Antibacterial agents and heavy metal resistance in Gram-negative bacteria isolated from seawater, shrimp and sediment in Iskenderun Bay, Turkey

The aim of the present study was to determine the level of antibiotic resistance patterns and distribution of heavy metal resistance of bacterial isolates from seawater, sediment and shrimps, and to determine if there is a relationship between antibiotic and heavy metal resistance. We undertook studies in 2007 in the industrially polluted Iskenderun Bay, on the south coast of Turkey. The resistance of 236 Gram-negative bacterial isolates (49 from seawater, 90 from sediment and 97 from shrimp) to 16 different antibiotics, and to 5 heavy metals, was investigated by agar diffusion and agar dilution methods, respectively. A total of 31 species of bacteria were isolated: the most common strains isolated from all samples were Escherichia coli (11.4%), Aeromonas hydrophila (9.7%) and Stenotrophomonas maltophilia (9.3%). There was a high incidence of resistance to ampicillin (93.2%), streptomycin (90.2%) and cefazolin (81.3%), and a low incidence of resistance to imipenem (16.5%), meropenem (13.9%) and cefepime (8.0%). Some 56.8% of all bacteria isolated from seawater, sediment and shrimp were resistant to 7 or more antibiotics. Most isolates showed tolerance to different concentrations of heavy metals, and minimal inhibition concentrations ranged from 12.5 μg/ml to > 3200 μg/ml. The bacteria from seawater, sediment and shrimp showed high resistance to cadmium of 69.4%, 88.9%, and 81.1% respectively, and low resistance to manganese of 2%, 6.7% and 11.3% respectively. The seawater and sediment isolates which were metal resistant also showed a high resistance to three antibiotics: streptomycin, ampicillin and trimethoprim-sulphamethoxazole. In contrast, the shrimp isolates which were metal resistant were resistant to four antibiotics: cefazolin, nitrofurantoin, cefuroxime and ampicillin. Our results show that Iskenderun Bay has a significant proportion of antibiotic and heavy metal resistant Gram-negative bacteria, and these bacteria constitute a potential risk for public health.     

Antibiotic resistant enterococci and staphylococci isolated from flies collected near confined poultry feeding operations

Use of antibiotics as feed additives in poultry production has been linked to the presence of antibiotic resistant bacteria in farm workers, consumer poultry products and the environs of confined poultry operations. There are concerns that these resistant bacteria may be transferred to communities near these operations; however, environmental pathways of exposure are not well documented. We assessed the prevalence of antibiotic resistant enterococci and staphylococci in stored poultry litter and flies collected near broiler chicken houses. Drug resistant enterococci and staphylococci were isolated from flies caught near confined poultry feeding operations in the summer of 2006. Susceptibility testing was conducted on isolates using antibiotics selected on the basis of their importance to human medicine and use in poultry production. Resistant isolates were then screened for genetic determinants of antibiotic resistance. A total of 142 enterococcal isolates and 144 staphylococcal isolates from both fly and poultry litter samples were identified. Resistance genes erm(B), erm(A), msr(C), msr(A/B) and mobile genetic elements associated with the conjugative transposon Tn916, were found in isolates recovered from both poultry litter and flies. Erm(B) was the most common resistance gene in enterococci, while erm(A) was the most common in staphylococci. We report that flies collected near broiler poultry operations may be involved in the spread of drug resistant bacteria from these operations and may increase the potential for human exposure to drug resistant bacteria.     

Multiresistant Enterobacteriaceae with class 1 and class 2 integrons in a municipal wastewater treatment plant

