Detection of heavy metal ion resistance genes in Gram-positive and Gram-negative bacteria isolated from a lead-contaminated site

Resistance to a range of heavy metal ions wasdetermined for lead-resistant and other bacteria whichhad been isolated from a battery-manufacturing sitecontaminated with high concentrations of lead. Several Gram-positive (belonging to the genera Arthrobacter and Corynebacterium) andGram-negative (Alcaligenes species) isolateswere resistant to lead, mercury, cadmium, cobalt,zinc and copper, although the levels of resistance tothe different metal ions were specific for eachisolate. Polymerase chain reaction, DNA-DNAhybridization and DNA sequencing were used to explorethe nature of genetic systems responsible for themetal resistance in eight of the isolates. SpecificDNA sequences could be amplified from the genomic DNAof all the isolates using primers for sections of themer (mercury resistance determinant on thetransposon Tn501) and pco (copperresistance determinant on the plasmid pRJ1004) geneticsystems. Positive hybridizations with mer andpco probes indicated that the amplified segmentswere highly homologous to these genes. Some of thePCR products were cloned and partially sequenced, andthe regions sequenced were highly homologous to theappropriate regions of the mer and pcodeterminants. These results demonstrate the widedistribution of mercury and copper resistance genes inboth Gram-positive and Gram-negative isolates obtainedfrom this lead-contaminated soil. In contrast, theczc (cobalt, zinc and cadmium resistance) andchr (chromate resistance) genes could not beamplified from DNAs of some isolates, indicating thelimited contribution, if any, of these genetic systemsto the metal ion resistance of these isolates.     

Disinfectant tolerance and antibiotic resistance in psychrotrophic Gram-negative bacteria isolated from vegetables

A total of 330 strains of psychrotrophic non-fermenting Gram-negative bacteria isolated from vegetables were studied. In spite of the wide range of antibiotic resistance occurring, less than 10% showed resistance patterns which included mezclocillin-ticarcillin-gentamicin or ceftizoxime-norfloxacin. Reductions of > 5 log₁₀ in the numbers of cfu were found when these strains were exposed for 30 min to a quaternary ammonium compound (1% w/v).     

Antibiotic resistance among coliform bacteria isolated from hospital and urban wastewaters

The mean count of coliforms/ml in urban and hospital drains were 68.9×10⁴ and 48.4×10⁴, respectively.Klebsiella predominated amongst the 16 coliform species that were differentiated;Escherichia coli occurred with highest frequency. All the isolates were resistant to at least one antibiotic and resistance to ampicillin, tetracycline, and chloramphenicol was particularly high. Multiple antibiotic resistant strains were common in both environments—85% and 65% for hospital and urban sources, respectively. The difference in the frequency of resistant strains from the two sources was not significant. 20% of strains from the two sources were multiply resistant to six antibiotics. The role of untreated wastewater in the maintenance and dissemination of resistant coliforms and its public health significance are highlighted.

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Résumé Le comptage moyen de coliformes par ml dans des égouts urbains ou d'hôpital était respectivement de 68.9 10⁴ et de 48.4 10⁴.Kiebsiella prédominait parmi les 16 espèces de coliformes différenciées;Escherichia coli apparaissait avec la fréquence la plus élevée. Tours les isolats étaient résistants à au moins un antibiotique et la résistance à l'ampicilline, la tetracycline et le chloramphénicol était particulièrement élevée. Des souches résistantes à plusieurs antibiotiques étaient communes dans les deux environnements—85% et 65% respectivement pour les origines urbaines et d'hôpital. La différence dans la fréquence de souches résistantes provenant des deux origines n'était pas significative. Vingt pour-cent des souches provenant des deux origines présentaient une résistance multiple aux six antibiotiques. On a mis en évidence le rôle de l'eau résiduaire non traitée dans le maintien et la dissémination de coliformes résistants et de sa signification pour la santé publique.

