Environment, antibiotics

Although it is still difficult to establish clear cause effect relationships, it is widely accepted that chemical pollution contributes for antibiotic resistance dissemination [10, 33, 34]. There are evidences that antibiotic resistance increase is related with environmental pollution and anthropic pressures. In this respect, antibiotics seem to be a major, although not the unique, form of pollution, mainly because it is estimated that about 75% of the antibiotics consumed by humans and animals are eliminated as active substances [35, 36]. In the environment, antibiotics can suffer adsorption, photolysis or biodegradation, reaching very low concentrations [37]. Nevertheless, at sub-inhibitory levels, as they are found in the environment, antibiotics can promote several alterations on housekeeping functions of the cells. Apparently, some of these alterations are not associated with antibiotic resistance. Even though, they contribute for the perturbation of the microbial community, leading, eventually, to an overall resistance increase [1, 34, 38]. 

UCS (2003). Hogging it Estimates of antimicrobial use in livestock. Available at the Union of Concerned Scientists website http //www.ucsusa.org/food and environment/antibiotic-resistance/index. 

Because of the highly permeable nature of the ced wad of gram-positive organisms, they produce P-lactamases which are not only found throughout the ced wad, but also in the extracedular environment. Hence the extracedular P-lactamases can act on the antibiotic before the ced is entered. 

The nature of the conditions of intensive production, however, can increase the risk of diseases and infections which can spread very rapidly and devastate large numbers of animals." Thus it is common practice for producers of poultry to add coccidiostats to their diets and vaccines to their drinking water in order to prevent coccidiosis and other infectious diseases such as bronchitis and Newcastle disease. A similar problem exists for intensively reared fish, where it is necessary to add antibiotics to their diets. A problem with intensively reared fish is that their diet is added directly into the water in which they live thus drugs and other additives in the diet are relatively easily dispersed into the local environment of fish farms, where they can increase bacterial resistance and also cause problems such as algal blooms. 

The level of antibiotic resistance of the gut flora of pigs has been found to be influenced by factors other than the inclusion of antibiotics in the diet " " such factors include the herd environment, history and the opportunity for cross-contamination. 

The 3-lactam antibiotics are cell-wall inhibitors toward susceptible bacteria. To survive in a hostile environment with ionic strengths often quite different from the interior of the cell, bacteria have evolved a rigid, quite complex cell wall. 

As recently as 1970, only about 30 naturally occurring organohalogen compounds were known. It was simply assumed that chloroform, halogenated phenols, chlorinated aromatic compounds called PCBs, and other such substances found in the environment were industrial pollutants. Now, only a third of a century later, the situation js quite different. More than 5000 organohalogen compounds have been found to occur naturally, and tens of thousands more surely exist. From a simple compound like chloromethane to an extremely complex one like vancomycin, a remarkably diverse range of organohalogen compounds exists in plants, bacteria, and animals. Many even have valuable physiological activity. Vancomycin, for instance, is a powerful antibiotic produced by the bacterium Amycolatopsis orientalis and used clinically to treat methicillin-resistant Staphylococcus aureus (MRSA). 

Numerous studies confirmed ubiquity of several antibiotics (i.e., ofloxacin, trimethoprim, roxythromycin, and sulfamethoxazole) in sewage influent, though at low ng level [8, 13, 14]. However, even at very low concentrations they can have significant ecotoxicological effects in the aquatic and terrestrial compartment [15, 16]. Indiscriminate or excessive use of antibiotics has been widely blamed for the appearance of so-called super-bugs that are antibiotic-resistant. It is of crucial importance to control their emissions into the environment through more cautious utilization and monitoring outbreaks of dmg-resistant infections. 