In this study, 1832 strains of the family Enterobacteriaceae were isolated from different stages of a municipal wastewater treatment plant, of which 221 (12.1%) were intI-positive. Among them 61.5% originated from raw sewage, 12.7% from aeration tank and 25.8% from the final effluent. All of the intI-positive strains were multiresistant, i.e. resistant to at least three unrelated antimicrobials. Although there were no significant differences in resistance range, defined as the number of antimicrobial classes to which an isolate was resistant, between strains isolated from different stages of wastewater treatment, for five β-lactams the percentage of resistant isolates was the highest in final effluent, which may reflect a selective pressure the bacteria are exposed to, and the possible route of dissemination of β-lactam resistant strains to the corresponding river. The sizes of the variable part of integrons ranged from 0.18 to 3.0 kbp and contained up to four incorporated gene cassettes. Sequence analysis identified over 30 different gene cassettes, including 24 conferring resistance to antibiotics. The highest number of different gene cassettes was found in bacteria isolated from the final effluent. The gene cassettes were arranged in 26 different resistance cassette arrays; the most often were dfrA1-aadA1, aadA1, dfrA17-aadA5 and dfrA12-orfF-aadA2. Regarding the diversity of resistance genes and the number of multiresistant bacteria in the final effluent, we concluded that municipal sewage may serve as a reservoir of integron-embedded antibiotic resistance genes.     

High diversity and abundance of antibiotic-resistant Escherichia coli isolated from humans and farm animal hosts in Jeonnam Province, South Korea

The spread of antibiotics resistance among bacteria is a threat to human health. Since South Korea uses approximately 1.5 times more antibiotics than do other OECD countries, this is likely to impact the numbers and types of antibiotic-resistant bacteria found in the environment. In this study we examined feces from domesticated animals and humans for the diversity and abundance of antibiotic-resistant Escherichia coli. Abundant antibiotic-resistant E. coli were isolated from all the tested animals and humans and were examined by horizontal, fluorophore-enhanced, rep-PCR (HFERP) DNA fingerprint analysis. A total of 793 unique, non-clonal, E. coli isolates were obtained from the 513 human and animal hosts examined. Antibiotic resistance analysis, done using 14 antibiotics, indicated that 72.3% of the isolates (573 of 793) were found resistant to more than one antibiotic. The E. coli isolated from swine were resistant to the greatest number of antibiotics. Tetracycline resistant E. coli were routinely isolated from all animal hosts (36 to 77% per host), except for dairy cattle (9.3%). Twenty nine E. coli isolates from all hosts, except for duck, were resistant to more than 10 antibiotics. Gene transfer and southern hybridization studies revealed that resistance to 13 of the antibiotics was self-transmissible, and likely mediated by plasmids and integrons. Since genetically diverse and numerically abundant antibiotic-resistant E. coli were consistently recovered from chicken, swine and other domesticated animals in South Korea, our results suggest that the use of sub-therapeutic levels of antibiotics for disease prophylaxis and growth promotion should be curtailed.     

Incidence of heavy metal and antibiotic resistance in bacterial isolates from Blue Nile river water in Ethiopian region

Heavy metal pollution of river water has health implications. This study was aimed to test if bacteria that are heavy metal resistant can resist antibiotics. Heavy metal-resistant bacteria were isolated using Nutrient agar plates amended with 100?μg?ml^?1 of metal salts. Isolates were further screened to determine minimal inhibitory concentration against each metal. The isolates belonged to the genera of Neisseria, Bacillus, Pseudomonas, Staphylococcus, Streptococcus, Micrococcus, Corynebacterium and Proteus. Minimum inhibitory concentration of the isolates for heavy metals ranged from 200 to 2300?μg?ml^?1. Isolates of Pseudomonas, Neisseria, Bacillus, Protues, Streptococcus, Staphylococcus and Micrococcus spp. exhibited multiple antibiotic resistance. Statistically significant correlation between metal resistance and antibiotic resistance was observed among bacterial isolates. The present work suggests that some of the isolates could be hazardous to human beings as a result of natural selection of dual resistant mechanisms.     

Microbial and antibiotic resistant constituents associated with biological aerosols and poultry litter within a commercial poultry house

