Study on genes for cross-resistance to isoniazid and ethionamidein Mycobacterium tuberculosis / 预防医学

Objective@#To examine the association between the cross-resistance to ethionamide (Eto) and isoniazid (INH) and mutations of drug resistant genes in Mycobacterium tuberculosis (MTB), so as to provide the evidence for clinical diagnosis and treatment for multidrug-resistant (MDR) tuberculosis.@*Methods@#Totally 126 MTB clinical isolates were selected, including 88 MDR-MTB clinical isolates and 38 INH- and rifampicin (RFP)-sensitive isolates. The resistance to INH and Eto was tested in MTB clinical isolates using the drug susceptibility test, and the mutations in the spacer region of INH and Eto resistance-related katG, inhA, ethA, mshA, ndh, spacer region of oxyR-ahpC and inhA promoter were detected using PCR assay. The phenotypic resistance served as a gold standard, and the sensitivity, specificity and accuracy of gene mutation tests were calculated for detection of MTB clinical isolates cross-resistant to INH and Eto.@*Results@#Of the 126 MTB clinical isolates, there were 37 isolates cross-resistant to INH and Eto (29.37%), 51 isolates with resistance to INH and susceptibility to Eto (40.48%), 4 isolates with susceptibility to INH and resistance to Eto (3.17%) and 34 isolates with susceptibility to INH and Eto (26.98%). Among the 41 Eto-resistant MTB clinical isolates, there were 37 isolates with resistance to INH (90.24%). There were 64 MTB clinical isolates detected with katG mutations (50.79%), 4 isolates with mutation in the spacer region of oxyR-ahpC (3.17%), 2 isolates with inhA mutations (1.59%), and these isolates were all resistant to INH. There were 11 MTB clinical isolates detected with mutation in the inhA promoter (8.73%) and one isolate with ndh mutation, and all these isolates were cross-resistant to INH and Eto. There were 23 MTB clinical isolates detected with ethA mutations (18.25%) and 40 isolates with mshA mutations (31.75%), in which Eto-susceptible and -resistant isolates were detected. The diagnostic sensitivity, specificity and accuracy of inhA promoter tests for detection of cross-resistance to INH and Eto were 29.73% (95%CI: 16.44%-47.17%), 100.00% (95%CI: 87.36%-100.00%) and 63.38% (95%CI: 51.76%-73.63%) in MTB clinical isolates.@*Conclusions@#The prevalence of INH resistance is high in Eto-resistant MTB clinical isolates. Mutation in the inhA promoter region correlates with the cross-resistance to INH and Eto in MTB clinical isolates, and detection of mutation in the inhA promoter may be feasible to detect the cross-resistance to INH and Eto in MTB clinical isolates.

Resistencia cruzada entre isoniacida y etionamida y su alta correlación con la mutación C-15T en aislamientos de Mycobacterium tuberculosis de Perú / Cross-resistance between isoniazid and ethionamide and its strong association with mutation C-15T in Mycobacterium tuberculosis isolates from Peru

Resumen Diversos estudios han evidenciado una resistencia cruzada entre isoniacida y etionamida, 2 de los fármacos utilizados en el tratamiento de la tuberculosis multirresistente.El objetivo del presente estudio fue determinar la resistencia cruzada entre ambos fármacos en aislados de Mycobacterium tuberculosis obtenidos en un hospital de Lima (Perú), conalta proporción de pacientes con tuberculosis. Se calculó la frecuencia de mutaciones asociadas con la resistencia a la isoniacida (INH) evaluando el gen katG y la región promotorainhA mediante la prueba molecular Genotype MTBDRplus v2.0. El método gold standard conocido como agar proporciones en placa (APP) permitió la identificación de resistencia a INH yetionamida. De 107 aislamientos resistentes a INH, 54 fueron multirresistentes (identificadosmediante la prueba Genotype MTBDRplus) y 49 (es decir, el 45,8% del total) también fueronresistentes a etionamida por el método APP. En los aislamientos resistentes a INH, se encontraron mutaciones en el gen katG en el 50,5% (54/107); en la región promotora inhA en el23,3% (25/107), y un 14,0% (15/107) presentaron mutaciones en ambos. Un 12,1% (13/107)fueron resistentes a INH por ausencia de banda wild type y banda de mutación. La mutaciónC-15T en la región promotora inhA presentó una fuerte asociación con la resistencia a etionamida y alcanzó el 73,4% (36/49) de los aislamientos resistentes a dicho fármaco. Los resultadosdel presente estudio sugieren que la identificación de mutaciones relacionadas con resistenciaa INH, sobre todo en la región promotora inhA, podría ser de gran utilidad para identificarla resistencia cruzada a etionamida y mejorar el tratamiento de las personas afectadas portuberculosis.© 2019 Asociacion Argentina de Microbiolog´ía. Publicado por Elsevier Espana, S.L.U. Este es unart´ículo Open Access bajo la licencia CC BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/).

