Obasola Ezekiel Fagade

Worldwide emergence of colistin resistance in Klebsiella pneumoniae from healthy humans and patients in Lao PDR, Thailand, Israel, Nigeria and France owing to inactivation of the PhoP/PhoQ regulator mgrB: an epidemiological and molecular study

The emergence of colistin-resistant Klebsiella pneumoniae (CRKP) is a major public health concern worldwide. In this study, the prevalence and molecular basis of colistin resistance in CRKP isolated from healthy individuals and patients in Lao PDR, Thailand, Nigeria and France were investigated. Stool samples were screened by culture for the presence of colistin-resistant Klebsiella spp. Whole-genome sequence analysis was used to decipher the molecular mechanism of colistin resistance in a blaNDM-1-positive in vitro-selected CRKP mutant. PCR amplification and sequencing of the mgrB genetic environment was performed for all CRKP isolates as well as control colistin-susceptible K. pneumoniae (CSKP) isolates recovered from the same stools. A total of 869 stool samples were screened for colistin-resistant Klebsiella spp., yielding 32 CRKP and 2 colistin-resistant Klebsiella oxytoca. Comparative whole-genome sequence analysis revealed that an in vitro-selected CRKP mutant had an insertion sequence in its mgrB gene, as well as missense mutations in other selected clones. Of the 34 colistin-resistant Klebsiella spp. isolates, 14 (41.2%; 13 CRKP and 1 K. oxytoca) from the four countries also had various defects in their mgrB genes, but no such defects were found in the CSKP controls (P<10(-4)). Few mutations were observed in pmrAB compared with mgrB among the CRKP isolates. The worldwide emergence of CRKP is a major public health concern. Detection and surveillance of such strains are warranted to prevent an uncontrollable pandemic. Inactivation of the PhoP/PhoQ regulator gene mgrB is associated with ≥40% of colistin resistance among the CRKP isolates observed in this study.

Synthesis, Physicochemical, and Biological Properties of Nickel(II), Copper(II), and Zinc(II) Complexes of an Unsymmetrical Tetradentate Schiff Base and Their Adducts

Nickel(II), copper(II) and zinc(II) complexes of unsymmetrical Schiff base derived from 2-hydroxy-1-naphthaldehyde, 2,4-pentanedione and p-phenylenediamine of the general formula [M(C10H6OCH:N(C6H4)N:C(CH3)CH:C(CH3)O)], [ML], and their adducts with 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen) have been synthesized and characterized by elemental analyses, conductance, room temperature magnetic susceptibility, and infrared and electronic spectral measurements. The ligand is tetradentate, coordinating via the imine N and enolic O atoms. The magnetic moments and electronic spectra corroborate octahedral geometry for Ni(II) and Cu(II) complexes whereas the Zn(II) Schiff base complex analyzed 4-coordinate and the adduct 6-coordinate. The Ni(II) and Cu(II) complexes incorporated two water molecules each. The antimicrobial properties of the ligand and compounds against Staphylococcus aureus, Streptococcus faecalis, Bacillus sp, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Klebsiella pneumoniae, Acinetobacter sp, Flavobacterium sp, Enterococcus faecalis and Candida albicans are reported. The compounds generally exhibited good activity against the selected organisms. The compound [CuLphen] has comparable activity to gentamycin. The minimum inhibitory concentrations (MICs) of the sensitive compounds are between 1.0–12.0 mg/mL.

Synthesis, characterization and biological studies on unsymmetrical Schiff-base complexes of nickel(II), copper(II) and zinc(II) and adducts with 2,2′-dipyridine and 1,10-phenanthroline

A series of metal(II) unsymmetrical Schiff-base complexes, {M(C10H6OCH:N(CH2)2N : C(CH3)CH : C(CH3)O), where M=Ni(II), Cu(II) and Zn(II)}, and their 2,2′-dipyridine (bipy) and 1,10-phenanthroline (phen) adducts are synthesized and characterized by microanalysis, magnetic susceptibility, conductance, IR and UV-Vis spectra. The ligand coordinates using the N2O2 chromophore to give a two-metal-center four-coordinate square-planar geometry. IR and UV-Vis spectra are consistent with octahedral adducts. The compounds are non-electrolytes in nitromethane and magnetic moments indicate that the complexes are magnetically dilute. The antimicrobial activity of the compounds against ten bacteria and one fungus are reported. The Cu(II) and Zn(II) complexes showed good activity against many of the organisms while their adducts are generally not sensitive. The minimum inhibitory concentrations (MICs) of the sensitive compounds are between 3.0–13.0 mg mL−1.