Poultry are known to harbor antibiotic resistant and pathogenic bacteria, and as such poultry litter and poultry house air can be contaminated with these bacteria. However, the presence of antibiotic resistant bacteria in biological aerosols and litter is largely not understood. The purpose of this study was to determine the amount of aerosolized bacteria and endotoxin, particularly fecal indicators, staphylococci, and enterococci, associated with poultry house and outdoor air. Aerosol samples were collected at multiple locations on the farm and in the house. Antibiotic resistance was investigated using the Kirby Bauer method on selected isolates using twelve different antibiotics spanning both narrow to broad spectrums of effectiveness. Overall there was a cyclical increase in bacterial concentrations as flocks progressed from pre-flock to late-flock, with > 2 orders magnitude lower concentration during pre-flock periods (no chickens), in both the litter and aerosol samples. The house environment provided for significantly concentrated bacterial and endotoxin levels. It was estimated that Staphylococcus bacteria accounted for at least 90% of cultured aerobic bacteria and culture-independent 16S rRNA analyses demonstrated that significant population changes occurred from pre- to late-flock. Rarely was an isolate resistant to more than 4 antibiotic classes; however there was a trend upwards in overall resistance of enterococci as the flock cycle progressed. It appears that although levels of antibiotic resistant bacteria were highly concentrated within the house, levels were much lower outside of the house, and very little house escape occurred.     

Novel homologs of the multiple resistance regulator marA in antibiotic-contaminated environments

Antibiotics are commonly detected in the environment as contaminants. Exposure to antibiotics may induce antimicrobial-resistance, as well as the horizontal transfer of resistance genes in bacterial populations. We selected the resistance gene marA, mediating resistance to multiple antibiotics, and explored its distribution in sediment and water samples from surface and sewage treatment waters. Ciprofloxacin and ofloxacin (fluoroquinolones), sulphamethoxazole (sulphonamide), erythromycin, clarythromycin, and spiramycin (macrolides), lincomycin (lincosamide), and oxytetracycline (tetracycline) were measured in the same samples to determine antibiotic contamination. Bacterial populations from environmental samples were challenged with antibiotics to identify resistant isolates. The gene marA was found in almost all environmental samples and was confirmed by PCR amplification in antibiotic-resistant colonies. 16S rDNA sequencing revealed that the majority of resistant isolates belonged to the Gram-positive genus Bacillus, not previously known to possess the regulator marA. We assayed the incidence of marA in environmental bacterial populations of Escherichia coli and Bacillus by quantitative real-time PCR in correlation with the levels of antibiotics. Phylogenetic analysis indicated the possible lateral acquisition of marA by Bacillus from Gram-negative Enterobacteriaceae revealing a novel marA homolog in Bacillus. Quantitative PCR assays indicate that the frequency of this gene in antropised environments seems to be related to bacterial exposure to water-borne antibiotics.     

Diversity and antibiotic resistance of Aeromonas spp. in drinking and waste water treatment plants

The taxonomic diversity and antibiotic resistance phenotypes of aeromonads were examined in samples from drinking and waste water treatment plants (surface, ground and disinfected water in a drinking water treatment plant, and raw and treated waste water) and tap water. Bacteria identification and intra-species variation were determined based on the analysis of the 16S rRNA, gyrB and cpn60 gene sequences. Resistance phenotypes were determined using the disc diffusion method.Aeromonas veronii prevailed in raw surface water, Aeromonas hydrophyla in ozonated water, and Aeromonas media and Aeromonas puntacta in waste water. No aeromonads were detected in ground water, after the chlorination tank or in tap water. Resistance to ceftazidime or meropenem was detected in isolates from the drinking water treatment plant and waste water isolates were intrinsically resistant to nalidixic acid. Most of the times, quinolone resistance was associated with the gyrA mutation in serine 83. The gene qnrS, but not the genes qnrA, B, C, D or qepA, was detected in both surface and waste water isolates. The gene aac(6’)-ib-cr was detected in different waste water strains isolated in the presence of ciprofloxacin. Both quinolone resistance genes were detected only in the species A. media. This is the first study tracking antimicrobial resistance in aeromonads in drinking, tap and waste water and the importance of these bacteria as vectors of resistance in aquatic environments is discussed.     

