Carbapenem-resistant and OXA-23-producing Acinetobacter baumannii isolates in the United Arab Emirates

Five carbapenem-resistant Acinetobacter baumannii isolates, collected from the United Arab Emirates in 2006, were investigated to identify the mechanism(s) responsible for carbapenem resistance. Genotyping was performed by pulsed-field gel electrophoresis, and the location of the bla _OXA-23 gene was determined by using the endonuclease I Ceu I technique and mating-out assays. The four isolates in which the bla _OXA-23 gene was located on the chromosome within a Tn 2006 composite transposon were clonally related. The single non-clonally related isolate harboured the bla _OXA-23 gene on a 70-kb transferable plasmid. This study reports on the dissemination of OXA-23-producing A. baumannii isolates in the Middle East.     

Clonal spread of carbapenem-resistant OXA-23-positive Acinetobacter baumannii in a Bulgarian university hospital

From October 1999 to September 2006, 29 carbapenem-resistant isolates of Acinetobacter baumannii were collected consecutively from patients hospitalized in different wards of the University Hospital in Pleven, Bulgaria. The bla _OXA-23 gene, associated with the upstream-located IS Aba1 , was identified as the mechanism responsible for carbapenem resistance in all isolates. The isolates belonged to two different clonal groups, indicating a sustained hospital outbreak. This study demonstrates both the epidemic potential of carbapenem-resistant A. baumannii and its longevity in the hospital environment.     

Epidemic multidrug-resistant Acinetobacter baumannii related to European clonal types I and II in Rome (Italy)

The molecular epidemiology and the genetic basis of antibiotic resistance in 88 multidrug-resistant (MDR) Acinetobacter baumannii strains isolated during 18 months from infected patients in seven intensive care units (ICUs) in Rome were investigated. Random amplified polymorphic DNA and macrorestriction analysis identified two predominant clonal types, genetically related to the European epidemic clones I (type 2) and II (type 1), accounting for 98.9% of A. baumannii ICU isolates. Type 1 was isolated from all ICUs under survey. Class 1 integrons of 2.2 and 2.5 kb were detected in type 1 and type 2 isolates, respectively. The integron structures were similar to those previously determined for epidemic A. baumannii strains from various European countries, and suggestive of integron rearrangement/exchange among isolates related to the European epidemic clones I and II. Carbapenem resistance was associated with the presence of the bla _OXA-58 gene in type 1 isolates. The results indicate that the A. baumannii type 1 clone has a high potential of spreading among hospitals.     

Molecular characterisation of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella spp. isolates at a tertiary-care centre in Lebanon

The prevalence of bla _CTX-M, bla _TEM and bla _SHV genes among extended-spectrum β-lactamase (ESBL)-producing clinical isolates of Escherichia coli ( n  = 50) and Klebsiella spp. ( n  = 50) from Lebanon was 96%, 57% and 67%, and 40%, 82% and 84%, respectively. Genotyping revealed that the clonal diversity was unrelated to the presence of bla genes. Sequence analysis of 16 selected isolates identified the bla _CTX-M-15, bla _TEM-1, bla _OXA-1 and six bla _SHV genes, as well as the gene encoding the quinolone-modifying enzyme AAC(6')-Ib-cr. The genes encoding CTX-M-15 and AAC(6')-Ib-cr were carried on a 90-kb plasmid of the pC15-1a or pCTX-15 type, which transferred both ESBL production and quinolone resistance from donors to transconjugants.     

