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A Ibrahim

Publications and source records attributed to A Ibrahim.

At least 37 records · Page 2Linked to original sources
PubMed2000

Evaluation of PCR-based methods for discrimination of Francisella species and subspecies and development of a specific PCR that distinguishes the two major subspecies of Francisella tularensis.

Previous studies have demonstrated that the four subspecies of the human pathogen Francisella tularensis, despite showing marked variations in their virulence for mammals and originating from different regions in the Northern Hemisphere, display a very close phylogenetic relationship. This property has hampered the development of generally applicable typing methods. To overcome this problem, we evaluated the use of PCR for discrimination of the subspecies using various forms of long arbitrary primers or primers specific for repetitive extragenic palindromic sequences (REP) or enterobacterial repetitive intragenic consensus (ERIC) sequences. Patterns generated by use of REP, ERIC, or long arbitrary primers allowed differentiation at the species level and of the four subspecies of F. tularensis. With each of these three methods, similar or identical clustering of strains was found, and groups of strains of different geographical origins or differing in virulence showed distinct patterns. The discriminatory indices of the methods varied from 0.57 to 0.65; thus, the patterns were not sufficiently discriminatory to distinguish individual strains. The sequence of a fragment generated by amplification with an arbitrary primer was determined, and a region showing interstrain heterogeneity was identified. Specific primers were designed, and a PCR was developed that distinguished strains of F. tularensis subsp. holarctica from strains of other F. tularensis subspecies, including strains of the highly virulent F. tularensis subsp. tularensis. Notably, one European isolate showed the genetic pattern typical of the highly virulent F. tularensis subsp. tularensis, generally believed to exist only in North America. It is proposed that a combination of the specific PCR together with one method generating subspecies-specific patterns is suitable as a rapid and relatively simple strategy for discrimination of Francisella species and subspecies.

DNA Primers↗
PubMed2000

Report of the Australian National Polio Reference Laboratory. 1 July to 31 December 1999.

Since 1994, as part of the global eradication of poliomyelitis, the Australian National Polio Reference Laboratory (NPRL) at the Victorian Infectious Diseases Reference Laboratory (VIDRL) has been responsible for virological testing to confirm the absence of poliomyelitis in Australia. Samples from patients with acute flaccid paralysis are transported to VIDRL for viral culture. Polio and enteroviruses are referred for intratypic differentiation as wild or Sabin (vaccine) strains. A total of 23 faecal specimens from 17 patients were processed for enterovirus culture in the period 1 July to 31 December 1999. Since 1995, 1,078 enterovirus isolates from six states have been tested for the presence of wild poliovirus. To date, 562 strains were confirmed as Sabin vaccine-like, one non Sabin-like strain was identical with a laboratory control virus and the other strains were non-polio enteroviruses or other viruses. A World Health Organization (WHO) workshop in diagnostic polio polymerase chain reaction techniques was held at VIDRL in November 1999. The laboratory was reaccredited as a regional polio reference laboratory for the WHO Western Pacific region and a national laboratory for Australia, the Pacific Island countries and Brunei Darussalam. Planning is proceeding for the polio-free certification and containment of laboratory stocks of wild poliovirus infectious materials in Australia.

Australia↗
PubMed2000

Pathogenesis I: interactions of host cells and fungi.

The interactions of host cells and fungi during infection represent a complex interplay. Although T helper 1 (Th1)-mediated immunity is primarily responsible for acquired resistance to Paracoccidioides brasiliensis, studies have demonstrated that polymorphonuclear neutrophils play a critical role in providing an early resistance to this organism. One study has shown that the invasiveness of Candida albicans requires adherence, particularly to endothelial cells, which in turn are stimulated to express various cell-markers and pro-inflammatory cytokines as part of a proactive resistance to invasion. Somewhat in contrast to infection with C. albicans, it has been shown that the capsular glucuronoxylomannan of Cryptococcus neoformans causes the shedding of host-cell adherence molecules (L-selectins) needed for the migration of host-inflammatory cells to sites of infection and likely explains, in part, the reduced host inflammatory response to this organism. Resistance to aspergillosis is often associated with the immune status of the host. In one set of studies, it has been demonstrated that lymphocytes have little direct effect on the organism, but that antigen-presenting dendritic cells stimulate the production of Th1 cytokines, suggesting a positive role for the dendritic cell in host-response. Similarly, another study has shown that among the regulatory cytokine networks that Th2-associated cytokines (e.g., interleukin-10) likely play a detrimental role in the resistance of the host to Aspergillus fumigatus.