Prevalence of antibiotic and heavy metal resistance in Gram negative bacteria isolated from rivers in northern Pakistan

Antibiotic and metal resistance is a global occurring phenomenon and a universal threat. The release of antibiotics and metals into the environment like natural water bodies stimulates resistant microbes that could become a reservoir for a resistant gene pool for other pathogenic bacteria. The aim of the study was to determine microbial diversity, distribution of antibiotic and metal resistance bacteria from five rivers. The resistance of 168 Gram negative isolates was tested against 10 antibiotics and five metals. The study revealed a high incidence of bacterial isolates resistant to ampicillin (44.7%), streptomycin (37.3%) and chloramphenicol (33.9%). The highest level of antibiotic resistance was detected in the River Ravi. The multiple antibiotic resistance (MAR) index of the five rivers ranged from <0.2 to 0.6. Isolates displayed tolerance to different concentrations of heavy metals. High antibiotic and metal‐resistances in samples from the Rivers Ravi and Soan suggest co‐resistance amongst the bacterial populations.     

Wastewater treatment contributes to selective increase of antibiotic resistance among Acinetobacter spp.

The occurrence and spread of multi-drug resistant bacteria is a pressing public health problem. The emergence of bacterial resistance to antibiotics is common in areas where antibiotics are heavily used, and antibiotic-resistant bacteria also increasingly occur in aquatic environments. The purpose of the present study was to evaluate the impact of the wastewater treatment process on the prevalence of antibiotic resistance in Acinetobacter spp. in the wastewater and its receiving water. During two different events (high-temperature, high-flow, 31 °C; and low-temperature, low-flow, 8 °C), 366 strains of Acinetobacter spp. were isolated from five different sites, three in a wastewater treatment plant (raw influent, second effluent, and final effluent) and two in the receiving body (upstream and downstream of the treated wastewater discharge point). The antibiotic susceptibility phenotypes were determined by the disc-diffusion method for 8 antibiotics, amoxicillin/clavulanic acid (AMC), chloramphenicol (CHL), ciprofloxacin (CIP), colistin (CL), gentamicin (GM), rifampin (RA), sulfisoxazole (SU), and trimethoprim (TMP). The prevalence of antibiotic resistance in Acinetobacter isolates to AMC, CHL, RA, and multi-drug (three antibiotics or more) significantly increased (p < 0.01) from the raw influent samples (AMC, 8.7%; CHL, 25.2%; RA, 63.1%; multi-drug, 33.0%) to the final effluent samples (AMC, 37.9%; CHL, 69.0%; RA, 84.5%; multi-drug, 72.4%), and was significantly higher (p < 0.05) in the downstream samples (AMC, 25.8%; CHL, 48.4%; RA, 85.5%; multi-drug, 56.5%) than in the upstream samples (AMC, 9.5%; CHL, 27.0%; RA, 65.1%; multi-drug, 28.6%). These results suggest that wastewater treatment process contributes to the selective increase of antibiotic resistant bacteria and the occurrence of multi-drug resistant bacteria in aquatic environments.     

Antibiotic resistance and tolerance to heavy metals demonstrated by environmental pathogenic bacteria isolated from the Kahwa River,Bukavu Town,Democratic Republic of the Congo

Increasing concentration of heavy metals and antibiotics within bacterial microenvironments contribute to medical problems. This research confirmed the presence of enteropathogenic bacteria in the sediment and water of Kahwa River. Vibrio cholerae, Shigella dysenteriae, Salmonella typhi and Salmonella paratyphi showed resistance to antibiotics and tolerance to heavy metals. The bacteria, particularly Vibrio, were extensively resistant to Ampicillin; less so to Chloramphenicol, Co-trimoxazole and Tetracycline with a relatively reduced resistance shown to Ciprofloxacin. Higher levels of antibiotic resistance were noticed in bacteria isolated from river sediment when compared to bacteria isolated from river water (p < 0.05). Tolerance to cadmium and lead was also more obvious in bacteria isolated from river sediment. An increasing association was observed between multiple antibiotic resistance and tolerance to heavy metals. Bacterial growth in the presence of cadmium was restricted when compared to lead.     

