First characterisation of plasmid-mediated quinolone resistance-qnrS1 co-expressed bla CTX-M-15 and bla DHA-1 genes in clinical strain of Morganella morganii recovered from a Tunisian Intensive Care Unit.

PURPOSE: Aim of this study was to show the emergence of the qnr genes among fluoroquinolone-resistant, AMPC and ESBL (extended-spectrum-beta-lactamase) co-producing Morganella morganii isolate. MATERIALS AND METHODS: A multi resistant Morganella morganii SM12012 isolate was recovered from pus from a patient hospitalized in the intensive care unit at the Military hospital, Tunisia. Antibiotic susceptibility was tested with the agar disk diffusion method according to Clinical and Laboratory Standards Institute guidelines. ESBLs were detected using a standard double-disk synergy test. The characterization of beta-lactamases and associated resistance genes were performed by isoelectric focusing, polymerase chain reaction and nucleotide sequencing. RESULTS: The antimicrobial susceptibility testing showed the high resistance to penicillins, cephalosporins (MICs: 64-512 µg/ml) and fluoroquinolones (MICs: 32-512 µg/ml). But M. morganii SM12012 isolate remained susceptible to carbapenems (MICs: 4-<0.25 µg/ml). The double-disk synergy test confirmed the phenotype of extended-spectrum ß-lactamases (ESBLs). Three identical ß-lactamases with pI values of 6.5, 7.8 and superior to 8.6 were detected after isoelectric focusing analysis. These ß-lactamases genes can be successfully transferred by the conjugative plasmid. Molecular analysis demonstrated the co-production of bla (DHA-1), bla (CTX-M-15) and qnrS1 genes on the same plasmid. The detection of an associated chromosomal quinolone resistance revealed the presence of a parC mutation at codon 80 (Ser80-lle80). CONCLUSION: This is the first report in Tunisia of nosocomial infection due to the production of CTX-M-15 and DHA-1 ß-lactamases in M. morganii isolate with the association of quinolone plasmid resistance. The incidence of these strains invites continuous monitoring of such multidrug-resistant strains and the further study of their epidemiologic evolution.

Properties of a previously undescribed grapevine nepovirus from Tunisia.

A virus with isometric particles c. 30 nm in diameter and angular contour was isolated by inoculation of sap from a Tunisian grapevine with mild mottling and leaf deformation. The virus sedimented in sucrose density gradients as three components: T (empty shells), M (particles containing a molecule of ssRNA with an apparent size of 5,800 nucleotides, constituting 35% of the particle weight) and B (particles containing a molecule of ssRNA with apparent size of 6,800 nucleotides, constituting 41% of the particle weight). Virus particles had buoyant densities of 1.31 (T), 1.45 (M), and 1.49 g/cm3 (B) in cesium chloride equilibrium gradients. The coat protein subunits consisted of a single polypeptide with mol. wt. of c. 59,000 daltons. An antiserum was produced with a titer of 1:256, which did not react with healthy plant antigens. Cells of artificially infected herbaceous hosts showed cytoplasmic vesiculate-vacuolate inclusion bodies, virus-containing tubules, mostly associated with plasmodesmata and/or cell wall protrusions, and crystalline aggregates of virus particles and empty capsids. The physicochemical and ultrastructural properties of this virus resemble very much those of nepoviruses. However, it was serologically unrelated to 19 different members of the group, including all those reported to infect grapevines. Therefore, the virus is possibly a hitherto unreported nepovirus for which the name of grapevine Tunisian ringspot virus (GTRV) is proposed.