During a 2-year period, blood samples from 2505 Lebanese blood donors were chosen at random, at various periods of time at one blood donation centre (Hotel Dieu de France, Beirut, Lebanon) and were screened for markers of HBV infection (HBsAg, anti-HBc and anti-HBs). The study showed HBsAg positivity of 0.6% and an overall exposure rate to HBV of 10.0%. Out of the 2505 blood donors screened, 56 (22%) were found to be 'anti-HBc alone' positive which is almost four times the HBsAg positivity. The 56 'anti-HBc alone' samples were retested by another ELISA kit commercially available and 54 samples were 'anti-HBc alone' positive by both assays. The 54 samples had no serological markers as evidence of infection with human immunodeficiency virus (HIV) or hepatitis C virus (HCV). Only seven (13%) out of the 54 samples were HBV DNA positive by PCR and all were HBV genotype D. All seven HBV DNA-positive samples had HBV DNA levels below 400 copies/ml. Although any circulating HBV DNA among our 'anti-HBc alone' blood donors was below the detection limit of our Amplicor Monitor assay, some of these samples had circulating virus. A national study, where a larger number of blood donors from different blood donation centres across the country will perhaps determine whether screening for anti-HBc in addition to HBsAg detection is needed in Lebanese blood donors.

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Recently we identified hepatitis C virus (HCV) genotype 4 as the principle genotype among Lebanese thalassaemics. In an attempt to confirm the predominance of genotype 4 in Lebanon and perhaps in the Middle East, genotyping was attempted on 142 HCV-infected Lebanese patients from five different hospitals in the country. These included 38 HCV-positive patients with symptomatic liver disease who were referred to gastroenterologists and 104 HCV-positive patients with no symptoms of liver disease: 27 patients with thalassaemia, 30 patients on haemodialysis, 32 multi-transfused and 15 intravenous drug users. HCV genotyping was performed on PCR HCV RNA-positive samples using a commercial line probe assay (LiPA; Innogenetics, Ghent, Belgium). HCV genotype 4 is found to be the predominant genotype among HCV-infected Lebanese patients (ranging from 34.2% to 53.3%) followed by 1a (ranging from 12.5% to 43.3%) and 1b (ranging from 8.0% to 34.4%). In patients with symptomatic liver disease, however, genotype 4 (34.2%) was preceded by genotype 1a (39.5%). The predominance of HCV genotype 4 in our population (45.7%) confirms the predominance of HCV genotype 4 in Lebanon and most of the Arab countries in the Middle East but contrasts with data reported from non-Arab Middle Eastern Countries as can be seen from the literature review. Implications of genotyping for clinical outcome of HCV infection, response to treatment as well as for vaccine development are discussed.

Recently the prevalence of hepatitis B virus (HBV) genotypes and the association between these genotypes and the clinical status of HBV-infected patients were recently investigated in the Lebanese population. The aim of the additional study reported here was to determine the current prevalence of hepatitis delta virus (HDV) infection and the range of HDV genotypes in this Lebanese population. Two hundred and fifty-eight HBsAg-positive patients (107 asymptomatic blood donors, 92 with chronic hepatitis, 24 with cirrhosis, 15 with hepatocellular carcinoma, 20 patients on haemodialysis) from ten medical centers in Lebanon were tested for antibody to hepatitis D virus (anti-HDV). Those testing positive were analysed further for HDV-RNA and for genotyping by reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP). Three samples (1.2%) were anti-HDV positive and out of these, only one was HDV-RNA positive (0.6%) and was analysed as HDV genotype I. Our results point to a low endemicity of HDV in the Lebanese population which is in sharp contrast to data reported from Lebanon 20 years ago and to the situation in neighbouring Arab and non-Arab countries in the Mediterranean region. HDV genotype I seems to be the predominant genotype in Lebanon and the Middle East.

Occult hepatitis B virus (HBV) infection, characterised by the presence of HBV infection with undetectable hepatitis B surface antigen (HBsAg), was investigated in 98 Lebanese patients with chronic hepatitis C liver disease and 85 control subjects recruited from eight institutions in different parts of the country. The prevalence of occult HBV infection ranged from 11.9% to 44.4% in hepatitis C virus (HCV)-infected patients and it increased with increasing severity of the liver disease. The overall rate of HBV DNA in our 98 HCV-infected patients was 16.3%. On the other hand, the rate of HBV DNA was 41.0% in anti-HBc alone positive patients compared to only 7.1% in healthy controls who were also anti-HBc alone positive (p < 0.001). Moreover, the prevalence HBV DNA increased with increasing severity of the liver disease, but this increase was only marginally significant and, perhaps, could have been significant if more patients were involved in the study. Although Lebanon is an area of low endemicity for both HBV and HCV, occult HBV infection is common in HCV-infected patients. The presence of HBV DNA, therefore, presents a challenge for the effective laboratory diagnosis of hepatitis B, particularly if polymerase chain reaction (PCR)-based HBV detection methods are not used.