     

Antibiotic resistance of coryneform bacteria isolated from the reproductive tract of women

The species composition, antilysozyme activity and antibiotic resistance of coryneform bacteria, isolated from the reproductive tract of women with microecological disturbances, were studied. Sixty six women without microecological disturbances and 102 female patients with microecological disturbances in the reproductive tract were examined. The study showed that Corynebacterium minutissimum, C. amycolatum, C. group JK, C. bovis and C. pseudodiphtheriticum prevailed in the healthy women. In the patients with microecological disturbances in the reproductive tract C. vitarumen, C. matruchotii, C. striatum, C. renale and C. urealyticum were detected in addition to the above species. The average antilysozyme activity of the coryneform bacteria isolated from the healthy women was 1.32 +/- 0.47. In the patients with microecological disturbances in the reproductive tract it was 1.84 +/- 0.38. The in vitro susceptibility of the coryneform bacteria to antimicrobial agents was determined. High prevalence of resistance to beta-lactams (oxacillin and penicillin), erythromycin and co-trimoxazole was detected. Thus, the species variety and the antilysozyme activity of the coryneform bacteria in the reproductive tract of the women with microecological disturbances were found to be higher. The high prevalence of resistance to oxacillin, penicillin, erythromycin and co-trimoxazole in the coryneform bacteria isolated from the patients with the microecological disturbances did not differ from that in the healthy women.     

Antibiotic resistance patterns of gram-negative bacteria isolated from environmental sources.

A total of 2,445 gram-negative bacteria belonging to fecal coliform, Pseudomonas, Moraxella, Acinetobacter, and Flavobacterium-Cytophaga groups were isolated from the rivers and bay of Tillamook, Oregon, and their resistances to chloramphenicol (25 microgram/ml), streptomycin (10 microgram/ml), ampicillin (10 microgram/ml), tetracycline (25 microgram/ml), chlortetracycline (25 microgram/ml), oxytetracycline (25 microgram/ml), neomycin (50 microgram/ml), nitrofurazone (12.5 microgram/ml), nalidixic acid (25 microgram/ml), kanamycin (25 microgram/ml), and penicillin G (10 IU/ml) were determined. Among fecal coliforms the bay isolates showed greater resistance to antibiotics than those from tributaries or surface runoff. No such well-defined difference was found among other bacterial groups. The antibiotic resistance patterns of gram-negative bacteria from different sources correlated well, perhaps indicating their common origin. The antibiotic resistance patterns of gram-negative bacteria of different general also correlated well, perhaps indicating that bacteria which share a common environment also share a common mode for developing antibiotic resistance.     

Molecular characterization of antimicrobial resistance in Gram-negative bacteria isolated from bovine mastitis in Egypt

The aim of this study was to characterize the genetic basis of multidrug resistance in Gram-negative bacteria isolated from bovine mastitis cases in Egypt. Multidrug resistance phenotypes were found in 34 of 112 (30.4%) Gram-negative bacterial isolates, which harbored at least one antimicrobial resistance gene. The most prevalent multidrug-resistant (MDR) species were Enterobacter cloacae (8 isolates, 7.1%), Klebsiella pneumoniae (7 isolates, 6.3%), Klebsiella oxytoca (7 isolates, 6.3%), Escherichia coli (5 isolates, 4.5%), and Citrobacter freundii (3 isolates, 2.7%). The most commonly observed resistance phenotypes were against ampicillin (97.0%), streptomycin (94.1%), tetracycline (91.2%), trimethoprim-sulfamethoxazole (88.2%), nalidixic acid (85.3%), and chloramphenicol (76.5%). Class 1 integrons were detected in 28 (25.0%) isolates. The gene cassettes within class 1 integrons included those encoding resistance to trimethoprim (dfrA1, dfrA5, dfrA7, dfrA12, dfrA15, dfrA17, and dfrA25), aminoglycosides (aadA1, aadA2, aadA5, aadA7, aadA12, aadA22, and aac(3)-Id), chloramphenicol (cmlA), erythromycin (ereA2), and rifampicin (arr-3). Class 2 integrons were identified in 6 isolates (5.4%) with three different profiles. Furthermore, the β-lactamase encoding genes, bla(TEM), bla(SHV), bla(CTX-M), and bla(OXA), the plasmid-mediated quinolone resistance genes, qnr and aac(6)-Ib-cr, and the florfenicol resistance gene, floR, were also identified. To the best of our knowledge, the results identified class 2 integrons, qnr and aac(6)-Ib-cr from cases of mastitis for the first time. This is the first report of molecular characterization for antimicrobial resistance in Gram-negative bacteria isolated from bovine mastitis in Africa.     

