An outbreak caused by multidrug-resistant OXA-58-positive Acinetobacter baumannii in an intensive care unit in Italy

Genomic study of Acinetobacter baumannii strains co-harboring bla OXA-58 and bla NDM-1 reveals a large multidrug-resistant plasmid encoding these carbapenemases in Brazil

Introduction

Acinetobacter baumannii contributes significantly to the global issue of multidrug-resistant (MDR) nosocomial infections. Often, these strains demonstrate resistance to carbapenems (MDR-CRAB), the first-line treatment for infections instigated by MDR A. baumannii. Our study focused on the antimicrobial susceptibility and genomic sequences related to plasmids from 12 clinical isolates of A. baumannii that carry both the blaOXA-58 and bla NDM-1 carbapenemase genes.

Methods

Whole-genome sequencing with long-read technology was employed for the characterization of an A. baumannii plasmid that harbors the bla OXA-58 and blaNDM-1 genes. The location of the bla OXA-58 and bla NDM-1 genes was confirmed through Southern blot hybridization assays. Antimicrobial susceptibility tests were conducted, and molecular characterization was performed using PCR and PFGE.

Results

Multilocus Sequence Typing analysis revealed considerable genetic diversity among bla OXA-58 and bla NDM-1 positive strains in Brazil. It was confirmed that these genes were located on a plasmid larger than 300 kb in isolates from the same hospital, which also carry other antimicrobial resistance genes. Different genetic contexts were observed for the co-occurrence of these carbapenemase-encoding genes in Brazilian strains.

Discussion

The propagation of bla OXA-58 and bla NDM-1 genes on the same plasmid, which also carries other resistance determinants, could potentially lead to the emergence of bacterial strains resistant to multiple classes of antimicrobials. Therefore, the characterization of these strains is of paramount importance for monitoring resistance evolution, curbing their rapid global dissemination, averting outbreaks, and optimizing therapy.

Influx of multidrug-resistant organisms by country-to-country transfer of patients

BACKGROUND

Multidrug-resistant organisms (MDRO) are a worldwide problem. International migration and travel facilitate the spread of MDRO. Therefore the goal of our study was to assess the risk of influx of MDRO from patients transferred to one of Central Europe's largest hospitals from abroad.

METHODS

A mono-centre study was conducted. All patients transferred from other countries were screened; additional data was collected on comorbidities, etc. Presence of carbapenemases of multidrug-resistant Gram-negatives was confirmed by PCR. The association between length of stay, being colonized and/or infected by a MDRO, country of origin, diagnosis and other factors was assessed by binomial regression analyses.

RESULTS

From 2012 to 2013, one fifth of all patients were colonized with MDRO (Methicillin-resistant Staphylococcus aureus [4.1 %], Vancomycin-resistant Enterococci [2.9 %], multidrug-resistant Gram-negatives [12.8 %] and extensively drug-resistant Gram-negatives [3.4 %]). The Gram-negatives carried a variety of carbapenemases including OXA, VIM, KPC and NDM. The length of stay was significantly prolonged by 77.2 % in patients colonized with a MDRO, compared to those not colonized (p<0.0001).

CONCLUSIONS

Country-to-Country transfer of patients to European hospitals represents a high risk of introduction of MDRO and infection control specialists should endorse containment and screening measures.

"Roar" of blaNDM-1 and "silence" of blaOXA-58 co-exist in Acinetobacter pittii

Acinetobacter pittii 44551 was recovered from a patient with gout combined with tuberculosis and was found to harbor the carbapenemase genes bla_NDM-1 and bla_OXA-58 on two different plasmids pNDM-44551 and pOXA58-44551, respectively. pNDM-44551 displayed high self-transferability across multiple bacterial species, while pOXA58-44551 was likely co-transferable with pNDM-44551 into A. baumannii receipts. pNDM-44551 was a close variant of the previously characterized pNDM-BJ01, and the bla_NDM-1 gene cluster was arranged sequentially as orfA, ISAba14, aphA6, ISAba125, bla_NDM-1, ble_MBL, ΔtrpF, dsbC, tnpR, and zeta. pOXA58-44551 was a repAci9-containing plasmid, and bla_OXA-58 was embedded in a 372F-ISAba3-like-bla_OXA-58-ISAba3 structure. The mobile genetic platforms of bla_NDM-1 and bla_OXA-58 herein showed some differences from their previously characterized variants. The production of NDM-1 in strain 44551 contributed the majority to its high resistance to carbapenems, while the bla_OXA-58 stayed silent most likely due to the lack of an upstream promoter to drive its transcription. Increased surveillance of Acinetobacter co-harboring bla_NDM-1 (active) and bla_OXA-58 (either active or silent) is urgently needed.

Country-to-country transfer of patients and the risk of multi-resistant bacterial infection

Management of patients with a history of healthcare contact in multiple countries is now a reality for many clinicians. Leisure tourism, the burgeoning industry of medical tourism, military conflict, natural disasters, and changing patterns of human migration may all contribute to this emerging epidemiological trend. Such individuals may be both vectors and victims of healthcare-associated infection with multiresistant bacteria. Current literature describes intercountry transfer of multiresistant Acinetobacter spp and Klebsiella pneumoniae (including Klebsiella pneumoniae carbapenemase- and New Delhi metallo-β-lactamase-producing strains), methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and hypervirulent Clostridium difficile. Introduction of such organisms to new locations has led to their dissemination within hospitals. Healthcare institutions should have sound infection prevention strategies to mitigate the risk of dissemination of multiresistant organisms from patients who have been admitted to hospitals in other countries. Clinicians may also need to individualize empiric prescribing patterns to reflect the risk of multiresistant organisms in these patients.

Amide isosteres of oroidin: assessment of antibiofilm activity and C. elegans toxicity

The synthesis and antibiofilm activities of sulfonamide, urea, and thiourea oroidin analogues are described. The most active derivative was able to selectively inhibit P. aeruginosa biofilm development and is also shown to be nontoxic upward of 1 mM to the development of C. elegans in comparison to other similar isosteric analogues and the natural product oroidin.