Iruka Okeke | University of Ibadan (original) (raw)

Papers by Iruka Okeke

Journal of the National Medical Association, 2007

To determine the prevalence and disease association of Helicobacter pylori (H. pylori) in dyspept... more To determine the prevalence and disease association of Helicobacter pylori (H. pylori) in dyspeptic patients in southwest Nigeria. Obafemi Awolowo University Teaching Hospitals Complex, Ile-lfe, Nigeria. Consecutive dyspeptic patients for upper gastrointestinal endoscopy from January 1996 to March 1997 were investigated for H. pylori in gastric biopsy by histopathology and culture. Patients without gastroduodenal ulcerations or neoplastic lesions constituted the nonulcer dyspeptic (NUD) group. 138 (92 males, 46 females) patients aged 4.5-85 years [mean (7) = 45+/-SD 17.8 years] who had upper gastrointestinal endoscopy were analyzed for presence of H. pylori. Eighty-three had histopathology alone, while 55 others had both histology and culture. Endoscopic diagnosis included duodenal ulcer (DU) (n=35, 23%); gastric ulcer (n=4, 3%); gastric cancer (n=14, 9%); NUD, including gastritis (n=49, 32%); duodenitis (n=47, 31%); and normal (n=16, 11%). Overall, H. pylori was positive in 107 of ...

Trends in Microbiology, 2008

International Journal of Aromatherapy, 2004

Phytotherapy Research, 1999

The 50% aqueous ethanol extract of Alchornea cordifolia (Schum and Thonn) Muell. Arg. leaf was sc... more The 50% aqueous ethanol extract of Alchornea cordifolia (Schum and Thonn) Muell. Arg. leaf was screened for activity against 74 microbial strains representing aerobic, facultative and anaerobic bacteria as well as fungi. The panel of test strains included organisms from culture collections as well as clinical and environmental isolates. A concentration of 5 mg/mL of extract inhibited 36.5% of the isolates and 95.9% were inhibited by a concentration of 20 mg/mL. Only three strains, all filamentous fungi, were not susceptible to 40 mg/mL of the extract, the highest concentration tested. The extract showed the best activity against gram-positive bacteria and yeasts with inhibitory concentrations against these organisms being under 5 mg/mL. The results demonstrate that the A. cordifolia extract has a very broad spectrum of activity and suggests that it may be useful in the treatment of various microbial infections. # 1999 John Wiley & Sons, Ltd.

The Lancet Infectious Diseases, 2001

Journal of Travel Medicine, 2006

Antimicrobial use has been correlated with the prevalence of resistance among microorganisms. Res... more Antimicrobial use has been correlated with the prevalence of resistance among microorganisms. Resistant strains are particularly likely to be selected when antibiotics are used inappropriately. This is a common feature in many developing countries, where antimalarials and antibiotics are available from multiple sources without prescription and professional health care is expensive or unavailable. 1,2 Increasing numbers of African residents make short-term visits to countries where antibiotics are only available by prescription. We sought to determine how commonly these individuals traveled with antimicrobials purchased in their own countries; how often they considered themselves infected abroad; and what was their primary response to presumed infection.

Journal of Clinical Microbiology, 2004

Enteroaggregative Escherichia coli (EAEC) strains are etiologic agents of acute and persistent di... more Enteroaggregative Escherichia coli (EAEC) strains are etiologic agents of acute and persistent diarrhea. In this study, the results of phenotypic assays suggested that EAEC strains possess specialized iron acquisition systems. Genes required for the synthesis (iucA) or transport (fepC) of siderophores, and genes encoding siderophore (fyuA, ireA, and iroN) or heme transport (chu) receptors or hemoglobin proteases (pic and hbp), were sought in EAEC strains which have been characterized with respect to known virulence genes and phylogeny. The chuA, iucA, fyuA, fepC, and pic genes were detected in 33, 76.2, 85.7, 33, and 61.9% of these EAEC strains, respectively, and the other genes were absent. The majority of EAEC strains possessed genes encoding multiple iron transport systems, and there was no phylogenetic correlation in the distribution of the majority of these loci, as is typical for EAEC. The notable exceptions were chuA and fepC (which is associated with the prrA-modA-fepC pathogenicity island); these genes were restricted to the EAEC2 and DAEC2 phylogenetic groups, which could represent pathogenic subsets. When collections of EAEC strains isolated during casecontrol studies in Nigeria and Brazil were examined, no association of the presence of either chuA or iucA alone with diarrhea was seen, but both genes together were present in significantly more strains from cases than from controls in the Nigerian collection (P < 0.05). It is possible that the presence of both genes marks at least some virulent strains. The data also demonstrate geographical variation in the association of iron utilization genes with disease in EAEC.

