Phenomenon Of Drug Resistance Research Articles

1244P - The decrease of TMB, TNB and HLA expression are the mechanism of drug resistance of NSCLC to immunosuppressive PD-1/PD-L1

BackgroundImmunotherapy, as a new treatment, has become an option after surgery, radiotherapy and chemotherapy, and its status is becoming more and more important. However, after PD-1/PD-L1 as the target of drug treatment, it is inevitable that the phenomenon of drug resistance will arise caused by the reduction of drug sensitivity. However, there is still no clear understanding of the mechanism of drug resistance to PD-1/PD-L1, which needs to be further explored. MethodsTissue biopsy was performed in patients with renal metastasis of lung squamous cell carcinoma, primary lung (P), renal metastases (M1), and PD-1-treated renal metastases (M2). Then, P1, M1, and M2 were sequenced by whole exome genome sequencing (WES) to construct a gene evolution map and neoantigens evolution tree. Furthermore, the genomic differences between P and M1, as well as between M1 and M2, were found, and the evolution of tumor was demonstrated. ResultsAfter WES, we found that 139 groups of mutations [tumor mutational burden (TMB)=4.48 mutations/MB] were detected in the most sensitive P for PD-1 treatment, and 67 neoantigens were expressed [tumor neoantigens burden (TNB)=2.16 neoantigens /MB]. Among them, 22 groups were P-specific mutations, and 9 kinds of P-specific neoantigens were expressed, among the unique neoantigens of P, 77.8% (7/9) of the neoantigens were not deleted by HLA (human leukocyte antigen). The sensitivity of patients with M1 to PD-1 was significantly lower than that of P. WES showed that a total of 201 mutations (TMB=6.48 mutation / MB) were detected in M1. Expression of 93 neoantigens (TNB=3.00 neoantigens / MB). Among them, 85 groups were M1-specific mutations, 35 kinds of M1-specific neoantigens were expressed, of which 51.4% (18/35) of the neoantigens had no deletion of HLA. M2 was resistant to PD-1, and a total of 135 mutations were detected in WES (TMB=4.35 mutation / MB), expressed 88 neoantigens (TNB=2.84 neoantigens / MB), 91 group was M1 and M2 common mutation, 43 group was M2 specific mutation. Expression of 21 kinds of M2 specific neoantigens. The HLA presenting these neoantigens was deleted. ConclusionsThe decrease of TMB, TNB and HLA expression are the important mechanisms of PD-1/PD-L1 resistance in non-small cell lung cancer. Legal entity responsible for the studyHenan Cancer Hospital. FundingHas not received any funding. DisclosureThe author has declared no conflicts of interest.

PB1888 FEATURES OF CYSTEIN-RICH PROTEIN METALLOTHIONEIN FUNCTIONING IN CHRONIC B-LYMPHOCYTIC LEUKEMIA CELLS

Background: The main approach to the hematological cancers treatment is an intensive chemotherapy. However, often its ineffectiveness could be result of the phenomenon of multiple drug resistance (MDR) – immunity of cancer cells to cytostatic drugs. The most important MDR pathways are increased drug efflux resulting in reduced its accumulation, activation of detoxification mechanisms in tumor cells, altered activities of certain enzymes and level of intracellular thiols such as metallothioneins or reduced glutathione which bind compounds toxic for cells. Study and comprehension of these mechanisms will enable the design of suitable techniques and procedures for malignant tumor treatment. Aims: To investigate the level of expression of cystein-rich proteins metallothioneins in lymphocytes of patients with chronic B-lymphocytic leukemia (B-CLL) and to find out their role in the maintenance of redox state under this pathological state. Methods: Lymphocytes were separated from the B-CLL patient's and healthy donor's peripheral blood by density gradient centrifugation on histopaque. Monoclonal antibodies UC1MT (Abcam), UIC2 (Immunotech), MRP1 (R&D) were used to evaluate MTs I-II types, ABCB1, ABCC1 expression, respectively. Reactive oxygen species (ROS) level was assessed using fluorescent probe CM-H2DCFDA (Invitrogen). All investigations were carried out on the FACScanto II (BD). Results: A significant reduction (1.5–2.0-fold) of the MT expression level in B-CLL lymphocytes in comparison to the last one in healthy donors was reveled, despite the proven role of this protein in the detoxification processes from drugs. Additionally a comparative evaluation of expression of the membrane protein-transporters ABC family associated with MDR – ABCB1/P-gp and ABCC1/MRP1 was conducted. Theirs significant rise was found in tested group of B-CLL patients. Moreover, the rise of the ABCC1/ABCB1 expression ratio in leukemia cells reveled under enhanced ROS level compare to normal cells. Summary/Conclusion: Thus, in B-CLL cells the role of MT in the maintaining of redox state (ROS sequestration) is decreased under the rise of ABCC1 function. It is clear that the potential of MT as the scavengers of ROS is not fully understood, but the present data show that this protein could be selected as a target for novel treatment strategies for patients with leukemia.

