CRISPR-Cas9 is a promising technology for genome editing. Here we use Cas9 nuclease-induced double-strand break DNA (DSB) at the UROS locus to model and correct congenital erythropoietic porphyria. We demonstrate that homology-directed repair is rare compared with NHEJ pathway leading to on-target indels and causing unwanted dysfunctional protein. Moreover, we describe unexpected chromosomal truncations resulting from only one Cas9 nuclease-induced DSB in cell lines and primary cells by a p53-dependent mechanism. Altogether, these side effects may limit the promising perspectives of the CRISPR-Cas9 nuclease system for disease modeling and gene therapy. We show that the single nickase approach could be safer since it prevents on- and off-target indels and chromosomal truncations. These results demonstrate that the single nickase and not the nuclease approach is preferable, not only for modeling disease but also and more importantly for the safe management of future CRISPR-Cas9-mediated gene therapies.

Molecular methods applied to 2,855 strains of Campylobacter-like organisms received from a surveillance network of Campylobacter infections in France identified 29 Arcobacter butzleri infections. This species ranks fourth for Campylobacteraceae isolation and appears to have the same pathogenic potential as the other species in the genus.

Background: Erythromycin is the drug of choice to treat human campylobacteriosis. Campylobacter isolates exhibit two different phenotypes with regard to erythromycin resistance: high-level resistant strains (HLR) and low-level resistant strains (LLR). Objectives: To study the mechanisms of resistance of Campylobacter to erythromycin, its 6-O-methyl derivative clarithromycin and the ketolide telithromycin. Results: We observed a cross-resistance against these three molecules but in contrast, no cross-resistance to quinolones. Analyses of LLR showed no mutation on the 23S rDNA and the presence of a drug transport system, which can be inhibited by phenylalanine arginine β-naphthylamide (PAβN), an efflux-pump inhibitor. In contrast, no PAβN-sensitive drug transport was identified in HLR but we found mutations in the rDNA, which were responsible for decreased binding of telithromycin to purified ribosomes. We further showed that the CmeB efflux pump already described in Campylobacter is not involved in the PAβN-sensitive transport of telithromycin. Conclusions: Mutations in the ribosome confer high-level macrolide/ketolide resistance. Low-level resistance was mediated by an efflux mechanism which is sensitive to PAβN. This efflux pump was selective to macrolides/ketolide and was different from the previously described Campylobacter efflux pump.

We describe isolates from human Campylobacter infection in the French population and the isolates' antimicrobial drug resistance patterns since 1986 and compare the trends with those of isolates from broiler chickens and pigs from 1999 to 2004. Among 5,685 human Campylobacter isolates, 76.2% were C. jejuni, 17.2% C. coli, and 5.0% C. fetus. Resistance to nalidixic acid increased from 8.2% in 1990 to 26.3% in 2004 (p<10-3), and resistance to ampicillin was high over time. Nalidixic acid resistance was greater for C. coli (21.3%) than for C. jejuni (14.9%, p<10-3). C. jejuni resistance to ciprofloxacin in broilers decreased from 31.7% in 2002 to 9.0% in 2004 (p = 0.02). The patterns of resistance to quinolones and fluoroquinolones were similar between 1999 and 2004 in human and broiler isolates for C. jejuni. These results suggest a potential benefit of a regulation policy limiting use of antimicrobial drugs in food animals.

The nucleotide sequence of the gyrA gene of Arcobacter butzleri, Arcobacter cryaerophilus, Arcobacter cibarius, and Arcobacter skirrowii was determin

Background. To better document the risk factors for sporadic Campylobacter infection in France, we conducted a national case-control study from Septe