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The accumulation of arsenic (As) and physiological responses of Lemna minor L. under different concentration (0, 1, 4, 16 and 64 microM) and duration (1, 2, 4 and 6 days) of two species As, NaAsO(2) and Na(2)HAsO(4).7H(2)O, were studied in hydroponics. The accumulation of both As species depended on As concentration and exposure duration. The highest accumulation of As was found as 17408 and 8674 microg g(-1), for plants exposed to 64 microM of As(III) and As(V), respectively, after 6 days. Two-way ANOVA analyses indicated that, for plants exposed to arsenite (As(III)), exposure duration had a greater effect than concentration on As accumulation. Conversely, exposure concentration had a greater effect on As accumulation in plants exposed to arsenate (As(V)). Arsenic exposure levels, approaching 16 microM for As(III) and 64 microM for As(V), did not significantly affect EC values. Beyond these exposure concentrations, EC values increased in a manner that depended on duration. Significant effect of As(III) on lipid peroxidation was observed at 1 microM application whereas, this effect started to be significant after an exposure to 16 microM As(V). For both As(III) and As(V), photosynthetic pigment levels slightly increased for the first day with respect to the control, followed by a gradual decline at higher concentrations and durations. An increase in protein content and enzyme activity was observed at moderate exposure conditions, followed by a decrease. Significant positive correlations were determined between accumulated As and ion leakage and lipid peroxidation. Negative correlations were found between accumulated As and total chlorophyll and protein content. Our results suggested that exposure duration and concentration had a strong synergetic effect on antioxidant enzyme activity. The findings of the present study may be useful when this plant is used as a phytoremediator in arsenic-polluted water.

In this study, the susceptibility of larvae and adults of Tribolium castaneum (Herbst) to gamma radiation was investigated in the laboratory in Turkey. Gamma radiation was applied at 6 dose levels between 20 and 200 Gy to 13-15 day-old adults and at 5 dose levels between 20 and 180 Gy to 18-20 day-old larvae of T. castaneum. All experiments were performed in growth chambers maintained at 27 ± 1°C and 70 ± 5 % r.h. The larvae proved to be the more susceptible stage, survival to the adult stage being prevented by exposure of the eggs to 100 Gy; the adult stage was less susceptible. LD 50 and LD 99 values were determined as 19,75 and 42,97 Gy for larvae and 33,21 and 64,50 Gy for adult stage, respectively. It was concluded that 100 Gy is the effective dose for both larval and adult stages.