Functional and transcriptomic characterization of carboplatin-resistant A2780 ovarian cancer cell line

BackgroundOvarian cancer is a significant cancer-related cause of death in women worldwide. The most used chemotherapeutic regimen is based on carboplatin (CBDCA). However, CBDCA resistance is the main obstacle to a better prognosis. An in vitro drug-resistant cell model would help in the understanding of molecular mechanisms underlying this drug-resistance phenomenon. The aim of this study was to characterize cellular and molecular changes of induced CBDCA-resistant ovarian cancer cell line A2780.MethodsThe cell selection strategy used in this study was a dose-per-pulse method using a concentration of 100 μM for 2 h. Once 20 cycles of exposure to the drug were completed, the cell cultures showed a resistant phenotype. Then, the ovarian cancer cell line A2780 was grown with 100 μM of CBDCA (CBDCA-resistant cells) or without CBDCA (parental cells). After, a drug sensitivity assay, morphological analyses, cell death assays and a RNA-seq analysis were performed in CBDCA-resistant A2780 cells.ResultsMicroscopy on both parental and CBDCA-resistant A2780 cells showed similar characteristics in morphology and F-actin distribution within cells. In cell-death assays, parental A2780 cells showed a significant increase in phosphatidylserine translocation and caspase-3/7 cleavage compared to CBDCA-resistant A2780 cells (P < 0.05 and P < 0.005, respectively). Cell viability in parental A2780 cells was significantly decreased compared to CBDCA-resistant A2780 cells (P < 0.0005). The RNA-seq analysis showed 156 differentially expressed genes (DEGs) associated mainly to molecular functions.ConclusionCBDCA-resistant A2780 ovarian cancer cells is a reliable model of CBDCA resistance that shows several DEGs involved in molecular functions such as transmembrane activity, protein binding to cell surface receptor and catalytic activity. Also, we found that the Wnt/β-catenin and integrin signaling pathway are the main metabolic pathway dysregulated in CBDCA-resistant A2780 cells.

Quantitative Occurrence of Antibiotic Resistance Genes among Bacterial Populations from Wastewater Treatment Plants Using Activated Sludge

Wastewater treatment plants (WWTPs) are an important reservoir in the development of drug resistance phenomenon and they provide a potential route of antibiotic resistance gene (ARGs) dissemination in the environment. The aim of this study was to assess the role of WWTPs in the spread of ARGs. Untreated and treated wastewater samples that were collected from thirteen Polish WWTPs (applying four different modifications of activated sludge–based treatment technology) were analyzed. The quantitative occurrence of genes responsible for the resistance to beta-lactams and tetracyclines was determined using the real-time PCR method. Such genes in the DNA of both the total bacterial population and of the E. coli population were analyzed. Among the tested genes that are responsible for the resistance to beta-lactams and tetracyclines, blaOXA and blaTEM and tetA were dominant, respectively. This study found an insufficient reduction in the quantity of the genes that are responsible for antibiotic resistance in wastewater treatment processes. The results emphasize the need to monitor the presence of genes determining antibiotic resistance in the wastewater that is discharged from treatment plants, as they can help to identify the hazard that treated wastewater poses to public health.

Are Carbonic Anhydrases Suitable Targets to Fight Protozoan Parasitic Diseases?

