Antibiotic resistant bacteria in Windermere and two remote upland tarns in the English Lake District

The incidence of antibiotic resistance was determined in over 2000 bacteria which were divided into the following groups: faecal streptococci, coliforms (excluding Escherichia coli), E. coli, Pseudomonas spp. and aquatic bacteria (i.e. bacteria predominant in the lake water which were excluded from the previous four categories). The isolates were obtained from the water of Windermere (English Lake District) and from a sewage effluent which entered the lake. With the exception of the faecal streptococci, the incidence of antibiotic resistance was higher in the bacteria isolated from the lake water than in those from the effluent, and ranked according to groups Pseudomonas spp. greater than E. coli greater than aquatic bacteria greater than coliforms greater than faecal streptococci. The highest incidence of multiple resistance was found among the pseudomonads. When corrected for the relative size of each population the pool of antibiotic resistance in the aquatic bacteria was by far the largest. The incidence of antibiotic resistance in aquatic bacteria isolated from Windermere was, however, lower than in those isolated from two remote upland tarns. This finding may have been due to differences in the species composition of the three sites except that the same results were obtained when only fluorescent pseudomonads were tested. The upland tarns were not totally isolated from man and other animals but did not receive any sewage or other effluents and therefore the results were surprising. Possible explanations include a lack of susceptibility in aquatic bacteria and increased resistance associated with growth in nutrient poor environments.     

Antibiotic resistant bacteria in Windermere and two remote upland tarns in the English Lake District

The incidence of antibiotic resistance was determined in over 2000 bacteria which were divided into the following groups: faecal streptococci, coliforms (excluding Escherichia coli ), E. coli, Pseudomonas spp. and aquatic bacteria (i.e. bacteria predominant in the lake water which were excluded from the previous four categories). The isolates were obtained from the water of Windermere (English Lake District) and from a sewage effluent which entered the lake. With the exception of the faecal streptococci, the incidence of antibiotic resistance was higher in the bacteria isolated from the lake water than in those from the effluent, and ranked according to groups Pseudomonas spp. > E. coli > aquatic bacteria > coliforms > faecal streptococci. The highest incidence of multiple resistance was found among the pseudomonads. When corrected for the relative size of each population the pool of antibiotic resistance in the aquatic bacteria was by far the largest. The incidence of antibiotic resistance in aquatic bacteria isolated from Windermere was, however, lower than in those isolated from two remote upland tarns. This finding may have been due to differences in the species composition of the three sites except that the same results were obtained when only fluorescent pseudomonads were tested. The upland tarns were not totally isolated from man and other animals but did not receive any sewage or other effluents and therefore the results were surprising. Possible explanations include a lack of susceptibility in aquatic bacteria and increased resistance associated with growth in nutrient poor environments.     

Olaquindox resistance in the coliform flora of pigs and their environment: an ecological study

Faecal samples were taken weekly from a chosen pen on each of four commercial pig farms, two of which used olaquindox as a feed additive. Coliform bacteria were isolated from the samples and the incidence and level of resistance to olaquindox and to four therapeutic antibiotics determined. The coliforms isolated were biotyped to follow the emergence of drug-resistant sub-populations. The results showed that the coliform flora was complex and that a turnover of biotypes was associated with changes in the occupancy of the pen and, possibly, diet. This turnover led to large fluctuations in both incidence and level of resistance to olaquindox and the antibiotics. Olaquindox resistance was not specifically linked with resistance to any therapeutic antibiotic, and the possible origin of olaquindox-resistant strains is discussed in relation to the biotypes.     

Olaquindox resistance in the coliform flora of pigs and their environment: an ecological study

Faecal samples were taken weekly from a chosen pen on each of four commercial pig farms, two of which used olaquindox as a feed additive. Coliform bacteria were isolated from the samples and the incidence and level of resistance to olaquindox and to four therapeutic antibiotics determined. The coliforms isolated were biotyped to follow the emergence of drug-resistant sub-populations. The results showed that the coliform flora was complex and that a turnover of biotypes was associated with changes in the occupancy of the pen and, possibly, diet. This turnover led to large fluctuations in both incidence and level of resistance to olaquindox and the antibiotics. Olaquindox resistance was not specifically linked with resistance to any therapeutic antibiotic, and the possible origin of olaquindox-resistant strains is discussed in relation to the biotypes.     