The results showed that the compounds studied with more frequency in the aquatic environment, and of which, logically, there is more information, are the antibiotics, analgesics and anti-inflammatories (like diclofenac, ibuprofen, naproxen, acetylsalicylic acid, and paracetamol), as well as the p-blocker atenolol. In the category of antibiotics, several families are included, like the macrolides (erythromycin), the fluoroquinolones (ofloxacin and ciprofloxacin), sulfonamides (sulfamethoxazole), penicillins (amoxicillin), the metronidazol, and trimethoprim. Other therapeutic groups also widely studied and frequently found in the environmental waters are the lipid regulators (gemfibrozil and bezafibrat), antiepileptic carbamaze-pine, and antidepressants (diazepam, fluoxetine, paroxetine) (see Table 3). 

Isidori M, Lavorgna M, Nardelli A, Pascarella L, Parella A (2005) Toxic and genotoxic evaluation of six antibiotics on non-target organisms. Sci Total Environ 346 87-98... 

McArdell CS, Molnar E, Suter MJF, Giger W (2003) Occurrence and fate of macrolide antibiotics in wastewater treatment plants and in the Glatt Valley watershed, Switzerland. Environ Sci Technol 37(24) 5479-5486... 

All laboratory operations are carried out in laminar flow cabinets in rooms in which filtered air is maintained at a slight positive pressure relative to their outer environment. Operators wear sterilized clothing and work aseptically. Antibiotic fermentations are, of strict necessity, pure culture aseptic processes, without con-tamirrating orgarrisms. 

Microbial cells may be subjected to stress from a number of sources in their environment. These include antibiotics, metal cations and metalloid oxyanions, aromatic hydrocarbons, chlorophenols,... 

A study with a strain of plasmid-bome antibiotic-resistant Escherichia coli indicated that the strain did not transmit these plasmids to indigenous strains after introduction into the terrestrial environment (Devanas et al. 1986). 

Brodhagen M, MD Henkels, JE Loper (2004) Positive antoregnlation and signaling properties of pyolnteorin, an antibiotic produced by the biological control organism Pseudomonas fluorescens Pf-5. Appl Environ Microbiol 70 1758-1766. 

Rasor and Tischer (1998) have brought out the advantages of enzyme immobilization. Examples of penicillin-G to 6-APA, hydrolysis of cephalospwrin C into 7-ACA, hydrolysis of isosorbide diacetate and hydrolysis of 5-(4-hydroxy phenyl) hydantom are cited. De Vroom (1998) has reported covalent attachment of penicillin acylase (EC 3.51.11) from E.Coli in a gelatine-based carrier to give a water insoluble catalyst assemblase which can be recycled many times, and is suitable for the production of semi-synthetic antibiotics in an aqueous environment. The enzyme can be applied both in a hydrolytic fashion and a synthetic fashion. 6-APA was produced from penicillin-G similarly, 7-ADCA was produced from desa acetoxycephalosporin G, a ring expansion product of penicillin G. 

The application of various antibiotics such as rifampicin/tetracycline (63), cefatoxime/trimethoprim (64), or bacteriostatic compounds such as Micropur (Roth, Karlsruhe, Germany) (65) used for root pretreatment or added to collection media is another strategy to prevent biodegradation during root exudate collection. However, depending on dosage and plant species, also phytotoxic effects of antibiotics have been reported (Table 3). Antibiotics in the soil environment... 

J. M. Raaijmakers, D. M. Weller, and L. S. Thomashow, Frequency of antibiotic producing Pseudomonas spp. in natural environments. Appk Environ. Microbiol. 63 881 (1997). 

L. A. Silo-Suh, B. J. Lethbridge, S. J. Raffel, H. He, J. Clardy, and J. Handelsman, Biological activities of two fungistatic antibiotics produced by Bacillus cercus UW85. Appl. Environ. Microbiol. 60 2023 (1994). 

D. J. Drahos, B. C. Hemming, and S. McPherson, Tracking recombinant organisms in the environment P-galactosida.se as a selectable non-antibiotic marker for fluorescent psudeomonads. Biotechnology. 4 439 (1986). 

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