scholarly journals Experimental Induction of Paromomycin Resistance in Antimony-Resistant Strains of L. donovani: Outcome Dependent on In Vitro Selection Protocol

2012 ◽  
Vol 6 (5) ◽  
pp. e1664 ◽  
Author(s):  
Sarah Hendrickx ◽  
Raquel Andrea Inocêncio da Luz ◽  
Vasundhra Bhandari ◽  
Kristel Kuypers ◽  
Craig D. Shaw ◽  
...  
Keyword(s):  
In Vitro Selection ◽  
Paromomycin Resistance ◽  
Experimental Induction ◽  
Selection Protocol ◽  
Resistant Strains

scholarly journals In Vitro Selection of Resistance to Four β-Lactams and Azithromycin in Streptococcus pneumoniae

1998 ◽  
Vol 42 (11) ◽  
pp. 2914-2918 ◽  
Author(s):  
Glenn A. Pankuch ◽  
Shane A. Jueneman ◽  
Todd A. Davies ◽  
Michael R. Jacobs ◽  
Peter C. Appelbaum
Keyword(s):  
Streptococcus Pneumoniae ◽  
In Vitro Selection ◽  
Antimicrobial Agents ◽  
Penicillin G ◽  
Resistance Selection ◽  
Resistant Strains ◽  
Selection Of ◽  
Selection Of Resistance

ABSTRACT Selection of resistance to amoxicillin (with or without clavulanate), cefaclor, cefuroxime, and azithromycin among six penicillin G- and azithromycin-susceptible pneumococcal strains and among four strains with intermediate penicillin sensitivities (azithromycin MICs, 0.125 to 4 μg/ml) was studied by performing 50 sequential subcultures in medium with sub-MICs of these antimicrobial agents. For only one of the six penicillin-susceptible strains did subculturing in medium with amoxicillin (with or without clavulanate) lead to an increased MIC, with the MIC rising from 0.008 to 0.125 μg/ml. Five of the six penicillin-susceptible strains showed increased azithromycin MICs (0.5 to >256.0 μg/ml) after 17 to 45 subcultures. Subculturing in medium with cefaclor did not affect the cefaclor MICs of three strains but and led to increased cefaclor MICs (from 0.5 to 2.0 to 4.0 μg/ml) for three of the six strains, with MICs of other β-lactams rising 1 to 3 twofold dilutions. Subculturing in cefuroxime led to increased cefuroxime MICs (from 0.03 to 0.06 μg/ml to 0.125 to 0.5 μg/ml) for all six strains without significantly altering the MICs of other β-lactams, except for one strain, which developed an increased cefaclor MIC. Subculturing in azithromycin did not affect β-lactam MICs. Subculturing of the four strains with decreased penicillin susceptibility in amoxicillin (with or without clavulanate) or cefuroxime did not select for β-lactam resistance. Subculturing of one strain in cefaclor led to an increase in MIC from 0.5 to 2.0 μg/ml after 19 passages. In contrast to strains that were initially azithromycin susceptible, which required >10 subcultures for resistance selection, three of four strains with azithromycin MICs of 0.125 to 4.0 μg/ml showed increased MICs after 7 to 13 passages, with the MICs increasing to 16 to 32 μg/ml. All azithromycin-resistant strains were clarithromycin resistant. With the exception of strains that contained mefE at the onset, no strains that developed resistance to azithromycin containedermB or mefE, genes that have been found in macrolide-resistant pneumococci obtained from clinic patients.

scholarly journals Drug Combination of AZT and ddl: Synergism of Action and Prevention of Appearance of AZT-Resistance

1994 ◽  
Vol 5 (1) ◽  
pp. 51-55 ◽  
Author(s):  
G. Antonelli ◽  
F. Dianzani ◽  
D. Bellarosa ◽  
O. Turriziani ◽  
E. Riva ◽  
...  
Keyword(s):  
In Vitro Selection ◽  
Mononuclear Cells ◽  
Peripheral Blood Mononuclear ◽  
Immunodeficiency Virus ◽  
Resistant Strains ◽  
Azt Resistance ◽  
Hiv 1

