Genomic Characterization of Two NDM-5-Producing Isolates of Klebsiella pneumoniae ST11 from a Single Patient.

Two metallo-ß-lactamase-producing Klebsiella pneumoniae (HA30 and HA31) were isolated in a hospital in Argentina during 2018. K. pneumoniae HA30 was isolated from a rectal swab during the epidemiological surveillance for carbapenemase-producing strains, while K. pneumoniae HA31 was collected from the same patient 4 days after hospitalization. The aim of the present study was to identify the clonal relationships and resistome of these two NDM-producing K. pneumoniae strains isolated from a patient with a fatal outcome. Whole-genome sequencing (WGS) was performed using Illumina MiSeq-I, and subsequent analysis involved genome assembly, annotation, antibiotic resistance gene identification, multilocus sequence typing (MLST), and plasmid characterization using bioinformatics tools. Conjugation assays to E. coli J53 was conducted as previously described. K. pneumoniae HA30 exhibited extensively drug-resistant phenotype, while HA31 was multidrug-resistant as defined by Magiorakos et al., including both resistance to carbapenems, aminoglycosides and ciprofloxacin with blaNDM-5, blaCTX-M-15 and rmtB genes found in both strains. MLST analysis showed that both strains belonged to ST11, differing by only 4 cgSNPs, indicating that K. pneumoniae HA30 and HA31 were the same strain. Conjugation assays revealed that K. pneumoniae HA31 strain possessed a transferable plasmid to E. coli J53. Bioinformatics studies identified that the same strain colonizing an inpatient during hospital admission subsequently caused the infection leading to a fatal outcome, being the first report of blaNDM-5, rmtB and blaCTX-M-15 genes in a K. pneumoniae ST11 strain from Latin America. Our results also highlighted the importance of focusing on epidemiological surveillance programs.

Antimicrobial resistance dissemination associated with intensive animal production practices in Argentina: A systematic review and meta-analysis.

Abuse and misuse of antimicrobial agents has accelerated the spread of antimicrobial-resistant bacteria. The association between antimicrobial-resistant infections in humans and antimicrobial use in agriculture is complex, but well-documented. This study provides a systematic review and meta-analysis of the dissemination of antimicrobial resistance (AMR) to antimicrobials defined as critically important by the WHO, in swine, chicken, and cattle from intensive and extensive production systems in Argentina. We conducted searches in electronic databases (MEDLINE-PubMed, Web of Science, SciELO, the National System of Digital Repositories from Argentina) as well as in the gray literature. Inclusion criteria were epidemiological studies on AMR in the main food-transmitted bacteria, Salmonella spp., Campylobacter spp., Escherichia coli and Enterococcus spp., and mastitis-causing bacteria, isolated from swine, chicken, dairy and beef cattle from Argentina. This study gives evidence for supporting the hypothesis that AMR of common food-transmitted bacteria in Argentina is reaching alarming levels. Meta-analyses followed by subgroup analyses confirmed the association between the prevalence of AMR and (a) animal species (p<0.01) for streptomycin, ampicillin and tetracycline or (b) the animal production system (p<0.05) for streptomycin, cefotaxime, nalidixic acid, ampicillin and tetracycline. Moreover, swine (0.47 [0.29; 0.66]) and intensive production (0.62 [0.34; 0.83]) showed the highest pooled prevalence of multidrug resistance while dairy (0.056 [0.003; 0.524]) and extensive production (0.107 [0.043; 0.240]) showed the lowest. A research gap regarding beef-cattle from feedlot was identified. Finally, there is an urgent need for political measures meant to coordinate and harmonize AMR surveillance and regulate antimicrobial use in animal production.

Molecular characterization of multidrug-resistant Escherichia coli of the phylogroups A and C in dairy calves with meningitis and septicemia.