Abstract Several studies have shown cross-resistance between isoniazid and ethionamide, 2of the drugs used in the treatment of multidrug-resistant tuberculosis. The objective of this study was to determine the cross-resistance between both drugs in Mycobacterium tuberculosis isolates from a hospital with high incidence of tuberculosis in Lima, Peru. The frequency of mutations to isoniazid in the katG gene and the inhA promoter region was identified by the Genotype MTBDRplus v2.0 molecular test. The gold standard Agar Proportion method (APM) allowed todetect resistance to isoniazid and ethionamide. Of 107 isoniazid-resistant isolates (54 multidrug-resistant isolates identified by the Genotype MTBDRplus test, 45.8% (49/107) were also resistant to ethionamide by the APM. Mutations were found in the katG gene in 50.5% (54/107), in the promoter region inhA in 23.3% (25/107) and 14.0% (15/107) that share both mutations in the resistant isolates to INH. The absence of the wild type and mutation bands indicated that 12.1% (13/107) of the isolates were resistant to INH. The mutation C-15T in the inhA promoter region showed a strong association with resistance to ethionamide in 73.4% (36/49) of the isolates analyzed. The results of the present study suggest that the identification of mutations related to resistance to isoniazid, especially in the inhA promoter region, could be very useful to identify cross-resistance to ethionamide and improve the treatment of individuals suffering from this disease.

Multidrug-resistant Candida glabrata strains obtained by induction of anidulafungin resistance in planktonic and biofilm cells

Candida glabrata has emerged as a common cause of serious life-threatening fungal infections, largely owing to their low susceptibility to azole antifungals. Recent guidance indicates the use of echinocandins as the first-choice drug for the treatment of systemic infections of C. glabrata; however, C. glabrata resistance to echinocandins is reportedly increasing. Herein, we present the induction of anidulafungin resistance in planktonic and sessile cells of C. glabrata and the development of fluconazole cross-resistance. MICs of 21 clinical C. glabrata strains were determined by a broth microdilution method using anidulafungin and fluconazole. Biofilm formation on a tracheal catheter was determined using 1- × 1-cm2 polyvinyl polychloride catheter fragments. Induction of anidulafungin resistance in planktonic and sessile cells and evaluation of its stability were performed by exposing the strains to successively higher concentrations of the antifungal. The induction resulted in strains strongly resistant to anidulafungin (MICs: 1-2 µg/mL) and fluconazole (≥64 µg/mL). Most of the sessile cells of C. glabrata presented slightly reduced susceptibility compared with the planktonic cells. Clinically, this cross-resistance could lead to therapeutic failure while using fluconazole in patients previously exposed to subinhibitory concentrations of anidulafungin for extended periods.

Is the emergence of fungal resistance to medical triazoles related to their use in the agroecosystems? A mini review

Abstract Triazole fungicides are used broadly for the control of infectious diseases of both humans and plants. The surge in resistance to triazoles among pathogenic populations is an emergent issue both in agriculture and medicine. The non-rational use of fungicides with site-specific modes of action, such as the triazoles, may increase the risk of antifungal resistance development. In the medical field, the surge of resistant fungal isolates has been related to the intensive and recurrent therapeutic use of a limited number of triazoles for the treatment and prophylaxis of many mycoses. Similarities in the mode of action of triazole fungicides used in these two fields may lead to cross-resistance, thus expanding the spectrum of resistance to multiple fungicides and contributing to the perpetuation of resistant strains in the environment. The emergence of fungicide-resistant isolates of human pathogens has been related to the exposure to fungicides used in agroecosystems. Examples include species of cosmopolitan occurrence, such as Fusarium and Aspergillus, which cause diseases in both plants and humans. This review summarizes the information about the most important triazole fungicides that are largely used in human clinical therapy and agriculture. We aim to discuss the issues related to fungicide resistance and the recommended strategies for preventing the emergence of triazole-resistant fungal populations capable of spreading across environments.

