Marcus Ho Yin Wong

Chlorogenic Acid Exhibits Cholesterol Lowering and Fatty Liver Attenuating Properties by Up‐regulating the Gene Expression of PPAR‐α in Hypercholesterolemic Rats Induced with a High‐Cholesterol Diet

Hypercholesterolemia is a major risk factor for the development of cardiovascular disease and nonalcoholic fatty liver disease. Natural compounds have been proved to be useful in lowering serum cholesterol to slow down the progression of cardiovascular disease and nonalcoholic fatty liver disease. In the present study, the hypocholesterolemic and hepatoprotective effects of the dietary consumption of chlorogenic acid were investigated by monitoring plasma lipid profile (total cholesterol, triglycerides, high‐density lipoprotein and low‐density lipoprotein) in Sprague–Dawley rats fed with a normal diet, a high‐cholesterol diet or a high‐cholesterol diet supplemented with chlorogenic acid (1 or 10 mg/kg/day p.o.) for 28 days. Chlorogenic acid markedly altered the increased plasma total cholesterol and low‐density lipoprotein but decreased high‐density lipoprotein induced by a hypercholesterolemic diet with a dose‐dependent improvement on both atherogenic index and cardiac risk factor. Lipid depositions in liver were attenuated significantly in hypercholesterolemic animals supplemented with chlorogenic acid. It is postulated that hypocholesterolemic effect is the primary beneficial effect given by chlorogenic acid, which leads to other secondary beneficial effects such as atheroscleroprotective, cardioprotective and hepatoprotective functions. The hypocholesterolemic functions of chlorogenic acid are probably due to the increase in fatty acids unitization in liver via the up‐regulation of peroxisome proliferation‐activated receptor α mRNA. Copyright

Emergence of Clinical Salmonella enterica Serovar Typhimurium Isolates with Concurrent Resistance to Ciprofloxacin, Ceftriaxone, and Azithromycin

ABSTRACT Salmonella infection is an important public health issue for which the needs of antimicrobial treatment are increasing. A total of 546 human clinical S. enterica serovar Typhimurium isolates were recovered from patients in hospitals in China during the period of 2005 to ∼2011. Twenty percent of the isolates exhibited resistance to ciprofloxacin, and 4% were resistant to ceftriaxone. Importantly, for the first time, 12 (2%) S. Typhimurium isolates resistant to both ciprofloxacin and ceftriaxone were recovered; among these 12 isolates, two were also resistant to azithromycin, and one was resistant to all other drugs tested. The combined effects of various transferrable extended-spectrum β-lactamase determinants and a novel efflux-based ciprofloxacin resistance mechanism encoded by the mobile efflux gene oqxAB were responsible for the emergence of these extremely (highly) drug-resistant (XDR) S. Typhimurium isolates. The dissemination of resistance genes, such as those encoding ESBLs and the OqxAB pump, among Salmonella organisms will speed up the selection of XDR Salmonella, posing a huge threat to public health and Salmonella infection control.

PMQR genes oqxAB and aac(6′)Ib-cr accelerate the development of fluoroquinolone resistance in Salmonella typhimurium

Emergence of multidrug-resistant Salmonella typhimurium strains, especially the ACSSuT and nalidixic acid R types, has significantly compromised the effectiveness of current strategies to control Salmonella infections, resulting in increased morbidity and mortality. Clinical S. typhimurium isolates recovered in Hong Kong during the period of 2005–2011 were increasingly resistant to ciprofloxacin (CIP) and antibiotics of the ACSSuT group. Our data revealed that oqxAB and aac(6′)Ib-cr were encoded on plasmids of various sizes and the presence of these two elements together with a single gyrA mutation in S. typhimurium were sufficient to mediate resistance to CIP. Acquisition of the oqxAB and aac(6′)Ib-cr encoding plasmids by S. typhimurium caused a fourfold increase in CIP minimal inhibitory concentration. Furthermore, the presence of oqxAB and aac(6′)Ib-cr in Salmonella dramatically increased the mutation prevention concentration of CIP which may due to mutational changes in the drug target genes. In conclusion, possession of oqxAB and aac(6′)Ib-cr encoding plasmid facilitate the selection of CIP resistant S. typhimurium, thereby causing a remarkable increase of CIP resistance among clinical Salmonella strains in Hong Kong.

First detection of oqxAB in Salmonella spp. isolated from food

ABSTRACT Food-borne salmonellosis is an important public health problem worldwide and the second leading cause of food-borne illnesses in Hong Kong. In this study, the prevalence and antimicrobial resistance of Salmonella in meat products in Hong Kong were determined. Interestingly, a plasmid-mediated quinolone resistance (PMQR) gene combination, oqxAB, which mediates resistance to nalidixic acid, chloramphenicol, and olaquindox, was for the first time detectable on the chromosomes of two Salmonella enterica serovar Derby isolates. Further surveillance of oqxAB in Salmonella will be needed.

