Clinical outcome from hematopoietic cell transplant patients with bloodstream infection caused by carbapenem-resistant P. aeruginosa and the impact of antimicrobial combination in vitro.

Bloodstream infection (BSI) caused by carbapenem-resistant P. aeruginosa (CRPA) has high mortality in hematopoietic stem cell transplant (HSCT) recipients. We performed MIC, checkerboard, time-kill assay, PFGE, PCR, and whole genome sequence and described the clinical outcome through Epi Info comparing the antimicrobial combination in vitro. Mortality was higher in BSI caused by CRPA carrying the lasB virulence gene. The isolates were 97% resistant to meropenem displaying synergistic effect to 57% in combination with colistin. Seventy-three percent of the isolates harbored blaSPM-1 and Tn4371 and belonged to ST277. The synergistic effect in vitro with meropenem with colistin appeared to be a better therapeutic option.

Predictive factors, outcomes, and molecular epidemiology of Clostridioides difficile diarrhea in Brazilian hospitals.

Little is known about the role of lineage of strains of Clostridioides difficile (CD) on the clinical presentation of CD infection (CDI) in Latin America, especially regarding the treatment response. We conducted a multicenter, prospective study to investigate the predictive factors and treatment outcomes of CDI in hospitalized patients and to performed phenotypical and molecular characterization of CD strains. A total of 361 diarrheic patients at 5 hospitals from different regions of the country were enrolled. All stool samples were tested for glutamate dehydrogenase (GDH), toxins A and B, and toxin genes using a nucleic acid amplification test (NAAT). Specimens were cultured and susceptibility profile and whole-genome sequencing (WGS) were performed. CDI positivity was 15% (56/377). Predictive factors for CDI were prior use of meropenem (OR 4.09, 95% CI 2.097-7.095; p<0.001), mucus in stools (OR 3.29; 95% CI 1.406-7.722; p=0.006) and neutrophil left-shift with >20% of bands (OR 3.77; 95% IC 1.280-11.120; p=0.016). Overall mortality was 19%, with no deaths attributed to CDI. Oral metronidazole was used in 74% of cases, with 85% of cure and 14% of recurrence. A total of 35 CD isolates were recovered, all of them susceptible to metronidazole and vancomycin. The WGS revealed 17 different STs, six of which were novel. ST42 was the most common ST and hypervirulent strains were not found. Severe CDI were caused by ST42, ST5, ST8, ST48, ST33 and a novel ST667. The ermB gene was more frequently found in isolates of ST42 (p=0.004).

Prevalence of Clostridioides difficile associated diarrhea in hospitalized patients in five Brazilian centers: A multicenter, prospective study.

Epidemiological data on CD infection (CDI) in Latin American are scarce. CDI prevalence and strains characterization were prospectively evaluated in 5 Brazilian hospitals from different regions. Prevalence rates of CDI were 15%, ranging from 0 to 37%. ST42 was the most common Sequence Type and hypervirulent strains were not identified.

Simultaneous colonization by Escherichia coli and Klebsiella pneumoniae harboring mcr-1 in Brazil.

CASE PRESENTATION: We present a case report of a woman, concurrently colonized by polymyxin-resistant E. coli and K. pneumoniae. A Brazilian female patient, in her mid-fifties, was hospitalized with schistosomiasis. During hospitalization, polymyxin-resistant E. coli and K. pneumoniae were isolated from surveillance cultures. METHODS: Identification, antimicrobial susceptibility testings, PCR for mcr-1, plasmid transfer by conjugation and whole genome sequencing were performed. RESULTS: E. coli ST744 and K. pneumoniae ST101 carrying mcr-1 gene were described. Transconjugant E. coli was positive for mcr-1 and IncX4 by PCR. The plasmid is a 33,304-base pair plasmid, and the mcr-1 gene was the only antimicrobial resistance gene present in the plasmid. CONCLUSIONS: This study presents a case report of a hospitalized woman, concurrently colonized by mcr-1-harboring E. coli ST744, a different ST from previously described in Brazil, and a K. pneumoniae ST101.

