Antibiogram-derived radial decision trees: Innovative visual educational tools for discussing empirical antibiotic selections


  • Paul P. Belliveau Pharmacy Practice, Massachusetts College of Pharmacy & Health Sciences-Worcester, 19 Foster Street, Worcester, MA 01608, USA
  • Rocco J. Perla Department of Clinical Microbiology and Infection Control, HealthAlliance Hospitals, 60 Hospital Road, Leominster, MA 01453, USA


Antibiogram, decision-trees, pedagogy, susceptibility


This article describes a unique visual pedagogical tool that displays appropriate empirical antimicrobial treatment choices for anticipated pathogens. This new tool, a probability-based radial decision tree (RDT), transforms data from a traditional hospital antibiogram into a format that can be used as an epidemiologic tool, a guide to empiric antimicrobial therapy and a robust educational tool for display of therapy options for pan-susceptible and drug-resistant isolates. As well-described resistance mechanisms serve the basis for the antimicrobial treatment choices in the RDT, use of this tool provides a means for both displaying treatment choices and explaining the rationale for such options in a logical and systematic manner. Teaching fellow pharmacists and pharmacy students with this tool provides both verbal and visual cues that may allow more efficient conveying of key concepts important to understanding options for treatment of select pathogens.


Akasaka, T., Tanaka, M., Yamaguchi, A., & Sato, K. (2001). Type II topoisomerase mutations in fluoroquinolone-resistant clinical strains of Pseudomonas aeruginosa isolated in 1998 and 1999: Role of target enzyme in mechanism of fluoroquinolone resistance. Antimicrobial Agents and Chemotherapy, 45, 2263 – 2268.

Akova, M., Yang, Y., & Livermore, D. M. (1990). Interactions of tazobactam and clavulanate with inducibly- and constitutively- expressed class I beta-lactamases. The Journal of Antimicrobial Chemotherapy, 25, 199–208.

American Thoracic Society, & Infectious Diseases Society of America (2005). Guidelines for the management of adults with hospital- acquired, ventilator-associated, and healthcare-associated pneumonia. American Journal of Respiratory and Critical Care Medicine, 171, 388–416.

Bryson, H. M., & Brogden, R. N. (1994). Piperacillin/tazobactam. A review of its antibacterial activity, pharmacokinetic properties and therapeutic potential. Drugs, 47, 506–535.

Burgess, D. S., & Nathisuwan, S. (2002). Cefepime, piperacillin/ta- zobactam, gentamicin, ciprofloxacin, and levofloxacin alone and in combination against Pseudomonas aeruginosa. Diagnostic

Microbiology and Infectious Disease, 44, 35–41.

Chambers, H. F. (1997). Methicillin resistance in staphylococci: Molecular and biochemical basis and clinical implications. Clinical Microbiology Reviews, 10, 781–791.

Chambers, H. F. (2001). The changing epidemiology of Staphylococcus aureus? Emerging Infectious Diseases, 7, 178–182.

Chambers, H. F. (2005). Community-associated MRSA—resistance and virulence converge. New England Journal of Medicine, 352, 1485–1487.

Chamot, E., El Amari, B. E., Rohner, P., & Van Delden, C. (2003). Effectiveness of combination antimicrobial therapy for Pseudo- monas aeruginosa bacteremia. Antimicrobial Agents and Che- motherapy, 47, 2756–2764.

Chatzinikolaou, I., Abi-Said, D., Bodey, G. P., Rolston, K. V. I., Tarrand, J. J., & Samonis, G. (2000). Recent experience with Pseudomonas aeruginosa bacteremia in patients with cancer. Archives of Internal Medicine, 160, 501–509.

Clinical Laboratory and Standards Institute/NCCLS. (2005a).

Analysis and Presentation Of Cumulative Antimicrobial Susceptibility Test Data; Approved Guideline-Second Edition. (CLSI/NCCLS document M39-A2). Wayne, PA: CLSI/NCCLS.