Aquaporin-1 and HCO3−-Cl− transporter-mediated transport of CO2 across the human erythrocyte membrane

Recent studies have suggested that aquaporin-1 (AQP1) as well as the HCO₃⁻-Cl⁻ transporter may be involved in CO₂ transport across biological membranes, but the physiological importance of this route of gas transport remained unknown. We studied CO₂ transport in human red blood cell ghosts at physiological temperatures (37 °C). Replacement of inert with CO₂-containing gas above a stirred cell suspension caused an outside-to-inside directed CO₂ gradient and generated a rapid biphasic intracellular acidification. The gradient of the acidifying gas was kept small to favour high affinity entry of CO₂ passing the membrane. All rates of acidification except that of the approach to physicochemical equilibrium of the uncatalysed reaction were restricted to the intracellular environment. Inhibition of carbonic anhydrase (CA) demonstrated that CO₂-induced acidification required the catalytic activity of CA. Blockade of the function of either AQP1 (by HgCl₂ at 65 μM) or the HCO₃⁻-Cl⁻ transporter (by DIDS at 15 μM) completely prevented fast acidification. These data indicate that, at low chemical gradients for CO₂, nearly the entire CO₂ transport across the red cell membrane is mediated by AQP1 and the HCO₃⁻-Cl⁻ transporter. Therefore, these proteins may function as high affinity sites for CO₂ transport across the erythrocyte membrane.     

Immunohistochemical evaluation of nm23-H1 gene product in transitional cell carcinoma of the bladder

The expression of the nm23-H₁ gene has been suggested to have an inverse association with metastases in certain tumours. The aim of this study was to investigate the relationship of nm23-H₁ immunohistochemical expression with pathological tumour variables and survival in a series of transitional cell carcinomas (TCCs) of the bladder. Formalin-fixed, paraffin-embedded archival tissue from 87 carcinomas (T_a-T₁ 45 cases) and T₂-T₄ (42 cases) was immunostained (Strept ABC/ HRP) with the NDPK-A monoclonal antibody (NDPK-A) against nm23-H₁ protein. The tumours had already been evaluated for immuno-expression of p53 protein. In addition, DNA analysis was performed by flow cytometry. Results were analysed using the linear trend in proportions test, the Fisher's exact test and multivariate analysis. Paradoxically, advanced tumour stage showed significant correlation with nm23-H₁ immunopositivity in muscle invasive TCCs (P_t = 0.01). Patients with nm23-H₁ positive, muscle invasive TCCs had a worse prognosis at a level of suggestive statistical significance (P_F = 0.08). In multivariate analysis, using a Cox's proportional hazards survival model with six variables, tumour grade, disease stage and synchronous p53 and nm23-H₁ detection showed significant correlation with poor patient survival ( P  = 0.014, P  = 0.049 and P  = 0.05, respectively).     

Activation of Cloned Human CD4+ Th1 and Th2 Cells by Blood Dendritic Cells

Dendritic cells (DC) have been reported to be the most potent antigen-presenting cells (APC) for the activation of naive T cells and to be 10–100-fold more potent APC than monocytes (Mφ) in the mixed lymphocyte reaction. In this study the authors compared human blood DC with Mφ and B cells for their ability to activate cloned rye grass allergen Lol p I specific CD4⁺ Th₁ and Th₂ cells. In the presence of Lol  p I, all three types of APC activated Th₁ and Th₂ cells to a similar extent, as shown by T-cell proliferation and interferon-γ, interleukin-2 (IL-2) or IL-4 secretion. However, at low APC : T cell ratios, Mφ were the most potent APC for both Th₁ and Th₂ cells followed in decreasing order by DC and B cells. This hierarchy was observed with APC preparations isolated by negative selection or highly purified by positive selection using fluorescent cell sorting for HLA-DR^high-DC, CD14^pos-Mφ and CD19^pos-B cells. The data demonstrate that, in contrast to what has been reported for naive T cells, human blood DC activate cloned memory Th₁ and Th₂ cells to a similar extent as Mφ and B cells presumably because the requirements for activation of memory type T cells are less stringent than those for naive T cells.     

