title: Comparison of Minocycline Susceptibility Testing Methods for Carbapenem-Resistant Acinetobacter baumannii.
abstract: Treatment options for infections due to carbapenem-resistant Acinetobacter baumannii are extremely limited. Minocycline is a semisynthetic tetracycline derivative with activity against this pathogen. This study compared susceptibility testing methods that are used in clinical microbiology laboratories (Etest, disk diffusion, and Sensititre broth microdilution methods) for testing of minocycline, tigecycline, and doxycycline against 107 carbapenem-resistant A. baumannii clinical isolates. Susceptibility rates determined with the standard broth microdilution method using cation-adjusted Mueller-Hinton (MH) broth were 77.6% for minocycline and 29% for doxycycline, and 92.5% of isolates had tigecycline MICs of ≤2 μg/ml. Using MH agar from BD and Oxoid, susceptibility rates determined with the Etest method were 67.3% and 52.3% for minocycline, 21.5% and 18.7% for doxycycline, and 71% and 29.9% for tigecycline, respectively. With the disk diffusion method using MH agar from BD and Oxoid, susceptibility rates were 82.2% and 72.9% for minocycline and 34.6% and 34.6% for doxycycline, respectively, and rates of MICs of ≤2 μg/ml were 46.7% and 23.4% for tigecycline. In comparison with the standard broth microdilution results, very major rates were low (∼2.8%) for all three drugs across the methods, but major error rates were higher (∼5.6%), especially with the Etest method. For minocycline, minor error rates ranged from 14% to 37.4%. For tigecycline, minor error rates ranged from 6.5% to 69.2%. The majority of minor errors were due to susceptible results being reported as intermediate. For minocycline susceptibility testing of carbapenem-resistant A. baumannii strains, very major errors are rare, but major and minor errors overcalling strains as intermediate or resistant occur frequently with susceptibility testing methods that are feasible in clinical laboratories.
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.|Department of Infectious Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Bowler
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Serena F
authors.initials: SF
authors.lastname: Kantz
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Roberta T
authors.initials: RT
authors.lastname: Mettus
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.|Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Christi L
authors.initials: CL
authors.lastname: McElheny
authors.affiliation: Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA yod4@pitt.edu.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Doi
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D004318:Doxycycline / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D000078304:Tigecycline
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D000078304:Tigecycline; D008911:Minocycline; D004318:Doxycycline