Animals↗
PubMed1999

Report of the Australian National Polio Reference Laboratory. 1 January 1999 to 30 June 1999. Towards WHO certification as wild poliovirus-free: laboratory surveillance in Australia.

Since 1994 the Australian National Polio Reference Laboratory at the Victorian Infectious Diseases Reference Laboratory has been responsible for virological confirmation of the eradication of poliomyelitis in Australia. The laboratory is also a World Health Organization Western Pacific regional polio reference laboratory and the national polio laboratory for the Pacific Island countries and for Brunei Darussalam. It is now over two years since the last case of poliomyelitis was detected in the Western Pacific region of the World Health Organization. The co-operation of staff in all laboratories where polioviruses are handled and where samples from acute flaccid paralysis (AFP) patients are submitted is required until Australia and the region can be declared wild poliovirus-free. The characterisation of all polioviruses isolated in Australia in this reporting period led to the apparent detection of a non Sabin vaccine-like poliovirus in an environmental sample. The virus was found to be identical to a laboratory control isolate by sequencing. The environmental virus is therefore characterised as a contaminant, not a wild isolate. The investigation is outlined in this article, as well as the results of investigation and characterisation of all referred polioviruses.

Acute Disease↗
PubMed1999

Report of the Australian National Polio Reference Laboratory. 1 January to 31 December 1998.

The Australian National Polio Reference Laboratory was established at the Victorian Infectious Diseases Reference Laboratory (VIDRL) in late 1994 to carry out virological confirmation of the eradication of poliomyelitis in Australia. The laboratory is responsible for transporting samples from all Australian patients with acute flaccid paralysis (AFP) to VIDRL for poliovirus culture, identification and intratypic differentiation. The laboratory also performs polio serology on selected serum samples from AFP patients when faecal samples are not available. In 1998, faecal specimens were received from 11 patients with AFP. Adenovirus type 2 was isolated from 1 patient and an untypable non-polio enterovirus from another. No viruses were isolated from the other 9 patients. Since 1995, over 820 isolates have been transported to VIDRL from laboratories in five Australian states for testing. Three hundred and seventy three (45%) were confirmed as Sabin vaccine-like polioviruses, 416 (51%) were non-polio enteroviruses and 24 (3%) yielded no virus or viruses other than enteroviruses. Eight polioviruses are still uncharacterised.

Adolescent↗
PubMed1999

Localized pneumocephalus caused by Clostridium perfringens meningitis.

Clostridium meningitis is a rare complication of elective surgery, but the presence of pneumocephalus on CT in the absence of penetrating injuries, should raise the possibility of anaerobic infections. We report a case of fatal Clostridium perfringens meningitis which occurred 4 months after a craniotomy for glioblastoma multiforme. The diagnosis was suspected based on the CT findings. The literature of this rare condition is reviewed.

Clostridium perfringens↗
PubMed1999

Pulse wave velocity as an index of arterial stiffness: a comparison between newly diagnosed (untreated) hypertensive and normotensive middle-aged Malay men and its relationship with fasting insulin.

