Genetic Alterations Associated with Polymyxin B Resistance in Nosocomial KPC-2-Producing Klebsiella pneumoniae from Brazil.

The rapid increased multidrug resistance in Klebsiella pneumoniae has led to a renewed interest in polymyxin antibiotics, such as colistin, as antibiotics of last resort, not least in low/middle income countries. We conducted a genomic survey of clinical polymyxin-resistant K. pneumoniae to investigate the genetic alterations in isolates harboring blaKPC-2. Whole-genome sequencing was performed using an Illumina NextSeq 500 paired-end reads. Mutations and insertion sequence detection were analyzed to seven isolates recovered from clinical specimens of patients hospitalized in Brazil, focusing on key genes associated with polymyxin resistance. Furthermore, the levels of mRNA expression of genes associated with resistance to polymyxin B and other antimicrobials were evaluated by quantitative real-time PCR. Eighty-five percent of the isolates were assigned to clonal complex 258, with a minimum inhibitory concentration range of 4 to >256 mg/L for polymyxin B. It was possible to observe the presence of one important insertion element, ISKpn13, in a strain recovered from the blood that have blaKPC-2. Deleterious mutations reported in PmrB (R256G), YciM (N212T), and AcrB (T598A) were common, and mobile colistin resistance (mcr) genes were absent in all the isolates. RT-qPCR analysis revealed an overexpression of the pmrC (1.160-fold), pmrD (2.258-fold), and kpnE (1.530-fold) genes in the polymyxin B-resistant isolates compared with the expression of the polymyxin B-susceptible K. pneumoniae isolate. Overall, these results demonstrate the diversity of genetic variations in polymyxin-resistant populations derived from the different clonal strains, but the same sequence types, and suggest that there are still unknown mechanisms of polymyxin resistance in K. pneumoniae.

High mortality by nosocomial infections caused by carbapenem-resistant P. aeruginosa in a referral hospital in Brazil: facing the perfect storm.

Introduction. Carbapenem-resistant Pseudomonas aeruginosa is responsible for increased patient mortality.Gap Statement. Five and 30 day in-hospital all-cause mortality in patients with P. aeruginosa infections were assessed, followed by evaluations concerning potential correlations between the type III secretion system (TTSS) genotype and the production of metallo-ß-lactamase (MBL).Methodology. This assessment comprised a retrospective cohort study including consecutive patients with carbapenem-resistant infections hospitalized in Brazil from January 2009 to June 2019. PCR analyses were performed to determine the presence of TTSS-encoding genes and MBL genes.Results. The 30-day and 5-day mortality rates for 262 patients were 36.6 and 17.9 %, respectively. The unadjusted survival probabilities for up to 5 days were 70.55 % for patients presenting exoU-positive isolates and 86 % for those presenting exo-negative isolates. The use of urinary catheters, as well as the presence of comorbidity conditions, secondary bacteremia related to the respiratory tract, were independently associated with death at 5 and 30 days. The exoS gene was detected in 64.8 % of the isolates, the presence of the exoT and exoY genes varied and exoU genes occurred in 19.3 % of the isolates. The exoU genotype was significantly more frequent among multiresistant strains. MBL genes were not detected in 92 % of the isolates.Conclusions. Inappropriate therapy is a crucial factor regarding the worse prognosis among patients with infections caused by multiresistant P. aeruginosa, especially those who died within 5 days of diagnosis, regardless of the genotype associated with TTSS virulence.

Novel small IncX3 plasmid carrying the blaKPC-2 gene in high-risk Klebsiella pneumoniae ST11/CG258.

This study used whole-genome sequencing (WGS) and PFGE to analysis KPC-2-producing Klebsiella pneumoniae strains from clinical specimens collected in Brazilian hospitals. The study identifies the emergence of a novel small IncX3 plasmid (pKPB11), 12,757-bp in length, in a high-risk K. pneumoniae ST11/CG258 lineage, a successful clonal group in Brazil, carrying the blaKPC-2 gene on a non-Tn4401 genetic element (NTEKPC-Ic). Comparative analysis of the pKPB11 showed that this plasmid reduced its size, losing part of its conjugation apparatus. The pKPB11 was also compared to another strain sequenced in this study (KPC89) that had the hybrid IncX3-IncU plasmid (pKP89), of approximately 45 kb in length, similarly carrying the blaKPC-2 gene on NTEKPC-Ic. To the best of our knowledge, pKPB11 is the first example of small IncX3 plasmid found in a high-risk KPC-2-producing K. pneumoniae ST11/CG258.

