Impact of chlortetracycline and sulfapyridine antibiotics on soil enzyme activities.

Pharmaceutical antibiotics are frequently used in the livestock and poultry industries to control infectious diseases. Due to the lack of proper guidance for use, the majority of administrated antibiotics and their metabolites are excreted to the soil environment through urine and feces. In the present study, we used chlortetracycline and sulfapyridine antibiotics to screen out their effects on dehydrogenase, alkaline phosphatase and urease activity. Factorial experiments were conducted with different concentrations of antibiotic (0, 10, 25 and 100 mg kg-1 of soil) mixed with soil samples, and the enzyme activity was measured at intervals of 1, 4 and 21 days. The results show that the chlortetracycline and sulfapyridine antibiotics negatively affect the dehydrogenase activity, but the effect of sulfapyridine decreases with time of incubation. Indeed, sulfapyridine antibiotic significantly affect the alkaline phosphatase activity for the entire three-time interval, while chlortetracycline seems to inhibit its activity within 1 and 4 days of incubation. The effects of chlortetracycline and sulfapyridine antibiotics on urease activity appear similar, as they both significantly affect the urease activity on day 1 of incubation. The present study concludes that chlortetracycline and sulfapyridine antibiotics have harmful effects on soil microbes, with the extent of effects varying with the duration of incubation and the type of antibiotics used

Assessment of some cultural experimental methods to study the effects of antibiotics on microbial activities in a soil: An incubation study - Fig 3

<p><b>Cumulative respiration of oxytetracycline (OTC) (A) and sulfamethoxazole (SMX) (B) treatments depending on sample treatment (0, 1, 10, 25, 50, and 100 mg/kg) and incubation time (1, 2, 3, 4, 5, 6, 11, and 21 days).</b> Error bars represent the standard deviation of replicate analyses (n = 3). The standard deviations of replicates are in the range of 0.005–0.071 and 0.006–0.095 mg CO₂. g^-1 dm. h^-1 for oxytetracycline and sulfamethoxazole treatments, respectively.</p

Two-way analysis of variance (ANOVA) of cumulative respiration for OTC and SMX treatments.

<p>Two-way analysis of variance (ANOVA) of cumulative respiration for OTC and SMX treatments.</p

Physical and chemical characterization of the soil.

<p>Physical and chemical characterization of the soil.</p

Iron concentration of oxytetracycline (OTC) and sulfamethoxazole (SMX) treatments depending on sample treatment (0, 1 and 10 mg/kg).

<p>Different letters indicate significant differences (confidence level of 95%) among treatments at incubation time (one-way ANOVA, followed by the least significant difference test). Error bars represent the standard deviation of replicate analyses (n = 3).</p

Two-way analysis of variance (ANOVA) of microbial biomass carbon for OTC and SMX treatments.

<p>Two-way analysis of variance (ANOVA) of microbial biomass carbon for OTC and SMX treatments.</p