Escherichia coli is an important cause of septicemia (SEPEC) and neonatal meningitis (NMEC) in dairy calves. However, the diversity of virulence profiles, phylogroups, antimicrobial resistance patterns, carriage of integron structures, and fluoroquinolone (FQ) resistance mechanisms have not been fully investigated. Also, there is a paucity of knowledge about the virulence profiles and frequency of potential SEPEC in feces from calves with or without diarrhea. This study aimed to characterize the virulence potential, phylogroups, antimicrobial susceptibility, integron content, and FQ-resistance mechanisms in Escherichia coli isolated from calves with meningitis and septicemia. Additionally, the virulence genes (VGs) and profiles of E. coli isolated from diarrheic and non-diarrheic calves were compared between them and together with NMEC and SEPEC in order to identify shared profiles. Tissue and fluid samples from eight dairy calves with septicemia, four of which had concurrent meningitis, were processed for bacteriology and histopathology. Typing of VGs was assessed in 166 isolates from diverse samples of each calf. Selected isolates were evaluated for antimicrobial susceptibility by the disk diffusion test. Phylogroups, integron gene cassettes cartography, and FQ-resistance determinants were analyzed by PCR, sequencing, and bioinformatic tools. Furthermore, 109 fecal samples and 700 fecal isolates from dairy calves with or without diarrhea were evaluated to detect 19 VGs by uniplex PCR. Highly diverse VG profiles were characterized among NMEC and SEPEC isolates, but iucD was the predominant virulence marker. Histologic lesions in all calves supported their pathogenicity. Selected isolates mainly belonged to phylogroups A and C and showed multidrug resistance. Classic (dfrA17 and arr3-dfrA27) and complex (dfrA17-aadA5::ISCR1::blaCTX-M-2) class 1 integrons were identified. Target-site mutations in GyrA (S83L and D87N) and ParC (S80I) encoding genes were associated with FQ resistance. The VGs detected more frequently in fecal samples included f17G (50%), papC (30%), iucD (20%), clpG (19%), eae (16%), and afaE-8 (13%). Fecal isolates displaying the profiles of f17 or potential SEPEC were found in 25% of calves with and without diarrhea. The frequency of E. coli VGs and profiles did not differ between both groups (p > 0.05) and were identical or similar to those found in NMEC and SEPEC. Overall, multidrug-resistant E. coli isolates with diverse VG profiles and belonging to phylogroups A and C can be implicated in natural cases of meningitis and septicemia. Their resistance phenotypes can be partially explained by class 1 integron gene cassettes and target-site mutations in gyrA and parC. These results highlight the value of antimicrobial resistance surveillance in pathogenic bacteria isolated from food-producing animals. Besides, calves frequently shed potential SEPEC in their feces as commensals ("Trojan horse"). Thus, these bacteria may be disseminated in the farm environment, causing septicemia and meningitis under predisposing factors.

Genome analysis of a clinical isolate of Shewanella sp. uncovered an active hybrid integrative and conjugative element carrying an integron platform inserted in a novel genomic locus.

Shewanella spp. are currently considered to be emerging pathogens that can code for a blaOXA carbapenemase in their chromosome. Complete genome analysis of the clinical isolate Shewanella sp. Sh95 revealed that this strain is a novel species, which shares a lineage with marine isolates. Characterization of its resistome showed that it codes for genes drfA15, qacH and blaOXA-48. We propose that Shewanella sp. Sh95 acts as reservoir of blaOXA-48. Moreover, analysis of mobilome showed that it contains a novel integrative and conjugative element (ICE), named ICESh95. Comparative analysis between the close relatives ICESpuPO1 from Shewanella sp. W3-18-1 and ICE SXTMO10 from Vibrio cholerae showed that ICESh95 encompassed two new regions, a type III restriction modification system and a multidrug resistance integron. The integron platform contained a novel arrangement formed by gene cassettes drfA15 and qacH, and a class C-attC group II intron. Furthermore, insertion of ICESh95 occurred at a unique target site, which correlated with the presence of a different xis/int module. Mobility of ICESh95 was assessed and demonstrated its ability to self-transfer with high efficiency to different species of bacteria. Our results show that ICESh95 is a self-transmissible, mobile element, which can contribute to the dissemination of antimicrobial resistance; this is clearly a threat when natural bacteria from water ecosystems, such as Shewanella, act as vectors in its propagation.

