Mahmoud Saleh Mahmoud Mohamed

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ABSTRACTPurpose/Aim: This study aims to evaluate the predisposing risk factors and antibiotic resistance of bacterial corneal ulcer to commonly used antibiotics. In addition, assess the in vitro efficacy of plant-derived essential oils (EOs) as safe and effective antimicrobial agents.Methods: Demographic features and predisposing risk factors of corneal ulcer patients were recorded. Isolation and identification of bacteria was performed using conventional microbiological methods. Antibacterial activity was determined by disk diffusion and the micro-dilution broth methods. EOs were extracted by steam distillation and were analyzed by gas chromatography mass spectrometry technique.Results: Out of the 200 patients with corneal ulcer evaluated in this study, the main predisposing factor of bacterial corneal ulcer was trauma (26.5%) and 96.7% isolates were multidrug resistant. Staphylococcus aureus was the predominant isolate 33 cases. Antibiotic susceptibility of bacterial isolates showed that the fourth-generation fluoroquinolones, gatifloxacin was the most effective antibiotic with sensitivity rate 81.3%. Seven selected EOs showed significant activity against most of the tested bacteria. Syzygium aromaticum oil showed high activity against all tested bacterial species with highest sensitivity rate (97.5%) and low minimal inhibitory concentration values against S. aureus (0.10 µl/ml). The chemical composition of the EOs showed that the monoterpenes were predominant. The main constituent of S. aromaticum oil was eugenol (76%).Conclusions: The current study showed that S. aromaticum oil had high antibacterial activity that could be helpful in the treatment of ocular bacterial infections to minimizing the possible side effects of commonly used antibiotic.

Abstract Aim This study aimed to test biofilm inhibition activities of each of essential oils (EOs), main compounds of EOs and enzymes against pathogenic Klebsiella pneumoniae. Methods and Results The effect of seven EOs and three enzymes was tested on formation and eradication of K. pneumoniae biofilm. Peppermint oil showed a robust biofilm inhibitory effect, causing inhibition that ranged from 69·2 to 98·2% at 5 ?l ml?1. Thyme oil was found to have the best biofilm eradication ability, causing eradication that ranged from 80·1 to 98·0% at 10 ?l ml?1. The most effective EOs were analysed by GC/MS, to determine the major chemical constitutes of each oil. Pure menthol was found to cause 75·3?97·5% biofilm inhibition at 2·5 ?g ml?1, whereas thymol caused 85·1?97·8% biofilm eradication at 5 ?g ml?1. However, moderate inhibition activity was detected for α?amylase and bromelain, while poor activity was detected for ??amylase. Ciprofloxacin combination with thyme oil and thymol was found to enhance antibiotic activity, and affect biofilm cell viability. The observed inhibitory/eradication activity on K. pneumoniae biofilms was confirmed by scanning electron microscopy. Conclusions Thyme and peppermint EOs, and their active components are promising antibiofilm agents alone and/or in combination with ciprofloxacin to inhibit/eradicate biofilms of K. pneumoniae. Significance and Impact of the Study The presented results suggest the potential application of EOs against infections, caused by biofilm?producing K. pneumoniae, to prevent biofilm formation or decrease their resistance threshold. Moreover, the combination of EOs with ciprofloxacin minimizes the antibiotic concentration used and accordingly the potential accompanying toxic side effects.

This study aimed to test and evaluate antibacterial and antifungal activities of secondary metabolites obtained from endophytic fungi isolated from the leaves of endemic plant Zygophyllum mandavillei. The fungus Cladosporium cladosporioides was the predominant isolated fungus with colonization and dominance frequencies percentage of 12.50 and 39.32 respectively. C. cladosporioides extract was found to have the best antimicrobial activity causing a zone of inhibition ranging from 20.7 to 25.7 mm against all tested bacterial and fungal phytopathogens. Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the extract successfully identified six major compounds: Cladosporin, Isocladosporin, 5′- hydroxyasperentin, Di (2-ethylhexyl) phthalate, 1-acetyl-17-methoxyaspidospermidin-20-ol, and 3-phenylpropionic acid. Enhanced antimicrobial activity was recorded for 3-phenylpropionic acid with MIC value ranging from 3.90 to 15.62 μg/ml followed by 5′- hydroxyasperentin with MIC ranging from 7.81 to 62.5 μg/ml. The most effective compound, 3-phenylpropionic acid, was further characterized by Fourier transform infrared spectroscopy (FT-IR) in addition to nuclear magnetic resonance (NMR) and mass spectroscopy to elucidate the chemical structure. The cytotoxicity of 3-phenylpropionic acid revealed a lower level of cytotoxicity at the concentration range 0.01–10 µg/ml as indicated by the cell viability percentage which is ranging from 75.47–94.14%. These results suggested that 3-phenylpropionic acid may serve as a potential alternative approach for the management of plant phytopathogens.