Piper aduncum against Haemonchus contortus isolates: cross resistance and the research of natural bioactive compounds / Piper aduncum contra isolados de Haemonchus contortus: resistência cruzada e a pesquisa de bioativos naturais

Abstract The anthelminthic activity of the essential oil (EO) of Piper aduncum L. was tested in vitro on eggs and larvae of resistant (Embrapa2010) and susceptible (McMaster) isolates of Haemonchus contortus. The EO was obtained by steam distillation and its components identified by chromatography. EO concentrations of 12.5 to 0.02 mg/mL were used in the egg hatch test (EHT) and concentrations of 3.12 to 0.01 mg/mL in the larval development test (LDT). Inhibition concentrations (IC) were determined by the SAS Probit procedure, and significant differences assessed by ANOVA followed by Tukey’s test. In the EHT, the IC50 for the susceptible isolate was 5.72 mg/mL. In the LDT, the IC50 and IC90 were, respectively, 0.10 mg/mL and 0.34 mg/mL for the susceptible isolate, and 0.22 mg/mL and 0.51 mg/mL for the resistant isolate. The EO (dillapiole 76.2%) was highly efficacious on phase L1. Due to the higher ICs obtained for the resistant isolate, it was raised the hypothesis that dillapiole may have a mechanism of action that resembles those of other anthelmintic compounds. We further review and discuss studies, especially those conducted in Brazil, that quantified the major constituents of P. aduncum-derived EO.

Resumo Este estudo avaliou a atividade anti-helmíntica in vitro do óleo essencial (OE) de Piper aduncum L. sobre ovos e larvas de Haemonchus contortus, verificando se um isolado resistente (Embrapa2010), apresentaria o mesmo comportamento que um sensível (McMaster). O OE foi obtido por arraste a vapor e analisado por cromatografia para identificação dos constituintes. O óleo foi avaliado nas concentrações de 12,5 a 0,02 mg/mL no Teste de eclosão dos ovos (TEO) e nas concentrações de 3,12 a 0,01 mg/mL no Teste de desenvolvimento larvar (TDL). As concentrações inibitórias (CI) foram determinadas pelo procedimento Probit do SAS e as diferenças estatísticas geradas pela ANOVA seguida pelo teste de Tukey. Para o isolado sensível obteve-se CI50 de 5,72 mg/mL no TEO. No TDL o óleo apresentou CI50 e CI90 de 0,10 mg/mL e 0,34 mg/mL para o isolado sensível e 0,22 mg/mL e 0,51 mg/mL para o resistente, respectivamente. Demonstrou-se que o OE (dilapiol 76,2%) teve alta eficácia sobre a fase L1. Devido às elevadas CIs obtidas para o isolado resistente, levantou-se a hipótese de que o dilapiol talvez possua um mecanismo de ação semelhante a algum grupo anti-helmíntico. O artigo faz uma revisão e discute estudos de quantificação dos constituintes majoritários do OE de P. aduncum, destacando os realizados no Brasil.

Acid and low temperature treatments on Salmonella Enteritidis inoculated in pork and its subsequent survival in simulated gastric fluid / Ácido e baixas temperaturas sobre Salmonella Enteritidis inoculada em carne suína e sua sobrevivência subsequente ao fluido gástrico simulado

ABSTRACT: The objective of this study was to evaluate the acid resistance of Salmonella enterica serovar Enteritidis (S. Enteritidis) in stored pork and in simulated gastric fluid (SGF). A culture of S. Enteritidis was subjected to acid treatment prior to inoculation into pork, stored under refrigeration at frozen temperatures and exposed to SGF. The S. Enteritidis CCS3 and ATCC 13076 strains previously subjected to acid treatment (at pH 4.0-5.0) were inoculated in pork and stored at 4°C and -18°C. Storage at 4ºC did not affect the populations of both S. Enteritidis strains. After 84 days at -18°C, the mean population of both CCS3 and ATCC strains were reduced by 0.8 and 1.5 log cycles, respectively. Prior acid treatment did not enhance the survival of both strains at low temperatures. After acid treatment and low temperature storage, S. Enteritidis ATCC 13076 lost culturability after being exposed to SGF for 10 minutes. In contrast, S. Enteritidis CCS3 was tolerant until three hours of SGF exposure. S. Enteritidis CCS3 submitted to pH 4.0 was more tolerant to SGF exposure than when submitted to pH 4.5, 5.0 and without acid treatment. Therefore, this study indicates that exposure to an acidic and cold environment during processing enhanced the ability of S. Enteritidis to survive in the gastric environment of the human stomach, possibly increasing the risk of a Salmonella infection after consumption of pork.