Clinical Laboratory and Standards Institute/NCCLS. (2005b).

Performance Standards For Antimicrobial Susceptibility Testing; Fifteenth Informational Supplement. (CLSI/NCCLS document M100-S15). Wayne, PA: CLSI/NCCLS.

Courvalin, P. (2005). Antimicrobial drug resistance: “Prediction is very difficult, especially about the future”. Emerging Infectious Diseases, 11, 1503–1506.

Diekema, D. J., Pfaller, M. A., Schmitz, F. J., Smayevsky, J., Bell, J., Jones, R. N. et al. (2001). Survey of infections due to Staphylococcus species: Frequency of occurrence and antimicro- bial susceptibility of isolates collected in the United States, Canada, Latin America, Europe, and the Western Pacific Region for the SENTRY Antimicrobial Surveillance Program, 1997– 1999. Clinical Infectious Diseases, 32(Suppl 2), S114–S132.

El Amin, N, Giske, C. G., Jalal, S., Keijser, B., Kronvall, G., & Wretlind, B. (2005). Carbapenem resistance mechanisms in Pseudomonas aeruginosa: Alterations of porin OprD and efflux proteins do not fully explain resistance patterns observed in clinical isolates. APMIS, 113, 187–196.

Friedland, I., Gallagher, G., King, T., & Woods, G. L. (2004). Antimicrobial susceptibility patterns in Pseudomonas aeruginosa: Data from a multicenter Intensive Care Unit Surveillance Study (ISS) in the United States. Journal of Chemotherapy, 16, 437 – 441.

Fung-Tomc, J., Huczko, E., Pearce, M., & Kessler, R. E. (1988). Frequency of in vitro resistance of Pseudomonas aeruginosa to cefepime, ceftazidime, and cefotaxime. Antimicrobial Agents and Chemotherapy, 32, 1443–1445.

Fung-Tomc, J., Dougherty, T. J., DeOrio, F. J., Simich-Jacobson, V., & Kessler, R. E. (1989). Activity of cefepime against ceftazidime- and cefotaxime-resistant gram-negative bacteria and its relationship to b-lactamase levels. Antimicrobial Agents and Chemotherapy, 33, 498–502.

Goldmann, D. A., Weinstein, R. A., Wenzel, R. P., Tablan, O. C., Duma, R. J., Gaynes, R. P. et al., (1996). Strategies to prevent and control the emergence and spread of antimicrobial-resistant microorganisms in hospitals. A challenge to hospital leadership. The Journal of the American Medical Association, 275, 234–240.

Hancock, R. E. W. (1998). Resistance mechanisms in Pseudomonas aeruginosa and other nonfermentative gram-negative bacteria. Clinical Infectious Diseases, 27(Suppl 1), S93–S99.

Hancock, R. E. W., & Bellido, F. (1992). Factors involved in the enhanced efficacy against Gram-negative bacteria of fourth generation cephalosporins. The Journal of Antimicrobial Che- motherapy, 29(Suppl A), 1–6.

Hilf, M., Yu, V. L., Sharp, J., Zuravleff, J. J., Korvick, J. A., & Muder, R. R. (1989). Antibiotic therapy for Pseudomonas aeruginosa bacteremia: Outcome correlations in a prospective study of 200 patients. The American Journal of Medicine, 87, 540 – 546.

Hughes, W. T., Armstrong, D., Bodey, G. P., Bow, E. J., Brown, A. E., Calandra, T. et al. (2002). Guidelines for the use of antimicrobial agents in neutropenic patients with cancer. Clinical Infectious Diseases, 34, 730–751.

Ibrahim, K. H., Gunderson, B., & Rotschafer, J. C. (2001). Intensive care unit antimicrobial resistance and the role of the pharmacist. Critical Care Medicine, 29(4 Suppl), N108–N113.

