Characterization of influenza outbreaks in Lebanon during the 2013/14 and 2014/15 seasons

Despite the significant burden of influenza outbreaks, active disease monitoring has been largely absent in the Middle East, including Lebanon. In this study we characterized influenza virus in 440 nasopharyngeal swabs collected from patients with acute respiratory infections during two influenza seasons in Lebanon. Influenza A(H3N2) was dominant in the 2013/14 season while the A(H1N1)pdm09 and B/Yamagata strains were most prevalent in the 2014/15 season. All tested isolates were susceptible to 4 neuraminidase inhibitors (oseltamivir, zanamivir, peramivir and laninamivir). Genetic analysis of the haemagglutinin gene revealed multiple introductions of influenza viruses into Lebanon from different geographic sources during each season. Additionally, large data gaps were identified in the Middle East region, as indicated by the lack of current influenza sequences in the database from many countries in the region.

First detection and sequence analysis of thebla-CTX-M-15 gene in Lebanese isolates of extended-spectrum-β-lactamase-producingShigella sonnei

The emergence in Shigella species of extended-spectrum beta-lactamases (ESBL) that impart resistance to third-generation cephalosporins is a growing concern world-wide. So far, however, ESBL-producing Shigella have only been reported seven times, albeit from seven different countries. In Lebanon, three ESBL-producing clinical isolates of S. sonnei were recovered from 30 cases of shigellosis diagnosed between July 2004 and October 2005. All three were found to be resistant to amoxycillin, cefotaxime, ceftazidime, aztreonam, trimethoprim/sulphamethoxazole, gentamicin, and kanamycin. Each harboured the bla-CTX-M gene, and the results of sequence analysis indicated this to be of the bla-CTX-M-15 type and encoded on a 70-kb plasmid, flanked by an insertion element (ISEcp1). The bla-TEM-1 gene was also detected on the chromosomes of two of the ESBL-producing isolates. Class-2 integrons containing dhfr1, aadA1 and sat1 genes were detected on the chromosomes of all three isolates but not on the plasmids. Fluoroquinolone-modifying factors [QnrA, QnrB, QnrS or AAC(6')-Ib-cr] were not detected. The results of RAPD analysis, combined with data on antimicrobial susceptibility, indicated that each isolate was unique. In conclusion, the emergence of ESBL-producing isolates of S. sonnei has been demonstrated for the first time in Lebanon. The resistance of these isolates to third-generation cephalosporins was mediated by the CTX-M-15 enzyme, which was plasmid-encoded.

Signal transduction and the regulation of apoptosis: roles of ceramide

Knowledge about the molecular regulators of apoptosis is rapidly expanding. Cell death signals emanating from death receptors or internal cell injury detectors launch a number of signaling pathways which converge on several key families of proteins including specialized proteases and endonucleases which play a critical role in the execution of the death order. In this review, we summarize recent discoveries relating to the signaling pathways involved, the death receptors, the caspase family of apoptotic proteases, Bcl-2 family members, the sphingolipid ceramide, and the tumor suppressor p53. In particular, we focus on the role played by ceramide as a coordinator of the stress response and as a candidate biostat in the detection of cell injury.

Cerebral mycotic aneurysm in a child with Down's syndrome: a unique association

Mycotic aneurysms are rare complications in patients with infective endocarditis, particularly in the pediatric population. We report a case of mycotic aneurysm of the middle cerebral artery complicating bacterial endocarditis in a child with Down's syndrome. The patient was successfully treated medically without the need for surgical intervention.

Ceramide generation by two distinct pathways in tumor necrosis factor alpha-induced cell death

Ceramide accumulation in the cell can occur from either hydrolysis of sphingomyelin or by de novo synthesis. In this study, we found that blocking de novo ceramide synthesis significantly inhibits ceramide accumulation and subsequent cell death in response to tumor necrosis factor alpha. When cells were pre-treated with glutathione, a proposed cellular regulator of neutral sphingomyelinase, inhibition of ceramide accumulation at early time points was achieved with attenuation of cell death. Inhibition of both pathways achieved near-complete inhibition of ceramide accumulation and cell death indicating that both pathways of ceramide generation are stimulated. This illustrates the complexity of ceramide generation in cytokine action.

