RESUMEN
Human-induced transformations of ecosystems usually result in fragmented populations subject to increased extinction risk. Fragmentation is also often associated with novel environmental heterogeneity, which in combination with restricted gene flow may increase the opportunity for local adaptation. To manage at-risk populations in these landscapes, it is important to understand how gene flow is changing, and how populations respond to habitat loss. We conducted a landscape genomics analysis using Restriction-site Associated DNA sequencing to investigate the evolutionary response of the critically endangered Dahl's Toad-headed turtle (Mesoclemmys dahli) to severe habitat modification. The species has lost almost all of its natural habitat in the southwestern part of its range and about 70% in the northeast. Based on least cost path analysis across different resistance surfaces for 3,211 SNPs, we found that the landscape matrix is restricting gene flow, causing the fragmentation of the species into at least six populations. Genome scans and allele-environment association analyses indicate that the population fragments in the deforested grasslands of the southwest are adaptively different from those in the more forested northeast. Populations in areas with no forest had low levels of adaptive genetic diversity and the fixation of ancestrally-polymorphic SNPs, consistent with directional selection in this novel environment. Our results suggest that this forest-stream specialist is adapting to pond-grassland conditions, but it is also suffering from negative consequences of habitat loss, including genetic erosion, isolation, small effective population sizes, and inbreeding. We recommend gene flow restoration via genetic rescue to counteract these threats, and provide guidance for this strategy.
Asunto(s)
Especies en Peligro de Extinción , Bosques , Flujo Génico , Variación Genética , Genómica , Clima Tropical , Tortugas/genética , Adaptación Fisiológica/genética , Animales , Colombia , Genética de Población , Genotipo , Geografía , Heterocigoto , Endogamia , Densidad de Población , Análisis de Secuencia de ADNRESUMEN
BACKGROUND: In Argentina, there has been an abrupt increase in KPC-2-producing Klebsiella pneumoniae (K. pneumoniae). Tucumán is a multi-border area, so the rapid dissemination of carbapenem-resistant K. pneumoniae is a clinically relevant problem for the region. OBJECTIVES: This study aimed to investigate the epidemiological and molecular patterns of KPC-producing K. pneumoniae clinical isolates collected from different hospitals in Tucumán. METHODS: Carbapenem-resistant K. pneumoniae strains were sequentially and uniquely collected during two time periods. Antibiotic susceptibility was determined by the automated Vitex 2® system and using the standard agar dilution test. Multilocus sequence typing and pulsed-field electrophoresis were used for epidemiological analysis. The genetic structures around blaKPC and the encoding genes of extended-spectrum ß-lactamases were detected by polymerase chain reaction and sequencing. Plasmids were analysed by conjugation and using the plasmid relaxase gene-typing method. RESULTS: All 37 isolates were multidrug resistant, and theblaKPC-2 gene was confirmed in all of them. In 17 isolates (45.9%), the blaCTX-M-2 gene was also amplified, as well as blaSHV-2 in five isolates (13.5%) and blaCTX-M-2/blaSHV-2 in four isolates (10.8%). The molecular epidemiology of the blaKPC-2 gene has resulted in it being associated with an IncL/M transferable plasmid disseminating in various sequence types (STs) (ST17, ST556, ST342, ST147, ST461, ST65, ST15 and ST70), and in a new genetic environment with a 764-bp deletion in the ISKpn7-blaKPC region. CONCLUSIONS: These findings contribute to the understanding of the great diversity of the blaKPC-2-carrying genetic platforms.
Asunto(s)
Carbapenémicos/farmacología , Infecciones por Klebsiella/microbiología , Klebsiella pneumoniae/genética , beta-Lactamasas/metabolismo , Argentina , Farmacorresistencia Bacteriana , Electroforesis en Gel de Campo Pulsado , Humanos , Infecciones por Klebsiella/tratamiento farmacológico , Klebsiella pneumoniae/metabolismo , Pruebas de Sensibilidad Microbiana , Epidemiología Molecular , Tipificación de Secuencias Multilocus , Plásmidos/genética , Estudios Retrospectivos , beta-Lactamasas/genéticaRESUMEN
The predominance of Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae was caused by the spread of ST258 clone. In Latin America, KPC was reported in 2006, with the isolation of genetically unrelated K. pneumoniae in Colombia. Since then, the expansion of blaKPC in either K. pneumoniae ST258 or other Enterobacteriaceae (ETB) species was increasingly reported. In this study, we characterized 89 KPC-producing Escherichia coli, Klebsiella oxytoca, Serratia marcescens, and Citrobacter freundii that were received between 2010 and 2014. The results revealed that all isolates harbored blaKPC-2. Moreover, the dissemination of KPC by non-K. pneumoniae was mainly caused by the dispersion of ETB mostly genetically unrelated. E. coli is a community pathogen that may serve as the vehicle for the spread of KPC into community settings. Recently, KPC was detected in E. coli ST131, an international epidemic and multidrug-resistant clone. We found that 5/29 KPC-producing E. coli belonged to ST131 and four were blaCTXM-15 producers. The detection of blaKPC in ST131 should be closely monitored to prevent further dissemination. The blaKPC is generally located within Tn4401 transposon capable of mobilization through transposition found in plasmids in ST258. Less is known about the diversity of blaKPC genetic elements that disseminate horizontally among other species of ETB. We found that 16/29 E. coli and 2/18 S. marcescens harbored blaKPC-2 in Tn4401a. In 71 isolates, blaKPC-2 was located amidst diverse Tn3-derived genetic elements bearing non-Tn4401 structure. Further studies on the plasmids that encode blaKPC-2 in these clinical isolates may provide additional insight into its transmission mechanisms.