Clonality, outer-membrane proteins profile and efflux pump in KPC- producing Enterobacter sp. in Brazil.

BACKGROUND: Carbapenems resistance in Enterobacter spp. has increased in the last decade, few studies, however, described the mechanisms of resistance in this bacterium. This study evaluated clonality and mechanisms of carbapenems resistance in clinical isolates of Enterobacter spp. identified in three hospitals in Brazil (Hospital A, B and C) over 7-year. METHODS: Antibiotics sensitivity, pulsed-field gel electrophoresis (PFGE), PCR for carbapenemase and efflux pump genes were performed for all carbapenems-resistant isolates. Outer-membrane protein (OMP) was evaluated based on PFGE profile. RESULTS: A total of 130 isolates of Enterobacter spp were analyzed, 44/105 (41, 9%) E. aerogenes and 8/25 (32,0%) E. cloacae were resistant to carbapenems. All isolates were susceptible to fosfomycin, polymyxin B and tigecycline. KPC was present in 88.6% of E. aerogenes and in all E. cloacae resistant to carbapenems. The carbapenems-resistant E. aerogenes identified in hospital A belonged to six clones, however, a predominant clone was identified in this hospital over the study period. There is a predominant clone in Hospital B and Hospital C as well. The mechanisms of resistance to carbapenems differ among subtypes. Most of the isolates co-harbored blaKPC, blaTEM and /or blaCTX associated with decreased or lost of 35-36KDa and or 39 KDa OMP. The efflux pump AcrAB-TolC gene was only identified in carbapenems-resistant E. cloacae. CONCLUSIONS: There was a predominant clone in each hospital suggesting that cross-transmission of carbapenems-resistant Enterobacter spp. was frequent. The isolates presented multiple mechanisms of resistance to carbapenems including OMP alteration.

In vitro activity of potential old and new drugs against multidrug-resistant gram-negatives.

BACKGROUND: The aim of this study was to evaluate the in vitro susceptibility of MDR gram-negatives bacteria to old drugs such as polymyxin B, minocycline and fosfomycin and new drugs such as tigecycline. METHODS: One hundred and fifty-three isolates from 4 Brazilian hospitals were evaluated. Forty-seven Acinetobacter baumannii resistant to carbapenens harboring adeB, blaOxA23, blaOxA51, blaOxA143 and blaIMP genes, 48 Stenotrophomonas maltophilia including isolates resistant to levofloxacin and/or trimethoprim-sulfamethoxazole harboring sul-1, sul-2 and qnrMR and 8 Serratia marcescens and 50 Klebsiella pneumoniae resistant to carbapenens harboring blaKPC-2 were tested to determine their minimum inhibitory concentrations (MICs) by microdilution to the following drugs: minocycline, ampicillin-sulbactam, tigecycline, and polymyxin B and by agar dilution to fosfomycin according with breakpoint criteria of CLSI and EUCAST (fosfomycin). In addition, EUCAST fosfomycin breakpoint for Pseudomonas spp. was applied for Acinetobacter spp and S. maltophilia, the FDA criteria for tigecycline was used for Acinetobacter spp and S. maltophilia and the Pseudomonas spp polymyxin B CLSI criterion was used for S. maltophilia. RESULTS: Tigecycline showed the best in vitro activity against the MDR gram-negative evaluated, followed by polymyxin B and fosfomycin. Polymyxin B resistance among K. pneumoniae was detected in 6 isolates, using the breakpoint of MIC > 8 ug/mL. Two of these isolates were resistant to tigecycline. Minocycline was tested only against S. maltophilia and A. baumannii and showed excellent activity against both. CONCLUSIONS: Fosfomycin seems to not be an option to treat infections due to the A. baumannii and S. maltophilia isolates according with EUCAST breakpoint, on the other hand, showed excellent activity against S. marcescens and K. pneumoniae.

