Viene presentata ed analizzata la flora vascolare dell’Oltrepò Pavese, uno dei territori floristicamente più variegati e meno conosciuti dell’Italia nord-occidentale. L’opera costituisce il primo di ...tre contributi relativi alla flora della provincia di Pavia, per la quale mancava un lavoro di sintesi da oltre centocinquant’anni. I due elenchi floristici allegati si basano sui dati raccolti in campo dagli autori, integrati con le informazioni derivanti dallo studio critico della bibliografia esistente e dalla revisione dei campioni conservati soprattutto presso l’Erbario Lombardo dell’Universita di Pavia (PAV) e l’erbario del Museo di Storia Naturale di Milano (MSNM). Nell’area di studio risultano presenti 1.871 taxa (specie, sottospecie e ibridi), di cui 183 non più ritrovati dopo il 1980; a questi si aggiungono 245 entità di presenza dubbia e 161 segnalate per errore. Gli endemiti italiani ammontano a 16 mentre il contingente alloctono conta 321 entità (neofite e archeofite). Vengono qui segnalate 4 nuove neofite (Bidens triplinervia, Cucurbita melopepo subsp. melopepo, Morus kagayamae, Vitis berlandieri × V. vinifera) e una nuova archeofita (× Triticosecale) per l’Italia; tra le 30 novità e le 16 conferme per la flora della Lombardia figurano 6 endemiti italiani (Adenostyles australis, Brachypodium genuense, Centaurea aplolepa s.l., Hieracium grovesianum s.l., Stipa etrusca, Tephroseris italica).
In February 2022, a critically ill patient colonized with a carbapenem-resistant K. pneumoniae producing KPC-3 and VIM-1 carbapenemases was hospitalized for SARS-CoV-2 in the intensive care unit of ...Policlinico Umberto I hospital in Rome, Italy. During 95 days of hospitalization, ceftazidime/avibactam, meropenem/vaborbactam, and cefiderocol were administered consecutively to treat 3 respiratory tract infections sustained by different bacterial agents. Those therapies altered the resistome of K. pneumoniae sequence type 512 colonizing or infecting the patient during the hospitalization period. In vivo evolution of the K. pneumoniae sequence type 512 resistome occurred through plasmid loss, outer membrane porin alteration, and a nonsense mutation in the cirA siderophore gene, resulting in high levels of cefiderocol resistance. Cross-selection can occur between K. pneumoniae and treatments prescribed for other infective agents. K. pneumoniae can stably colonize a patient, and antimicrobial-selective pressure can promote progressive K. pneumoniae resistome evolution, indicating a substantial public health threat.
In 2021,
Klebsiella pneumoniae
sequence type 307 (ST307) strains causing pulmonary and bloodstream infections identified in a hospital in Rome, Italy, reached high levels of resistance to ...ceftazidime-avibactam (CZA). One of these strains reached high levels of resistance to both CZA and carbapenems and carried two copies of
bla
KPC-3
and one copy of
bla
KPC-31
located on plasmid pKpQIL. The genomes and plasmids of CZA-resistant ST307 strains were analyzed to identify the molecular mechanisms leading to the evolution of resistance and compared with ST307 genomes at local and global levels. A complex pattern of multiple plasmids in rearranged configurations, coresident within the CZA-carbapenem–resistant
K. pneumoniae
strain, was observed. Characterization of these plasmids revealed recombination and segregation events explaining why
K. pneumoniae
isolates from the same patient had different antibiotic resistance profiles. This study illustrates the intense genetic plasticity occurring in ST307, one of the most worldwide-diffused
K. pneumoniae
high-risk clones.
In 2021, Klebsiella pneumoniae sequence type 307 (ST307) strains causing pulmonary and bloodstream infections identified in a hospital in Rome, Italy, reached high levels of resistance to ...ceftazidime-avibactam (CZA). One of these strains reached high levels of resistance to both CZA and carbapenems and carried two copies of
and one copy of
located on plasmid pKpQIL. The genomes and plasmids of CZA-resistant ST307 strains were analyzed to identify the molecular mechanisms leading to the evolution of resistance and compared with ST307 genomes at local and global levels. A complex pattern of multiple plasmids in rearranged configurations, coresident within the CZA-carbapenem-resistant K. pneumoniae strain, was observed. Characterization of these plasmids revealed recombination and segregation events explaining why K. pneumoniae isolates from the same patient had different antibiotic resistance profiles. This study illustrates the intense genetic plasticity occurring in ST307, one of the most worldwide-diffused K. pneumoniae high-risk clones.
