Pathogen killing pathogen: antimicrobial substance from Acinetobacter active against foodborne pathogens.

Cinara Souza Da Conceição,Janaína Dos Santos Nascimento,Barbara Victor Souza,Jessica Manya Bittencourt Dias Vieira

doi:10.3855/jidc.9894

Abstract

Antimicrobial substances (AMS) produced by bacteria may reduce or prevent the growth of pathogenic and spoilage microorganisms in food. In this study, 16 isolates of Acinetobacter baumannii/calcoaceticus (ABC) complex, previously obtained from reconstituted infant milk formula (IMF) samples and the preparation and distribution utensils from the nursery of a public hospital, were used to screen for AMS production. Antimicrobial substance production and spectrum of activity assays were performed by agar-spot assay. Optimization of growth conditions for AMS production was also evaluated. Three (17.6%) isolates, namely JE3, JE4, and JE6, produced AMS against the principal indicator strain Salmonella enterica subsp. enterica serotype Typhi ATCC 19214. JE6 was also able to inhibit strains of Klebsiella pneumoniae, Proteus vulgaris, and Bacillus cereus, a Gram-positive bacteria. Remarkably, JE6 was able to inhibit all the tested resistant and multidrug-resistant (MDR) strains of the ABC complex and Shigella dysenteriae associated with IMF and utensils, indicating a potentially valuable application. AMS produced by JE6 does not appear to be affected by proteolytic enzymes and the producer strain showed specific immunity to its own AMS. This study highlights AMS produced by Acinetobacter with applications against MDR spoilage and foodborne pathogens - some of them, infectious disease causing agents - which, to our knowledge, has not been previously described.

Highlights

Antimicrobial substances (AMS) produced by bacteria may reduce or prevent the growth of pathogenic and spoilage microorganisms in food
Sixteen isolates of Acinetobacter baumannii/calcoaceticus (ABC) complex, from reconstituted infant milk formula (IMF) samples and sanitized utensils used in preparation/distribution, from the nursery of a public hospital in Rio de Janeiro, Brazil
After 18 hours at 37°C, the bacteria were killed by exposure to chloroform vapor and the plates were sprayed with the indicator strain culture Salmonella enterica serotype Typhi ATCC 19214 (0.3 mL of a previously grown culture in 3 mL of Casoy soft agar)

Summary

Introduction

Antimicrobial substances (AMS) produced by bacteria may reduce or prevent the growth of pathogenic and spoilage microorganisms in food. Results: Three (17.6%) isolates, namely JE3, JE4, and JE6, produced AMS against the principal indicator strain Salmonella enterica subsp. JE6 was able to inhibit all the tested resistant and multidrug-resistant (MDR) strains of the ABC complex and Shigella dysenteriae associated with IMF and utensils, indicating a potentially valuable application. Conclusion: This study highlights AMS produced by Acinetobacter with applications against MDR spoilage and foodborne pathogens - some of them, infectious disease causing agents - which, to our knowledge, has not been previously described. The use of antimicrobial substances (AMS) with antagonistic properties has become the prime candidate in food safety and preservation research. Bacteriocins are proteins or peptides produced by bacteria that have antimicrobial properties [2,3,4]. Bacteriocins differ from most therapeutic antibiotics because they have a biologically active protein component (being rapidly digested by the proteases of the human digestive system), are ribosomally synthesized, and have a narrower activity spectrum [5,6]

Methods

Results

Conclusion