Chlorhexidine susceptibility and Eagle effect in planktonic cells and biofilm of nosocomial isolates.

The aim of this study is to evaluate the chlorhexidine gluconate (CHG) susceptibility in both planktonic cells and biofilm of 32 Gram-negative (Gn) and 6 Gram-positive (Gp) isolates by minimal inhibitory concentration (2-256 µg/mL for Gn and 2-32 µg/mL for Gp), minimal bactericidal concentration (4-256 µg/mL for Gn and 2-32 µg/mL for Gp) in planktonic cells, and minimal biofilm elimination concentration (128 ≥ 16,384 µg/mL in Gn and 32 ≥ 16,384 µg/mL in Gp) in biofilm environment. Our study showed that Gn isolates have higher minimal concentrations than Gp and bacteria in biofilms are more tolerant than planktonic ones. No correlation between MBC or MBEC and biofilm formation was statistically confirmed. The Eagle effect, previously described for antimicrobials and antifungals, was evidenced in this work for CHG, an antiseptic. Besides that, the phenomenon was described in 23/38 isolates (60.5%), raising minimal concentration up to ≥ 16,384 µg/mL. Our study showed that clinical isolates have a high ability to form biofilm allowing them to tolerate CHG concentrations as high as the ones used in clinical practice. Therefore, attention should be given to the occurrence of this phenomenon to avoid false susceptibility results.

Neisseria gonorrhoeae arthritis in a patient with systemic lupus: resistance and virulence profiles.

In this study, we describe a case report of gonococcal arthritis in a Systemic Lupus Erythematosus patient. Although several mechanisms favor disseminated gonococcal infection (DGI) in patients immunosuppressed by SLE, this association is rarely reported in literature. We performed whole genome sequencing (WGS) of the etiologic agent involved and molecular analysis using a global collection of Neisseria gonorrhoeae strains. Ours is the only sample derived from synovial fluid identified in this collection, the others being from the usual anatomical sites. Antimicrobial susceptibility was determined by disk diffusion and Etest, and WGS was conducted to determine multilocus sequence typing profiles, group isolates based on core genome single nucleotide polymorphisms (SNP), and identify virulence genes and antimicrobial resistance determinants. The N. gonorrhoeae samples in the global collection were highly heterogeneous. The SNP tree had a total 19,532 SNPs in 320 samples. Our sample displayed resistance to ciprofloxacin (MIC = 2 µg/mL) and tetracycline (zone diameter = 0 mm) belonged to ST 1588 and was not closely related to any isolate in the global collection of N. gonorrhoeae strains. The isolate had genetic features related to beta-lactam, tetracycline and quinolone resistance. Seventy-one virulence genes were identified in our sample, belonging to the following classes: adherence, efflux pump, immune modulator, invasion, iron uptake, protease and stress adaptation. Moreover, no virulence genes for immune evasion and toxin were identified.

Selection and Identification of a DNA Aptamer for Multidrug-Resistant Acinetobacter baumannii Using an In-House Cell-SELEX Methodology.

Infections caused by multidrug-resistant A. baumannii are a worldwide health concern with high mortality rates. Rapid identification of this infectious agent is critical as it can easily spread with difficult or no options for treatment. In this context, the development of reliable and economically viable detection and therapeutic methodologies are still challenging. One of the promising solutions is the development of nucleic acid aptamers capable of interacting with bacteria. These aptamers can be used for specific recognition of infectious agents as well as for blocking their functions. Cell-SELEX technology currently allows the selection and identification of aptamers and is flexible enough to target molecules present in an entire bacterial cell without their prior knowledge. However, the aptamer technology is still facing many challenges, such as the complexity of the screening process. Here, we describe the selection and identification of a new aptamer A01, using an in-house whole-cell SELEX-based methodology, against multi-resistant Acinetobacter baumannii, with rapid execution and low cost. In addition, this protocol allowed the identification of the aptamer A01 with the whole A. baumannii cell as a target. The aptamer A01 demonstrated a binding preference to A. baumannii when compared to K. pneumoniae, C. albicans, and S. aureus in fluorescence assays. Although the time-kill assay did not show an effect on bacterial growth, the potential bactericidal or bacteriostatic cannot be totally discarded. The new categorized aptamer (A01) displayed a significant binding affinity to MDR A. baumannii.

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.

Carbapenem-resistant Klebsiella pneumoniae colonization and infection is associated with lower overall survival in a cohort of haematopoietic stem-cell transplantation patients: mechanism of resistance and virulence by whole-genome sequencing.

Carbapenem-resistant Klebsiella pneumoniae (CRK) infections are a growing concern in immunocompromised patients. The aim of the present study was to evaluate the impact of CRK colonization and infection in overall mortality for haematopoietic stem-cell transplant (HSCT) patients. We also aimed to investigate resistance and virulence profiles of CRK isolates and assess their epidemiological and genetic relatedness. Patients in the HSCT unit were screened for colonization with CRK with weekly rectal swab or stool cultures and placed under contact precautions. We defined CRK colonization as positive culture from a swab or stool sample grown in MacConkey agar with meropenem at 1 µg ml-1. Demographic and clinical data were retrieved from the patients' charts and electronic records. According to resistance mechanisms and pulsed field gel electrophoresis profile, isolates were selected based on whole-genome sequencing (WGS) using MiSeq Illumina. Outcomes were defined as overall mortality (death up to D+100), and infection-related death (within 14 days of infection). We report a retrospective cohort of 569 haematopoietic stem-cell transplant patients with 105 (18.4 %) CRK colonizations and 30 (5.3 %) infections. blaKPC was the most frequent carbapenemase in our cohort with three isolates co-harbouring blaKPC and blaNDM. We found no difference in virulence profiles from the CRK isolates. There were also no significant differences in virulence profiles among colonization and infection isolates regarding genes encoding for type 1 and 3 fimbriae, siderophores, lipopolysaccharide and colibactin. In clonality analysis by PFGE and WGS, isolates were polyclonal and ST340 was the most prevalent. Overall survival at D+100 was 75.4 % in in CRK-colonized (P=0.02) and 35.7 % in infected patients and significantly lower than non-colonized patients (85.8 %; P<0.001). We found a higher overall mortality associated with colonization and infection; KPC was the main resistance mechanism for carbapenems. The polyclonal distribution of isolates and findings of CRK infection in patients not previously colonized suggest the need to reinforce antibiotic stewardship.