RESUMO: O objetivo deste estudo foi avaliar a resistência ao ácido de Salmonella enterica serovar Enteritidis (S. Enteritidis) previamente submetidas a tratamento ácido e inoculadas em carne suína armazenada em temperaturas de refrigeração e congelamento ao fluido gástrico simulado (FGS). As linhagens de S. Enteritidis CCS3 and ATCC 13076 previamente submetidas a tratamento ácido variando de pH 4.0 a 5.0 foram inoculadas em carne de porco e armazenadas a 4 e −18°C. A estocagem por sete dias a 4°C não afetou as populações das duas linhagens de S. Enteritidis. Após 84 dias a -18°C, as reduções médias das populações das linhagens foram de 0,8 e 1,5 ciclos logarítmicos, respectivamente. O tratamento ácido prévio não aumentou a sobrevivência das duas culturas sob baixas temperaturas. Após tratamento ácido e estocagem em temperaturas baixas, S. Enteritidis ATCC 13076 perdeu a culturabilidade após 10 minutos de desafio ao FGS. Contrariamente, S. Enteritidis CCS3 mostrou-se tolerante à exposição por três horas ao FGS. S. Enteritidis CCS3 submetidas a tratamento ácido prévio em pH 4,0 mostraram-se mais tolerantes à exposição por 180 minutos ao FGS que células submetidas aos tratamentos ácidos em pH 4,5 e 5,0 e células sem tratamento. Portanto, este estudo indica que S. Enteritidis submetida a um ambiente ácido e frio durante o processamento pode melhorar a sua capacidade de sobreviver à barreira gástrica em humanos, possivelmente, aumentando o risco de surto por Salmonella após consumo de carne de porco.

Caracterização molecular e perfil de suscetibilidade de Cryptococcus e outras leveduras melanizadas de ambiente contaminado com fungicidas azólicos

Cepas fúngicas ambientais estão sujeitas, continuamente, à grande diversidade de ações antrópicas, como a exposição a f u n g i c i d a, o que poderia induzir à resistência adquirida a fármacos antifúngicos com estrutura química e mecanismo de ação semelhante. A resistência adquirida a fármacos azólicos(fluconazol, itraconazol, v o r i c o n a z o l, etc.) tem importante implicação clínica.O objetivo deste estudo foi isolar e caracterizar leveduras melanizadas de origem ambiental, do gênero Cryptococcus e do grupo Black Yeast Fungi (BYF),e determinar seu perfil de sensibilidade a fármacos e fungicidas azólicos...

Environmental fungal strains are subject continuously to the wide range of humanactivities, such as exposure to fungicide, which could lead to acquired resistance to antifungal drugs with similar chemical structure and mechanism of action. Theacquired resistance to azole drugs (fluconazole, itraconazole, voriconazole, etc.)has important clinical implications. The aim of this study was to isolate and characterize melanized yeast environmental origin, gender Cryptococcus and Black Yeast Fungi group (BYF), and determine its susceptibility profile to drugs and azole fungicides...

Experimental study on cross-resistance of Culex pipiens pallens to 3 kinds of chemical pesticides / 中国血吸虫病防治杂志

Objective To understand the cross-resistance of Culex pipiens pallens to common pesticides,so as to provide the evidence for improving the application of chemical pesticides. Methods The IV instar larvae of DDVP-resistant,propoxur-resistant and cypermethrin-resistant strains as well as the sensitive strain of Culex pipiens pallens were collected to detect the re-sistance to DDVP,propoxur and cypermethrin based on the WHO bioassay method. Results The resistance coefficients of DDVP-resistant strain to DDVP,propoxur and cypermethrin were 14.47,8.96 and 207.27 respectively. The resistance coeffi-cients of propoxur-resistant strain to DDVP,propoxur and cypermethrin were 3.27,6.93 and 8.65 respectively. The resistance coefficients of cypermethrin-resistant strain to DDVP,propoxur and cypermethrin were 2.93,1.61 and 501.11 respectively. Con-clusion The resistance and cross-resistance could be generated during the long-term application of a single kind of chemical pesticide,and we should pay more attention to the varieties and dosages of them.