Populations of antibiotic-resistant coliform bacteria change rapidly in a wastewater effluent dominated stream

Incomplete elimination of bacteria and pharmaceutical drugs during wastewater treatment results in the entry of antibiotics and antibiotic-resistant bacteria into receiving streams with effluent inputs. In Mud Creek in Fayetteville, AR, ofloxacin, trimethoprim, and sulfamethoxazole have been detected in water and sediment, and tetracycline has been detected in sediment downstream of treated effluent input. These antibiotics have been measured repeatedly, but at low concentrations (< 1 μg/L) in the stream. To determine if effluent input results in detectable and stable changes in antibiotic resistances downstream of effluent input, antibiotic resistance in Escherichia coli and total coliform bacteria in Mud Creek stream water and sediment were determined using a culture-based method. Isolated E. coli colonies were characterized for multiple antibiotic resistance (MAR) patterns on solid media and to evaluate E. coli isolate richness by amplification of a partial uidA gene followed by denaturant gradient gel electrophoresis (DGGE). Despite temporal variability, proportions of antibiotic-resistant E. coli were generally high in effluent and 640 m downstream. The MAR pattern ampicillin-trimethoprim-sulfamethoxazole was associated with a DGGE profile that was detected in effluent and downstream E. coli isolates, but not upstream. Percent resistance among coliform bacteria to trimethoprim and sulfamethoxazole was higher 640 m downstream compared to upstream sediment and water (with one exception). Resistance to ofloxacin was too low to analyze statistically and tetracycline resistance was fairly constant across sites. Resistances changed from 640 m to 2000 m downstream, although dissolved nutrient concentrations within that stream stretch resembled effluent. Antibiotic resistant bacteria are entering the stream, but resistances change within a short distance of effluent inputs, more quickly than indicated based on chemical water properties. Results illustrate the difficulty in tracking the input and fate of antibiotic resistance and in relating the presence of low antibiotic concentrations to selection or persistence of antibiotic resistances.     

Antibiotic resistance in coagulase negative staphylococci isolated from wastewater and drinking water

This study reports the antibiotic resistance patterns of coagulase negative staphylococci (CNS) isolated from a drinking water treatment plant (WTP), a drinking water distribution network, responsible for supplying water to the consumers (WDN), and a wastewater treatment plant (WWTP), responsible for receiving and treating domestic residual effluents. Genotyping and the 16S rRNA gene sequence analysis demonstrated a higher diversity of species both in the WTP (6 species/19 isolates) and WWTP (12 species/47 isolates) than in the WDN (6 species/172 isolates). Staphylococcus pasteuri and Staphylococcus epidermidis prevailed in the WTP and WDN and Staphylococcus saprophyticus in the WWTP. Staphylococci with reduced susceptibility (resistance or intermediary phenotype) to beta-lactams, tetracycline, clindamycin and erythromycin were observed in all types of water and belonged to the three major species groups. The highest resistance rate was found against erythromycin, presumably due to the presence of the efflux pump encoded by the determinant msrA, detected in the majority of the resistant isolates. This study demonstrates that antibiotic resistant CNS may colonize different types of water, namely drinking water fulfilling all the quality standards.     

Occurrence of sulfonamide and tetracycline-resistant bacteria and resistance genes in aquaculture environment

The occurrence of sulfonamide and tetracycline resistance and their pollution profile in the aquaculture environment of Tianjin, northern China, were investigated. The presence of antibiotic-resistant bacteria was identified and the corresponding antibiotic resistance genes (ARGs) were quantified at 6 aquaculture farms in Tianjin. Sulfonamide-resistance genes were prevalent and their concentrations were the highest detected (3.0 × 10⁻⁵ to 3.3 × 10⁻⁴ for sul1/16S rDNA, 2.0 × 10⁻⁴ to 1.8 × 10⁻³ for sul2/16S rDNA) among the various ARGs, most likely because the use of sulfonamides is more prevalent than tetracyclines in this area. Bacillus was the most dominant bacterial genus in both sulfamethoxazole resistant bacteria (63.27% of the total resistant bacteria) and tetracycline-resistant bacteria (57.14% of the total resistant bacteria). At least two of those genes (tetM, tetO, tetT, tetW, sul1 and sul2) were detected in the isolates of Bacillus cereus, Bacillus subtilis, Bacillus megaterium and Acinetobacter lwofii, and all of the above genes were detected in B. cereus, suggesting the occurrence of multi-resistance in the studied area. The genetic transfer of sul1 between intestinal bacteria (e.g., Enterococcus spp.) and indigenous bacteria (e.g., Bacillus spp.) was implied by phylogenetic analysis. Several strains of resistant opportunistic pathogens (e.g., Acinetobacter spp.) were found in indigenous bacteria, which increase the risk of ARGs to public health. Overall, this is the first study to comprehensively investigate the antibiotic resistance profile by analyzing the species of antibiotic-resistant bacteria and adopting qualitative and quantitative methods to investigate ARGs at a typical aquaculture area in northern China.     