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Probiotic lactic acid bacteria are crucial producers of fermented dairy products that are popular functional foods in many countries. The health benefits of probiotic bacteria are mainly attributed to their effective bioactive metabolites. The quality of fermented milk is mainly dependent on the bacterial strain used in the fermentation process. In this study, an innovative technique is used in order to enhance the activities of the probiotic bacteria, quality of fermented milk, and consequently the whole fermentation process. Red laser dosages, at the wavelength of 632.7 nm, were applied to the type strain Lacticaseibacillus casei NRRL-B-1922 before the fermentation of skim milk. The results revealed that the scavenging of 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical and total antioxidant capacity were significantly increased from 21% in untreated control to 56% after bacterial laser irradiation of 12 J/cm2 dosage for 40 min. The antioxidant activity was found to be increased as the red laser dosage increased in a dose-response relationship. Additionally, the lactose fermentation in skim milk medium of 43.22 mg/mL initial concentration into organic acids was enhanced after L. casei irradiation and recorded 23.15 mg/mL compared to control group 28.35 mg/mL without bacterial pre-treatment. These results are correlated with increase of the β-Galactosidase activity, where the L. casei that has been exposed to 40 min of red laser exhibited the higher activity of a 0.37 unit/mL relative to the control 0.25 unit/mL. The assessment of this fermented milk after L. casei laser exposure for 10, 20, and 40 min indicates multiple biological effects, including assimilation of cholesterol as well as proteolytic and antibacterial activity. Our data on the exposure of L. casei to laser beam suggest promising application of red laser in the fermentation process of skim milk.

This study aims to evaluate the prevalence of multidrug-resistant (MDR) and biofilm-forming pathogens from animal source compared to clinical ones. In addition, to assess the antibacterial and antibiofilm activity of silver nanoparticles (AgNPs) alone and/or mixed with vancomycin. Out of 62 bacterial isolates from animal respiratory tract infection (RTI), 50.00% were defined as MDR, while among human ones, 44.00% were MDR. The bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae were the predominant isolated bacteria from both animal and human origin with frequency percentage of 50.00, 22.32, and 18.75, respectively. Among Staph. aureus strains, mecA gene was detected in 60.00% and 61.54% of animal and human isolates, respectively, while mecALGA251 (mecC) gene was detected in 13.33% and 15.38% of animal and human isolates, respectively. Biofilm formation ability among animal isolates was 83.87%, while among human ones was 86.00%. AgNPs were effective in inhibiting planktonic cells with minimal inhibitory concentration (MIC) values (0.625?10??g/mL), as well as eradicating biofilm with minimal biofilm eradication concentration values (1.25?10??g/mL). Noticeable low MIC of AgNPs was required for the isolates from animal source (0.625?5??g/mL) compared to clinical ones (0.625?10??g/mL). Remarkable reduction in AgNP effective concentration was observed after combination with 1/4 MIC of vancomycin with minimum recorded concentration of 0.08??g/mL. In conclusion, the prevalence of MDR among RT pathogens was recorded with high ability to produce biofilm and virulence factors from both animal and human pathogens. AgNPs showed strong antibacterial and antibiofilm activity alone and mixed with vancomycin, with up to fourfold reduction of AgNP inhibitory dose.This study aims to evaluate the prevalence of multidrug-resistant (MDR) and biofilm-forming pathogens from animal source compared to clinical ones. In addition, to assess the antibacterial and antibiofilm activity of silver nanoparticles (AgNPs) alone and/or mixed with vancomycin. Out of 62 bacterial isolates from animal respiratory tract infection (RTI), 50.00% were defined as MDR, while among human ones, 44.00% were MDR. The bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae were the predominant isolated bacteria from both animal and human origin with frequency percentage of 50.00, 22.32, and 18.75, respectively. Among Staph. aureus strains, mecA gene was detected in 60.00% and 61.54% of animal and human isolates, respectively, while mecALGA251 (mecC) gene was detected in 13.33% and 15.38% of animal and human isolates, respectively. Biofilm formation ability among animal isolates was 83.87%, while among human ones was 86.00%. AgNPs were effective in inhibiting planktonic cells with minimal inhibitory concentration (MIC) values (0.625?10??g/mL), as well as eradicating biofilm with minimal biofilm eradication concentration values (1.25?10??g/mL). Noticeable low MIC of AgNPs was required for the isolates from animal source (0.625?5??g/mL) compared to clinical ones (0.625?10??g/mL). Remarkable reduction in AgNP effective concentration was observed after combination with 1/4 MIC of vancomycin with minimum recorded concentration of 0.08??g/mL. In conclusion, the prevalence of MDR among RT pathogens was recorded with high ability to produce biofilm and virulence factors from both animal and human pathogens. AgNPs showed strong antibacterial and antibiofilm activity alone and mixed with vancomycin, with up to fourfold reduction of AgNP inhibitory dose.