Isenberg, H. D., Alperstein, P., & France, K. (1999). In vitro activity of ciprofloxacin, levofloxacin, and trovafloxacin, alone and in combination with b-lactams, against clinical isolates of Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Burkholderia cepacia. Diagnostic Microbiology and Infectious Disease, 33, 81–86.

Jalal, S., & Wretlind, B. (1998). Mechanisms of quinolone resistance in clinical strains of Pseudomonas aeruginosa. Microbial Drug Resistance-Mechanisms Epidemiology & Disease, 4, 257–261.

Johnson, C. C., Livornese, L., Gold, M. J., Pitsakis, P. G., Taylor, S., & Levison, M. E. (1995). Activity of cefepime against ceftazidime-resistant gram-negative bacilli using low and high inocula. The Journal of Antimicrobial Chemotherapy, 35, 765–773.

Jones, R. N. (2003). Global epidemiology of antimicrobial resistance among community-acquired and nosocomial patho- gens: A five-year summary from the SENTRY antimicrobial surveillance program (1997–2001). Seminars in Respiratory and Critical Care Medicine, 24, 121–134.

Jones, R. N., Beach, M. L., & Pfaller, M. A. (2001). Spectrum and activity of three contemporary fluoroquinolones tested against Pseudomonas aeruginosa isolates from urinary tract infections in the SENTRY Antimicrobial Surveillance Program (Europe and the Americas; 2000): More alike than different!. Diagnostic Microbiology and Infectious Disease, 41, 161–163.

Kucers, A., Crowe, S. M., Grayson, M. L., & Hoy, J. F. (Eds.) (1997). The use of antibiotics. A clinical review of antibacterial, antifungal and antiviral drugs. Boston, MA: Butterworth- Heinemann.

Larson, E. L., Saiman, L., Haas, J., Neumann, A., Lowy, F. D., Fatato, B. et al. (2005). Perspectives on antimicrobial resistance: Establishing an interdisciplinary research approach. American Journal of Infection Control, 33, 410–418.

Lawton, R. M., Fridkin, S. K., Gaynes, R. P., & McGowan, J. E. (2000). Practices to improve antimicrobial use at 47 US hospitals: The status of the 1997 SHEA/IDSA position paper recommendations. Infection Control and Hospital Epidemiology, 21, 256–259.

Levy, S. B., & OBrien, T. F. (2005). Global antimicrobial resistance alerts and implications. Clinical Infectious Diseases, 41(Suppl 4), S219 – S220.

Limaye, A. P., Gautom, R. K., Black, D., & Fritsche, T. R. (1997). Rapid emergence of resistance to cefepime during treatment. Clinical Infectious Diseases, 25, 339–340.

Livermore, D. M. (1992). Interplay of impermeability and chromosomal b-lactamase activity in imipenem-resistant Pseu- domonas aeruginosa. Antimicrobial Agents and Chemotherapy, 36, 2046 – 2048.

Livermore, D. M. (1995a). b-Lactamases in laboratory and clinical medicine. Clinical Microbiology Reviews, 8, 557–584.

Livermore, D. M. (1995b). b-lactamases in laboratory and clinical resistance. Clinical Microbiology Reviews, 8, 557–584.

Livermore, D. M. (2001). Of Pseudomonas, porins, pumps, and carbapenems. The Journal of Antimicrobial Chemotherapy, 47, 247 – 250.

Livermore, D. M. (2002). Multiple mechanisms of antimicrobial resistance in Pseudomonas aeruginosa: Our worst nightmare? Clinical Infectious Diseases, 34, 634–640.

Livermore, D. M., & Yang, Y. J. (1987). Beta-lactamase lability and inducer power of newer beta-lactam antibiotics in relation to their activity against beta-lactamase-inducibility mutants of Pseudomonas aeruginosa. The Journal of Infectious Diseases, 155, 775 – 782.

