Abstract
The insect gut is home to a wide range of microorganisms, including several bacterial species. Such bacterial symbionts provide various benefits to their insect hosts. One of such services is providing metabolites that resist infections. Little data are available about gut-inhabiting bacteria for several insect groups. Through the present work, the gut bacteria associated with the American cockroach (Periplaneta americana L.) were isolated, identified, and studied for their potential antimicrobial activity against multidrug-resistant (MDR) human pathogens. The cockroaches were collected from three different environmental sites. Gut bacteria were isolated, and sixteen species of bacteria were identified using Vitek MALDI-TOF MS. The antagonistic activity of the identified bacteria was tested against a panel of multidrug-resistant bacteria and fungi, namely: methicillin-resistant Staphylococcus aureus (MRSA) (clinical isolate), Streptococcus mutans Clarke (RCMB 017(1) ATCC ® 25175™) (Gram-positive bacteria), Enterobacter cloacae (RCMB 001(1) ATCC® 23355™) and Salmonella enterica (ATCC® 25566™) (Gram-negative bacteria). The isolates were also tested against human pathogenic fungi such as Candida albicans (RCMB005003(1) ATCC® 10231™), Aspergillus niger (RCMB002005), Aspergillus fumigatus (RCMB002008), Aspergillus flavus (RCMB002002), and Penicillium italicum (RCMB 001018(1) IMI193019). The results indicated that some bacterial species from the cockroach gut could antagonize the growth activity of all the tested pathogens. Such antimicrobial properties could ultimately lead to the future development of therapeutic drugs. The evaluation and mode of action of antagonistic gut bacteria against the most affected MDR pathogens were demonstrated using transmission electron microscopy (TEM).
Highlights
Drug-resistant pathogens are one of the most challenging issues facing public health today [1]
All bacteria species were isolated from a single site except two species: Bacillus sphaericus, which was isolated from insects collected at the paper factory and from sewage water, referred to as 1 and 12, respectively; and Serratia marcescens, which was isolated from insects collected from the food store and from sewage water, referred to as 4 and 15
The present work showed that some of the gut bacteria isolated from the American cockroach, P. americana L., had outstanding antimicrobial activities against the most tested MDR human pathogens
Summary
Drug-resistant pathogens are one of the most challenging issues facing public health today [1]. The WHO considers drug-resistant bacterium as one of the ten most threatening health issues confronting humanity in the present century [2]. Many species of bacteria have developed strong resistance against several groups of antimicrobial agents, especially with the rapid global spread of multi- and pan-resistant bacteria that have induced infections while not being treated with existing antimicrobial drugs [3]. The problem of drug resistance is found in the treatment of pathogenic fungi. Searching for new sources of antimicrobial agents for tackling this problem is becoming increasingly urgent. Insects form one of these interesting new alternative sources of drugs for the era [4]
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