Since the discovery of qnrA in 1998, two additional qnr genes, qnrB and qnrS, have been described. These three plasmid-mediated genes contribute to quinolone resistance in gram-negative pathogens worldwide. A clinical strain of Proteus mirabilis was isolated from an outpatient with a urinary tract infection and was susceptible to most antimicrobials but resistant to ampicillin, sulfamethoxazole, and trimethoprim. Plasmid pHS10, harbored by this strain, was transferred to azide-resistant Escherichia coli J53 by conjugation. A transconjugant with pHS10 had low-level quinolone resistance but was negative by PCR for the known qnr genes, aac(6)-Ib-cr and qepA. The ciprofloxacin MIC for the clinical strain and a J53/pHS10 transconjugant was 0.25 g/ml, representing an increase of 32-fold relative to that for the recipient, J53. The plasmid was digested with HindIII, and a 4.4-kb DNA fragment containing the new gene was cloned into pUC18 and transformed into E. coli TOP10. Sequencing showed that the responsible 666-bp gene, designated qnrC, encoded a 221-amino-acid protein, QnrC, which shared 64%, 42%, 59%, and 43% amino acid identity with QnrA1, QnrB1, QnrS1, and QnrD, respectively. Upstream of qnrC there existed a new IS3 family insertion sequence, ISPmi1, which encoded a frameshifted transposase. qnrC could not be detected by PCR, however, in 2,020 strains of Enterobacteriaceae. A new quinolone resistance gene, qnrC, was thus characterized from plasmid pHS10 carried by a clinical isolate of P. mirabilis.Plasmid-mediated quinolone resistance was first described for a ciprofloxacin-resistant strain of Klebsiella pneumoniae in 1998 (15). The responsible gene, qnr (later named qnrA), was located on plasmid pMG252, which encodes multidrug resistance proteins. qnrB and qnrS were discovered in 2005 and 2006, respectively, and mediated similar levels of ciprofloxacin resistance (9, 11). Qnr proteins belong to the pentapeptide repeat protein (PRP) family and protect DNA gyrase and topoisomerase IV from quinolone inhibition (26,27,28). qnr genes show a high level of diversity; there are at least 6 qnrA, 20 qnrB, and 3 qnrS alleles reported, with one or more amino acid alterations within each family (12; http://www.lahey.org /qnrStudies). More recently, qnrD was found in Salmonella isolates (3). qnr genes are widely distributed in clinical Enterobacteriaceae isolates around the world and are usually associated with mobile elements (21). There were also qnr-like genes found on the chromosomes of Vibrio vulnificus, Vibrio parahaemolyticus, Photobacterium profundum, Stenotrophomonas maltophilia, and gram-positive genera such as Enterococcus, Listeria, Clostridium, and Bacillus (1,17,22,24). The wide distribution of qnr genes in different species of Enterobacteriaceae and their high degree of diversity raise the concern that there might be more qnr genes that have not yet been discovered. In this study, a new plasmid-mediated quinolone resistance gene, qnrC, was found on and cloned from a transferable plasmid, pHS10, in a clinical ...

This study was to estimate the prevalence and characteristics of Staphylococcus aureus from 1,850 retail meat and meat products in China during July 2011 to June 2016. The samples were collected covering most provincial capitals in China, including 604 raw meat, 601 quick-frozen meat, and 645 ready-to-eat meat. Using the qualitative and quantitative methods, all 39 cities had S. aureus-positive samples, and S. aureus was detected in 35.0% (647/1,850) of the samples. The levels of S. aureus in retail meat showed that the MPN value of the majority of the positive samples ranged from 0.3 to 100 MPN/g. Twenty-four antibiotics were used to test all 868 S. aureus isolates for antibiotic susceptibility. Only 11 isolates (1.26%) were susceptible to all antibiotics, whereas most isolates (821/868, 94.6%) showed resistance or intermediary resistance to more than three or more antibiotics. Of these strains, 104 (12.0%) were resistant to more than 10 antibiotics. However, the most frequent resistance was observed to ampicillin (85.4%), followed by penicillin (84.6%), erythromycin (52.7%), tetracycline (49.3%), kanamycin (45.3%), telithromycin (30.1%), clindamycin (29.6%), streptomycin (21.1%), norfloxacin (20.4%), gentamicin (19.4%), fusidic acid (18.4%), ciprofloxacin (16.9%), chloramphenicol (13.1%), amoxycillin/clavulanic acid (11.0%), and others (<10%). 7.4% of isolates (62/868) were confirmed as methicillin-resistance S. aureus (MRSA). By molecular typing analysis, there were 164 spa types and 111 STs were identified, including 15 novel spa types and 65 newly STs by multilocus sequence typing (MLST) and spa typing. Despite the wide genetic diversity observed among the 868 isolates, a great proportion of the population belonged to finite number of major clones: ST1-t127 (93/868, 10.7%) and ST7-t091 (92/868, 10.6%), ST5-t002 (42/868, 4.8%), ST398-t034 (40/868, 4.6%), ST188-t034 (38/868, 4.4%), ST59-t437 (30/868, 3.5%), ST6-t701 (29/868, 3.3%), and ST9-t899 (27/868, 3.1%) in China. This study reflects S. aureus was readily detected in Chinese retail meat and meat products but the level were not very excessive. In this study, the high antibiotic resistance is alarming and raising public health concern. In additions, most of molecular types of isolates have been linked to human infections around the world, indicating that these types of S. aureus in China have a theoretical pathogenic potential.

