Acanthamoeba and bacteria produce antimicrobials to target their counterpart

Abstract

BackgroundIn the microbial ecosystem, microbes compete for space and nutrients. Consequently, some have developed the ability to kill or inhibit the growth of other competing microbes by producing antimicrobial substances. As the ‘producer’ species are generally immune to these substances, their compounds act on the competing microbial species and give the producer more space and access to nutrients for growth. Many currently used antibiotics were developed by exploiting this potential of certain microbes.FindingsHere, the free-living amoeba, Acanthamoeba castellanii, was investigated for its antibacterial activity against representative Gram positive and Gram negative bacteria, while bacterial isolates were tested for their anti-amoebic properties. Conditioned medium from A. castellanii showed remarkable bactericidal properties against methicillin-resistant Staphylococcus aureus (MRSA) exhibiting almost 100% kill rate, but had limited effect against Acinetobacter sp., Pseudomonas aeruginosa and vancomycin-resistant Enterococcus faecalis (VRE). Similarly, the conditioned medium of E. coli K1 and Enterobacter sp., exhibited potent anti-Acanthamoebic effects in a concentration-dependent manner. Conditioned media of Acanthamoeba, E. coli K1 and Enterobacter sp. showed no cytotoxicity in vitro when tested against human brain microvascular endothelial cells. Active molecule/s in aforementioned amoebic and two bacterial conditioned media were 5 – 10 kDa, and <5 kDa respectively.ConclusionsA. castellanii conditioned medium showed potent bactericidal properties against MRSA. The active molecule(s) are heat- and pronase-resistant, and in the 5 to 10 kDa molecular mass range. Contrary to this, E. coli K1 and Enterobacter sp., conditioned medium showed anti-amoebic effects that are <5 kDa in molecular mass, suggestive of active metabolites.

Gut bacteria of cockroaches are a potential source of antibacterial compound(s)

“…These molecules give growth advantage to producer species by killing or inhibiting the growth of other species (Iqbal et al . ). The producer species are immune to these molecules (Iqbal et al .…”

“…In the developing world, 68% of child mortality and 45% of all deaths are due to infectious diseases (Iqbal et al . ). While in under‐developed countries, infectious diseases are responsible for 63% of all deaths of children up to the age of 4 years (Murray and Lopez ).…”

Acanthamoeba polyphaga Mimivirus Prevents Amoebal Encystment-Mediating Serine Proteinase Expression and Circumvents Cell Encystment

“…Despite the recent interest in both organisms, there are few studies focusing on the interactions between Acanthamoeba spp. and the infecting mimivirus (9,10). Thus, the objective of this study was to analyze the interactions between Acanthamoeba spp.…”

Insects Offer a Useful Invertebrate Model to Screen Antimicrobial Libraries In Vivo

“…Clinical isolates of P. aeruginosa and MRSA were obtained and cultured at 37°C for 20 h in Luria-Bertani broth as previously described [6]. Adult locusts between 15-30 days old were divided into groups of 20 and injected with 20 μL of 2 x 106 c.f.u.…”

“…We have recently proposed the use of insects such as locust as an in vivo model to study bacterial and parasitic infections [3][4][5]. In the present study we propose the use of Locusta migratoria as a model to screen antimicrobial compounds against Pseudomonas aeruginosa or Methicillin-resistant Staphylococcus aureus (MRSA) infections in vivo.Clinical isolates of P. aeruginosa and MRSA were obtained and cultured at 37°C for 20 h in Luria-Bertani broth as previously described [6]. Adult locusts between 15-30 days old were divided into groups of 20 and injected with 20 μL of 2 x 106 c.f.u.…”