Antibacterial efficacy of Nisin, Pediocin 34 and Enterocin FH99 against Listeria monocytogenes and cross resistance of its bacteriocin resistant variants to common food preservatives

Antilisterial efficiency of three bacteriocins, viz, Nisin, Pediocin 34 and Enterocin FH99 was tested individually and in combination against Listeria mononcytogenes ATCC 53135. A greater antibacterial effect was observed when the bacteriocins were combined in pairs, indicating that the use of more than one LAB bacteriocin in combination have a higher antibacterial action than when used individually. Variants of Listeria monocytogenes ATCC 53135 resistant to Nisin, Pediocin 34 and Enterocin FH99 were developed. Bacteriocin cross-resistance of wild type and their corresponding resistant variants were assessed and results showed that resistance to a bacteriocin may extend to other bacteriocins within the same class. Resistance to Pediocin 34 conferred cross resistance to Enterocin FH 99 but not to Nisin. Similarly resistance to Enterocin FH99 conferred cross resistance to Pediocin 34 but not to Nisin. Also, the sensitivity of Nisin, Pediocin 34 and Enterocin FH99 resistant variants of Listeria monocytogenes to low pH, salt, sodium nitrite, and potassium sorbate was assayed in broth and compared to the parental wild-type strain. The Nisin, Pediocin 34 and Enterocin FH99 resistant variants did not have intrinsic resistance to low pH, sodium chloride, potassium sorbate, or sodium nitrite. In no case were the bacteriocin resistant Listeria monocytogenes variants examined were more resistant to inhibitors than the parental strains.

The efficacy of a chitin synthesis inhibitor against field populations of organophosphate-resistant Aedes aegypti in Brazil

The mosquito Aedes aegypti is the main focus of dengue control campaigns. Because of widespread resistance against conventional chemical insecticides, chitin synthesis inhibitors (CSIs) are considered control alternatives. We evaluated the resistance status of four Brazilian Ae. aegypti populations to both the organophosphate temephos and the pyrethroid deltamethrin, which are used in Brazil to control larvae and adults, respectively. All vector populations exhibited high levels of temephos resistance and varying rates of alterations in their susceptibility to pyrethroids. The effect of the CSI novaluron on these populations was also investigated. Novaluron was effective against all populations under laboratory conditions. Field-simulated assays with partial water replacement were conducted to evaluate novaluron persistence. Bioassays were continued until an adult emergence inhibition of at least 70% was attained. We found a residual effect of eight weeks under indoor conditions and novaluron persisted for five-six weeks in assays conducted in an external area. Our data show that novaluron is effective against the Ae. aegypti populations tested, regardless of their resistance to conventional chemical insecticides.

The analysis of quinolone resistance of the avian Escherichia coli and Salmonella isolates from 1993 to 2008 / 中国人兽共患病学报

Quinolones are broad-spectrum antibacterial agents used in human and veterinary medicine, and their extensive use have been associated with a rise of the quinolone resistance. In the present study, the quinolone resistance of avian E.coli and Salmonella isolates was evaluated and compared, in which 344 avian E.coli and 224 Salmonella isolates from 1990s were serogrouped with antisera and thc antimicrobial susceptibility test to 10 quinolones was carried out by using the Kirby-Bauer method recommended by Clinical and Laboratory Standards Institute (CLSI). It was demonstrated that the 344 isolates of avian E.coli distributed in 27 serogroups and 68.90% (237/344) of the isolates belonged to four O-serogroups: i.e. O1, O2, O18, O78, and the 224 isolates of avian Salmonella were all determined to be Salmonella pullorum. The drug-resistance rate of avian E. coli isolates to nalicixic acid from 1993-1999 was more than 60%(64.43%,131/181), whereas those of isolates to 9 antibiotics from 2000-2008 had a drug-resistance rates of more than 60%, namely,nalicixic acid(92.02%), fleroxacin(79.75%), pipemidic acid(79.14%), enrofloxacin(78.53%), enoxacin(76.07%), lomenfloxacin(74.85%), ciprofloxacin(69.33%), norfloxacin(63.80%) and ofloxacin(61.35%). For the 4 O-serogroups of the avian E.coli isolates, the drug-resistance rates of more than 50% to antimicrobials were as follows: O78 isolates to 7 antimicrobials;O18 isolates to 5 antimicrobials, and O1 and O2 isolates just to 3 antimicrobials. The quinolone resistance of Salmonella isolates was much lower than E.coli, in which 101 salmonella isolates from 1993-1999 were all susceptible to quinolones. Nalicixic acid resistance of salmonella isolate firstly appeared in 2000, and the drug-resistance rate of salmonella isolates from 2000-2008 was found to be more than 60% for nalicixic acid(83.74%), but those to other quinolones were comparatively lower. These results indicated that the quinolone resistance of avian E.coli and salmonella were increasing in the past two decads because of the over-use of antibiotics.