Polymerase chain reaction (PCR)-based detection and transcription of the gene encoding a potent virulence factor, the exotoxin A, were done on 32 isolates of Pseudomonas aeruginosa belonging to 23 genotypes. These isolates were obtained from 22 patients who were admitted to the emergency room in a medical center during a 5-month period with the diagnosis of either unilateral or bilateral otitis externa. Patients showed symptoms that ranged from mild to severe. PCR amplification of a 396-bp fragment of the gene encoding the exotoxin A was done on extracted DNA. Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) was performed on extracted RNA to detect exotoxin A gene mRNA transcripts. Quantitation of RT-PCR amplicons from P. aeruginosa isolates associated with mild and severe symptoms was determined by end-point titration of c-DNA and scanning of amplicons with the Storm Gel and Blot Imaging System. Data have shown that all of the 32 isolates of P. aeruginosa carry the exotoxin A gene, and all isolates with the exception of two had the exotoxin A transcription demonstrated by the production of a 396-bp amplicon from RT-PCR-amplified RNA. The remaining two isolates amplified fragments that were slightly smaller than the expected size. Additional studies are needed to characterize these two mRNA transcripts. Transcription levels of exotoxin A gene associated with severe symptoms were significantly more elevated than those associated with mild to moderate symptoms. Studies are under way to determine expression of P. aeruginosa exotoxin A by detecting quantitatively levels of the translated exotoxin A protein produced by isolates associated with severe and mild to moderate symptoms.

The presence of hepatitis B virus (HBV) serological markers have been investigated in 101 Lebanese patients (69 men, 32 women; mean age 32.7 +/- 1.7 years) infected with human immunodeficiency virus type 1 (HIV-1). Seven patients (6.9%) were HBsAg carriers compared with 54 patients (53.5%) who had no evidence of exposure to HBV infection. Twenty-four patients (23.8%) had anti-HBc alone as a serological marker compared with four patients who were positive for anti-HBs alone and 12 patients (11.9%) who were anti-HBc and anti-HBs-positive. Occult HBV infection (presence of HBV DNA in the absence of HBsAg) is found to be relatively high (28.7%) in HIV-infected Lebanese patients and the overwhelming majority (83.3%) of those who were positive for anti-HBc alone had a detectable HBV DNA in their serum. However, none of our HIV-positive patients with occult HBV infection had abnormal alanine aminotransferase level, which also raises the question as to whether occult HBV plays a role in the aetiology of liver disease in HIV-infected patients. Further, studies on the association between HBV DNA levels and markers of liver function in addition to data on liver biopsy would help in answering this question.

Random amplified polymorphic DNA (RAPD) analysis was done on 32 isolates of Pseudomonas aeruginosa. These isolates were obtained from 22 patients who presented to the emergency room in a major medical center in Beirut, Lebanon, during a 5-month period with the diagnosis of either unilateral or bilateral otitis externa. Patients had yellowish to greenish discharge, moderate to severe external auditory canal swelling, moderate to severe pain, and periauricular cellulitis. None of these patients had intrinsic predisposing factors. An ear swab was obtained from both ears of patients, cultured on trypticase soy agar. P. aeruginosa was identified on the basis of pyocyanine production and API identification kits. RAPD analysis was done by using two primers (10 mer and 21 mer primers) and appropriate PCR conditions on extracted DNA. Our data have shown 23 RAPD patterns (A-W) distributed among the 32 P. aeruginosa isolates. RAPD patterns were reproducible. Twenty of 32 isolates were recovered from 10 patients with bilateral otitis externa. The remaining 12 of 32 isolates were recovered from 12 different patients with unilateral otitis externa. Eleven RAPD patterns (A,B,C,D,E,F,H,I,R,U,V) were associated with severe clinical symptoms, including severe pain, severe external auditory canal swelling, periauricular cellulitis, and a yellowish discharge. The remaining RAPD patterns were not associated with severe infections. This denotes a possible association between certain genotypes and severity of symptoms.