Xiao Wang

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) is priority pathogen for nosocomial infection control worldwide. This study aimed to elucidate differences in distribution, genotyping and antimicrobial resistance patterns between CRAB and carbapenem-susceptible Acinetobacter baumannii (CSAB) strains isolated from healthcare environments. Materials and methods: A total of 1,812 environmental samples were collected from 10 medical institutions in Pudong New Area between June and December 2024 for the identification of A. baumannii . Antimicrobial susceptibility testing, whole-genome sequencing, and bioinformatic analysis were performed to reveal molecular characteristics of A. baumannii. Results: A total of 81 A. baumannii strains were detected, with 39.51% CRAB ( n = 32) and 60.49% CSAB ( n = 49). CRAB strains were highly prevalent in intensive care units (ICUs, accounting for 83.33%) and patient-contact items, whereas CSAB were more evenly distributed. MLST analysis identified ST2 as dominant CRAB clone (78.13%), followed by ST164 (18.75%). CRAB isolates demonstrated 100% resistance to multiple antibiotics such as piperacillin/tazobactam and ciprofloxacin, whereas all CSAB isolates were susceptible to tested antibiotics except one ampicillin/sulbactam-resistant isolate. Carbapenem resistance in CRAB was predominantly mediated by class D carbapenemases, with carriage rate of the bla _OXA-23 gene reaching 96.88%. Notably, six ST164 isolates co-harbored class B and class D carbapenemase genes, which may elevate resistance severity. Bioinformatic analysis indicated that 22.20% of resistance plasmids in CRAB were predicted to be conjugative. CRAB exhibited a more diverse and extensive virulence gene profile than CSAB strains. Conclusions: The ICU environment was critical for CRAB control. ST2 and ST164 represented clones worthy of attention. CRAB exhibited stronger resistance, harbored more putatively conjugative plasmids and richer virulence-associated genes than CSAB, highlighting the need for targeted disinfection and surveillance of prevalent clones.

This study aimed to characterize the epidemiological characteristics and pathogen distribution of diarrhea among adults aged ≥60 in Pudong New Area, Shanghai. A retrospective analysis was conducted on 4310 diarrhea cases aged ≥60 collected from the ongoing surveillance from January 2010 to December 2024. Specimens were tested for 8 bacterial and 5 viral pathogens using culture and molecular methods. Detection rates were compared across age groups and over time, and age-specific trends were evaluated using joinpoint regression. The overall pathogen-positive rate was 42.20% (1819/4310). Viral infections accounted for the largest proportion (20.26%), mainly norovirus (13.53%) and rotavirus (4.78%). Bacterial infections accounted for 15.99%, predominantly Diarrheagenic E. coli (DEC) (5.94%), non-typhoidal Salmonella (NTS) (3.57%), and Campylobacter spp. (2.60%). Pathogen positivity peaked in 2017, declined after 2020 during the COVID-19 pandemic, and slightly increased thereafter. Viral infections occurred primarily in winter–spring (October–March), whereas bacterial infections peaked in summer–autumn (June–September). Among cases with single infections, the highest viral and bacterial positivity rates were observed in the 60–69 age group (both p < 0.05), while DEC was highest in those aged ≥80 (6.57%). Joinpoint regression revealed non-linear age patterns. Viral infections declined with age but rebounded around the early 90s, whereas bacterial infections remained relatively stable before increasing at similar ages. Norovirus, rotavirus, and DEC were the leading pathogens of infectious diarrhea among the elderly in Pudong New Area, Shanghai. Age-specific, temporal, and seasonal patterns underscore the need for targeted prevention strategies, particularly for the extreme elderly.

Carbapenem-resistant Acinetobacter baumannii (CRAB) represents a formidable nosocomial pathogen, with healthcare environments acting as critical reservoirs for its dissemination. In this study, we investigated the prevalence, antimicrobial resistance profiles and genomic characteristics of CRAB isolates collected from hospitals in Shanghai, China, between June and December 2024, identifying ST2 ^Pas (84.13%) and ST164 ^Pas (15.08%) as the predominant lineages among the 126 CRAB isolates recovered from clinical ( n =94), environmental ( n =29) and healthcare worker ( n =3) sources. Environmental CRAB accounted for the highest proportions on patient-contact surfaces (34.48%), medical devices (31.03%) and shared items (24.14%). Within the dominant ST2 ^Pas lineage, clinical isolates exhibited higher resistance rates to ampicillin/sulbactam, cefoperazone/sulbactam and levofloxacin, with significantly higher carriage rates of bla _TEM-1D compared to environmental isolates. Compared to ST164 ^Pas , ST2 ^Pas CRAB isolates exhibited greater resistance to amikacin, gentamicin, trimethoprim/sulfamethoxazole and minocycline and a higher prevalence of aph (3′)-Ia, aph (3″)-Ib, aph(3′ )-VI, aph (6)-Id, arm A, bla _OXA-66 , bla _TEM-1D , mph (E) and tet (B), but lower rates of bla _CARB-16 , bla _NDM-1 and bla _OXA-91 ( P< 0.05). Notably, comparative genomic analysis suggested putative adaptive differences between the two lineages. ST2 ^Pas retained the T6SS and biofilm-associated genes ( bap ), descriptive genomic features that suggest a potential capacity for active colonization. Conversely, the ST164 ^Pas clone lacked the T6SS gene cluster but was enriched with the surface adhesin ata and immune evasion-related genes. Concordantly, ST164 ^Pas CRAB isolates exhibited significantly stronger biofilm-forming capacities than ST2 ^Pas in vitro . We hypothesize that these genomic alterations and phenotypic traits may represent a fitness trade-off, potentially conferring a survival advantage under antibiotic pressure. Furthermore, bla _OXA-23 in ST2 ^Pas was predominantly carried on conjugative plasmids restricted to Acinetobacter species, whereas bla _NDM-1 in ST164 ^Pas was localized on a broad-host-range non-mobile plasmid, potentially facilitating cross-genus transmission. Although our ST164 ^Pas isolates shared high homology with clinical strains from Zhejiang, China, the genomic localization of bla _NDM-1 differed between the plasmid and chromosome, respectively. These descriptive genomic findings highlight the putative adaptive trajectories of the predominant ST2 ^Pas and emerging ST164 ^Pas clones, underscoring the critical need for comprehensive genomic surveillance, complemented by future phenotypic validation, to monitor their rapid evolution and dissemination.

