these findings pointed out the potential threat of carbamazepine in the environmental
spread of antimicrobial resistance.
3.5 Antibiotics
Antibiotics are natural or synthetic substances that kill (bactericidal) or inhibit the
growth (bacteriostatic) of bacteria [281]. They are commonly used in human and
veterinary medicines [282] as well as in agriculture [283–285] and aquaculture
[286, 287] to prevent or treat infections, as growth promoters [288, 289] and
sometimes as food preservatives [290]. There are about 250 different antibiotics
which can be classified on the basis of their mechanisms in four different groups
[281] such as those that inhibit the:
– Synthesis of the cell wall (beta-lactam and glycopeptides)
– Biosynthesis of proteins (aminoglycosides, tetracyclines, chloramphenicol,
macrolides, oxazolidinones)
– DNA replication (quinolones)
– Metabolism of folic acid (sulfonamides and trimethoprim)
As a result of their extensive use and their recalcitrance to degradation, antibiotics
are frequently found in various matrices such as wastewater [291–297], biosolids
[240, 298–301], sewage sludge [302–308], and farmyard manure [309–320]. Applications of these matrices to arable soils to water crop or as organic amendment can
lead to the dispersion of antibiotic residues in both terrestrial and aquatic ecosystems
[321, 322]. Indeed, antibiotics can runoff or leach from the soil polluting surface
water and groundwater, respectively [25, 323, 324]. The ubiquitous detection of
antibiotic residues in environmental matrices is cause for a great concern since even
at rather low concentration they exert a selection pressure favorable to the emergence
and further dispersion of antimicrobial resistances among environmental microbial
communities [325–330].
In addition, antibiotic residues may also inhibit specific microbial guilds or
functions and therefore disrupt critical processes for ecosystem functioning. Indeed,
they have been shown to affect degrading microorganisms, thereby impairing the
removal of organic matter and chemicals in sewage treatment plants [331–334]. In
addition, antibiotic residues contaminating wastewater or biosolids/manure that are
applied on arable soils can inhibit microbial populations involved in carbon and
nitrogen geochemical cycling [335, 336], climate regulation [337], and degradation
of xenobiotics and therefore may alter soil fertility and ecosystem health [338–343] .
In soils, antibiotics are subjected to microbial transformation with variable
degrading rates depending on their molecular structure and physicochemical properties [48, 344]. Amoxicillin (beta-lactam) and chlortetracycline are easily degradable [345, 346], while ciprofloxacine, norfloxacine (fluoroquinolones), azithromycin
(macrolides), and doxycycline (tetracyclines) are more recalcitrant to biodegradation
remaining for a long period of time in soils [131]. Interestingly, in several studies
Impact of PhACs on Soil Microorganisms
277
spread of antimicrobial resistance.
3.5 Antibiotics
Antibiotics are natural or synthetic substances that kill (bactericidal) or inhibit the
growth (bacteriostatic) of bacteria [281]. They are commonly used in human and
veterinary medicines [282] as well as in agriculture [283–285] and aquaculture
[286, 287] to prevent or treat infections, as growth promoters [288, 289] and
sometimes as food preservatives [290]. There are about 250 different antibiotics
which can be classified on the basis of their mechanisms in four different groups
[281] such as those that inhibit the:
– Synthesis of the cell wall (beta-lactam and glycopeptides)
– Biosynthesis of proteins (aminoglycosides, tetracyclines, chloramphenicol,
macrolides, oxazolidinones)
– DNA replication (quinolones)
– Metabolism of folic acid (sulfonamides and trimethoprim)
As a result of their extensive use and their recalcitrance to degradation, antibiotics
are frequently found in various matrices such as wastewater [291–297], biosolids
[240, 298–301], sewage sludge [302–308], and farmyard manure [309–320]. Applications of these matrices to arable soils to water crop or as organic amendment can
lead to the dispersion of antibiotic residues in both terrestrial and aquatic ecosystems
[321, 322]. Indeed, antibiotics can runoff or leach from the soil polluting surface
water and groundwater, respectively [25, 323, 324]. The ubiquitous detection of
antibiotic residues in environmental matrices is cause for a great concern since even
at rather low concentration they exert a selection pressure favorable to the emergence
and further dispersion of antimicrobial resistances among environmental microbial
communities [325–330].
In addition, antibiotic residues may also inhibit specific microbial guilds or
functions and therefore disrupt critical processes for ecosystem functioning. Indeed,
they have been shown to affect degrading microorganisms, thereby impairing the
removal of organic matter and chemicals in sewage treatment plants [331–334]. In
addition, antibiotic residues contaminating wastewater or biosolids/manure that are
applied on arable soils can inhibit microbial populations involved in carbon and
nitrogen geochemical cycling [335, 336], climate regulation [337], and degradation
of xenobiotics and therefore may alter soil fertility and ecosystem health [338–343] .
In soils, antibiotics are subjected to microbial transformation with variable
degrading rates depending on their molecular structure and physicochemical properties [48, 344]. Amoxicillin (beta-lactam) and chlortetracycline are easily degradable [345, 346], while ciprofloxacine, norfloxacine (fluoroquinolones), azithromycin
(macrolides), and doxycycline (tetracyclines) are more recalcitrant to biodegradation
remaining for a long period of time in soils [131]. Interestingly, in several studies
Impact of PhACs on Soil Microorganisms
277