Monitoring the quality of mineral bottled water concerning to potential pathogenic bacteria and nitrate levels

The diversity of cultured pathogenic bacteria in the bottled mineral water (BMW) was investigated using selective media. The pure isolates from these selective media, which showed hemolytic activity on the blood agar media and antibiotic resistance, were identified by 16S rRNA gene technique. The seven obtained strains were belonged to the genus Pseudomonas, Bacillus, Acinetobacter, Stenotrophomonas, and Exiguobacterium, and were mostly closed to the pathogenic strains. The increasing of ozone concentration from air-fed ozone generators eliminate the growth of bacteria included the pathogenic bacteria, but in other side it increases the amount of nitrates and nitrites in the final product of the BMW. These findings revealed that the BMW either has potential pathogenic bacteria or high levels of nitrates and all these products may effect on the health of the end user.     

Microbial contamination of main contact surfaces of Automated Teller Machines from Metropolitan Area of Porto

ABSTRACT

Automated Teller Machines (ATM) are likely to be contaminated with various microorganisms because of their contact with the hands of many users daily. The main objective of this study was to investigate ATMs as a potential source of bacterial contamination. This study was conducted in the Metropolitan Area of Porto, in which 50 swab samples were cultured on selective media. Some isolates were identified based on colonial, morphological and biochemical characteristics. Susceptibility to several antibiotics was also evaluated for each isolated organism. Most contaminated ATMs had high numbers of Enterobacteriaceae and Enterococci. Staphylococci and Enterobacteriaceae were the most prevalent bacteria found. The recovered bacterial isolates varied in their antibiotic resistance pattern; Staphylococcus spp. demonstrated the most resistant profiles. With this pioneering study in Portugal, it was demonstrated that although ATMs in metropolitan area of Porto were not highly contaminated, some potentially pathogenic bacteria were present and resistant to some commonly used antibiotics.     

Microbial community functional structure in response to antibiotics in pharmaceutical wastewater treatment systems

It is widely demonstrated that antibiotics in the environment affect microbial community structure. However, direct evidence regarding the impacts of antibiotics on microbial functional structures in wastewater treatment systems is limited. Herein, a high-throughput functional gene array (GeoChip 3.0) in combination with quantitative PCR and clone libraries were used to evaluate the microbial functional structures in two biological wastewater treatment systems, which treat antibiotic production wastewater mainly containing oxytetracycline. Despite the bacteriostatic effects of antibiotics, the GeoChip detected almost all key functional gene categories, including carbon cycling, nitrogen cycling, etc., suggesting that these microbial communities were functionally diverse. Totally 749 carbon-degrading genes belonging to 40 groups (24 from bacteria and 16 from fungi) were detected. The abundance of several fungal carbon-degrading genes (e.g., glyoxal oxidase (glx), lignin peroxidase or ligninase (lip), manganese peroxidase (mnp), endochitinase, exoglucanase_genes) was significantly correlated with antibiotic concentrations (Mantel test; P < 0.05), showing that the fungal functional genes have been enhanced by the presence of antibiotics. However, from the fact that the majority of carbon-degrading genes were derived from bacteria and diverse antibiotic resistance genes were detected in bacteria, it was assumed that many bacteria could survive in the environment by acquiring antibiotic resistance and may have maintained the position as a main player in nutrient removal. Variance partitioning analysis showed that antibiotics could explain 24.4% of variations in microbial functional structure of the treatment systems. This study provides insights into the impacts of antibiotics on microbial functional structure of a unique system receiving antibiotic production wastewater, and reveals the potential importance of the cooperation between fungi and bacteria with antibiotic resistance in maintaining the stability and performance of the systems.     

