Antibiotic resistance patterns of Acinetobacter calcoaceticus–A. baumannii complex species from Colombian hospitals

Introduction Only automated phenotypic methods are currently used in Colombian hospitals for identifying isolates of the Acinetobacter calcoaceticus-A. baumannii complex (ACB). The phenotypical similarities in these species mean that they cannot be differentiated by manual or automated methods, thereby leading to their identification as A. baumannii, or ACB complex in clinical settings. Our objective was to identify to the species level 60 isolates, from four hospitals, evaluate their antibiotic susceptibility, and detect resistance-related genes.Methods16S–23S rRNA internal transcribed spacer (ITS) region and rpoB gene partial sequences were amplified. Resistance genes for cephalosporin, carbapenem and aminoglycoside were detected by PCR. Possible mutations in the quinolone resistance-determining region (QRDR) were evaluated. The association of ISAba-1 with blaOXA and blaADC genes was determined by PCR. Amplification products of ITS region, rpoB gene and some resistance genes were sequenced and compared using the BLAST tool. Results: 16S-23S rRNA ITS region and partial rpoB gene sequence analysis allowed 51isolates to be identified as A. baumannii, 8 as A. nosocomialis, and 1 isolate as A. pitti. A. baumannii isolates were highly resistant to all antibiotics tested, while the others were susceptible to ciprofloxacin and ampicillin/sulbactam. Quinolone resistance, found only in A. baumannii, was associated with mutations in the QRDR region of gyrA and parC genes. Conclusion This is the first investigation in Colombia that has identified ACB complex species using molecular methods, and determined differences in antibiotic resistance and resistance genes among the species. It is of the highest importance to identify isolates to the species level for future resistance and epidemiology studies in our region (AU)

Introducción Actualmente, los hospitales en Colombia utilizan únicamente métodos fenotípicos automatizados para la identificación de aislamientos del complejo Acinetobacter calcoaceticus - baumannii (ACB). La similitud entre estas especies no permite que se diferencien por métodos fenotípicos ya sean estos manuales o automatizados, llevando a que los aislamientos se identifiquen como A. baumannii o como pertenecientes al complejo ACB en las instituciones hospitalarias. Nuestro objetivo fue identificar a nivel de especie, 60 aislamientos de cuatro hospitales, identificados como del complejo ACB, evaluar su resistencia a antibióticos y detectar genes de resistencia. Métodos Para la identificación de especies se amplificaron la región intergénica espaciadora de los genes 16S y 23S rRNA y la secuencia parcial del gen rpoB. Estos amplificados y algunos genes de resistencia se secuenciaron y se compararon utilizando la herramienta BLAST. Se detectaron por PCR genes de resistencia a cefalosporinas, carbapenemes y aminoglicósidos. Se evaluaron posibles mutaciones en la región determinante de resistencia a quinolonas (QRDR). Se determinó por PCR la asociación de ISAba-1con los genes blaOXA y blaADC. Resultados Con las secuencias de la región ITS 16S-23S rRNA y el gen rpoB, se identificaron 51 aislamientos (..) (AU)

Detection of the aminoglycosidestreptothricin resistance gene cluster ant(6)-sat4-aph(3')-III in commensal viridans group streptococci

High-level aminoglycoside resistance was assessed in 190 commensal erythromycin-resistant alpha-hemolytic streptococcal strains. Of these, seven were also aminoglycoside-resistant: one Streptococcus mitis strain was resistant to high levels of kanamycin and carried the aph(3’)-III gene, four S. mitis strains were resistant to high levels of streptomycin and lacked aminoglycoside-modifying enzymes, and two S. oralis strains that were resistant to high levels of kanamycin and streptomycin harbored both the aph(3’)-III and the ant(6) genes. The two S. oralis strains also carried the ant(6)-sat4- aph(3’’)-III aminoglycoside-streptothricin resistance gene cluster, but it was not contained in a Tn5405-like structure. The presence of this resistance gene cluster in commensal streptococci suggests an exchange of resistance genes between these bacteria and enterococci or staphylococci (AU)

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Tumour cells resistance in cancer therapy

Resistance to chemotherapeutic drugs presents a big caveat for cancer treatment. In this review we will describe the molecular mechanisms involved in chemoresistance, discussing the mechanisms of resistance related to tumour microenvironment, as well as their intracellular mechanisms. Chemoresistance can also appear as a consequence to treatments with new anticancer drugs. In this sense, we will exemplify this type of resistance discussing mechanisms of action of epidermal growth factor receptor (EGFR) inhibitors. We conclude that the main problem of chemoresistance is due to its pleiotropic and multifactorial nature(AU)

La vieja batalla entre la especie humana y el bacilo de Koch. ¿Es posible soñar con erradicar la tuberculosis? / The old battle between the human species and Koch’s bacillae. Can one dream of eradicating tuberculosis?

