Carbapenem-resistant Klebsiella pneumoniae capsular types, antibiotic resistance and virulence factors in China: a longitudinal, multi-centre study.

Epidemiological knowledge of circulating carbapenem-resistant Klebsiella pneumoniae (CRKP) is needed to develop effective strategies against this public health threat. Here we present a longitudinal analysis of 1,017 CRKP isolates recovered from patients from 40 hospitals across China between 2016 and 2020. Virulence gene and capsule typing revealed expansion of CRKP capsule type KL64 (59.5%) alongside decreases in KL47 prevalence. Hypervirulent CRKP increased in prevalence from 28.2% in 2016 to 45.7% in 2020. Phylogenetic and spatiotemporal analysis revealed Beijing and Shanghai as transmission hubs accounting for differential geographical prevalence of KL47 and KL64 strains across China. Moderate frequency capsule or O-antigen loss was also detected among isolates. Non-capsular CRKP were more susceptible to phagocytosis, attenuated during mouse infections, but showed increased serum resistance and biofilm formation. These findings give insight into CRKP serotype prevalence and dynamics, revealing the importance of monitoring serotype shifts for the future development of immunological strategies against CRKP infections.

The Molecular Epidemiology of Prevalent Klebsiella pneumoniae Strains and Humoral Antibody Responses against Carbapenem-Resistant K. pneumoniae Infections among Pediatric Patients in Shanghai.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has caused wide dissemination among pediatric patients globally and thus has aroused public concern. Here, we investigated the clinical epidemiological characteristics of 140 nonreplicate clinical K. pneumoniae strains isolated from pediatric patients between January and December 2021. Of all isolates, 16.43% (23 of 140) were CRKP strains, which predominantly contained KPC carbapenemase. wzi sequencing demonstrated that KL47 (65.22%, 15 of 23) was the most frequent capsular type, followed by KL64 (17.39%, 4 of 23). A total of 23 CRKP strains were classified into three different O-genotypes, including OL101 (65.22%, 15 of 23), O1 (26.09%, 6 of 23), and O3 (8.7%, 2 of 23). Interestingly, KL47 strains were strongly associated with OL101, while KL64 strains were all linked with O1. Some capsule-deficient strains were identified by serological typing, phage-typing, depolymerase-typing, and uronic acid assay. In this study, compared with healthy children, higher titers of anti-capsular polysaccharides (CPS) IgG were first detected in the sera of K47 and K64 K. pneumoniae-infected children, which had the effective bactericidal activity against corresponding serotype K. pneumoniae strains. These findings will facilitate the development of novel therapeutic and vaccine strategies against K. pneumoniae infection in children. IMPORTANCE The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains resistant to numerous antibiotics and the limited therapeutic options available have become an urgent health threat to the immunocompromised pediatric population. Vaccines and antibodies, especially those targeting capsular polysaccharides, may be novel and effective prevention and treatment options. Thus, it is important to understand the spread of CRKP in pediatric populations. This research presents OL101:KL47 and O1:KL64 as the predominant combinations among CRKP strains in children in Shanghai, China. The primary carbapenemase gene is KPC in CRKP strains. Additionally, this study found elevated levels of anti-CPS IgG against K47 and K64 K. pneumoniae strains in pediatric patients for the first time. The significant bactericidal activity of these anti-CPS IgGs was confirmed.

Gelidibacter maritimus sp. nov., isolated from marine sediment.

A Gram-stain-negative, yellow, strictly aerobic, non-flagellated, gliding, rod-shaped bacterial strain, was isolated from costal sediment, designated as F6074T. The strain F6074T grows optimally at 30 °C, pH 7.5, and 3.0% (w/v) NaCl. Cells of strain F6074T are 0.2-0.5 µm wide and 1.0-2.0 µm long. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain F6074T belonged to the genus Gelidibacter, with the highest sequence similarity to Gelidibacter japonicus JCM 31967T (98.0%), followed by G. flavus JCM 31135T (97.7%), and similarity between strain F6074T and the type species G. algens DSM 12408T was 96.0%. Genome sequencing results revealed a genome size of 47,07,621 bp. The DNA G + C content was 37.8 mol%. The ANI and dDDH values between strain F6074T and G. japonicus JCM 31967T were 83.9 and 27.8%, the values between strain F6074T and G. algens DSM 12408T were 77.5% and 31.5%, and the values between strain F6074T and G. flavus JCM 31135T were 84.3 and 27.9%, respectively. The predominant quinone was MK-6 and the major fatty acids were iso-C15:0, iso-C15:1G, iso-C17:0 3-OH, anteiso-C15:0 and summed feature 3. The polar lipids were consisted of phosphatidylethanolamine (PE), two unidentified aminolipids (AL) and three unidentified lipids (L1, L2, L3). Based on the phenotypic, phylogenetic and chemotaxonomic data, strain F6074T was considered to represent a novel species of the genus Gelidibacter, for which the name Gelidibacter maritimus sp. nov., is proposed. The type strain is F6074T (MCCC 1H00427T = KCTC 72942T).

