Transmission of blaNDM in Enterobacteriaceae among animals, food and human.

Despite carbapenems not being used in animals, carbapenem-resistant Enterobacterales (CRE), particularly New Delhi metallo-ß-lactamase-producing CRE (NDM-CRE), are prevalent in livestock. Concurrently, the incidence of human infections caused by NDM-CRE is rising, particularly in children. Although a positive association between livestock production and human NDM-CRE infections at the national level was identified, the evidence of direct transmission of NDM originating from livestock to humans remains largely unknown. Here, we conducted a cross-sectional study in Chengdu, Sichuan Province, to examine the prevalence of NDM-CRE in chickens and pigs along the breeding-slaughtering-retail chains, in pork in cafeterias of schools, and in colonizations and infections from children's hospital and examined the correlation of NDM-CRE among animals, foods and humans. Overall, the blaNDM increases gradually along the chicken and pig breeding (4.70%/2.0%) -slaughtering (7.60%/22.40%) -retail (65.56%/34.26%) chains. The slaughterhouse has become a hotspot for cross-contamination and amplifier of blaNDM. Notably, 63.11% of pork from the school cafeteria was positive for blaNDM. The prevalence of blaNDM in intestinal and infection samples from children's hospitals was 21.68% and 19.80%, respectively. whole genome sequencing (WGS) analysis revealed the sporadic, not large-scale, clonal spread of NDM-CRE along the chicken and pig breeding-slaughtering-retail chain, with further spreading via IncX3-blaNDM plasmid within each stage of whole chains. Clonal transmission of NDM-CRE is predominant in children's hospitals. The IncX3-blaNDM plasmid was highly prevalent among animals and humans and accounted for 57.7% of Escherichia coli and 91.3% of Klebsiella pneumoniae. Attention should be directed towards the IncX3 plasmid to control the transmission of blaNDM between animals and humans.

Antimicrobial resistance profiles of common mastitis pathogens on large Chinese dairy farms.

The primary objective of this study was to determine the antimicrobial resistance (AMR) profile of common mastitis pathogens on large Chinese dairy farms. A total of 673 isolates, including Staphylococcus aureus (14.41%, 97/673), coagulase-negative staphylococci (CNS, 52.30%, 352/673), Streptococcus agalactiae (5.64%, 38/673), non-agalactiae streptococci (7.42%, 50/673), Acinetobacter spp. (7.72%, 52/673), Escherichia spp. (6.39%, 43/673), and Klebsiella spp. (6.09%, 41/673), were collected from 15 large Chinese dairy farms in 12 provinces. The AMR profiles were measured using a microdilution method. Our results showed that more than 75% of Staph. aureus (87/97) and CNS (291/352) were resistant to penicillin (PEN). More than 30% of Escherichia spp. (15/43) showed resistance to ampicillin (AMP). However, less than 10% CNS and non-agalactiae streptococci showed resistance to amoxicillin/clavulanate (AMC; 1/352; 0/50), cephalexin (LEX; 1/352; 0/50), ceftiofur (EFT; 10/352; 0/50), and rifaximin (RIX; 21/352; 2/50); less than 10% Staph. aureus showed resistance to AMC (1/97), oxacillin (OX; 3/97), LEX (1/97), EFT (2/97), and RIX (2/97); less than 10% Strep. agalactiae showed resistance to PEN (3/38), AMC (0/38), LEX (0/38), EFT (0/38), and RIX (0/38); and less than 10% Escherichia spp. showed resistance to AMC (1/43) and EFT (4/43). These results suggested that most mastitis pathogens were susceptible to most antimicrobials with exceptions of Staph. aureus tested against penicillin or ampicillin and CNS against penicillin or oxacillin. To control the AMR threat in Chinese dairy farms, a nationwide surveillance program for AMR of bovine mastitis pathogens is needed.

Clonal and Horizontal Transmission of blaNDM among Klebsiella pneumoniae in Children's Intensive Care Units.

Increasing infections caused by blaNDM-carrying Klebsiella pneumoniae (NDM-KP) are an urgent threat to children with weakened immunity and limited antibiotic use. Preventing and intervening in NDM-KP infections requires a clear understanding of the pathogen's molecular and epidemiological characteristics. We investigated the prevalence and characteristics of NDM-KP in six children's hospitals from five Chinese provinces/municipalities. We collected 111 NDM-KP strains (40 NDM-1, one NDM-4 and 70 NDM-5) from neonatal intensive care units (NICUs) and pediatric intensive care units (PICUs) from June 2017 to June 2018; these strains accounted for 31.62% of all carbapenem-resistant K. pneumoniae (CR-KP). Although NDM-KP isolates exhibited high resistance to all carbapenems, including ertapenem (MIC: ≥32 mg/L, 96.4%), imipenem (MIC: ≥16 mg/L, 90.1%) and meropenem (MIC: ≥16 mg/L, 99.1%), they were fully sensitive to amikacin, tigecycline and polymyxin B, and presented low resistance to levofloxacin (9.9%) and gentamicin (15.3%). Whole-genome sequencing was conducted to gain insight into the molecular characterizations of NDM-KP isolates. The NDM-KP isolates belonged to 20 sequence types (STs), and ST2407 (n = 45) dominated in one hospital from Chengdu. ST2407 isolates with fewer single-nucleotide polymorphisms (SNP < 38) were found either in the same hospital or different hospitals. Most blaNDM (81.1%, 90/111), including all blaNDM-5 and blaNDM-4 and 47.5% (19/40) of blaNDM-1, in NDM-KP isolates with 13 STs were associated with the IncX3 plasmid. Our results indicated that both explosive clonal transmission and horizontal transmission of blaNDM occur among NDM-KP strains in children's hospitals. These data provide a basis for preventing and controlling NDM-KP-associated infectious diseases in hospitalized children, especially in neonates. IMPORTANCE The blaNDM gene is playing an increasingly important role in infections caused by CR-KP, especially in children. However, systematic detection and bioinformatics analysis of NDM-KP in children's hospitals are lacking in China. In this study, a total of 111 NDM-positive K. pneumoniae isolates were selected from the China Antimicrobial Surveillance Network for further investigation. The isolates were further characterized using state-of-the-art molecular techniques. Our findings suggested the clonal and horizontal transmission of blaNDM in K. pneumoniae in NICUs/PICUs. Key plasmids (IncX3) and ST diversity contribute to the spread of blaNDM. In addition, our findings provided recommendations for pediatric clinicians to use antibiotics to treat NDM-KP infections. Our current large-scale epidemiological survey would support further infection intervention strategies of NDM-KP in NICU/PICU of children's hospitals.