El presente trabajo trata de analizar la complejidad de la vieja batalla que lleva librando, desde hace millones de años, la especie humana contra Mycobacterium tuberculosis, intentando realizar un repaso de todos los conocimientos que se tienen sobre esta enfermedad y de lo más importante de lo que puede acontecer en el futuro, con el fin de llegar a la conclusión de si es posible acabar soñando con erradicar esta enfermedad que tanto daño ha causado a la humanidad. A pesar de que la especie humana tiene suficientes conocimientos para vencer la batalla a M. tuberculosis, importantes condicionantes, sobre todo sociales (pobreza, inmigración, VIH, MDR), están favoreciendo la guerra del lado del bacilo. Y que, incluso aplicando adecuadamente todos los buenos conocimientos adquiridos para el control de la TB (detección y curación de casos, quimioprofilaxis, vacunación BCG, etc.), se tardaría aún varios siglos en poder conseguir la erradicación. Sólo la posibilidad de descubrir una vacuna 100% eficaz, o el descubrimiento de nuevas asociaciones antimicrobianas que pudiesen curar la enfermedad en un plazo no superior a 15 días, podría acelerar este ritmo hacia la erradicación. Pero, lamentablemente, no existen fundamentos que permitan soñar con que cualquiera de estas dos posibilidades pueda cumplirse en los próximos 10-20 años. Por lo tanto, el sueño de erradicar la TB es un sueño muy antiguo, pero, lamentablemente, aún muy lejano

This article analyses the complexity of the age-old battle that the human species has been waging for millions of years against Mycobacterium tuberculosis. We review all of the knowledge available about this disease, and the most important future developments, in order to reach the conclusion that it is indeed possible to dream of eradicating this disease that has caused such harm to humanity. In spite of the human species possessing sufficient knowledge to win the battle against Mycobacterium tuberculosis, important conditioning factors, above all social in character (poverty, immigration, HIV, MDR), are favouring the bacteria in this war. And, in spite of suitably applying all of the positive knowledge acquired for the control of TB (detection and cure of cases, chemoprofilaxis, BCG vaccination, etc.), it will still take several centuries to achieve its eradication. Only by discovering a vaccine that is 100% efficient, or the discovery of new anti-microbial associations that could cure the disease in no longer than 15 days, could accelerate this advance towards its eradication. But, unfortunately, there are no reasons allowing us to dream that either of these two possibilities can be fulfilled in the next 10 to 20 years. Therefore, the dream of eradicating TB is a very old dream, but one that unfortunately remains very distant

Expresión de proteínas relacionadas con resistencia a múltiples fármacos (MDR-proteínas) en tumores sólidos / Expresssion of multidrug resistance (MDR)-associated proteins in solid tumors

Las causas de que una célula tumoral sea resistente a la quimioterapia son muchas y de variada naturaleza. El motivo del presente trabajo es realizar una revisión y una puesta al día de una de estas posibles causas, en concreto, la expresión de proteínas relacionadas con la resistencia a múltiples fármacos (AU)

The causes of drug resistance in tumor cells vary widely. The present study aims to provide an update of multidrug resistance in tumor cells and, in particular, of multidrug resistance-associated proteins (AU)

The roles of the pfcrt 76T and pfmdr1 86Y mutations, immunity and the initial level of parasitaemia, in predicting the outcome of chloroquine treatment in two areas with different transmission intensities.