Characterization of Tn6238 with a new allele of aac(6')-Ib-cr.

Here, we report that the genetic structure of Tn1331 remained conserved in Argentina from 1989 to 2013 (72 of 73 isolates), with the exception being the plasmid-borne Tn1331-like transposon Tn6238 containing a new aac(6')-Ib-cr allele recovered from a colistin-resistant Klebsiella pneumoniae clinical isolate. A bioinformatic analysis of aac(6')-Ib-like gene cassettes suggests that this new aac(6')-Ib-cr allele emerged through mutation or homologous recombination in the Tn1331 genetic platform. Tn6238 is a novel platform for the dissemination of aminoglycoside and fluoroquinolone resistance determinants.

Presence of OXA-type enzymes in Achromobacter insuavis and A. dolens.

The accurate species identification of Achromobacter isolates is difficult and the clinical isolates of this genus are mostly referred as A. xylosoxidans. Here, we report new OXA variants in 2 isolates identified as A. insuavis (A114, A79) and 1 isolate identified as A. dolens (A336). These results suggest that different bla OXA genes are ubiquitous in the different species of Achromobacter spp. The role of the other species of Achromobacter in clinical samples needs to be reevaluated, and the proper identification is absolutely necessary to understand the epidemiology of this genus.

Sporadic clone Escherichia coli ST615 as a vector and reservoir for dissemination of crucial antimicrobial resistance genes.

There is scarce information concerning the role of sporadic clones in the dissemination of antimicrobial resistance genes (ARGs) within the nosocomial niche. We confirmed that the clinical Escherichia coli M19736 ST615 strain, one of the first isolates of Latin America that harbors a plasmid with an mcr-1 gene, could receive crucial ARG by transformation and conjugation using as donors critical plasmids that harbor bla CTX-M-15, bla KPC-2, bla NDM-5, bla NDM-1, or aadB genes. Escherichia coli M19736 acquired bla CTX-M-15, bla KPC-2, bla NDM-5, bla NDM-1, and aadB genes, being only blaNDM-1 maintained at 100% on the 10th day of subculture. In addition, when the evolved MDR-E. coli M19736 acquired sequentially bla CTX-M-15 and bla NDM-1 genes, the maintenance pattern of the plasmids changed. In addition, when the evolved XDR-E. coli M19736 acquired in an ulterior step the paadB plasmid, a different pattern of the plasmid's maintenance was found. Interestingly, the evolved E. coli M19736 strains disseminated simultaneously the acquired conjugative plasmids in different combinations though selection was ceftazidime in all cases. Finally, we isolated and characterized the extracellular vesicles (EVs) from the native and evolved XDR-E. coli M19736 strains. Interestingly, EVs from the evolved XDR-E. coli M19736 harbored bla CTX-M-15 though the pDCAG1-CTX-M-15 was previously lost as shown by WGS and experiments, suggesting that EV could be a relevant reservoir of ARG for susceptible bacteria. These results evidenced the genetic plasticity of a sporadic clone of E. coli such as ST615 that could play a relevant transitional link in the clinical dynamics and evolution to multidrug/extensively/pandrug-resistant phenotypes of superbugs within the nosocomial niche by acting simultaneously as a vector and reservoir of multiple ARGs which later could be disseminated.

Emergence and spread of plasmid-borne tet(B)::ISCR2 in minocycline-resistant Acinetobacter baumannii isolates.

Resistance to minocycline has emerged in multidrug-resistant Acinetobacter baumannii isolates from Buenos Aires hospitals. Few reports about the description and dispersion of tet genes in this species have been published. We observed the presence of tet(B) in all minocycline-resistant isolates. This gene was found to be associated with the ISCR2 mobile element, which may, in part, explain its dispersion.

Outbreak of extensively drug-resistant Acinetobacter baumannii indigo-pigmented strains.