Protozoans belonging to Plasmodium, Leishmania and Trypanosoma genera provoke widespread parasitic diseases with few treatment options and many of the clinically used drugs experiencing an extensive drug resistance phenomenon. In the last several years, the metalloenzyme Carbonic Anhydrase (CA, EC 4.2.1.1) was cloned and characterized in the genome of these protozoa, with the aim to search for a new drug target for fighting malaria, leishmaniasis and Chagas disease. P. falciparum encodes for a CA (PfCA) belonging to a novel genetic family, the η-CA class, L. donovani chagasi for a β-CA (LdcCA), whereas T. cruzi genome contains an α-CA (TcCA). These three enzymes were characterized in detail and a number of in vitro potent and selective inhibitors belonging to the sulfonamide, thiol, dithiocarbamate and hydroxamate classes were discovered. Some of these inhibitors were also effective in cell cultures and animal models of protozoan infections, making them of considerable interest for the development of new antiprotozoan drugs with a novel mechanism of action.

A Structural View on Medicinal Chemistry Strategies against Drug Resistance.

The natural phenomenon of drug resistance is a widespread issue that hampers the performance of drugs in many major clinical indications. Antibacterial and antifungal drugs are affected, as well as compounds for the treatment of cancer, viral infections, or parasitic diseases. Despite the very diverse set of biological targets and organisms involved in the development of drug resistance, the underlying molecular mechanisms have been identified to understand the emergence of resistance and to overcome this detrimental process. Detailed structural information on the root causes for drug resistance is nowadays frequently available, so next-generation drugs can be designed that are anticipated to suffer less from resistance. This knowledge-based approach is essential for fighting the inevitable occurrence of drug resistance.

On the mechanism of antibiotic resistance and fecal microbiota transplantation.

Antibiotic resistance is a growing threat to human health and is caused by mainly the overuse of antibiotics in clinical medicine. Clinically, drug resistance emerges after a series of antibiotic treatments, implying that each treatment changes the intestinal flora composition and the accumulations of these changes induce the resistance. But mathematically, this cumulative effect cannot be achieved by a general population model, because the system will return to its pre-treatment state (an isolated steady state) after each cure. Based on the fact that sensitive bacteria and resistant bacteria are similar in most respects except their reactions to antibiotics, we developed a mathematical model with a specific phase-space structure: instead of isolated points, the steady states of this system compose one-dimensional manifolds (line segments). This structure explains the fundamental mechanism of antibiotic resistance: after antibiotic treatment, the system cannot return to the pretreatment healthy steady state but rather slightly moves along the manifold to a different steady state. Each use of antibiotics can change the ratio of resistant to susceptible pathogens in the host. The change the ratio can persist and accumulate, and finally promotes the emergence of antimicrobial resistance. We also assessed key factors (such as pathogen composition, the amount and composition of beneficial bacteria, medication duration and bactericidal rates of drugs) influencing the development of drug resistance. In addition, we clarified how fecal microbiota transplantation affects the treatment of antibiotic-resistant infections. The effect is essentially a transfer towards the healthy state in the phase space. Finally, based on the mechanisms revealed by the mathematical models, we suggested some strategies to delay or prevent the emergence of drug resistance. These findings not only provide a solid theoretical basis for the treatment of antimicrobial resistance, but also inspire clues to the phenomenon of drug resistance.

Abstract 757: Novel warheads for targeted therapies of cancer: The concept and design of oxime-ether-based pro-PBDs

Abstract Pyrrolo[2,1-c][1,4]benzodiazepine (PBD) antibiotics are a class of natural products produced by various actinomycetes bacteria. PBD-dimers function as sequence-selective DNA-crosslinking, alkylating compounds which are considerably more potent than systemic chemotherapeutic agents. PBDs recognize and bond to specific sequences in the DNA minor groove. After DNA insertion, a covalent aminal bond is formed through nucleophilic attack of the N-2 of a guanine (G) base on the electrophilic C-11 imine of PBD. The end result is obstruction of tumor cell division without any significant distortion of the DNA's helical structure, thus potentially avoiding the common phenomenon of drug resistance. In recent years, synthetic PBD-dimers have emerged as a promising class of payloads for conjugates in the field of targeted cancer therapies. Unfortunately, many PBD conjugates preserve the strongly alkylating (electrophilic C-11) imine moiety within their structural framework, which can react in a deleterious manner while in circulation on their way to their intended targets. As an elegant solution to this inherent problem, we designed diazepine-ring-opened conjugated prodrugs lacking the imine functionality. In our design concept, we replaced this moiety with its synthetic precursors: an aldehyde and an amine. The later provided an attachment point to targeting ligands through self-immolative linker systems, whereas the former was masked as an oxime ether. Such oxime ethers are known to exhibit enhanced stability under physiological conditions. Once the prodrug (pro-PBD) conjugate enters a targeted cell, cleavage of the linker system triggers the generation of an aromatic amine. As we discovered, an intramolecular ring-closure subsequently takes place as the aromatic amine adds directly into the sp2 center of the oxime ether to form the imine condensate and ultimately the 1,4-diazepine ring in a PBD framework. In our pro-PBDs, we envision exploiting their aromatic amines as a part of an arsenal of self-immolative linker systems for small molecule conjugation. To prove the range of applications for this new class of latent DNA-alkylators, we modified their linkers to tailor the kinetics of prodrug release and drug formation. The utility of these novel warheads and linker systems towards the design of Small Molecule Drug Conjugates (SMDC) for targeted cancer therapies will also be discussed in the presented poster. One can predict that any of the presented pro-PBDs could be easily incorporated as novel payloads in Antibody-Drug Conjugates (ADCs). Citation Format: Iontcho Vlahov, Albert Felten, Ning Zou, Kevin Wang, Hari K. Santhapuram, Paul Kleindl, Spencer Hahn, Jeremy Vaughn, Christopher Leamon. Novel warheads for targeted therapies of cancer: The concept and design of oxime-ether-based pro-PBDs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 757.