The resistance of Plasmodium falciparum to chloroquine (CQ) is probably mediated by point mutations in two genes: pfcrt and pfmdr1. The aim of the present study was to investigate, in patients treated with CQ, the association between host factors, such as immunity and initial level of parasitaemia, and the ability to clear P. falciparum parasites carrying the key chloroquine-resistance (CQR) mutations, pfcrt 76T and pfmdr1 86Y. Identical CQ-efficacy trials were performed in 51 young children (aged <5 years) from Kibaha, in north-western Tanzania, and 44 patients (aged 3-57 years) from Darawish, in eastern Sudan. In both areas, all the CQ-treatment failures had infections with the 76T and 86Y alleles before treatment. Although the presence of these two alleles was significantly associated with treatment failure in Sudan (P=0.001), the corresponding association in Tanzania did not reach statistical significance (P=0.1). Of the 39 patients from Darawish and 44 from Kibaha who harboured parasites with the CQR mutations, 12 and 19, respectively, managed to clear their parasitaemias. The ability to clear CQR parasites was significantly associated with the initial level of parasitaemia (with P-values of 0.05 in Tanzania and 0.01 in Sudan) and with age-- the best surrogate for protective immunity in endemic areas (with P-values of 0.02 in Tanzania and 0.001 in Sudan). These results confirm previous observations that indicated that the 76T and 86Y alleles play a role in the mechanism of CQR, although other factors, such as level of parasitaemia when treated and age, are also important. The 76T and 86Y alleles could still be used as predictive markers for CQR, in non-immune individuals and low-transmission areas.

Multidrug resistance-1 (MDR-1): a new target for T cell-based immunotherapy.

Acquired multidrug resistance (MDR) remains a major challenge in the treatment of cancer with chemotherapeutic drugs. It can be mediated by the up-regulated expression of different proteins within the tumor cell membrane. Here, we used murine multidrug resistance-1 (MDR-1) as a target-antigen for the immunotherapy of cancer. We successfully demonstrated that peripheral T cell tolerance can be broken by oral administration of a DNA vaccine encoding MDR-1 and carried by attenuated Salmonella typhimurium to secondary lymphoid organs. Thus, mice, immunized orally three times at 2-wk intervals and challenged 2 wk thereafter with either MDR-1 expressing CT-26 colon carcinoma cells or MDR-1 expressing Lewis lung carcinoma cells, revealed a significant increase in life span. This was evident, when compared with animals either vaccinated with the empty control vector or challenged with the parental cell lines lacking overexpression of MDR-1. The immune response induced was antigen-specific and CD8+ T cell-mediated. The presence of the target antigen led to up-regulation of activation markers on CD8+ T cells and resulted in a strong cytotoxic T cell response as well as lysis of tumor target cells in vitro. We furthermore established the vaccine to be an effective treatment for established multi-drug-resistant tumor metastases, resulting in a significantly increased life span of experimental animals. Absence of CD8+ T cells due to in vivo depletion led to abrogation of effectiveness. Taken together, our results demonstrate that T cell tolerance against the MDR-1 self-antigen can be broken. It is anticipated that the combination of such an approach with chemotherapy could lead to more effective treatments of cancer.

Glycoprotein 170 induces platelet-activating factor receptor membrane expression and confers tumor cell hypersensitivity to NK-dependent cell lysis.

Multidrug resistance (MDR) confers resistance to anticancer drugs and reduces therapeutic efficiency. It is often characterized by the expression of the MDR1 gene product P-glycoprotein (or gp170) at the membrane of tumor cells. To further propose a potential complementary tool in cancer treatment, the sensitivity of gp170 tumor cells to NK-dependent lysis was investigated. Two kinds of cells were generated from wild-type K562 erythroleukemic cells: the first were derived from Taxol-selected cells and cloned, whereas the second were retrovirally transduced by the cDNA of the MDR1 gene. The last process was also applied to the human embryonal carcinoma cells called Tera-2 cells. First, both cloned and MDR-1 K562 cells appeared highly susceptible to naive NK cell killing. Interestingly, in addition, Tera-2 cells that were not sensitive to NK lysis could be killed when they expressed gp170 at their membranes. In previous data, we demonstrated that NK cell release of bimolecular complexes composed of perforin and platelet-activating factor (PAF) interacting with the PAF-R, which has to be expressed on the target cell membranes, were components of NK tumor cell killing. In the present study, we show that gp170 has the capacity to drive constitutive PAF-R expression on tumor cells, which could be responsible for hypersensitivity to NK lysis and accelerated cell death.

[Internalization of antibody-targeted immunonanoparticles into human hepatoma cells and its reversal effect on MDR].

