Should empiric coverage of Staphylococcus aureus bacteremia (SAB) routinely include an anti-staphyloccal β-lactam?

Although there are no clinical trials comparing  therapy with vancomycin and β-lactam to vancomycin alone in the empiric treatment of S. aureus bacteremia (SAB), combination therapy has been advocated by some based on reports of reduced morbidity and mortality (1). More recently however, a retrospective study involving 122 hospitals failed to find superiority of vancomycin-β-lactam combination therapy compared to vancomycin alone for empiric therapy of SAB (2).

We do know that despite its activity against methicillin-susceptible S. aureus (MSSA), vancomycin is less bactericidal (3), with a higher rate of relapse than anti-staphylococcal β-lactams in the treatment of established SAB (4).

So although it may not be clear if we need to empirically place all of our patients suspected of SAB on a vancomycin-β-lactam from the get go,  once MSSA has been confirmed, vancomycin should be dropped in favor of an anti-staphylococcal β-lactam.

 

References 

  1. McConeghy KW, Bleasdale SC, Rodvold KA. The empirical combination of vancomycin and a β-lactam for staphylococcal bacteremia. Clin Infect Dis 2013;57:1760-5.
  2. McDaniel JS, Perencevich EN, Diekema DJ, et al. Comparative effectiveness of beta-lactams versus vancomycin for treatment of methicillin-susceptible Staphylococcus aureus bloodstream infections among 122 hospitals. Clin Infect Dis 2015;61:361-7.
  3. Fernandez Guerrero ML, de Gorgolas M. Comparative activity of cloxacillin and vancomycin against methicillin-susceptible Staphylococcus aureus experimental endocarditis. J Antimicrob Chemother 2006;58:1066-1069.
  4. Chang F-Y, Peacock JE, Musher DM, et al. Staphylococcus aureus bacteremia: recurrence and the impact of antibiotic treatment in a prospective multicenter study. Medicine (Baltimore) 2003;82:333-9.
Should empiric coverage of Staphylococcus aureus bacteremia (SAB) routinely include an anti-staphyloccal β-lactam?

Is oral vancomycin prophylaxis (OVP) effective in preventing recurrent Clostridium difficile infection (CDI) in patients requiring systemic antimicrobial therapy (SAT)?

Although OVP is often administered to patients with history of CDI who require SAT, evidence to support this practice has been lacking until recently. In a retrospective study of 203 patients who received either OVP (125 mg or 250 mg 2x/daily) during the course of their SAT and up to 1 week thereafter vs no OVP,  CDI rate was significantly lower in the OVP group (4.2% vs 26.6%, respectively, O.R. 0.12 [C.I. 0.04-0.4]) (1). The mean age was 73 y (41-97 y), the mean interval between prior CDI and initiation of prophylaxis was 6.1 months (1-21 months), and the mean duration of prophylaxis following discontinuation of SAT was 1 day (0-6 days) in the OVP group.

Despite its retrospective nature, this study lends support to the use of OVP in reducing the risk of recurrent CDI in patients who require SAT. It is unclear how long OVP should be continued after SAT, if at all, but common practice is 1-2 weeks. More studies are clearly needed.

Disclosure: The author of this post is also a coauthor of the study cited.

 

Reference

  1. Van Hise NW, Bryant AM, Hennessey EK, Crannage AJ, Khoury JA, Manian FA. Efficacy of oral vancomycin in preventing recurrent Clostridium difficile infection in patients treated with systemic antimicrobial agents. Clin Infect Dis 2016; Advance Access published June 17, 2016. Doi.10.1093/cid/ciw401.
Is oral vancomycin prophylaxis (OVP) effective in preventing recurrent Clostridium difficile infection (CDI) in patients requiring systemic antimicrobial therapy (SAT)?

Does electroconvulsive therapy (ECT) pose a risk of embolic stroke in patients with atrial fibrillation (AF)?

Acute embolic stroke in the setting of AF without anticoagulation after ECT has been reported in a single case report in the absence of conversion to normal sinus rhythm (1). Several cases of episodic or persistent conversion to normal sinus rhythm (NSR) in patients with AF undergoing ECT have also been reported (in the absence of embolic stroke), leading some to recommend anticoagulation therapy in such patients (2), though no firm data exist.

The mechanism by which ECT promotes cardioversion from AF to NSR is unclear as direct electrical influence of ECT on the heart is thought to be negligible (1). Arrhythmias such as atrial flutter and AF have also been reported after ECT (1). Curiously, ECT is associated with increased 5- hydroxytryptamine (5- HT2)-receptor densities of platelets in patients with depression which may enhance platelet reactivity and increase the risk of embolic stroke (3) even in the absence of cardioversion.

 

References

  1. Suzuki H, Takano T, Tominaga M, et al. Acute embolic stroke in a patient with atrial fibrillation after electroconvulsive therapy. J Cardiol Cases 2010; e12-e14.
  2. Petrides G, Fink M. Atrial fibrillation, anticoagulation, electroconvulsive therapy. Convulsive Therapy 1996;12:91-98.
  3. Stain-Malmgren R, Tham A, Ǻberg-Wistedt A. Increased platelet 5-HT2 receptor binding after electroconvulsive therapy in depression. J ECT 1998;14:15-24.
Does electroconvulsive therapy (ECT) pose a risk of embolic stroke in patients with atrial fibrillation (AF)?

Is cefpodoxime an appropriate oral antibiotic substitute for ceftriaxone when treating patients with respiratory tract infections caused by penicillin-resistant Streptococcus pneumoniae (PRSP)?