Characterization of carbapenem-resistant Pseudomonas aeruginosa clinical isolates, carrying multiple genes coding for this antibiotic resistance.

BACKGROUND: Carbapenemase genes are one of the most frequent mechanisms reported in carbapenem-resistant P. aeruginosa; however, description of P. aeruginosa co-harbouring two or more carbapenemases is unusual. METHODS: In this study we evaluated the presence of carbapenemase genes and the clonality of P. aeruginosa isolates obtained from a hospital over a 12-year period. A total of 127 isolates of carbapenem-resistant P. aeruginosa recovered from 109 patients feces (four samples), rectal swab (three samples), nasal swab (one sample) and anal abscess (one sample), were evaluated. Minimum inhibitory concentrations of the following antibiotics imipenem, meropenem and polymyxin E were determined by broth microdilution. The molecular profile of isolates was evaluated by pulsed field gel electrophoresis (PFGE). PCR for the following carbapenemase genes blaIMP;blaSPM;blaVIM;blaSIM;blaNDM;blaKPC;blaGES and nucleotide sequencing to confirm the enzyme gene types were performed and compared with the database available on the Internet (BLAST-http://www.ncbi.nlm.nhi.gov/blast/). RESULTS: All isolates were carbapenem-resistant, their MIC50 and MIC90 were respectively 64 µg/mL and 256 µg/mL to imipenem and 32 µg/mL and 256 µg/mL to meropenem, all isolates except one (MIC = 8 mg/L) were susceptible to polymyxin E. The most frequent carbapenemase genes identified were blaSPM identified in 41 isolates (32%), followed by 10 with blakpc and 5 with blaVIM (3.9%). All belonged to the class SPM-1 and VIM-2. In 2011, one isolate harbouring three carbapenemase genes (SPM-1, VIM-2 and KPC-2) that belonged to a new clone was identified in a hematopoietic stem cell transplanted patient. Then, 19 carbapenem-resistant P. aeruginosa were identified in an outbreak that occurred in the bone marrow transplant unit, all positive for SPM-1 gene, and 9 (47.3%) harbored both SPM-1 and KPC. CONCLUSION: Our findings showed that PCR for KPC gene should be performed to evaluate carbapenem resistance in P. aeruginosa and that this agent can harbor more than one carbapenemase gene. Attention should be focused on the possible rapid spread of KPC in P. aeruginosa isolates and for the fact that P. aeruginosa may become a reservoir of this transmissible resistance mechanism.

Risk factors for bloodstream infection by multidrug-resistant organisms in critically ill patients in a reference trauma hospital.

BACKGROUND: Bloodstream infections (BSI) by multidrug-resistant (MDR) organisms are responsible for significant mortality in critically ill trauma patients. Our objective is to identify the risk factors for BSI by MDR agents and their resistance mechanisms in a trauma reference hospital. METHODS: During 18 months, all patients admitted in our Intensive Care Unit (ICU) were enrolled in this prospective cohort. We included the first episode of BSI by carbapenem-resistant Gram-negative bacteria, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococcus. Demographic and clinical data were compared among patients with and without BSI and variables with P < .05 were tested in a multivariate analysis. We performed PCR for identification of carbapenemase and SCC mec genes and Pulsed-field gel electrophoresis for clonality. RESULTS: Out of 1,528 patients, 302 (19.8%) were trauma and 66 (4.3%) had a MDR-BSI (19.5% were trauma). The multivariate analysis showed that mechanical ventilation (OR3.16; 95% CI 1-8; P = .02), hemodialysis (OR3.16; 95% CI 1-5; P = .0003) and surgery (OR1.76; 95% CI 1-3; P = .04) were independent risk factors for MDR-BSI. The most frequent MDR were Klebsiella pneumoniae (n = 26) and MRSA (n = 27). Regarding K pneumoniae strains (n = 24), 20 (83.8%) harbored bla KPC gene and 1 bla NDM. The majority of KPC isolates belonged to a predominant clone; while the MRSA were polyclonal and SCC mec type II. CONCLUSIONS: Mechanical ventilation, surgery and hemodialysis were independent risk factors for MDR-BSI in our cohort, but trauma was not. KPC was the main mechanism of resistance among carbapenem-resistant K pneumoniae that belonged to a predominant clone which could indicate cross-transmission.