Acinetobacter baumannii pigmented strains are not common in clinical settings. Here, we report an outbreak caused by indigo-pigmented A. baumannii strains isolated in an acute care hospital in Argentina from March to September 2012. Pan-PCR assays exposed a unique pattern belonging to the recently described regional CC113(B)/CC79(P) clonal complex that confirms the relevant relationships among the indigo-pigmented A. baumannii strains. All of them were extensively drug resistant and harbored different genetic elements associated with horizontal genetic transfer, such as the transposon Tn2006, class 2 integrons, AbaR-type islands, IS125, IS26, strA, strB, florR, and the small recombinase ISCR2 associated with the sul2 gene preceded by ISAba1.

Outbreak of a cluster with epidemic behavior due to Serratia marcescens after colistin administration in a hospital setting.

Serratia marcescens causes health care-associated infections with important morbidity and mortality. Particularly, outbreaks produced by multidrug-resistant isolates of this species, which is already naturally resistant to several antibiotics, including colistin, are usually described with high rates of fatal outcomes throughout the world. Thus, it is important to survey factors associated with increasing frequency and/or emergence of multidrug-resistant S. marcescens nosocomial infections. We report the investigation and control of an outbreak with 40% mortality due to multidrug-resistant S. marcescens infections that happened from November 2007 to April 2008 after treatment with colistin for Acinetobacter baumannii meningitis was started at hospital H1 in 2005. Since that year, the epidemiological pattern of frequently recovered species has changed, with an increase of S. marcescens and Proteus mirabilis infections in 2006 in concordance with a significant decrease of the numbers of P. aeruginosa and A. baumannii isolates. A single pulsed-field gel electrophoresis (PFGE) cluster of S. marcescens isolates was identified during the outbreak. When this cluster was compared with S. marcescens strains (n = 21) from 10 other hospitals (1997 to 2010), it was also identified in both sporadic and outbreak isolates circulating in 4 hospitals in Argentina. In132::ISCR1::blaCTX-M-2 was associated with the multidrug-resistant cluster with epidemic behavior when isolated from outbreaks. Standard infection control interventions interrupted transmission of this cluster even when treatment with colistin continued in several wards of hospital H1 until now. Optimizing use of colistin should be achieved simultaneously with improved infection control to prevent the emergence of species naturally resistant to colistin, such as S. marcescens and P. mirabilis.

Spreading of AbaR-type genomic islands in multidrug resistance Acinetobacter baumannii strains belonging to different clonal complexes.

In order to determine the occurrence of AbaR-type genomic island in multidrug resistant Acinetobacter baumannii (MDRAb) strains circulating in Argentina, Uruguay, and Chile, we studied 51 MDRAb isolates recovered from several hospitals over 30 years. AbaR-type genomic resistance islands were found in 36 MDRAb isolates since 1986 till now. MLST technique allowed us to identify the presence of four different Clonal Complexes (109, 104, 119, 113) among the positive AbaR-type island positive strains. This is the first description of AbaR-type islands in the CC104 and CC113 that are the most widespread Clonal Complexes in Argentina. In addition, PCR mapping exposed different arrays to those previously described, evidencing the plasticity of this island. Our results evidence a widespread distribution of the AbaR-type genomic islands along the time in the MDRAb population, including the epidemic global clone 1 (GC1) as well as different clonal complexes to those already described in the literature.

Distribution of allelic variants of the chromosomal gene bla OXA-114-like in Achromobacter xylosoxidans clinical isolates.

Achromobacter xylosoxidans is increasingly being documented in cystic fibrosis patients. The bla(OXA-114) gene has been recognized as a naturally occurring chromosomal gene, exhibiting different allelic variants. In the population under study, the bla(OXA-114)-like gene was found in 19/19 non-epidemiological-related clinical isolates of A. xylosoxidans with ten different alleles including 1 novel OXA-114 variant.

Identification of a Specific Biomarker of Acinetobacter baumannii Global Clone 1 by Machine Learning and PCR Related to Metabolic Fitness of ESKAPE Pathogens.