IL-1 activates two phospholipid signaling pathways in intestinal epithelial cells

OBJECTIVE AND DESIGN

the aim of the study was to decipher the molecular signals involved in IL-I's action on intestinal epithelial cells (IEC).

MATERIALS AND METHODS

Mode-K cells, used as a model of IEC, were treated with IL-I, and PLA2 activity and PGE2, ceramide, and cyclooxygenase-2 (COX-2) levels were measured using enzyme-immuno-assay kit, EIA, thin-layer chromatography and western blotting assays respectively.

RESULTS

IL-I caused a concentration- and time-dependent increase in PLA2 activity (3-fold increase), in ceramide levels (peak increase = 10.5 +/- 0.9 pmol/nmol phosphate), and in COX-2 and PGE2 levels. PGE2 increase was biphasic with an early peak at 10 min (around 5 ng/mg protein) due to increased PLA2 activity. The later peak (13.1 +/- 1.9 ng/mg protein) at 4 h was due to COX-2 induction.

CONCLUSION

In conclusion, these findings demonstrate that IL-I regulates IEC function through two pathways, the PLA2 and the sphingomyelin pathways, both of which are capable of modulating the inflammatory process.

Aspergillus vertebral osteomyelitis in a child with a primary monocyte killing defect: response to GM-CSF therapy

We report the first case of vertebral aspergillosis in a child with a primary defect in monocyte killing, an extremely rare immunodeficiency The diagnosis of defective monocyte killing was made by an in vitro assay that showed normal killing of Staphylococcus aureus by the patient's neutrophils but impaired killing by his monocytes. Importantly, the extensive granulomatous infection that involved the vertebral column, posterior mediastinum, pleura, and lung was not responsive to aggressive treatment with a combination of liposomal amphotericin B. intralesional amphotericin B. itraconazole, and granulocyte transfusions. Dramatic clinical and radiological improvement was only seen after the addition of granulocyte macrophage-colony stimulating factor (GM-CSF) to his treatment regimen. The use of GM-CSF in the treatment of invasive aspergillosis in immunocompromised patients requires further evaluation.

Old and new targets of antibacterial therapy

Currently available antibiotics target bacterial cell wall synthesis, protein synthesis, or DNA replication. Antibiotics that are structurally unrelated sometimes have common targets. Mutations in these common targets frequently give rise to bacteria that are resistant to multiple antibiotics. The impact of these bacteria in clinical situations is increasing whereas development of effective antibiotics for their treatment is not keeping pace. This emerging crisis in clinical care has led to intense efforts in new antibiotic development. Both improvements in currently available classes of antibiotics as well as discovery of completely novel ones are being aggressively sought. In this review, the mechanisms of action of available antibiotics will be discussed with emphasis on newly developed drugs. Also, some of the potential new targets of antibiotic therapy in the future will be highlighted.

Paediatric infective endocarditis: 19-year experience at a tertiary care hospital in a developing country

A retrospective study was undertaken to study children who presented with infective endocarditis (IE) to a university teaching hospital in Beirut, Lebanon, between January 1977 and May 1995. Of 41 patients with IE (24F, 17M), 28 (68%) were diagnosed between 1977 and 1985. Patients' ages ranged from 3 to 18 y (mean age 11.3+/-2.8 y), and 13 patients were <10 y of age. Clinical presentations included: fever (in 88%), heart failure (in 39%), neurologic findings (in 20%) and embolic phenomena (in 22%). Nineteen patients (46%) had underlying congenital heart disease (CHD) with tetralogy of Fallot and pulmonary stenosis being the most common. Sixteen patients (39%) had underlying rheumatic heart disease (RHD). A total of 5 children (12%) with normal cardiac anatomy had IE. One had underlying acquired viral myocarditis with mitral insufficiency. Echocardiography showed vegetations in 60%. Blood cultures were positive in 31 patients (76%). IE occurred in three patients following cardiac surgery. In one patient it occurred within 2 mo of surgery and in the other two it occurred within 6 mo. Streptococcus viridans and Staphylococcus aureus were the two most commonly isolated bacteria. Overall mortality rate was 29% (not statistically significant between patients presenting between 1977-1985 and 1986-1995; p = 0.17). There was no statistically significant difference in mortality among the groups (five in the group with CHD, six with RHD and one with structurally normal heart). This study demonstrates that RHD is an important underlying cause of IE in children in our community. This finding is similar to those in other developing countries and different from those in developed countries. Distribution of pathogens and CHD in our study is comparable to some reports in the literature, except for the higher proportion of patients with underlying pulmonary stenosis. Bacterial endocarditis prophylaxis should be emphasized in patients with RHD or pulmonary stenosis.