BACKGROUND: Arterial stiffness, an aging process which is accelerated by hypertension, is emerging as a useful index of vascular health. There are evidences to suggest that hyperinsulinaemia may be an independent risk factor for coronary artery disease, besides its possible pathogenic role in essential hypertension. The main objectives of this study were to compare arterial stiffness between untreated hypertensives and normotensives and to investigate the relationship between fasting serum insulin and arterial stiffness. METHODS: A cross-sectional observational study was designed. Forty normotensive (median age 47 +/- 6 yrs.) and twenty untreated hypertensive Malay men (median age 50 +/- 7 yrs.) without clinical evidence of cardiovascular complications were selected. Pulse wave velocity measured using the automated Complior machine was used as an index of arterial stiffness. Other measurements obtained were blood pressure, body mass index, fasting insulin, cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, glucose and creatinine level. RESULTS: The blood pressure and pulse wave velocity (PWV) were significantly higher in the hypertensives compared to the normotensives (blood pressure 169/100 mm Hg +/- 14/7 vs. 120/80 mm Hg +/- 10/4, p < 0.001; PWV 11.69 m/s +/- 1.12 vs. 8.83 m/s +/- 1.35, p < 0.001). Other variables such as body mass index, fasting insulin, cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides and haematocrit were comparable among the two groups. Within each group, there was a significant positive correlation between pulse wave velocity and systolic blood pressure (r = 0.76, p < 0.001 in normotensives; r = 0.73, p < 0.001 in hypertensives) and mean arterial pressure (r = 0.74, p < 0.001 in normotensives; r = 0.73, p < 0.001 in hypertensives). No correlation was noted between pulse wave velocity and diastolic blood pressure, age, body mass index, fasting insulin level, cholesterol, HDL-cholesterol, LDL-cholesterol or triglyceride levels. CONCLUSION: Arterial stiffness as determined by PWV is increased in newly diagnosed untreated hypertensive subjects even before clinically evident cardiovascular disease. However, arterial stiffness is not correlated with the fasting insulin level in normotensives and newly diagnosed hypertensives.

Adult↗
PubMed1998

Cellulosome and noncellulosomal cellulases of Clostridium cellulovorans.

This paper reviews the properties of the cellulosome and noncellulosome cellulases produced by Clostridium cellulovorans, an anaerobic, mesophilic, spore-forming microorganism that produces copious amounts of cellulase. The three major subunits of the cellulosome, CbpA, exoglucanase S (ExgS), and P100, are described, as well as the properties of the functional domains of CbpA. The properties of two noncellulosomal endoglucanases, EngD and EngF, are compared. The functions of the cellulose-binding domain (CBD) of CbpA indicate its potential uses in biotechnology.

Amino Acid Sequence↗
PubMed1998

Detection of pathogenic Yersinia enterocolitica using a digoxigenin labelled probe targeting the yst gene.

A 145 base pair digoxigenin-d-UTP-labelled probe, specific for pathogenic Yersinia enterocolitica heat-stable enterotoxin yst gene, was prepared by PCR. The probe was used in DNA-DNA colony hybridization and dot-blot hybridization assays. The specificity of the probe was confirmed using 52 strains representing all Yersinia spp., except Y. pestis. Out of a total of 25 Y. enterocolitica strains screened, the probe correctly identified all 18 pathogenic strains. Among the other Yersinia spp. screened, only one strain of Y. kristensenii was positively detected by the yst probe but could be differentiated by its weak signal response as compared with that obtained by pathogenic strains of Y. enterocolitica.

Bacterial Toxins↗
PubMed1998

[What functions do six different genes for secretory proteinases have in Candida albicans?].

Secreted Aspartate Proteinases (Sap) are among those factors of the human pathogen Candida albicans, which promote infections in the immunocompromised host. Sap isoenzymes are encoded by at least nine different genes (SAP1-9), which are differentially regulated in vitro. RT-PCR analysis during experimental infections and from patient samples confirmed the expression of SAP genes in vivo. However, while Sap2 is the dominant isoenzyme under culture conditions, other SAP genes are also expressed during infections. In order to investigate the role of single isoenzymes during the pathogenesis of candidosis, mutants were produced which harbour deletions in SAP1, SAP2, SAP3 and SAP4-6. Although only SAP2 and SAP4-6 mutants showed a strong reduction of proteolytic activity in vitro, all SAP mutants were significantly attenuated in systemic infections. In addition, SAP2, SAP3 and SAP4-6 mutants were clearly more sensitive to neutrophilic leucocytes compared to the wild type SC5314. These investigations show that several proteinase isoenzymes are likely to be involved in the pathogenesis of candidosis.

