Stella I. Smith

Effects of Ocimum gratissimum L. essential oil at subinhibitory concentrations on virulent and multidrug‐resistant Shigella strains from Lagos, Nigeria

Ocimum gratissimum leaf extracts have been extensively demonstrated to be effective against the various aetiologic agents of diarrhoea, including Shigellae. However, the mechanism of the shigellocidal action of this plant remains to be understood. This study investigated the effects of O. gratissimum essential oil (EO) at subinhibitory concentrations of 0.75 and 1.0 μg/ml on virulence and multidrug‐resistant strains of 22 Shigella isolates from Nigeria. Compared with untreated Shigella strains, O. gratissimum EO caused significant decreases (p<0.01) in extracellular protease activity, o‐lipopolysaccharide rhamnose content and incidence of invasiveness mediated as keratoconjunctivitis in guinea pig. The disparity in extracellular protease activity and o‐lipopolysacharide rhamnose between the two treatment groups was also found to be significant (p<0.05), suggesting greater anti‐virulent effects of O. gratissimum oil at 1.0 μg/ml. Antibiotic susceptibility testing revealed that the EO of O. gratissimum reduced the MICs of antibiotics to which Shigellae showed resistance by 9.8–53.1% and fluoroquinolones by 18.2–45.5%. The results of this study strongly suggest inhibition of extracellular protease and expression of O‐LPS rhamnose in Shigellae by O. gratissimum EO. The future use of O. gratissimum– antibiotic combinations as a therapeutic measure against shigellosis is discussed.

Prevalence of Helicobacter pylori vacA, cagA and iceA genotypes in Nigerian patients with duodenal ulcer disease

Distinct virulence factors of Helicobacter pylori have been associated with clinical outcome of the infection; however, considerable variations have been reported from different geographic regions. Data on genotypes of African H. pylori isolates are sparse. The aim of this study was to determine the prevalence of specific genotypes of H. pylori in Nigerian patients with duodenal ulcer and non-ulcer dyspepsia. H. pylori was cultured from endoscopic biopsies obtained from 41 Nigerian patients (19 with duodenal ulcer, 22 with non-ulcer dyspepsia). The vacA alleles, cagA and iceA genotypes were determined by PCR. The vacA s1,m1 and s1,m2 genotypes were found in 26.3% and 22.7%, and in 73.7% and 72.7% of H. pylori isolates from patients with duodenal ulcer and non-ulcer dyspepsia, respectively. The iceA1 genotype was present in 94.7% and 86.4% of isolates from duodenal ulcer and non-ulcer dyspepsia patients, respectively. cagA+ infection was found predominantly (> 90%) in Nigerian H. pylori isolates irrespective of the clinical diagnosis. In conclusion, vacA s1,m2, iceA1 and cagA+ are common genotypes of H. pylori isolated from Nigerian patients. As in several other developing countries there seems to be no association between these genotypes and duodenal ulcer disease.

Helicobacter pylori exploits human CEACAMs via HopQ for adherence and translocation of CagA

Helicobacter pylori (Hp) strains that carry the cag type IV secretion system (cag-T4SS) to inject the cytotoxin-associated antigen A (CagA) into host cells are associated with peptic ulcer disease and gastric adenocarcinoma. CagA translocation by Hp is mediated by β1 integrin interaction of the cag-T4SS. However, other cellular receptors or bacterial outer membrane adhesins essential for this process are unknown. Here, we identify the HopQ protein as a genuine Hp adhesin, exploiting defined members of the carcinoembryonic antigen-related cell adhesion molecule family (CEACAMs) as host cell receptors. HopQ binds the amino-terminal IgV-like domain of human CEACAM1, CEACAM3, CEACAM5 or CEACAM6 proteins, thereby enabling translocation of the major pathogenicity factor CagA into host cells. The HopQ–CEACAM interaction is characterized by a remarkably high affinity (KD from 23 to 268 nM), which is independent of CEACAM glycosylation, identifying CEACAMs as bona fide protein receptors for Hp. Our data suggest that the HopQ–CEACAM interaction contributes to gastric colonization or Hp-induced pathologies, although the precise role and functional consequences of this interaction in vivo remain to be determined.

Associated risk factors and pulsed field gel electrophoresis of nasal isolates of Staphylococcus aureus from medical students in a tertiary hospital in Lagos, Nigeria

Staphylococcus aureus infections are growing problems worldwide with important implications in hospitals. The organism is normally present in the nasal vestibule of about 35% of apparently healthy individuals and its carriage varies between different ethnic and age groups. Staphylococcal nasal carriage among health workers is particularly important to establish new clones and track origin of infections during outbreak situations. To determine the carriage rate and compare the pulsed field gel patterns of the strains, nasal swabs were collected from 185 medical students in a teaching hospital in Lagos, Nigeria. Isolates of S. aureus were tested for heamolysin production, methicillin sensitivity and Pulsed Field Gel Electrophoresis (PFGE) was performed. The results showed S.aureus nasal carrier rate of 14% with significant rate among males compared to females. All the isolates produced heamolysin. Antibiotic susceptibility pattern revealed that majority of the isolates was susceptible. Five strains (19%) harboured resistant determinants to penicillin and tetracycline. None of the strains was resistant to methicillin. 44% of the isolates typed by PFGE had type B, the most predominant pulsotype. PFGE A clone exhibited a single resistance phenotype suggesting a strong clonal relationship that could punctual an outbreak in the hospital. The results speculate that nasal carriage among medical personnel could be a function of various risk factors. Personal hygiene and behaviour may however be the means to reducing colonization and spread of S.aureus in our hospitals.

