Phenotypic and genotypic characterization of plasmid-mediated AmpC beta-lactamases in enteric Gram-negative bacteria from patients with lower respiratory tract infections in a tertiary hospital, southwest Nigeria

Background: AmpC or class C or group 1 beta lactamases are class C cephalosporinases that hydrolyse a wide variety of beta-lactam antibiotics including alpha methoxy beta-lactams (cefoxitin), narrow and broad spectrum cephalosporins. This study was conducted to characterize plasmid-mediated AmpC producing enteric Gram- negative bacteria from patients with lower respiratory tract infections in Obafemi Awolowo University Teaching Hospital Complex (OAUTHC) Ile Ife, Osun State, Nigeria Methodology: A total of 149 patients with clinical features of lower respiratory tract infections (LRTI) were selected by simple random sampling for the study. All Gram-negative isolates recovered from standard microbiological cultures of respiratory specimens of these patients were tested against cefoxitin, third generation cephalosporins (3GCs), and other antibiotics using the disc diffusion AST method, and also screened for production of AmpC beta-lactamases phenotypically by the CLSI method. Plasmid DNA extraction was carried out on twenty-nine cefoxitin-resistant selected isolates using the Kado and Lin method, while genotypic detection of plasmid-mediated AmpC gene was carried out by the polymerase chain reaction (PCR) assay. Results: The results showed that 204 (43.3%) of 471 isolates recovered from the 149 selected patients were resistant to 3GC in the AST assay, among which 121 (59.3%) were resistant to cefoxitin, and 189 of the 471 isolates (40.1%) were AmpC producers. The AmpC producers concurrently showed multiple resistance pattern to other antibiotics tested in this study. Ninety six percent of the 29 selected isolates for plasmid analysis contained plasmids, 45% of which amplified positive on PCR for CMY, 38% for FOX, and 31% for ACC types of AmpC genes. Conclusion: This study showed a high degree of antibiotic resistance among enteric Gram-negative bacteria recovered from patients with LRTIs, as well as high degree of plasmid-encoded AmpC genes responsible for this high antibiotic resistance among the isolates. Proper antibiotic policy and regulation are required to limit the spread of plasmid mediated AmpC ß-lactamase

Plasmid curing in multi-drug resistant hospital and community uropathogenic Escherichia coli

ABSTRACT: Escherichia coli is the most prevalent organism responsible for urinary tract infections (UTIs) in hospital and community sources. The present study was carried out to detect multi drug resistant (MDR) E coli from urine samples and the role of plasmids in drug resistance. One hundred urine samples were collected from the hospital and community within the University of Port Harcourt. Microscopic and chemical examination was carried out on the urine samples. E coli were isolated and antibiotic sensitivity test was carried out on the isolates, the resistant E. coli were cured by acridine orange and further subjected susceptibility testing. Result obtained from the study showed 35% E. coli recovered from community samples and 65% from hospital samples. Antibiotic sensitivity testing before plasmid curing showed high level of resistance to Augmentin (99%), Cefuroxime (92%), Ceftazidime (78%) and Cefixime (71%). The lowest level of resistance was reported in Gentamicin (15%) and Nitrofurantoin (19%). All the isolates were resistant to Augmentin but upon plasmid curing the resistant rate of isolates to eight antibiotics reduced. Our findings showed that Augmentin and Cefuroxime (62 and 31%) were still resistant after the plasmids of the isolates were cured. For hospital and community sources Nitrofurantoin (1; 0%), Ceftazidime (3; 8%), Ciprofloxacin (1%), Gentamicin (10%) and Ofloxacin (10%). Sixty-two (62) percent of the hospital isolates were resistant to three or more antibiotics while 60% of the community isolates were multidrug resistant. Our study thus concludes that plasmids alone are not responsible for the resistance to antibiotics exhibited by E,coli from urine samples. Antibiotics should be produced to target genes that are responsible for resistance to prevent the spread of drug resistant organisms

Antibiotic Susceptibility and Plasmid Profiles of Shigella Species in Sudan

This study was carried out to determine the antibiotic susceptibility; plasmid profile and conjugative abilities of Shigella species isolated from different towns in Sudan during 2005-2007.Methods:Stool specimens were collected in Carry Blair transport medium from patients presenting with diarrhea from different sites in Sudan between the years 2005-2007.All specimens were inoculated on Mac Conkey's agar and Xylose Lysine Dioxycholate (XLD) (Mast group Ltd. Merseyside U.K.). Bacteria was isolated and subjected to different antibiotics to detect sensitivity and transference of resistance.Results:One hundred and fourteen Shigella isolates were included in the study.Eighty (70.1) were Shigella flexeneri representing the dominant isolate; followed by 20 (17.5) isolates of Shigella dysenteriae; 9 (7.9) Shigella sonnei and 5 (4.5) Shigella boydii.Most of the isolates showed resistance to streptomycin (70);tetracycline (52) and co-trimoxazole (43).They were highly sensitive to norfloxacin (97); nalidixic acid (95); gentamicin (89) and chloramphenicol (77).Multi-drug resistance to two or more antibiotics was apparent in most of the isolates (64; 56.1).Fifty nine of the resistant Shigella isolates were studied for their ability to transfer resistance to the donor E. coli K12 by conjugation.Of these;six were able to transfer resistance to streptomycin; tetracycline and co-trimoxazole.Extraction of the plasmid DNA from both donors and trans-conjugants showed a single type of plasmid with a molecular weight of 4.6 Kb.Conclusion The transfer of multi-drug resistant plasmids and the emergence of antibiotic Shigella and other bacterial species should raise the awareness and the seriousness of the uncontrolled (unsupervised) use of antibiotics in the medical practice

Vibrio cholerae a Madagascar : a propos d'une souche multiresistante

"Multiresistant Vibrio cholerae strain in Madagascar : report of the first case"": Madagascar was cholera free until March 1999. The first case was reported in Mahajanga; anorth west coast harbor. Ten months later and despite a massive use of tetracycline as proplylactic drug; cholera had reached every region of the island.All suspected cholera samples were analysed at the Pasteur Institute of Madagascar where susceptibility to tetracycline was systematically performed. On February 2000; a multidrug resistant strain of V. cholerae was isolated. We studied this strain by performing Minimal Inhibitory Concentration (MIC) and by plasmidic and conjugative assay.As the original strain; this multiresistant V. cholerae showed a resistance to cotrimoxazole; to streptomycin and chloramphenicol but; in addition to; appeared strongly resistant to ampicillin and tetracycline. This strain harboured a 26 kb self-transmissible plasmid. Conjugation tests showed the possibility of plasmidic segregates or acquisition of two different plasmids. The weak transfer rate could explain why we have isolated only one multiresistant strain. The emergence of a such multiresistant strain should encourage the medical authorities to reinforce the epidemic survey in every medical Malagasy district and to carry out new antimicrobial surveys to describe the mechanisms of the spread of these resistances."