eThe in vitro activity of the novel antimicrobial peptide dendrimer G3KL was evaluated against 32 Acinetobacter baumannii (including 10 OXA-23, 7 OXA-24, and 11 OXA-58 carbapenemase producers) and 35 Pseudomonas aeruginosa (including 18 VIM and 3 IMP carbapenemase producers) strains and compared to the activities of standard antibiotics. Overall, both species collections showed MIC 50/90 values of 8/8 g/ml and minimum bactericidal concentrations at which 50% or 90% of strains tested are killed (MBC 50/90 ) of 8/8 g/ml. G3KL is a promising molecule with antibacterial activity against multidrug-resistant and extensively drug-resistant A. baumannii and P. aeruginosa isolates. The spread of Acinetobacter baumannii and Pseudomonas aeruginosa isolates that are resistant to carbapenem antibiotics due to the production of carbapenemases represents a serious threat (1). These strains are usually multidrug-resistant (MDR) due to the coexpression of mechanisms involving other classes of antibiotics, thus drastically limiting our therapeutic armamentarium (2-4). In particular, extensively drug-resistant (XDR) isolates are commonly detected worldwide (5), whereas the prevalence of pandrug-resistant (PDR) isolates is increasing worryingly in several countries (6-8). Therefore, novel antimicrobial strategies need to be rapidly developed.Recently, there has been a rising interest in evaluating naturally occurring or synthetic antimicrobial peptides (AMPs) with activity against prokaryotic membranes. This attention is due to their wide spectrum of activity against both Gram-positive and Gramnegative species, potent bactericidal activity, and ability to bypass common mechanisms of resistance that affect standard antibiotics (9, 10). However, several reasons have so far limited the clinical implementation of AMPs: (i) high susceptibility to degradation by endogenous and microbial proteases; (ii) toxicity due to the high concentration necessary to inhibit bacteria; and (iii) short half-life because of high protein binding (11). Several authors have modified AMPs to obtain proteolytically resistant versions, mostly by sequence variations and the use of D-amino acids (12-15). However, redesigning the peptide chain topology, in particular by introducing multiple branching points to obtain synthetic AMP dendrimers (AMPDs), seems a promising solution to overcome all of the the aforementioned problems (16-18).G3KL is a novel AMP dendrimer (AMPD) developed at the Department of Chemistry and Biochemistry of the University of Bern (Switzerland) by sequence optimization of an initial hit compound identified by screening a combinatorial library of dendrimers using a tailored high-throughput screening assay and presumed to act as a membrane-disrupting agent (19)(20)(21)(22). Its activity requires a dendritic topology and only natural lysine and leucine residues alternating in the branches (Fig. 1). This novel AMPD has demonstrated in vitro activity against several Gram-negative strains, low toxicity to human red blood cells (minimal hemolytic ...

We aimed to assess the intestinal colonization dynamics by multiple extended-spectrum cephalosporin-resistant Enterobacteriaceae (ESC-R-Ent) clones in Swiss travelers to India, a country with high prevalence of these multidrug-resistant pathogens. Fifteen healthy volunteers (HVs) colonized with ESC-R-Ent after traveling to India who provided stools before, after, and at 3- and 6-month follow-up are presented in this study. Stools were enriched in a LB broth containing 3 mg/L cefuroxime and plated in standard selective media (BLSE, ChromID ESBL, Supercarba) to detect carbapenem- and/or ESC-R-Ent. At least 5 Enterobacteriaceae colonies were analyzed for each stool provided. All strains underwent phenotypic tests (MICs in microdilution) and molecular typing to define bla genes (microarray, PCR/sequencing), clonality (MLST, rep-PCR), and plasmid content. While only three HVs were colonized before the trip, all participants had positive stools after returning, but the colonization rate decreased during the follow-up period (i.e., six HVs were still colonized at both 3 and 6 months). More importantly, polyclonal acquisition (median of 2 clones, range 1–5) was identified at return in all HVs. The majority of the Escherichia coli isolates belonged to phylogenetic groups A and B1 and to high diverse non-epidemic sequence types (STs); however, 15% of them belonged to clonal complex 10 and mainly possessed blaCTX−M−15 genes. F family plasmids were constantly found (~80%) in the recovered ESC-R-Ent. Our results indicate a possible polyclonal acquisition of the ESC-R-Ent via food-chain and/or through an environmental exposure. For some HVs, prolonged colonization in the follow-up period was observed due to clonal persistence or presence of the same plasmid replicon types in a new bacterial host. Travel medicine practitioners, clinicians, and clinical microbiologists who are facing the returning travelers and their samples for different reasons should be aware of this important phenomenon, so that better infection control measures, treatment strategies, and diagnostic tests can be adopted.