Pathogenic and diagnostic analysis of bacterial meningitis children in the Midwest area

Objective To investigate the diagnostic analysis and pathogenic characteristics of bacterial meningitis (BM) in children in Midwest area in China. Methods Clinical and pathogenic data of inpatients with BM were analyzed retrospectively at Xiangya Hospital, Central South University and Children′s Hospital of Chongqing Medical University, including age, gender, index of peripheral inflammation, cerebrospinal fluid routine, biochemistry, culture, drug sensitivity and image change. Results In total, 446 cases with BM were analyzed in this study.The male-to-female ratios was 1.671.00.Peripheral blood detected abnormal ratios of white blood cell (WBC), C reactive protein(CRP) and procalcitonin (PCT) which were 67.7%(302/446 cases), 64.9%(268/413 cases) and 71.7%(279/389 cases), respectively.Cerebrospinal fluid detected abnormal ratios of WBC count, glucose and protein, which were 76.5%(332/434 cases), 71.2%(306/430 cases) and 91.7%(397/433 cases), respectively; 79.4% of the patients revealed abnormal head CT/MRI image.Bacterial culture positive rate was 33.6%(150/446 cases), and the positive rates of abnormality in peripheral blood WBC, CRP, PCT or cerebrospinal fluid WBC, glucose and protein were 34.9% (116/332 cases), 34.8%(138/397 cases), 36.6%(112/306 cases), respectively, which were higher than the normal patients, who were 29.4%(30/102 cases), 25.0%(9/36 cases), 21%(26/124 cases), respectively.The most common pathogenic bacteria were Streptococcus pneumoniae, Escherichia coli and coagulase negative staphylococcus.Infants within one year presented dominantly with infection of Escherichia coli, accounting for 26.6%(29/109 cases). Children above 1-year-old presented dominantly with Streptococcus pneumoniae, accounting for 61.0%(25/41 cases). A drug-resistance phenomenon was common among pathogenic bacteria. Conclusion Abnormality in peripheral blood WBC, CRP, PCT or cerebrospinal fluid WBC, glucose and protein, and subdural effusion/empyema can help the early diagnosis and differential diagnosis of BM.The most common pathogenic bacteria in Midwest area of China are Streptococcus pneumoniae, Escherichia coli and coagulase negative staphylococcus, which suggests recommend the application of Streptococcus pneumoniae vaccine. Drug-resistance phenomenon to pathogens is very common.For the treatment strategy, it should be made and adjusted timely according to the drug sensitivity and common hospital antimicrobial spectrum. Key words: Bacterial meningitis; Child; Pathogenic analysis; Diagnostic analysis

Characteristics and drug resistance of non-O157 Shiga toxin-producing E. coli in animal feces, from Shandong Province

