Abstract
Antibiotic resistance is a global issue which is magnified by interspecies horizontal gene transfer. Understanding antibiotic resistance in bacteria in a natural setting is crucial to check whether they are multidrug resistant (MDR) and possibly avoid outbreaks. In this study, we have isolated several antibiotic-resistant bacteria (ARB) (n = 128) from the mangroves in Kerala, India. ARBs were distributed based on antibiotics (p = 1.6 × 10−5). The 16S rRNA gene characterization revealed dominance by Bacillaceae (45%), Planococcaceae (22.5%), and Enterobacteriaceae (17.5%). A high proportion of the isolates were MDR (75%) with maximum resistance to methicillin (70%). Four isolates affiliated to plant-growth promoters, probiotics, food, and human pathogens were resistant to all antibiotics indicating the seriousness and prevalence of MDR. A significant correlation (R = 0.66; p = 2.5 × 10−6) was observed between MDR and biofilm formation. Antagonist activity was observed in 62.5% isolates. Gram-positive isolates were more susceptible to antagonism (75.86%) than gram-negative (36.36%) isolates. Antagonism interactions against gram-negative isolates were lower (9.42%) when compared to gram-positive isolates (89.85%). Such strong antagonist activity can be harnessed for inspection of novel antimicrobial mechanisms and drugs. Our study shows that MDR with strong biofilm formation is prevalent in natural habitat and if acquired by deadly pathogens may create havoc in public health.
Highlights
The discovery of antibiotics has been a breakthrough in the medical field, which has saved millions of lives
The phylogenetic relationship of the four isolates indicates that G1 has the closest phylogeny to Staphylococcus haemolyticus under the family Staphylococcaceae while A8, T8, and G2 have the closest hit to Bacillus cereus, Bacillus circulans, and Bacillus infantis, respectively, under family Bacillaceae (Figure 2)
The 16S rRNA gene identification revealed that the antibiotic-resistant isolates belonged to five families dominated by the Bacillaceae family (45%; 18 out of 40) followed by Planococcaceae (22.5%), Enterobacteriaceae (17.5%), Pseudomonadaceae (7.5%), Staphylococcaceae (5%), and Shewanellaceae (2.5%) (Figure 3A,B)
Summary
The discovery of antibiotics has been a breakthrough in the medical field, which has saved millions of lives. There is an increasing evidence of several non-pathogenic drug-resistant microbes in the environmental microbial community This is of serious concern since those non-pathogenic microbes could serve as a reservoir of antibiotic-resistant genes, which could spread to pathogens through horizontal gene transfer and give rise to numerous super bugs. Despite such threats, the natural environment microbial community resistome has received relatively less focus [1]. Microbes around producers would eventually develop resistance to antibiotics in order to coexist or compete for food and space Such origination of resistant genes, which has been found in the soil, is clinically relevant and causes difficulties in treating patients. In this paper, we have elucidated the multidrug resistant nature, biofilm, and the community antagonism from several antibiotic-resistant bacteria of mangrove sediment origin
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