title: Association of slow recovery of Mycobacterium africanum-infected patients posttreatment with high content of Persister-Like bacilli in pretreatment sputum.
abstract: OBJECTIVE
  Mycobacterium africanum that causes 40% of tuberculosis (TB) in West Africa grows more slowly in culture and has similar transmission capacity compared with Mycobacterium tuberculosis, but M. africanum-exposed contacts progress more slowly to active disease. The presence of lipid body (LB) containing M. tuberculosis complex (MTBC) cells in sputum samples has been associated with mycobacterial transcriptomes indicating slow or no growth and persister-like antibiotic tolerance. Slow-growing bacilli have been found to display a persister-like phenotype with the accumulation of LBs and drug tolerance. Our previous study showed that the body mass index and lung damage resolution on chest X-ray were significantly improved slower in M. africanum-infected patients posttreatment than in M. tuberculosis-infected patients; however, the reason for this remains unclear. Therefore, we hypothesized that these differences could be either due to significant differences in drug resistance between the MTBC lineages or a difference in their content of persisters, as indicated by the percentage of LP-positive bacilli in sputum.
  
  
  METHODS
  Sputum isolates collected before treatment from patients with TB were subjected to drug susceptibility testing using the BD BACTEC MGIT 960 SIRE kit. The percentage of acid-fast bacilli (AFB) and LB-positive bacilli in pretreatment sputum was determined by a dual staining procedure using Auramine O and LipidTOX Red neutral lipid stain, respectively, and fluorescence microscopy imaging.
  
  
  RESULTS
  Out of the 77 isolates tested, 9 showed resistance to at least one drug and only 2 showed multidrug (rifampicin and isoniazid) resistance among M. tuberculosis-infected patients. The percentage of AFB-positive smears was similar between the two groups (p=0.821), whereas that of LP-positive bacilli was significantly higher (p=0.0059) in M. africanum-infected patients' sputa (n=24) than in M. tuberculosis-infected patients' sputa (n=36). In addition, the bacillary lengths were significantly higher in M. africanum-infected patients' sputa than in M. tuberculosis-infected patients' sputa (p=0.0007). A high frequency of LP-positive bacilli in pretreatment sputum was associated with a poor body mass index and lung damage on chest X-ray improvement following anti-TB treatment in both the groups (r2=0.022; p=0.017).
  
  
  CONCLUSIONS
  The slow clinical recovery of M. africanum-infected patients compared with M. tuberculosis-infected patients posttreatment may be at least partially associated with the persistence of drug-tolerant "fat and lazy" bacilli.
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia; Department of Biochemistry, University of Yaoundé I, Cameroon; Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom. Electronic address: ltientcheu@mrc.gm.
authors.forename: Leopold D
authors.initials: LD
authors.lastname: Tientcheu
authors.affiliation: Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: Andrew
authors.initials: A
authors.lastname: Bell
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia.
authors.forename: Oumie
authors.initials: O
authors.lastname: Secka
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia.
authors.forename: Abigail
authors.initials: A
authors.lastname: Ayorinde
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia.
authors.forename: Jacob
authors.initials: J
authors.lastname: Otu
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
authors.forename: Nathalie J
authors.initials: NJ
authors.lastname: Garton
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia.
authors.forename: Jayne S
authors.initials: JS
authors.lastname: Sutherland
authors.affiliation: World Health Organization Regional Office for Africa, Brazzaville, Congo.
authors.forename: Martin O
authors.initials: MO
authors.lastname: Ota
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia.
authors.forename: Martin
authors.initials: M
authors.lastname: Antonio
authors.affiliation: Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: H M
authors.initials: HM
authors.lastname: Dockrell
authors.affiliation: Vaccines and Immunity Theme, Medical Research Council Unit, Gambia.
authors.forename: Beate
authors.initials: B
authors.lastname: Kampmann
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, United Kingdom.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Barer
keywords: Drug tolerance; Lipid body; Mycobacterium africanum; Tuberculosis treatment