Objective: To understand the infection status, characteristics and drug resistance of non-O157 Shiga toxin-producing E. coli (STEC) in animal feces in Shandong Province. Methods: From 2015 to 2016, convient sampling method was used to collect 1 022 fresh feces of animals in Weishan county and Laizhou city, and 24 non-O157 STEC were isolated. The serotypes of non-O157 STEC strains were confirmed through serum agglutination test. The susceptibility was explored through the antimicrobial sensitivity experiments. ESBLs activity was confirmed by double-disc diffusion. PCR method was used to detect the resistance genes. PFGE typing was operated to assess the relatedness and variability of the strains. The multi-locus sequence typing (MLST) was adopted to get the allelic profile and ST sequence of strains. Analysis was made on the evolutionary relationship between different ST groups was made through CLC Sequence Viewer and Counting Express. Results: A total of 24 non-O157 STEC were isolated from animal feces. 23 strains were from pig feces, and 1 strain was from cow feces, and the serotypes were more dispersed. All of the 24 strains carried stx2 genes. The highest resistance rate was sulfamethoxazole(22 strains), the mount of cotrimoxazole and nalidixic acid was 18 strains, chloramphenicol was 13 strains, tetracycline was 19, and there was a phenomenon of multiple drug resistance. The drug resistance spectrum was sulfamethoxazole tetracycline-compound novammin-naphthidine-chloramphenicol. All strains were sensitive to cefepime and imipenem. The ESBLs confirmatory test showed that 4 strains of non O157 STEC produced beta lactamase. PCR detected 7 resistance genes, and 4 tetracycline resistance genes (Tet A, Tet B, tetC and tetD) were detected. The beta lactamase resistance genes (blaSHV-1, bla CTX-M, bla TEM) were all negative. 24 strains were divided into 15 PFGE types, and their clustering results were more dispersed and no dominant PFGE type. There were 11 kinds of MLST types, most of them are ST540 and ST5133 types, each of which was 4 strains, and clustered into 1 MLST genomes. Conclusion: The serotypes of non-O157 STEC in animal feces O157 STEC were dispersed, and the resistant rate to common antibiotic was high. MLST typing results presents obvious polymorphism. Surveillance and manage ment of these strains should be strengthened.

Non-clinical isolates as potential reservoirs of antibiotic resistance in Port Harcourt, Nigeria.

IntroductionMultidrug resistance (MDR) is a growing problem worldwide. This type resistance often arises due to the sequential acquisition of drug resistance determinants and subsequent clonal spread. It is therefore important to determine possible reservoirs of these MDR gene to help set out control strategies. This study was aimed at analysing susceptibility patterns of various non-clinical Gram negative bacterial strains to determine their potential as reservoirs of MDR.MethodsThirty-five non-clinical Gram negative bacteria were identified and susceptibility profile determined using standard methodologies.ResultsFindings showed a preponderance of Pseudomonas aeruginosa and Escherichia Coli. Resistance rates of above 80% were noted in 50% of antibiotics, though none of the isolates were resistant to Ofloxacin. Majority of isolates (68.6%) had a multiple antibiotic resistance (MAR) index greater than 0.5, but only 20% of Escherichia Eoli. were found in this category. A high level of MDR was noted in this study (71.4%), but again only 20% of these were Escherichia Coli.ConclusionGram negative bacteria are the most common group of bacteria frequently encountered in clinical microbiology. In more recent years, infections with these organisms have been further complicated by the phenomenon of drug resistance. Non-clinical isolates have been postulated as possible reservoirs. Findings from this study of widespread multidrug resistance support this idea. This study however highlights the lack of MDR in Escherichia Coli, which is promising. More extensive studies will need to be carried out to properly assess the role of non-clinical isolates as reservoirs of MDR determinants.

Transcriptome profiling identified differentially expressed genes and pathways associated with tamoxifen resistance in human breast cancer.

Tamoxifen (TAM) resistance is an important clinical problem in the treatment of breast cancer. In order to identify the mechanism of TAM resistance for estrogen receptor (ER)-positive breast cancer, we screened the transcriptome using RNA-seq and compared the gene expression profiles between the MCF-7 mamma carcinoma cell line and the TAM-resistant cell line TAMR/MCF-7, 52 significant differential expression genes (DEGs) were identified including SLIT2, ROBO, LHX, KLF, VEGFC, BAMBI, LAMA1, FLT4, PNMT, DHRS2, MAOA and ALDH. The DEGs were annotated in the GO, COG and KEGG databases. Annotation of the function of the DEGs in the KEGG database revealed the top three pathways enriched with the most DEGs, including pathways in cancer, the PI3K-AKT pathway, and focal adhesion. Then we compared the gene expression profiles between the Clinical progressive disease (PD) and the complete response (CR) from the cancer genome altas (TCGA). 10 common DEGs were identified through combining the clinical and cellular analysis results. Protein-protein interaction network was applied to analyze the association of ER signal pathway with the 10 DEGs. 3 significant genes (GFRA3, NPY1R and PTPRN2) were closely related to ER related pathway. These significant DEGs regulated many biological activities such as cell proliferation and survival, motility and migration, and tumor cell invasion. The interactions between these DEGs and drug resistance phenomenon need to be further elucidated at a functional level in further studies. Based on our findings, we believed that these DEGs could be therapeutic targets, which can be explored to develop new treatment options.

