Latitude of the study place and age of the patient are associated with incidence of mediastinitis and microbiology in open-heart surgery: a systematic review and meta-analysis.

OBJECTIVE: We aimed to summarize the pooled frequency of mediastinitis following open-heart surgery caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria. DESIGN: This study was a systematic review and a meta-analysis of prospective and retrospective cohort studies. MATERIALS AND METHODS: We searched the literature, and a total of 97 cohort studies were identified. Random-effect model was used to synthesize the results. Heterogeneity between studies was examined by subgroup and meta-regression analyses, considering study and patient-level variables. Small-study effect was evaluated. RESULTS: Substantial heterogeneity was present. The estimated incidence of mediastinitis evaluated from 97 studies was 1.58% (95% confidence intervals [CI] 1.42, 1.75) and that of Gram-positive bacteria, Gram-negative bacteria, and MRSA bacteria evaluated from 63 studies was 0.90% (95% CI 0.81, 1.21), 0.24% (95% CI 0.18, 0.32), and 0.08% (95% CI 0.05, 0.12), respectively. A meta-regression pinpointed negative association between the frequency of mediastinitis and latitude of study place and positive association between the frequency of mediastinitis and the age of the patient at operation. Multivariate meta-regression showed that prospective cohort design and age of the patients and latitude of study place together or in combination accounted for 17% of heterogeneity for end point frequency of mediastinitis, 16.3% for Gram-positive bacteria, 14.7% for Gram-negative bacteria, and 23.3% for MRSA bacteria. CONCLUSION: Evidence from this study suggests the importance of latitude of study place and advanced age as risk factors of mediastinitis. Latitude is a marker of thermally regulated bacterial virulence and other local surgical practice. There is concern of increasing risk of mediastinitis and of MRSA in elderly patients undergoing sternotomy.

Some inflammation-related parameters in patients following normo- and hypothermic cardio-pulmonary bypass.

AIMS: One of the complications of Cardio-Pulmonary Bypass is the Systemic Inflammatory Response Syndrome. Cardio-Pulmonary Bypass can be performed under either normothermic or hypothermic conditions. The aim of this study was to compare some inflammation-related parameters of patients following normothermic and hypothermic bypass. Moreover, attempts were undertaken to detect endotoxin, an inflammatory agent that has been implicated in the Systemic Inflammatory Response Syndrome, in the serum of patients. Levels of serum anti-endotoxin antibodies were estimated since they have been reported to negate the effect of endotoxin in the inflammatory syndrome. METHODS AND RESULTS: Seventeen normothermic and 20 hypothermic cases were studied. Blood specimens were collected pre-, off- and post-bypass. Pertinent clinical and surgical data were collected. Hematological parameters (leukocyte, neutrophil and platelet counts) and liver function tests were determined by standard procedures. Endotoxin was determined by the Limulus Lysate Assay and anti-endotoxin antibodies by an enzyme immunoassay. Complement (C3 and C4) levels were determined by radial immunodiffusion. There were increases in leukocyte and neutrophil, and a decline in platelet numbers in both groups of patients. There was a decline in C3 and C4 levels in both groups of patients. Endotoxin was not detected in sera, and anti-endotoxin antibody levels were similar, in both groups of patients. CONCLUSION: There were no significant differences in most of the altered inflammation-related parameters between the two groups of patients. Some of the findings might be partly due to hemo-dilution. The hydrophobic nature of endotoxin among other factors, might have hindered its detection in serum.

Plasmid DNA vaccines.

Genes that code for the production of protein antigens have been cloned and recombined with plasmids. Gene-plasmid constructs have been amplified in a bacterial host, purified and administered to a mammalian host. The gene is expressed in the host and the antigen that is produced induces an immune response. These so-called DNA vaccines have been prepared for a number of infectious agents, some tumors and some allergens, and were shown to be efficacious in animal studies. Clinical trials for some of these vaccines are underway. Advantages of using a DNA vaccine include the abilities to favor a T helper-1 or a T helper-2 lymphocyte response and to induce a cytotoxic T-lymphocyte response. Moreover, some reports have indicated that they produce long-lasting immunity. DNA vaccines might be used in situations where no effective vaccine is available for a disease. However, their use might not be risk-free. Further research in this field is needed to determine their efficacy and to identify the risks involved in using them.

