An IncN-ST7 epidemic plasmid mediates the dissemination of carbapenem-resistant Klebsiella pneumoniae in a neonatal intensive care unit in China over 10 years.

OBJECTIVES: Carbapenem-resistant Klebsiella pneumoniae (CRKP) has widely disseminated globally, but its epidemiological characterization and clinical significance in paediatric patients are not well understood. In this study, we aimed to trace the dissemination dynamics of CRKP in the neonatal intensive care unit (NICU) of a tertiary hospital over a 10-y period. METHODS: We collected 67 non-duplicate K. pneumoniae species complex isolates from the NICU with patient metadata during 2009-2018. Antimicrobial susceptibility was determined by the agar or broth microdilution method. Risk factors for CRKP-positive patients were identified by univariate and multivariate analysis. Genetic characterization was dissected by whole-genome sequencing. Plasmid transmissibility, stability, and fitness were assessed. RESULTS: Thirty-four of 67 isolates (50.75%) were identified as CRKP. Premature rupture of membranes, gestational age, and invasive procedures are independent risk factors for CRKP-positive patients. The annual isolation rate of CRKP varied between 0% and 88.9%, and multiple clonal replacements were observed during the study period, which could be largely due to the division of the NICU. All but one CRKP produced IMP-4 carbapenemase, which was encoded by an IncN-ST7 epidemic plasmid, suggesting that the IncN-ST7 plasmid mediated the CRKP dissemination in the NICU over 10 y. The same plasmid was found in several CRKP isolates from adult patients, of which two ST17 isolates from the neurosurgery department shared a high homology with the ST17 isolates from the NICU, indicating possible cross-departmental transmission. CONCLUSION: Our study highlights the urgent need for infection control measures targeting high-risk plasmids like IncN-ST7.

A point mutation in recC associated with subclonal replacement of carbapenem-resistant Klebsiella pneumoniae ST11 in China.

Adaptation to selective pressures is crucial for clinically important pathogens to establish epidemics, but the underlying evolutionary drivers remain poorly understood. The current epidemic of carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a significant threat to public health. In this study we analyzed the genome sequences of 794 CRKP bloodstream isolates collected in 40 hospitals in China between 2014 and 2019. We uncovered a subclonal replacement in the predominant clone ST11, where the previously prevalent subclone OL101:KL47 was replaced by O2v1:KL64 over time in a stepwise manner. O2v1:KL64 carried a higher load of mobile genetic elements, and a point mutation exclusively detected in the recC of O2v1:KL64 significantly promotes recombination proficiency. The epidemic success of O2v1:KL64 was further associated with a hypervirulent sublineage with enhanced resistance to phagocytosis, sulfamethoxazole-trimethoprim, and tetracycline. The phenotypic alterations were linked to the overrepresentation of hypervirulence determinants and antibiotic genes conferred by the acquisition of an rmpA-positive pLVPK-like virulence plasmid and an IncFII-type multidrug-resistant plasmid, respectively. The dissemination of the sublineage was further promoted by more frequent inter-hospital transmission. The results collectively demonstrate that the expansion of O2v1:KL64 is correlated to a repertoire of genomic alterations convergent in a subpopulation with evolutionary advantages.

Methodology Establishment and Application of VITEK Mass Spectrometry to Detect Carbapenemase-Producing Klebsiella pneumoniae.

The ability of VITEK mass spectrometry (MS) in detection of bacterial resistance is currently under exploration and evaluation. In this study, we developed and validated a VITEK MS method to rapidly test carbapenemase-producing Klebsiella pneumoniae (CPKP). Solvents, antibiotic concentrations, crystal conditions and times, centrifugation speeds, and other factors were optimized to design a rapid sample pretreatment process for CPKP detection by VITEK MS. The related parameters of the mass spectrum were adjusted on the instrument to establish an CPKP detection mode. 133 clinically isolated strains of CPKP in the microbiology laboratory at the Shenzhen People's Hospital from 2004 to 2017 were selected for accuracy evaluation. The fresh suspected strains from the microbiology laboratory in 2020 were used to complete the clinical verification. Two antibiotics, meropenem (MEM) and imipenem (IPM), were used as substrates. These two substrates were incubated with suspected CPKP, and the results were obtained by VITEK MS detection. Using this method, different types of CPKP showed different detection results and all the CPKP strains producing KPC-2 and IMP-4 carbapenemase were detected by VITEK MS. Thus, VITEK MS can be used for rapid detection of CPKP, especially for some common types of CPKP. This method provides high accuracy and speed of detection. Combined with its cost advantages, it can be intensely valuable in clinical microbiology laboratories after the standard operating procedures are determined.

[Reference interval in preliminary investigation of maternal thyroid function during pregnancy in Shenzhen China].

OBJECTIVE: To explore the thyroid function distribution of different trimesters among normal pregnant women and establish the reference interval for maternal thyroid function during pregnancy in Shenzhen, China. METHODS: A prospective study was conducted for healthy pregnant women in first trimester (n = 334), second trimester (n = 272), third trimester (n = 271) and non-pregnant controls (n = 77) from December 2012 to June 2013 at our hospital. Free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), triiodothyronine (TT3) and thyroxine (T4) of four groups were measured and analyzed. And the reference intervals for different trimesters were established. RESULTS: TSH declined in the first trimester and then rose in the second trimester. The reference ranges of TSH for early, middle and late pregnancy were 0.08-4.39, 0.41-4.16 and 0.30-5.46 mIU/L respectively. FT4 and healthy control groups showed no significant difference in the first trimester. But it declined in the second trimester. The reference ranges of FT4 for early, middle and late pregnancy were 7.74-14.58, 6.81-12.00 and 6.36-10.99 pmol/L respectively. FT3 rose slightly in the first trimester and then gradually decreased. The reference ranges of FT3 for early, middle and late pregnancy were 3.59-5.59, 3.34-4.91 and 3.09-4.58 pmol/L respectively. CONCLUSIONS: As compared with healthy control women in Shenzhen, thyroid function indicators of pregnant women show statistically significant differences. And the establishment of indicators of women's thyroid function reference intervals for different trimesters has important clinical significance in Shenzhen.