Copper amendment of agricultural soil selects for bacterial antibiotic resistance in the field

AIMS: The objective of this study was to determine whether Cu-amendment of field plots affects the frequency of Cu resistance, and antibiotic resistance patterns in indigenous soil bacteria. METHODS AND RESULTS: Soil bacteria were isolated from untreated and Cu-amended field plots. Cu-amendment significantly increased the frequency of Cu-resistant isolates. A panel of isolates were characterized by Gram-reaction, amplified ribosomal DNA restriction analysis and resistance profiling against seven antibiotics. More than 95% of the Cu-resistant isolates were Gram-negative. Cu-resistant Gram-negative isolates had significantly higher incidence of resistance to ampicillin, sulphanilamide and multiple (> or =3) antibiotics than Cu-sensitive Gram-negative isolates. Furthermore, Cu-resistant Gram-negative isolates from Cu-contaminated plots had significantly higher incidence of resistance to chloramphenicol and multiple (> or =2) antibiotics than corresponding isolates from control plots. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this field experiment show that introduction of Cu to agricultural soil selects for Cu resistance, but also indirectly selects for antibiotic resistance in the Cu-resistant bacteria. Hence, the widespread accumulation of Cu in agricultural soils worldwide could have a significant effect on the environmental selection of antibiotic resistance.     

急性脑卒中患者医院感染分析

目的为探明急性脑卒中患者医院感染的特点及危险因素,以便采取有效控制措施。方法对温州医学院附属第一医院1997年1月1日～2002年12月31日6年间收治的4730例急性脑卒中患者进行监测。结果医院感染率为1252%。女性高于男性(P<005),感染率随年龄增大而升高(P<001)。医院感染多发生在入院2周内,感染部位以呼吸道为主(4796%),其次为泌尿道(3481%)。病原菌以G-菌为主(4309%),其次为G+菌(3091%)和真菌(2600%)。耐药菌株不断增加。结论免疫功能低下、侵袭性操作、滥用抗生素和激素是急性脑卒中患者医院感染的主要危险因素。加强对细菌耐药性的监测,合理选用抗生素,是减少或延缓耐药菌株产生的关键措施。     

Spatial Analysis of Antibiotic Resistance Along Metal Contaminated Streams

The spatial pattern of antibiotic resistance in culturable sediment bacteria from four freshwater streams was examined. Previous research suggests that the prevalence of antibiotic resistance may increase in populations via indirect or coselection from heavy metal contamination. Sample bacteria from each stream were grown in media containing one of four antibiotics—tetracycline, chloramphenicol, kanamycin, and streptomycin—at concentrations greater than the minimum inhibitory concentration, plus a control. Bacteria showed high susceptibilities to the former two antibiotics. We summarized the latter two more prevalent (aminoglycoside) resistance responses and ten metals concentrations per sediment sample, by Principal Components Analysis. Respectively, 63 and 58% of the variability was explained in the first principal component of each variable set. We used these multivariate summary metrics [i.e., first principal component (PC) scores] as input measures for exploring the spatial correlation between antibiotic resistance and metal concentration for each stream sampled. Results show a significant and negative correlation between metals PC scores versus aminoglycoside resistance scores and suggest that selection for metal tolerance among sediment bacteria may influence selection for antibiotic resistance differently in sediments than in the water column. Our most important finding comes from geostatistical cross-variogram analysis, which shows that increasing metal concentration scores are spatially associated with decreasing aminoglycoside resistance scores—a negative correlation, but holds for contaminated streams only. We suspect our field results are influenced by metal bioavailability in the sediments and by a contaminant promoted interaction or “cocktail effect” from complex combinations of pollution mediated selection agents.     

Effects of sunlight and Synechocystis sp. (picocyanobacterium) on the incidence of antibiotic resistance in wastewater enteric bacteria

Experimental study of the effects of sunlight and Synechocystis sp. (picocyanobacterium) on the incidence of antibiotic resistance in Salmonella sp. and faecal coliforms (FC), was carried out in wastewaters of Marrakesh stabilization ponds (Morocco). The effect of sunlight was found to be important on the incidence of antibiotic resistance of these enteric bacterial populations. In microcosms seeded with the mixed inoculum (40 different strains) of Salmonella or FC and exposed to sunlight, the overall resistance of these bacteria (72.5 and 57.5% respectively) was significantly higher than that noted in the dark (45 and 32.5% respectively). In microcosms seeded with a monobacterial inoculum, some FC isolates became resistant to the antibiotics cephalothin, amoxicillin or sulphamethoxazole, after their incubation in sunlight. Synechocystis appeared to have no significant effect on the incidence of bacterial antibiotic resistance. The ecological significance of sunlight and Synechocystis sp. in reducing densities and increasing antibiotic resistance of pathogenic bacteria through wastewater stabilization ponds is discussed.     