Both 3′-azido-3′-deoxythymidine (AZT) and 2′,3′-dideoxynosine (ddl) strongly inhibit the replication of human immunodeficiency virus type 1 (HIV-1). Here, it is shown that combination of AZT and ddl at concentrations that are readily achievable in vivo synergistically inhibit HIV-1 replication in C8166 cells and peripheral blood mononuclear cells. The synergism is significant even when the effect of AZT and ddl alone was negligible. Our findings show that AZT-resistance is less likely to occur when a combination of AZT and ddl is used. Particularly, generation of AZT-resistant strains by in vitro selection is prevented, or delayed, by the combination of AZT plus ddl. Taken together these observations provide a rationale for combination of AZT and ddl in the therapy of AIDS patients.

scholarly journals Pre-clinical evaluation of an in vitro selection protocol for the enrichment of transduced CD34+ cell-derived human dendritic cells

Gene Therapy ◽  
2001 ◽  
Vol 8 (18) ◽  
pp. 1427-1435 ◽  
Author(s):  
JT Evans ◽  
P Cravens ◽  
J Gatlin ◽  
PF Kelly ◽  
PE Lipsky ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Clinical Evaluation ◽  
In Vitro Selection ◽  
Selection Protocol ◽  
Human Dendritic Cells

scholarly journals Extended-Spectrum Cephalosporinases in Pseudomonas aeruginosa

2009 ◽  
Vol 53 (5) ◽  
pp. 1766-1771 ◽  
Author(s):  
José-Manuel Rodríguez-Martínez ◽  
Laurent Poirel ◽  
Patrice Nordmann
Keyword(s):  
Pseudomonas Aeruginosa ◽  
In Vitro Selection ◽  
Resistance Mechanism ◽  
Cloning And Sequencing ◽  
Alanine Residue ◽  
Resistant Strains ◽  
Imipenem Resistance ◽  
Selection Of

ABSTRACT The characterization of AmpC-type β-lactamases was performed in a collection of 32 clinical Pseudomonas aeruginosa isolates with intermediate susceptibility or resistance to imipenem and ceftazidime. Twenty-one out of those 32 isolates overexpressed AmpC β-lactamase, and the MICs of ceftazidime and imipenem were reduced after cloxacillin addition. Cloning and sequencing identified 10 AmpC β-lactamase variants. Reduced susceptibility to imipenem, ceftazidime, and cefepime was observed only with recombinant P. aeruginosa strains expressing an AmpC β-lactamase that had an alanine residue at position 105. The catalytic efficiencies (k cat/Km ) of the AmpC variants possessing this residue were increased against oxyiminocephalosporins and imipenem. In addition, we show here that those AmpC variants constitute a favorable background for the in vitro selection of imipenem-resistant strains. This report identified a novel resistance mechanism that may contribute to imipenem resistance in P. aeruginosa.

Mechanisms involved in effects of antimicrobial peptides, bactenectins ChBac3.4, ChBac5, and mini-ChBac7.5Nb, on bacterial cells

2017 ◽  
pp. 43-50
Author(s):  
О.В. Шамова ◽  
М.С. Жаркова ◽  
П.М. Копейкин ◽  
Д.С. Орлов ◽  
Е.А. Корнева
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Activity ◽  
Innate Immunity ◽  
Infectious Diseases ◽  
Metabolic Activity ◽  
Capra Hircus ◽  
Bacterial Cells ◽  
Antibiotic Resistant ◽  
Resistant Strains