Candida albicans↗
PubMed1998

Invasion of the Nile Valley in Egypt by a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina, snail vectors of Schistosoma mansoni.

Two years (1996-1997) of systematic survey showed that a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina has invaded the irrigation and drainage systems in the Nile Delta and the Valley nor the of El-Menya. However, the infestation of water courses by and the population density of this snail were variable in various localities. The infestation rate ranged between 7.1% in El-Fayoum Governorate and 52.6% in El-Dakahliya Governorate and the snail density from 2 snails/site to 69.7 snails/site in the same governorates, respectively. Comparing the survey results of the two study years in the sampling sites indicated that the hybrid snail has relatively increased in population density than B. alexandrina. The hybrid snail of B. glabrata and B. alexandrina was found alone in some sites, but was mostly associated with B. alexandrina. The results showed also that both Biomphalaria have almost the same major physicochemical requirements. However, the hybrid snails and B. alexandrina were found differently associated with aquatic snails and plants. The hybrid snail was found naturally infected with S. mansoni thus giving indication that it is presently participating in schistosomiasis mansoni transmission in Egypt.

Animals↗
PubMed1998

Compatibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid of both to seven strains of Schistosoma mansoni from Egypt.

The susceptibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid snail of both, all obtained from natural habitats in Egypt, to infection with six human local strains of Schistosoma mansoni and a laboratory strain of human origin was determined. The infection rate, prepatent period, periodic cercarial production and duration of cercarial shedding were compared in all cases. The results showed that each of the three studied Biomphalaria snails had different rates of infection and different values of total periodic cercarial production with various strains of S. mansoni. However, the mean infection rate of all local S. mansoni strains was significantly much higher in B. alexandrina than each of B. glabrata and the hybrid snail, being 66%, 7.2% and 8.5%, respectively. Considering the mean of results of all local S. mansoni strains used, the longevity of cercariae-shedding B. glabrata and the hybrid snails was much longer than that of B. alexandrina, with high significant difference between them (P < 0.01), being 94.5, 103.3 & 69.1 days, respectively. The mean prepatent period of various S. mansoni strains showed no significant difference in the three Biomphalaria snails studied. The hybrid snail produced periodically (1 h stimulant twice weekly) more schistosome cercariae/snail (4,784.2) than B. glabrata (2,913.4 cercariae/snail) and the least production was in the case of B. alexandrina (1,397.2 cercariae/snail) (P < 0.05). The diurnal pattern of S. mansoni cercarial shedding was found to be similar for B. glabrata, B. alexandrina and the hybrid snail showing a peak of cercariae at the same time (9-10 a.m.).

Animals↗
PubMed1997

Detection of pathogenic Yersinia enterocolitica in milk and pork using a DIG-labelled probe targeted against the yst gene.

A PCR-amplified, digoxigenin (DIG)-labelled yst probe was evaluated in naturally and artificially contaminated pork and milk samples for its ability to detect and differentiate between pathogenic and nonpathogenic strains of Yersinia enterocolitica following enrichment in irgasan-ticarcillin-chlorate (ITC) enrichment broth. A total of 44 raw pork samples were obtained from one meat-processing factory and two local retail stores. Y. enterocolitica serogroup O:3/biovar 4 was isolated from 6 of the 44 (14%) pork samples tested. The hybridization results were in good agreement when compared with those from standard biochemical and serological tests. The lowest concentration detectable by a colony hybridization technique in the milk samples inoculated with Y. enterocolitica O:8 PA-A corresponded to 10 cfu/ml in the original sample. No pathogenic serovars were detected in 6 raw milk and 3 pasteurized milks tested. The results of this investigation demonstrate that the DIG-labelled yst probe is a reliable tool for rapid detection of pathogenic Y. enterocolitica in naturally and artificially contaminated food samples.

