Month: May 2023

My newly-admitted patient has positive blood cultures for Staphylococcus aureus.  How long should his S. aureus bacteremia be treated?

FA Manian MD, MPH, , , , , , , , , , , , , , , Leave a comment

Because of the tendency of S. aureus bacteremia (SAB) to disseminate (eg, endocarditis, spinal epidural abscess, other metastatic infections), it should be treated with a minimum of 2 weeks of IV antibiotics following first repeat negative blood cultures, irrespective of the source of infection or rate of clinical improvement. 1-6

Beyond 2 weeks, the ultimate duration of parenteral antibiotics for treatment of SAB depends on several factors, including whether it is considered an “uncomplicated” or “complicated”. 1,2

Generally, uncomplicated SAB is defined as:

  • Negative results of follow-up blood culture at 2-4 days after bacteremia and
  • Clinical defervescence within 72 h of IV therapy and removal of the presumed focus of infection (eg, debridement of soft tissue infection or IV catheter) and
  • No evidence of metastatic infection among patients with catheter-related bloodstream infection or with primary bacteremia without evidence of endocarditis on transthoracic (TTE) or transesophageal echocardiogram (TEE) and
  • No endovascular foreign material (eg, prosthetic devices)

Patients not meeting the above criteria should be considered to have complicated SAB. Some studies have also reported primary bacteremia without obvious source and community-acquired SAB as risk factors for complications.4,6  

Even uncomplicated SAB should still receive at least 2 weeks of IV anti-staphylococcal therapy.  In a prospective observational study involving 111 patients with uncomplicated SAB, shorter course (<2 weeks) of IV antibiotic therapy was associated with significantly higher rate of relapse with a trend toward primary bacteremia associated with increased treatment failure.4

All other patients not considered to have an uncomplicated SAB, should receive extended antibiotic therapy (eg, 4-6 weeks or longer) depending on several factors, including clinical course and suspicion for a diagnosis of established metastatic disease (eg, endocarditis, spinal epidural abscess, etc…).  Continued parenteral antibiotic therapy is standard practice as there is insufficient data to support use of oral antibiotics in the treatment of complicated SAB before 4-6 weeks of therapy is completed.2

Standard practice in the treatment of SAB should also include an infectious disease (ID) consultation which has been associated with significantly reduced rates of mortality and risk of relapse.7

 Bonus Pearl: Did you know that SAB is associated with a mortality of 20-30% in developed countries despite antibacterial therapies and source control strategies? 1

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References

  1. Lam JC, Stokes W. The golden grapes of wrath—Staphylococcus aureus bacteremia: A clinical review. Am J Med 2023, 136:19-26. https://pubmed.ncbi.nlm.nih.gov/36179908/
  2. Kimming A, Hagel St, Weis S, et al. Management of Staphylococcus aureus bloodstream infections. Frontiers in Medicine 2021; 7: Article 616524. https://www.frontiersin.org/articles/10.3389/fmed.2020.616524/full
  3. Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin Infect Dis 52:e18-e55. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/216060
  4. Chong YP, Moon SM, Bang KM, et al. Treatment duration for uncomplicated Staphylococcus aureus bacteremia to prevent relapse: Analysis of a prospective observational cohort study. Antimicrob Agents Chemother 2013;57:1150-56. https://pubmed.ncbi.nlm.nih.gov/23254436/
  5. Kuehl R, Morata L, Boeing C, et al. Defining persistent Staphylococcus aureus bacteremia: secondary analysis of a prospective cohort study. Lancet 2020;20: 1409-17. https://pubmed.ncbi.nlm.nih.gov/32763194/
  6. Fowler VG, Olsen MK, Corey R, et al. Clinical identifiers of complicated Staphylococcus aureus Arch Intern Med 2003;163:2066-72. https://pubmed.ncbi.nlm.nih.gov/14504120/
  7. Vogel M, Schmitz RPH, Hagel S, et al. Infectious disease consultation for Staphylococcus aureus bacteremia—A systematic review and meta-analysis. J Infect 2016, 72:19-28. https://pubmed.ncbi.nlm.nih.gov/26453841/ 

Disclosures/Disclaimers: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

My newly-admitted patient has positive blood cultures for Staphylococcus aureus.  How long should his S. aureus bacteremia be treated?

The urine culture of my female patient with urgency is growing Lactobacillus spp.  Should I treat it?

FA Manian MD, MPH, , , , , , , , Leave a comment

Lactobacillus spp. isolated from urine generally does not require treatment because these organisms are often part of the normal bacterial flora of the genitourinary (GU) and gastrointestinal tracts, are generally of low virulence, are rarely associated with urinary tract infections (UTIs) and may in fact have potential benefits in preventing UTIs. 1-4

In a study involving female urinary microbiome, subjects with urgency urinary incontinence were less likely to have Lactobacillus spp. based on 16S rRNA gene sequencing of transurethral catheter urine than those without symptoms, suggestive of possible protective role of this organism in female GU tract.1

Although Lactobacillus UTI is rare, one particular species, Lactobacillus delbrueckii, has been implicated in several case reports involving primarily elderly women.3,4

Vaginal colonization with lactobacilli provides a natural, nonspecific defense mechanism against infection in part by production of lactic acid and lowering of the regional pH which, when combined with hydrogen peroxide production by commensal anaerobes, interferes with colonization of the vaginal mucosal surfaces by potential pathogens. Lactobacilli also interfere with the adherence of pathogens by production of biosurfactants.3 It’s no surprise that lactobacilli are often considered “friendly bugs” and used in many probiotic preparations.

Bonus Pearl: Did you know that contrary to the current dogma, urine is not necessarily sterile.  Even in asymptomatic people, it may contain several organisms, including Lactobacillus, Gardnerella, Streptococcus, Staphylococcus (not aureus) and Corynebacterium? 5

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References

  1. Pearce MM, Hilt EE, Rosenfeld AM, et al. The female urinary microbiome: a comparison of women with and without urgency urinary incontinence. mBio 2014;5:e01283-14. https://pubmed.ncbi.nlm.nih.gov/25006228/
  2. Thomas-White K, Forster SC, Kumar N, et al. Culturing of female bladder bacteria reveals an interconnected urogenital microbiota. Nature Communications 2018;9:1557. https://www.nature.com/articles/s41467-018-03968-5.pdf (urine not sterile, bladder with lactobacillus prevention, normal asymptomatic
  3. Darbro BW, Petroelje BK, Doern GV. Lactobacillus delbureckii as the cause of urinary tract infection. J Clin Microbiol 2009;47:275-277. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2620876/#:~:text=Urinary%20tract%20infections%20caused%20by,a%20setting%20of%20ureteral%20obstruction.
  4. Maillet F, Passeron A, Podglajen I, et al. Lactobacillus delbrueckii urinary tract infection in a male patient. Med Mal Infect 2019;49:225-230. https://www.sciencedirect.com/science/article/pii/S0399077X1830787X?via%3Dihub
  5. Reid G. The scientific basis for probiotic strains of Lactobacillus. App Env Microbiol 1999;65:3763-3766. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC99697/

Disclosures/Disclaimers: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

The urine culture of my female patient with urgency is growing Lactobacillus spp.  Should I treat it?