My patient with sepsis and bacteremia has an extremely high serum Creatine kinase (CK) level. Can his infection be causing rhabdomyolysis?

 Absolutely! Although trauma, toxins, exertion, and medications are often listed as common causes of rhabdomyolysis, infectious etiologies should not be overlooked as they may account for 5% to 30% or more of rhabdomyolysis cases (1,2).

 

Rhabdomyolysis tends to be associated with a variety of infections, often severe, involving the respiratory tract, as well as urinary tract, heart and meninges, and may be caused by a long list of pathogens (1).  Among bacterial causes, Legionella sp. (“classic” pathogen associated with rhabdomyolysis), Streptococcus sp. (including S. pneumoniae), Salmonella sp, Staphylococcus aureus, Francisella tularensis have been cited frequently (3).  Some series have reported a preponderance of aerobic gram-negatives such as Klebsiella sp., Pseudomonas sp. and E. coli  (1,2).   Among viral etiologies, influenza virus, human immunodeficiency virus, and coxsackievirus are commonly cited (2,3).  Fungal and protozoal infections (eg, malaria) may also be associated with rhabdomyolysis (5).

 

So how might sepsis cause rhabdomyolysis? Several potential mechanisms have been implicated, including tissue hypoxemia due to sepsis, direct muscle invasion by pathogens (eg, S. aureus, streptococci, Salmonella sp.), toxin generation (eg, Legionella), cytokine-mediated muscle cell toxicity (eg, aerobic gram-negatives) as well as muscle ischemia due to shock (1,5).

 

Bonus Pearl: Did you know that among patients with HIV infection, infections are the most common cause (39%) of rhabdomyolysis (6)? 

 

Liked this post? Download the app on your smart phone and sign up under MENU to catch future pearls right into your inbox!

References

 

1. Kumar AA, Bhaskar E, Shantha GPS, et al. Rhabdomyolysis in community acquired bacterial sepsis—A retrospective cohort study. PLoS ONE 2009;e7182. Doi:10.1371/journa.pone.0007182. https://www.ncbi.nlm.nih.gov/pubmed/19787056.

2. Blanco JR, Zabaza M, Sacedo J, et al. Rhabdomyolysis of infectious and noninfectious causes. South Med J 2002;95:542-44. https://www.ncbi.nlm.nih.gov/pubmed/12005014

3. Singh U, Scheld WM. Infectious etiologies of rhabdomyolysis:three case reports and review. Clin Infect Dis 1996;22:642-9. https://www.ncbi.nlm.nih.gov/pubmed/8729203

4. Shih CC, Hii HP, Tsao CM, et al. Therapeutic effects of procainamide on endotoxin-induced rhabdomyolysis in rats. PLOS ONE 2016. Doi:10.1371/journal.pone.0150319. https://www.ncbi.nlm.nih.gov/pubmed/26918767

5. Khan FY. Rhabdomyolysis: a review of the literature. NJM 2009;67:272-83. http://www.njmonline.nl/getpdf.php?id=842

6. Koubar SH, Estrella MM, Warrier R, et al. Rhabdomyolysis in an HIV cohort: epidemiology, causes and outcomes. BMC Nephrology 2017;18:242. DOI 10.1186/s12882-017-0656-9. https://bmcnephrol.biomedcentral.com/track/pdf/10.1186/s12882-017-0656-9

My patient with sepsis and bacteremia has an extremely high serum Creatine kinase (CK) level. Can his infection be causing rhabdomyolysis?

How should I interpret the growth of “normal respiratory flora” from sputum of my patient with community-acquired pneumonia (CAP)?

Since the primary reason for obtaining a sputum culture in a patient with pneumonia is to sample the lower respiratory tract, you should first verify that the sputum was “adequate” by reviewing the gram stain. Absence of neutrophils (unless the patient is neutropenic) with or without epithelial cells on gram stain of sputum suggests that it may not be an adequate sample (ie, likely saliva)1, and therefore growth of normal respiratory flora (NRF) should not be surprising in this setting.  