Immunization of mice against Salmonella typhimurium using different DNA preparations.

Groups of female BALB/c mice were given primary and booster injections of whole genomic DNA extracted from S. typhimurium, P. aeruginosa, or S. aureus. Other groups of mice were immunized in a similar manner with the 1.57kb fragment of the mouse virulence gene (mviA), pTargeT vector (plasmid DNA)/1.57kb construct, pTargeT vector, or saline. Mice in all groups were challenged intraperitoneally with 100 LD50 of S. typhimurium. The bacterial genomic DNA was extracted using the Pure Gene extraction kit. Specific primers were used to amplify the 1.57kb fragment by PCR. The pTargeT Mammalian Expression Vector System was used to prepare the plasmid/ 1.57kb construct. Bacterial genomic DNA extracted from P. aeruginosa and S. aureus appeared to induce non-specific resistance in mice. Specific, in addition to non-specific resistance appeared to be induced when genomic DNA from S. typhimurium was used. There was a prolongation of survival in the groups of mice that received either the 1.57kb fragment or the pTargeT vector/1.57kb construct and 16.67% and 33.34% respectively, of mice in each group survived at 40 days post challenge. None of the mice in the saline control group survived by day 7 post challenge. It is suggested that the non-specific resistance observed in this study might have been due to the adjuvant effect of the non-methylated CpG and other immunostimulatory motifs in bacterial DNA. Specific resistance obtained when genomic DNA from S. typhimurium was used might have been due to minute antigenic contamination, or virulence factor genes other than the mviA gene, might have been expressed in the host, which induced specific immunity.

Introduction of HIV-2 and multiple HIV-1 subtypes to Lebanon.

HIV genetic variability, phylogenetic relationships, and transmission dynamics were analyzed in 26 HIV-infected patients from Lebanon. Twenty-five specimens were identified as HIV-1 and one as HIV-2 subtype B. The 25 strains were classified into six env-C2-V3 HIV-1 subtypes: B (n = 10), A (n = 11), C (n = 1), D (n = 1), G (n = 1), and unclassifiable. Potential recombinants combining parts of viral regions from different subtypes Aenv/Dpol/Agag, Genv/Apol, and the unclassifiable-subtype(env)/unclassifiable-subtype(pol)/Agag were found in three patients. Epidemiologic analysis of travel histories and behavioral risks indicated that HIV-1 and HIV-2 subtypes reflected HIV strains prevalent in countries visited by patients or their sex partners. Spread of complex HIV-subtype distribution patterns to regions where HIV is not endemic may be more common than previously thought. Blood screening for both HIV-1 and HIV-2 in Lebanon is recommended to protect the blood supply. HIV subtype data provide information for vaccine development.

Identification of allergens in a selected group of asthmatics in Lebanon.

Anti-allergen antibodies were searched for by an Enzyme Immunoassay in the sera obtained from 60 patients with a clinical diagnosis of asthma. Allergic rhinitis was also present in 28 patients. The diagnosis of asthma was based on clinical criteria that include history and clinical evidence of airflow obstruction. Ten potential allergens (Bermuda grass, Olive tree, Parietaria, Alternaria, Cat hair dander, Dog hair dander, Mite DPT, Mugwort, Birch tree and Timothy grass) common to the Mediterranean area, were utilized. Twenty-five of 60 specimens were seropositive. Mite DPT was the allergen identified in 16 of the 25 seropositive specimens. Six of the 25 seropositive specimens reacted with more than one allergen. This may be due to the existence of similar antigenic determinant groups in the allergens used. There was no correlation between the occurrence of rhinitis in addition to asthma on one hand and the identified allergen on the other. Sixteen of the 25 seropositive patients were female. This observation is believed to be related to their occupation. Dog hair dander was identified as the allergen in 1 of the 25 seropositive patients. The low figure obtained was expected because keeping house pets is not a common practice in Lebanon. The 35 seronegative patients may belong to the intrinsic asthma group or the causative allergen in each case was not one of the 10 allergens used in this study. These results indicate that the house dust mite appears to be the most common allergen in the Lebanese asthmatic group studied.