Emergence of multidrug-resistant Acinetobacter baumannii producing OXA-23 carbapenemase, Nigeria

The objective of our study was to describe the molecular support of carbapenem resistance from randomly selected clinical isolates of multidrug-resistant (MDR) Acinetobacter baumannii as a pilot study from the Hamad Medical Corporation (HMC), Qatar. Results of our report will be used to study carbapenemases using molecular techniques in all isolated MDR A. baumannii. Forty-eight MDR A. baumannii were randomly selected from isolates preserved at HMC. Identification of all isolates was confirmed by matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry. Antibiotic resistance was tested phenotypically by Phoenix and confirmed by Etest. The molecular support of carbapenemases (blaOXA-23, blaOXA-24, blaOXA-58, blaNDM) was investigated by real-time PCR. The epidemiologic relatedness of the isolates was verified by phylogenetic analysis based on partial sequences of CsuE and blaOXA-51 genes. All 48 isolates were identified as A. baumannii and were confirmed to be resistant to most antibiotics, especially meropenem, imipenems, ciprofloxacin, levofloxacin, amikacin, gentamicin and most of the β-lactams; they were sensitive to colistin. All the isolates were positive for blaOXA-23 and negative for the other tested carbapenemase genes. Clonality analysis demonstrated that different lineages were actually circulating in Qatar; and we suggest that an outbreak occurred in the medical intensive care unit of HMC between 2011 and 2012. Here we report the emergence of MDR A. baumannii producing the carbapenemase OXA-23 in Qatar. New Microbes and New Infections

In-vitro studies on the sensitivity pattern of Plasmodium falciparum to antimalarial drugs and local herbal extracts

BackgroundThe resistance of human malaria parasites to anti-malarial compounds has become considerable concern, particularly in view of the shortage of novel classes of anti-malarial drugs. One way to prevent resistance is by using new compounds that are not based on existing synthetic antimicrobial agents.ResultsSensitivity of 100 Plasmodium falciparum isolates to chloroquine, quinine, amodiaquine, mefloquine, sulphadoxine/pyrimethamine, artemisinin, Momordica charantia (‘Ejirin’) Diospyros monbuttensis (‘Egun eja’) and Morinda lucida (‘Oruwo’) was determined using the in vitro microtest (Mark III) technique to determine the IC50 of the drugs. All the isolates tested were sensitive to quinine, mefloquine and artesunate. Fifty-one percent of the isolates were resistant to chloroquine, 13% to amodiaquine and 5% to sulphadoxine/pyrimethamine. Highest resistance to chloroquine (68.9%) was recorded among isolates from Yewa zone while highest resistance to amodiaquine (30%) was observed in Ijebu zone. Highest resistance to sulphadoxine/pyrimethamine was recorded in Yewa and Egba zones, respectively. A positive correlation was observed between the responses to artemisinin and mefloquine (P<0.05), artemisinin and quinine (P<0.05) and quinine and mefloquine (P<0.05). A negative correlation was observed between the responses to chloroquine and mefloquine (P>0.05). Highest anti-plasmodial activity was obtained with the ethanolic extract of D. monbuttensis (IC50 = 3.2nM) while the lowest was obtained from M. lucida (IC50 =25nM).ConclusionsNatural products isolated from plants used in traditional medicine, which have potent anti-plasmodial action in vitro, represent potential sources of new anti-malarial drugs.

Antibiotic resistance and resistance genes in Escherichia coli from poultry farms, southwest Nigeria

INTRODUCTION This study investigated the mechanisms of resistance in 36 E. coli isolated from waste, litter, soil and water samples collected from poultry farms in Southwestern Nigeria. METHODOLOGY Minimum inhibitory concentration (MIC) distributions of the isolates were determined using the methods of the Clinical and Laboratory Standard Institute and resistance genes detected by PCR. RESULTS A total of 30 isolates (94%) showed resistance to more than one antimicrobial. Percentage resistance was: tetracycline 81%, sulphamethoxazole 67%, streptomycin 56%, trimethoprim 47 %, ciprofloxacin 42%, ampicillin 36%, spectinomycin 28%, nalidixic acid 25%, chloramphenicol 22%, neomycin 14%, gentamicin 8%, amoxicillin-clavulanate, ceftiofur, cefotaxime, colistin, florfenicol and apramycin 0%. Resistance genes found among the isolates include bla-TEM (85%), sul2 (67%), sul3 (17%), aadA (65%), strA (70%), strB (61%), catA1 (25%), cmlA1 (13%), tetA (21%) and tetB (17%). Class 1 and 2 integrons were found in five (14%) and six (17%) isolates, respectively, while one isolate was positive for both classes of integrons. Seven out of eight isolates with resistance to ciprofloxacin and MIC ≤ 32 mg/L to nalidixic acid contained qnrS genes. CONCLUSIONS Our findings provided additional evidence that the poultry production environment in Nigeria represents an important reservoir of antibiotic resistance genes such as qnrS that may spread from livestock production farms to human populations via manure and water.

Entomopathogenic fungi in population of Zonocerus variegatus (l) in Ibadan, Southwest, Nigeria

Field survey of population of Zonocerus variegatus revealed a high fungal incidence of 76% when Sporulation tests were carried out on grasshoppers cadaver. Eight fungi with differing incidence rates were isolated. These are Fusarium sp. (8%); Beauveria bassiana (18%); Metarhizium sp. (20%); Aspergillus flavus (10%); Penicillium sp. (13%) Aspergillus niger (14%); Mucor sp. (13%) and unidentified fungus (4%). Fungal isolates virulence bioassay response showed that B. bassiana had the highest lethal time (LT50) of 2 days. Metarhizium sp with LT50 of 5 days was selected in lieu of A. niger which does not prove to be pathogenic to grasshoppers. The results were discussed in relation to the ecology of fungal pathogens of the variegated grasshopper and their possible role in control of Z. variegatus in the agroecosystem of south west, Nigeria.

