Aims: Assessment of the antibiotic resistance pattern and detection of genes responsible for the β-lactam resistance in enterobacteria isolated from different sources was carried out in the course of the study.
Place and Duration of Study: Samples from different sources in Iwo, Osun State, Nigeria including Abattoir and Cow ranch. The study was done August 2015 to May 2016.
Methodology: Isolation was done on nutrient agar, xylose lysine deoxycholate (XLD) and identified using standard procedures. Antibiotic multidisc containing the following ceftazidime (30 µg), cefruroxime (30 µg), gentamicin (10 µg), ciprofloxacin (5 µg), ofloxacin (5 µg), augmentin (30 µg), nitrofurantoin (300 µg), and ampicillin ( ) were used to study the resistance patterns of the bacteria. Polymerase chain reaction (PCR) method was carried out to screen for CTX-M gene in beta-lactam resistant isolates and statistical analyses were carried out using the analysis of variance test (ANOVA) and the PAST (paleontology statistics) software analytical package where applicable.
Results: Fifty-two (52) entrobacteria consisting of nine genera (9) were isolated and identified, Serratia (13), Enterobacter (11), Klebsiella (6), E. coli (5), Proteus (5), Salmonella (3), Shigella (3), Citrobacter (3), and Yersinia (3). The highest resistance observed by the isolates was to ampicillin (80.7%) followed by augmentin (40%) and 33% resistance of the isolates to cefuroxime, while all the isolates were sensitive to ceftazidime, gentamicin, ofloxacin, ciprofloxacin and nitrofurantoin. Nineteen of the isolates were resistant to three or more of the tested antibiotics i.e. multiple resistance while five of the multidrug resistant isolates show the presence of CTX-M β-lactam resistance gene which seems to be responsible for their resistance to the β-lactam antibiotic tested.
Conclusion: There are a number of organisms in the environment that have developed multiple resistances to several antibiotics and in view of this thwart treatment; of major concern are the Enterobacteriaceae family in which new resistance characteristics have been discovered leading to increasing resistance to standard available drug therapies.
Three new Schiff bases, (Z)-2-(4-(dimethylamino)benzylidene)-N-methylhydrazinecarbothioamide (PDM), (Z)-2-(2-hydroxy-5-nitrobenzylidene)-N-methylhydrazinecarbothioamide (5NS) and (Z)-2-(4-cyanobenzylidene)-N-methylhydrazinecarbothioamide (4CN) of thiosemicarbazone-benzaldehyde derivatives were synthesized by condensation reaction. These compounds were formed from the reaction of 4-methyl-3-thiosemicarbazide with p-dimethylaminobenzaldehyde, 5-nitrosalicylaldehyde and 4-formylbenzonitrile respectively. The molecules synthesized were screened against bacterial isolates; Gram-positive (Staphylococcus aureus and Bacillus cereus), and Gram-negative (Klebsiella pnuemoniae and Pseudomonas aeruginosa) bacteria using agar well diffusion technique, supported by molecular docking and theoretical analysis through computational approach adopting a coupled DFT-B3LYP and 6-31G(d) basis set. The in-vitro antibacterial studies proofed that the compounds have a broad-spectrum antibacterial activity against the bacterial isolates while 5NS (21.0 mm) and PDMA (9.5 mm) have higher antibacterial activities than the standard drug, streptomycin against Staphylococcus aureus (16.5 mm) and Pseudomonas aeruginosa (9.0 mm) respectively. Theoretical studies and molecular docking established the fact that these Schiff bases could be explored further as bioactive compounds against bacterial infections and also as corrosion inhibitors of metals in the oil and gas industry.
Graphical abstract
The emerging field of forensic biology has attempted to solve certain problems encountered when estimating post-mortem interval (PMI) by using predictable changes in the microbial and arthropod community structure. Pig (Sus scrofa) carcasses are widely used as animal models in clinical human studies. The objective of this study was to identify bacteria from the skin surface of pig carcass for possible use in forensic investigation.
Three pigs (a suitable human substitute) were collected from a local farm and killed by suffocation and further place in a bush land for decomposition. 24hours later skin samples were collected and transported to the laboratory for the isolation of bacteria using standard pour plate techniques and identified using Bergey’s manual of systemic bacteriology. The experiment was conducted in February 2019 during the dry season of the year with an average temperature of 23.50c and relative humidity of 60.8%
A total of fourteen (14) isolates were gotten from the pig carcass samples out of which four (4) were Gram-positive bacteria and the remaining ten (10) were Gram-negative. Staphylococcus spp. (28.6%) was the most abundant while Salmonella sp., Serratia sp., Klebsiella sp., Citrobacter sp. and Proteus sp. occurred at 14.3% each.
This study focus on the type of bacteria communities during a decomposition process which will help provide baseline information in the application of forensic biology to determination of nature of death, abuse or neglect.
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