The first reports of carbapenem-resistant
in our hospital date back to 2006. In that period, few ertapenem-resistant but meropenem-susceptible
isolates belonging to sequence type (ST) 37 were ...retrieved from clinical samples. These strains produced the CTX-M-15 extended spectrum β-lactamase, OmpK35 was depleted due to a nonsense mutation, and a novel OmpK36 variant was identified. Yet, starting from 2010,
carbapenemase (KPC)-producing ST512 isolates started prevailing and ST37 vanished from sight. Since 2018 the clinical use of the combination of ceftazidime-avibactam (CZA) has been introduced in clinical practice for the treatment of bacteria producing serine-β-lactamases, but KPC-producing, CZA-resistant
are emerging. In 2021, four CZA-resistant ST37 isolates producing KPC variants were isolated from the same number of patients.
KPC gene cloning in
was used to define the role of those KPC variants on CZA resistance, and whole genome sequencing was performed on these isolates and on three ST37 historical isolates from 2011. CZA resistance was due to mutations in the
KPC genes carried on related pKpQIL-type plasmids, and three variants of the KPC enzyme have been identified in the four ST37 strains. The four ST37 isolates were closely related to each other and to the historical isolates, suggesting that ST37 survived without notice in our hospital for 10 years, waiting to re-emerge as a CZA-resistant
clone. The ancestor of these contemporary isolates derives from ST37 wild-type porin strains, with no other mutations in chromosomal genes involved in conferring antibiotic resistance (
,
,
,
,
).
Carbapenemase-producing Klebsiella pneumoniae represents a major public health issue globally. Isolates with resistance to the newest drugs, like ceftazidime/avibactam (CZA), are increasingly ...reported. In this study, we analyzed the evolution of KPC-3-producing sequence type (ST) 512 K. pneumoniae strains isolated at three different times (hospitalization days 45, 56, and 78) from the same patient, two of which were observed in a pericholecystic liver abscess. The three K. pneumoniae isolates (295Kp, 304Kp, and hmv-318Kp) from the same patient were subjected to antimicrobial susceptibility testing, whole-genome sequencing, sedimentation assay, biofilm measurement, serum resistance assay, macrophage phagocytosis, and adhesion assays. KPC-producing isolate hmv-318Kp exhibited carbapenem susceptibility, hypermucoviscous (hmv) colony phenotype and CZA resistance. Virulence markers of hypervirulent Klebsiella were absent. Two non-synonymous mutations were identified in the hmv-318Kp genome comparing with isogenic strains: a single-nucleotide polymorphism (SNP) occurred in the pKpQIL plasmid, changing blaKPC-3 in the blaKPC-31 gene variant, conferring CZA resistance; and a second SNP occurred in the wzc gene of the capsular biosynthesis cluster, encoding a tyrosine kinase, resulting in the F557S Wzc protein mutation. The Klebsiella pneumoniae strain exhibiting an hmv phenotype (hmv-Kp) phenotype has been previously associated with amino acid substitutions occurring in the Wzc tyrosin kinase protein. We observed in vivo evolution of the ST512 strain to CZA resistance and acquisition of hypermucoviscosity. The pathogenetic role of the detected Wzc substitution is not fully elucidated, but other Wzc mutations were previously reported in hmv K. pneumoniae. Wzc mutants may be more frequent than expected and an underreported cause of hypermucoviscosity in K. pneumoniae clinical isolates.IMPORTANCEHere we describe the evolution of KPC-3-producing ST512 K. pneumoniae isolated at three different times from the same patient of which the last one, from a biliary abscess, showed CZA resistance by KPC-31 production and manifested hmv colony phenotype. Hypervirulent Klebsiella pneumoniae (hv-Kp) isolates are increasingly reported worldwide. Their hypervirulent traits are associated with the presence of rmpA/A2 genes and an hmv. In this study, we identified an hmv-Kp that lacked the rmpA-D cluster but showed an amino acid substitution in the Wzc tyrosin kinase protein, involved in the capsular biosynthesis. This hmv-Kp strain emerged in vivo and evolved resistance to ceftazidime/avibactam resistance in a liver abscess of a patient. Our findings suggest that wzc mutations may be underreported, making it challenging to distinguish hv-Kp from “classic” K. pneumoniae with an hmv phenotype.
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