Principal component analysis exploring the association between antibiotic resistance and heavy metal tolerance of plasmid-bearing sewage wastewater bacteria of clinical relevance

• Published in: Access microbiology Vol. 2; no. 3; p. acmi000095
• Main Authors: Mandal, Manisha, Das, Saumendra Nath, Mandal, Shyamapada
• Format: Journal Article
• Language: English
• Published: Microbiology Society 01-03-2020
• ISSN: 2516-8290; 2516-8290
• DOI: 10.1099/acmi.0.000095

This paper unravels the occurrence of plasmid-mediated antibiotic resistance in association with tolerance to heavy metals among clinically relevant bacteria isolated from sewage wastewater. The bacteria isolated were identified following conventional phenotypic and/or molecular methods, and were subjected to multiple-antibiotic resistance (MAR) profiling. The isolates were tested against the heavy metals Hg
2+
, Cd
2+
, Cr
2+
and Cu
2+
. SDS-PAGE and agarose gel electrophoretic analyses were performed, respectively, for the characterization of heavy metal stress protein and R-plasmid among the isolated bacteria. Principal component analysis was applied in determining bacterial resistance to antibiotics and heavy metals. Both lactose-fermenting (
Escherichia coli
) and non-fermenting (
Acinetobacter baumannii
and
Pseudomonas putida
) Gram-negative bacterial strains were procured, and showed MAR phenotypes with respect to three or more antibiotics, along with resistance to the heavy metals Hg
2+
, Cd
2+
, Cr
2+
and Cu
2+
. The Gram-positive bacteria,
Enterococcus faecalis
, isolated had ‘ampicillin–kanamycin–nalidixic acid’ resistance. The bacterial isolates had MAR indices of 0.3–0.9, indicating their (
E. faecalis
,
E. coli
,
A. baumannii
and
P. putida
) origin from niches with high antibiotic pollution and human faecal contamination. The Gram-negative bacteria isolated contained a single plasmid (≈54 kb) conferring multiple antibiotic resistance, which was linked to heavy metal tolerance; the SDS-PAGE analysis demonstrated the expression of heavy metal stress proteins (≈59 and ≈10 kDa) in wastewater bacteria with a Cd
2+
stressor. The study results grant an insight into the co-occurrence of antibiotic resistance and heavy metal tolerance among clinically relevant bacteria in sewage wastewater, prompting an intense health impact over antibiotic usage.