MRSA outbreak in a Neonatal Intensive Care Unit in a developed country: importance of rapid detection of reservoirs and implementation of intervention measures.

We described a MRSA bloodstream infection outbreak that was rapidly identified and controlled in a Neonatal Intensive Care Unit after implementation of a bundle of measures, including PCR-screening and HCW decolonization. We found 35% of healthcare workers(HCW) colonized with S. aureus by PCR, one of them that presented skin lesion positive for MSSA (same clone and spa type than two patients). Our findings raise the hypothesis that the outbreak could be related to HCW colonization.

Virulomic Analysis of Multidrug-Resistant Klebsiella pneumoniae Isolates and Experimental Virulence Model Using Danio rerio (Zebrafish).

This study evaluates a possible correlation between multidrug-resistant Klebsiella pneumoniae strains and virulence markers in a Danio rerio (zebrafish) model. Whole-genome sequencing (WGS) was performed on 46 strains from three Brazilian hospitals. All of the isolates were colistin-resistant and harbored blaKPC-2. Ten different sequence types (STs) were found; 63% belonged to CC258, 22% to ST340, and 11% to ST16. The virulence factors most frequently found were type 3 fimbriae, siderophores, capsule regulators, and RND efflux-pumps. Six strains were selected for a time-kill experiment in zebrafish embryos: infection by ST16 was associated with a significantly higher mortality rate when compared to non-ST16 strains (52% vs. 29%, p = 0.002). Among the STs, the distribution of virulence factors did not differ significantly except for ST23, which harbored a greater variety of factors than other STs but was not related to a higher mortality rate in zebrafish. Although several virulence factors are described in K. pneumoniae, our study found ST16 to be the only significant predictor of a virulent phenotype in an animal model. Further research is needed to fully understand the correlation between virulence and sequence types.

Clostridioides difficile from Brazilian hospitals: characterization of virulence genes by whole genome sequencing.

Clostridioides difficile (CD) is the most frequent cause of healthcare related diarrhea and its severity has increased in the last decade by the spread of hypervirulent strains. Most important CD virulence factor is toxin production; however, not only toxins are responsible for Clostridioides virulence. We sequenced 38 strains and analyzed the presence and integrity of 24 virulence (including toxin) genes. We identified 28 toxigenic strains, six also presented the cdt genes. Only six strains didn't present all others genes searched. All absent genes were adhesion related. Understand others CD virulence factors can lead to a best understanding on this matter.

Identification of Staphylococcus aureus carrying the mecA gene in ready-to-eat food products sold in Brazil.

Since Staphylococcus aureus can cause several types of diseases, the development of antibiotic resistance poses an even greater threat to public health. S. aureus is known to possess the adaptive capability to promptly respond to antibiotics, making it resistant and increasingly difficult to treat; methicillin-resistant strains of S. aureus are a major concern with regard to this species. Previous studies reported the identification of methicillin-resistant S. aureus in food, demonstrating that this can represent a source of S. aureus which may carry the mecA gene. Fifty-seven S. aureus isolates, previously obtained from different types of food, were screened by polymerase chain reaction with specific primers for the mecA gene, which mediates methicillin resistance. Five (9%) isolates showed the presence of mecA gene, demonstrating that food may contain microorganisms possessing resistance genes. This study emphasizes the need to include food as a possible source of S. aureus carrying mecA gene and the need to monitor these products. Moreover, this is the first report of the presence of mecA genes in S. aureus isolated from ready-to-eat food in Brazil and Latin America.