Livermore, D. M., & Yang, Y. J. (1989). Comparative activity of meropenem against Pseudomonas aeruginosa strains with well- characterized resistance mechanisms. The Journal of Antimicro- bial Chemotherapy, 24(Suppl A), 149–159.

MacDougall, C., & Polk, R. E. (2005). Antimicrobial stewardship programs in healthcare systems. Clinical Micro- biology Reviews, 18, 638–656.

MacGowan, A. P., Wootton, M., & Holt, H. A. (1999). The antibacterial efficacy of levofloxacin and ciprofloxacin against Pseudomonas aeruginosa assessed by combining antibiotic exposure and bacterial susceptibility. The Journal of Antimicrobial Chemotherapy, 43, 345–349.

Masuda, N., Gotoh, N., Ishii, C., Sakagawa, E., Ohya, S., & Nishino, T. (1999). Interplay between chromosomal b-lacta- mase and the MexAB-OprM efflux system in intrinsic resistance to b-lactams in Pseudomonas aeruginosa. Antimicrobial Agents and Chemotherapy, 43, 400–402.

Mermel, L. A., Farr, B. M., Sherertz, R. J., Raad, I. I., OGrady, N., Harris, J. S. et al. (2001). Guidelines for the management of intravascular catheter-related infections. Clinical Infectious Dis- eases, 32, 1249–1272.

Micek, S. T., Lloyd, A. E., Ritchie, D. J., Reichley, R. M., Fraser, V. J., & Kollef, M. H. (2005). Pseudomonas aeruginosa blood stream infection: Importance of appropriate initial antibiotic treatment. Antimicrobial Agents and Chemotherapy, 49, 1306 – 1311.

Moellering, R. C., & Eliopoulos, G. M. (2005). Principles of anti- infective therapy. In G. L. Mandell, J. E. Bennett, & R. Dolin (Eds.), Principles and practice of infectious diseases, 6th ed. (pp. 242–253). Philadelphia, PA: Elsevier.

Moreillon, P., Que, Y-A., & Glauser, M. P. (2005). Staphylococcus aureus (including staphylococcal toxic shock). In G. L. Mandell, J. E. Bennett, & R. Dolin (Eds.), Principles and practice of infectious diseases, 6th ed. (pp. 2321 – 2351). Philadelphia, PA: Elsevier.

Mylonakis, E., & Calderwood, S. B. (2001). Infective endocarditis in adults. New England Journal of Medicine, 345, 1318–1329. Owens, R. C., Fraser, G. L., & Stogsdill, P. (2004). Antimicrobial stewardship programs as a means to optimize antimicrobial use. Pharmacotherapy, 24, 896–908.

Pai, H., Kim, J-W., Kim, J., Lee, J. H., Choe, K. W., & Gotoh, N.

(2001). Carbapenem resistance mechanisms in Pseudomonas aeruginosa clinical isolates. Antimicrobial Agents and Chemother- apy, 45, 480–484.

Paul, M., & Leibovici, L. (2005). Combination antibiotic therapy for Pseudomonas aeruginosa bacteraemia. The Lancet Infectious Diseases, 5, 192–193.

Peeters, M. J., & Sarria, J. C. (2005). Clinical characteristics of linezolid-resistant Staphylococcus aureus infections. The American Journal of Medical Sciences, 330, 102–104.

Pendland, S. L., Messick, C. R., & Jung, R. (2002). In vitro synergy testing of levofloxacin, ofloxacin, and ciprofloxacin in

combination with aztreonam, ceftazidime, or piperacillin against Pseudomonas aeruginosa. Diagnostic Microbiology and Infectious Disease, 42, 75–78.

Perla, R. J., & Belliveau, P. P. (2005). Antibiogram-derived radial decision trees: An innovative approach to susceptibility data display. American Journal of Infectious Diseases, 1, 124–127.