Age,growth and sex ratio of tench Tinca tinca (L., 1758) in Seyhan Dam Lake,Turkey

The study investigated the age, growth and sex ratio of Tinca tinca L., 1758 in Seyhan Dam Lake, Turkey and determined its first population structure data in the lake. Fishermen had introduced tinca into the lake between 2001 and 2002. A total of 1284 T. tinca (778 males and 506 females) were captured between January and December 2007 by gill nets of various mesh sizes. The sex ratio was 1 : 1.53 females to males. Total lengths and weights ranged from 12 to 29 cm and 27 to 403.3 g. Ages in both sexes ranged from 1 to 5 years. For all individuals the length‐weight relation and von Bertalanffy growth parameters were W = 0.063 × L^2.51 (r = 0.981), and L = 50.86 cm, k = 0.112 year^?1, t_o = ?1.551 year.     

Multidrug resistance in Gram-negative bacteria

Broadly specific, so-called multidrug, efflux mechanisms are now known to contribute significantly to intrinsic and acquired multidrug resistance in a number of Gram-negative bacteria, and the boom in bacterial genomics has confirmed the distribution of these systems in all bacteria. This broad distribution of multidrug transporters lends a certain credibility to suggestions that they play a housekeeping role in the cell, beyond any contributions they may make to antimicrobial efflux and resistance. In many instances, these transporters are dispensable, arguing against their carrying out essential cellular functions; nevertheless, the multiplicity of these broadly specific export systems within a given microorganism, often with overlapping substrate specificity, may explain the dispensability of individual exporters. Whatever their intended function, however, their conservation in so many organisms highlights their probable general importance in antimicrobial resistance, particularly in Gram-negative bacteria whose outer membranes work synergistically with many of these export systems to promote drug exclusion.     

Antibiotic resistance genes in anaerobic bacteria isolated from primary dental root canal infections

Fourty-one bacterial strains isolated from infected dental root canals and identified by 16S rRNA gene sequence were screened for the presence of 14 genes encoding resistance to beta-lactams, tetracycline and macrolides. Thirteen isolates (32%) were positive for at least one of the target antibiotic resistance genes. These strains carrying at least one antibiotic resistance gene belonged to 11 of the 26 (42%) infected root canals sampled. Two of these positive cases had two strains carrying resistance genes. Six out of 7 Fusobacterium strains harbored at least one of the target resistance genes. One Dialister invisus strain was positive for 3 resistance genes, and 4 other strains carried two of the target genes. Of the 6 antibiotic resistance genes detected in root canal strains, the most prevalent were blaTEM (17% of the strains), tetW (10%), and ermC (10%). Some as-yet-uncharacterized Fusobacterium and Prevotella isolates were positive for blaTEM, cfxA and tetM. Findings demonstrated that an unexpectedly large proportion of dental root canal isolates, including as-yet-uncharacterized strains previously regarded as uncultivated phylotypes, can carry antibiotic resistance genes.     

Length–weight relationships for 12 fish species caught in Seyhan Dam Lake in southern Anatolia, Adana, Turkey

Presented are the length–weight relationships of 12 fish species [ Oncorhynchus mykiss (Walbaum, 1792); Cyprinus carpio, Linnaeus, 1758; Carassius carassius Linnaeus, 1758; Alburnoides bipunctatus (Bloch, 1782); Alburnus adanensis Battalgazi, 1944; Rutilus rutilus , Linnaeus, 1758; Squalis cephalus, Linnaeus, 1758; Tinca tinca (Linnaeus, 1758); Capoeta barroisi (Valenciennes, 1842); Silurus glanis Linnaeus, 1758; Gambussia affinis (Baird and Girard, 1853); and Sander lucioperca (Linnaeus, 1758)] from Seyhan Dam Lake, Turkey. This study provides the first estimation of length–weight relationships for two of the species ( A.   adanensis and C. barroisi ).     

