First report of blaOXA-24 carbapenemase gene, armA methyltransferase and aac(6')-Ib-cr among multidrug-resistant clinical isolates of Proteus mirabilis in Algeria

OBJECTIVE

Carbapenemase-producing, or carbapenem-resistant, Enterobacteriaceae are an emerging threat to human and animal health because they are resistant to many of the last-line antimicrobials available for treatment of infection. The aim of this study was to analyse the antimicrobial resistance patterns and their encoding genes of Proteus mirabilis isolated in Constantine, Algeria.

METHODS

A total of 108 Proteus, Morganella and Providencia (PMP) strains were isolated from a large variety of clinical specimens at University Hospital of Constantine in Algeria. Isolates were identified using the API 20E system and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Diagnostic accuracy was determined by independent comparison of each method to phylogenetic analysis based on 16S rRNA gene sequencing. Antimicrobial susceptibility was determined by the standard disk diffusion and Etest methods. The presence of antimicrobial resistance genes was screened for by PCR amplification and sequencing.

RESULTS

A total of 72 PMP strains were multidrug-resistant (MDR). Among them, one P. mirabilis isolate was resistant to imipenem with a minimum inhibitory concentration (MIC) of ≥12μg/mL. PCR and sequencing showed the presence of various antimicrobial resistance genes, including bla_CTX-M-15, bla_TEM-1, bla_TEM-2, bla_PER-1, bla_SHV-11, aadA1, aadA2, armA, aac(6')-Ib, aac(6')-Ib-cr, aac(3)-Ia and ant(2″)-I, forming different resistance profiles. Moreover, the bla_OXA-24 gene was detected in the imipenem-resistant P. mirabilis strain.

CONCLUSION

In this study, a MDR P. mirabilis isolate harbouring the bla_OXA-24, armA 16S rRNA methylase and aac(6)-Ib-cr genes was found for the first time in Algeria.

Inactivation of the arn operon and loss of aminoarabinose on lipopolysaccharide as the cause of susceptibility to colistin in an atypical clinical isolate of proteus vulgaris

Colistin has become a last-line antibiotic for the treatment of multidrug-resistant bacterial infections; however, resistance to colistin has emerged in recent years. Some bacteria, such as Proteus and Serratia spp., are intrinsically resistant to colistin although the exact mechanism of resistance is unknown. Here we identified the molecular support for intrinsic colistin resistance in Proteus spp. by comparative genomic, transcriptomic and proteomic analyses of colistin-susceptible (CSUR P1868_S) and colistin-resistant (CSUR P1867_R) strains of an atypical Proteus vulgaris. A significant difference in outer membrane glycoside structures in both strains that was corroborated by MALDI-TOF/MS analysis was found, which showed an absence of 4-amino-4-deoxy-l-arabinose (L-Ara4N) in the outer membrane lipid A moiety of the susceptible strain. Comparative genomic analysis with other resistant strains of P. vulgaris available in a local database found a mutation in the arnBCADTEF operon of the susceptible strain. Transcriptomic analysis of genes belonging to the arnBCADTEF operon showed a significant decrease in mRNA expression level of these genes in the susceptible strain, supporting addition of L-Ara4N in the outer membrane lipid A moiety as an explanation for colistin resistance. Insertion of the arnD gene that was suggested to be altered in the susceptible strain by in silico analysis led to a 16-fold increase of colistin MIC in the susceptible strain, confirming its role in colistin resistance in this species. Here we show that constitutive activation of the arn operon and addition of L-Ara4N is the main molecular mechanism of colistin resistance in P. vulgaris.

Antidiabetic, antioxidant and anti inflammatory properties of water and n-butanol soluble extracts from Saharian Anvillea radiata in high-fat-diet fed mice

ETHNOPHARMACOLOGICAL RELEVANCE

According to Saharian traditional medicine, Anvillea radiata Coss. & Dur. (Asteraceae) has been valued for treating a variety of ailments such as gastro-intestinal, liver and pulmonary diseases, and has gained awareness for its beneficial effect on postprandial hyperglycemia. However, to best of our knowledge, no detailed study of the antidiabetic curative effects of this plant has been conducted yet.

AIM OF THE STUDY

To determine the hypoglycemic and antidiabetic effect of dietary supplementation with Anvillea radiata extracts on high-fat-diet (HFD)-induced obesity and insulin resistance in C57BL/6J mice in relation with antioxidant, anti-inflammatory, pancreatic beta-cells and skeletal muscle protection, and digestive enzyme inhibiting properties.

MATERIALS AND METHODS

Six extracts (water soluble and organic) from aerial parts of the plant were analyzed phytochemically (total phenolic and flavonoid content) and screened for in vitro superoxide (by chemiluminescence) and hydroxyl radical (by electron paramagnetic resonance spin-trapping) scavenging, antioxidant (DPPH, TRAP and ORAC assays), xanthine oxidase, metal chelating, α-amylase and α-glucosidase inhibitory property, and protective effects on copper-induced lipoprotein oxidation. Then selected hydroalcoholic and aqueous extracts were assessed for toxicity in normal human lung fibroblasts and A549 cancer cells using FMCA and MTT assays. Two water-soluble extracts having the best overall properties were assessed for their (i) protective effect at 1-15µg/mL on metabolic activity of rat insulinoma-derived INS-1 cells exposed to hyperglycemic medium, and (ii) acute hypoglycemic effect on 16-weeks HFD-induced diabetic mice. Then diabetic mice were administered HFD supplemented by extracts (up to 150mg/kg/day) for 12 additional weeks using standard diet as control and the antidiabetic drug, metformin (150mg/kg), as positive control. Then the antidiabetic, anti-inflammatory and antioxidant activity of extracts were determined.

RESULTS

Of the highly efficient polyphenolics-enriched hydroalcoholic and ethyl acetate extracts, the lyophilized aqueous (AQL) and butanol extracts were not toxic in cells (≤ 400µg/mL) or when given orally in normal mice (≤ 2000mg/kg), exerted a dose-dependent hypoglycemic action in diabetic mice, which was maximal at the dose of 150mg/kg. Upon administering this dose for 12 weeks, both extracts significantly ameliorated body weight control capacity, recovery of plasma glucose and insulin level, reduced oxidative stress in blood, myocardial and skeletal muscles, and improved hyperlipidemic and inflammatory status. Moreover, diabetes-related complications were optimally ameliorated by oral therapy based on halved doses (75mg/kg) of a mixture of AQL and metformin.

CONCLUSIONS

Current investigation supports the traditional medicinal usage of Anvillea radiata and suggests that both readily accessible and low-cost bio-extracts have the potency to develop an antihyperglycemic, antihyperlipidemic and protective agent against beta-cells and muscle dysfunction at doses compatible with the common practices of indigenous people for the management of metabolic disorders.