We report an outbreak of carbapenemase-producing hypervirulent Klebsiella pneumoniae in two hospitals that undergo frequent patient transfers. Analysis of 11 completely assembled genomes showed that the bacteria were ST11-K64 strains. Moreover, 12 single nucleotide polymorphisms (SNPs) identified the strains as having originated from the same cluster, and were also indicative of the interhospital transmission of infection. Five plasmids were assembled in each of the strains. One plasmid carried several virulence genes, including the capsular polysaccharide regulators rmpA and rmpA2 . Two others carried antimicrobial-resistance genes, including one for carbapenem resistance, bla KPC–2 . Comparative genomic analysis indicated the occurrence of frequent and rapid gain and loss of genomic content along transmissions and the co-existence of progeny strains in the same ward. A 10-kbp fragment harboring antimicrobial resistance-conferring genes flanked by insert sequences was missing in a plasmid from strain KP20194c in patient 3, and this strain also likely subsequently infected patient 4. However, strains containing the 10-kbp fragment were also isolated from the ward environment at approximately the same time, and harbored different chromosome indels. Tn 1721 and multiple additional insert sequence-mediated transpositions were also seen. These results indicated that there is a rapid reshaping and diversification of the genomic pool of K. pneumoniae facilitated by mobile genetic elements, even a short time after outbreak onset. ST11-K64 CR-hvKP strains have the potential to become new significant superbugs and a threat to public health.

Introduction: Bloodstream infection (BSI) is associated with high mortality rates. Mycoplasma hominis, which rarely causes extragenital infections, has been shown to induce BSI and presents a clinical diagnostic and therapeutic challenge. Methods: In this study, we investigated the clinical characteristics, antibiotic resistance, and multilocus sequence typing (MLST) of eight BSI cases caused by M. hominis in South China from January 2018 to October 2021. Results: Underlying immunosuppression and genitourinary tract surgery are important risk factors for M. hominis BSI. The most prevalent clinical symptoms and signs were fever. Additional findings included elevated neutrophil count and C-reactive protein level. Furthermore, in this study, all the patients had erythrocytopenia. M. hominis harbored the highest rate of resistance to levofloxacin (75.0%), followed by sparfloxacin (50.0%), and gatifloxacin (37.5%). gyrA S153L was the most frequent mutation in levofloxacin-resistant strains, followed by parC S91I. parC K144R may be related to resistance to gatifloxacin and sparfloxacin. Eight strains showed sensitivity to all the other antibiotics analyzed (doxycycline, minocycline, josamycin, and clindamycin). MLST was performed in seven isolates, and seven new sequence types were described. We compared our isolates with all M. hominis strains from the PubMLST database, and one major clonal complex and eight singletons were identified. Conclusions: Our study clarified and expanded the clinical features and antibiotic resistance of M. hominis BSI. These findings are useful for the clinical diagnosis and control of M. hominis BSI.

Klebsiella pneumoniae may cause pyogenic infections, which are potentially life-threatening and bring great challenges for clinical management. However, the clinical and molecular characteristics of K. pneumoniae are poorly understood, and effective antibacterial treatment strategies are limited.