Asunto(s)
Proteínas Bacterianas/genética , Citrobacter freundii/genética , Escherichia coli/genética , Klebsiella oxytoca/genética , Serratia marcescens/genética , beta-Lactamasas/genética , Argentina , Infección Hospitalaria/microbiología , Elementos Transponibles de ADN/genética , Farmacorresistencia Bacteriana/genética , Resistencia a Múltiples Medicamentos/genética , Variación Genética/genética , Humanos , Klebsiella pneumoniae/genética , Plásmidos/genéticaRESUMEN
OBJECTIVES: The aim of this study was to characterise a KPC-carrying Klebsiella pneumoniae isolate from a Peruvian hospital setting. METHODS: The identity of the isolate was confirmed by amplification and sequencing of the 16S rRNA gene, and the antibiotic resistance profile was determined by disk diffusion and automated methods The sequence type (ST) and phylogenetic group were established by PCR. The presence of different ß-lactamase genes was determined, including blaMBL, blaKPC, blaCTX-M, blaSHV, blaOXA-1-like, blaOXA-2-like, blaOXA-5-like, blaOXA-48-like and blaTEM and up to six different plasmid-encoded AmpC genes as well as class 1 integrons. The conjugability of ß-lactam resistance was assessed by conjugation. RESULTS: The isolate was confirmed to be K. pneumoniae classified as belonging to the KpI phylogenetic group within ST340, which belongs to the high-risk clonal complex 258 (CC258). The isolate was resistant to all ß-lactam agents tested, with only the presence of a non-conjugative blaKPC-2 gene being detected and carried in a non-classical genetic structure. CONCLUSIONS: This is the first description of a member of CC258 and of a blaKPC-2 gene in Peru. Intensive surveillance is needed to determine the relevance of both in this area.
Asunto(s)
Infecciones por Klebsiella/microbiología , Klebsiella pneumoniae/enzimología , Klebsiella pneumoniae/aislamiento & purificación , beta-Lactamasas/metabolismo , Conjugación Genética , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Pruebas Antimicrobianas de Difusión por Disco , Transferencia de Gen Horizontal , Genotipo , Hospitales , Humanos , Integrones , Klebsiella pneumoniae/clasificación , Klebsiella pneumoniae/genética , Tipificación Molecular , Perú , Plásmidos/análisis , Reacción en Cadena de la Polimerasa , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , beta-Lactamasas/genéticaRESUMEN
Infection caused by carbapenem-resistant Klebsiella pneumoniae has become a major healthcare threat and KPC-2 enzyme is a dominant factor mediating carbapenems resistance in K. pneumoniae. This study was designed to determine the genetic environment of blaKPC-2, which prevailed in clinical K. pneumoniae isolates recovered in Huashan Hospital, Shanghai, China. Forty-two clinical isolates were included in this study by blaKPC-2 screening. After multilocus sequence typing and plasmid analyses of PCR-based replicon typing (PBRT), junction PCR, mapping PCR and crossing PCR assays, primer walking, and amplicon sequencing were used to analyze the genetic environment of the blaKPC-2 gene. ST423, ST65, ST977, and ST11 were all detected in KPC-2-producing K. pneumoniae. Two types of blaKPC-2-bearing genetic structure were found: Tn1721-blaKPC-2-Tn3 and Tn1721-blaKPC-2-ΔTn3-IS26; and were carried in IncX and IncFII plasmids, respectively. In conclusion, the genetic environment of the blaKPC-2 gene was diverse and Tn1721-blaKPC-2-ΔTn3-IS26 was dominant in clinical K. pneumoniae isolates in Huashan Hospital. This study sheds some light on the genetic environment and should foster further studies about the mechanism of the blaKPC-2 dissemination.