Capsular polysaccharide and lipopolysaccharide O type analysis of Klebsiella pneumoniae isolates by genotype in China.

Klebsiella pneumoniae is a common pathogen associated with nosocomial infections and is characterised serologically by capsular polysaccharide (K) and lipopolysaccharide O antigens. We surveyed a total of 348 non-duplicate K. pneumoniae clinical isolates collected over a 1-year period in a tertiary care hospital, and determined their O and K serotypes by sequencing of the wbb Y and wzi gene loci, respectively. Isolates were also screened for antimicrobial resistance and hypervirulent phenotypes; 94 (27.0%) were identified as carbapenem-resistant (CRKP) and 110 (31.6%) as hypervirulent (hvKP). isolates fell into 58 K, and six O types, with 92.0% and 94.2% typeability, respectively. The predominant K types were K14K64 (16.38%), K1 (14.66%), K2 (8.05%) and K57 (5.46%), while O1 (46%), O2a (27.9%) and O3 (11.8%) were the most common. CRKP and hvKP strains had different serotype distributions with O2a:K14K64 (41.0%) being the most frequent among CRKP, and O1:K1 (26.4%) and O1:K2 (17.3%) among hvKP strains. Serotyping by gene sequencing proved to be a useful tool to inform the clinical epidemiology of K. pneumoniae infections and provides valuable data relevant to vaccine design.

[Antimicrobial resistance changes of carbapenem-resistant Enterobacteriaceae strains isolated from children].

Objective: To investigate the prevalence and resistance changes of carbapenem-resistant Enterobacteriaceae (CRE) strains isolated from children patients of Chinese Bacterial Resistance Surveillance Network (CHINET) from 2005 to 2017. Methods: Antimicrobial susceptibility testing was carried out by disk diffusion method (KB method) and automated systems. Results were analyzed according to the Clinical and Laboratory Standards Institute (CLSI) 2017 edition standards. Results: Among the 4 481 CRE clinical strains, the overall prevalence of CRE in children was 6.4%, including 8.8% in neonatal period, 7.3% in infancy, 3.8% in early childhood, 4.0% in preschool, 4.7% at school age and 7.4% of puberty. The CRE prevalence of citrobacter spp. remained stable in 2005-2017, whereas other bacteria showed an upward trend, which was higher than that of the adult group (P<0.01). Among the 4 481 CRE strains, there were 2 905 strains of Klebsiella spp. (64.8%), 813 strains of Escherichia coli (18.1%), 549 strains of Enterobacter spp.(12.3%), and 65 strains of Citrobacter spp.(1.5%). Among the 4 481 CRE strains, 20.7%, 13.3%, and 11.8% were from the intensive care unit (ICU), neonatal department and internal medicine wards, respectively. Specimens were distributed as respiratory (42.8%), urine (26.3%), and blood (14.9%). The results of antimicrobial susceptibility testing exhibited that the CRE strains were highly resistant to most commonly used antimicrobial agents in clinical practice, such as imipenem, meropenem and ertapenem, as well as penicillins and cephalosporins, etc. Conclusion: The prevalence of CRE strains in children is increasing year by year, and their antimicrobial resistance to common antibacterial agents in clinical practice is extremely serious, to which serious attention needs to be paid. According to the results of antimicrobial susceptibility testings, the antibacterial agents should be rationally selected to effectively control the spread of CRE.

Resistance trends among clinical isolates in China reported from CHINET surveillance of bacterial resistance, 2005-2014.

With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22,774 and 84,572 annually. Rates of extended-spectrum ß-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.

Diversity of human leukocyte antigen-B27 alleles in Han population of Hunan province, southern China.

This study was to investigate the frequency of HLA-B27 and its subtypes in the Han population of Hunan province, southern China. One hundred and sixty-nine healthy unrelated donors were tested for HLA-B27 by polymerase chain reaction-sequence-specific primer (PCR-SSP). One hundred and twenty-eight B27-positive spondyloarthropathy patients and 18 B27-positive healthy controls were subtyped using the high-resolution PCR-SSP. The phenotype frequency of human leukocyte antigen (HLA)-B27 was found to be 2.36% in healthy population. Five B27 alleles were identified: B*2704, B*2705, B*2706, B*2707, and B*2724. No significant difference was found in the distribution of HLA-B27 subtypes between the patients and controls studied. Notably, B*2724 was observed in a juvenile patient with ankylosing spondylitis. This subtype has not been previously reported in Chinese ankylosing spondylitis (AS) patients and other ethnic groups.

Biocidal activity in plant pathogenic Acidovorax, Burkholderia, Herbaspirillum, Ralstonia and Xanthomonas spp.

Antibacterial and antifungal activity was investigated for strains of Acidovorax spp., Burkholderia spp., Herbaspirillum rubrisubalbicans and Ralstonia solanacearum; strains representing 118 species and pathovars of Xanthomonas were also tested for phytotoxic capacity. Antibacterial activity was present in all Burkholderia spp. except B. andropogonis, in biovars II and III of R. solanacearum but not in biovars I and IV, and in two strains of Xanthomonas. Little antibacterial activity was recorded for Acidovorax spp. Antifungal activity was expressed by most strains of A. avenae ssp. avenae and A. avenae ssp. cattleyae. Weak or variable antifungal reactions were given by strains of A. avenae ssp. citrulli and no activity was expressed by A. konjaci. Most strains of B. caryophylli, B. cepacia, B. gladioli pv. agaricicola, B. gladioli pv. alliicola, B. gladioli pv. gladioli, B. glumae and B. plantari produced extensive inhibition zones against Rhodotorula mucilaginosa. Strains of H. rubrisubalbicans and R. solanacearum gave negative, weak or variable reactions. Strains of Xanthomonas spp. exhibited no antifungal activity. In all cases antifungal activity was caused by a low molecular weight toxin. Three Xanthomonas strains exhibited phytotoxic activity. The ecological implications of these data are discussed.