Gelidibacter pelagius sp. nov., Isolated from Coastal Sediment.

A novel Gram-stain-negative, aerobic, rod-shaped, non-flagellated, and gliding bacterial strain, designated DF109T, was isolated from the coastal sediment of Jingzi Wharf, Weihai, China. The optimal growth occurs at 28°C, pH 7.0-7.5, and 1.0% (w/v) NaCl environment. The colony was yellow-colored, convex, non-transparent, and circular on 2216E Agar. Phylogenetic analyses of the 16S rRNA gene and genome sequence of this newly isolated strain revealed that it is a member of the genus Gelidibacter within the family Flavobacteriaceae. The phylogenetic analysis based on 16S rRNA gene sequences indicated that strain DF109T has the highest sequence similarity to Gelidibacter japonicus JCM 31967T (98.0%). The average nucleotide identity (ANI) values between genomes of DF109T and G. japonicus JCM 31967T and G. algens DSM 12408T were 86.3% and 78.7% and the digital DNA-DNA hybridization (dDDH) values were 31.4% and 22.4%, respectively. The sole isoprenoid quinone was MK-6 and the major cellular fatty acids were iso-C15:1G, iso-C17:0 3-OH, anteiso-C15:0, and iso-C16:0 3-OH. The major polar lipids of strain DF109T were an aminolipid, a phosphatidylethanolamine, and four unidentified lipids. The genomic DNA G+C content was 37.5 mol%. Strain DF109T is suggested to represent a novel species in the genus Gelidibacter, for which the name Gelidibacter pelagius sp. nov. is proposed. The type strain is DF109T (=MCCC 1H00454T=KCTC 82420T).

Tenacibaculum pelagium sp. nov., isolated from marine sediment.

A novel bright yellow pigmented, Gram-stain-negative, gliding, aerobic and rod-shaped marine bacterium, designated strain S7007T, was isolated from a marine sediment sample taken from Jingzi Wharf, Weihai, China. The bacterium was able to grow at 4-33 °C (optimum 28 °C), at pH 6.5-9.0 (optimum 7.0) and with 2.0-4.0% (w/v) NaCl (optimum 3.0%). According to the phylogenetic analysis based on the 16S rRNA gene sequences, strain S7007T was associated with the genus Tenacibaculum and showed highest similarity to Tenacibaculum adriaticum JCM 14633T (98.0%). The average nucleotide identity (ANI) scores of strain S7007T with T. adriaticum JCM 14633T and T. maritimum NBRC 110778T were 78.3% and 77.1%, respectively and the Genome-to-Genome Distance Calculator (dDDH) scores were 20.5% and 19.9%, respectively. The sole isoprenoid quinone was MK-6 and the major cellular fatty acids (> 10.0%) were iso-C15:0, iso-C15:0 3-OH, iso-C15: 1 G and summed feature 3 (comprising C16:1 ω7c and/or C16:1 ω6c). The major polar lipids of strain S7007T were phosphatidylethanolamine, phosphatidyldimethylethanolamine, one unidentified lipid and two unidentified aminolipids. The genomic DNA G + C content was 30.9 mol %. The combined phenotypic data and phylogenetic inference that strain S7007T should be classified as a novel species in the genus Tenacibaculum, for which the name Tenacibaculum pelagium sp. nov. is proposed. The type strain is S7007T (= MCCC 1H00428T = KCTC 72941T).

Chryseobacterium lacus sp. nov. Isolated From the Surface Water of Two Lakes With Light-Induced Carotenoid Production.

Two Gram-stain-negative, rod-shaped, gliding, catalase-positive, and facultative anaerobic strains, YLOS41T and XH07, were isolated from surface water of Yilong Lake and West Lake of Dali in Yunnan Province, respectively. Both strains were yellow-colored under light conditions and white-colored under dark conditions. The results of physiological and chemotaxonomic characterization, sequencing and phylogenetic analysis, and draft genome sequence comparison demonstrated that the two strains represented a single novel species within the genus Chryseobacterium, for which the name Chryseobacterium lacus sp. nov. is proposed. The type strain is YLOS41T (= KCTC 62352T = MCCC 1H00300T), and the second strain is XH07 (= KCTC 62993). During the cultivation process, we found that the colony color of the two strains changed from white to yellow with illumination. The study investigated the effects of light irradiation on the strain YLOS41T. Results showed that light irradiation did not affect the growth of cells but significantly increased carotenoid synthesis, which caused the change of colony color. In-depth metabolic analysis was conducted by transcriptome. The predominant changes were found for genes involved in carotenoid synthesis as protection from light damage. Based on the genome and transcriptome, we proved that strain YLOS41T possessed a complete synthetic pathway of carotenoid and speculated that the production was zeaxanthin. This was the first report of Chryseobacterium species with light-induced carotenoid synthesis. This study enhances our present knowledge on how Chryseobacterium species isolated from surface water responds to light damage.