Background: Hospital wastewater has a high amount of both organic and inorganic matter,
as well as high densities of living organisms, including pathogenic, and environmental bacteria. It has
been suggested that genes encoding resistance to an antibiotic can be located together with heavy
metals resistance genes on either the same genetic structure (plasmid) or different genetic structures
within the same bacterial strain. Resistance transfer is mainly attributed to conjugation since many antimicrobial
resistance genes are situated on mobile elements, such as plasmids and conjugative transposons,
whereas renovation and transduction are usually more limited. Our study confirmed the flow
of resistance genes between indigenous and foreign organisms and indicated the possibility of resistance
transfer from environmental reservoirs to pathogenic strains, which should be underlined in
the future. The recent patents on drug resistance (US20030130169, WO/2001/060387,
WO/2016/151092) and gene transfer (JP2003189855, JP2010094090), helped in this study.
Methods: Water samples were collected from three different sites of hospital wastewater. Isolation of
Gram-negative bacteria from hospital wastewater samples was done using the standard microbial procedure.
The heavy metal resistance was determined by the minimum inhibitory concentration (MIC)
against the test bacterial strain by spot plate method. The antibiotic resistance was determined by a
standard disc diffusion technique. The bacterial resistance transfer studies were determined between
donor and recipient strain in nutrient as well as wastewater. The antibiogram and MIC of the donors
and transconjugants were studied by above-described methods.
Results: A high number of Gram-Negative Bacterial Isolates (GNB) exhibited antibiotic and metal resistance
transfer into E. coli K-12 and similar GNB isolates in nutrient broth as compared to
wastewater. The microbial conjugation experiments showed that a high percentage of multi-resistant
GNB (75% and 66%) was able to transfer their single or multidrug resistance patterns to E. coli K-12
among antibiotic while 58%, 66% of the multiresistant isolates were able to transfer their single or
multi-metal resistance patterns to E. coli K-12 among metal in nutrient medium and wastewater, respectively.
In the present conjugation study, 97.5% and 70% of the total tested GNB isolates were
able to transfer an antibiotic-resistant marker to recipient GNB in both the medium (nutrient medium
and wastewater), whereas 92.5% and72.5% of the isolates were able to transfer metal resistant marker
to recipient GNB in nutrient medium and wastewater from all the site tested. The higher (6.8x10-1 and
5.9x10-1) frequency of transfer was observed among antibiotic and metal while the lower frequency of
transfer was (7.0x10-3 and 2.0x10-3) exhibited against antibiotic and metal in both the medium from
the entire site tested, respectively.
Conclusion: We can recommend that the hospital water is heavily polluted with several types of antibiotics,
toxic metals as well as the potentially hazardous bacterial flora because of their capacity to resist
one or the other well known antibiotic and chemotherapeutic agents. These studies provide evidence
that a wide variety of clinically important antibiotic and metal resistance genes is mobile within
aquatic bacterial communities one step ahead of the above, we can envisage the alarming situation
prevailing in our system and surrounding in the light of transmissible nature of R-plasmids.