Sadik Dincer

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 microg/ml to > 3200 microg/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.

Distribution and antibacterial drug resistance ofAeromonas spp. from fresh and brackish waters in Southern Turkey

The frequency of antibiotic resistance was compared inAeromonas spp. isolated from fresh and brackish water in Southern Turkey. A total of 97Aeromonas spp. strains were isolated from four zones (three from fresh and one from brackish water). Most of the strains isolated from all samples wereAeromonas hydrophila (79.4%), while the amount ofAeromonas sobria andAeromons caviae, were rather lower in the samples examined (17.5% and 3.1% respectively). A high proportion of isolates from all water sources showed resistance to cephalotin (86.6%) and trimethoprim-sulphamethoxazole (69%). On the other hand, a low proportion of bacteria showed resistance to tetracycline (14.4%), chloramphenicol (11.3%), gentamicin (7.2%) and nitrofurantoin (6.8%). Only one strain showing resistance to amikacin was found. Multiple Antibiotic Resistance Index (MARI) to at least two antibiotics was highest in brackish water (zone 4), followed by fresh water (zone 3). MARI values ranging from 0.2 to 0.8 for the bacteria isolated from brackish water. This study suggest that, multiple antibiotic resistantAeromonas spp., especiallyA. hydrophila, can be easily recovered from fresh and brackish water sources in Turkey and these sources may play as a reservoirs responsible for disease pathogen aeromonads.

Production and Characterization of Phytase from Lactobacillus plantarum

Phytase was produced from Lactobacillus plantarum isolated from a fermented food (Shalgam) and characterized in this study. Extracellular and intracellular enzyme activities of L. plantarum were determined as 984.50 U/mL and 494 U/g, respectively. Molecular weight of extracellular phytase from L. plantarum was estimated to be 46 kDa, and intracellular phytases were estimated to be 72 kDa, 36 kDa, and 33 kDa by SDS-PAGE. Optimum temperature for extracellular and intracellular phytase activity was 120°C, and optimum pH for extracellular and intracellular phytase activity was pH 3.4. The intracellular enzyme was 94% stable for 10 min at 80°C. The extracellular enzyme activity was not significantly affected by 1 mM CoCl2 and 1mM FeCl2. Intracellular enzyme activity was not significantly affected by 5 mM MnCl2.

Degradation of 2,4,6-trinitrotoluene by P. aeruginosa and characterization of some metabolites.

Degradation of 2,4,6-trinitrotoluene (TNT), a nitroaromatic explosive found in the soil and ground water, was investigated using Pseudomonas aeruginosa in in vitro experiments . Biodegradable abilitiy of this bacteria was performed with 50 and 75 mg L −1 TNT concentrations in a defined liquid medium for 96 h time period. Treatment of TNT in supernatant samples taken at 0, 6, 12, 24, 48, 72 and 96 h from agitated vessels was followed by reverse-phase high-performance liquid chromatography (HPLC). In cultures supplemented with 50 and 75 mgL −1 TNT, after 96 h of incubation 46% and 59% reduction were detected respectively. Two metabolites as degradation intermediates with nitrite release into the medium, 2,4-dinitrotoluene (2,4-DNT) and 4-aminodinitrotoluene (4-ADNT), were elucidated by thin layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). These findings clearly indicate that Pseudomonas aeruginosa can be used in bioremediation of TNT contaminated sites.

Spreading of Antibiotic Resistance with Wastewater

The recent statistics show that the worlds population is rapidly increasing. This increase negatively affects the water resources and it increases the water demand progressively. Along with the increase in the worlds population, the insensible use of water resources, pollution, and drought lead to the increasing reduction of water resources. Due to these factors, all countries, primarily developed countries, have started looking for new water resources. This search has been extended to extraterrestrial water. However, the exist‐ ing technology and opportunities direct countries toward the purification of wastewater rather than searching for new water resources. For the reasons outlined above, purifica‐ tion and recycling of wastewater become important. In addition to the natural resistance of microorganisms against antibiotics, a resistance also arises because of the unconscious and overuse of antibiotics. This resistance spreads through wastewater progressively. Antibiotic resistance shows an increase according to the scientific data. In order to prevent the resistance, it is of capital importance to treat the wastewater in which the domestic pollution burden is high. In this study, the role of domestic wastewater in the occurrence and spread of antibiotic resistance will be revealed.