What changes should I consider in my treatment of hospitalized patients with community-acquired pneumonia (CAP) in light of the 2019 guidelines of the American Thoracic society (ATS) and Infectious Diseases Society of America (IDSA)?

Compared to 2007,1 the 2019 ATS/IDSA guidelines2 propose changes in at least 4 major areas of CAP treatment in inpatients, with 2 “Do’s” and 2 “Dont’s”:

  • Do select empiric antibiotics based on severity of CAP and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (see related pearl on P4P)
  • Do routinely treat CAP patients who test positive for influenza with standard CAP antibiotics
  • Don’t routinely provide anaerobic coverage in aspiration pneumonia (limit it to empyema and lung abscess) (see related pearl on P4P)
  • Don’t routinely treat CAP with adjunctive corticosteroids in the absence of refractory shock

β-lactam plus macrolide is recommended for both non-severe and severe CAP.  β-lactam plus respiratory fluoroquinolone is an alternative regime in severe CAP, though not endorsed as strongly as β-lactam plus macrolide therapy (low quality of evidence).  Management per CAP severity summarized below:

  • Non-severe CAP
    • β-lactam (eg, ceftriaxone, cefotaxime, ampicillin-sulbactam and newly-added ceftaroline) plus macrolide (eg, azithromycin, clarithromycin) OR respiratory fluoroquinolone (eg, levofloxacin, moxifloxacin)
    • In patients at risk of MRSA or P. aeruginosa infection (eg, prior isolation of respective pathogens, hospitalization and parenteral antibiotics in the last 90 days or locally validated risk factors—HCAP has been retired), obtain cultures/PCR
    • Hold off on MRSA or P. aeruginosa coverage unless culture/PCR results return positive.
  • Severe CAP
    • β-lactam plus macrolide OR β-lactam plus respiratory fluoroquinolone (see above)
    • In patients at risk of MRSA or P. aeruginosa infection (see above), obtain cultures/PCR
    • Add MRSA coverage (eg, vancomycin or linezolid) and/or P. aeruginosa coverage (eg, cefepime, ceftazidime, piperacillin-tazobactam, meropenem, imipenem) if deemed at risk (see above) while waiting for culture/PCR results

Duration of antibiotics is for a minimum of 5 days for commonly-targeted pathogens and a minimum of 7 days for MRSA or P. aeruginosa infections, irrespective of severity or rapidity in achieving clinical stability.

For patients who test positive for influenza and have CAP, standard antibacterial regimen should be routinely added to antiinfluenza treatment.

For patients suspected of aspiration pneumonia, anaerobic coverage (eg, clindamycin, ampicillin-sulbactam, piperacillin-tazobactam) is NOT routinely recommended in the absence of lung abscess or empyema.

Corticosteroids are NOT routinely recommended for non-severe (high quality of evidence) or severe (moderate quality of evidence) CAP in the absence of refractory septic shock.

Related pearls on P4P:

2019 CAP guidelines on diagnostics:                                        https://pearls4peers.com/2020/02/14/what-changes-should-i-consider-in-my-diagnostic-approach-to-hospitalized-patients-with-community-acquired-pneumonia-cap-in-light-of-the-2019-guidelines-of-the-american-thoracic-society-ats-and-inf/ 

Anerobic coverage of aspiration pneumonia: https://pearls4peers.com/2019/07/31/should-i-routinely-select-antibiotics-with-activity-against-anaerobes-in-my-patients-with-presumed-aspiration-pneumonia/


  1. Mandell LA, Wunderink RG, Anzueto A. Infectious Disease Society of America/American Thoracic Society Consensus Guidelines on the Management guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis 2007;44:S27-72. https://www.ncbi.nlm.nih.gov/pubmed/17278083
  2. Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. Am J Respir Crit Care Med 2019;200:e45-e67. https://www.ncbi.nlm.nih.gov/pubmed/31573350


What changes should I consider in my treatment of hospitalized patients with community-acquired pneumonia (CAP) in light of the 2019 guidelines of the American Thoracic society (ATS) and Infectious Diseases Society of America (IDSA)?

Is meropenem a good choice of antibiotic for treatment of my patient’s intraabdominal infection involving enterococci?

Although meropenem is a broad spectrum antibiotic that covers many gram-negative and gram-positive organisms as well as anaerobes, its activity against enterococci is generally poor and leaves much to be desired.

In a study of ampicillin-sensitive E. faecalis isolates from hospitalized patients, only 36% of isolates were considered susceptible (MIC≤4 mg/L); activity against E. faecium isolates was similarly poor.1 Several other studies have reported the suboptimal activity of meropenem against both E. faecalis and E. faecium, 2-4 with susceptibility rates as low as 8.6% depending on the MIC break point used.3

A popular textbook and a handbook on infectious diseases also do not recommend the use of meropenem for treatment of enterococcal infections. 5,6

Of interest, the package insert states that meropenem is indicated for complicated skin and soft tissue infections due to a variety of organisms, including E. faecalis (vancomycin-susceptible isolates only), but not for complicated intra-abdominal infections or meningitis due this organism.7

In our patient with intraabdominal infection,  we may consider piperacillin-tazobactam instead.  Piperacillin-tazobactam is a broad spectrum antibiotic with excellent coverage against anaerobes and ampicillin-susceptible E. faecalis.1,8  