Animals↗
PubMed1997

A cluster of atypical Yersinia strains with a distinctive 16S rRNA signature.

Thirty-eight bacterial isolates from raw milk samples in Queensland, Australia were identified as members of the genus Yersinia on the basis of biochemical profile, ability to hybridize with a genus-specific DNA probe, comparative 16S rDNA sequence analysis, and the presence of characteristic 16S rDNA signature nucleotides which occur in all Yersinia spp. Twenty-five of these isolates reacted with typing sera (O:22 or O:58) of Y. enterocolitica; the remainder were non-typable. None of the isolates displayed any of the phenotypic or genetic virulence-associated characteristics of Y. enterocolitica. Comparative 16S rDNA sequence analysis revealed that members of this group appear to represent a new sub-line within the genus Yersinia, most closely related to Y. frederiksenii hybridization group 2 (unnamed genomospecies 2). This findings was confirmed by DNA hybridization studies which indicated that the strains belonged to the unnamed genomospecies, Yersinia frederiksenii genomospecies 2, which is biochemically indistinguishable from Y. frederiksenii (Y. frederiksenii genomospecies 1). A 23-nucleotide 16S rDNA signature stretch which characterised these strains was identified.

Animals↗
PubMed1997

PCR-amplified 16S and 23S rDNA restriction analysis for the identification of Acinetobacter strains at the DNA group level.

The genus Acinetobacter is phenotypically rather homogeneous, but genotypically heterogeneous. In this study, a simple method based on restriction analysis of a PCR-amplified large fragment (4.5 kb) of most of the ribosomal operon (16S and 23S ribosomal genes and the spacer in-between) was investigated. Sixty-seven collection strains belonging to the 20 DNA groups proposed until 1993 were studied. Using the enzyme Sau3AI, 25 DNA profiles were obtained. Strains belonging to DNA groups 1, 3, 6, TU13 and TU15 showed two profiles each, and DNA groups 4, 5 and 7 showed profiles with variants showing less intensive additional bands. The remaining 12 groups showed 12 different profiles. The profiles obtained were DNA-group-specific except for one profile which was shared between the unnamed DNA group 3 and a rarely encountered genotypically related DNA group. These two DNA groups could be separated by using the enzyme Hinf1. Twenty-five additional clinical isolates previously characterized by standard DNA-DNA hybridization were selected in a double-blind fashion for identification at the DNA group level to check the reliability of the assay. All strains were correctly identified at the DNA group level. PCR-amplified 16S and 23S rDNA restriction analysis is both an accurate and rapid method for the identification of Acinetobacter at the DNA group level.

Acinetobacter↗
PubMed1997

Specific detection of Coxiella burnetii through partial amplification of 23S rDNA.

A previously published sequence of the 23S rRNA gene of Coxiella burnetii has been reported to contain an intervening sequence of 444 base pairs (bp). The sequence information on the intervening sequence and the 23S rRNA gene was exploited to develop a specific PCR-based assay for C. burnetii. A primer set was designed that amplified a 477-bp fragment encompassing part of the intervening sequence and part of the 23S rDNA. From all of nine C. burnetii strains tested, a fragment of the expected size was amplified. As predicted from the published sequence, restriction endonuclease digestion of the PCR product from the Coxiella strains with RsaI produced two distinct fragments approximately 210- and 270-bp in size. The PCR-based method showed a detection limit of 10(2) bacteria as determined by visualization of the amplicon on an agarose gel. When experimentally infected blood was analyzed, the detection limit was 10(3) bacteria. No visible amplicons were observed when 41 bacterial strains, representing 29 species other than C. burnetii, were tested. The presence of the DNA in all bacterial samples was confirmed by amplification of a 350-bp fragment of the 16S rDNA using two universal primers. The described method proved to be specific for C. burnetii and may become a rapid and sensitive diagnostic assay for C. burnetii. The results also demonstrate that the intervening sequence within the 23S rRNA gene is generally found among isolates of C. burnetii.

Coxiella burnetii↗