OBJECTIVE: To observe if antibody-targeted immunonanoparticles could internalize into sensitive and multidrug resistance (MDR) cells of human hepatoma; and to study if the immunonanoparticles could reverse the MDR. METHODS: Human hepatoma-specific adriamycin-loaded human serum albumin immunonanoparticles (HAb18-ADR-HSA-NP) were incubated with human hepatoma sensitive cell line (SMMC-7721) or MDR cell line (SMMC-7721/MDR+) and the internalization of immunonanoparticles were observed by laser confocus microscopy, scanning electron microscopy and transmission electron microscopy; MTT colorimetric assay was used for assaying in vitro cytotoxicities of HAb18-ADR-HSA-NP to the resistant variant cells. Then based on these data, IC50 value of the immunonanoparticles and RF (Resistant Factor) of MDR cells were calculated. RESULTS: Laser confocus microscopy showed that many fluorescent particles (labeled immunonanoparticles) tightly adsorbed to SMMC-7721 cells and were also seen in cytoplasm of SMMC-7721 cells. When incubated with immunonanoparticles at 37 degrees C, many of immunonanoparticles were visualized in cytoplasm of SMCC-7721 or SMCC-7721/MDR+. These immunonanoparticles-contained cells exhibited damaged ultrastructures and the damage degree depended on incubation time. When the human hepatoma cells were pretreated with HAb18 antibody and incubated with immunonanoparticles, few immunonanoparticles were seen in cytoplasm of the cells, suggesting antibody-specific internalization of the immunonanoparticles. Scanning electron microscopy demonstrated specific binding of the immunonanoparticles to the resistant variant cells. That immunonanoparticles exerted enhanced cytotoxicity to the resistant variant cells was demonstrated by a decrease of RF value of MDR cells, compared with free ADR (4.4 vs. 2.1). CONCLUSION: Human hepatoma-specific adriamycin-loaded human serum albumin immunonanoparticles could specifically internalize into sensitive or multidrug resistance cells of human hepatoma via antibody direction. The immunonanoparticles could enhance the sensitivity of MDR cells to ADR cytotoxicity, suggesting its reverse effect on MDR.

Expression of CD20 on acute lymphoblastic leukemia cells in children.

CD20 determinant expressed on B precursors is associated with regulation of proliferation, apoptosis and maturation of these cells. The acute lymphoblastic leukemia "common" type (cALL) based on expression of CD20 is subdivided in type I and II. However, the clinical significance of CD20 expression on cALL and significance of cALL type I and II discernment are not fully elucidated. The association of CD20 expression with the expression of multidrug resistance molecule (MDR), CD34, atypical immunophenotypes of leukemia cells and response to induction therapy were determined in the group of 147 patients with acute lymphoblastic leukemia (ALL) B progenitor type (ALL-proB -14 patients) and common type (cALL-133 patients). The expression of CD20 on leukemia cells was studied routinely at diagnosis before the therapy. This expression was noted on leukemia cells of 6 ALL-proB patients (42.8%) and 66 cALL patients (49.6%). The expression of CD20 showed no association with the expression of CD34, CD22 and MDR. The reverse association was observed between CD20 expression and the presence of co-expression of myeloid (CD13, CD33, CD65, CD15) and T lymphoid determinants (CD2, CD5, CD7) on leukemia cells. The effect of induction therapy analyzed as time of blast cells cytoreduction in peripheral blood and time of reaching the complete remission showed the slower clearance of peripheral blood from blast cells associated with expression of CD20. There was no association of CD20 expression with the time of reaching the hematological remission. The above results suggested a "protective" role of CD20 against co-expression of other determinants (myeloid and lymphoid) and no association with the results of induction therapy.

Pharmacokinetic and prognostic significance of intestinal MDR1 expression in recipients of living-donor liver transplantation.

