Co-occurrence of blaNDM-1 and blaOXA-23 in carbapenemase-producing Acinetobacter baumannii belonging to high-risk lineages isolated from burn patients in Tunisia.

AIMS: Carbapenem-resistant Acinetobacter baumannii (CR-Ab) is an important cause of infections in burn patients. This study aimed to characterize the antimicrobial susceptibility pattern of CR-Ab isolated from burns in Burn Intensive Care Unit (BICU) of the Trauma and Burn Centre of Ben Arous, to determine the prevalence of ß-lactamase-encoding genes and to search eventual genetic relatedness of CR-Ab strains. METHODS AND RESULTS: From 15 December 2016 to 2 April 2017, all nonduplicated CR-Ab isolated in burn patients in the BICU were screened by simplex Polymerase Chain Reaction (PCR) for the class A, B, C, and D ß-lactamase genes. Sequencing was performed for NDM gene only. Genetic relatedness was determined by using pulsed field gel electrophoresis (PFGE) and by multilocus sequence typing. During the study period, 34 strains of CR-Ab were isolated in burns, mainly in blood culture (n = 14) and central vascular catheter (n = 10). CR-Ab strains were susceptible to colistin but resistant to amikacin (91%), ciprofloxacin (100%), rifampicin (97%), and trimethoprim-sulfamethoxazole (100%). All strains harbored blaOXA-51-like and blaOXA-23 genes, only or associated to blaGES (n = 26; 76%), blaADC (n = 20; 59%), blaPER-1 (n = 6; 18%) or/and blaNDM-1 (n = 3; 9%). PFGE identified 16 different clusters and revealed that most strains belonged to one major cluster A (n = 15; 44.1%). Among NDM-1 isolates, two were clonally related in PFGE and belonged to two single locus variant sequence type ST-6 and ST-85. CONCLUSIONS: This is the first description of clonally related NDM-1 and OXA-23-producing A. baumannii strains in the largest Tunisian BICU associated with two single locus variant sequence types ST6 and ST85.

High rates of antibiotic resistance and biofilm production in Escherichia coli isolates from food products of animal and vegetable origins in Tunisia: a real threat to human health.

The aim of this study was to compare the antibiotic susceptibility of eighty Escherichia coli isolates from vegetables and food products of animal origin in Tunisia, and to study their genes encoding antibiotic resistance and in vitro biofilm forming capacity. Antimicrobial susceptibilities were determined, as well as PCR investigation of genes associated with antibiotic resistance. Biofilm formation was tested using four different methods: the microtiter plate-, MTT-staining-, XTT-staining-, and the Congo Red Agar assays. High antibiotic resistance rates were observed for amoxicillin (68.7%), amoxicillin/clavulanic acid (73.7%), gentamicin (68.7%), kanamycin (66.2%), nalidixic acid (36.2%), streptomycin (68.7%) and tetracycline (35%). The majority of isolates was multidrug resistant and biofilm producer. MTT testing showed that vegetables isolates were significantly higher biofilm producers compared to foods of animal origins. This study showed that E. coli isolates from food products were reservoirs of genes encoding antibiotic-resistance and have a high propensity to produce biofilm.

Characterization of Pseudomonas aeruginosa isolated from various environmental niches: New STs and occurrence of antibiotic susceptible "high-risk clones".

The aim of this study was to investigate the antimicrobial phenotypes, major virulence factors, and the molecular typing of 66 P. aeruginosa isolates collected from various sources: human patients and hospital environment, raw milk, poultry meat, chicken/sheep fecal samples, wastewater, thermal water, and seawater. All isolates, except one, were susceptible to all tested antibiotics. exoA, lasB, rhlR, and lasR genes were harbored by 60 isolates. Forty-six, 18, and 2 isolates amplified exoS, exoU, and exoS+exoU genes, respectively. Twenty-one isolates showed high elastase and pigment production. The PFGE typing identified 26 pulsotypes. Some pulsotypes included isolates from different environmental niches and areas. Twelve selected isolates were typed by MLST and eight different STs were found, three of them were new. Our results highlighted the dissemination of some clones amongst different settings and the occurrence of antibiotic susceptible 'high-risk clones' that might be very harmful when acquiring genes encoding antibiotic resistance.