Journal of Bacteriology, 2007

A novel and functional conjugative transfer system identified in O119:H2 enteropathogenic Escheri... more A novel and functional conjugative transfer system identified in O119:H2 enteropathogenic Escherichia coli (EPEC) strain MB80 by subtractive hybridization is encoded on a large multidrug resistance plasmid, distinct from the well-described EPEC adherence factor (EAF) plasmid. Variants of the MB80 conjugative resistance plasmid were identified in other EPEC strains, including the prototypical O111:NM strain B171, from which the EAF plasmid has been sequenced. This separate large plasmid and the selective advantage that it confers in the antibiotic era have been overlooked because it comigrates with the virulence plasmid on conventional gels.

Infection, Genetics and Evolution, 2011

In recent years, the frequency of cholera epidemics across Africa has increased significantly wit... more In recent years, the frequency of cholera epidemics across Africa has increased significantly with thousands of people dying each year. However, there still exists a lack of information concerning the Vibrio cholerae O1 lineages driving early and contemporary epidemics since the seventh cholera pandemic started in the continent. This compromises the understanding of the forces determining the epidemiology of cholera in Africa and its control. This study aimed to analyze a collection of V. cholerae O1 strains from the beginning of the seventh cholera pandemic in Ghana and to compare them with recent isolates to understand the evolution of the cholera epidemic in Ghana. V. cholerae O1 strains were characterized by means of Multilocus Sequence Analysis (MLSA), genes from the virulence core genome (VCG), and genes related to the choleragenic phenotype. Our results revealed two major clusters of Ghanaian V. cholerae O1 strains, El Tor and Amazonia/Ghana. Concerning the virulence genes, all strains harbored the set of VCG and most were positive for VSP-II genomic island. The ctxB gene of the contemporary strains was characterized as Altered El Tor. The strains from 1970 to 1980 were susceptible to all antibiotics tested, except for the Amazonia/Ghana cluster that was resistant to aminoglycosides and carried the class 2 integron with the sat2-aadA1 arrangement. This study showed that distinct V. cholerae O1 were the determinants of cholera outbreaks in Ghana. Thus, in endemic regions, such as Africa, cholera can be caused by various V. cholerae O1 genotypes.

Gut Pathogens, 2011

Background: Enteroaggregative Escherichia coli (EAEC) are important diarrhoeal pathogens that are... more Background: Enteroaggregative Escherichia coli (EAEC) are important diarrhoeal pathogens that are defined by a HEp-2 adherence assay performed in specialist laboratories. Multilocus sequence typing (MLST) has revealed that aggregative adherence is convergent, providing an explanation for why not all EAEC hybridize with the plasmidderived probe for this category, designated CVD432. Some EAEC lineages are globally disseminated or more closely associated with disease. Results: To identify genetic loci conserved within significant EAEC lineages, but absent from non-EAEC, IS3-based PCR profiles were generated for 22 well-characterised EAEC strains. Six bands that were conserved among, or missing from, specific EAEC lineages were cloned and sequenced. One band corresponded to the aggR gene, a plasmid-encoded regulator that has been used as a diagnostic target but predominantly detects EAEC bearing the plasmid already marked by CVD432. The sequence from a second band was homologous to an open-reading frame within the cryptic enterohaemorrhagic E. coli (EHEC) O157 genomic island, designated O-island 62. Screening of an additional 46 EAEC strains revealed that the EHEC O-island 62 was only present in those EAEC strains belonging to the ECOR phylogenetic group D, largely comprised of sequence type (ST) complexes 31, 38 and 394.