Distribution and Quantification of Antibiotic Resistant Genes and Bacteria across Agricultural and Non-Agricultural Metagenomes

There is concern that antibiotic resistance can potentially be transferred from animals to humans through the food chain. The relationship between specific antibiotic resistant bacteria and the genes they carry remains to be described. Few details are known about the ecology of antibiotic resistant genes and bacteria in food production systems, or how antibiotic resistance genes in food animals compare to antibiotic resistance genes in other ecosystems. Here we report the distribution of antibiotic resistant genes in publicly available agricultural and non-agricultural metagenomic samples and identify which bacteria are likely to be carrying those genes. Antibiotic resistance, as coded for in the genes used in this study, is a process that was associated with all natural, agricultural, and human-impacted ecosystems examined, with between 0.7 to 4.4% of all classified genes in each habitat coding for resistance to antibiotic and toxic compounds (RATC). Agricultural, human, and coastal-marine metagenomes have characteristic distributions of antibiotic resistance genes, and different bacteria that carry the genes. There is a larger percentage of the total genome associated with antibiotic resistance in gastrointestinal-associated and agricultural metagenomes compared to marine and Antarctic samples. Since antibiotic resistance genes are a natural part of both human-impacted and pristine habitats, presence of these resistance genes in any specific habitat is therefore not sufficient to indicate or determine impact of anthropogenic antibiotic use. We recommend that baseline studies and control samples be taken in order to determine natural background levels of antibiotic resistant bacteria and/or antibiotic resistance genes when investigating the impacts of veterinary use of antibiotics on human health. We raise questions regarding whether the underlying biology of each type of bacteria contributes to the likelihood of transfer via the food chain.     

Association of metal tolerance with multiple antibiotic resistance of bacteria isolated from drinking water.

Bacterial isolates from the drinking water system of an Oregon coastal community were examined to assess the association of metal tolerance with multiple antibiotic resistance. Positive correlations between tolerance to high levels of Cu2+, Pb2+, and Zn2+ and multiple antibiotic resistance were noted among bacteria from distribution waters but not among bacteria from raw waters. Tolerances to higher levels of Al3+ and Sn2+ were demonstrated more often by raw water isolates which were not typically multiple antibiotic resistant. A similar incidence of tolerance to Cd2+ was demonstrated by isolates of both water types and was not associated with multiple antibiotic resistance. These results suggest that simultaneous selection phenomena occurred in distribution water for bacteria which exhibited unique patterns of tolerance to Cu2+, Pb2+, and Zn2+ and antibiotic resistance.     

Association of metal tolerance with multiple antibiotic resistance of bacteria isolated from drinking water

Bacterial isolates from the drinking water system of an Oregon coastal community were examined to assess the association of metal tolerance with multiple antibiotic resistance. Positive correlations between tolerance to high levels of Cu2+, Pb2+, and Zn2+ and multiple antibiotic resistance were noted among bacteria from distribution waters but not among bacteria from raw waters. Tolerances to higher levels of Al3+ and Sn2+ were demonstrated more often by raw water isolates which were not typically multiple antibiotic resistant. A similar incidence of tolerance to Cd2+ was demonstrated by isolates of both water types and was not associated with multiple antibiotic resistance. These results suggest that simultaneous selection phenomena occurred in distribution water for bacteria which exhibited unique patterns of tolerance to Cu2+, Pb2+, and Zn2+ and antibiotic resistance.     