Prevalence of EHEC O157:H7 in patients with diarrhoea in Lagos, Nigeria

The prevalence of sorbitol‐nonfermenting Escherichia coli O157:H7 (EHEC) was assessed in 100 patients with diarrhoea by stool culture on sorbitol MacConkey agar. The cytotoxicity of the EHEC strains was analysed by Vero cell assay and the antimicrobial susceptibility pattern of the isolates was determined. Detection rate of EHEC O157:H7 was 6%. Five of the six patients were males. Three of the isolates were from children and one was from a teenager. All strains induced cytotoxic effects in the Vero cell assay. All isolates were susceptible to most of the antimicrobials tested. The results showed that diarrhoea caused by EHEC O157:H7, a potentially life‐threatening pathogen, has remained common particularly among the child population of Lagos during the past 10 years (5). There must therefore be adequate meat and food inspection to improve the general hygiene of local fast food restaurants, so‐called ‘bukkas’, which are regarded as likely sources of infection.

A comprehensive analysis of Helicobacter pylori plasticity zones reveals that they are integrating conjugative elements with intermediate integration specificity

BackgroundThe human gastric pathogen Helicobacter pylori is a paradigm for chronic bacterial infections. Its persistence in the stomach mucosa is facilitated by several mechanisms of immune evasion and immune modulation, but also by an unusual genetic variability which might account for the capability to adapt to changing environmental conditions during long-term colonization. This variability is reflected by the fact that almost each infected individual is colonized by a genetically unique strain. Strain-specific genes are dispersed throughout the genome, but clusters of genes organized as genomic islands may also collectively be present or absent.ResultsWe have comparatively analysed such clusters, which are commonly termed plasticity zones, in a high number of H. pylori strains of varying geographical origin. We show that these regions contain fixed gene sets, rather than being true regions of genome plasticity, but two different types and several subtypes with partly diverging gene content can be distinguished. Their genetic diversity is incongruent with variations in the rest of the genome, suggesting that they are subject to horizontal gene transfer within H. pylori populations. We identified 40 distinct integration sites in 45 genome sequences, with a conserved heptanucleotide motif that seems to be the minimal requirement for integration.ConclusionsThe significant number of possible integration sites, together with the requirement for a short conserved integration motif and the high level of gene conservation, indicates that these elements are best described as integrating conjugative elements (ICEs) with an intermediate integration site specificity.

Prevalence of a marker of active helicobacter pylori infection among patients with type 2 diabetes mellitus in Lagos, Nigeria

BackgroundThere appears to exist a potentially important interplay between diabetes mellitus (DM) and Helicobacter pylori (H. pylori) infection. Findings from previous studies have been conflicting. Only a few studies have examined the topic in a sub-Saharan African population. This study sought to determine the prevalence of H. pylori infection among Type 2 diabetes mellitus (T2DM) patients in Lagos, Nigeria.FindingsH. pylori infection was detected in 18% of T2DM patients and 13% of controls but there was no statistical significance in this difference (p = 0.52). The prevalence of H. pylori was neither associated with the known duration of T2DM nor was it associated with age, gender, body mass index (BMI), smoking status. T2DM was not shown to be a risk factor independently associated with risk for H. pylori infection (OR = 0.87, 95% CI = 0.58-1.31, p = 0.57).ConclusionsThe lack of a statistical significant difference between the H. pylori infection rates in T2DM patients and controls suggests that the infection is not increased in T2DM. Larger studies need to be conducted to confirm the study findings.

High amoxycillin resistance in Helicobacter pylori isolated from gastritis and peptic ulcer patients in western Nigeria.