Since the emergence of high-risk clones worldwide, constant investigations have been undertaken to comprehend the molecular basis that led to their prevalent dissemination in nosocomial settings over time. So far, the complex and multifactorial genetic traits of this type of epidemic clones have allowed only the identification of biomarkers with low specificity. A machine learning algorithm was able to recognize unequivocally a biomarker for early and accurate detection of Acinetobacter baumannii global clone 1 (GC1), one of the most disseminated high-risk clones. A support vector machine model identified the U1 sequence with a length of 367 nucleotides that matched a fragment of the moaCB gene, which encodes the molybdenum cofactor biosynthesis C and B proteins. U1 differentiates specifically between A. baumannii GC1 and non-GC1 strains, becoming a suitable biomarker capable of being translated into clinical settings as a molecular typing method for early diagnosis based on PCR as shown here. Since the metabolic pathways of Mo enzymes have been recognized as putative therapeutic targets for ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens, our findings highlight that machine learning can also be useful in knowledge gaps of high-risk clones and provides noteworthy support to the literature to identify relevant nosocomial biomarkers for other multidrug-resistant high-risk clones. IMPORTANCE A. baumannii GC1 is an important high-risk clone that rapidly develops extreme drug resistance in the nosocomial niche. Furthermore, several strains have been identified worldwide in environmental samples, exacerbating the risk of human interactions. Early diagnosis is mandatory to limit its dissemination and to outline appropriate antibiotic stewardship schedules. A region with a length of 367 bp (U1) within the moaCB gene that is not subjected to lateral genetic transfer or to antibiotic pressures was successfully found by a support vector machine model that predicts A. baumannii GC1 strains. At the same time, research on the group of Mo enzymes proposed this metabolic pathway related to the superbug's metabolism as a potential future drug target site for ESKAPE pathogens due to its central role in bacterial fitness during infection. These findings confirm that machine learning used for the identification of biomarkers of high-risk lineages can also serve to identify putative novel therapeutic target sites.

Comparative genome analysis of the genus Shewanella unravels the association of key genetic traits with known and potential pathogenic lineages.

Shewanella spp. are Gram-negative rods widely disseminated in aquatic niches that can also be found in human-associated environments. In recent years, reports of infections caused by these bacteria have increased significantly. Mobilome and resistome analysis of a few species showed that they are versatile; however, comprehensive comparative studies in the genus are lacking. Here, we analyzed the genetic traits of 144 genomes from Shewanella spp. isolates focusing on the mobilome, resistome, and virulome to establish their evolutionary relationship and detect unique features based on their genome content and habitat. Shewanella spp. showed a great diversity of mobile genetic elements (MGEs), most of them associated with monophyletic lineages of clinical isolates. Furthermore, 79/144 genomes encoded at least one antimicrobial resistant gene with their highest occurrence in clinical-related lineages. CRISPR-Cas systems, which confer immunity against MGEs, were found in 41 genomes being I-E and I-F the more frequent ones. Virulome analysis showed that all Shewanella spp. encoded different virulence genes (motility, quorum sensing, biofilm, adherence, etc.) that may confer adaptive advantages for survival against hosts. Our data revealed that key accessory genes are frequently found in two major clinical-related groups, which encompass the opportunistic pathogens Shewanella algae and Shewanella xiamenensis together with several other species. This work highlights the evolutionary nature of Shewanella spp. genomes, capable of acquiring different key genetic traits that contribute to their adaptation to different niches and facilitate the emergence of more resistant and virulent isolates that impact directly on human and animal health.

Replacement of KPC-producing pandemic lineages and dissemination of plasmids associated with antimicrobial resistance determinants during inpatient's hospitalization.