Other potential explanations for NRF on sputum culture in patients with CAP include:2-5

  • Delay in sputum processing with possible overgrowth of oropharyngeal flora.
  • Pneumonia caused by pathogens that do not grow on standard sputum culture media (eg, atypical organisms, viruses, anaerobes).
  • Pneumonia caused by potential pathogens such as as Streptococcus mitis and Streptococcus anginosus group that may be part of the NRF.
  • Initiation of antibiotics prior to cultures (eg, in pneumococcal pneumonia).

Of note, since 2010, several studies have shown that over 50% of patients with CAP do not have an identifiable cause.3 So, growing NRF from sputum of patients with CAP appears to be common.

References

  1. Wong LK, Barry AL, Horgan SM. Comparison of six different criteria for judging the acceptability of sputum specimens. J Clin Microbiol 1982;16:627-631. https://www.ncbi.nlm.nih.gov/pubmed/7153311
  2. Donowitz GR. Acute pneumonia. In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases (2010). Churchill Livingstone, pp 891-916.
  3. Musher DM, Abers MS, Bartlett JG. Evolving understanding of the causes of pneumonia in adults, with special attention to the role of pneumococcus. Clin Infect Dis 2017;65: 1736-44. https://www.ncbi.nlm.nih.gov/pubmed/29028977
  4. Abers MS, Musher DM. The yield of sputum culture in bacteremic pneumococcal pneumonia after initiation of antibiotics. Clin Infect Dis 2014; 58:1782. https://www.ncbi.nlm.nih.gov/pubmed/24604901
  5. Bartlett JG, Gorbach SL, Finegold SM. The bacteriology of aspiration pneumonia. Bartlett JG, Gorbach SL, Finegold SM. Am J Med 1974;56:202-7. https://www.ncbi.nlm.nih.gov/pubmed/4812076
How should I interpret the growth of “normal respiratory flora” from sputum of my patient with community-acquired pneumonia (CAP)?

Do most patients with mycotic aneurysms have endocarditis?

No! In fact, the great majority of patients who develop mycotic aneurysm (MAs) in the postantibiotic era have no evidence of endocarditis1-3.

MAs are thought to be related to microbial arteritis due to blood stream infection of any source with implantation of circulating pathogen (usually bacterial) in atherosclerotic, diseased, or traumatized aortic intima. Plus, MAs may develop due to an adjacent infectious process (eg, vertebral osteomyelitis), either through direct extension or via lymphatic vessels, pathogen seeding of vasa vasorum, or infection of a pre-existing aneurysm1,2.  All these factors may occur in the absence of endocarditis.

Many of your patients may be at risk of MA such as those with advanced age or history of diagnostic or therapeutic arterial catheterization, illicit intravascular drug use, hemodialysis and depressed host immunity1-3..  Staphylococcus aureus, Salmonella sp, S. epidermidis and Streptococcus sp are common culprits in descending order1-3.

So think of MA in your patient with recent blood stream infection,  particularly due to S. aureus or Salmonella sp, in the setting of persistent signs of infection  with or without evidence of endocarditis.

Final Fun Fact: Did you know that the term “mycotic aneurysm” is a misnomer, having been first introduced by Sir William Osler to describe aneurysms of the aortic arch in a patient with (you guessed it) bacterial not fungal endocarditis?

References:

  1. Gomes MN, Choyke PL, Wallace RB. Infected aortic aneurysms: A changing entity. Ann Surg 1992;215:435-42. https://www.ncbi.nlm.nih.gov/pubmed/1616380
  2. Muller BT, Wegener OR, Grabitz K, et al. Mycotic aneurysms of the thoracic and abdominal aorta and iliac arteries: Experience with anatomic and extra-anatomic repair in 33 cases. J Vasc Surg 2001;33:106-13. https://www.ncbi.nlm.nih.gov/pubmed/11137930
  3. Mukherjee JT, Nautiyal A, Labib SB. Mycotic aneurysms of the ascending aorta. Tex Heart Inst J 2012;39:692-5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3461658/
Do most patients with mycotic aneurysms have endocarditis?