Effects of various analgesic and anti-inflammatory drugs on endotoxin-induced hyperalgesia in rats and mice.

A new model of endotoxin (ET)-induced hyperalgesia has been used to test the effects of four classes of drugs in rats and mice. Hyperalgesia was assessed by paw pressure (PP), hot plate (HP) and tail flick (TF) tests. Each drug was injected intraperitoneally 24 and 12 h before ET injection and just before each pain test at 3, 6, 9 and 24 h after ET injection. At the dosages used, acetaminophen and dexamethasone were the most effective in reducing PP hyperalgesia and least effective on TF hyperalgesia, while indometacin and morphine produced their main effect on TF hyperalgesia. The four drugs were about equally effective in reversing HP hyperalgesia. We conclude that ET hyperalgesia is mediated by both prostaglandin-sensitive and prostaglandin-independent mechanisms.

Human leukocyte antigen frequencies in a selected group of Lebanese Greek Orthodox.

HLA classes I and II profiles were determined among 45 unrelated Lebanese Greek Orthodox by the complement dependent lymphomicrocytotoxicity assay. HLA epitope frequencies and alleles in linkage disequilibrium were determined; the obtained results were then compared to those reported for other groups. Moreover, possible HLA-disease associations were examined; medical history in relation to diabetes, rheumatoid arthritis, and ankylosing spondilitis was taken for each of the 45 individuals. The results indicated that: 1) There were similarities and differences in HLA frequencies and alleles in linkage disequilibrium in Greek Orthodox as compared to those in other groups. It is worth mentioning the higher frequencies of B35, DR11, and DQ3 and the existence of linkage disequilibrium between DR11 and DR52 and DR4 and DR53 in Greek Orthodox. 2) Preliminary results indicate that there were no significant HLA-disease associations between each of DR4 and rheumatoid arthritis, DR4 and insulin dependent diabetes mellitus (IDDM), and B27 and ankylosing spondilitis in the group studied. Such associations have been reported in North American Caucasians.

Antigen processing/presenting and oncogenesis.

It has been established in recent years that a number of tumor cell types express tumor antigens, yet the host's immune system fails to recognize them. The antigen processing/presenting machinery, which plays a crucial role in generating an immune response, and possible causes for its inability of processing/presenting tumor antigens are reviewed. These causes are related to the expression of major histocompatibility complex molecules, costimulatory molecules, and tumor antigens by tumor cells, and the types of cytokines produced. Therapeutic measures include transfecting tumor cells with genes that encode major histocompatibility complex and costimulatory molecules, cytokines, and tumor antigens. In addition, tumor peptide vaccines are evaluated. However, developing an immune response to tumor antigens carries with it the risk of autoimmune disease.

Detection of anti-hepatitis C-virus antibodies and hepatitis C-virus RNA in Lebanese hemodialysis patients.

