The resistance pattern and mechanisms of bacterial isolates obtained from clinical origin, soil, industrial effluent, orange juice products and drinking water were studied using commonly used antibiotics. The microbial load of the water samples, industrial effluent and orange juice products were 1.0 × 10¹−2.25 × 10⁶, 2.15 × 10⁵, and 3.5 × 10⁴−2.15 × 10⁵ cfu mL⁻¹, respectively. The faecal coliform test revealed that only two out of twenty orange juice products had MPN of 2 and 20, the MPN of water ranged from 1−≥1800, while the effluent had MPN of ≥1800. The bacterial isolates that were isolated include E. coli, S. aureus, P. vulgaris, S. marcescens, S. pyogenes, B. cereus, B. subtilis, Micrococcus sp., Klebsiella sp., P. aeruginosa, and Enterobacter sp. Also, clinical and soil isolates of P. aeruginosa were used in the study. Among the eight antibiotics tested for resistance on five strains of each bacterium, seven different resistance patterns were observed among the bacterial isolates obtained from water, effluent and orange juice products. Among the clinical and soil isolates of P. aeruginosa, four multiple-drug resistance patterns were obtained. Thirty strains of E. coli and S. aureus were tested for β-lactamase production and fourteen strains, seven each of E. coli and S. aureus that had high Minimum Inhibitory Concentration values (MIC) for both Amoxycillin and Cloxacillin were positive.

In this work, we present a low-field magnetic resonance imaging (LF-MRI) aptasensor based on the difference in magnetic behavior of two magnetic nanoparticles with diameters of 10 (MN₁₀) and 400 nm (MN₄₀₀) for the rapid detection of Pseudomonas aeruginosa (P. aeruginosa). First, specific anti-P. aeruginosa aptamers were covalently immobilized onto magnetic nanoparticles via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide chemistry for the capture of the target bacteria. In the presence of P. aeruginosa, an MN₁₀–bacteria–MN₄₀₀ (MBM) complex was formed after binding between the aptamers on magnetic nanoparticles and P. aeruginosa cells. When a magnetic field was applied, the MBM complex and free MN₄₀₀ were rapidly magnetically separated, and free MN₁₀ left in the solution worked as a T₂ (transverse relaxation time) single readout in MRI measurement. Under optimum conditions, the LF-MRI platform provides both image analysis and quantitative detection of P. aeruginosa, with a detection limit of 100 cfu/mL. The feasibility and specificity of the aptasensor were demonstrated in detecting real food, orange juice, and drinking water samples and validated using plate counting methods.

This work presents, for the first time, a fast and highly sensitive electrochemical method for determination of three organophosphorus compounds (OPs), diazinon (DZN), malathion (MLT), and chlorpyrifos (CLPF), using a modified pyrolytic graphite electrode (PGE) coupled to batch injection analysis system with multiple pulse amperometric detection (BIA–MPA). The PGE was modified by a nanocomposite based on functionalized carbon nanotubes (CNTf) and silver nanoparticles (AgNPs). The OPs samples were directly analyzed on the modified working electrode surface by BIA-MPA system in Britton-Robinson (BR) buffer 0.15 mol L⁻¹ at pH 6.0. The MPA detection of DZN, MLT and CLPF was performed using two potential pulses, which were sequentially applied on modified PGE at −1.3 V (100 ms) and +0.8 V (100 ms) for selective determination of these three OPs and working electrode cleaning, respectively. Under optimized conditions, the sensor presented a linear range of 0.1–20 μmol L⁻¹ for DZN, 1.0–30 μmol L⁻¹ for MLT and from 0.25 to 50 μmol L⁻¹ for CLPF. The limits of detection (LOD) and quantification (LOQ) of 0.35 and 1.18 μmol L⁻¹ for DZN, 0.89 and 2.98 μmol L⁻¹ for MLT, and 0.53 and 1.78 μmol L⁻¹ for CLPF were obtained. The proposed method exhibited high sensitivity of 0.068, 0.030 and 0.043 mA L μmol⁻¹ for DZN, MLT and CLPF detection, respectively. Furthermore, the BIA-MPA system provided an analytical frequency of 71 determinations per hour for direct determination of these OPs in water and food samples. The modified PGE coupled to BIA-MPA system showed a high stability of electrochemical response for OPs detection with relative standard deviation (RSD) of 1.60% (n = 20). The addition-recovery studies of the proposed method were carried out in tap water, orange juice, and apple fruit real samples, which showed suitable recovery values between 77 and 124%. The analytical performance of the developed sensor provides an attractive alternative method for OPs determination with great potential for a fast and sensitive application in contaminated samples with these pesticides.