OBJECTIVES: The emergence of blaKPC-2 within nosocomial settings has become a major public health crisis worldwide. Our aim was to perform whole-genome sequencing (WGS) of three KPC-producing Gram-negative bacilli (KPC-GNB) strains isolated from a hospitalized patient to identify acquired antimicrobial resistance genes (ARGs). METHODS: WGS was performed using Illumina MiSeq-I, and de novo assembly was achieved using SPAdes. Bioinformatics analysis was done using Resfinder, AMRFinder, ISFinder, plasmidSPAdes, PlasmidFinder, MOB-suite, PLSDB database, and IntegronFinder. Conjugation assays were performed to assess the ability of blaKPC-2 to transfer via a plasmid-related mobilization mechanism. RESULTS: High-risk clone KPC-producing Klebsiella pneumoniae sequence type (ST) 258 (HA3) was colonizing an inpatient who later was infected by KPC-producing Escherichia coli ST730 (HA4) and subsequently by KPC-producing K. pneumoniae ST11 (HA15) during hospitalization. Although belonging to different species, both strains causing infections harbored the same gene configuration for dissemination of blaKPC-2 in related IncM1 plasmids recently found in other KPC-GNB isolated from Hospital Alemán at Ciudad Autónoma de Buenos Aires. Conjugation assays revealed that only pDCVEA4-KPC from E. coli HA4 was successfully transferred with a conjugation frequency of 3.66 × 101. CONCLUSIONS: Interchange of multidrug-resistant K. pneumoniae lineages ST258 replaced by ST11 in the framework of colonization and infection by KPC-GNB of an inpatient from our institution was found. In addition, the transfer of the gene configuration of blaKPC-2 between infecting strains may have occurred in the nosocomial environment, but we cannot rule out that the event took place in vivo, within the patient, during hospitalization.

Genomic data reveals the emergence of the co-occurrence of blaKPC-2 and blaCTX-M-15 in an Escherichia coli ST648 strain isolated from rectal swab within the framework of hospital surveillance.

OBJECTIVES: The worldwide dissemination of carbapenemase-producing Escherichia coli lineages belonging to high-risk clones poses a challenging public health menace. The aim of this work was to investigate genomic features of a colonizing multidrug-resistant strain of Klebsiella pneumoniae carbapenemase (KPC)-producing E. coli from our institution. METHODS: Whole-genome sequencing was done by Illumina MiSeq-I, and de novo assembly was achieved using SPAdes. Resistome, mobilome, plasmids, virulome, and integrons were analysed using ResFinder, AMRFinder, ISFinder, PlasmidFinder, MOB-suite, VirulenceFinder, and IntegronFinder. Sequence types (STs) were identified with pubMLST and BIGSdb databases. Conjugation assays were also performed. RESULTS: Escherichia coli HA25pEc was isolated from a rectal swab sample taken within the framework of the hospital epidemiological surveillance protocol for detection of carbapenemase-producing Enterobacterales. Escherichia coli HA25pEc corresponded to the first report of ST648 co-harbouring blaKPC-2 and blaCTX-M-15 in Latin America from a colonized patient. It had 19 antibiotic resistance genes (ARGs), including blaKPC-2, located on a Tn4401a isoform. Conjugation assays revealed that blaKPC-2 was not transferred by conjugation to E. coli J53 under our experimental conditions. CONCLUSION: Escherichia coli ST648 has been detected previously in companion and farm animals as well as in hospital- and community-acquired infections worldwide. Although scarcely reported as KPC-producers, our finding in a culture surveillance with several acquired ARGs, including blaCTX-M-15, alerts the potential of this clone for worldwide unnoticed spreading of extreme drug resistance to ß-lactams. These data reinforce the importance of carrying out molecular surveillance to identify reservoirs and warn about the dissemination of new international clones in carbapenemase-bearing patients.

The Acinetobacter baumannii website (Ab-web): a multidisciplinary knowledge hub, communication platform, and workspace.

Acinetobacter baumannii is a Gram-negative bacterium increasingly implicated in hospital-acquired infections and outbreaks. Effective prevention and control of such infections are commonly challenged by the frequent emergence of multidrug-resistant strains. Here we introduce Ab-web (https://www.acinetobacterbaumannii.no), the first online platform for sharing expertise on A. baumannii. Ab-web is a species-centric knowledge hub, initially with 10 articles organized into two main sections, 'Overview' and 'Topics', and three themes, 'epidemiology', 'antibiotic resistance', and 'virulence'. The 'workspace' section provides a spot for colleagues to collaborate, build, and manage joint projects. Ab-web is a community-driven initiative amenable to constructive feedback and new ideas.