OXA-51-like β-lactamases and their association with particular epidemic lineages of Acinetobacter baumannii

Sixty diverse clinical Acinetobacter baumannii isolates of worldwide origin were assigned to sequence groups, based on a multiplex PCR for the ompA , csuE and bla _OXA-51-like genes. The majority (77%) of isolates belonged to sequence groups 1 and 2 (SG1 and SG2), with sequence group 3 (SG3) and non-grouped isolates accounting for the remainder. The isolates were not closely related according to pulsed-field gel electrophoresis (PFGE), and the majority were sensitive to imipenem and meropenem. The construction of a linkage map of OXA-51-like β-lactamase sequence relationships revealed two closely related clusters of enzymes, one focused around OXA-66 and the other around OXA-69. Isolates belonging to SG1 encoded an enzyme from the OXA-66 cluster, while those belonging to SG2 encoded an enzyme from the OXA-69 cluster. All SG3 isolates encoded OXA-71, which does not form part of a close enzyme grouping. Major multinational lineages accounted for a significant proportion of A. baumannii clinical isolates, and the evolution of the OXA-51-like enzymes appears to be an ongoing process.     

Allotype-Associated Differences in Concentrations of Human IgA2

Concentrations of immunoglobulin (Ig)A₂ were determined in 176 Finnish blood donor sera. Their IgA, IgM, IgE, IgG₁, IgG₂, IgG₃ and IgG₄ concentrations and Gm allotypes had been determined earlier. The mean concentration of IgA₂ was higher in individuals carrying the Gm(ax) allele (0.15 g/l) than in those negative for Gm(x) (0.103 g/l). The difference was statistically significant ( P  = 0.006). As ≥ 70% of IgA was usually IgA₁, its concentration could be calculated fairly reliably by subtracting the IgA₂ value from the IgA value. The mean IgA₁ concentration (2.03 g/l) seemed to be independent of the Gm allotypes.     

Cyclic AMP-dependent Cl− secretion induced by thromboxane A2 in isolated human colon

Increased release of thromboxane A₂ (TXA₂) has been shown to be involved in inflammatory bowel diseases. In the present study, we have investigated the effect of a stable TXA₂ analogue (STA₂) on the electrical parameters in isolated human colonic mucosa. In the human mucosa set between Ussing chambers, STA₂ stimulated Cl⁻ secretion in a concentration-dependent manner with an EC₅₀ of 0.06 μ m . The STA₂-induced Cl⁻ secretion was significantly inhibited by ONO-3708 (10 μ m ), a specific TXA₂ receptor antagonist. The effect of STA₂ (0.3 μ m ) was independent of the colonic segment from which the tissue was obtained, from caecum to rectum. Chromanol 293B, an inhibitor of the cAMP-dependent KvLQT1 channel, attenuated the STA₂-induced Cl⁻ secretion in the human colonic mucosa (IC₅₀ value 1.18 μ m ). We found that KvLQT1 mRNA and protein were expressed in all the tested segments of the human colon. The STA₂-induced Cl⁻ secretion was significantly inhibited by 8-bromo-2'-monobutyryladenosine-3',5'-cyclic monophosphorothioate (50 μ m ), a membrane-permeant cAMP antagonist. STA₂ (0.3 μ m ) significantly increased the intracellular cAMP levels and the short-circuit current via TXA₂ receptor in a human colonic cell line. These results suggest that the TXA₂-induced Cl⁻ secretion in the colon is mediated via the cAMP pathway in addition to the Ca²⁺–calmodulin pathway which was previously reported.     

Urinary leukotriene E4 and 11-dehydrothromboxane B2 in patients with aspirin-sensitive asthma

The objective of this study was to define the participation of cysteinyl leukotrienes (LTs) or thromboxane A₂ in the pathogenesis of aspirin-sensitive asthma (ASA). Leukotriene E₄ (LTE₄) and 11-dehydrothromboxane B₂ (11DTXB₂) values in spot urine were measured in 22 asthmatics with a history of aspirin sensitivity and in 17 without such a history of aspirin-sensitive asthma [NASA]) in the outpatient clinic. The urinary LTE₄ value was significantly higher in ASA patients than in NASA (340±47 vs 65±15 pg/mg·cr, P <0.001), but there was no significant difference in urinary 11DTXB2 between the two groups (891±77 vs 657±90 pg/mg·cr). A high value of LTE4 was not associated with type of asthma, severity of disease, oral prednisolone treatment, sex, or age. A higher value of 11DTXB₂ was observed in the atopic type than the nonatopic type in ASA (1086±111 vs 697±147 pg/mg·cr, P<0.05). No correlation was observed between urinary LTE₄ and 11DTXB₂ in either ASA or NASA. In conclusion, LTs may play an important role in the pathogenesis of ASA, and TXA₂ in the pathogenesis of the atopic type in ASA.     