Pfaller, M. A., Jones, R. N., Marshall, S. A., Coffman, S. L., Hollis, R. J., Edmond, M. B. et al. (1997). Inducible amp C b-lactamase producing gram-negative bacilli from blood stream infections: Frequency, antimicrobial susceptibility, and molecular epide- miology in a national surveillance program (SCOPE). Diagnostic Microbiology and Infectious Disease, 28, 211–219.

Pier, G. B., & Ramphal, R. (2005). Pseudomonas aeruginosa. In G. L. Mandell, J. E. Bennett, & R. Dolin (Eds.), Principles and Practice of Infectious Diseases, 6th ed. (pp. 2587 – 2615). Philadelphia, PA: Elsevier.

Poole, K. (2005). Aminoglycoside resistance in Pseudomonas aeruginosa. Antimicrobial Agents and Chemotherapy, 49, 479–487.

Rapp, R. P. (2006). Pharmacy infectious diseases practice. Annals of Pharmacotherapy, 40, 304–306.

Rossolini, G. M., & Mantengoli, E. (2005). Treatment and control

of severe infections caused by multiresistant Pseudomonas

aeruginosa. Clinical Microbiology & Infection, 11(Suppl 4), 17–32.

Ruef, C. (2004). Epidemiology and clinical impact of glycopeptide

resistance in Staphylococcus aureus. Infection, 32, 315–327.

Safdar, N., Handelsman, J., & Maki, D. G. (2004). Does combination antimicrobial therapy reduce mortality in gram- negative bacteraemia? A meta-analysis. The Lancet Infectious

Diseases, 4, 519–527.

Sanders, C. C., Gates, M. L., & Sanders, W. E. (1988).

Heterogeneity of class I b-lactamase expression in clinical isolates of Pseudomonas aeruginosa. Antimicrobial Agents and Chemotherapy, 32, 1893–1895.

Shlaes, D. M., Gerding, D. N., John, J. F., Craig, W. A., Bornstein, D. L., Duncan, R. A. et al. (1997). Society for healthcare epidemiology of America and infectious diseases society of America joint Committee on the prevention of antimicrobial resistance: Guidelines for the prevention of antimicrobial resistance in hospitals. Clinical Infectious Diseases, 25, 584 – 599.

Siegman-Igra, Y., Ravona, R., Primerman, H., & Giladi, M. (1998). Pseudomonas aeruginosa bacteremia: An analysis of 123 episodes, with particular emphasis on the effect of antibiotic therapy. International Journal of Infectious Diseases, 2, 211–215.

Sobel, J. D., & Kaye, D. (2005). Urinary tract infections. In G. L. Mandell, J. E. Bennett, & R. Dolin (Eds.), Principles and practice of infectious diseases, 6th ed. (pp. 875–905). Philadelphia, PA: Elsevier.

Stapleton, P. D., & Taylor, P. W. (2002). Methicillin resistance in Staphylococcus aureus: Mechanisms and modulation. Science Progress, 85, 57–72.

Stevens, D. L., Bisno, A. L., Chambers, H. F., Everett, E. D., Dellinger, P., Goldstein, E. J. C. et al. (2005). Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clinical Infectious Diseases, 41, 1373–1406.

Wilson, P., Andrews, J. A., Charlesworth, R., Walesby, R., Singer, M., Farrell, D. J. et al. (2003). Linezolid resistance in clinical isolates of Staphylococcus aureus. The Journal of Antimicrobial Chemotherapy, 51, 186–188.

Yang, Y. J., & Livermore, D. M. (1989). Interactions of meropenem with class I chromosomal beta-lactamases. The Journal of Antimicrobial Chemotherapy, 24, 207–217.

Zapantis, A., Lace, M. K., Horvat, R. T., Grauer, D., Barnes, B. J., ONeal, B. et al. (2005). Nationwide antibiogram analysis using NCCLS M39-A guidelines. Journal of Clinical Microbiology, 43, 2629 – 2634.



Research Article