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).
Rhipicephalus annulatus is a vector of bovine babesiosis (cattle fever) and bovine anaplasmosis that infect approximately 80% of cattle production, leading to loss in the livestock and dairy industry. They are vectors of disease agents to humans. Cuticular hydrocarbons (CHCs) have been used as a chemotaxonomic tool to facilitate the identification of various arthropod species since the 1970s. The present study used GC-MS to differentiate the CH components of feeding stages of female R. annulatus. Hydrocarbons identified from the three stages contain 7 to 44 carbons and include linear strait-chained alkanes, and a few branched alkanes and alkenes. The chemical diversity was higher in an unfed stage and lower in an engorged one. The most abundant compounds across all stages were eicosane and tetracosane. Principal component and cluster analyses revealed that engorged stages were the most dissimilar stage in terms of their CHC profile, while the unfed and semi-fed stages showed relatively similar CHC profiles. The results obtained in this study demonstrated the potential use of CHCs to identify species, and different stages for female R. annulatus, determination of the most affected stage to be easily controlled, and establishment of a database to be used in chemotaxonomy of tick species.
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