17
composition and bacteriophages to be involved in transfer of antibiotic resistance
genes between the microbiome of cystic fibrosis patients (Rolain et al. 2011).
Viruses have long been known to facilitate transduction, but now many phages have
been active in mobilizing genes conferring resistance to antibiotics such as imipenem, ceftazidime and aztreonam in Pseudomonas aeruginosa (Blahova et al. 2000);
multiple drug resistance in Salmonella enterica (Schmieger and Schicklmaier
1999); ampicillin resistance to Escherichia coli (Colomer-Lluch et al. 2011).
This attribute of bacteriophages as gene carriers has recently been reported from
niches such as sewage/waste water, which contains complex nutrients, high organic
matter and high concentration of antibiotics, antibiotic resistance genes and antibiotic resistance bacteria. Using quantitative PCR, bacteriophage fractions from this
niche has been found to harbor many antibiotic resistance genes (qnrS, bla TEM,
bla CTX-M , bla SHV , mecA, sul1) including those conferring multiple drug resistance
(Colomer-Lluch et al. 2011; Marti et al. 2014; Calero-Cáceres and Muniesa 2016).
The number and type of antibiotic resistance genes in the phage fractions sampled
from different sections (example sludge) of sewage treatment plants varies. Similar
loads of resistance determinants and phages have been found in human feces (Quirós
et al. 2014) and other environmental samples (Balcazar 2014). The presence of
phages and high number of antibiotic resistant bacteria and antibiotic resistance
genes in the sewage sludge makes it an active playground for transfer of antibiotic
resistance genes and many studies have implicated high incidence of transfer of
resistance (Colomer-Lluch et al. 2011; Calero-Cáceres et al. 2014). Although, more
evidence for the impact of phages in transfer of antibiotic resistance genes is
required, but the high number of antibiotic resistance genes they harbor and their
active involvement in transfer of genes, makes them a potential hazard and contributing factor in spread of antimicrobial resistance.
1.2.8 Antimicrobial Resistance and Agriculture
There are many ways that antibiotics can end up in the environment. These include
(and are not limited to) human sewage, veterinary and livestock farming waste and
surface run-off from any other sources (Gillings 2013) (Fig. 1.2). This is largely
because a large portion of the administered antibiotics is not completely metabolized and excreted out of humans/animals. This is governed by various factors,
including the type of antibiotic, dosage, age and species of the animal being administered. The waste material from these sources inevitably contains antibiotics and
antibiotic resistance genes (Martinez 2009). The leakage of antibiotics can happen
during irrigation, antibiotic contaminated dust, release from the antibiotic production pharmaceutical units, and even during transport and storage of the animalderived manure. This condition may arise due to inappropriate handling conditions
for aforementioned waste in the open, where it frequently mixes up with the rainwater. In addition to these, accidental spills from agricultural antibiotic storage units
and direct disposal of expired antibiotics from households/small vendors also
1 Antimicrobial Resistance Paradigm and One-Health Approach
composition and bacteriophages to be involved in transfer of antibiotic resistance
genes between the microbiome of cystic fibrosis patients (Rolain et al. 2011).
Viruses have long been known to facilitate transduction, but now many phages have
been active in mobilizing genes conferring resistance to antibiotics such as imipenem, ceftazidime and aztreonam in Pseudomonas aeruginosa (Blahova et al. 2000);
multiple drug resistance in Salmonella enterica (Schmieger and Schicklmaier
1999); ampicillin resistance to Escherichia coli (Colomer-Lluch et al. 2011).
This attribute of bacteriophages as gene carriers has recently been reported from
niches such as sewage/waste water, which contains complex nutrients, high organic
matter and high concentration of antibiotics, antibiotic resistance genes and antibiotic resistance bacteria. Using quantitative PCR, bacteriophage fractions from this
niche has been found to harbor many antibiotic resistance genes (qnrS, bla TEM,
bla CTX-M , bla SHV , mecA, sul1) including those conferring multiple drug resistance
(Colomer-Lluch et al. 2011; Marti et al. 2014; Calero-Cáceres and Muniesa 2016).
The number and type of antibiotic resistance genes in the phage fractions sampled
from different sections (example sludge) of sewage treatment plants varies. Similar
loads of resistance determinants and phages have been found in human feces (Quirós
et al. 2014) and other environmental samples (Balcazar 2014). The presence of
phages and high number of antibiotic resistant bacteria and antibiotic resistance
genes in the sewage sludge makes it an active playground for transfer of antibiotic
resistance genes and many studies have implicated high incidence of transfer of
resistance (Colomer-Lluch et al. 2011; Calero-Cáceres et al. 2014). Although, more
evidence for the impact of phages in transfer of antibiotic resistance genes is
required, but the high number of antibiotic resistance genes they harbor and their
active involvement in transfer of genes, makes them a potential hazard and contributing factor in spread of antimicrobial resistance.
1.2.8 Antimicrobial Resistance and Agriculture
There are many ways that antibiotics can end up in the environment. These include
(and are not limited to) human sewage, veterinary and livestock farming waste and
surface run-off from any other sources (Gillings 2013) (Fig. 1.2). This is largely
because a large portion of the administered antibiotics is not completely metabolized and excreted out of humans/animals. This is governed by various factors,
including the type of antibiotic, dosage, age and species of the animal being administered. The waste material from these sources inevitably contains antibiotics and
antibiotic resistance genes (Martinez 2009). The leakage of antibiotics can happen
during irrigation, antibiotic contaminated dust, release from the antibiotic production pharmaceutical units, and even during transport and storage of the animalderived manure. This condition may arise due to inappropriate handling conditions
for aforementioned waste in the open, where it frequently mixes up with the rainwater. In addition to these, accidental spills from agricultural antibiotic storage units
and direct disposal of expired antibiotics from households/small vendors also
1 Antimicrobial Resistance Paradigm and One-Health Approach