Background: In China, Carbapenem-resistant Klebsiella pneumoniae (CRKP) is dominated by sequence type 11 (ST11) harbouring KPC-2, with KL64 displacing KL47 and KL25 emerging. ST859 (ST11 variant) has caused outbreaks, but its epidemiology is unclear. Materials and Methods: A total of 99 non-duplicate CRKP isolates were collected from June to December 2024. Antimicrobial susceptibility was determined by broth microdilution. The genomic sequences of the strains were obtained using next-generation sequencing technology. Resistance genes, virulence loci, and plasmid replicons were identified with Kleborate, Abricate, and MOB-suite, respectively. Results: ST11 accounted for 63.64% and ST859 for 15.15%. All ST859 were KL19, while ST11 were mainly KL25 (60.32%) and KL64 (26.98%). 76.8% co-harbored carbapenemase and extended-spectrum beta-lactamase (ESBL) genes, with KPC-2 and CTX-M-65 being the predominant types. Susceptibility rates were 100% to tigecycline, and 78.79% to ceftazidime/avibactam. ST859 CRKP isolates exhibited higher phenotypic resistance to tetracycline and colistin than ST11 CRKP isolates (p < 0.05), and carrying LAP-2, QnrS1, QnrS10, and tet(A) more frequently. ST11-KL25 showed higher resistance to amikacin, gentamicin, and chloramphenicol, with increased prevalence of CTX-M-65, TEM-1, rmtB, catA2, and dfrA14 compared to ST11-KL64 (p < 0.05). IncF was the most prevalent replicon and both ST859 and ST11 CRKP carry conjugative resistance plasmids, and the host range is predominantly Enterobacterales. Conclusions: ST859-KL19 ranks second to ST11 with higher resistance to tetracyclines and colistin. ST11-KL25 may have already displaced ST11-KL64 as the predominant capsular type in Shanghai, with distinct resistance profiles between KL variants. Long-term, multicenter surveillance is urgently needed to delineate the evolutionary trajectory and clinical impact of these emerging clones.

Background: Shigella spp. are critical pathogens causing diarrheal diseases. This study analyzed the epidemiological characteristics, antimicrobial resistance profiles, virulence factor profiles, and molecular patterns of Shigella isolates in Pudong New Area, Shanghai, from 2013 to 2024. Materials and Methods: Antimicrobial susceptibility of Shigella isolates was determined using the broth microdilution method. All molecular characterization analyses were based on whole-genome next-generation sequencing of Shigella strains. Results: A total of 55 Shigella spp. isolates were obtained from 17,670 enrolled diarrheal cases between 2013 and 2024, including 47 S. sonnei and 8 S. flexneri isolates. Resistance rates to sulfamethoxazole-trimethoprim (SXT), streptomycin (STR), nalidixic acid (NAL), ampicillin (AMP), and tetracycline (TET) all exceeded 90.00%. The resistance rate to azithromycin (AZI) increased from 12.50% to 60.00% with a fluctuating upward trend from 2013 to 2019; 97.87% of S. sonnei and 100.00% of S. flexneri isolates were multidrug-resistant. These isolates harbored multiple resistance genes and virulence factors. S. sonnei was dominated by ST152, while S. flexneri was predominantly ST245. These isolates were phylogenetically close to domestic (Beijing) and international (USA) strains of the same sequence typing collected at different time points, suggesting a common origin and stable transmission characteristics. Conclusion: From 2013 to 2024, the prevalent Shigella species in Pudong were S. sonnei and S. flexneri. Shigella isolates exhibited high resistance rates, and the situation of multidrug resistance was severe. Therefore, strengthening antimicrobial resistance monitoring and controlling regional transmission are of great significance. Meanwhile, genomic surveillance of Shigella ST152/ST245 is recommended for Pudong’s enteric pathogen control programs.