Low antibiotic resistance rates and high genetic heterogeneity of Escherichia coli isolates from urinary tract infections of diabetic patients in Tunisia.

Antimicrobial resistance phenotypes, tetracycline, sulphonamide resistance genes, and integrons were analysed in 48 Escherichia coli isolates recovered from urine cultures of diabetic patients in Tunisia. Twenty-one were susceptible to all antibiotics tested. High rates of resistance were observed for amoxicillin (39.5%), trimethoprim-sulphamethoxazole (33.3%), sulphonamide (33.3%), and tetracycline (31.2%). Resistance to imipenem was not detected, and ESBL producing isolates were not recovered. Our analysis assigned 26, 13, 3, and 5 isolates to phylogroups A, B1, B2, and D, respectively. It is worthy to note that all the resistant isolates belonged to phylogroups A (15 isolates) and B1 (12 isolates), while for the 21 susceptible isolates, phylogroups A, B1, B2, and D were found in 11, 2, 3, and 5 isolates, respectively. Among 15 tetracycline-resistant isolates, the tetA and tetB genes were detected in three and four isolates, respectively. Among 17 sulphonamide resistant isolates, 12, 3, and 1 isolates harboured sul1, sul2, and sul3, respectively. sul1 and sul2 genes occurred simultaneously in three isolates. Integrons were detected in 11 isolates. Ten isolates harboured the class 1 integron and three the class 2 integron. The variable regions (VRs) of the class 1 integrons were analysed in the 10 in1-positive isolates, and the following gene cassette arrangements were detected: dfrA12-orfF-aadA2-cmIA1-aadA1-qacH-IS440-sul3 (one isolate), dfrA15-aadA1 (three isolates), dfrA5 (one isolate), dfrA17- aadA5 (one isolate), dfrA1-aadA1 (one isolate), and dfrA14 (one isolate). The VR of class 2 integron was analysed in the in2-positive isolates, and only one gene cassette arrangement was detected, dfrA1-sat-aadA1. Pulsed-field gel electrophoresis (PFGE) analysis of resistant isolates showed that all were unrelated. Our results highlight the moderate antibiotic resistance in the clinical isolates as well as their heterogeneous genetic background.

Chemical content, antibacterial and antioxidant properties of essential oil extract from Tunisian Origanum majorana L. cultivated under saline condition.

Essential oils of marjoram were extracted from plants, growing under non-saline and saline condition (75mM NaCl). Their antioxidant and antibaterial activity against six bacteria (Enterococcus faecalis, Escherichia coli, Salmonella enteritidis, Listeria ivanovii, Listeria inocula, and Listeria monocytogenes) were assessed. Result showed that, (i) independently of salt treatment, marjoram essential oils inhibited the growth of most of the bacteria but in degrees. The least susceptible one was Enterococcus faecalis. (ii) Gram negative bacteria seemed more sensitive to treated essential oils than Gram positive ones. (iii) Compared to synthetic antibiotics, marjoram essential oils were more effective against E. coli, L. innocua and S. enteridis. This activity was due to their high antioxidant activity. Thus, essential oils of marjoram may be an alternative source of natural antibacterial and antioxidant agents.

DNA fingerprinting of a multi-resistant coagulase-negative staphylococci isolated from biomaterials in dialysis services.

BACKGROUND: Coagulase-negative staphylococci (CoNS) have emerged as an important opportunistic pathogen isolated in hospital. Several species of CoNS have been implicated in human infections and disease especially in patients with poor health status. METHODS: A total of 71 clinical strains of CoNS were isolated from dialysis fluid and needles in a dialysis unit and characterized. Susceptibility to antibiotics, biofilm production and molecular typing by pulsed-field gel electrophoresis (PFGE) were achieved. RESULTS: The main isolated CoNS strains were Staphylococcus epidermidis (45%), Staphylococcus hominis (14%) and Staphylococcus haemolyticus (12.7%). The susceptibility profile of all strains revealed high resistance level to penicillin and oxacillin. PCR detection of oxacillin resistance gene (mecA gene) revealed a higher percentage of positive strains than the classic test (ATB Staph). Slime production test was positive in 60.6% of CoNS strains. PFGE analysis showed the presence of 69 restriction profiles clustered in 56 patterns. CONCLUSIONS: Profiles of all isolates were generally heterogeneous, suggesting independent circulation with some evidence of cross-transmission.