


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Legend/credit: MRI of myositis of the gastrocnemius and multiple abscesses of the posterior compartment caused by community-acquired methicillin-resistant Staphylococcus. [9].
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Bacterial Infectious Myositis


Bacteria are the most common domain that can infect muscle leading to myositis from infection according to the literature. Staphylococcus aereus and Streptococcus strains, both gram-positive and typically facultative anaerobes, are the most common bacteria causing agents of myositis and are categorized into their own type of myositis. Some cases of bacterial myositis are polymicrobial, especially when infections are contaminated with soil. In events of bacterial myositis, it is necessary to culture on differential media and use gram staining to determine the bacteria responsible for the infection in order to treat the infection. Pyomyositis, psoas abscess, S. aereus myositis, group A and group B streptococcal myositis, Clostridial gas gangrene, and nonclostridial myositis are the distinctive categories of bacterial myositis. [3]

Pyomyositis
Pyomyositis, also known as tropical myositis because it is found often in tropical climates, is a bacterial infection due to hematogenous spread (spread through the blood stream) mainly caused by Staphylococcus aereus that is only present in one muscle group. [4]. This infection is often seen in children, but not always. [5] In fact, it can be found in people of all ages and is becoming more prevalent in the United States in the past 40 years. [6]
It was discovered that immunocompromised individuals, such as those with HIV, are more likely to acquire pyomyositis. [7] This can be attributed to many reasons, but most importantly the fact that S. aureus grows much more easily in immunocompromised people that have a weaker defense mechanism [8] Pyomyositis cases, in general, have increased since the HIV epidemic has broken out. [9]


Since pyomyositis occurs in single muscle groups, it is no surprise that cases of pyomyositis have been identified in bodybuilders who use anabolic steroids, known to increase athletic performance. Anabolic steroids are commonly injected into sites in which the athlete desires mass gain. [10] ,which poses more risks than just the detrimental effects anabolic steroids have on healthy individuals who do not need them for health reasons. In a case study, one bodybuilder began to have pain in his right arm and was diagnosed with pyomyositis of brachial biceps. The diagnosis was a result of culturing of a sample of the patient’s steroid needle, which was positive for S. aereus, which can be treated with antibiotics. [11] Another bodybuilding, anabolic steroid-user with the same diagnosis of S. aereus pyomyositis in the brachial biceps underwent surgical cleaning and a Penrose drain (essentially a tube that drains fluid after surgery) was used in addition to antibiotic treatment. [12] In a third similar case, a steroid user was found to have pyomyositis of the brachial biceps and ipsilateral triceps with culturing revealing presence of S. viridians, which was treated with antibiotics. A picture of magnetic resonance imaging of the bicep can be seen to the right.

Magnetic resonance imaging of myositis by S. viridians in the bicep of an anabolic steroid user. [2].


In all three cases, the athletes were able to return to full athletic activity within 42 days. Since anabolic steroids in bodybuilders, among other drugs administered without clinical approval, are injected in a nonsterile site, the site at which the steroids are injected is at high risk for infections i.e. pyomyosits.


Magnetic resonance imaging of myositis by S. viridians in the bicep of an anabolic steroid user. [3].



CT scan of psoas abscess by Streptococcus pyogenes in HIV patient. [4].


CT scan of psoas abscess by Streptococcus aereus. [5].


MRI of Group B_streptococcal myositis in right rectus muscle identified with the arrow. [6].


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Myositis by Fungi

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Myositis by Viral infection

MRI of bicep parasitic myositis by Taenia solium. [7].


Parasitic Myositis

Micrograph of the unidentified fungi in a case of fungal myositis. [8].


Conclusion

References

  1. ↑ [Crum-Cianflone, Nancy F. “Bacterial, Fungal, Parasitic, and Viral Myositis.” Clinical Microbiology Reviews 21.3 (2008): 473–494. PMC]
  2. ↑ Bartlett et al.: Oncolytic viruses as therapeutic cancer vaccines. Molecular Cancer 2013 12:103.
  3. ↑ [Crum-Cianflone, Nancy F. “Bacterial, Fungal, Parasitic, and Viral Myositis.” Clinical MicrobiologyReviews 21.3 (2008): 473–494. PMC]
  4. ↑ [Crum-Cianflone, Nancy F. “Bacterial, Fungal, Parasitic, and Viral Myositis.” Clinical Microbiology Reviews 21.3 (2008): 473–494. PMC]
  5. ↑ [Horn, C. V., and S. Master. 1968. Pyomyositis tropicans in Uganda. East Afr. Med. ]
  6. ↑ [Levin, M. J., and P. Gardner. 1971. “Tropical” pyomyositis: an unusual infection due to Staphylococcus aureus. N. Engl. J. Med. 284:196-198.]
  7. ↑ [Crum-Cianflone, Nancy F. “Bacterial, Fungal, Parasitic, and Viral Myositis.” Clinical Microbiology Reviews 21.3 (2008): 473–494. PMC]
  8. ↑ [Widrow, C. A., S. M. Kellie, B. R. Saltzman, and U. Mathur-Wagh. 1991. Pyomyositis in patients with the human immunodeficiency virus: an unusual form of disseminated bacterial infection. Am. J. Med]
  9. ↑ [Christin, L., and G. A. Sarosi. 1992. Pyomyositis in North America: case reports and review. Clin. Infect. Dis. 15:668-677]
  10. ↑ [Filho, Nivaldo Souza Cardozo et al. “PYOMYOSITIS IN ATHLETES AFTER THE USE OF ANABOLIC STEROIDS - CASE REPORTS.” Revista Brasileira de Ortopedia 46.1 (2011): 97–100. PMC]
  11. ↑ [Filho, Nivaldo Souza Cardozo et al. “PYOMYOSITIS IN ATHLETES AFTER THE USE OF ANABOLIC STEROIDS - CASE REPORTS.” Revista Brasileira de Ortopedia 46.1 (2011): 97–100. PMC]
  12. ↑ [Filho, Nivaldo Souza Cardozo et al. “PYOMYOSITIS IN ATHLETES AFTER THE USE OF ANABOLIC STEROIDS - CASE REPORTS.” Revista Brasileira de Ortopedia 46.1 (2011): 97–100. PMC]



Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2017, Kenyon College.

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