Dados do Trabalho

Título

Borderline rpoB gene mutations are associated to rifampicin-monoresistant tuberculosis in São Paulo State

Objetivo (s)

To describe the frequency of mutations in the rpoB gene in Mycobacterium tuberculosis clinical
isolates received between December 2018 and December 2021 by Instituto Adolfo Lutz.

Material e Métodos

M. tuberculosis isolates from patients with criteria for drug susceptibility testing (DST) were
routinely subjected to GenoType MTBDRplus 2.0 (LPA), and those with inferred rpoB mutations
underwent rpoB Sanger sequencing and/or phenotypic DST (pDST) by MGIT 960 using isoniazid
(INH) at 0.1 µg/mL and rifampicin (RIF) at 0.5 or 1 µg/mL.

Resultados e Conclusão

In the study period, 15192 isolates were tested with LPA, of which 14335 (94.4%) gave wild-type
(WT) results for both isoniazid (INH) and rifampicin (RIF), 316 (2.1%) showed rpoB mutations only
(RIF-R), 296 (1.9%) showed katG and/or inhA mutations only (INH-R), and 245 (1.6%) showed rpoB
and katG and/or inhA mutations (MDR). Regarding the 316 RIF-R isolates, the most prevalent rpoB
mutations were inferred in WT7 probe (n=162, 51.3%), followed by inferred in WT2 (n=34, 10.8%)
and WT3 (n=29, 9.2%), and S531L mutation (n=27, 8.5%). The most frequent rpoB mutations in the
245 MDR isolates were S531L (n=158, 64.5%), inferred in WT7 (n=18, 7.3%) and WT8 (n=17, 6.9%),
and H526Y mutation (n=9, 3.7%). Overall, 82.6% (n=261/316) of the RIF-R isolates presented rpoB
inferred mutations alone, while only 20% (n=49/245) of the MDR isolates showed such mutations.
Among the 165 RIF-R isolates with inferred mutations sequenced, 95 had WT7 inferred mutations,
all with H526N borderline mutation and susceptible at 1 µg/mL of RIF. All of the 25 isolates
sequenced with WT2 inferred mutations presented L511P borderline mutation, 17 of which were
tested on MGIT and were RIF-susceptible, one at 0.5 µg/mL. Of the 22 isolates sequenced with
WT3 inferred mutations, 20 (90.9%) had F514F silent mutation and all the 17 tested by MGIT were
RIF-susceptible (3 with RIF at 0.5 µg/mL). The 2 other isolates presented double F514F mutation
and tested RIF-resistant on MGIT at 1 µg/mL. Overall, 117 RIF-R isolates with inferred mutations
underwent pDST, of which 107 (97.3%) tested susceptible on MGIT to both INH and RIF, 3 were
INH-R only (all with H526N mutation), 4 RIF-R (2 with double F514F, 1 with L533P and 1 with
S531W), and 3 were MDR (1 with Q490R+S531W mutations, 1 with Q513R, and 1 with Q513K).
In São Paulo State, RIF-monoresistant TB is caused predominantly by borderline rpoB mutations,
which are missed by pDST.

Palavras-chave

line probe assay, mutation, Mycobacterium tuberculosis, rifampicin, MDR-TB