Spectinomycin

BACKGROUND: Neisseria gonorrhoeae (N. gonorrhoeae) resistance to antimicrobial has been a major concern in China, and epidemiological data on N. gonorrhoeae resistance are not well understood. This meta-analysis was aimed at summarizing the evidence on N. gonorrhoeae resistance to penicillin, tetracycline, ciprofloxacin, ceftriaxone and spectinomycin in China.

Matrix effect (ME) is always a major issue for the development of LC-MS/MS method. ME resulting from co-eluting residual matrix components can affect the ionization efficiency of target analytes, leading to quantification errors of the analytes of interest. The present work evaluates MEs of milk samples on simultaneous analysis of four aminoglycosides residues via LC-ESI/MS/MS including streptomycin, dihydrostreptomycin, spectinomycin and kanamycin. Approaches to reduce MEs were examined: optimization of the sample preparation, sample dilution and lower flow rate used. Three commercial sorbents were tested including Oasis MCX, Oasis HLB and Oasis WCX. WCX behaved better for all analytes, but high MEs (80.8-134.9%) were obtained. Therefore, a consecutive SPE of tC18-WCX was found to effectively reduce ME. Milk samples from different manufacturers were analyzed and low MEs (85.6-112.9%) were obtained.

Analysis of bacterial gene function commonly relies on gene disruption or replacement followed by phenotypic characterization of resulting mutant strains. Deletion or replacement of targeted regions is commonly achieved via two homologous recombination (HR) events between the bacterial genome and a non-replicating plasmid carrying DNA fragments flanking the region to be deleted. Counterselection of clones that have integrated the entire plasmid in their genome via a single HR is crucial in this procedure. Various genetic tools and well established protocols are available for this type of mutagenesis in model bacteria, however, these methods are not always efficiently applicable in less established systems. Here we describe the construction and application of versatile plasmid vectors, pREDSIX and pTETSIX, for marker replacement and markerless mutagenesis, respectively. Apart from an array of restriction sites optimized for cloning GC-rich DNA fragments, the vector backbone contains a constitutively expressed gene for mCherry enabling rapid identification of clones originating from single or double HR events by fluorescence-assisted cell sorting (FACS).

We describe development and validation of a high-throughput screen (HTS) for identifying small molecules that restore the efficacy of carbapenems (adjunctives) and/or directly inhibit growth of carbapenem-resistant Enterobacteriaceae (CRE). Our HTS assay is based on a screen-counterscreen approach using a representative multidrug-resistant CRE strain, Klebsiella pneumoniae BIDMC12A. Specifically, we tested the ability of small molecules to inhibit bacterial growth in the presence (screen) or absence (counterscreen) of meropenem, a representative carbapenem antibiotic. Primary screening of 11,698 known bioactive compounds identified 14 with adjunctive activity and 79 with direct antimicrobial effect. Secondary screening identified triclosan as a strongly synergistic meropenem adjunctive (fractional inhibitory concentration = 0.48) and confirmed azidothymidine (AZT) (minimal inhibitory concentration [MIC] = 4 μg mL-1), NH125 (MIC = 4 μg mL-1), diphenyleneiodonium chloride (MIC = 8 μg mL-1), and spectinomycin (MIC = 32 μg mL-1) as potent direct antimicrobials.