Ap、Km和Cm抗性细菌在土壤中的差异分布及成因

从不同区域土壤中分离细菌：对其进行氨苄青碡素、卡那霉素和氯霉素的抗性测试,以及抗药性质粒分析。结果表明,对照区和生活区土壤细菌抗氨苄青霉素和卡那霉素菌株比例未见显著性差异,未检出抗氯霉素细菌。保护区中抗氨苄青霉素、卡那霉素菌株含质粒比例均为18.2％,生活区中抗氨苄青霉素和卡那霉素菌株含质粒比例分别为36.4％和27．3％。随机抽提质粒转化无抗忡菌,表明部分抗菌素抗性基因是由质粒携带。实验结果认为本地土壤中抗菌素抗性菌分布差异尚未有显著性表现。     

Classification of antibiotic resistance patterns of indicator bacteria by discriminant analysis: use in predicting the source of fecal contamination in subtropical waters

The antibiotic resistance patterns of fecal streptococci and fecal coliforms isolated from domestic wastewater and animal feces were determined using a battery of antibiotics (amoxicillin, ampicillin, cephalothin, chlortetracycline, oxytetracycline, tetracycline, erythromycin, streptomycin, and vancomycin) at four concentrations each. The sources of animal feces included wild birds, cattle, chickens, dogs, pigs, and raccoons. Antibiotic resistance patterns of fecal streptococci and fecal coliforms from known sources were grouped into two separate databases, and discriminant analysis of these patterns was used to establish the relationship between the antibiotic resistance patterns and the bacterial source. The fecal streptococcus and fecal coliform databases classified isolates from known sources with similar accuracies. The average rate of correct classification for the fecal streptococcus database was 62.3%, and that for the fecal coliform database was 63.9%. The sources of fecal streptococci and fecal coliforms isolated from surface waters were identified by discriminant analysis of their antibiotic resistance patterns. Both databases identified the source of indicator bacteria isolated from surface waters directly impacted by septic tank discharges as human. At sample sites selected for relatively low anthropogenic impact, the dominant sources of indicator bacteria were identified as various animals. The antibiotic resistance analysis technique promises to be a useful tool in assessing sources of fecal contamination in subtropical waters, such as those in Florida.     

Antibiotic and heavy metal resistance in Gram-negative bacteria isolated from the Seyhan Dam Lake and Seyhan River in Turkey

This study aimed to determine the pattern of antibiotic and heavy metal resistance in Gram-negative bacteria isolated from five different sites in the Seyhan Dam Lake and Seyhan River in Adana, Turkey. The susceptibility of 268 isolates to 16 different antibiotics and five heavy metals was investigated by agar diffusion and dilution methods, respectively. The most common species isolated from the samples were Aeromonas hydrophila (17.5 %), Aeromonas caviae (8.9 %) and Citrobacter freundii (8.9 %). There was a high incidence of resistance to ampicillin (80.2 %), streptomycin (71.6 %) and cefazolin (60.4 %). Multiple antibiotic resistance indices ranged from 0.2 to 0.81, suggesting exposure to antibiotic contamination. The isolates showed tolerance to different concentrations of heavy metals. These results indicate that antibiotic and heavy metal resistance among the Seyhan Dam Lake and Seyhan River bacteria may pose a risk to the fish population and public health. At the same time, the finding in the aquatic environments of different combinations of resistance genes suggests their involvement in the spread of multidrug-resistant strains.     

Antibiotic resistance of native and faecal bacteria isolated from rivers, reservoirs and sewage treatment facilities in Victoria, south-eastern Australia

The incidence of resistance to ampicillin, chloramphenicol, kanamycin, nalidixic acid, neomycin and streptomycin was significantly greater (P < 0.001) in native heterotrophic bacteria than in Escherichia coli isolated from a range of sites along the Yarra River in south-eastern Australia. There was no significant difference in the incidence of resistance between native and faecal bacteria to tetracycline. Both groups were almost totally resistant to penicillin. Multivariate analyses indicated little clear spatial pattern in the incidence of resistance in native bacteria from upstream vs downstream sites along the Yarra River. In contrast, E. coli isolated from upstream (rural) sites tended to have a lower incidence of resistance than isolates from downstream (urban) sites. These findings have implications for the use of antibiotic resistance as a bacteriological water quality parameter.     