omeprazole or bismuth for 2 weeks. Treatment failure has been reported in some patients, and in others there is usually the attendant problem of the patients not coming back to the clinic, most because of the cost and the lack of free health care in Nigeria. There is no documented eradication rate of H. pylori in Nigeria. The main problem is lack of ability to isolate the organism in most laboratories, as a result of the specialized conditions required for isolation. Therefore, the few patients who have follow-up endoscopy are usually checked on the basis of the CLO test and, occasionally, histology. There have been few documented cases of H. pylori from the north of the country and the majority of biopsy samples were not cultured,2,3 although our study (from the western region) has documented work on the CLO test, culture, and gram staining.4 In northern Nigeria, Holcombe et al.2,3 reported the prevalence of H. pylori by histology to be 87%, with culture (62% and 72.7% respectively) being positive for H. pylori. From our culture study of H. pylori, 27% of patients with gastritis and peptic ulcer in western Nigeria were positive.4 One of the reasons for the high metronidazole resistance in this part of the world is that medical practitioners, especially those in private practice, prescribe metronidazole; metronidazole for the treatment of parasitic infections and urinary tract infections (UTI). Ampicillin is a drug that is widely abused in this part of the world; it is generally sold in the streets (especially the 250-mg and 500-mg doses). Amoxycillin is also sold in the streets. The possibility of bacterial strains acquiring resistance to amoxycillin and ampicillin is strong, because both are penicillins and â-lactamase agents. Colonization of the stomach with ampicillin and, possibly, other â-lactam-resistant bacteria may also lead to the transfer of amoxicillin resistance to H. pylori. To determine resistance to antibiotics, the disk diffusion technique is cheap and reliable for use, especially in developing countries where the E test and determining the minimum inhibitory concentration Helicobacter pylori has been proposed as the etiologic agent of gastric and duodenal ulcers, antral gastritis, and some gastric carcinoma.1 It has been noted that the eradication of H. pylori leads to the permanent cure of peptic ulcer disease.1 In Nigeria, most often, blind therapy, or what is referred to as empirical treatment, is given to patients who have endoscopic symptoms of ulcer or gastritis and are Campylobacter like organisms (CLO) positive, and, to a lesser extent, show histological gastritis. The study therefore aimed at carrying out in-vitro antibiotic susceptibility testing on the H. pylori strains isolated from patients presenting with peptic ulcer and gastritis in Nigeria, in particular using the antibiotics commonly prescribed for these patients to prove their efficacy and or to explain the reasons for observed treatment failures. All the isolates were resistant to amoxycillin, ampicillin, piperacillin, erythromycin, tetracycline, and metronidazole. All the strains had zone sizes of 7.6mm or less with these agents. The majority (75%) of the isolates were resistant to cefuroxime. All were sensitive to ofloxacin, ciprofloxacin, and norfloxacin. All were moderately sensitive to imipenem. Twenty-five percent of the strains were sensitive to gentamicin and kanamycin (Table 1). No â-lactamase activity was detected in any of the H. pylori strains. This study showed that all the H. pylori isolated from western Nigeria were resistant to ampicllin, amoxycillin, tetracycline, and metronidazole. Unfortunately, two of these drugs (metronidazole and amoxycillin) form the crux of the drugs used for the treatment of H. pylori infections in Nigeria. In Nigeria, as a result of the high rate of drug abuse, clinicians give the following drug combinations: 1 g amoxycillin three times daily for 2 weeks; 400 mg metronidazole daily for 10 days, and

Application of stool-PCR for the diagnosis of Helicobacter pylori from stool in Nigeria- a pilot study

There are various methods for detection of Helicobacter pylori and the gold standard for non-invasive detection is the urea breath test (UBT). The aim of the study is therefore to detect H. pylori from the stool of patients with dyspepsia by PCR and compare results obtained with UBT. A total of 97 stool samples from patients presenting with dyspeptic symptoms in Lagos University Teaching Hospital (LUTH) were screened for urea breath test (UBT) and the presence of H. pylori DNA using stool-PCR. Out of 97 stool samples analysed, 38 (39.2%) were positive for Helicobacter spp. and 20 (20.6%) positive for H. pylori by PCR, through amplification of 16S rRNA and glmM genes respectively. Of the 20 positive by glm M gene, the cagA gene was detected in 8 (40%) samples, while 47 (48.5%) out of 97 stool samples were positive for H. pylori by UBT. The sensitivity and specificity of the glmM gene compared with UBT as the gold standard is 42.6% and 100% respectively. The positive predictive value (PPV) was 100% while the negative predictive value (NPV) was 60%.The method may be useful for detecting H. pylori from stool amongst children especially where most hospitals lack endoscope for children although the method is expensive.

Diagnostic methods for typhoid fever in Nigeria.

Abstract In this study, 65 patients are screened for Salmonella typhi by conventional culture and the Widal test. In addition, the patients undergo full blood count are screened for malaria parasites. Of the 65 patients, 50 report febrile conditions, while the remaining 15 are used as a control population. In the febrile group, 13 (26%) were positive for S. typhi, while in the control group only one (7%) was positive for S. typhi. Overall, 36 (64.3%) patients had malaria parasites. Patients with a higher O antibody titre (≥ 1 in 80) by Widal test were found to have consumed both tap water and pure water. More females (10/14; mean age: 33) had typhoid fever as a result of S. typhi infection, the majority of which were isolated from stool samples (57%). Nine of the isolates were also positive for malaria parasites, seven of which were in the trophozoite stage. Plasmodium falciparum was the predominant parasite (78%), the remainder being P. malariae. The majority of patients (12/14) with typhoid fever had normal PCV values. In conclusion, it is recommended that tests for the diagnosis of typhoid fever in Nigeria should include malaria parasites, S. typhi culture from faecal samples, and the Widal test.