Rheumatic fever in children: a 15-year experience in a developing country

Clinical data from 91 patients with rheumatic fever (RF), who were hospitalized at a tertiary hospital in Lebanon between 1980 and 1995, were reviewed retrospectively. Age on hospitalization was 11.1+/-2.9 years (mean +/- SD, range 3-17 years). Nineteen patients were <6 years of age. Manifestations included carditis (93%), arthritis (39%), Sydenham's chorea (2%), erythema marginatum (4%), subcutaneous nodules (1%), fever (62%), arthralgia (55%), and acute congestive heart failure (CHF) on initial presentation (44%). Pericardial effusion occurred in 11%. There was positive family history of RF in 14%. Mitral insufficiency and aortic insufficiency occurred in 67 and 35%, respectively. Both mitral and aortic valves were involved in 30% of cases. Tricuspid insufficiency developed in 3% and pulmonary insufficiency in 1%. Mitral stenosis developed in 19%. Twenty-eight patients underwent surgical intervention: mitral valve repair and commissurotomy in 9/91 (10%), mitral valve replacement in 18/91 (20%), and aortic valve replacement in 9/91 (10%). Overall mortality was 12%: 5 following surgical intervention (3 after mitral valve surgery and 2 after mitral and aortic valve surgery). All patients that died had CHF on initial presentation (p = 0.006). This study includes hospitalized patients with predominant rheumatic heart disease. Initial presentation with CHF is a risk factor for surgical intervention and mortality. A significant high surgical intervention rate is noted that is probably related to the nature of the selected group studied. This study emphasizes the significant morbidity and death in patients with RF and carditis.

Distinct sites of action of Bcl-2 and Bcl-xL in the ceramide pathway of apoptosis

We studied the inhibition of tumour necrosis factor alpha (TNFalpha)- and camptothecin-induced apoptosis by Bcl-2 and Bcl-xL as they relate to the ceramide pathway. Expression of either Bcl-2 or Bcl-xL provided significant protection from the apoptotic effects of TNFalpha or camptothecin. In contrast to Bcl-2, Bcl-xL overexpression did not protect cells from ceramide-induced apoptosis. On the other hand, Bcl-xL prevented the accumulation of endogenous ceramide in response to TNFalpha or camptothecin, whereas Bcl-2 showed little effect on ceramide formation. Moreover, Bcl-xL, but not Bcl-2, totally inhibited a caspase-8-like activity in cell lysates stimulated with TNFalpha. These results identify a different mechanism of action for Bcl-xL compared with Bcl-2 and they demonstrate that Bcl-xL targets a point upstream of ceramide generation, whereas Bcl-2 functions downstream of ceramide in the TNFalpha- and camptothecin-activated pathways of apoptosis.

p53-dependent ceramide response to genotoxic stress

Both p53 and ceramide have been implicated in the regulation of growth suppression. p53 has been proposed as the "guardian of the genome" and ceramide has been suggested as a "tumor suppressor lipid. " Both molecules appear to regulate cell cycle arrest, senescence, and apoptosis. In this study, we investigated the relationship between p53 and ceramide. We found that treatment of Molt-4 cells with low concentrations of actinomycin D or gamma-irradiation, which activate p53-dependent apoptosis, induces apoptosis only in cells expressing normal levels of p53. In these cells, p53 activation was followed by a dose- and time-dependent increase in endogenous ceramide levels which was not seen in cells lacking functional p53 and treated similarly. Similar results were seen in irradiated L929 cells whereby the p53-deficient clone was significantly more resistant to irradiation and exhibited no ceramide response. However, in p53-independent systems, such as growth suppression induced by TNF-alpha or serum deprivation, ceramide accumulated irrespective of the upregulation of p53, indicating that p53 regulates ceramide accumulation in only a subset of growth-suppressive pathways. Finally, ceramide did not increase p53 levels when used at growth-suppressive concentrations. Also, when cells lacking functional p53, either due to mutation or the expression of the E6 protein of human papilloma virus, were treated with exogenous ceramide, there was equal growth suppression, cell cycle arrest, and apoptosis as compared with cells expressing normal p53. These results indicate that p53 is unlikely to function "downstream" of ceramide. Instead, they suggest that, in situations where p53 performs a critical regulatory role, such as the response to genotoxic stress, it functions "upstream" of ceramide. These studies begin to define a relationship between these two pathways of growth inhibition.

