Primary microbiological screening of amino acids and their modified variants

Abstract

Introduction.  The Fight against infectious diseases is still the most relevant problem in medicine. Antimicrobial chemical agents have the leading role in prophylaxis and treatment of diseases of microbial genesis. The main negative consequence of antibiotic therapy is the progressive resistance of the microorganisms. With increasing frequency, the specialists turn to the natural treatment approaches, especially towards plants that possess antibacterial activity and towards the compounds that compose the biological structure of the organisms and display various properties. The aim of the study – to substantiate microbiologically the use of new antimicrobial agents based on the modified amino acids variants. Materials and methods. 20 native amino acids and 52 synthetic derivatives of 7 amino acids were studied, All synthetic compounds were produced and characterized at the department of pharmakognosia of the national pharmaceutical university of the Health Ministry of Ukraine. For the primary screening  standard test cultures of gram-positive and gram-negative bacteria were used that belonged to different taxonomic groups. Determination of antimicrobial and anticandidal activity of the new compounds was carried out with the help of the standard methods of double serial dilution in the nutritive medium (macromethod). The testing was carried out in the volume of 1 ml of each dilution of the compounds with the final concentration of the studied microorganism approximately 5 × 10^5 CFU/ml. The minimal inhibiting concentration (MIC) was established according to the minimal concentration of the studied substance that suppressed the visible growth of the culture. For determination of the minimal bactericidal concentration (MBcC) measured seedings onto solid mediums (Muller-Hinton agar) from all the probes where no microorganism growth was observed were undertaken. The lowest concentration that caused death of no less than 99,9% bacteria was accepted as MBcC.  Results and discussion. Therefore, the primary microbiological screening of the 52 new synthetic amino acid derivatives has shown significant antimicrobial activity of the synthetic compounds against reference strains of gram-positive microorganisms (S.аureus АТСС 25923, B. subtilis ATCC 6633), mild antimicrobial activity of the overwhelming majority against gram-negative microorganisms (P. vulgaris ATCC 4636, E. coli АТСС 25922, P. aeruginosa ATCC 27853), and weak antifungal activity against Candida spp, fungi (C. аlbicans ATCC 885-653). For the more detailed study of the range and levels of the antimicrobial activity in the future, the lysine derivative compounds 6.1, 6.1.1, 6.1.2, 6.3, 6.6 and arginine derivative compounds 7.1.3, 7.1.5, 7.1.6, 7.1.7, and 7.1.11 were chosen, in order to develop antimicrobial agents based thereof. Conclusions. 1. Among the studied 20 native amino acids, only lysine and glycine had mild antimicrobial activity against reference strains of gram-negative and gram-positive microorganisms. 2. Primary microbiological screening of the 52 new synthetic amino acid derivatives has shown their high antimicrobial activity against reference strains of gram-positive microorganisms (S. aureus ATCC 25923 and B. subtilis ATCC 6633) in 94 % studied compounds (MIC in the range 3,9 – 15,6 μg/ml). 3. More than 80 % studied synthetic amino acid derivatives have shown high or mild activity (MIC in the range of 7,8 – 62,5 μg/ml) against gram-negative microorganisms test strains. 4. Based on the results of the study, the level of sensitivity of C. albicans ATCC 885-653 test strain to the synthetic amino acid derivatives was low. 5. It was proven experimentally that further studies of the range and level of antimicrobial activity of the certain most active compounds with the aim of new antimicrobial and antifungal agents development is both expedient and promising.

Introduction. TheFightagainstinfectiousdiseasesisstillthemostrelevantprobleminmedicine [1]. Antimicrobialchemicalagentshavetheleadingroleinprophylaxisandtreatmentofdiseasesofmicrobialgenesis [2]. Themainnegativeconsequenceofantibiotictherapyistheprogressiveresistanceofthemicroorganisms [3-5]. With increasing frequency, the specialists turn to the natural treatment approaches, especially towards plants that possess antibacterial activity and towards the compounds that compose the biological structure of the organisms and display various properties. The aim of the study – to substantiate microbiologically the use of new antimicrobial agents based on the modified amino acids variants. Materials and methods. 20 nativeaminoacidsand 52 syntheticderivativesof 7 amino acids were studied, All synthetic compounds were produced and characterized at the department of pharmakognosia of the national pharmaceutical university of the Health Ministry of Ukraine. Fortheprimaryscreening standard test cultures of gram-positive andgram-negativebacteriawereusedthatbelongedtodifferenttaxonomicgroups. Determinationofantimicrobialandanticandidalactivityofthenewcompoundswascarriedoutwiththehelpofthestandardmethodsofdouble serial dilution in the nutritive medium (macromethod). The testing was carried out in the volume of 1 ml of each dilution of the compounds with the final concentration of the studied microorganism approximately 5 × 10⁵CFU/ml. The minimal inhibiting concentration (MIC) was established according to the minimal concentration of the studied substance that suppressed the visible growth of the culture. Fordeterminationoftheminimalbactericidalconcentration (MBcC) measuredseedingsontosolidmediums (Muller-Hintonagar) fromalltheprobeswherenomicroorganismgrowthwasobservedwereundertaken. The lowest concentration that caused death of no less than 99,9% bacteria was accepted as MBcC.

Results and discussion. Therefore, theprimarymicrobiologicalscreeningofthe52 newsyntheticaminoacidderivativeshasshownsignificantantimicrobialactivityofthesyntheticcompoundsagainstreferencestrainsofgram-positivemicroorganisms (S.аureus АТСС 25923,B. subtilisATCC 6633), mildantimicrobialactivityoftheoverwhelmingmajorityagainstgram-negativemicroorganisms (P. vulgarisATCC 4636, E. coli АТСС 25922, P. aeruginosaATCC 27853), andweakantifungalactivityagainstCandidaspp, fungi (C. аlbicansATCC 885-653). For the more detailed study of the range and levels of the antimicrobial activity in the future, the lysine derivative compounds 6.1, 6.1.1, 6.1.2, 6.3, 6.6 and arginine derivative compounds 7.1.3, 7.1.5, 7.1.6, 7.1.7, and 7.1.11 were chosen, in order to develop antimicrobial agents based thereof.Conclusions. 1. Amongthestudied 20 nativeaminoacids, onlylysineandglycinehadmildantimicrobialactivityagainstreference strains of gram-negativeandgram-positivemicroorganisms.2. Primarymicrobiologicalscreeningofthe 52 newsyntheticaminoacidderivativeshasshowntheirhighantimicrobialactivityagainstreferencestrainsofgram-positivemicroorganisms (S. aureus ATCC 25923 and B. subtilis ATCC 6633) in 94 % studied compounds (MICintherange 3,9 – 15,6 μg/ml). 3. Morethan 80 % studiedsyntheticaminoacidderivativeshaveshownhighormildactivity (MICintherangeof 7,8 – 62,5 μg/ml) against gram-negative microorganisms test strains. 4. Basedontheresultsofthestudy, thelevelofsensitivityofC. albicans ATCC 885-653 test strain to the synthetic amino acid derivatives was low.5. Itwasprovenexperimentallythatfurtherstudiesoftherangeandlevelofantimicrobialactivityofthecertainmostactivecompoundswiththeaimofnewantimicrobialandantifungalagentsdevelopmentisbothexpedientandpromising.