Hypoxic 3D in vitro culture models reveal distinct resistance processes to TKIs in renal cancer cells

BackgroundThe aim of this study is to determine the effect of hypoxia on axitinib and sorafenib-treated renal cell carcinoma (RCC) cells. Hypoxia is a crucial factor influencing transcription process via protein modulation, which was shown i.e. in pancreatic cancer. Until now, hypoxia has been defined as associated with poorer outcome and inducing chemotherapy resistance in solid tumors. The unique phenomenon of pseudo-hypoxia connected with vhl mutation was observed in clear-cell, but not in papillary RCC, and the treatment of this subtype of cancer is still challenging. Despite the introduction of new antiangiogenic targeted therapies (inter alia tyrosine kinase inhibitors, TKIs), patients still develop both primary and acquired resistance. Overcoming resistance to TKIs, also in papillary RCC, may be possible by finding significantly modified protein expression. To do this, hypoxic 3D in vitro models must be developed to mimic both molecular pathways typical for low oxygen tension and cell–cell dynamics in tumor-like spatial structures.ResultsClear-cell and papillary renal cell carcinoma (cc and pRCC) cell lines were used in the study to determine the impact of hypoxia on primary drug resistance phenomenon previously observed in papillary, but not in ccRCC. Resistance was confirmed in monolayer culture and in 3D models in soft agar and suspension culture. Human papillary kidney cancer stem-like cells (HKCSCs) cultured in hypoxia developed resistance to sorafenib, while when cultured in normoxia resistance to axitinib has developed. Flow cytometry revealed that hypoxia decreased proliferation rates in all investigated RCC cells. In HKCSCs, there was an increase of quiescent cells (Ki67−) and percentage of cells arrested in S phase. It also appeared that map2k1 and eif4b protein expression is altered in papillary RCC resistant to tested drugs at different oxygen tensions. Also, HKCSCs did not express vegfr-1, braf nor c-kit, TKIs target receptors, which were present in ccRCC cells sensitive to TKI treatment.ConclusionsThe results confirm that low oxygen tension affects RCC cells. Hypoxia facilitates induction of sorafenib resistance in pRCC and induces map2k1 overexpression, while normoxic axitinib-resistant cells up-regulated eif4b. Further studies may determine if map2k1 or eif4b proteins play a role in pRCC resistance to TKIs. It is also of interest to establish if other than vegfr-1, braf, c-kit receptors can serve as potential molecular targets for more effective anti-RCC strategies.

Modulators of the Efflux Pump Cdr1p of Candida albicans: Mechanisms of Action and Chemical Features.

The multicomponent primary active ATP-binding cassette transporter Cdr1p in the structure of the pathogenic yeast Candida albicans is among the culprits of antifungal agent resistance reported in recent decades. So far, various potential novel inhibitors/ modulators of this protein have been purified, synthesized, and biologically tested, with results showing their ability to effectively reverse CaCdr1p-mediated drug resistance phenomenon. These compounds are of diverse origins, possess non-identical structural features and adopt different mechanisms of action. A structured search of chemical features and mechanisms of studied modulators of CaCdr1p was carried out using both original research publications and review articles. The nature of possible inhibitory mechanisms against the pump was analyzed in relation to the structure and the activity of the transporter. A process of summarizing modulatory spectra of the listed compounds against 2 other efflux pumps of Candida albicans namely Cdr2p and Mdr1p was also conducted, during which selective inhibitors of Cdr1p were revealed. In this article, 6 possible mechanisms with which a molecule can manifest their activity against the efflux pump are described, and a list of nearly 50 CaCdr1p modulators found in literatures along with their respective mechanism(s) (if already identified) is provided, summarizing the results obtained so far in the search of new inhibitors of the drug extrusion transporter that can enhance the potency of commonly used antifungal agents. A table of inhibitory spectra of the listed compounds against Cdr1p, Cdr2p and Mdr1p is also given, with several selective modulators of Cdr1p finally indicated. The findings of this review contribute to future studies regarding CaCdr1p and its modulators by summarizing the results obtained so far on this emerging issue of health sciences. Further research concerning novel compounds capable of inhibiting Cdr1p needs to be carried out in hopes of completing the lists provided in this article.