Prevalence of OXA-type β-lactamases among Acinetobacter baumannii isolates from Northwest of Iran

Carbapenems have been considered as last line antibiotics for treatment of multidrug-resistant (MDR) Acinetobacter baumannii but carbapenem resistant A. baumannii has been increased during the last decade in many parts of the world. OXA-type β-lactamase enzymes are the most common cause of carbapenem resistance in A. baumannii and presence of ISAba1 in upstream of these genes may increase the expression of these OXA genes. The aim of this study was to determine, for the first time, the antibiotic resistance pattern and prevalence of OXA type β-lactamases among nosocomial A. baumannii isolates from northwest of Iran. A total of 100 A. baumannii isolates were recovered from hospitalized patients in a university hospital in northwest of Iran. Sixty-two percent of isolates were resistant to imipenem. All isolates carried bla(OXA-51)-like gene. Among imipenem resistant isolates, 88.7% carried bla(OXA-23)-like, 1.6% carried bla(OXA-40)-like, and 3.2% had bla(OXA-58)-like resistance genes. Ninety percent of isolates contained ISAba1 element and in 74.2% of imipenem resistant isolates, ISAba1 was located in upstream of bla(OXA-23)-like. The results of this study demonstrated high prevalence of OXA-type carbapenemase among MDR A. bumanii in the Northwest of Iran.     

D1 and D2 receptor-mediated dopaminergic modulation of visual responses in cat dorsal lateral geniculate nucleus

The modulatory effects of dopamine (DA) on the visual responses of relay cells of the dorsal aspect of cat lateral geniculate nucleus (dLGN) were tested using local micro-iontophoretic application of DA and application of the receptor-specific agonists SKF38393 (SKF, D₁/D₅) and quinpirole (QUIN, D₂/D₃/D₄) in the anaesthetized alcuronium-treated cat. The effects of DA and QUIN were clearly dose-dependent: small amounts caused a weak and transient facilitation of visual activity (10–30 % increase) preferentially in Y-type relay cells, which changed to a moderate reduction of visual responses when the dose was increased (50 %, maximal 70 %). The effect of SKF was mainly suppressive and increased with the amount of drug applied (up to 90 % reduction). The selective antagonists SCH23390 (SCH, D₁) and sulpiride (SULP, D₂) reduced the effects of co-applied DA agonists. We found little evidence for a specific dopaminergic modulation of the surround inhibition (stimulus-driven lateral inhibition) although DA slightly facilitated the transmission of weak signals (small stimuli). Nevertheless, some dopaminergic effects seem to be mediated via inhibitory interneurons regulating the strength of sustained or recurrent inhibition. Application of DA agonists during blockade of GABA_A receptors indicates a direct suppression of relay cells via D₁ receptors, an excitation of relay cells via D₂ receptors and - with increasing amounts of D₂ agonist - probably also an excitation of inhibitory interneurons, which results in an indirect inhibition of dLGN relay cells (predominantly of the X-type). The results are discussed in relation to the impairment of visual functions in Parkinson's disease.     

The blaSHV-5 gene is encoded in a compound transposon duplicated in tandem in Enterobacter cloacae

The presence of bla _SHV-5 is described in a compound transposon, duplicated in tandem and flanked by IS 26 copies on a 70-kb conjugative plasmid (pHNM1), in an Enterobacter cloacae strain associated with a nosocomial outbreak that occurred in Mexico.     