Co-occurrence of antibiotic,biocide, and heavy metal resistance genes in bacteria from metal and radionuclide contaminated soils at the Savannah River Site

Contaminants such as heavy metals may contribute to the dissemination of antimicrobial resistance (AMR) by enriching resistance gene determinants via co-selection mechanisms. In the present study, a survey was performed on soils collected from four areas at the Savannah River Site (SRS), South Carolina, USA, with varying contaminant profiles: relatively pristine (Upper Three Runs), heavy metals (Ash Basins), radionuclides (Pond B) and heavy metal and radionuclides (Tim’s Branch). Using 16S rRNA gene amplicon sequencing, we explored the structure and diversity of soil bacterial communities. Sites with legacies of metal and/or radionuclide contamination displayed significantly lower bacterial diversity compared to the reference site. Metagenomic analysis indicated that multidrug and vancomycin antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) including those associated with copper, arsenic, iron, nickel and zinc were prominent in all soils including the reference site. However, significant differences were found in the relative abundance and diversity of certain ARGs and MRGs in soils with metal/radionuclide contaminated soils compared to the reference site. Co-occurrence patterns revealed significant ARG/MRG subtypes in predominant soil taxa including Acidobacteriaceae, Bradyrhizobium, Mycobacterium, Streptomyces, Verrumicrobium, Actinomadura and Solirubacterales. Overall, the study emphasizes the potential risk of human activities on the dissemination of AMR in the environment.     

Antimicrobial resistance in Gram-negative bacilli isolated from infant formulas

A total of 90 samples of infant formula (IF) were collected from the lactary of a teaching hospital, during a 4-month period from July to August 1999. The sanitary conditions of the formulas were analyzed, and a physiological characterization of Gram-negative bacillus isolates and antimicrobial susceptibility testing were performed. Colony counts were considered to be unacceptable for the majority of the IF samples and the contamination rates were related to inadequate handling. Coliforms (35 degrees C and 45 degrees C growth) were detected in most of the IF tested. Klebsiella pneumoniae, Citrobacter freundii, Cedacea davisae, Klebsiella planticola and Enterobacter cloacae were the isolates most commonly identified. Antimicrobial susceptibility testing showed significant resistance rates, particularly to amoxicillin/clavulanic acid, cefoxitin, cephalotin or ampicillin. One extended-spectrum beta-lactamase-producing K. pneumoniae strain was also recovered.     

Antibiotic resistance patterns of coagulase-negative staphylococcus strains isolated from blood cultures of septicemic patients in Turkey

The aim of this study is to determine antibiotic resistance patterns and slime production characteristics of coagulase-negative Staphylococci (CoNS) caused nosocomial bacteremia. A total of 200 CoNS strains were isolated from blood samples of patients with true bacteremia who were hospitalized in intensive care units and in other departments of Istanbul University Cerrahpasa Medical Hospital between 1999 and 2006. Among 200 CoNS isolates, Staphylococcus epidermidis was the most prevalent species (87) followed by Staphylococcus haemolyticus (23), Staphylococcus hominis (19), Staphylococcus lugdunensis (18), Staphylococcus capitis (15), Staphylococcus xylosus (10), Staphylococcus warneri (8), Staphylococcus saprophyticus (5), Staphylococcus lentus (5), Staphylococcus simulans (4), Staphylococcus chromogenes (3), Staphylococcus cohnii (1), Staphylococcus schleiferi (1), and Staphylococcus auricularis (1). Resistance to methicillin was detected in 67.5% of CoNS isolates. Methicillin-resistant CoNS strains were determined to be more resistant to antibiotics than methicillin-susceptible CoNS strains. Resistance rates of methicillin-resistant and methicillin-susceptible CoNS strains to the antibacterial agents, respectively, were as follows: gentamicin 90% and 17%, erythromycin 80% and 37%, clindamycin 72% and 18%, trimethoprim-sulfamethoxazole 68% and 38%, ciprofloxacin 67% and 23%, tetracycline 60% and 45%, chloramphenicol 56% and 13% and fusidic acid 25% and 15%. None of the strains were resistant to vancomycin and teicoplanin. Slime production was detected in 86 of 200 CoNS strains. Resistance to methicillin was found in 81% of slime-positive and in 57% of slime-negative strains. Our results indicated that there is a high level of resistance to widely used agents in causative methicillin-resistant CoNS strains. However fusidic acid has the smallest resistance ratio, with the exception of glycopeptides. Additionally, most S. epidermidis strains were slime-positive, with statistically significant (p<0.001) association between methicillin resistance and slime production.     