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In this study, coagulase negative staphylococci (CoNS) (n = 70) isolated from subclinical sheep mastitis were screened for minimum inhibitory concentration (MIC) to antimicrobials used commonly in veterinary field in Turkey. In addition, plasmid profiling and biofilm production of CoNS isolates was investigated. All isolates were found to be susceptible to amoxycillin-clavulanic acid, cephalothin, gentamicin, enrofloxacin and oxacillin. The highest resistance was observed in 42.9% (n = 30) of the isolates against the beta-lactam antibiotics, penicillin and ampicillin. All beta-lactam resistant isolates produced beta-lactamase and carried blaZ. Tetracycline resistance was observed in 11.4% (n = 8) of the isolates, either alone or in combination with beta-lactams and macrolides. Of the tetracycline resistant 8 isolates, 5 carried the tetK gene, one carried the tetM and 2 isolates carried both genes together. Erythromycin resistance was observed in 5.7% of the isolates; msrA was detected alone (one isolate) or in combination with mphC (one isolate) and ermC (one isolate). ermA was observed only in one isolate. Most of the strains showed only a single plasmid band in size of 19.3 kb, but some had 2 to 3 plasmids ranging from >19.3 kb to 0.9 kb. Out of 70 CoNS isolates, 28 (40%) were identified as biofilm producer by Congo red agar (CRA) method, and 30 (42.9%) were positive for both icaA and icaD genes, which are known to be responsible for biofilm formation in CoNS. ÖzetBu çalışmada, subklinik koyun mastitislerinden izole edilen koagulaz negatif stafilokokların (KNS) (n = 70) veteriner hekimlik alanında yaygın olarak kullanılan antimikrobiyallere minimal inhibitor konsantrasyonları (MİK), plazmid profilleri ve biyofilm üretimi araştırıldı. Tüm izolatlar amoksisilin-klavulanik asid, cefalotin, gentamisin, enrofloksasin ve oksasiline duyarlı bulundu. En yüksek direnç izolatların %42.9'unda (n = 30) beta-laktam antibiyotiklere (penisilin ve ampisilin) karşı gözlendi. Beta-laktam antibiyotiklere dirençli izolatların tamamı beta-laktamaz sentezlediği ve blaZ genini taşıdığı belirlendi. Tetrasiklin direnci tek veya beta-laktam antibiyotikler ve makrolidlerle kombine olarak izolatların %11.4'ünde (n = 8) gözlendi. Tetrasiklin dirençli izolatların 5'inde tetK, birinde tetM ve ikisinde de her iki geni birlikte bulundu. Eritromisin direnci izolatların %5.7'sinde (n = 4) bulundu. msrA, mphC, ermA birer izolatta, ermC ise msrA geni ile kombine olarak bir izolatta tespit edildi. İzolatların büyük kısmı 19.3 kb büyüklüğünde tek plasmid gösterirken, bazı izolatlar büyüklüğü >19.3 kb ile 0.9 kb arasında değişen 2-3 plazmid taşıdığı belirlendi. Yetmiş KNS izolatından 28'i (%40) Kongo Red Agar (KRA) metodu ile biyofilm sentezi ve 30'unun da (%42.9) biyofilm sentezinden sorumlu olan icaA ve icaD genleri yönünden pozitif olduğu saptandı.

This study aimed to determine the time taken for Escherichia coli O157:H7 to adapt to different types of acids and the effect of acid adaptation on the survival level of E. coli O157:H7 in sucuk (Turkish-type fermented sausage). E. coli O157:H7 cells were adapted to acids in a tryptic soy broth (TSB) set to pH 5.5 for 1-, 2-, 3-, and 4-h periods using hydrochloric, acetic, lactic, and citric acid. The acid tolerance of acid-adapted and nontreated cells was determined in TSB of pH 3.5 and then acid-adapted and nontreated E. coli O157:H7 (10 5 CFU/g) was added to sucuk. In the adaptation trial in which acetic acid was used, the highest acid resistance was seen in the 3-h adaptation samples, and in the lactic acid trials, the highest acid resistance was seen in the 3-and 4-h adaptation samples. In the adaptation trials with hydrochloric acid, it was observed that the duration of the adaptation period did not increase the resistance. It was determined that the survival rate of E. coli O157:H7 in sucuk was significantly increased through acid adaptation. As a result, it was understood that acid-adapted E. coli O157:H7 can maintain its viability in sucuk for at least 15 days.

ABSTRACT. Macrolide and lincosamide (ML) resistance and the related resistance genes of staphylococci were assessed from cases of bovine subclinical mastitis. Of the 104 Staphylococcus aureus and 62 coagulase negative staphylococcus (CoNS) isolates, 26 (25%) and 12 (19.4%) were resistant to ML, respectively. While constitutive ML resistance phenotype accounted for 15.4% (16/104) of S. aureus and 8.1% (5/62) of CoNS, inducible ML resistance phenotype accounted for 2.9% (3/104) of S. aureus and 3.2% (2/62) of CoNS. Among erythromycin-resistant isolates, single or various combination of different resistance genes were detected. The results of this study showed that ML resistance was prevalent among staphylococci from subclinical bovine mastitis cases in Hatay, Turkey. Therefore, a continuous surveillance is necessary to minimise the spread of antimicrobial-resistant staphylococci.KEY WORDS: bovine subclinical mastitis, macrolide-lincosamide resistance, staphylococcus.