The release of hexavalent chromium [Cr (VI)] into environments has resulted in many undesirable interactions with biological systems for its toxic potential and mutagenicity. Chromate reduction via chromium reductase (ChrR) is a key strategy for detoxifying Cr (VI) to trivalent species of no toxicity. In this study, ten bacterial isolates were isolated from heavily polluted soils, with a strain assigned as FACU, being the most efficient one able to reduce Cr (VI). FACU was identified as Escherichia coli based on morphological and 16S rRNA sequence analyses. Growth parameters and enzymatic actions of FACU were tested under different experimental conditions, in the presence of toxic chromium species. The E. coli FACU was able to reduce chromate at 100 μg/mL conceivably by reducing Cr (VI) into the less harmful Cr (III). Two distinctive optical spectroscopic techniques have been employed throughout the study. Laser-induced breakdown spectroscopy (LIBS) was utilized as qualitative analysis to demonstrate the presence of chromium with the distinctive spectral lines for bacteria such as Ca, Fe, and Na. While UV-visible spectroscopy was incorporated to confirm the reduction capabilities of E. coli after comparing Cr (III) spectrum to that of bacterial product spectrum and they were found to be identical. The chromate reductase specific activity was 361.33 μmol/L of Cr (VI) per min per mg protein. The FACU (EMCC 2289) 16S rRNA sequence and the ChrR-partially isolated gene were submitted to the DDBJ under acc. # numbers LC177419 and LC179020, respectively. The results support that FACU is a promising source of ChrR capable of bioremediation of toxic chromium species.

The search for effective and bioactive antimicrobial molecules to  encounter the medical need for new antibiotics is an encouraging area of research. Plant defensins are small cationic, cysteine-rich peptides with a stabilized tertiary structure by disulfide-bridges and characterized by a wide range of biological functions. The heterologous expression of Egyptian maize defensin (MzDef) in Escherichia coli and subsequent purification by glutathione affinity chromatography yielded 2 mg/L of recombinant defensin peptide. The glutathione-S-transferase (GST)-tagged MzDef of approximately 30 kDa in size (26 KDa GST +  ~ 4 KDa MzDef peptide) was immunodetected with anti-GST antibodies. The GST-tag was successfully cleaved from the MzDef peptide by thrombin, and the removal was validated by the Tris-Tricine gel electrophoresis. The MzDef induced strong growth inhibition of Rhizoctonia solani, Fusarium verticillioides, and Aspergillus niger by 94.23%, 93.34%, and 86.25%, respectively, whereas relatively weak growth inhibitory activity of 35.42% against Fusarium solani was recorded. Moreover, strong antibacterial activities were demonstrated against E. coli and Bacillus cereus and the moderate activities against Salmonella enterica and Staphylococcus aureus at all tested concentrations (0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 µM). Furthermore, the in vitro MTT assay exhibited promising anticancer activity against all tested cell lines (hepatocellular carcinoma, mammary gland breast cancer, and colorectal carcinoma colon cancer) with IC50 values ranging from 14.85 to 29.85 µg/mL. These results suggest that the recombinant peptide MzDef may serve as a potential alternative antimicrobial and anticancer agent to be used in medicinal application.

Drought stress is threatening the growth and productivity of many economical crops. Therefore, it is necessary to establish innovative and efficient approaches for improving crop growth and productivity. Here we investigated the potentials of the cell-free extract of Actinobacteria (Ac) isolated from a semi-arid habitat (Al-Jouf region, Saudi Arabia) to recover the reduction in maize growth and improve the physiological stress tolerance induced by drought. Three Ac isolates were screened for production of secondary metabolites, antioxidant and antimicrobial activities. The isolate Ac3 revealed the highest levels of flavonoids, antioxidant and antimicrobial activities in addition to having abilities to produce siderophores and phytohormones. Based on seed germination experiment, the selected bioactive fraction of Ac3 cell-free extract (F2.7, containing mainly isoquercetin), increased the growth and photosynthesis rate under drought stress. Moreover, F2.7 application significantly alleviated drought stress-induced increases in H2O2, lipid peroxidation (MDA) and protein oxidation (protein carbonyls). It also increased total antioxidant power and molecular antioxidant levels (total ascorbate, glutathione and tocopherols). F2.7 improved the primary metabolism of stressed maize plants; for example, it increased in several individuals of soluble carbohydrates, organic acids, amino acids, and fatty acids. Interestingly, to reduce stress impact, F2.7 accumulated some compatible solutes including total soluble sugars, sucrose and proline. Hence, this comprehensive assessment recommends the potentials of actinobacterial cell-free extract as an alternative ecofriendly approach to improve crop growth and quality under water deficit conditions.