Spectroscopic, Magnetic and Biological Studies on Some Metal(II) Complexes of 3-(4,6-Dimethyl-2Pyrimidinylamino)-1-Phenyl-2-Butenone and the Mixed Complexes with 2,2′ -Bipyridine and 1,10-Phenanthroline

Mn(II), Co(II), Ni(II) and Cu(II) complexes of the β -ketoimine, [(C 6 H 5 )C:OCH:C(CH 3 )NH(C 6 H 7 N 2 )], and their mixed complexes with 2,2′ -dipyridine (bipy) and 1,10-phenanthroline (phen) are synthesized. The ligand, though containing four donor atoms, was bidentate, coordinating with O and imine N. 1 Hnmr reveals that the ligand exists, predominantly, as ketoimine in polar solvent, but as enolimine in the solid state. All complexes were characterized by microanalyses, magnetic susceptibility, conductance, infrared, and electronic spectral measurements. Spectroscopic and magnetic data are consistent with the adoption of tetrahedral geometry to the Mn(II) and Ni(II) and square planar for Cu(II) complexes while the Co(II) complex and the adducts are octahedral. All the complexes are high-spin, and are non-electrolyte in nitromethane. The compounds exhibited activities against four Gram negative bacilli (Proteus sp, Klebsiella sp, Pseudomonas sp and Salmonella spp); three Gram positive organisms (B. subtilis, B. cereus, S aureus), and a fungus (C. albicans). Except for [CoL 2 (H 2 O) 2 ] and [MnL 2 phen], which have comparable activity with ciprofloxacin against Bacillus subtilis, all the complexes are less active than the antibiotic against all the other microorganisms. Minimum inhibitory concentrations were 3.0–9.0 mg/mL.

Persistence of Rhizobium inoculants originating from Leucaena leucocephala fallowed plots in Southwest Nigeria

Ten core soil samples were collected from experimental plots at IITA, SW Nigeria that were previously inoculated with Rhizobium strains (IRC1045 and IRC 1050) specific for Leucaena leucocephala at two depths; 0–15 cm and 15–30 cm. The control soil samples were collected at similar depths from an adjacent field with no previous history of legume cultivation. Six weeks after planting of L. leucocephala in the soil samples in the greenhouse shoots, roots and nodules were harvested aseptically. Typing of the nodules as well as the identification of the persisting population of the introduced strains were based on the intrinsic resistance of IRC 1045 and IRC 1050 to streptomycin at 500 g/ml and nodules were found to be made up of 100% of previously introduced strains. The potency and competitive ability of the recovered IRC 1045 and IRC 1050 were thus confirmed via the pot experiment and plant reinfection experiment in the greenhouse. At 0–15 cm and 15–30 cm depths 8.0 x 10 4 and 9.0 x 10 4 rhizobia/g of soil were recovered respectively in spite of the 10-year fallow period. Biomass production with the three woody legumes revealed Root and Shoot dry weights of the following order of magnitude Senna siamea > L. leucocephala > Senna spectabilis. This report showed the great potential of application of Rhizobium technology in low input sustainable agricultural practice and environmental pollution abatement for non-use of chemical nitrogen fertilizers.

Comparative analysis of genetic variation among Xanthomonas axonopodis pv manihotis isolated from the western states of Nigeria using RAPD and AFLP

Xanthomonas axonopodis pv manihotis is the causal agent of cassava bacterial blight (CBB) worldwide. CBB disease is a major constraint to cassava cultivation, and losses can be extremely severe in regions where highly susceptible cultivars are grown. To develop an efficient disease management policy, the genetic diversity of the pathogens population must be known. There is dearth of information on the genetic diversity of X. axonopodis pv manihotis population in Nigeria. We used RAPD (random amplified polymorphic DNA) and AFLP (amplified fragment length polymorphism), a PCR-based technique, to characterize the X. axonopodis pv manihotis isolates from the western States of Nigeria. Thirteen strains Xam and 2 reference strains were tested with eight primers combination of AFLP and 4 RAPD primers. RAPD amplified DNA fragment data showed four major clusters at 80 % similarity coefficient level and two strains were not clustered by this analysis. Strains Kwa76A and Ond48A were also separated in the principal component analysis of the same data. Numerical analysis differentiated the AFLP patterns into four distinct clusters and grouped two strains separately at 66 % similarity. PCA assembly grouped the bacterial strains into 4 and one of the strains was singled out from the others. The two DNA analyses techniques seem to be complimentary to one another and informative on the genomic structure of Xam population in Western Nigeria. The genetic analysis presented here contributes to understanding of the Xam population structure in Western Nigeria.