Heterologous expression of MAB_0591 conferred rifampicin resistance to E. coli and M. tuberculosis Rifamycin MIC values were consistently lower for the M. abscessus Δarr mutant as compared with the M. abscessus ATCC 19977 parental type strain. The rifamycin WT phenotype was restored after complementation of the M. abscessus Δarr mutant with arr Further MIC data demonstrated that a C25 modification increases rifamycin activity in WT M. abscessus However, MIC studies in the M. abscessus Δarr mutant suggest that C25 modified rifamycins are still subject to modification by Arr_Mab CONCLUSIONS: Our findings identify Arr_Mab as the major innate rifamycin resistance determinant of M. abscessus. Our data also indicate that Arr_Mab-mediated rifamycin resistance in M. abscessus can only in part be overcome by C25 carbamate modification.

Background The resistance of Neisseria gonorrhoeae to ceftriaxone is unusual in Switzerland. The underlying genotype responsible for resistance is suspected to be novel. Generally, resistance in Neisseria gonorrhoeae (Ng) involves a comprehensive set of genes with many different mutations leading to resistance to different β-lactams and fluoroquinolones. Case presentation A patient had a positive result from specific PCR for Ng. We routinely culture all clinical specimens with a positive NG-PCR. In this particular case, we isolated a strain with resistance to ceftriaxone in Switzerland. A total of seven different genes (penA, ponA, porinB, mtr, gyrA, parC, 23S rRNA gene) in this strain were partially sequenced for comparison with phenotypic susceptibility testing. Interestingly, two different mutations in the porinB gene were observed, and data on this gene are limited. Information on the identified allele type of the penA gene is very limited as well. Three different mutations of parC and gyrA that correlate with ciprofloxacin resistance were found. The combination of ceftriaxone and ciprofloxacin resistance makes an appropriate treatment difficult to obtain due to multidrug resistance. Conclusion The combined results for all genes show the appearance of new mutations in central Europe either due to worldwide spread or the emergence of new genetic combinations of mutations.

Background: Resistance of Neisseria gonorrhoeae to ceftriaxone is very rare in Switzerland. The underlying genotype is suspected to be novel. Generally, resistance in Neisseria gonorrhoeae (Ng) involves a comprehensive set of genes with many different mutations causing resistance to different β-lactams and fluoroquinolones.Case presentation: A patient had a positive result with specific PCR for Ng. We routinely start culturing for all clinical specimens with a positive result with NG-PCR. In this particular case, we isolated such a strain with resistance to ceftriaxone in Switzerland. A total of 7 different genes in this strain were partially sequenced for comparison with phenotypic susceptibility testing. Interestingly, two different mutations in the porinB gene were observed, and data on this gene are limited. Information on the identified allele type of the penA gene is very limited as well. Three different mutations of parC and gyrA that correlate with ciprofloxacin resistance were found.Conclusion: The combined results for all genes show the appearance of new mutations in central Europe either due to worldwide spread or the emergence of new genetic combinations.