Emerging Infectious Diseases, 2007

Enteroaggregative Escherichia coli (EAEC) are heterogeneous, diarrheagenic E. coli. Of EAEC strai... more Enteroaggregative Escherichia coli (EAEC) are heterogeneous, diarrheagenic E. coli. Of EAEC strains from Nigeria, 10 independent antimicrobial-resistant isolates belonged to the multilocus sequence type 69 clonal complex, to which uropathogenic E. coli clonal group A belongs. This fi nding suggests a recent common ancestor for these distinct groups of pathogenic E. coli.

Emerging Infectious Diseases, 2000

... The future usefulness of these drugs will, however, depend on effective interventions to halt... more ... The future usefulness of these drugs will, however, depend on effective interventions to halt the selection and spread of resistance among enteric organisms. Acknowledgments We thank Bukola Quadri, Oladipo Ojo, and Kemi Adeyemi for technical assistance. ...

Emerging Infectious Diseases, 1999

Drugs of the Future, 2004

... Although many recent studies suggest that chewing sticks are more effective than the toothbru... more ... Although many recent studies suggest that chewing sticks are more effective than the toothbrush in the maintenance of oral hygiene (7-10), Norton and Andy (11) reported more plaque formation and gingival bleeding in chewing stick users alone and Eid et al. ...

BMC Microbiology, 2011

Background: Antimicrobial resistance is under-documented and commensal Escherichia coli can be us... more Background: Antimicrobial resistance is under-documented and commensal Escherichia coli can be used as indicator organisms to study the resistance in the community. We sought to determine the prevalence of resistance to broad-spectrum antimicrobials with particular focus on the quinolones, which have recently been introduced in parts of Africa, including Ghana.

BMC Microbiology, 2009

The roles of diffusely-adherent Escherichia coli (DAEC) and enteroaggregative E. coli (EAEC) in d... more The roles of diffusely-adherent Escherichia coli (DAEC) and enteroaggregative E. coli (EAEC) in disease are not well understood, in part because of the limitations of diagnostic tests for each of these categories of diarrhoea-causing E. coli. A HEp-2 adherence assay is the Gold Standard for detecting both EAEC and DAEC but DNA probes with limited sensitivity are also employed.

BMC Microbiology, 2010

We recently observed an association of resistance with a certain enteropathogenic Escherichia col... more We recently observed an association of resistance with a certain enteropathogenic Escherichia coli (EPEC) serotypes and identified a conjugative plasmid, similar to plasmid pED208, that was conserved among archival O111:H2/NM and O119:H2 strains of diverse geographical origin. In this study, we sought to determine the prevalence and distribution of this plasmid among a collection of EPEC isolates from Brazil, as well as to study the susceptibilities of these isolates to antimicrobial agents. Results: Resistance was more commonly seen in typical EPEC than atypical strains. The most prevalent resistances were to ampicillin, tetracycline, streptomycin and the sulfonamides. Markers for the EPEC conjugative multiresistance plasmid, were detected in 21 (30%) of typical but only 4 (5%) of atypical strains (p = 0.001, Chisquared test). This plasmid, previously reported from only O111 and O119 strains was found in O55 and O127 strains and was associated with the presence of class 1 integrons. Conclusion: Our data suggest a limited but expanding host range for the EPEC resistance plasmid.

Applied and Environmental Microbiology, 2009

We demonstrate that enhanced lysozyme resistance of enteropathogenic Escherichia coli requires th... more We demonstrate that enhanced lysozyme resistance of enteropathogenic Escherichia coli requires the plasmid-encoded regulator, Per, and is mediated by factors outside the locus for enterocyte effacement. EspC, a Per-activated serine protease autotransporter protein, conferred enhanced resistance on nonpathogenic E. coli, and a second Per-regulated, espC-independent lysozyme resistance mechanism was identified.

Antimicrobial resistance is becoming increasingly important in high-burden infectious diseases in... more Antimicrobial resistance is becoming increasingly important in high-burden infectious diseases in Africa. Resistance to affordable antimalarials and antibacterials has worsened patient prognosis, increased health-care costs, and is a barrier to effective health care. This chapter outlines the African situation for a few infectious diseases and discusses mitigating factors, particularly selective pressure from antimicrobial use. Overuse of antimicrobials for prevention and

International Journal for Parasitology, 1999