Antibiotic resistance of staphylococci isolated from outpatients

The aim of the study was to determine susceptibility of 587 strains of S. aureus and 85 strains of coagulase-negative staphylococci isolated from outpatients in Poznań to co-trimoxazole, amoxycillin/clavulanic acid, erythromycin, gentamycin, doxycycline, ampicillin, oxacillin, cephradine, clindamycin and neomycin. Also methicillin-resistant strains were determined as well as strains ability to produce beta-lactamases. Susceptibility testing and examination of methicillin-resistant strains were performed by the disc diffusion techniques according to recommendation of NCCLS. Methicillin-resistant strains were additionally examined to their sensitivity to vankomycin and teicoplanin. beta-lactamase production was detected using nitrocefin impregnated discs and iodometric method. Amoxacillin/clavulanic acid, gentamycin, co-trimoxazole, cephradin, oxacillin and clindamycin occurred to be very active against both, S. aureus and coagulase-negative staphylococci. 84.7% to 100% of examined strains were sensitive to these drugs. Doxycyclin, erythromycin and ampicillin were less effective. Nine strains (1.5%) of 587 strains of S. aureus as well as 7 strains (8.7%) of coagulase-negative staphylococci were methicillin-resistant. All of methicillin-resistant strains were sensitive to vancomycin and teicoplanin. More than 75% of S. aureus and close to 50% of coagulase-negative staphylococci were able to produce beta-lactamases.     

Efflux pumps and drug resistance in Gram-negative bacteria

The outer membrane of Gram-negative bacteria can only slow down the influx of lipophilic inhibitors, and so these bacteria need active efflux pumps of broad specificity to survive. Pumps such as the Escherichia coli Acr system and its homologs make Gram-negative bacteria resistant to dyes, detergents and antibiotics.     

Multidrug resistance in hydrocarbon-tolerant Gram-positive and Gram-negative bacteria

New Gram-positive and Gram-negative bacteria were isolated from Poeni oily sludge, using enrichment procedures. The six Gram-positive strains belong to Bacillus, Lysinibacillus and Rhodococcus genera. The eight Gram-negative strains belong to Shewanella, Aeromonas, Pseudomonas and Klebsiella genera. Isolated bacterial strains were tolerant to saturated (i.e., n-hexane, n-heptane, n-decane, n-pentadecane, n-hexadecane, cyclohexane), monoaromatic (i.e., benzene, toluene, styrene, xylene isomers, ethylbenzene, propylbenzene) and polyaromatic (i.e., naphthalene, 2-methylnaphthalene, fluorene) hydrocarbons, and also resistant to different antimicrobial agents (i.e., ampicillin, kanamycin, rhodamine 6G, crystal violet, malachite green, sodium dodecyl sulfate). The presence of hydrophilic antibiotics like ampicillin or kanamycin in liquid LB-Mg medium has no effects on Gram-positive and Gram-negative bacteria resistance to toxic compounds. The results indicated that Gram-negative bacteria are less sensitive to toxic compounds than Gram-positive bacteria, except one bacteria belonging to Lysinibacillus genus. There were observed cellular and molecular modifications induced by ampicillin or kanamycin to isolated bacterial strains. Gram-negative bacteria possessed between two and four catabolic genes (alkB, alkM, alkB/alkB1, todC1, xylM, PAH dioxygenase, catechol 2,3-dioxygenase), compared with Gram-positive bacteria (except one bacteria belonging to Bacillus genus) which possessed one catabolic gene (alkB/alkB1). Transporter genes (HAE1, acrAB) were detected only in Gram-negative bacteria.     

Antibiotic activity of epiphytic bacteria isolated from intertidal seaweeds

A survey of antibiotic-producing bacteria from the microbial flora attached to seaweeds and the study of their antibiotic capacities were carried out. From 5 species of green and brown marine algae, 224 bacterial strains were isolated and tested for antibiotic production. A total of 38 strains displayed antibiotic activity, withEnteromorpha intestinalis being the source of the highest number of producer strains. All epiphytic bacteria with antibiotic activity were assigned to thePseudomonas-Alteromonas group. Antagonism assays among the isolates demonstrated that each producer strain inhibits the growth of the other producers, as well as of some nonproducer strains also isolated from seaweeds. Likewise, an autoinhibitory effect was observed in all antibiotic-producing strains. Antibacterial spectra of all the strains include activity againstStaphylococcus, Alcaligenes, Pseudomonas, Vibrio, Pasteurella, andAchromobacter. A preliminary characterization of the antibiotic substances produced by these epiphytic bacteria demonstrated that they are low molecular weight compounds, thermolabile, and anionic and are not affected by proteolytic enzymes. The role that these inhibitory substances can play in the natural environment is discussed.