Antimicrobial resistance of bacteria isolated from slaughtered and retail chickens in South Africa

Animal feed is increasingly being supplemented with antibiotics to decrease the risk of epidemics in animal husbandry. This practice could lead to the selection for antibiotic resistant micro-organisms. The aim of this study was to determine the level of antibiotic resistant bacteria present on retail and abattoir chicken. Staphylococci, Enterobacteriaceae, Salmonella and isolates from total aerobic plate count were tested for resistance to vancomycin, streptomycin, methicillin, tetracycline and gentamicin using the disc diffusion susceptibility test; resistance to penicillin was determined using oxacillin. Results from the antibiotic code profile indicated that many of the bacterial strains were displaying multiple antibiotic resistance (MAR). A larger proportion of resistance to most antibiotics, except for vancomycin, was displayed by the abattoir samples, therefore suggesting that the incidence of MAR pathogenic bacteria was also higher in the abattoir samples. This resistance spectrum of abattoir samples is a result of farmers adding low doses of antibiotics to livestock feed to improve feeding efficiency so that the animals need less food to reach marketable weight. The lower incidence of MAR pathogenic bacteria in the retail samples is a result of resistance genes being lost due to lack of selective pressure, or to the fact that the resistant flora are being replaced by more sensitive flora during processing. The use of subtherapeutic levels of antibiotics for prophylaxis and as growth promoters remains a concern as the laws of evolution dictate that microbes will eventually develop resistance to practically any antibiotic. Selective pressure exerted by widespread antimicrobial use is therefore the driving force in the development of antibiotic resistance. This study indicated that a large proportion of the bacterial flora on fresh chicken is resistant to a variety of antibiotics, and that resultant food-related infections will be more difficult to treat.     

Occurrence and patterns of antibiotic resistance in vertebrates off the Northeastern United States coast

The prevalence of antibiotic-resistant bacteria in the marine environment is a growing concern, but the degree to which marine mammals, seabirds and fish harbor these organisms is not well documented. This project sought to identify the occurrence and patterns of antibiotic resistance in bacteria isolated from vertebrates of coastal waters in the northeastern United States. Four hundred and seventy-two isolates of clinical interest were tested for resistance to a suite of 16 antibiotics. Fifty-eight percent were resistant to at least one antibiotic, while 43% were resistant to multiple antibiotics. A multiple antibiotic resistance index value ≥0.2 was observed in 38% of the resistant pathogens, suggesting exposure of the animals to bacteria from significantly contaminated sites. Groups of antibiotics were identified for which bacterial resistance commonly co-occurred. Antibiotic resistance was more widespread in bacteria isolated from seabirds than marine mammals, and was more widespread in stranded or bycaught marine mammals than live marine mammals. Structuring of resistance patterns based on sample type (live/stranded/bycaught) but not animal group (mammal/bird/fish) was observed. These data indicate that antibiotic resistance is widespread in marine vertebrates, and they may be important reservoirs of antibiotic-resistant bacteria in the marine environment.     

Incidence of Infectious Drug Resistance Among Fecal Coliforms Isolated from Raw Sewage

Raw sewage was examined for the incidence of antibiotic-resistant coliforms present among both total and fecal coliforms. In both groups, it was found that approximately 3% of the coliform bacteria were resistant to two or more antibiotics. Of these organisms, 48% were capable of transferring all or part of their antibiotic resistance to an antibiotic-sensitive, F⁻, derivative of Escherichia coli K-12. Among the R factors identified, those conferring resistance to streptomycin-tetracycline, ampicillin-streptomycin-tetracycline, and ampicillin or ampicillin-streptomycin accounted for 23, 20, and 15%, respectively, of the total R factors detected. The data indicate a significant level of infectious drug resistance among the fecal coliforms of the urban population. The data indicate further that because of the high incidence of coliform bacteria found to be doubly resistant to streptomycin and tetracyline, the inclusion of these antibiotics in selective media used for routine total or fecal coliform counts may serve to identify domestic sources of pollution.     

老年患者血培养病原菌分布及耐药性调查

目的了解老年患者血液感染的病原菌种类以及对抗菌药物的耐药状况。方法对2290份老年住院患者血培养标本中186例培养阳性检出菌及药敏结果进行统计学分析。结果在分离的172株细菌中,革兰阴性菌、革兰阳性菌及真菌分别占54.7%、34.9%和10.5%;革兰阴性菌中以大肠埃希菌占绝对优势(20.9%),假单胞菌其次(10.5%),革兰阳性菌中以凝固酶阴性葡萄球菌(CNS)占绝对优势(20.9%),金黄色葡萄球菌仅为2.9%。药敏试验表明老年菌血症的病原菌对常用抗菌药物的耐药严重,尤其是CNS及假单胞菌属细菌表现为较高的耐药率及多重耐药性。结论老年菌血症病原菌以机会致病菌感染比例较高,致病菌耐药问题严重,及时监测老年致病菌的变迁和耐药发展趋势以指导临床用药至关重要。