Incidence of infections caused by carbapenem-resistant Acinetobacter baumannii.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii (CR-Ab) has become a worrying health care problem, mainly in developing countries, such as Brazil. The objective was to investigate the prevalence and prognostic factors for CR-Ab infections at a Brazilian university hospital and examine the impact of inappropriate antimicrobial therapy on patient outcome. METHODS: A retrospective study on hospitalized patients with CR-Ab infections was carried out from January 2013 to December 2017. An epidemiologic analysis was carried out to determine the frequency of infections, the epidemiologic indicators by year, the risk factors for 30-day mortality, and the impact of inappropriate therapy. RESULTS: A total of 489 patients were included in the study. A rate of 0.7 per 1,000 patient-day CR-Ab infections was observed, mostly in the lungs (54.7%), and predominantly in the adult intensive care unit. The occurrence of infections by CR-Ab per 1,000 patient-days in November 2014 exceeded the established control limit, confirming an outbreak. CONCLUSIONS: The prevalence of CR-Ab increased in the investigated hospital, passing to an endemic pathogen with a direct impact on mortality and the control of these strains.

Molecular Detection of Class 1 Integron-Associated Gene Cassettes in KPC-2-Producing Klebsiella pneumoniae Clones by Whole-Genome Sequencing.

The dissemination of antimicrobial resistance genes and the bacterium that harbor them have increasingly become a public concern, especially in low- and middle-income countries. The present study used whole-genome sequencing to analyze 10 KPC-2-producing Klebsiella pneumoniae isolates obtained from clinical specimens originated from Brazilian hospitals. The study documents a relevant "snapshot" of the presence of class 1 integrons in 90% of the strains presenting different gene cassettes (dfrA30, dfrA15, dfrA12, dfrA14, aadA1, aadA2, and aac(6')Iq), associated or not with transposons. Two strains presented nonclassical integron (lacking the normal 3'conserved segment). In general, most strains showed a complex resistome, characterizing them as highly resistant. Integrons, a genetically stable and efficient system, confer to bacteria as highly adaptive and low cost evolution potential to bacteria, even more serious when associated with high-risk clones, indicating an urgent need for control and prevention strategies to avoid the spread of resistance determinants in Brazil. Despite this, although the class 1 integron identified in the KPC-2-producing K. pneumoniae clones is important, our findings suggest that other elements probably have a greater impact on the spread of antimicrobial resistance, since many of these important genes were not related to this cassette.

Molecular characterization and clonal dynamics of nosocomial blaOXA-23 producing XDR Acinetobacter baumannii.

The emergence of infections associated to new antimicrobial resistance in Acinetobacter baumannii (Ab) genotypes represents a major challenge. In this context, this study aimed to determine the diversity of resistance mechanisms and investigate clonal dissemination and predominant sequence types (STs) in multidrug-resistant Ab strains of clinical (tracheal aspirate, n = 17) and environmental (surface, n = 6) origins. Additionally, the major clones found in clinical (A) and environmental (H) strains had their complete genomes sequenced. All strains were submitted to polymerase chain reactions (PCR) for the detection of the ISAba1/blaOXA-51-like and ISAba1/blaOXA-23-like genes, while the expression of genes encoding the carO porin, AdeABC (adeB), AdeFGH (adeG), and AdeIJK (adeJ) efflux pumps was determined by real time PCR (qPCR). Most of the strains were characterized as extensively drug-resistant (XDR) with high minimal inhibitory concentrations (MICs) detected for tigecycline and carbapenems. Associations between ISAba1/OXA-51 and ISAba1/OXA-23 were observed in 91.3% and 52.2% of the strains, respectively. Only the adeB gene was considered hyper-expressed. Furthermore, most of the strains analyzed by the MuLtilocus Sequence-Typing (MLST) were found to belong to the clonal complex 113 (CC113). In addition, a new ST, ST1399, belonging to CC229, was also discovered herein. Strains analyzed by whole genome sequencing presented resistance genes linked to multidrug-resistance phenotypes and confirmed the presence of Tn2008, which provides high levels carbapenem-resistance.

