title: Application of quantitative second-line drug susceptibility testing at a multidrug-resistant tuberculosis hospital in Tanzania.
abstract: BACKGROUND
  Lack of rapid and reliable susceptibility testing for second-line drugs used in the treatment of multidrug-resistant tuberculosis (MDR-TB) may limit treatment success.
  
  
  METHODS
  Mycobacterium tuberculosis isolates from patients referred to Kibong'oto National TB Hospital in Tanzania for second-line TB treatment underwent confirmatory speciation and susceptibility testing. Minimum inhibitory concentration (MIC) testing on MYCOTB Sensititre plates was performed for all drugs available in the second-line formulary. We chose to categorize isolates as borderline susceptible if the MIC was at or one dilution lower than the resistance breakpoint. M. tuberculosis DNA was sequenced for resistance mutations in rpoB (rifampin), inhA (isoniazid, ethionamide), katG (isoniazid), embB (ethambutol), gyrA (fluoroquinolones), rrs (amikacin, kanamycin, capreomycin), eis (kanamycin) and pncA (pyrazinamide).
  
  
  RESULTS
  Of 22 isolates from patients referred for second-line TB treatment, 13 (59%) were MDR-TB and the remainder had other resistance patterns. MIC testing identified 3 (14%) isolates resistant to ethionamide and another 8 (36%) with borderline susceptibility. No isolate had ofloxacin resistance, but 10 (45%) were borderline susceptible. Amikacin was fully susceptible in 15 (68%) compared to only 11 (50%) for kanamycin. Resistance mutations were absent in gyrA, rrs or eis for all 13 isolates available for sequencing, but pncA mutation resultant in amino acid change or stop codon was present in 6 (46%). Ten (77%) of MDR-TB patients had at least one medication that could have logically been modified based on these results (median 2; maximum 4). The most common modifications were a change from ethioniamide to para-aminosalicylic acid, and the use of higher dose levofloxacin.
  
  
  CONCLUSIONS
  In Tanzania, quantitative second-line susceptibility testing could inform and alter MDR-TB management independent of drug-resistance mutations. Further operational studies are warranted.
authors.affiliation: Division of Infectious Diseases and International Health, University of Virginia, PO Box 801340, Charlottesville, Virginia 22908, USA. skh8r@virginia.edu.
authors.forename: Stellah G
authors.initials: SG
authors.lastname: Mpagama
authors.forename: Eric R
authors.initials: ER
authors.lastname: Houpt
authors.forename: Suzanne
authors.initials: S
authors.lastname: Stroup
authors.forename: Happiness
authors.initials: H
authors.lastname: Kumburu
authors.forename: Jean
authors.initials: J
authors.lastname: Gratz
authors.forename: Gibson S
authors.initials: GS
authors.lastname: Kibiki
authors.forename: Scott K
authors.initials: SK
authors.lastname: Heysell
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D013636:Tanzania; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy / Q000382:microbiology*; D055815:Young Adult
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins
references.citation: Antimicrob Agents Chemother. 2003 Dec;47(12):3799-805
references.pmid: 14638486
references.citation: J Clin Microbiol. 2012 Nov;50(11):3732-4
references.pmid: 22895034
references.citation: Diagn Microbiol Infect Dis. 2013 Jun;76(2):187-96
references.pmid: 23561273
references.citation: Am J Respir Crit Care Med. 2010 Sep 1;182(5):684-92
references.pmid: 20442432
references.citation: Eur J Clin Microbiol Infect Dis. 2012 May;31(5):835-9
references.pmid: 21866324
references.citation: Int J Tuberc Lung Dis. 2010 Mar;14(3):282-8
references.pmid: 20132618
references.citation: Antimicrob Agents Chemother. 2011 May;55(5):2032-41
references.pmid: 21300839
references.citation: Antimicrob Agents Chemother. 2008 Mar;52(3):852-7
references.pmid: 18070980
references.citation: Clin Infect Dis. 2012 Jul;55(2):178-9
references.pmid: 22467672
references.citation: Antimicrob Agents Chemother. 2004 Feb;48(2):596-601
references.pmid: 14742214
references.citation: PLoS One. 2013 May 13;8(5):e62034
references.pmid: 23675411
references.citation: PLoS Med. 2006 Jul;3(7):e241
references.pmid: 16796403
references.citation: Int J Tuberc Lung Dis. 2006 Jun;10(6):605-12
references.pmid: 16776446
references.citation: Antimicrob Agents Chemother. 2012 Jul;56(7):3857-63
references.pmid: 22564839
references.citation: J Clin Microbiol. 2006 Mar;44(3):688-92
references.pmid: 16517840
references.citation: Lancet Infect Dis. 2009 Mar;9(3):153-61
references.pmid: 19246019
references.citation: Expert Rev Mol Diagn. 2012 May;12(4):395-405
references.pmid: 22616704
references.citation: Am Rev Respir Dis. 1988 May;137(5):1217-22
references.pmid: 3195815
references.citation: Clin Infect Dis. 2010 Jul 1;51(1):6-14
references.pmid: 20504231
references.citation: Antimicrob Agents Chemother. 2000 Sep;44(9):2291-5
references.pmid: 10952570
references.citation: PLoS Med. 2006 Sep;3(9):e352
references.pmid: 16968123
references.citation: Lancet Infect Dis. 2010 Sep;10(9):621-9
references.pmid: 20797644
references.citation: Int J Tuberc Lung Dis. 2009 Nov;13(11):1355-9
references.pmid: 19861006
references.citation: Proc Natl Acad Sci U S A. 2000 Aug 15;97(17):9677-82
references.pmid: 10944230
references.citation: Drugs. 2002;62(15):2169-83
references.pmid: 12381217