Hemodialysis patients are at high risk of developing HCV infection. Reports from various countries have shown a prevalence of 12-29% among this group. The present study aimed at assessing the utility of HCV antibodies and HCV-RNA detection in the diagnosis of HCV in Lebanese hemodialysis patients. One hundred and eight hemodialysis patients from various hospitals in Lebanon were assayed for the presence of anti-HCV antibodies by ELISA and LIA, and for the presence of HCV-RNA by RT-PCR of the 5' Non-coding region (5' NCR). Specificity of the amplicons was confirmed by Southern hybridization. Seventeen out of 108 patients were reactive in ELISA and positive in the Line Immunoassay (LIA). Eleven out of the 17 were positive by RT-PCR. Three out of 29 patients nonreactive in ELISA were positive by RT-PCR. Our results indicate that hemodialysis patients in this study may be grouped into 4 categories. These include (1) patients with viremia and no immune response, (2) patients with no viremia and with an immune response, (3) patients with both viremia and immune response and (4) patients with no viremia and no immune response. The first 3 categories may reflect the different phases of HCV infection and imply that detection of both anti-HCV antibodies and HCV-RNA are needed for the establishment of adequate diagnosis. In addition, data collected from patients implicated in this study show that infection by HCV may be dialysis machine-related, rather than transfusion-related. However, cross-contamination unrelated to machines may also occurs.

Genotyping of hepatitis C virus isolates from Lebanese hemodialysis patients by reverse transcription-PCR and restriction fragment length polymorphism analysis of 5' noncoding region.

We have genotyped the 5' noncoding region of hepatitis C virus in Lebanese hemodialysis patients by reverse transcription-PCR and restriction fragment length polymorphism analysis. Of 50 patients, 15 had the expected 268-bp amplicon by reverse transcription-PCR. Specificity of the amplicons was confirmed by Southern hybridization. Restriction analysis of the amplicons showed the pattern for genotype 4 (common in the Middle East).

Endotoxin-induced local inflammation and hyperalgesia in rats and mice: a new model for inflammatory pain.

Lipopolysaccharide, also known as endotoxin (ET), is a major constituent of the outer membrane of the cell wall of most gram negative bacteria. ET is known to cause a number of pathophysiological changes associated with illness including inflammatory pain. The aim of this study is to characterize the peripheral hyperalgesia induced by ET in rats and mice. Different groups of rats and mice received different doses of ET ranging from 0.6 microgram to 40 micrograms dissolved in 50 microliters saline and injected in the plantar area of the left hind legs. All animals were subjected to tail immersion (TF), hot plate (HP) and paw pressure (PP) tests, 2-3 days prior to ET injection and during the following 1-2 days. ET injections produced a dose-dependent decrease in the latencies of the HP and PP tests of the injected leg reaching a maximum decrease of 50-60% of the control with 20-40 micrograms ET at 9 h (rats) and 24 h (mice) after the injection. Almost complete recovery was observed after 24 h in rats and 48 h in mice. TF latencies showed a less but a significant decrease while PP of the opposite leg and all tests in saline-injected animals did not elicit significant variations and served as additional controls. Our results indicate that the use of ET-produced hyperalgesia is a valid model for local and reversible inflammatory pain, with minimal distress to the animal. This model can also be used to study the efficacy of various anti-inflammatory and analgesic drugs and the molecular mechanisms of inflammation induced by bacterial invasion.

Rapid laboratory confirmation of human brucellosis by PCR analysis of a target sequence on the 31-kilodalton Brucella antigen DNA.

We developed a PCR-based assay for the rapid and specific laboratory diagnosis of human brucellosis directly from whole blood. Specimens were collected in EDTA tubes from 17 patients with acute serologic brucellosis and 3 patients with chronic relapsing brucellosis as determined by serologic tests and the patient's clinical picture. DNA was extracted from peripheral mononuclear cells obtained from the blood of patients with brucellosis and control individuals. Specific primers for the PCR amplification of a 223-bp region on the sequence encoding the 31-kDa immunogenic Brucella abortus protein (BCSP 31) were used. All amplicons had the expected size of 223 bp. The specificity of amplification was determined by Southern hybridization and restriction endonuclease analysis. DNA extracted from blood taken from 30 healthy individuals as well as from 9 patients with typhoid fever did not show any amplification with the primers used. The test proved to be rapid and specific for the laboratory confirmation of acute human brucellosis. Further studies must be conducted to assess the utility of this test on additional patients with chronic relapsing brucellosis as well as patients under treatment.