Characterization of Extended-Spectrum-β-Lactamase-Producing Vibrio parahaemolyticus

Vibrio parahaemolyticus is a major causative agent of gastroenteritis, particularly in areas with high levels of seafood consumption, and it has recently become pandemic due to the emergence of the O3:K6 serotype ([12][1]). Tdh and Trh have been implicated as major virulence factors in the strains

Evolution and Dissemination of OqxAB-Like Efflux Pumps, an Emerging Quinolone Resistance Determinant among Members of Enterobacteriaceae

ABSTRACT The OqxAB efflux pump, a plasmid-mediated quinolone resistance (PMQR) determinant, has become increasingly prevalent among members of Enterobacteriaceae over the past decade. To investigate the evolution and dissemination routes of the oqxAB operon, we assessed the prevalence of oqxAB-like elements among various Gram-negative bacterial species and analyzed the genotypic and phenotypic characteristics of organisms harboring such elements. With a comprehensive genotyping approach, a chromosome-based oqxAB operon was detectable in all Klebsiella pneumoniae strains tested, including organisms isolated before the year 1984. Sequence and phylogenetic analyses confirmed that the oqxAB operon in K. pneumoniae isolates was genetically closest to their plasmid-borne counterparts recoverable only from Escherichia coli and Salmonella isolates collected from the year 2003 onward. Chromosomal elements with much lower sequence homology were also found among the Enterobacter spp. but not other Gram-negative species. Contrary to the quinolone resistance phenotypes which were consistently observable among organisms with oqxAB-harboring plasmids, chromosomal oqxAB elements generally did not confer quinolone resistance, except for K. pneumoniae strains, which exhibited a typical oqxAB-mediated phenotype characterized by cross-resistance to olaquindox, chloramphenicol, and the quinolones. Gene expression analysis illustrated that such phenotypes were due to elevated expression of the chromosomal oqxAB operon. Furthermore, transposition of the oqxAB operon from the bacterial chromosome to plasmids was found to result in a >80-fold increase in the level of expression of the OqxAB pump, confirming its status as the first constitutively expressed efflux system located in bacterial mobile elements.

Molecular characterisation of a multidrug resistance conjugative plasmid from Vibrio parahaemolyticus

Vibrio parahaemolyticus is a major causative agent of gastroenteritis and is the leading cause of food-borne illness in Hong Kong. Recent studies of resistance to extended-spectrum β-lactams and fluoroquinolones in V. parahaemolyticus have caused huge concern. This work reports the characterisation of a multidrug resistance conjugative plasmid in V. parahaemolyticus isolated from shrimp samples from Hong Kong. The plasmid is ca. 200 kb and carries multidrug resistance genes, including a novel plasmid-mediated quinolone resistance gene qnrVC6 surrounded by several known and novel insertion sequence (IS) elements, an extended-spectrum β-lactamase gene bla(PER-1) mediated by ISCR1, and a ca. 3-kb four-gene cassette (aacA3, catB2, dfrA1 and aadA1) class 1 integron. Transmission of this multidrug resistance conjugative plasmid among Vibrio spp. would compromise the effectiveness of Vibrio infection control and pose a huge threat to public health.

Expansion of Salmonella enterica Serovar Typhimurium ST34 Clone Carrying Multiple Resistance Determinants in China

Nontyphoidal salmonellae are among the principal bacterial pathogens implicated in cases of food-borne gastroenteritis worldwide ([1][1]). Multidrug resistance, including ampicillin, chloramphenicol, streptomycin, sulbactam, and tetracycline (ACSSuT) resistance and ciprofloxacin or ceftriaxone

Characterization of Salmonella food isolates with concurrent resistance to ceftriaxone and ciprofloxacin.

Foodborne salmonellosis is an important public health problem worldwide. Most human Salmonella infections occur through the consumption of contaminated food of animal origin. The study reported the first isolation of two Salmonella enterica serovar Oranienburg strains from pork in China with concurrent resistance to ciprofloxacin and ceftriaxone. Both isolates also showed resistance to norfloxacin, trimethoprim-sulfamethoxazole, and chloramphenicol, and an elevated minimal inhibitory concentraton of azithromycin; one strain was also resistant to amikacin, gentamicin, tetracycline, and amoxicillin-clavulanic acid. Salmonella ceftriaxone resistance was due to the production of IncN plasmidborne CTX-M-14 ESBL, and their ciprofloxacin resistance was mediated by target mutations and efflux pump activity. This is the first time that ceftriaxone- and ciprofloxacin-resistant Salmonella was reported in meat products, which may be due to the uses of antibiotics in animal production. The study warrants the continuous surveillance of multidrug-resistant Salmonella in meat products and cautious use of antibiotics in food animals.

Characterization of Multidrug-Resistant Proteus mirabilis Isolated from Chicken Carcasses

This study investigated genotypic and phenotypic features of antimicrobial resistance of Proteus mirabilis isolated from chicken products. Resistance to a broad spectrum of antimicrobial agents was commonly observed in the test isolates: tetracycline (100%), sulfamethoxazole (80%), chloramphenicol (66%), nalidixic acid (66%), ampicillin (60%), streptomycin (56%), ciprofloxacin (52%), kanamycin (46%), gentamicin (38%), ceftriaxone (36%), cefotaxime (34%), ceftiofur (22%), and amoxicillin-clavulanic acid (16%). The β-lactamases TEM-1 and OXA-1, and extended-spectrum β-lactamases CTX-M-9 and CMY-2 were detected in β-lactam-resistant isolates. Single mutations in gyrA and parC were found to be contributing factors for fluoroquinolone resistance. Plasmid-mediated quinolone resistance (PMQR) genes qnrA and qnrD were detected in six fluoroquinolone-resistant isolates and a superintegron element, SXT, was detected in 14 out of 50 isolates. The high-level of antimicrobial resistance of P. mirabilis isolated from food products may pose a potential threat to public health.