Class 2 integrons dissemination among multidrug resistance (MDR) clones of Acinetobacter baumannii.

Acinetobacter baumannii has emerged as a serious problem in the hospital environment at a global scale. Previous results from our laboratory showed a high frequency of class 2 integrons in A. baumannii strains from Argentina regarding the low rate of this element in A. baumannii isolates from the rest of the world. To reveal the current epidemiology of class 2 integrons, a molecular surveillance analyzing 78 multidrug resistant (MDR) A. baumannii isolates from Argentina and Uruguay was performed, exposing the presence of class 2 integron in the 36.61% of the isolates. Class 2 integron characterization showed that the typical Tn7::In2-7 array was present in 26 out of 27 intI2 positive isolates. All intI2 positive isolates contained at least one of the Tn7 transposition genes. In addition, we identified that 18 intI2 positive isolates possessed the Tn7::In2-7 within the attTn7 site. The molecular typing evidenced that clones I and IV that do not belong to widespread European clones I and II were found among the intI2 positive isolates. Our results exposed the widely dissemination of class 2 integron among MDR A. baumannii isolates from Argentina and Uruguay, also showing the persistence of two novel clones in our region, which could explain in part the high frequency of class 2 integron found in our region.

Acinetobacter baumannii is able to gain and maintain a plasmid harbouring In35 found in Enterobacteriaceae isolates from Argentina.

The aim of this study was to determine the presence of bla (CTX-M-2) in our A. baumannii population and their putative role as an alternative mechanism of resistance to third-generation cephalosporins in this species. The bla (CTX-M-2) gene is widespread among the Enterobacteriaceae isolates from our country; however, it was not found in 76 isolates A. baumannii non-epidemiologically related clinical isolates resistant to third-generation cephalosporins isolated since 1982 in hospitals from Buenos Aires City. A plasmid isolated from Proteus mirabilis that possesses the complex class 1 integron In35::ISCR1::bla (CTX-M-2) was used to transform the natural competent A. baumannii clinical strain A118. PCR, plasmid extraction, DNA restriction, and susceptibility test confirmed that A118 could gain and maintain the plasmid possessing In35::ISCR1::bla (CTX-M-2), the genetic platform where the bla (CTX-M-2) gene is dispersing in Argentina.

Achromobacter xylosoxidans: an emerging pathogen carrying different elements involved in horizontal genetic transfer.

In the last few years, numerous cases of multidrug-resistant Achromobacter xylosoxidans infections have been documented in immunocompromised and cystic fibrosis patients. To gain insights into the molecular mechanisms and mobile elements related to multidrug resistance in this bacterium, we studied 24 non-epidemiological A. xylosoxidans clinical isolates from Argentina. Specific primers for plasmids, transposons, insertion sequences, bla(ampC), intI1, and intI2 genes were used in PCR reactions. The obtained results showed the presence of wide host range IncP plasmids in ten isolates and a high dispersion of class 1 integrons (n = 10) and class 2 integrons (n = 3). Four arrays in the variable region (vr) of class 1 integrons were identified carrying different gene cassettes as the aminoglycoside resistance aac(6')-Ib and aadA1, the trimethoprim resistance dfrA1 and dfrA16, and the ß-lactamase bla(OXA-2). In only one of the class 2 integrons, a vr was amplified that includes sat2-aadA1. The bla(ampC) gene was found in all isolates, confirming its ubiquitous nature. Our results show that A. xylosoxidans clinical isolates contain a rich variety of genetic elements commonly associated with resistance genes and their dissemination. This supports the hypothesis that A. xylosoxidans is becoming a reservoir of horizontal genetic transfer elements commonly involved in spreading antibiotic resistance.