Abstract 5147: Novel warheads for targeted therapies of cancer: The concept and design of proPBDs

Abstract Pyrrolo[2,1-c][1,4]benzodiazepine (PBD) antibiotics, are a class of natural products produced by various actinomycetes bacteria. PBDs are sequence selective DNA-crosslinking alkylating compounds and are considerably more potent than systemic chemotherapeutic agents. Some PBDs have the ability to recognize and bond to specific sequences of DNA. After insertion in the minor groove, a covalent aminal bond is formed through nucleophilic attack of the N-2 of a guanine (G) base on the electrophillic C-11 imine of PBD. The end result is obstruction of tumor cell division without any significant distortion of the DNA’s helix, thus potentially avoiding the common phenomenon of drug resistance. In recent years, synthetic PBD-dimers have emerged as a promising class of payloads for conjugates in the field of targeted cancer therapies. Unfortunately, many PBD conjugates preserve the strongly alkylating imine moiety within their structural framework, which can react in a deleterious manner while in circulation on their way to their intended targets. As an elegant solution to this inherent problem we designed conjugated prodrugs lacking the imine moiety. Once the prodrug (proPBD) conjugate enters a targeted cell, cleavage of the linker system in the construct triggers the generation of a reactive intermediate possessing an aldehyde and aromatic amine. An intramolecular reaction subsequently takes place as the aromatic amine adds to the aldehyde with the loss of water to give the imine, and as a result, the diazepine ring. In our proPBDs, we envision to mask the aldehyde as a hydrolytically sensitive oxazolidine moiety and to exploit its ring system as a part of an arsenal of self-immolative linker systems for conjugation. To prove the range of applications for this new class of latent DNA-alkylators, we designed and prepared a diverse variety of novel warheads, consisting of proPBD dimers, hybrids of proPBD with other powerful alkylating agents, as well as tethers of proPBDs with sequence-selective DNA minor groove binders. The utility of the so prepared novel warheads in the design of small molecule drug conjugates (SMDC) for targeted cancer therapies will be also discussed in the presented poster. Citation Format: Iontcho Vlahov, Longwu Qi, Spencer Hahn, Kevin Wang, Hari K. Santhapuram, Albert Felten, Paul Kleindl, Jeremy Vaughn, Christopher P. Leamon. Novel warheads for targeted therapies of cancer: The concept and design of proPBDs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5147. doi:10.1158/1538-7445.AM2017-5147

Epidemiology of odontogenic infections in a secondary healthcare centre in Southern Nigeria

Association of odontogenic infections with several systemic diseases is of public health importance in Nigeria. This study aimed at determining the epidemiological and microbiological profiles of odontogenic infections and it aetiologic agents in dental patients in Benin City metropolis. Surface and deep socket swabs were collected from each patient before and after tooth extraction and processed for aerobic bacteria. Antimicrobial susceptibility test was carried out on each isolate using standard microbiological methods. Demographics of patients were collected with standard data recording format. Patients aged 20-29 years were more predisposed to odontogenic infections, predominantly peridontitis (51.5%) followed by caries (18.6%) and irreversible pulpitis (9.3%). Teeth in the right lower quadrant of the mouth were most frequently excised in both sexes. Predominant isolates were: β-haemolytic Streptococci (34%), Enterococci (20.6%), Corynebacteria (11.9%), Staphylococci (9.3%), γ-haemolytic Streptococci (5.2%), Neisseria (1.5%), Bacillus (1%), and α-haemolytic Streptococci (0.5%). There was low level of susceptibility of isolates to amoxicillin 30% and high level of susceptibility to perfloxacin (80%). A total of 19.1% of isolates were resistant to the five classes of antibiotics, indicative of multiple drug resistance (MDR) phenomenon. Our study has shown that, treatment of odontogenic infection in the study centre must change and be guided by antimicrobial susceptibility test result to ensure rational use of available antimicrobials.Keywords: Odontogenic infections; Antimicrobial activity; Epidemiological profile; Isolates

New onset of fever and lymphadenopathy in a patient on antitubercular treatment for tuberculous meningitis: Drug resistance or paradoxical response phenomenon?

