In this study was analyzed the prevalence of the main resistance genes encoding the carbapenemases KPC, VIM, NDM, IMP, OXA in Gram-negative bacteria isolated from blood cultures from various departments of the Ancona regional hospital. The global spread of carbapenem-resistant Enterobacteriaceae (CRE) is becoming increasingly worrying, especially in the nosocomial setting because carbapenems represent the drugs of choice and last resort in the treatment of infections caused by multiresistant Gram-negative bacteria. The strains isolated over the course of 4 months (May-August 2022) were evaluated for the presence of particular plasmids or mobile genetic elements responsible for the spread of carbapenem resistance and the genetic correlation between strains belonging to the same species was studied to try to identify any epidemic clones spread at our regional hospital. The prevalence of carbapenem resistance was 12%, and mainly concerned the species Klebsiella pneumoniae and Acinetobacter baumannii. Most K. pneumoniae strains were included in two clones belonging to sequence types ST101 and ST1519. The A. baumannii strains, however, did not appear to be genetically related, and all belonged to the same ST (ST2), which is one of the best-known epidemic clones, widespread globally. Genomic analysis highlighted the KPC carbapenemase gene in all K. pneumoniae strains (except one), while in the A. baumannii strains the OXA-23 and OXA-66 genes which have been described as carbapenemase genes more frequent in A. baumannii strains. In all K. pneumoniae strains except strain 151, the genes encoding the KPC-3 carbapenemase were located at the plasmid level, and in most cases the plasmids belonged to the IncF incompatibility group, ranging in size from ~100 and ~270 kb and were all multireplicons characterized by the FIIk - FIB combination (pQIL) demonstrating that they could be derived from plasmids similar to the pKpQIL commonly involved in the spread of carbapenem resistance in K. pneumoniae. The high homology of these plasmids also allowed us to hypothesize that the spread of resistance to carbapenems in the strains isolated from the different departments could be due to the circulation of the two main genotypes (ST101 and ST1519) but also to the possible transmission of the same plasmid from a strain to another. The ability of these plasmids to be transferred by conjugation or to transfer resistance to carbapenems will be verified in future experiments aimed at studying the mechanisms of spread of antibiotic resistance.
In questo studio è stata analizzata la prevalenza dei principali geni di resistenza che codificano le carbapenemasi KPC, VIM, NDM, IMP, OXA in batteri Gram-negativi isolati da emocolture provenienti da vari reparti dell’ospedale regionale di Ancona. La diffusione a livello globale delle Enterobacteriaceae resistenti ai carbapenemi (CRE) sta diventando sempre più preoccupante, soprattutto in ambito nosocomiale perché i carbapenemi rappresentano i farmaci di scelta e di ultima risorsa nel trattamento di infezioni da batteri Gram-negativi multiresistenti. I ceppi isolati nel corso di 4 mesi (maggio-agosto 2022) sono stati valutati per la presenza di particolari plasmidi o elementi genetici mobili responsabili della diffusione della resistenza ai carbapenemi ed è stata studiata la correlazione genetica tra ceppi appartenenti alla stessa specie per cercare di individuare eventuali cloni epidemici diffusi presso il nostro ospedale regionale. La prevalenza della resistenza ai carbapenemi era del 12%, e riguardava soprattutto le specie Klebsiella pneumoniae e Acinetobacter baumannii. La maggior parte dei ceppi di K. pneumoniae erano inclusi in due cloni appartenenti ai sequence type ST101 e ST1519. I ceppi di A. baumannii invece non sembravano correlati geneticamente, e appartenevano tutti allo stesso ST (ST2), che è uno dei cloni epidemici più conosciuti, diffuso a livello globale. L’analisi genomica ha evidenziato in tutti i ceppi di K. pneumoniae (tranne uno) il gene per la carbapenemasi KPC, mentre nei ceppi di A. baumannii i geni OXA-23 e OXA-66 che sono stati descritti come i geni di carbapenemasi più frequenti nei ceppi di A. baumannii. In tutti i ceppi di K. pneumoniae ad eccezione del ceppo 151, i geni che codificavano per la carbapenemasi KPC-3 erano localizzati a livello plasmidico e nella maggior parte dei casi i plasmidi appartenevano al gruppo di incompatibilità IncF, avevano dimensioni comprese tra ~100 e ~270 kb ed erano tutti multirepliconi caratterizzati dalla combinazione FIIk - FIB (pQIL) a dimostrazione che potrebbero essere derivati da plasmidi simili al pKpQIL comunemente coinvolto nella diffusione della resistenza ai carbapenemi in K. pneumoniae. L’elevata omologia di tali plasmidi ci ha permesso inoltre di ipotizzare che la diffusione della resistenza ai carbapenemi nei ceppi isolati dai diversi reparti potrebbe essere dovuta alla circolazione dei due principali genotipi (ST101 e ST1519) ma anche alla possibile trasmissione dello stesso plasmide da un ceppo all’altro. La capacità di tali plasmidi di essere trasferiti mediante coniugazione o di trasferire la resistenza ai carbapenemi verrà verificata in futuri esperimenti volti allo studio dei meccanismi di diffusione dell’antibiotico-resistenza.
Prevalenza di ceppi produttori di carbapenemasi tra Gram-negativi isolati da emocoltura
MOROZENCU, ANDREEA
2022/2023
Abstract
In this study was analyzed the prevalence of the main resistance genes encoding the carbapenemases KPC, VIM, NDM, IMP, OXA in Gram-negative bacteria isolated from blood cultures from various departments of the Ancona regional hospital. The global spread of carbapenem-resistant Enterobacteriaceae (CRE) is becoming increasingly worrying, especially in the nosocomial setting because carbapenems represent the drugs of choice and last resort in the treatment of infections caused by multiresistant Gram-negative bacteria. The strains isolated over the course of 4 months (May-August 2022) were evaluated for the presence of particular plasmids or mobile genetic elements responsible for the spread of carbapenem resistance and the genetic correlation between strains belonging to the same species was studied to try to identify any epidemic clones spread at our regional hospital. The prevalence of carbapenem resistance was 12%, and mainly concerned the species Klebsiella pneumoniae and Acinetobacter baumannii. Most K. pneumoniae strains were included in two clones belonging to sequence types ST101 and ST1519. The A. baumannii strains, however, did not appear to be genetically related, and all belonged to the same ST (ST2), which is one of the best-known epidemic clones, widespread globally. Genomic analysis highlighted the KPC carbapenemase gene in all K. pneumoniae strains (except one), while in the A. baumannii strains the OXA-23 and OXA-66 genes which have been described as carbapenemase genes more frequent in A. baumannii strains. In all K. pneumoniae strains except strain 151, the genes encoding the KPC-3 carbapenemase were located at the plasmid level, and in most cases the plasmids belonged to the IncF incompatibility group, ranging in size from ~100 and ~270 kb and were all multireplicons characterized by the FIIk - FIB combination (pQIL) demonstrating that they could be derived from plasmids similar to the pKpQIL commonly involved in the spread of carbapenem resistance in K. pneumoniae. The high homology of these plasmids also allowed us to hypothesize that the spread of resistance to carbapenems in the strains isolated from the different departments could be due to the circulation of the two main genotypes (ST101 and ST1519) but also to the possible transmission of the same plasmid from a strain to another. The ability of these plasmids to be transferred by conjugation or to transfer resistance to carbapenems will be verified in future experiments aimed at studying the mechanisms of spread of antibiotic resistance.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/14860