1642. Antibiotic susceptibility pattern for Mycobacterium avium complex  in central Illinois
Session: Poster Abstract Session: Mycobacterial Infections
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
  • MAC.png (154.1 kB)
  • Background: It is difficult and challenging to treat Mycobacterium avium complex (MAC) infection.   Macrolide class such as azithromycin and clarithromycin serve as one of the first line drugs. Combination therapy is essential in treating MAC to maximize the effectiveness of the macrolides and to minimize the development of macrolide resistance. The purpose of this study was to assess the antibiotic susceptibility pattern for MAC in central Illinois.

    Methods: Minimal inhibitory concentration (MIC) of 88 MAC clinical isolates collected at health care facilities in central Illinois between February 2010 and October 2012  were determined by  broth microdilution method using the SLOMYCO panel (from TREK Diagnostic Systems, Cleveland, OH) for the following antibiotics:  clarithromycin, moxifloxacin, linezolid, rifabutin, rifampin, isoniazid, amikacin, ciprofloxacin, trimethoprim/sulfamethoxazole, streptomycin, ethambutol, doxycycline, and ethionamide.

    Results: Overall, 43.5% of MAC isolates collected were M. avium and the  rest were M. intracellulare. With CLSI breakpoints, all 88 MAC isolates were susceptibile to clarithromycin, whereas 54.5% (48/88) were susceptible to moxifloxacin and 39.7% (39/88) were susceptibile to linezolid. For the remainder of antibiotics without established breakpoints , the median MICs were as follows (in mcg/ml) :- rifabutin - <0.25, ethambutol - 4, isoniazid - 8, rifampin - 4, trimethoprim/sulfamethoxazole - 2/38, amikacin - 8, ciprofloxacin - 8, doxycycline - >32, streptomycin - 16 and ethionamide - 5.

    Conclusion: No clarithromycin resistance was observed and clarithromycin remains the cornerstone for treatment of MAC infection.  With increase in macrolide use, this needs to be monitored closely.  Rifabutin was more active compared to rifampin.

    Srivalli Vegi, MD1, Amardeep Shrestha, MD1, Burim Neziroski, MD1, Janak Koirala, MD1 and Shingo Chihara, MD1,2, (1)Southern Illinois University School of Medicine, Springfield, IL, (2)Internal Medicine, Southern Illinois University School of Medicine, Springfield, IL


    S. Vegi, None

    A. Shrestha, None

    B. Neziroski, None

    J. Koirala, None

    S. Chihara, None

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