Search

Background: Introduction of Xpert® MTB/RIF assay has revolutionalised the diagnosis of tuberculosis (TB) by simultaneously detecting the bacteria and resistance to rifampicin (rif), a surrogate marker for multi-drug resistant TB (MDR-TB) as well as one of the principal first-line anti-tuberculosis drugs. In general, rpoB mutations can be found in 96.1% of rif-resistant Mycobacterium tuberculosis (MTB) strains worldwide and these mutations usually are located in a region at the 507-533rd amino acid residuals (81 bp) in the MTB rpoB gene, which is referred to as Rifampicin-resistance-determining region (RRDR). In this study, we determined the frequency of MDR-TB in Kampala using Xpert® MTB/RIF in comparison with the agar proportion method using Middlebrook 7H11 and further determined the frequency of probes for different rpoB gene mutations using Xpert® MTB/RIF assay in the 81 bp RRDR. Methods: A total of 1501 specimens received at Mycobacteriology laboratory, Makerere University for Xpert testing between May 2011 and May 2014 were analysed by Xpert® MTB/RIF assay. Specimens that were positive for both MTB and rifampicin resistance were further subjected to a complete first line anti-mycobacterial drug susceptibility testing using Middlebrook 7H11 agar proportion method (APM). Results: Xpert® MTB/RIF assay detected 313 MTB positive specimens and out of which 12 specimens had both MTB and rifampicin- resistance conferred by four different rpoB gene mutations in the 81 bp-RRDR of MTB, further one (1/12), specimen was found to be rifampicin mono-resistant on APM while the 11 were found to be MDR-TB. Probes associated with the observed rif-resistance were as follows: E (7/12), B (3/12), A (1/12), D (1/12) and no rif-resistance was associated with probe C. No specimen yielded rif-resistance associated with more than one probe failure (mutation combinations). Probe D was associated with rifampicin mono-resistant. Conclusions: MDR-TB was at 3.5% in the studied population. Mutations associated with Probe E (58%) also known as codons 531 and 533 are the commonest rpoB gene mutation identified by Xpert® MTB/RIF assay in this setting and mutations identified by probe E of the assay, turned out to be MDR-TB strains by agar proportion method antimicrobial susceptibility testing. No mutation was detected in the codon 522. [ABSTRACT FROM AUTHOR]

Background: Between January 2015 and July 2017, we investigated the frequency of carbapenem resistant Acinetobacter baumannii (CRAB) and carbapenem resistant Pseudomonas aeruginosa (CRPA) at the Mulago Hospital intensive care unit (ICU) in Kampala, Uganda. Carbapenemase production and carbapenemase gene carriage among CRAB and CRPA were determined; mobility potential of carbapenemase genes via horizontal gene transfer processes was also studied.Methods: Clinical specimens from 9269 patients were processed for isolation of CRAB and CRPA. Drug susceptibility testing was performed with the disk diffusion method. Carriage of carbapenemase genes and class 1 integrons was determined by PCR. Conjugation experiments that involved blaVIM positive CRAB/CRPA (donors) and sodium azide resistant Escherichia coli J53 (recipient) were performed.Results: The 9269 specimens processed yielded 1077 and 488 isolates of Acinetobacter baumannii and Pseudomonas aeruginosa, respectively. Of these, 2.7% (29/1077) and 7.4% (36/488) were confirmed to be CRAB and CRPA respectively, but 46 were available for analysis (21 CRAB and 25 CRPA). Majority of specimens yielding CRAB and CRPA were from the ICU (78%) while 20 and 2% were from the ENT (Ear Nose & Throat) Department and the Burns Unit, respectively. Carbapenemase assays performed with the MHT assay showed that 40 and 33% of CRPA and CRAB isolates respectively, were carbapenemase producers. Also, 72 and 48% of CRPA and CRAB isolates respectively, were metallo-beta-lactamase producers. All the carbapenemase producing isolates were multidrug resistant but susceptible to colistin. blaVIM was the most prevalent carbapenemase gene, and it was detected in all CRAB and CRPA isolates while blaOXA-23 and blaOXA-24 were detected in 29 and 24% of CRAB isolates, respectively. Co-carriage of blaOXA-23 and blaOXA-24 occurred in 14% of CRAB isolates. Moreover, 63% of the study isolates carried class 1 integrons; of these 31% successfully transferred blaVIM to E. coli J53.Conclusions: CRAB and CRPA prevalence at the Mulago Hospital ICU is relatively low but carbapenemase genes especially blaVIM and blaOXA-23 are prevalent among them. This requires strengthening of infection control practices to curb selection and transmission of these strains in the hospital. [ABSTRACT FROM AUTHOR]

Background: Introduction of Xpert® MTB/RIF assay has revolutionalised the diagnosis of tuberculosis (TB) by simultaneously detecting the bacteria and resistance to rifampicin (rif), a surrogate marker for multi-drug resistant TB (MDR-TB) as well as one of the principal first-line anti-tuberculosis drugs. In general, rpoB mutations can be found in 96.1% of rif-resistant Mycobacterium tuberculosis (MTB) strains worldwide and these mutations usually are located in a region at the 507-533rd amino acid residuals (81 bp) in the MTB rpoB gene, which is referred to as Rifampicin-resistance-determining region (RRDR). In this study, we determined the frequency of MDR-TB in Kampala using Xpert® MTB/RIF in comparison with the agar proportion method using Middlebrook 7H11and further determined the frequency of probes for different rpoB gene mutations using Xpert® MTB/RIF assay in the 81 bp RRDR.Methods: A total of 1501 specimens received at Mycobacteriology laboratory, Makerere University for Xpert testing between May 2011 and May 2014 were analysed by Xpert® MTB/RIF assay. Specimens that were positive for both MTB and rifampicin resistance were further subjected to a complete first line anti-mycobacterial drug susceptibility testing using Middlebrook 7H11 agar proportion method (APM).Results: Xpert® MTB/RIF assay detected 313 MTB positive specimens and out of which 12 specimens had both MTB and rifampicin- resistance conferred by four different rpoB gene mutations in the 81 bp-RRDR of MTB, further one (1/12), specimen was found to be rifampicin mono-resistant on APM while the 11 were found to be MDR-TB. Probes associated with the observed rif- resistance were as follows: E (7/12), B (3/12), A (1/12), D (1/12) and no rif-resistance was associated with probe C. No specimen yielded rif-resistance associated with more than one probe failure (mutation combinations). Probe D was associated with rifampicin mono-resistant.Conclusions: MDR-TB was at 3.5% in the studied population. Mutations associated with Probe E (58%) also known as codons 531and 533 are the commonest rpoB gene mutation identified by Xpert® MTB/RIF assay in this setting and mutations identified by probe E of the assay, turned out to be MDR-TB strains by agar proportion method antimicrobial susceptibility testing. No mutation was detected in the codon 522. [ABSTRACT FROM AUTHOR]