Association of Colistin-Resistant KPC Clonal Strains with Subsequent Infections and Colonization and Biofilm Production.

Carbapenemase-producing organisms are pandemic and a significant threat to public health. We investigated the clonal relatedness of colistin-resistant Klebsiella pneumoniae strains producing KPC-type carbapenemase (KPC-KP) causing subsequent infections or colonization. Moreover, we aimed to gain insight into the ability of biofilm production in K. pneumoniae strains producing carbapenemase. Twenty-two consecutive KPC-KP and one KPC-negative strain was identified from an adult intensive care unit in Brazil. Seventy-five percent of isolates that harbored the blaKPC gene exhibited genetic relatedness by pulsed-field gel electrophoresis, and none presented the plasmid-mediated mcr-1 and blaNDM genes. This study showed that the majority of repeated KPC infections in adults were caused by a clone that caused the previous infections/colonizations even after a long period of time and illustrates the capacity of multiple clones producing biofilms to coexist in the same patient at the same time, becoming a reservoir of KPC-KP in the hospital environment.

Hypervirulence and biofilm production in KPC-2-producing Klebsiella pneumoniae CG258 isolated in Brazil.

In this study, we describe the frequency of virulence genes in Klebsiella pneumoniae carbapenemase-2-producing Klebsiella pneumoniae (KPC-KP), including hypervirulent (hv) and hypermucoviscous (hm) strains by whole-genome sequencing. We also evaluate the capacity for biofilm formation by using phenotypic techniques. The occurrence of several virulence genes (fimABCDEFGHIK, mrkABCDFHJ, ecpA, wabG, entB, ugE, irp1, irp2, traT, iutA and ureADE) and a high frequency of hvhmKPC-KP isolates was found. Most hospital-associated lineages of KPC-KP belong to the international clonal group 258 (CG258). Biofilm formation was a constant feature among 90.9 % of KPC-KP strains. This report suggests a close relationship between ST437 and weak biofilm production, given that all weakly biofilm-producing strains belonged to this sequence type. This also supports the dissemination of KPC-KP containing numerous virulence determinants belonging to the biofilm-producing CG258 type in Brazil, including hv and hm strains. These factors allow this pathogen to cause infections, leading to its rapid expansion and persistence in hospital settings.

High frequency of the combined presence of QRDR mutations and PMQR determinants in multidrug-resistant Klebsiella pneumoniae and Escherichia coli isolates from nosocomial and community-acquired infections.

Plasmid-mediated quinolone resistance (PMQR) determinants combined with mutations in quinolone resistance-determining regions (QRDRs) and clonal dissemination were investigated in 40 fluoroquinolone-resistant Klebsiella pneumoniae and Escherichia coli isolates from nosocomial and community-acquired infections. We observed nucleotide substitutions in gyrA (Ser83Ile, Val37Leu, Lys154Arg, Ser171Ala, Ser19Asn, Ile198Val, Ser83Tyr, Ser83Leu, Asp87Asn and Asp87Gly) and parC genes (Ser80Ile, Glu84Lys, Ala129Ser, Val141Ala and Glu84Gly). Two novel substitutions were detected in the gyrA gene (Val37Leu and Ile198Val). The presence of PMQR genes predominated in community isolates (55.5 %). In addition to the frequent presence of the class 1 integron in isolates from community-acquired infections, the genetic similarity results obtained by PFGE showed high genomic diversity. This study suggests that management of multidrug-resistant Enterobacteriaceae isolates from the community are a possible source of genetic mobile elements that carry genes that confer resistance to fluoroquinolones. More attention should be paid to the surveillance of community-acquired infections.

Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation

Abstract Pseudomonas aeruginosa is an opportunistic pathogen that causes frequently nosocomial infections, currently becoming more difficult to treat due to the various resistance mechanisms and different virulence factors. The purpose of this study was to determine the risk factors independently associated with the development of bacteremia by carbapenem-resistant P. aeruginosa, the frequency of virulence genes in metallo-β-lactamases producers and to evaluate their ability to produce biofilm. We conducted a case–control study in the Uberlândia Federal University – Hospital Clinic, Brazil. Polymerase Chain Reaction was performed for metallo-β-lactamases and virulence genes. Adhesion and biofilm assays were done by quantitative tests. Among the 157 strains analyzed, 73.9% were multidrug-resistant, 43.9% were resistant to carbapenems, 16.1% were phenotypically positive for metallo-β-lactamases, and of these, 10.7% were positive for blaSPM gene and 5.3% positive for blaVIM. The multivariable analysis showed that mechanical ventilation, enteral/nasogastric tubes, primary bacteremia with unknown focus, and inappropriate therapy were independent risk factors associated with bacteremia. All tested strains were characterized as strongly biofilm producers. A higher mortality was found among patients with bacteremia by carbapenem-resistant P. aeruginosa strains, associated independently with extrinsic risk factors, however it was not evident the association with the presence of virulence and metallo-β-lactamases genes.