Cross-resistance Between Rifampicin and Rifabutin and Its Relationship with rpoB Gene Mutations in Clinically Isolated MDR-TB Strains / 결핵및호흡기질환

BACKGROUND: Despite the emerging danger of MDR-TB to human beings, there have only been a limited number of drugs developed to treat MDR-TB since 1970. This study investigated the cross-resistance rate between rifampicin (RFP) and rifabutin (RBU) in order to determine the efficacy of rifabutin in treating MDR-TB. In addition, the results of rifabutin were correlated with the rpoB mutations, which are believed to be markers for MDR-TB and RFP resistance. METHODS: The MICs of RBU were tested against 126 clinical isolates of MDR-TB submitted to the clinical laboratory of National Masan TB Hospital in 2004. Five different concentrations (10-160 microgram/ml) were used for the MICs. The detection of the rpoB mutations was performed using a RFP resistance detection kit with a line probe assay(LiPA), which contains the oligonucleotide probes for 5 wide type and 3 specific mutations (513CCA, 516GTC, and 531TTG). The rpoB mutation was determined by direct sequencing. RESULTS: The rate of cross-resistance between RFP and RBU was 70.5%(74/105) at 20 microgram/ml RBU(ed note: How much RFP?) Most mutations (86.3%) occurred in the 524~534 codons. The His526Gln, His526Leu, Leu533Pro, Gln513Glu, and Leu511Pro mutations(Ed note: Is this correct?) were associated with the susceptibilty to RBU. CONCLUSION: Based on the cross-resistance rate between RFP and RBU, RBU may be used effectively in some MDR-TB patients. Therefore, a conventional drug susceptibility test for RBU and a determination of the critical concentration are needed. However, rpoB gene mutation test may be have limited clinical applications in detecting RBU resistance.

Cross Resistance of Fluoroquinolone Drugs on gyrA Gene Mutation in Mycobacterium tuberculosis / 결핵및호흡기질환

BACKGROUND: Fluoroquinolone drugs are an important anti-tuberculous agent for the treatment of multi-drug resistant tuberculosis. However, many drugs belonging to the fluoroquinolones have different cross resistance to each other. METHODS: Sixty-three ofloxacin (OFX) resistant and 10 pan-susceptible M. tuberculosis isolates were selected, and compared for their cross resistance using a proportion method on Lowenstein-Jensen media, containing ofloxacin (OFX), ciprofloxacin (CIP), levofloxacin (LVX), moxifloxacin (MXF), gatifloxacin (GAT) and sparfloxacin (SPX), at concentrations ranging from 0.5 to 3microgram/ml. DNA extracted from the isolates was directly sequenced after amplifying from the gyrA and gyrB genes. RESULTS: The 63 OFX resistant M. tuberculosis isolates showed complete cross resistance to CIP, but only 90.5, 44.4, 36.5 and 46.0% to LVX, MXF, GAT, and to SPX, respectively. Fifty-one of the isolates (81.0%) had point mutations in codons 88, 90, 91 and 94 in gyrA, which are known to be correlated with OFX resistance. The Gly88Ala, Ala90Valand Asp94Ala mutations in gyrA showed a tendency to be susceptible to MXF, GAT and SPX. Only 4 isolates had mutations in the gyrB gene, which did not affect the OFX resistance. CONCLUSION: About 60% of the OFX resistant M. tuberculosis isolates were susceptible to GAT, SPX and MXF. These fluoroquinolones may be useful in the treatment of TB patients showing OFX resistance.