Central nervous system (CNS) involvement is one of the most devastating clinical manifestations of tuberculosis (TB) noted in 5 to 10% of patients with extra pulmonary TB and accounts for approximately 1% of all patients with TB. Clinical deterioration during treatment with anti-tuberculosis drugs (ATD) is not uncommon in immunocompetent persons. Possibilities include multi-drug resistant tuberculosis (MDR-TB), a paradoxical response or some other non-tubercularcauses of fever. Corticosteroids are considered tohave a beneficial effect in the management of paradoxical reactions. Immuno-modulatory drugs, including tumour necrosis factor-α antagonists, thalidomide and interferon-γ have beenused in isolated cases with more severe forms of paradoxical reactions.We report here a case of a 13 year old girl who while being treated for tubercular meningitis, developed high grade fever with lymphadenopathy. Her lymph node biopsy showed caseous necrosis with presence of AFB suggestive of a paradoxical reaction.

Mechanism of Action: How Nano-Antimicrobials Act?

Escalating resistance to almost every class of antibiotics is reducing the utility of currently available antimicrobial drugs. A part of this menace is attributed to poor pharmacokinetics and pharmacodynamics of the drug. Improvement in drug delivery is the most challenging task encountered by the pharmaceutical industries; however nanotechnology can bring a revolution in drug delivery design. Nano-antimicrobials (NAMs) have their own intrinsic antimicrobial activity (nanoparticles) or augment overall efficacy of enclosed antibiotics (nano-carriers), thus contribute in mitigating or reversing the resistance phenomenon. Nano-particles (NPs) having their own intrinsic antimicrobial activity kill microbes by mimicking natural course of killing by phagocytic cells i.e., by producing large quantity of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS). It is believed that NPs kill microbes by simultaneously acting on many essential life processes or metabolic routes of microbes; that as many genetic mutations to develop resistance against them seems to be impossible. Nano carriers improve the pharmacokinetics of the enclosed drug. Moreover, one of the major techniques by which NAMs can overcome resistance is targeted drug delivery to the site of disease. In this review, a comprehensive detail about the mechanism of action of NAMs are presented in context to multi drug resistance phenomenon.

Intercellular Communication between Malaria-Infected Erythrocytes in the Accelerated Multidrug Resistance Phenotype of the Plasmodium falciparum Parasite

The so-called ARMD (‘accelerated resistance to multidrug’) phenotype of the human malaria parasite Plasmodium falciparum that is prevalent in South East Asia is believed to confer a special hypermutator characteristic upon parasite strains in which it is expressed. Examination of the ARMD phenotype suggests that alternative mechanisms may be responsible for this ability that is unique among strains of P. falciparum parasite worldwide, but over which there is concern that further dissemination may lead to widespread loss of sensitivity to current chemotherapeutic regimens. Therefore, other recently discovered mechanisms that demonstrate potential in contributing to this noted drug resistance phenomenon merit further investigation. One important example, the cell-to-cell communication pathway in P. falciparum-infected erythrocytes, is being examined as a potential target for intervention and forms the subject of this article.

The evaluation of the classical Kirby-Bauer antibiogram method for the determination of antibiotic resistant microorganisms in tap water

Water supply systems are the main source of potable water for many inhabitants. The European Union and Polish laws demand high quality of tap water, but the aspect of antibiotic resistant bacteria (ARB) is not mentioned. The special emphasis is placed on the presence of pathogenic microorganisms in water, determining by the presence of chosen indicators. Although these regulations provide quite good quality of drinking water, the neglect of resistance vectors could lead to a serious threat to human health. In this study the randomly chosen sample of water from the Wroclaw water supply system was tested in order to evaluate the usefulness of Kirby-Bauer antibiogram method for the assessment of the presence of ARB. The susceptibility testing with 6 chosen antibiotics was performed on bacterial strains isolated from the sample. The diameters of growth inhibition zones were measured and the preliminary identification of strains was carried out, including Gram staining and bacterial cellular morphologies assessments. Although full recognition of the drug resistance phenomenon demands the identification of bacterial species for the comparison with susceptibility testing guidelines, this preliminary research could answer the question, whether the Kirby-Bauer method is sufficient for investigations of ARB dwelling in Wroclaw tap water or the other solution should be applied.