Huiming Jin

Serovars and antimicrobial resistance of non-typhoidal Salmonella from human patients in Shanghai, China, 2006-2010.

We conducted a retrospective study on non-typhoidal Salmonella isolates from patients with diarrhoea in Shanghai, China, 2006-2010. A total of 1484 isolates of 70 Salmonella serovars were recovered from about 18 000 stool specimens. Serovars Enteritidis and Typhimurium were the most prevalent with isolation rates of 27.6% and 25.5%, respectively. The majority (1151, 77.6%) of the isolates were resistant to at least one antimicrobial, and 598 (40.3%) to more than three antimicrobials. Approximately half (50.9%) of the isolates were resistant to nalidixic acid and other resistance rates were sulfisoxazole (47.9%), streptomycin (37.6%), ampicillin (31.3%) and tetracycline (30.5%). Co-resistance to fluoroquinolones and the third- and fourth-generation cephalosporins was also identified.

Antimicrobial resistance of Shigella spp. from humans in Shanghai, China, 2004-2011.

A retrospective study conducted on patients with diarrhea in Shanghai, China from 2004-2011, indicated that of 77,600 samples collected, 1,635 (2.1%) tested positive for Shigella. Species isolated included S. sonnei (1,066, 65.1%), S. flexneri (569, 34.7%), and S. boydii (3, 0.2%). Most of the Shigella isolates were found to be resistant to streptomycin (98.7%), trimethoprim (98.0%), ampicillin (92.1%), and nalidixic acid (91.7%). Additionally, many isolates were resistant to tetracycline (86.9%), trimethoprim + sulfamethoxazole (80.1%), sulfisoxazole (76.8%) and gentamicin (55.5%). Approximately 80% of the isolates were resistant to at least eight antimicrobial agents, 14% to at least ten antimicrobials tested and 10 isolates to fourteen antimicrobials, including sulfonamides, fluoroquinolones, tetracyclines, aminoglycosides and β-lactamases. Importantly, co-resistance to fluoroquinolones and the third- and fourth-generation cephalosporins was also identified. The high levels of resistance to antimicrobial agents commonly used in clinical medicine presents a great challenge to treating patients with shigellosis.

Shift in serotype distribution of Shigella species in China, 2003–2013

We identified 2912 Shigella isolates from diarrhoeal patients in China during 2003-2013. The most common species was Shigella flexneri (55.3%), followed by Shigella sonnei (44.1%); however, S. sonnei is becoming increasingly prevalent. Among the S. flexneri isolates, serotypes 2a and X variant (-:7,8, E1037) were the two most prevalent serotypes, and serologically atypical isolates were also commonly identified. Overall, S. sonnei, S. flexneri 2a and S. flexneri X variant (-:7,8, E1037) accounted for 76.1% of all Shigella isolates, and their prevalence increased from 54.0% during 2003-2004 to 84.1% during 2011-2013. A change was observed in the serotype distribution of Shigella in China during this period, and we propose an ideal strategy to inform the development of a broadly effective Shigella vaccine candidate.

Multidrug- Resistant Atypical Variants of Shigella flexneri in China

We identified 3 atypical Shigella flexneri varieties in China, including 92 strains with multidrug resistance, distinct pulse types, and a novel sequence type. Atypical varieties were prevalent mainly in developed regions, and 1 variant has become the dominant Shigella spp. serotype in China. Improved surveillance will help guide the prevention and control of shigellosis.

Emergence of resistance to fluoroquinolones and third-generation cephalosporins in Shigella flexneri subserotype 1c isolates from China

We report here on the first identification of Shigella flexneri subserotype 1c in China. We also report the emergence of resistance to ciprofloxacin and third-generation cephalosporins in this subserotype 1c for the first time. Isolates of seven strains circulating in China yielded three new sequence types and seven pulsed-field gel electrophoresis patterns, thus demonstrating the existence of high genetic diversity within the isolates. Overall, the seven isolates showed reduced susceptibility to ciprofloxacin; one isolate was ciprofloxacin resistant, whilst another developed resistance to ciprofloxacin, norfloxacin, cefotaxime and ceftriaxone.

Laboratory monitoring of bacterial gastroenteric pathogens Salmonella and Shigella in Shanghai, China 2006-2012.