Genetic factors involved in fosfomycin resistance of multidrug-resistant Acinetobacter baumannii.

The treatment of infections caused by A. baumannii is a challenge and fosfomycin has been used as a combination therapy. Moreover, data regarding the fosfomycin resistance mechanism is scarce. The goals of this study were to evaluate fosfomycin susceptibility in polyclonal multi-resistant A. baumannii isolates and characterize the fosfomycin resistance. We analyzed 32 A. baumannii isolates from a Brazilian bacterial collection, followed by their minimum inhibitory concentration (MIC), and whole-genome sequence to detect fosfomycin resistance genes. The isolates showed a fosfomycin MIC ranging from 32 to ≥256 mg/L. All isolates were negative for fosA and fosB genes, and four isolates carried the fosX gene. Two different metabolic pathways that form peptidoglycan precursors were identified. Mutations were observed in the adenylate cyclase gene. All A. baumannii isolates studied showed Val132Ala substitutions in MurA. The analysis showed different ways that may lead to the intrinsic fosfomycin-resistance of A. baumannii, such as alterations on the glycerol-3-phosphate transporter system caused by adenylate cyclase mutations; and a possible connection of cell wall recycling by different metabolic pathways.

Rhodococcus hoagii bloodstream infection in an allogeneic hematopoietic stem cell transplantation patient: Case report and review of literature.

We report a case of bloodstream infection caused by R. hoagii in a woman with acute myeloid leukemia, 37-years-old, who received an allogeneic hematopoietic stem cell transplant. She developed cutaneous and gastrointestinal tract graft versus host disease, respectively on day 29 and day 69. On day 157 she developed to acute severe respiratory failure. Rhodococcus sp was identified by MALDI-TOF and 16S rRNA sequencing from blood culture as Rhodococcus hoagii. The patient was a nurse that lived in urban areas, and stated no recent trips to countryside areas neither contacted with animals. Despite of the treatment with antibiotics with action against R. hoagii such as linezolid and meropenem the patient evolved to multiorgan dysfunction and death. Our case-report emphasizes the importance of early diagnosis and the use of 16S rRNA sequencing to confirmed the identification of species of Rhodococcus infection.

Multidrug-resistant Klebsiella pneumoniae: genetic diversity, mechanisms of resistance to polymyxins and clinical outcomes in a tertiary teaching hospital in Brazil.

Increased resistance to polymyxin in Klebsiella pneumoniae (ColRKP) has been observed. Molecular epidemiology, as well as the clinical impact of these difficult to treat pathogens need to be better characterized. We present the clinical outcomes of 28 patients infected by ColRKP in a tertiary hospital. Isolates with MIC >2 by Vitek 2 were confirmed by the microdilution broth test. Polymerase chain reaction (PCR) was performed for blaKPC, blaNDM, blaOXA-48 and blamcr-1 genes in the isolates, and Whole Genome Sequencing (WGS) was performed in six isolates. Seventeen (61%) patients were female and the mean age was 50 years old. In-hospital and 30-day mortality were 64% (18/28) and 53% (15/28), respectively. Central line-associated bloodstream infection in addition to bacteremia episodes due to other sources were the most frequent (61%). Mean APACHE and Charlson comorbidity index were 16 and 5, respectively. Twenty patients (71%) received at least one active drug and ten (35%) received two drugs: tigecycline 46% (13/28); amikacin 21% (6/28) and fosfomycin 3% (1 case). Twenty-six out of 28 tested cases were positive for blaKPC. Eight different clusters were identified. Four STs were detected (ST11, ST23, ST340, and ST437). Mutations on pmrA, arnB, udg, and yciM genes were present in all six isolates submitted to WGS; lpxMand mgrB mutations were also detected in all but one isolate. In conclusion, we observed resistance to polymyxin in severely ill patients mostly from intensive care units and/or immunosuppressed patients with high mortality rates in whom a diversity of ColRKP clusters was identified and might indicate selective pressure.