Molecular epidemiological survey of bacteremia by multidrug resistant Pseudomonas aeruginosa: the relevance of intrinsic resistance mechanisms.

The bacterial factors associated with bacteremia by multidrug-resistant and extensively drug-resistant P. aeruginosa, including overexpression of efflux pumps, AmpC overproduction, and loss/alteration of the OprD porin in isolates that are non-Metallo-ß-Lactamase producing were analyzed in a retrospective study. Molecular analyses included strain typing by Pulsed Field Gel Electrophoresis and identification of key genes via qualitative and quantitative PCR-based assays. Previous use of carbapenems and tracheostomy was independently associated with the development of bacteremia by extensively drug-resistant and multidrug-resistant strains of P. aeruginosa. A high consumption of antimicrobials was observed, and 75.0% of the isolates contained amplicons with the blaSPM-1 and blaVIM genes. Of the 47 non-Metallo-ß-Lactamase isolates, none had another type of carbapenemase. However, the isolates exhibited high rates of hyperproduction of AmpC, loss of the OprD porin (71.4%) and the presence of MexABOprM (57.1%) and MexXY (64.3%). This study suggests that in non-Metallo-ß-Lactamase isolates, the association of intrinsic resistance mechanisms could contributes to the expression of multidrug-resistant/extensively drug-resistant phenotypes.

Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation.

Pseudomonas aeruginosa is an opportunistic pathogen that causes frequently nosocomial infections, currently becoming more difficult to treat due to the various resistance mechanisms and different virulence factors. The purpose of this study was to determine the risk factors independently associated with the development of bacteremia by carbapenem-resistant P. aeruginosa, the frequency of virulence genes in metallo-ß-lactamases producers and to evaluate their ability to produce biofilm. We conducted a case-control study in the Uberlândia Federal University - Hospital Clinic, Brazil. Polymerase Chain Reaction was performed for metallo-ß-lactamases and virulence genes. Adhesion and biofilm assays were done by quantitative tests. Among the 157 strains analyzed, 73.9% were multidrug-resistant, 43.9% were resistant to carbapenems, 16.1% were phenotypically positive for metallo-ß-lactamases, and of these, 10.7% were positive for blaSPM gene and 5.3% positive for blaVIM. The multivariable analysis showed that mechanical ventilation, enteral/nasogastric tubes, primary bacteremia with unknown focus, and inappropriate therapy were independent risk factors associated with bacteremia. All tested strains were characterized as strongly biofilm producers. A higher mortality was found among patients with bacteremia by carbapenem-resistant P. aeruginosa strains, associated independently with extrinsic risk factors, however it was not evident the association with the presence of virulence and metallo-ß-lactamases genes.

Clinical and Molecular Epidemiology of Multidrug-Resistant P. aeruginosa Carrying aac(6')-Ib-cr, qnrS1 and blaSPM Genes in Brazil.

We described a comprehensive analysis of the molecular epidemiology of multidrug-resistant (MDR) P. aeruginosa. Molecular analysis included typing by Pulsed Field Gel Electrophoresis, identification of genes of interest through PCR-based assays and sequencing of target genes. Case-control study was conducted to better understand the prognostic of patients and the impact of inappropriate therapy in patients with bacteremia, as well as the risk factors of MDR infections. We observed a high rate of MDR isolates (40.7%), and 51.0% of them was independently associated with inappropriate antibiotic therapy. Bacteremia was detected in 66.9% of patients, and prolonged hospital stay was expressive in those resistant to fluoroquinolone. Plasmid-mediated quinolone resistance genes (PMQR), qnrS1 and aac(6')Ib-cr, were detected in two different nosocomial isolates (5.3%), and the aac(6')-Ib7 variant was detected at a high frequency (87.5%) in those negative to PMQR. The presence of mutations in gyrA and parC genes was observed in 100% and 85% of selected isolates, respectively. Isolates harboring PMQR genes or mutations in gyrA and parC were not closely related, except in those containing SPM (São Paulo metallo-ß-lactamase) clone. In addition, there is no study published in Brazil to date reporting the presence of Pseudomonas aeruginosa isolates harboring both qnrS1 and aac(6')Ib-cr genes, with alarming frequency of patients with inappropriate therapy.