A rapid rt-PCR for detection of mcr-1 from stool specimens was developed. The detection rate was increased by testing selective broth enrichments. This approach also has the advantage of concomitant isolation of mcr-1-harboring strains for further antimicrobial susceptibility and genetic testing.

Resistance to antibiotics used against Neisseria gonorrhoeae infections is a major public health concern. Antimicrobial resistance (AMR) testing relies on time-consuming culture-based methods. Development of rapid molecular tests for detection of AMR determinants could provide valuable tools for surveillance and epidemiological studies and for informing individual case management. We developed a fast (<1.5-h) SYBR green-based real-time PCR method with high-resolution melting (HRM) analysis. One triplex and three duplex reactions included two sequences for N. gonorrhoeae identification and seven determinants of resistance to extended-spectrum cephalosporins (ESCs), azithromycin, ciprofloxacin, and spectinomycin. The method was validated by testing 39 previously fully characterized N. gonorrhoeae strains, 19 commensal Neisseria species strains, and an additional panel of 193 gonococcal isolates. Results were compared with results of culture-based AMR determination. The assay correctly identified N. gonorrhoeae and the presence or absence of the seven AMR determinants. There was some cross-reactivity with nongonococcal Neisseria species, and the detection limit was 10 3 to 10 4 genomic DNA (gDNA) copies/reaction. Overall, the platform accurately detected resistance to ciprofloxacin (sensitivity and specificity, 100%), ceftriaxone (sensitivity, 100%; specificity, 90%), cefixime (sensitivity, 92%; specificity, 94%), azithromycin (sensitivity and specificity, 100%), and spectinomycin (sensitivity and specificity, 100%). In conclusion, our methodology accurately detects mutations that generate resistance to antibiotics used to treat gonorrhea. Low assay sensitivity prevents direct diagnostic testing of clinical specimens, but this method can be used to screen collections of gonococcal isolates for AMR more quickly than current culture-based AMR testing. G onorrhea is the second most common bacterial sexually transmitted infection worldwide, with an estimated 78 million new cases in 2012 (1). Moreover, Neisseria gonorrhoeae has developed resistance to most current and past treatment options. Antimicrobial-resistant (AMR) gonorrhea is a major public health concern about which the World Health Organization (WHO) emphasizes the importance of global surveillance to identify emerging resistance, monitor trends, and inform revisions of treatment guidelines (2, 3).At a molecular level, the mechanisms that confer resistance to the most common treatment options have been well characterized. For instance, the acquisition of mosaic penA alleles, with or without substitutions at amino acid position 501 of the encoded penicillin-binding protein 2 (PBP2), has been linked to decreased susceptibility or resistance to the extended-spectrum cephalosporins (ESCs) cefixime (CFX) and ceftriaxone (CRO) (4, 5). In particular, strains harboring a mosaic pattern XXXIV penA gene, including the internationally spreading N. gonorrhoeae multiantigen sequence typing (NG-MAST) genogroup 1407, have been responsible for ESC treatment failures in severa...

Molecular methods are often used for Neisseria gonorrhoeae detection, but complete definition of antimicrobial resistance (AMR) patterns still requires phenotypic tests. We developed an assay that both identifies N. gonorrhoeae and detects AMR determinants in clinical specimens.