Bacterial community characteristics under long-term antibiotic selection pressures

To investigate bacterial community characteristics under long-term antibiotic selection pressures, water samples from the upstream and the downstream sections of two rivers individually receiving the treated penicillin G and oxytetracycline production wastewater, as well as the anaerobic and the aerobic effluent of the penicillin G production wastewater treatment plant, were taken and analyzed. Antibiotic resistance ratios of bacterial communities in water samples were estimated by culture-based analysis. The majority of bacterial colonies (approximately 55%-70%) in both downstream rivers and the aerobic effluent showed resistance to 80 μg/ml of antibiotics tested, while the resistance ratios were less than 10% and 5% respectively for both upstream rivers. Six 16S rRNA gene clone libraries were constructed with 355 sequences and 215 OTUs totally obtained representing 465 clones. The antibiotic stresses seemed not reduce the diversities of bacterial communities in antibiotic containing water samples compared to those in the two reference upstream rivers. Bacterial groups present in the two reference upstream rivers were common residents in freshwater ecosystems, with the dominant groups as the phyla Proteobacteria including Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria, as well as Actinobacteria and Bacteroidetes. The phyla Proteobacteria and Firmicutes were dominant in all antibiotic containing water samples, with the clones belonged to Deltaproteobacteria and Epsilonproteobacteria significantly abundant, as well as Gram-positive low GC bacteria in the classes Clostridia and Bacilli. It thus seemed that Deltaproteobacteria, Epsilonproteobacteria, Clostridia and Bacilli might be specifically associated with antibiotic containing environments.     

Antibiotic resistance and antibacterial activity in heterotrophic bacteria of mineral water origin

Antibiotic resistance and antibacterial activity were determined on heterotrophic bacteria isolated from mineral waters. Of the 120 isolates Pseudomonas spp. (55.8%) was the predominant group followed by Acinetobacter spp. (14.17%), Flavobacterium spp. (10.83%), Achromobacter spp. (10%), Burkholderia cepacia (3.3%), Agrobacterium/radiobacter (2.5%), Moraxella spp. (1.7%), Aeromonas hydrophila (1.7%). Over 80% of the isolates were resistant to one or more antibiotics and the highest resistance was found for chloramphenicol, ampicillin, colistin and sulfamethizole (60%, 55%, 50% and 47.5%, respectively). Strains with multiple antibiotic resistance (MAR) represented 55% of isolates and the most resistant organism belonged to the genus Pseudomonas. Of 40 randomly selected strains, 27 (67.5%) had antibacterial activity towards one or more indicators. This activity, found in a high percentage in the genus Pseudomonas (92%), emerged mainly against closely related microorganisms. Several producers were active also against Escherichia coli, Salmonella, Listeria monocytogenes and Staphylococcus aureus. Forty-six percent of the isolates harboured 1 to 5 plasmids with molecular weights ranging from 2.1 to 41.5 MDa.     

First insights into antimicrobial resistance among faecal Escherichia coli isolates from small wild mammals in rural areas

Wild rodents can be carriers of antimicrobial resistant Escherichia coli. As rodents are known to be involved in the transmission of bacteria of human and animal health concern, they could likewise contribute to the dissemination of antimicrobial resistant bacteria in the environment. The aim of this study was therefore to get first insights into the antimicrobial resistance status among E. coli isolated from wild small mammals in rural areas. We tested 188 faecal isolates from eight rodent and one shrew species originating from Germany. Preselected resistant isolates were screened by minimal inhibitory concentration (MIC) testing or agar diffusion test and subsequent PCR analysis of resistance genes. The prevalence of antimicrobial resistant isolates was low with only 5.5% of the isolates exhibiting resistant phenotypes against at least one antimicrobial compound including beta-lactams, tetracyclines, aminoglycosides and sulfonamides.These results suggest a minor role of wild rodents from rural areas in the cycle of transmission and spread of antimicrobial resistant E. coli into the environment. Nevertheless E. coli with multiple antimicrobial resistances were significantly more often detected in wildlife rodents originating from areas with high livestock density suggesting a possible transmission from livestock to wild rodents.