Genetic and virulence characterization of colistin-resistant and colistin-sensitive A. baumannii clinical isolates.

Treatment of infections caused by A. baumannii is becoming a challenge due to the ability to develop multidrug-resistance, virulence, and high mortality. We described the colistin resistance and virulence genes present in sixA. baumannii clinical isolates using WGS, expression by qPCR, and virulence in the Galleria mellonella model. The colistin-resistant isolates were assigned as ST233 and the colistin-susceptible isolates as ST236 and ST407. The colistin-resistant isolates contained mutations within PmrA/PmrB, and the pmrA showed up-regulation in all of them. Only one colistin-resistant isolate indicating virulence in G. mellonella. This particular isolate belonged to a different clone, and it was the only isolate that presented non-synonymous mutations in pmrB. Colistinresistance in A. baumannii isolates seems to be caused by up-regulation of pmrA gene. Only one isolate appeared to be virulent in the G. mellonella model. This finding indicating low virulence in isolates belonging to emerging clones circulating in our hospital.

Evaluation of adenosine triphosphate test for cleaning assessment of gastroscopes and the effect on workload in a busy endoscopy center.

OBJECTIVE: Using adenosine triphosphate (ATP) tests to assess manual cleaning of gastroscopes and to determine the associated workload in a busy endoscopy unit. METHODS: Patient-used gastroscopes were sampled before and after cleaning to assess ATP levels, bioburden, and protein. Samples were collected by flushing 20 mL of sterile water through the biopsy port to the distal end. Time spent for reprocessing and performing the ATP test was recorded. RESULTS: Twenty-four samples were collected from 10 gastroscopes. After manual cleaning, 14/24 (58.3%) samples had no microbial growth (mean, 21 colony-forming units/cm2), and in 22/24 (91.7%) samples the protein was undetectable (mean, 0.04 µg/cm2). ATP test was above the cutoff (200 relative light units [RLU]) in 17/24 (70.8%) samples (mean, 498 RLU). After the second cleaning, 11/17 (64.7%) gastroscopes still failed the ATP test (mean, 321.2 RLU). The mean time spent to perform manual cleaning and ATP tests was 16 and 8 minutes, respectively. Hence, each test increased the length of time for cleaning plus testing cleanliness by 50%. CONCLUSION: Further studies regarding the optimal cutoff for ATP tests are needed. ATP tests for cleaning monitoring are easy to perform and provide immediate feedback to the team. However, the increased workload needs to be considered.

Multidrug-resistant Stenotrophomonas maltophilia: Description of new MLST profiles and resistance and virulence genes using whole-genome sequencing.

OBJECTIVES: Stenotrophomonas maltophilia is an opportunistic pathogen that has high intrinsic and acquired antimicrobial resistance, with great genetic diversity. The aim of this study was to characterise four S. maltophilia clinical isolates displaying different susceptibility profiles using whole-genome sequencing. METHODS: The whole genomes of four clinical isolates of S. maltophilia from three patients were sequenced using Ion Torrent™ PGM technology. The isolates presented different susceptibilities to trimethoprim/sulfamethoxazole (SXT) and levofloxacin. RESULTS: Three new multilocus sequence typing (MLST) profiles were identified (ST144, ST172 and ST173), differing in virulence and resistance genes. The ST172 isolate had more genes related to toxins than related to motility or adhesion and had different types of efflux pumps than the other isolates. The SXT-resistant strains belonged to ST172 or ST144 and did not harbour the sul1, sul2 or dfrA resistance genes. Strains I and II, from the same patient and belonging to the same ST but differing in resistance to SXT, had all of the resistance genes searched for in common, except for the SmeABC efflux pump complex genes that were only found in the SXT-resistant strain. All strains, including the strain susceptible to levofloxacin, harboured the qnrB gene, which may question the importance of this gene in determining levofloxacin resistance in S. maltophilia. CONCLUSION: Here we describe three new MLST profiles. Resistance to SXT in these strains appears to be associated with efflux pumps.