Activity of Moxifloxacin Against Ofloxacin-Resistant Mycobacterium Tuberculosis: A Study of Cross-Resistance Between Ofloxacin and Moxifloxacin / 결핵및호흡기질환

BACKGROUND: Moxifloxacin is an 8-methoxyquinolone compound which has been shown to have the best activity of the quinolones against M. tuberculosis but there is no literature showing the rate of cross-resistance between moxifloxacin and the other quinolones such as ofloxacin. Therefore, we tested the activity of moxifloxacin against ofloxacin resistant M. tuberculosis by a study of cross-resistance. METHODS: We tested MIC's of moxifloxacin and ofloxacin by proportion method against 34 M. tuberculosis isolates showing resistance against ofloxacin at 2.5microgram/ml concentration and 13 ofloxacin susceptible isolates from specimens submitted to clinical laboratory of National Masan Hospital from March 2003 to March 2004. RESULTS: For ofloxacin susceptible isolates, MIC(50) and MIC(90) of ofloxacin were all 1.25 microgram/ml, and MIC(50) and MIC(90) of moxifloxacin were 0.31 microgram/ml and 0.63microgram/ml respectively. For ofloxacin resistant isolates, MIC(50) of ofloxacin was over 10microgram/ml and MIC(50) of moxifloxacin was 5microgram/ml,MIC(90) of ofloxacin and moxifloxacin were all over 10microgram/ml. The rate of cross-resistance between the two was 67.6%(23/34) at 2.5microgram/ml concentration. CONCLUSIONS: Moxifloxacin showed activity against 82.4%(28/34) of ofloxacin resistant M. tuberculosis at 10microgram/ml, but more studies are needed so that moxifloxacin will be used for patient with multi-drug resistant tuberculosis including ofloxacin resistance.

A study of ciprofloxacin and imipenem cross resistance in Pseudomonas aeruginosa induced experimental mouse peritonitis / 中华传染病杂志

Objective To investigate the mechanism of cross resistant inducibility of ciprofloxacin and imipenem which led to cross resistance in Pseudomonas aeruginosa in vivo. Methods Cross resistant mutant strains were selected and induced with clinical isolates of P.aeruginosa PA5 susceptible to ciprofloxacin and imipenem by experiment of murine peritonitis. Mutation of DNA gyrase gene, drug uptake and membrance proteins of P.aeruginosa PA5 and its mutants resistant to ciprofloxacin and imipenem were examined. Results Both ciprofloxacin and imipenem could induce resistant strain of P.aeruginosa in experimental murine peritonitis, the cross resistance rates after ciprofloxacin and imipenem challenge were 3.8% and 0.98% respectively. The results of PCR SSCP showed that 3 of six cross resistant of P.aeruginosa strains had gyrA gene mutation. Electrophoresis of outer and inner membrane proteins did not exist any difference between cross resistant strains and their parent strain PA5. Fluorometric assay for ciprofloxacin uptake by bacterial cells indicated that the accumulation of ciprofloxacin in all cross resistant variants decreased to 1/2～1/3 compared with that of PA5. After chanllenge with CCCP, the drug uptake in cross resistance mutants increased to the same level as in PA5. Conclusions The results show that cross resistant strains of P. aeruginosa could be selected and induced in vivo. Active drug efflux is the major factor contributing to the cross resistance of P. aeruginosa to both quinolone and imipenem.

Establishment of multidrug resistance to adriamycin in Ehrlich ascites carcinoma in vivo / 中国药理学通报

Resistance to adriamycin was developed in an orignally adriamycin- sensitive strain of Ehrlich ascites carcinoma (EAC) in vivo by treament with the adriamycin during 50 weekly passages of the tumor. The results showed that the growth of the resistant line was slower than that of the EAC, total ascites cell volume,total cell number and mean single-cell volume were significantly smaller of the resistant line than those of original sensitive line. Also, itwas found the homogerously staining region and double minute chromosome in the cells of resistant line. The adriamycin-resistant tumor produced cross resistance to vincristine.mitomycin C,and actinomycin D,while section resistance to VP-16. There was no change in the sensitivity of tumor to oridonin.