BACKGROUND: Living-donor liver transplantation (LDLT) and subsequent immunosuppressive therapy with tacrolimus have been cornerstones in the recovery of patients from end-stage liver failure, but there has been no critical dosage regimen for tacrolimus therapy, especially the initial dosage. In this study, we examined whether the absorptive barriers, multidrug resistance protein (MDR1), or cytochrome P450 IIIA4 (CYP3A4) are important pharmacokinetic factors for tacrolimus and are prognostic indicators for LDLT outcome. METHODS: We used competitive polymerase chain reaction to evaluate the messenger ribonucleic acid (mRNA) expression levels of MDRL And Cyp3A4 in mucosal cells of the upper jejunum from a part of the Rroux-en- Y limb for biliary reconstruction during LDLT of recipients (n = 48). The tacrolimus dosage was started at an oral dose of 0.075 mg/kg every 12 hours and adjusted on the basis of its whole-blood trough level by use of a semiautomated microparticle enzyme immunoassay. RESULTS: The mRNA expression level of MDR1 (r = -0.776), but not CYP3A4 (r = -0.094), was inversely related to the concentration/dose ratio of tacrolimus. High levels of MDR1, but not CYP3A4, were strongly associated with reductions in survival rates after LDLT with the Kaplan-Meier method and log-rank statistics (P =.020 and P =.135, respectively). With use of a Cox regression procedure, high levels of MDR1 (relative risk, 12.99; 95% confidence interval, 1.64-103.23), but not CYP3A4 (relative risk, 0.93; 95% confidence interval, 0.87-1.00) appeared to be a significant prognostic indicator for poor survival. CONCLUSIONS: Intestinal MDR1 is not only a good probe with which to predict the interindividual variation in tacrolimus pharmacokinetics after LDLT but also a powerful prognostic indicator for the outcome of LDLT.

Detection of intracellular antigens by flow cytometry: comparison of two chemical methods and microwave heating.

Detection of intracellular antigens by flow cytometry requires effective fixation and permeabilization of the cell membrane. This study compares three fixation/permeabilization techniques: two commercial chemical reagents, the ORTHOPermeaFix (OPF) and the FIX&PERM Cell Permeabilization Kit (F&P), and a novel method based on microwave heating (MWH). They have been applied to the detection of two nuclear (p53 and rb/p105) and two cytoplasmic (bcl-2 and mdr-1/gp-170) antigens, using positive- and negative-control cell lines and peripheral blood mononuclear cells. Western blotting was performed as a control of protein expression. For the four antigens assessed, cellular morphology, discrimination between intact cells and debris, percentage of positive cells, and mean fluorescence intensity were examined. For this last parameter, the assessment of the MWH technique was performed using SD and a graphical approach inspired by the concepts described by Bland and Altman (Lancet 1986;346: 1085-7) as well as Petersen et al. (Clin Chem 1997;43: 2039-46). The statistical analysis shows that MWH is comparable to the commercial methods and that its reproducibility is also equivalent to OPF and F&P. As assessed for some of the most clinically relevant intracytoplasmic and intranuclear antigens, the MWH method appears to be a valuable and inexpensive alternative. It is worth noting that, unlike commercial reagents, MWH altered surface antigens. Interestingly, this feature, which would prevent cell selection on the basis of combined membrane and intracellular epitopes, is associated with a decrease of nonspecific background fluorescence.

A novel model of inflammatory bowel disease: mice deficient for the multiple drug resistance gene, mdr1a, spontaneously develop colitis.

The murine multiple drug resistance (mdr) gene, mdr1a, encodes a 170-kDa transmembrane protein that is expressed in many tissues including intestinal epithelial cells, a subset of lymphoid cells and hematopoietic cells. We report that mdr1a knockout (mdr1a-/-) mice are susceptible to developing a severe, spontaneous intestinal inflammation when maintained under specific pathogen-free animal facility conditions. The intestinal inflammation seen in mdr1a-/- mice has a pathology similar to that of human inflammatory bowel disease (IBD) and is defined by dysregulated epithelial cell growth and leukocytic infiltration into the lamina propria of the large intestine. Treating mdr1a-/- mice with oral antibiotics can both prevent the development of disease and resolve active inflammation. Lymphoid cells isolated from mice with active colitis are functionally reactive to intestinal bacterial Ags, providing evidence that there is enhanced immunologic responsiveness to the normal bacterial flora during IBD. This study is the first description of spontaneous colitis in a gene knockout mouse with an apparently intact immune system. This novel model of spontaneous colitis may provide new insight into the pathogenesis of IBD, the nature of dysregulated immune reactivity to intestinal bacterial Ags, and the potential functional role of mdr genes expressed in the cells and tissues of the colonic microenvironment.