In 2006 we initiated an enhanced laboratory-based surveillance of Salmonella and Shigella infections in Shanghai, China. A total of 4483 Salmonella and 2226 Shigella isolates were recovered from stool specimens by 2012. In 80 identified Salmonella serovars, Enteritidis (34·5%) and Typhimurium (26·2%) were the most common. Shigella (S.) sonnei accounted for 63·9% of human Shigella infections over the same time period, and replaced S. flexneri to become the primary cause of shigellosis since 2010. Overall, a high level of antimicrobial resistance was observed in Salmonella and Shigella, particularly to nalidixic acid, ampicillin, and tetracycline. Ciprofloxacin resistance was common in Salmonella Typhimurium (21·0%) and S. flexneri (37·6%). The cephalosporin resistance in both pathogens also increased over the years, ranging from 3·4% to 7·0% in Salmonella, and from 10·4% to 28·6% in Shigella. Resistance to multiple antimicrobials was also identified in a large number of the isolates. This study provides insight into the distribution of Salmonella and Shigella in diarrhoeal diseases.

Molecular analysis and antimicrobial susceptibility of enterotoxigenic Escherichia coli from diarrheal patients.

A total of 123 enterotoxigenic Escherichia coli (ETEC) isolates from diarrheal patients from June to December 2012 in Shanghai, China, were examined to determine their genetic relatedness using multilocus sequence typing and pulsed-field gel electrophoresis (PFGE) and for the presence of virulence genes and antimicrobial susceptibility. Twenty-nine sequence types (STs) and 63 PFGE patterns were identified, and results from the 2 subtyping methods correlated well. The 12 isolates of PFGE cluster B all belonged to ST-2332 and were associated with nosocomial neonatal diarrhea. Isolates of a cluster usually had the same set of virulence factors, whereas isolates of different PFGE clusters carried diverse combinations of virulence determinants. Isolates belonging to ST-2332 and ST-182 (n=9) were resistant to at least 6 antimicrobials. Our findings highlighted the need of active surveillance programs for infectious diseases collecting data at both epidemiological and genetic levels that can detect high-risk lineages of pathogens in order to rapidly identify disease outbreaks.

Antimicrobial susceptibility, virulence gene profiles and molecular subtypes of Salmonella Newport isolated from humans and other sources.

Salmonella Newport (S. Newport) is a major serotype associated with human salmonellosis. A total of 79 S. Newport recovered from humans and other sources in China were characterized for antimicrobial susceptibility, virulence gene profiles and molecular subtypes using pulsed field gel electrophoresis (PFGE). Approximately 63.3% of the isolates were susceptible to all of 16 antimicrobials tested. Nearly one third of the isolates (31.6%) were resistant to sulfisoxazole, 20.3% to tetracycline and 13.9% to nalidixic acid. Twelve isolates (15.2%) were resistant to three or more antimicrobials. Among 10 virulence genes detected, Salmonella pathogenicity island genes avrA, ssaQ, mgtC, siiD, and sopB and fimbrial gene bcfC were present in most of the isolates (93.7% to 100%). Overall, we observed nine distinct virulence gene profiles, three of which (VP1, VP2 and VP3) were most common (86.1%). A total of 56 PFGE patterns were identified and mainly grouped into seven clusters (A to G) with 80% pattern similarity. Isolates from aquatic product shared a high similarity with those from humans in several clusters, highlighting a potential risk of aquatic product as a source of S. Newport that infect humans. Furthermore, there was a strong association between certain PFGE clusters and virulence gene profiles, suggesting virulence subtyping can be a useful epidemiological tool to discriminate S. Newport isolates.

Whole-Genome Sequences of 12 Clinical Strains of Listeria monocytogenes

ABSTRACT Listeria monocytogenes is a foodborne pathogen of global concern due to the high mortality rate among immunocompromised patients. Whole-genome sequences of 12 strains of L. monocytogenes from humans were reported. The availability of these genomes should provide useful information on the evolutionary history and genetic diversity of L. monocytogenes.

Whole-Genome Sequences of Four Salmonella enterica Serotype Newport Strains from Humans

ABSTRACT Salmonellosis contributes significantly to the public health burden globally. Salmonella enterica serotype Newport is among Salmonella serotypes most associated with food-borne illness in the United States and China. It was thought to be polyphyletic and to contain different lineages. We report draft genomes of four S. Newport strains isolated from humans in China.