Preliminary description of biocidal (syringomycin) activity in fluorescent plant pathogenic Pseudomonas species.

Strains representing the fluorescent plant pathogenic Pseudomonas spp., Ps. agarici, Ps. asplenii, Ps. avellanae, Ps. beteli, Ps. caricapapayae, Ps. cichorii, Ps. corrugata, Ps. ficuserectae, Ps. flectens, Ps. fuscovaginae, Ps. marginalis, Ps. meliae, Ps. savastanoi, Ps. syringae, Ps. tolaasii and Ps. viridiflava were tested for biocidal activity using Aspergillus niger as assay organism. Inhibitory behaviour was found in strains of Ps. asplenii, Ps. blatchfordae, Ps. cichorii, Ps. corrugata, Ps. fuscovaginae, Ps. marginalis, Ps. marginalis pv. pastinacea, Ps. syringae pv. syringae, Ps. syringae pv. aptata, Ps. syringae pv. atrofaciens, Ps. syringae pv. lapsa, Ps. tolaasii, and strains of a Pseudomonas sp. pathogenic to Actinidia, in the Ps. savastanoi genomic sp. Antifungal activity could be identified with the production of members of the syringomycin family of toxins by strains in Ps. syringae, Ps. asplenii and Ps. fuscovaginae. These toxin reactions support suggestions made elsewhere of the synonym of the latter two species. In a preliminary characterization using tests for stability to heat, protease, acid and alkaline treatments, unknown toxins consistent with syringomycin-like toxins the strains from Actinidia species. The toxins from Ps. cichorii and from Ps. corrugata differed in their reactions from all other agents. Pseudomonas tolaasii produces the antifungal compound tolaasin. The white line reaction with Ps. reactions, a test for tolaasin production by strains of Ps. tolaasii, was confirmed as specific for this compound. Some of these low molecular weight toxins may be produced by some of these plant pathogenic strains.

Surveillance of bacterial resistance among isolates in Shanghai in 1999.

We report here surveillance data on the bacterial resistance of clinical isolates from 11 Shanghai hospitals in 1999, for guidance in the clinical use of antibacterial agents. Of the 14,855 strains collected, 5130 (34.5%) were Gram-positive cocci and 9725 (65.5%) were Gram-negative bacilli. The most common organisms in descending order of frequency, were: Escherichia coli (16%), coagulase-negative staphylococci (CNS; 14.3%), Klebsiella spp. (12.3%), Staphylococcus aureus (11.5%), Pseudomonas aeruginosa (9.2%), Acinetobacter spp. (8.1%), and Enterococcus spp. (6.6%). Methicillin-resistant strains accounted for 64% and 77% of S. aureus and CNS, respectively. The methicillin-sensitive strains were susceptible to most agents tested, while most methicillin-resistant strains were resistant to these agents. No vancomycin-resistant staphylococci were identified. Vancomycin-resistant strains accounted for 3.6% of Enterococcus fecalis and 1.7% of E. fecium. E. coli strains resistant to piperacillin, gentamicin, and fluoroquinolones accounted for 50% or more of the strains, and the resistance rates of Klebsiella spp., Enterobacter spp., Citrobacter spp., and Acinetobacter spp. to third-generation cephalosporins had increased markedly compared with rates in recent years. Resistance rates of P. aeruginosa to ceftazidime and imipenem (27% and 20%, respectively) had also increased compared with rates in recent years. A national strategy on the limited and prudent use of antibiotics is urgently needed.

Relationships within the Proteobacteria of plant pathogenic Acidovorax species and subspecies, Burkholderia species, and Herbaspirillum rubrisubalbicans by sequence analysis of 16S rDNA, numerical analysis and determinative tests.

Sequence data for 16S rDNA of the type strains of Acidovorax avenae subsp. avenae, A. avenae subsp. cattleyae, A. avenae subsp. citrulli, A. konjaci and Herbaspirillum rubrisubalbicans were compared with GenBank library accessions of Burkholderia spp., Comamonas sp., Ralstonia solanacearum and Variovorax sp. Maximum Parsimony analysis produced two clusters: 1. Acidovorax spp., Comamonas sp., and Variovorax sp. (all in the Comamonadaceae), and 2. Burkholderia spp., Ralstonia solanacearum, and Herbaspirillum rubrisubalbicans. Maximum Likelihood analysis produced only one cluster (of the Comamonadaceae). Using nutritional and laboratory tests, all Acidovorax spp., Burkholderia spp., and Herbaspirillum rubrisubalbicans were discriminated in distinct clusters at the species level, and could be identified by selected determinative tests. There were no phenotypic tests constituted as a circumscription of the genera and which permitted the allocation of strains to genera. Strain identification as species allowed allocation to genera only by inference. The nomenclatural implications of these data are discussed.