Антимикробные пептиды (АМП) системы врожденного иммунитета - соединения, играющие важную роль в патогенезе инфекционных заболеваний, так как обладают свойством инактивировать широкий спектр патогенных бактерий, обеспечивая противомикробную защиту живых организмов. В настоящее время АМП рассматриваются как потенциальные соединения-корректоры инфекционной патологии, вызываемой антибиотикорезистентными бактериями (АБР). Цель данной работы состояла в изученим механизмов антибактериального действия трех пептидов, принадлежащих к семейству бактенецинов - ChBac3.4, ChBac5 и mini-ChBac7.5Nb. Эти химически синтезированные пептиды являются аналогами природных пролин-богатых АМП, обнаруженных в лейкоцитах домашней козы Capra hircus и проявляющих высокую антимикробную активность, в том числе и в отношении грамотрицательных АБР. Методы. Минимальные ингибирующие и минимальные бактерицидные концентрации пептидов (МИК и МБК) определяли методом серийных разведений в жидкой питательной среде с последующим высевом на плотную питательную среду. Эффекты пептидов на проницаемость цитоплазматической мембраны бактерий для хромогенного маркера исследовали с использованием генетически модифицированного штамма Escherichia coli ML35p. Действие бактенецинов на метаболическую активность бактерий изучали с применением маркера резазурина. Результаты. Показано, что все исследованные пептиды проявляют высокую антимикробную активность в отношении Escherichia coli ML35p и антибиотикоустойчивых штаммов Escherichia coli ESBL и Acinetobacter baumannii in vitro, но их действие на бактериальные клетки разное. Использован комплекс методик, позволяющих наблюдать в режиме реального времени динамику действия бактенецинов в различных концентрациях (включая их МИК и МБК) на барьерную функцию цитоплазматической мембраны и на интенсивность метаболизма бактериальных клеток, что дало возможность выявить различия в характере воздействия бактенецинов, отличающихся по структуре молекулы, на исследуемые микроорганизмы. Установлено, что действие каждого из трех исследованных бактенецинов в бактерицидных концентрациях отличается по эффективности нарушения целостности бактериальных мембран и в скорости подавления метаболизма клеток. Заключение. Полученная информация дополнит существующие фундаментальные представления о механизмах действия пролин-богатых пептидов врожденного иммунитета, а также послужит основой для биотехнологических исследований, направленных на разработку на базе этих соединений новых антибиотических препаратов для коррекции инфекционных заболеваний, вызываемых АБР и являющимися причинами тяжелых внутрибольничных инфекций. Antimicrobial peptides (AMPs) of the innate immunity are compounds that play an important role in pathogenesis of infectious diseases due to their ability to inactivate a broad array of pathogenic bacteria, thereby providing anti-microbial host defense. AMPs are currently considered promising compounds for treatment of infectious diseases caused by antibiotic-resistant bacteria. The aim of this study was to investigate molecular mechanisms of the antibacterial action of three peptides from the bactenecin family, ChBac3.4, ChBac5, and mini-ChBac7.5Nb. These chemically synthesized peptides are analogues of natural proline-rich AMPs previously discovered by the authors of the present study in leukocytes of the domestic goat, Capra hircus. These peptides exhibit a high antimicrobial activity, in particular, against antibiotic-resistant gram-negative bacteria. Methods. Minimum inhibitory and minimum bactericidal concentrations of the peptides (MIC and MBC) were determined using the broth microdilution assay followed by subculturing on agar plates. Effects of the AMPs on bacterial cytoplasmic membrane permeability for a chromogenic marker were explored using a genetically modified strain, Escherichia coli ML35p. The effect of bactenecins on bacterial metabolic activity was studied using a resazurin marker. Results. All the studied peptides showed a high in vitro antimicrobial activity against Escherichia coli ML35p and antibiotic-resistant strains, Escherichia coli ESBL and Acinetobacter baumannii, but differed in features of their action on bacterial cells. The used combination of techniques allowed the real-time monitoring of effects of bactenecin at different concentrations (including their MIC and MBC) on the cell membrane barrier function and metabolic activity of bacteria. The differences in effects of these three structurally different bactenecins on the studied microorganisms implied that these peptides at bactericidal concentrations differed in their capability for disintegrating bacterial cell membranes and rate of inhibiting bacterial metabolism. Conclusion. The obtained information will supplement the existing basic concepts on mechanisms involved in effects of proline-rich peptides of the innate immunity. This information will also stimulate biotechnological research aimed at development of new antibiotics for treatment of infectious diseases, such as severe in-hospital infections, caused by antibiotic-resistant strains.

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