Anti-Parental-Strain Lymphocyte Responsiveness of F1 Hybrid-Strain Lymphocytes

The interactions between immunocompetent parental-strain tells and the F₁ hybrid rat into which these cells have been injected were studied. This involved examination of the behavior of both parental- and host-strain cells. Host lymphocytes reactive against parental-strain lymphocytes appeared in the thoracic duct lymph within 12 h of the intravenous injection of parental thoracic duct lymphocytes or thymus cells. The activity of these F₁ hybrid-strain lymphocytes was directed preferentially against parental-strain lymphocytes with anti-F₁ hybrid potential. This subpopulation of parental cells was absent from the thoracic duct but was well represented in the spleen, this enrichment being masked by a reversible F₁ hybrid anti-parental-strain lymphocyte response. If the anti-parental-strain lymphocyte activity of F₁ hybrid cells was interrupted by the destruction of host-strain cells with antiserum, parental-strain lymphocytes in the tissues of F₁ hybrid rats could be reactivated. By this procedure it was possible to passage graft-versus-host reactions initiated by parental-strain lymphocytes through several F₁ hybrid rats, thereby implying that anti-parental lymphocyte activity is of importance in limiting the serial passage of these reactions. Some of the anti-parental lymphocyte activity observed on the part of F₁ hybrid-strain cells was probably mediated by anti-idiotypic antibodies, but other phenomena, especially selective migration of both donor and host lymphocyte subpopulations, are of major importance in the interaction between parental-strain lymphocytes and an F₁ hybrid host.     

Recovery of FEV1 after histamine challenge in asthmatic children

Factors that influence the time necessary for complete recovery of FEV₁ after inhaling histamine were analysed in forty-five children with asthma. These included the initial bronchial obstruction (baseline FEV₁), the provocation dose of histamine producing a 20% fall in FEV₁ (PD₂₀) and the fall in FEV₁ after the histamine challenge. In addition it was also investigated whether a second challenge carried out after complete recovery of FEV₁ would produce a reproducible PD₂₀-histamine value. The time for complete recovery varied widely from 15 to more than 75 min. The time needed for complete recovery of FEV₁ after the histamine challenge seems to be mainly determined by the PD₂₀ value. The other factors such as initial bronchial obstruction and the fall in FEV₁ after the challenge showed no significant relationship with the recovery time. A second challenge with histamine resulted in a highly reproducible PD₂₀ value. The clinical implication of this study is that other tests can only be performed when FEV₁ has returned to 95% of baseline.     

Both Murine SAA1 and SAA2 Yield AA Amyloid in Alveolar Hydatid Cyst-Infected Mice

Amyloid susceptible C57BL/6 and partially amyloid resistant A/J mice, infected intraperitoneally with 250 alveolar hydatid cyst (AHC), the larval stage of a cestode parasite Echinococcus multilocularis , develop multiple organ amyloid deposits at approximately 1 and 4 weeks post infection (p.i.), respectively. Pooled spleens and livers from each mouse strain, at 8 and 10 weeks p.i., were used for the purification of protein AA utilizing a HiLoad Superdex 200 column equilibrated with 5 M guanidine-HCl. Protein AA from each mouse strain was separated on 16% Tris-tricine SDS-PAGE gels and immunoblotted with monospecific rabbit anti-mouse AA IgG; five and six immunoreactive AA subspecies were detected in the C57BL/6 and A/J materials, respectively. N-Terminal amino acid sequence analysis was performed on the bulk column-purified protein AA as well as on the electroblotted AA subspecies from each mouse strain. The results show a mixture of serum amyloid A₁ (SAA₁) and (SAA₂)-derived AA protein from each mouse strain; SAA₁-derived AA, although alluded to, has never been demonstrated as tissue deposits in mice. These findings suggest that the intense and persistent inflammatory processes in AHC-infected mice may have induced conversion of weakly amyloidogenic SAA₁ to AA. This conversion could be detected by amino acid sequencing of electrophoretically separated AA subspecies.     