Two potential improvements to BCG and their effect on skin test reactivity in the Lebanon.

An account of an ongoing project to assess the possible benefits of two additives to BCG vaccine is presented. These additives are suspensions of irradiation killed Mycobacterium vaccae in one case, and M. leprae in the other. Groups of children aged 7-17 living in Zgharta and Akkar districts of North Lebanon have received vaccination with BCG alone or with either of the two additives since 1980. This region was chosen since contact with environmental mycobacteria is small, but both leprosy and tuberculosis occur there. So far the effects of the additives have been assessed by annual skin testing of volunteers with Tuberculin, Leprosin A, Vaccin and Scrofulin, and by measuring the size of the vaccine scars. Some children have now been followed up on four occasions, and special attention is paid to them. No complications have been encountered in the 1740 children who have entered the study (by our observation, or by local report on those who have not attended for follow-up) and the mean scar sizes after vaccines with the additives are no larger than those after BCG alone. There is no evidence that the additives have prevented development of Tuberculin positivity after vaccination, or have changed the nature of reaction to it. Incorporation of M. leprae significantly increased Leprosin A positivity and both additives increased Vaccin positivity in comparison with the effects of BCG alone. The results are fitted to a model of the theoretical expectations of the study and may be beginning to show the advantages expected of the additives. The only unexpected finding was a reduction in Scrofulin positivity especially associated with the additives. The very low contact with environmental mycobacteria experienced in the study area has allowed the pattern of post-vaccination decay of skin test positivity to be studied with greater precision than has been reported before, and differences have been detected between the two districts where the study was conducted. Confirmation of the possible advantage of the additives will rest with data to be obtained in longer term follow-ups and in studies being carried out in other countries.

Skin sensitization to mycobacteria amongst school children prior to a study of BCG vaccination in North Lebanon.

1888 school children aged between 7 and 17 years, living in 13 villages in two districts of North Lebanon, were skin tested with four new tuberculins as the initial step in a study of BCG vaccination. The great majority of children were tested with Tuberculin, Leprosin A, Vaccin and Scrofulin. In comparison with other countries where similar studies have been carried out, extremely low levels of sensitization were discovered, indicating very little contact with mycobacteria. There was, however, a statistically significant increase in positivity with increasing age. The results obtained for the villages of each district were significantly different from each other, positivity being greatest in Akkar district for each reagent. The eight villages of Zgharta district could be separated into a lowland group of four villages, a mountain group of three villages and one anomalous mountain village. There was significantly more positivity in the lowland than in the mountain villages. In Akkar district, where leprosy has a low prevalence, positivity to Leprosin A was 8% amongst the children (leaving out an anomalous village). In Zgharta district where the disease does not occur, positivity was 3.4% to Leprosin A for the lowland villages and 0.9% for the group of 3 mountain villages. The two anomalous villages were the only ones in which tuberculosis cases were known to have occurred recently, and they were the only two villages in which Tuberculin positivity exceeded 10%.

The bacterial flora of fruits and vegetables in Lebanon and the effect of washing on the bacterial content.

Washed and unwashed vegetables and fruit specimens including radish, lettuce, mint, carrots, parsley, strawberries, green almond, akadinya, green-gages, cherries, plums, peaches, pears, and apples were investigated for their bacterial content. Tested specimens had a high content of bacteria belonging to the genera Enterobacter, Citrobacter, Klebsiella, Proteus, Pseudomonas, Providencia, Escherichia, Staphylococcus, and Salmonella. The washing procedure followed was effective in reducing the number of bacteria, but did not eliminate them. Enterobacter agglomerans was present in most specimens tested, and 11 out of 28 E. coli isolates were serotypable and may be enterotoxigenic or enteropathogenic. These findings are of concern in view of the fact that food-borne illnesses including "Traveler's diarrhea" are common in Lebanon.