Table 1.
list of bacterial and fungal isolates used in this study.
Fig 1.
Microtiter Broth Dilution Method Plate Setup: The figure shows a 96-microtiter plate that represents the experiment setup to evaluate the antimicrobial activity of ZnO-NPs.
Column 1 (A1 to F1 highlighted in blue) was loaded with ZnO-NPs suspension to observe the original solution turbidity. Wells highlighted in orange represent serial double fold dilution of ZnO-NPs in each row, followed by loading each well with standard bacterial suspension to evaluate the effect of ZnO-NPs on different microbial growth through measuring the MIC values. Wells in green at row G, and wells in white at row H were loaded with microbial suspension or media alone to serve as positive and negative controls, respectively.
Fig 2.
Schematic representation of VersaTrek Myco bottles used to evaluate the disinfectant properties of ZnO-NPs against acid-fast bacilli (AFB).
Two different CAP proficiency isolates of Mycobacterium tuberculosis were separately inoculated into Myco bottles. GS refers to growth supplements that support AFB growth. A mixture of antibiotics—polymyxin B, vancomycin, nalidixic acid, and amphotericin B (PVNA)—along with an additional antibiotic supplement (AS), was used to inhibit the growth of bacterial contaminants.
Table 2.
The mean of MIC values of the tested microorganisms.
Fig 3.
Panels A to C illustrate the testing of various microorganisms, each arranged in a separate row and exposed to different concentrations of ZnO-NPs. The concentration range tested spanned from 9.7 to 310 µg/mL, achieved through serial two-fold dilutions. In each plate, row G contained all tested microorganisms without ZnO-NPs, serving as a positive growth control, while row H was filled with blank media to act as a negative control. Abbreviations: Extended-spectrum beta-lactamases (ESBLs); Multidrug-resistant bacteria (MDR); Carbapenem-resistant Pseudomonas aeruginosa (CRPA); A. baumannii Multisensitive, A. baumannii MS; Methicillin-resistant Staphylococcus aureus (MRSA); Methicillin-susceptible Staphylococcus aureus, MSSA; Vancomycin- susceptible Enterococcus (VSE); Vancomycin- resistant Enterococcus (VRE).
Table 3.
The mean of inhibition zone diameter for Gram-negative bacteria using disc diffusion assay.
Table 4.
The mean of inhibition zone diameter for Gram-positive bacteria using disc diffusion assay method.
Fig 4.
Disc diffusion assay assessing the antimicrobial activity of ZnO-NPs against various Gram-positive and Gram-negative bacterial isolates.
Panels A to K display the antibacterial effects of ZnO-NPs alongside commercially available antibiotic discs for comparison. The central disc labeled “test” on each plate contains ZnO-NPs. Antibiotic discs were selected based on CLSI guidelines (CLSI, 2021) specific to each bacterial isolate. Additionally, a disc containing only zinc acetate was included on each plate as a diluent control. Abbreviations: Extended-spectrum beta-lactamases, ESBLs; Multidrug-resistant bacteria, MDR; Carbapenem-resistant Pseudomonas aeruginosa, CRPA; Carbapenem- susceptible Pseudomonas aeruginosa, CSPA; A. baumannii Multisensitive, A. baumannii MS. Methicillin-resistant Staphylococcus aureus, MRSA; Methicillin-susceptible Staphylococcus aureus, MSSA; Vancomycin- susceptible Enterococcus, VSE; Vancomycin- resistant Enterococcus, VRE.
Table 5.
Summary of CFU/mL and percent of reduction calculations on each sample type after exposure to ZnO-NPs at different time intervals, performed by pour plate assay.
Fig 5.
Each panel illustrates the disinfection effect of ZnO-NPs on different materials: water (Panel A), glass surface (Panel B), and stainless-steel surface (Panel C). The plates in each panel display microbial growth observed at various time intervals (5–60 minutes) and after overnight (ON) incubation.
Fig 6.
The effect of ZnO-NPs as surface disinfectant on a contaminated laboratory bench.
A Benche area was divided into four equal sections (5 × 5 cm), each contaminated with saline containing bacteria and allowed to airdry. ZnO-NPs suspension was applied, and cultures were taken at 5, 10, 15, and 20 minutes using sterile swabs on blood agar. Plate A observed growth of lab bench surface without ZnO-NPs treatments (number of colonies was numerous). Plate B. Observe the growth after ZnO-NPs exposure at different time intervals, including 5, 10, 15, and 20 mins.
Fig 7.
Two CAP proficiency testing AFB strains (E1-03 and E1-04) were evaluated in three independent experiments. The instrument detects changes in internal bottle pressure and automatically flags bottles as positive for microbial growth. The mean time to positivity for each strain is indicated below the corresponding assay bottle.