Evaluation of Antibiotic Resistance of Strains Isolated in Bari, Southern Italy, in 2017-2018 by Phenotypic and Genotyping Methods.

antibiotic resistance is a constantly evolving process and local surveillance is warranted to guide clinicians in the choice of therapy. Antibiotic susceptibility testing was performed by E-test on 92 strains, and resistance to clarithromycin and levofloxacin was also evaluated using a commercially available genotyping method. In naïve patients the resistance to clarithromycin, levofloxacin, and metronidazole was 37.7%, 26.2%, and 16.4%, respectively, significantly lower than the percentage found in treated patients. Concomitant resistance to ≥2 antibiotics was also observed in naïve patients. The A2143G mutation of the 23S-rRNA gene was the most frequently detected, also in naïve patients. The highest minimum inhibitory concentration (MIC) value (256 mg/L) was associated with A2142 mutations in all the patients carrying them. For levofloxacin resistance a mutation in codon 87 was detected in 63.9% and in codon 91 in 36.1% of the strains, without significant differences in the patients groups. A mutation in codon 87 was associated with the highest MIC value (32 mg/L). In our area, a high prevalence of primary resistance was detected; these rates were higher in patients who had experienced failure of several courses of therapy. A better knowledge of the local epidemiology of resistance, and the genotypes responsible, will improve the eradication rates.