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Ph neutral anti-microbial peptide-based decontamination of samples enhances recovery in culture of low load Mycobacterium tuberculosis

T J Bull(1) T Munshi(1) C Cosgrove(1) A Bartolf(2) M Meninchini(2) L Rindi(2) S Esin(2) G Batoni(2) K Hilpert()

1:St. George's University of London; 2:University of Pisa

Culture confirmation of M.tuberculosis (MTB) remains the gold standard for diagnosis of Tuberculosis but is typically successful in only 60% of samples even though many patients remain infectious.

We evaluated replacing the NaCl decontamination (gold standard) protocol of samples, followed by MGIT culture, with a Ph neutral pan anti-microbial peptide-based sample decontamination procedure followed by MGIT culture supplemented with a D-enantiomer peptide MTB growth enhancer (Index test).

255 clinical specimens obtained from 145 patients with a possible or diagnosed Tuberculosis were split evenly and processed in parallel. The Index test was significantly (P<0.0001) superior to the gold standard, recovering 56 MTB positive cultures including 13 faeces vs 30 MTB positive cultures including 1 faeces. It increased the culture confirmation rate for diagnosed Tuberculosis patients by 10% and empirically treated patients by 14%. The Index method also decreased sample contamination rate by 12%, increased the sample positivity rate by 46%, sampling test sensitivity by 19%, and provided a median decrease of 7.5 days in time to MGIT culture positivity (Ratio 0.6809 : 95% Cl 0.44 to 1.05).

We conclude that D-enantiomer antimicrobial peptide-based decontamination and culture provides increased sensitivity, rapidity and recovery of MTB, particularly from low load clinical samples, offering potential for improvement of culture confirmation during smear negative respiratory and faecal sampling.

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