A new study suggests that the gut bacteria from cockroaches produce potent antibacterial compounds that could be utilised against multidrug-resistant pathogens.
Antibiotic resistance has become a prominent issue in the treatment of bacterial infections, and has therefore emerged as a significant global threat to human health. An estimated 25,000 people die each year across Europe due to hospital infections caused by 5 key resistant bacteria, including E. coli and MRSA. Globally, antibiotic resistance could result in 10 million deaths each year by 2050, and a £66 trillion loss in economic productivity.
The misuse of antibiotics has played a key part in the multifaceted cause of antimicrobial resistance, and now only 3 of the 41 antibiotics in development have the potential to fight the majority of the most resistant bacteria. This alarming statistic unfortunately coincides with another one – it has been 30 years since a new class of antibiotics was last introduced. There is a clear and urgent demand for novel antimicrobials to be identified, and the insect world has become an area of significant interest as a potential source of new antimicrobial compounds.
A research group from Malaysia (Akbar et al.) have asked the question – how do animals such as cockroaches survive and thrive in the sordid conditions that they inhabit? In answer, Akbar et al. hypothesised that the gut bacteria of cockroaches produce antimicrobial compounds that help prevent bacterial infections.
To explore this notion, Akbar et al. isolated the gut bacteria from two different species of cockroach, and prepared conditioned media from these bacteria. Conditioned media refers to the broth that the isolated bacteria have been grown in, with the bacteria subsequently removed by filtration. This is a useful technique used to investigate any compounds produced by the bacteria, rather than the bacteria itself. The prepared conditioned media was tested for its effectiveness against a range of pathogenic bacteria.
Seven different conditioned media (CM 1-7) were prepared from the seven different types of bacteria isolated from the cockroaches. The team then incubated varying pathogenic bacteria with the conditioned media and the viable bacterial colonies were enumerated. Most, if not all of the seven conditioned media had significant bactericidal effects on the following pathogenic bacteria: MRSA, E. coli, K. pneumoniae, S. pyogenes, P. aeruginosa, S. enterica and S. marcescens. This means that bacteria isolated from the cockroach’s gut produce antimicrobial compounds that can fight some of the most troublesome and resistant bacteria relevant to antibiotic resistance.
Importantly, Akbar et al. found that 95oC heat-treatment of the conditioned media had no effect on their antibacterial properties, indicating that the antimicrobial compounds in question are stable and are likely to be small peptides or metabolites.
It is well-established that microorganisms such as bacteria release compounds that interfere with neighbouring bacteria to give a competitive advantage. Due to this, a lot of research interest has been given to identifying such antimicrobial compounds produced by bacteria in obscure environments. Therefore, to investigate the gut bacteria of cockroaches in such a manner is relevant, novel, and seemingly effective. The preparation of conditioned media in this study is also practically astute as it can be made in reproducibly large quantities and would thus prove a powerful method for future antibacterial testing.
This study did not identify the precise active antimicrobial compounds released by cockroach gut bacteria, which is the only shortcoming. This would allow similar molecules to be ‘screened’ for in other bacterial environments, and therefore adding more chapters to this intriguing and important story.