Selective involvement of ceramide in cytokine-induced apoptosis. Ceramide inhibits phorbol ester activation of nuclear factor kappaB

Among its diverse biologic effects, the cytokine tumor necrosis factor alpha causes the rapid nuclear translocation of the transcription factor, nuclear factor kappaB (NF-kappaB). The p55 tumor necrosis factor (TNF) receptor shares with the related APO-1/Fas antigen the ability to initiate apoptosis. We investigated the role of the sphingolipid mediator ceramide in the cytokine-induced signaling mechanisms leading to NF-kappaB activation and cell death. Several lines of evidence presented here suggest that ceramide generated in response to TNFalpha or Fas activation is not involved in NF-kappaB activation. (i) Cell-permeable ceramides and exogenous sphingomyelinase failed to induce either nuclear translocation of NF-kappaB or degradation of its cytosolic inhibitor, I-kappaB, in Jurkat T cells. (ii) Ceramide treatment of cells inhibited phorbol ester-induced activation of NF-kappaB. (iii) TNFalpha potently activated NF-kappaB in a cell line deficient in acid sphingomyelinase. (iv) TNFalpha activated NF-kappaB within minutes without altering ceramide levels. (v) Treatment of Jurkat cells with cross-linking antibodies to APO-1/Fas induced large scale increases in ceramide and apoptosis without affecting NF-kappaB. (vi) Ceramide generation in response to Fas activation was inhibited by N-acetyltyrosinylvalinylalanylaspartyl chloromethyl ketone, a peptide inhibitor of interleukin-1beta-converting enzyme-like proteases, whereas TNFalpha-induced NF-kappaB activation was unaffected by the inhibitor. These results show that ceramide accumulation belongs selectively to the apoptotic pathway(s) induced by cytokines, and, if anything, ceramide may participate in negative feedback regulation of NF-kappaB.

Cytokine response modifier A (CrmA) inhibits ceramide formation in response to tumor necrosis factor (TNF)-alpha: CrmA and Bcl-2 target distinct components in the apoptotic pathway

Proteases are now firmly established as major regulators of the "execution" phase of apoptosis. Here, we examine the role of proteases and their relationship to ceramide, a proposed mediator of apoptosis, in the tumor necrosis factor-alpha (TNF-alpha)-induced pathway of cell death. Ceramide induced activation of prICE, the protease that cleaves the death substrate poly(ADP-ribose) polymerase. Bcl-2 inhibited ceramide-induced death, but not ceramide generation. In contrast, Cytokine response modifier A (CrmA), a potent inhibitor of Interleukin-1 beta converting enzyme and related proteases, inhibited ceramide generation and prevented TNF-alpha-induced death. Exogenous ceramide could overcome the CrmA block to cell death, but not the Bcl-2 block. CrmA, however, did not inhibit the activation of nuclear factor (NF)-kappa B by TNF-alpha, demonstrating that other signaling functions of TNF-alpha remain intact and that ceramide does not play a role in the activation of NF-kappa B. These studies support a distinct role for proteases in the signaling/activation phase of apoptosis acting upstream of ceramide formation.