GABAB receptor activation desensitizes postsynaptic GABAB and A1 adenosine responses in rat hippocampal neurones

Whole-cell recordings of EPSCs and G-protein-activated inwardly rectifying (GIRK) currents were made from cultured hippocampal neurones to determine the effect of long-term agonist treatment on the presynaptic and postsynaptic responses mediated by GABA_B receptors (GABA_BRs). GABA_BR-mediated presynaptic inhibition was unaffected by agonist (baclofen) treatment for up to 48 h, and was desensitized by about one-half after 96 h. In contrast, GABA_BR-mediated GIRK currents were desensitized by a similar amount after only 2 h of agonist treatment. In addition, presynaptic inhibition mediated by A₁ adenosine receptors (A₁Rs) was unaffected by prolonged GABA_BR activation, whereas A₁R-mediated GIRK currents were desensitized. Desensitization of postsynaptic GABA_BR and A₁R responses was blocked by the GABA_BR antagonist (1-(S)-3,4-dichlorophenylethyl)amino-2-(S) hydroxypropyl-p-benzyl-phosphonic acid (CGP 55845A), but not by the A₁R antagonist cyclopentyldipropylxanthine (DPCPX). GIRK current amplitude could be partially restored after baclofen treatment by either coapplication of baclofen and adenosine, or intracellular infusion of the non-hydrolysable GTP analog 5'-guanylylimidodiphosphate (Gpp(NH)p). Short-term (4-24 h) baclofen treatment also significantly desensitized the inhibition of postsynaptic voltage-gated calcium channels by activation of GABA_BRs or A₁Rs. These results show that responses mediated by GABA_BRs and A₁Rs desensitize differently in presynaptic and postsynaptic compartments, and demonstrate the heterologous desensitization of postsynaptic A1R responses.     

Serial Measurements of Pregnancy-specific β1-glycoprotein (β1SP1) in Patients with Trophoblastic Disease

A radioimmunoassay for pregnancy-specific-β₁-glycoprotein (Bohn. 1971) has been established with a limit of detection of 2 μMg/litre in serum. The assay has been used to measure serial levels of pregnancy-specific-β₁-glycoprotein (β₁SP₁) in the serum of patients with choriocarcinoma and teratoma for comparison with measurements of the β-subunit of human chorionic gonadotrophin. The value of the assay for β₁SP₁, in the management of these patients is discussed.     

Central CRF, urocortins and stress increase colonic transit via CRF1 receptors while activation of CRF2 receptors delays gastric transit in mice

Recently characterized selective agonists and developed antagonists for the corticotropin releasing factor (CRF) receptors are new tools to investigate stress-related functional changes. The influence of mammalian CRF and related peptides injected intracerebroventricularly ( i.c.v. ) on gastric and colonic motility, and the CRF receptor subtypes involved and their role in colonic response to stress were studied in conscious mice. The CRF₁/CRF₂ agonists rat urocortin 1 (rUcn 1) and rat/human CRF (r/h CRF), the preferential CRF₁ agonist ovine CRF (oCRF), and the CRF₂ agonist mouse (m) Ucn 2, injected i.c.v. inhibited gastric emptying and stimulated distal colonic motor function (bead transit and defecation) while oCRF_9–33OH (devoid of CRF receptor affinity) showed neither effects. mUcn 2 injected peripherally had no colonic effect. The selective CRF₂ antagonist astressin₂-B ( i.c.v. ), at a 20 : 1 antagonist: agonist ratio, blocked i.c.v. r/hCRF and rUcn 1 induced inhibition of gastric transit and reduced that of mUcn 2, while the CRF₁ antagonist NBI-35965 had no effect. By contrast, the colonic motor stimulation induced by i.c.v. r/hCRF and rUcn 1 and 1h restraint stress were antagonized only by NBI-35965 while stimulation induced by mUcn 2 was equally blocked by both antagonists. None of the CRF antagonists injected i.c.v. alone influenced gut transit. These data establish in mice that brain CRF₁ receptors mediate the stimulation of colonic transit induced by central CRF, urocortins (1 and 2) and restraint stress, while CRF₂ receptors mediate the inhibitory actions of these peptides on gastric transit.