Molecular epidemiological survey of the quinolone- and carbapenem-resistant genotype and its association with the type III secretion system in Pseudomonas aeruginosa.

This study evaluated the predictors of mortality and the impact of inappropriate therapy on the outcomes of patients with bacteraemia and ventilator-associated pneumonia (VAP). Additionally, we evaluated the correlation of the type III secretion system (TTSS) effector genotype with resistance to carbapenems and fluoroquinolones, mutations in the quinolone resistance-determining regions (QRDRs), metallo-ß-lactamase and virulence factors. A retrospective cohort was conducted at a tertiary hospital in patients with multidrug-resistant (MDR) P. aeruginosa bacteraemia (157 patients) and VAP (60 patients). The genes for blaIMP, blaVIM, blaSIM, blaGIM and blaSPM and virulence genes (exoT, exoS, exoY, exoU, lasB, algD and toxA) were detected; sequencing was conducted for QRDR genes on fluoroquinolone-resistant strains. The multivariate analyses showed that the predictors independently associated with death in patients with bacteraemia were cancer and inappropriate therapy. Carbapenem resistance was more frequent among strains causing VAP (53.3 %), and in blood we observed the blaSPM genotype (66.6 %) and blaVIM genotype (33.3 %). The exoS gene was found in all isolates, whilst the frequency was low for exoU (9.4 %). Substitution of threonine to isoleucine at position 83 in gyrA was the most frequent mutation among fluoroquinolone-resistant strains. Our study showed a mutation at position 91 in the parC gene (Glu91Lys) associated with a mutation in gyrA (Thre83Ile) in a strain of extensively drug-resistant P. aeruginosa, with the exoT(+)exoS(+)exoU(+) genotype, that has not yet been described in Brazil to the best of our knowledge. This comprehensive analysis of resistance mechanisms to carbapenem and fluoroquinolones and their association with TTSS virulence genes, covering MDR P. aeruginosa in Brazil, is the largest reported to date.

Pseudomonas aeruginosa bacteraemia: independent risk factors for mortality and impact of resistance on outcome.

The rates of multidrug-resistant, extensively drug-resistant and pandrug-resistant isolates amongst non-fermenting Gram-negative bacilli, particularly Pseudomonas aeruginosa, have risen worldwide. The clinical consequence of resistance and the impact of adverse treatment on the outcome of patients with P. aeruginosa bacteraemia remain unclear. To better understand the predictors of mortality, the clinical consequence of resistance and the impact of inappropriate therapy on patient outcomes, we analysed the first episode of P. aeruginosa bacteraemia in patients from a Brazilian tertiary-care hospital during the period from May 2009 to August 2011. Antimicrobial susceptibility testing was conducted; phenotypic detection of metallo-ß-lactamase (MBL) and PCR of MBL genes were performed on carbapenem-resistant strains. Amongst the 120 P. aeruginosa isolates, 45.8 % were resistant to carbapenem and 36 strains were tested for MBL detection. A total of 30 % were phenotypically positive and, of these, 77.8 % expressed an MBL gene, bla(SPM-1) (57 %) and bla(VIM-type) (43 %). The resistance rates to ceftazidime, cefepime, piperacillin/tazobactam, carbapenem, fluoroquinolone and aminoglycoside were 55, 42.5, 35, 45.8, 44 and 44 %, respectively. Previous antibiotic use, length of a hospital stay ≥30 days prior to P. aeruginosa, haemodialysis, tracheostomy, pulmonary source of bacteraemia and Intensive Care Unit admission were common independent risk factors for antimicrobial resistance. Cefepime resistance, multidrug resistance and extensive drug resistance were independently associated with inappropriate therapy, which was an important predictor of mortality, being synergistic with the severity of the underlying disease.