Activation of a retinoblastoma-protein-dependent pathway by sphingosine

The retinoblastoma protein (Rb) is a tumour suppressor that is activated by dephosphorylation the function of which appears to be mediated, at least partly, through the inhibition of several transcription factors, such as E2F. We have recently described sphingosine, a sphingolipid-breakdown product, as a potent and specific inducer of Rb dephosphorylation resulting in inhibition of cell growth and a specific arrest in the G0/G1 phase of the cell cycle. Here we examine the role of Rb and its interaction with E2F in mediating the effects of sphingosine on cell growth. Sphingosine potently inhibited growth of lymphoblastic leukaemic cells, Molt-4, at submicromolar concentrations but showed a 10-fold reduced potency in inhibiting growth of retinoblastoma cells, WERI-Rb-1, which lack functional Rb. In addition, sphingosine's ability to inhibit growth of mink lung epithelial cells was significantly attenuated in cells overexpressing simian virus 40 large T antigen which binds Rb and related proteins. Sphingosine treatment of Molt-4 cells, but not WERI-Rb-1 cells, resulted in the loss of the specific E2F bands produced by the interaction of E2F and its specific DNA sequence element on gel-shift assays. The concentration (submicromolar) and kinetics (4 h) of sphingosine treatment were identical with those required to induce Rb dephosphorylation. In addition, at similar concentrations, sphingosine caused c-myc down-regulation in Molt-4 cells starting at 6 h after treatment. These results demonstrate that activation of Rb by sphingosine leads to sequestration of E2F by the active (hypophosphorylated) form of Rb with the resultant loss of its DNA-binding and genetranscribing abilities. A functional Rb is required to mediate the specific effects of sphingosine on growth arrest.

Retinoblastoma gene product as a downstream target for a ceramide-dependent pathway of growth arrest

Ceramide, a lipid mediator, has been most closely associated with antiproliferative activities. In this study, we examine the mechanism by which ceramide induces growth suppression and the role of the retinoblastoma gene product (Rb) in this process. Withdrawal of serum from the serum-dependent MOLT-4 cells resulted in significant dephosphorylation of Rb, correlating with the induction of G0/G1 cell cycle arrest. Serum withdrawal resulted in marked elevation in the levels of endogenous ceramide (3-fold at 24 h and 8-fold at 96 h) with little changes in the endogenous levels of sphingosine. The addition of exogenous C6-ceramide resulted in a concentration- and time-dependent dephosphorylation of Rb. Exogenous ceramide was active at levels comparable to endogenous levels achieved with serum withdrawal. Peak activity of exogenous ceramide (at 6 h) correlated with the uptake of C6-ceramide by MOLT-4 cells. Next, a number of studies were conducted to determine whether Rb plays a role in ceramide-induced growth suppression. (i) C6-Ceramide was poorly active in growth suppression of retinoblastoma cells that lack Rb. (ii) Mink lung epithelial cells in which Rb had been sequestered by overexpression of large tumor antigen were resistant to the action of ceramide compared to cells transfected with large tumor antigen mutated in the Rb-binding pocket. (iii) Overexpression of the EIA adenoviral protein, which binds and sequesters Rb, resulted in protection from growth suppression and cell cycle arrest induced by ceramide. Thus, these studies demonstrate that Rb is a downstream target for ceramide and may function in a growth suppressor pathway resulting in cell cycle arrest.

Tumor necrosis factor-alpha (TNF-alpha) signal transduction through ceramide. Dissociation of growth inhibitory effects of TNF-alpha from activation of nuclear factor-kappa B

Tumor necrosis factor-alpha (TNF-alpha) exerts pleiotropic biologic effects. Although TNF-alpha appears to activate a number of signal transduction pathways, the role of second messengers in mediating the different effects of TNF-alpha are not well defined. In this study, we investigated the role of ceramide as an intracellular mediator of TNF-alpha action. In Jurkat T cells, TNF-alpha caused early activation of the sphingomyelin cycle with peak hydrolysis of sphingomyelin observed at 30 min following addition of TNF-alpha. In this cell line, TNF-alpha caused potent activation of nuclear factor-kappa B (NF-kappa B) and exerted potent cytostatic/cytocidal activity. C2-ceramide mimicked the effects of TNF-alpha on cell growth in a dose-dependent manner, but C2-ceramide was unable to induce activation of NF-kappa B under multiple conditions investigated. C2-ceramide, however, enhanced activation of NF-kappa B in response to TNF-alpha with peak effects observed at a concentration of C2-ceramide of 5 microM. Thus, ceramide functions as a selective mediator of the cytostatic/cytotoxic effects of TNF-alpha and plays a positive feedback role in activation of NF-kappa B. TNF-alpha signaling, therefore, involves multiple second-messenger pathways that function independently or coordinately to transduce distinct functions of TNF-alpha.