Bacillus cereus is a common and important food-borne pathogen that can be found in various food products. Due to low-temperature sterilization for a short period of time, pasteurization is not sufficient for complete elimination of B. cereus in milk, thereby cause severe economic loss and food safety problems. It is therefore of paramount importance to perform risk assessment of B. cereus in pasteurized milk. In this study, we isolated B. cereus from pasteurized milk samples in different regions of China, and evaluated the contamination situation, existence of virulence genes, antibiotic resistance profile and genetic polymorphism of B. cereus isolates. Intriguingly, 70 samples (27%) were found to be contaminated by B. cereus and the average contamination level was 111 MPN/g. The distribution of virulence genes was assessed toward 10 enterotoxigenic genes (hblA, hblC, hblD, nheA, nheB, nheC, cytK, entFM, bceT, and hlyII) and one emetic gene (cesB). Forty five percent strains harbored enterotoxigenic genes hblACD and 93% isolates contained nheABC gene cluster. The positive rate of cytK, entFM, bceT, hlyII, and cesB genes were 73, 96, 75, 54, and 5%, respectively. Antibiotic susceptibility assessment showed that most of the isolates were resistant to β-lactam antibiotics and rifampicin, but susceptible to other antibiotics such as ciprofloxacin, gentamicin and chloramphenicol. Total multidrug-resistant population was about 34%. In addition, B. cereus isolates in pasteurized milk showed a high genetic diversity. In conclusion, our findings provide the first reference on the prevalence, contamination level and characteristics of B. cereus isolated from pasteurized milk in China, suggesting a potential high risk of B. cereus to public health and dairy industry.

ABSTRACT Increasing data indicate that insects serve as major reservoirs and vectors of viruses, which account for the continuously increasing ecological burden and infectious disease outbreaks. Uncovering the hidden diversity of viruses in insects will further the understanding of the ecological and evolutionary perspectives in the emergence of insect-associated virus diseases. In this study, we queried transcriptome sequencing (RNA-Seq) data from more than 600 species across 32 insect orders dwelling in different ecological habitats and recovered more than 1,213 RNA viruses that were recapitulated in 40 families, 2 unclassified genera, and many unspecified viral groups. These novel viruses included the well-known insect-associated viruses within Flaviviridae, Picornavirales, Bunyavirales, Mononegavirales, Nidovirales, Reoviridae, and Negevirus. More appeared to form novel clusters within previously described taxa or could be resolved as paraphyletic, including the first astrovirus identified in insects, in which many were sufficiently divergent to warrant the establishment of new virus genera or families. Additionally, some viruses were closely related to the recognized plant-, fungus-, and vertebrate-specific species, implying the importance of relationships between insect behavior and virus spread. Comparative genome analyses also revealed high genomic variability with respect to the flexible gene pool and genome architecture of these newly described viruses, including the evidence for genome reshuffling first discovered in Dicistroviridae. The data reflecting the genetically and ecologically diverse viral populations in insects greatly expand our understanding of RNA viruses in nature and highlight that the biodiversity of RNA viruses remains largely unexplored. IMPORTANCE Insects comprise the largest proportion of animals on earth and are frequently implicated in the transmission of vector-borne diseases. However, considerable attention has been paid to the phytophagous and hematophagous insects, with results that provide insufficient and biased information about the viruses in insects. Here, we have delivered compelling evidence for the exceptional abundance and genetic diversity of RNA viruses in a wide range of insects. Novel viruses were found to cover major categories of RNA viruses, and many formed novel clusters divergent from the previously described taxa, dramatically broadening the range of known RNA viruses in insects. These newly characterized RNA viruses exhibited high levels of genomic plasticity in genome size, open reading frame (ORF) number, intergenic structure, and gene rearrangement and segmentation. This work provides comprehensive insight into the origin, spread, and evolution of RNA viruses. Of course, a large-scale virome project involving more organisms would provide more-detailed information about the virus infections in insects.