Evaluation of antimicrobial sensitivity to tetracycline exposed to non-thermal plasma

Cubas, Anelise L. V.; Dutra, Ana Regina de A.; Alves, Thiago C.; Bianchet, Ritanara T.; Rambo, Adriano A.; Debacher, Nito A.

doi:10.21577/0100-4042.20230006

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Article • Quím. Nova 46 (3) • 2023 • https://doi.org/10.21577/0100-4042.20230006 copy

Evaluation of antimicrobial sensitivity to tetracycline exposed to non-thermal plasma

Authorship SCIMAGO INSTITUTIONS RANKINGS

Tetracyclines comprise a large group of broad-spectrum antibiotics used in human and veterinary medicine. Its mechanism of action, via oral ingestion, is to inhibit bacterial protein synthesis, but a large amount (70%) is eliminated without being metabolized, which presents a risk for the arising of antibiotic-resistant species. In this study, the degradation of Tetracycline TC by non-thermal plasma NTP and the antimicrobial sensitivity of the treated solution are investigated. The degradation was followed by chromatographic analysis while the efficiency of NTP in inhibiting the action of TC on bacteria was evaluated by antimicrobial sensitivity test by disk diffusion method. The results showed a high rate of TC degradation, over 90%, in 10 min of NTP treatment for a 60 mL (107 mg L^-1) sample and very slow increase up to 94% in 30 min. The antimicrobial sensitivity test of TC after degradation by NTP showed no antibiotic activity. Therefore, our findings are encouraging, since the removal efficiency is below the minimum threshold require, to prevent with high probability, outgrowth of antibiotic-resistant bacteria. In addition, the results confirm that the NTP treated solution is safe to the environment.

Keywords:
non-thermal plasma; tetracycline degradation; antimicrobial sensitivity

Sample: Tetracycline
Selectivity
(NC95%) P-value: 0.03836 <0.05
Lower limit: 12.57 min
Upper Limit: 12.67 min
Linearity
Linear analytical curve: y = 0.94 x -6.14
x = concentration (mg L^-1). y = area (mAU)
Correlation coefficient: 0.9999
Detection and quantification limits
DL: 0.3758 mg L^-1

Time (min)	TC Concentration (mg L^-1 )	TC Degradation %	RSD^* * RSD: relative standard deviation (acceptable < 5%).
0	107.71	0	2.07
10	8.72	91.90	3.03
15	7.81	92.75	2.68
30	6.44	94.02	0.14

Parameters	0 min	10 min	15 min	30 min
Temperature (ºC)	22.00	50.66 ± 0.44	52.00 ± 0.66	51.66 ± 1.11
pH	4.35	2.73 ± 0.09	2.78 ± 0.29	2.44 ± 0.12
Conductivity (S cm^-1)	141.00	551.33 ± 31.34	801.33 ± 40.12	1363.00 ± 10.81
Color	5.00	95.00 ± 1.00	89.67 ± 3.11	41.00 ± 2.00
Turbidity (NTU)	0.92	1.67 ± 0.39	1.18 ± 0.37	1.02 ± 0.27

	df	Sum Sq	Mean Sq (MS)	f	p value Pr(>F)
Time	3	22504	7501	3931	5.2 × 10^{-13 ***}
Residuals	8	15	2
Signify codes: 0 ‘^*’ 0.001 ‘^’ 0.01 ‘^*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Plates	Control (0 min)	10 min
1	Φ 12.10 mm (dose 30 µg) ^* * (C = 107 mg L-1, 30 µL);	Φ 7.5 mm ± 0.35 mm
2	Φ 8.03 mm (dose 15 µg) ^ (C = 100 mg L-1, 15 µL);	0 mm
3	Φ 8.14 mm (dose 15 µg) ^* ***** (C = 50 mg L-1, 15 µL);	0 mm
4	Φ 7.15 mm (dose 7.5 µg) ^** ****** (C = 50 mg L-1, 7.5 µL).	0 mm

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[1] *e-mail: nito.debacher@ufsc.br