Comparative analysis of genomic characteristics, fitness and virulence of MRSA ST398 and ST9 isolated from China and Germany.

Methicillin-resistant Staphylococcus aureus (MRSA) of sequence types ST398 and ST9 are dominant lineages among livestock in Europe and Asia, respectively. Although both STs were commonly found as colonizers of the skin and the mucosal membranes, MRSA ST398, rather than MRSA ST9, has been reported to cause infections in humans and animals. Herein, we comparatively analyzed the genomic characteristics, fitness and virulence of MRSA ST398 and ST9 isolated from pigs in both China (CHN) and Germany (GER) to explore the factors that lead to differences in their epidemics and pathogenicity. We observed that the CHN-MRSA ST9 and the GER-MRSA ST9 have evolved independently, whereas the CHN-MRSA ST398 and GER-MRSA ST398 had close evolutionary relationships. Resistance to antimicrobial agents commonly used in livestock, the enhanced ability of biofilm formation, and the resistance to desiccation contribute to the success of the dominant clones of CHN-MRSA ST9 and GER-MRSA ST398, and the vwbνSaα gene on the genomic island might in part contribute to their colonization fitness in pigs. All MRSA ST398 strains revealed more diverse genome structures, higher tolerance to acids and high osmotic pressure, and greater competitive fitness in co-culture experiments. Notably, we identified and characterized a novel hysAνSaß gene, which was located on the genomic island νSaß of MRSA ST398 but was absent in MRSA ST9. The enhanced pathogenicity of the MRSA ST398 strains due to hysAνSaß might in part explain why MRSA ST398 strains are more likely to cause infections.

Genomic epidemiology of animal-derived tigecycline-resistant Escherichia coli across China reveals recent endemic plasmid-encoded tet(X4) gene.

Public health interventions to control the recent emergence of plasmid-mediated tigecycline resistance genes rely on a comprehensive understanding of its epidemiology and distribution over a wide range of geographical scales. Here we analysed an Escherichia coli collection isolated from pigs and chickens in China in 2018, and ascertained that the tet(X4) gene was not present at high prevalence across China, but was highly endemic in northwestern China. Genomic analysis of tet(X4)-positive E. coli demonstrated a recent and regional dissemination of tet(X4) among various clonal backgrounds and plasmids in northwestern China, whereas a parallel epidemic coincided with the independent acquisition of tet(X4) in E. coli from the remaining provinces. The high genetic similarity of tet(X4)-positive E. coli and human commensal E. coli suggests the possibility of its spreading into humans. Our study provides a systematic analysis of the current epidemiology of tet(X4) and identifies priorities for optimising timely intervention strategies.

High colonization rate of a novel carbapenem-resistant Klebsiella lineage among migratory birds at Qinghai Lake, China.

OBJECTIVES: The emergence of carbapenemase-positive Enterobacteriaceae poses a serious threat to public health worldwide. Here we conducted a molecular surveillance study on carbapenem-resistant Enterobacteriaceae (CRE) colonization among migratory birds at Qinghai Lake in China. METHODS: A total of 420 samples from migratory birds and their surrounding environment were collected at three sites along the Qinghai Lake bird island. Carbapenem-non-susceptible isolates were identified by 16S rDNA sequencing and MALDI-TOF MS. Carbapenemase producers were determined by Carba NP testing. Antimicrobial susceptibility testing, transfer ability and PFGE were also performed, and 46 isolates from different pulsotypes were analysed by WGS. RESULTS: Three hundred and fifty isolates were carbapenemase producers based on Carba NP testing, while 233 Klebsiella spp. and 2 Escherichia coli isolates were NDM-5-carriers. PFGE was performed and showed that the isolates were grouped into five pulsotypes; among these, type A was predominant (86.7%, n = 202) and belonged to a novel Klebsiella lineage, ST1697. WGS analysis indicated that ST1697 strains may be a hybrid of the recombination of Klebsiella quasipneumoniae subsp. similipneumoniae and Klebsiella pneumoniae genomes. CONCLUSIONS: This high frequency of carbapenemase producers in migratory birds is unexpected. These results provide new insight into the spread of antibiotic resistance, and highlight that continued vigilance for MDR carbapenemase-producing Enterobacteriaceae in migratory birds is urgently needed.