  1. Endtz HP, van Dijk WC, Verbrugh HA, et al. Comparative in-vitro activity of meropenem against selected pathogens from hospitalized patients in the Netherlands. J Antimicrob Chemother 1997;39:149-56. https://www.ncbi.nlm.nih.gov/pubmed/9069534
  2. Pfaller MA, Jones RN. A review of the in vitro activity of meropenem and comparative antimicrobial agents tested against 30,254 aerobic and anaerobic pathogens isolated world wide. Diag Microbiol Infect Dis 1997;28:157-63. https://www.ncbi.nlm.nih.gov/pubmed/9327242
  3. Hallgren A, Abednazari H, Ekdahl C, et al. Antimicrobial susceptibility patterns of enterococci in intensive care units in Sweden evaluated by different MIC breakpoint systems. J Antimicrob Chemother 2001;48:53-62. https://www.ncbi.nlm.nih.gov/pubmed/11418512
  4. Hoban DJ, Jones RN, Yamane N, et al. In vitro activity of three carbapenem antibiotics comparative studies with biapenem (L-627), imipenem, and meropenem against aerobic pathogens isolated worldwide. Diag Microbiol Infect Dis 993;17:299-305.https://www.ncbi.nlm.nih.gov/pubmed/8112045
  5. Chambers HF. Carbapenem and monobactams. In Mandell GL et al. eds. Principles and practice of infectious diseases. 2010, pp 341-45.
  6. Cunha CB, Cunha BA. Antibiotic essentials. 2017, pp 689-91.
  7. Meropenem.http://online.lexi.com/lco/action/doc/retrieve/docid/patch_f/7253?searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3Dmeropenem%26t%3Dname
  8. Perry CM, Markham A. Piperacillin/tazobactam. Drugs 1999;57:805-43. https://link.springer.com/article/10.2165%2F00003495-199957050-00017

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Is meropenem a good choice of antibiotic for treatment of my patient’s intraabdominal infection involving enterococci?

Should I be concerned about piperacillin-tazobactam nephrotoxicity in the absence of vancomycin?

Nephrotoxicity associated with piperacillin-tazobactam (PT) combined with vancomycin (V) has been increasingly reported1,2,  with  some recommending that an alternative to V be used when PT is also on board 2. However, there are several reasons why the nephrotoxic potential of PT either alone or with antibiotics other than V also deserves further study before such recommendations can be widely embraced3.

First, most studies of VPT combination do not include comparative V or PT alone arms making it difficult to assess the relative contribution of these 2 antibiotics to kidney injury when used in combination. A small study that did include a PT-only  arm reported a similar rate of acute kidney injury (AKI) in PT and VPT arms ( 15.4% and 18.8% , respectively), both significantly higher that than of  V-only group (4%).4

 Other reasons not to readily dismiss PT as a cause of nephrototoxicity include the  lack of association between higher V trough levels and AKI in patients receiving VPT2, the association of PT with lower rates of renal function recovery in critically ill patients when compared to other selected β-lactams5,  and higher magnesium and potassium renal tubular loss with the use of PT compared to selected cephalosporins and ciprofloxacin6.  As with other penicillins, PT-associated acute interstitial nephritis may also occur7-8.

In short, even in the absence of V, nephrotoxic potential of PT should not be automatically dismissed.


Disclosure: Ref 3 was also authored by the creator of this pearl.


  1. Hammond DA, Smith MN, Chenghui Li, et al. Systematic review and meta-analysis of acute kidney injury associated with concomitant vancomycin and piperacillin/tazobactam. Clin Infect Dis 2017;64:666-74.
  2. Navalkele B, Pogue JM, Karino S, et al. Risk of acute kidney injury in patients on concomitant vancomycin and piperacillin-tazobactam compared to those on vancomycin and cefepime. Clin Infect Dis 2017;64:116-123.
  3. Manian FA. Should we revisit the nephrotoxic potential of piperacillin-tazobactam as well? Clin Infect Dis 2017; https://doi.org/10.1093/cid/cix321
  4. Kim T, Kandiah S, Patel M, et al. Risk factors for kidney injury during vancomycin and piperacillin/tazobactam administration, including increased odds of injury with combination therapy. BMC Res Notes 2015;8:579.
  5. Jensen J-U S, Hein L, Lundgren B, et al. Kidney failure related to broad-spectrum antibiotics in critically ill patients: secondary end point results from a 1200 patient randomized trial. BMJ Open 2012;2:e000635. http://bmjopen.bmj.com/content/2/2/e000635
  6. Polderman KH, Girbes ARJ. Piperacillin-induced magnesium and potassium loss in intensive care unit patients. Intensive Care Med 2002;28:530-522.
  7. Muriithi AK, Leung N, Valeri AM, et al. Clinical characteristics, causes and outcomes of acute interstitial nephritis in the elderly. Kidney International 2015;87:458-464.
  8. Soto J, Bosch JM, Alsar Ortiz MJ, et al. Piperacillin-induced acute interstitial nephritis. Nephron 1993;65:154-155. 
Should I be concerned about piperacillin-tazobactam nephrotoxicity in the absence of vancomycin?