Molecular characterization of carbapenem-resistant Klebsiella pneumoniae isolates from a university hospital in Brazil.

INTRODUCTION: The emergence of Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kpn) isolates is attracting significant attention in nosocomial infection settings. K. pneumoniae is the main pathogen that harbours blaKPC genes. METHODOLOGY: This study evaluated 54 K. pneumoniae carbapenem-resistant isolates from patients hospitalized at the University Hospital of Londrina, between July 2009 and July 2010. The isolates were phenotypically screened for carbapenemase production and submitted for genotypic confirmation by polymerase chain reaction (PCR) for KPC, metallo-ß-lactamases, OXA-48, and extended-spectrum beta-lactamase genes. The absence of outer membrane proteins (OMP) was investigated by SDS-PAGE. The susceptibility profile was determined by broth microdilution, according to Clinical and Laboratory Standards Institute protocol. RESULTS: All isolates were phenotypically positive for class A carbapenemase production, but negative for metallo-ß-lactamase activity. PCR analysis demonstrated that all isolates carried blaKPC genes and sequencing showed that all strains belonged to KPC-2 subtype. Four strains did not show porin expression, and all isolates were resistant to ertapenem, meropenem, and imipenem. Susceptibility rates reached 35.2% for gentamicin, 85.2% for polymixyn B, 87% for colistin, and 98.1% for both tigecycline and fosfomycin. Pulsed-field gel electrophoresis showed six clones, and three of them predominated among the isolates. CONCLUSIONS: KPC-2-producing K. pneumoniae is becoming predominant among carbapenem-resistant K. pneumoniae isolates at the hospital. The association of the enzyme KPC with other resistance determinants, such as loss of porins, may increase the severity of the situation of nosocomial infections. There is an urgent need to develop strategies for infection control and prevention.

High mortality of bloodstream infection outbreak caused by carbapenem-resistant P. aeruginosa producing SPM-1 in a bone marrow transplant unit.

PURPOSE: Carbapenem resistance in P. aeruginosa is increasing worldwide. In Brazil, SPM-1 is the main P. aeruginosa carbapenemase identified. Little is known about the virulence factor in SPM-1 clones.Methodolgy. We describe a carbapenem-resistant P. aeruginosa bloodstream infection (CRPa-BSI) outbreak in a bone marrow transplant Unit (BMT). Twenty-nine CRPa-BSI cases were compared to 58 controls. Microbiological characteristics of isolates, such as sensitivity, carbapenemase gene PCR for P. aeruginosa, and PFGE are described, as well as the whole-genome sequence (WGS) of three strains.Results/Key findings. The cultures from environmental and healthcare workers were negative. Some isolates harboured KPC and SPM. The WGS showed that the 03 strains belonged to ST277, presented the same mutations in outer membrane protein, efflux pump, and virulence genes such as those involved in adhesion, biofilm, quorum-sensing and the type III secretion system, but differ regarding the carbapenemase profile. A predominant clone-producing SPM harbouring Tn 4371 was identified and showed cross-transmission; no common source was found. Overall mortality rate among cases was 79 %. The first multivariate analysis model showed that neutropenia (P=0.018), GVHD prophylaxis (P=0.016) and prior use of carbapenems (P=0.0089) were associated with CRPa-BSI. However, when MASCC>21 points and platelets were added in the final multivariate analysis, only prior use of carbapenems remained as an independent risk factor for CRPa-BSI (P=0.043). CONCLUSIONS: The predominant clone belonging to ST277 showed high mortality. Carbapenem use was the only risk factor associated with CRPa-BSI. This finding is a wake-up call for the need to improve management in BMT units.