Abstract
The emergence of nearly untreatable infections caused by multidrug-resistant bacteria has led to a new public health concern in which a need for development of alternative non-antibiotic strategies has become urgent. The activity of metabolites produced by new strains of Lactobacillus against multidrug-resistant bacteria was investigated. The objective of this work was to isolate and identify lactobacilli from artisanal kefir by 16S rRNA gene sequencing as well as to evaluate the effect of the growth of Lactobacillus species in the Man Rogosa and Sharpe broth, supplemented with Tween 80 at concentrations of 0.6, 0.4, and 0.2 %. Cell Free Supernatants (CFSs) were obtained from these lactobacilli cultures and with them, organic acids (lactic acid and acetic acid) and ethanol were quantified by HPLC followed by the determination of their antimicrobial activities against eight strains of Staphylococcus aureus-MRSA and Klebsiella pneumonia KPC strains. The GenBank BLAST analysis revealed that, the isolated lactobacilli belonged to Lactobacillus paracasei (n=4) and Lactobacillus plantarum (n=5) strains. Increasing concentrations of Tween 80 did not affect the growth of Lactobacillus species significantly when compared to their controls (MRS broth). HPLC analysis of CFSs showed concentrations greater than 18.0, 4.0 and 1.0 g/L for lactic acid, acetic acid and ethanol, respectively. All CFSs were able to inhibit all pathogenic microorganisms evaluated. The percentage of inhibition was on average greater than 88% for MRSA and KPC strains. The antimicrobial activity was dependent on the CFSs tested. Based on these experimental conditions, organic acids and ethanol are likely to be responsible for this antimicrobial activity. Key words: Antibacterial activity, lactobacilli, cell free supernatants, Tween 80.
Highlights
The nosocomial infections caused by multidrug-resistant microorganisms (MDR) are among the most serious problems of clinical medicine and pose a major public health concern (Cecchini et al, 2015)
The growth curves of Lactobacillus species exposed to different concentrations of Man Rogosa and Sharpe (MRS)/Tween 80 (TW) are showed in Figures 1, 2, 3 and 4
The different concentrations of Tween 80 (0.2, 0.4 and 0.6%) present in the MRS medium did not significantly affect the growth of L. paracasei and L. plantarum strains, nor did it affect those of Lactobacillus rhamnosus ATCC 9595 when compared to their controls or to each other, p0.05
Summary
The nosocomial infections caused by multidrug-resistant microorganisms (MDR) are among the most serious problems of clinical medicine and pose a major public health concern (Cecchini et al, 2015). Methicillin resistant Staphylococcus aureus (MRSA) and extended spectrum β-lactamase (ESBL) producing Klebsiella pneumoniae are. The main bacteria associated with nosocomial infections (Fuzi, 2016). MDR develop numerous strategies of resistance to antimicrobial agents and host defenses. Patients infected by these microorganisms have increased length of hospital stay and higher mortality rate compared to individuals infected with susceptible strains (Spicknall et al, 2013)
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