 

Short answer: No! Although cefpodoxime is also a 3rd generation cephalosporin, its invitro activity against PRSP is not comparable to that of ceftriaxone.  In a study of 21,605 strains of S. pneumoniae collected internationally, whereas 89.1% of PRSP isolates were susceptible to ceftriaxone, only 35% were susceptible to cefpodoxime (1).  Among isolates resistant to penicillin and erythromycin, the susceptibility to ceftriaxone was 86.9% compared to that of 22.7% for cefpodoxime.

This information is important since 32%, and 17.6% of all S. pneumoniae isolates tested in this study  were either penicillin-resistant or penicillin- and erythromycin-resistant, respectively.  So, when it comes to the coverage of PRSP, there is no oral cephalosporin “equivalent” to ceftriaxone and that includes cefpodoxime.  In fact, the package insert of cefpodoxime states that cefpodoxime is active against S. pneumoniae “excluding penicillin-resistant strains” (2).

 

References

  1. Pottumarthy S. Fritsche TR, Jones RN. Comparative activity of oral and parenteral cephalosporins tested against multidrug-resistant Streptococcus pneumonia: report from SENTRY Antimicrobial Surveillance Program (1997-2003). Diag Microbiol Infect Dis 2005;51:147-150.
  2. http://www.accessdata.fda.gov/drugsatfda_docs/label/2007/050674s014,050675s017lbl.pdf; accessed June 20, 2016.
Is cefpodoxime an appropriate oral antibiotic substitute for ceftriaxone when treating patients with respiratory tract infections caused by penicillin-resistant Streptococcus pneumoniae (PRSP)?

What is the sensitivity of nose swabs in detecting methicillin-resistant Staphylococcus aureus (MRSA) pneumonia?

In MRSA pneumonia, the sensitivity of nasal swab PCR may vary from as low as 24.2% to 88% (1-3). A single center  study involving  patients with possible healthcare-associated pneumonia (HCAP) and a low clinical pulmonary infection score (CPIS) — for whom antibiotics may not be necessary anyway (4)—suggested that discontinuation of empiric vancomycin in patients without an adequate respiratory culture and a negative nose and throat culture may be reasonable (5).  However, a prospective study of ICU patients concluded that “clinicians cannot reliably use the results of initial negative MRSA nasal swab results to withhold empirical MRSA coverage from patients who otherwise are at risk for MRSA infection” (3).

Thus, there is currently insufficient data to support discontinuation of vancomycin based on a negative nasal screen alone, particularly in patients who may be at high risk of MRSA pneumonia.

 

References

  1. Rimawi RH, Ramsey KM, Shah KB, et al. Correlation between methicillin-resistant Staphylococcus aureus nasal sampling, and S. aureus pneumonia in the medical intensive care unit. Infect Control Hosp Epidemiol 2014;35:590-92.
  2. Dangerfield B, Chung A, Webb B, et al. Predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nasal swab PCR assay for MRSA pneumonia. Antimicrob Agents Chemother 2014;58:859-64.
  3. Sarikonda KV, Micek ST, Doherty JA, et al. Methicillin-resistant Staphylococcus aureus nasal colonization is a poor predictor of intensive care unit-acquired methicillin-resistant Staphylococcus aureus infections requiring antibiotic treatment. Crit Care Med 2010;38:1991-1995.
  4. Napolitano LM. Use of severity scoring and stratification factors in clinical trials of hospital-acquired and ventilator-associated pneumonia. Clin Infect Dis 2010;51:S67-S80.
  5. Boyce JM, Pop O-F, Abreu-Lanfranco O, et al. A trial of discontinuation of empiric vancomycin therapy in patients with suspected methicillin-resistant Staphylococcus aureus health care-associated pneumonia. Antimicrob Agents Chemother 2013;57:1163-1168.
What is the sensitivity of nose swabs in detecting methicillin-resistant Staphylococcus aureus (MRSA) pneumonia?

What complication of Behçet’s syndrome carries the highest mortality?

Behçet’s syndrome may cause life-threatening hemoptysis due to pulmonary artery aneurysms.1 In a cohort of 387  patients with such syndrome followed for over 20 years, massive hemoptysis was the leading cause of death, found most commonly early in the course of the disease among young men.2 Conversely, the one-year mortality of pulmonary artery aneurysm in Behçet’s may be greater than 50%.1 Behçet’s syndrome is the only vasculitic disease with a proclivity for large pulmonary vessels, while its less frequent pulmonary manifestations, such as fibrosis and thrombosis, overlap with other small vessel vasculitides.3 Beware that the initial presentation of pulmonary aneurysm rupture may be confused with that of pulmonary embolism, with potential for fatal complications from anticoagulation.1 CT angiogram should help in distinguishing the two conditions.

 

References 

  1. Uzun O, Akpolat T, Erkan L. Pulmonary vasculitis in behcet disease: a cumulative analysis. Chest. 2005;127(6):2243-2253.
  2. Kural-Seyahi E, Fresko I, Seyahi N, et al. The long-term mortality and morbidity of Behçet syndrome: a 2-decade outcome survey of 387 patients followed at a dedicated center. Medicine (Baltimore). 2003;82(1):60-76.
  3. Hamuryudan V, Er T, Seyahi E, et al. Pulmonary artery aneurysms in Behçet syndrome. Am J Med. 2004;117(11):867-870.

 

Contributed by Sam Slavin, Harvard Medical Student

What complication of Behçet’s syndrome carries the highest mortality?