Biomolecules from natural sources, including microbes, have been the basis of treatment of human diseases since the ancient times. Therefore, this study aimed to investigate the potential bioactivity of several actinobacteria isolates form Al-Jouf Desert, Saudi Arabia. Twenty-one actinobac-terial isolates were tested for their antioxidant (flavonoids, phenolics, tocopherols and carotenoids) content, and biological activities, namely FRAP, DPPH, ABTS, SOS and XO inhibition, anti-hemolytic and anti-lipid peroxidation as well as their antibacterial and antiprotozoal activities. Accordingly, five isolates (i.e., Act 2, 12, 15, 19 and 21) were selected and their 90% ethanolic extracts were used. The phylogenetic analysis of the 16S rRNA sequences indicated that the most active isolates be-long to genus Streptomyces. The genus Streptomyces has been documented as a prolific producer of biologically active secondary metabolites against different cancer types. Thus, the anti-blood cancer activity and the possible molecular mechanisms by which several Streptomyces species extracts inhibited the growth of different leukemia cells, i.e., HL-60, K562 and THP-1, were investigated. In general, the five active isolates showed cytotoxic activity against the tested cell lines in a dose dependent manner. Among the potent isolates, isolate Act 12 significantly decreased the cell viability and showed maximum cytotoxic activities against both HL-60 and K562 cells, while isolate Act 15 exhibited maximum cytotoxic activity against THP-1 cells. Moreover, Act 2 and Act 12 reduced cyclooxygenase (COX-2) and lipoxygenase (LOX) activity, which is involved in the proliferation and differentiation of cancer cells and may represent a possible molecular mechanism underlying leukemia growth inhibition. The bioactive antioxidant extracts of the selected Streptomyces species inhibited leukemia cell growth by reducing the COX-2 and LOX activity. Overall, our study not only. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

The microbial fuel cells (MFCs) are biochemical devices in which bacteria create electrical power by oxidizing simple compounds such as glucose as well as complex organic matter in wastewater. In this study, pumping air into the cathode chamber and its effect on microbial fuel cell performance was investigated. The metabolism of bacteria existed in wastewater was responsible for the generation of bioelectricity. The developed MFC system was designed by utilizing phosphate buffer to operate the system at controlled pH equal 7 and at a stable temperature of 30°C. It was found that increasing oxygen supply to the cathode chamber has a positive effect on the cell performance by increasing the voltage value. Generally, the efficiency of microbial fuel cell was enhanced in the case of cathodic chamber aeration in comparison to the case of no aeration was applied. It was found that the voltage increased in the case of oxygen supply to reach 0.45 mv with a stability over the 138 h of the experiment compared to the case of no aeration was applied where the voltage reached only 0.2 mV with stability in one case and 0.4 mV after 78 h of operation with instability in the second case. Therefore, the performance of the microbial fuel cell improved. It can be concluded that oxygen concentration affects both reaction kinetics and final power efficiency. © 2021 National Information and Documentation Center (NIDOC).

The improvement of milk dairy products’ quality and nutritional value during shelf-life storage is the ultimate goal of many studies worldwide. Therefore, in the present study, prospective beneficial effects of adding two different industrial yeasts, Kluyveromyces lactis and Saccharomyces cerevisiae pretreated by heating at 85◦C for 10 min to be inactivated, before fermentation on some properties of ABT fermented milk were evaluated. The results of this study showed that the addition of 3% and 5% (w/v) heat-treated yeasts to the milk enhanced the growth of starter culture, Lactobacillus acidophilus, Bifidobacteria, and Streptococcus thermophilus, during the fermentation period as well as its viability after 20 days of cold storage at 5 ± 1◦C. Furthermore, levels of lactic and acetic acids were significantly increased from 120.45 ± 0.65 and 457.80 ± 0.70 µg/mL in the control without heat-treated yeast to 145.67 ± 0.77 and 488.32 ± 0.33 µg/mL with 5% supplementation of Sacch. cerevisiae respectively. Moreover, the addition of heat-treated yeasts to ABT fermented milk enhanced the antioxidant capacity by increasing the efficiency of free radical scavenging as well as the proteolytic activity. Taken together, these results suggest promising application of non-viable industrial yeasts as nutrients in the fermentation process of ABT milk to enhance the growth and viability of ABT starter cultures before and after a 20-day cold storage period by improving the fermented milk level of organic acids, antioxidant capacity, and proteolytic activities. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Labneh is positioned in the top ranking of the bestselling dairy products all over the world due to its health benefits and delicious taste. Labneh production depends mainly on probiotic bacteria in the fermentation of milk. Probiotic bacteria have many health benefits, which are driven by their selective bioactive metabolites that quantitively affect the fermentation products. The current investigation aimed to study the implementation of photobiomodulation through the irradiation of Lacticaseibacillus casei NRRL-B-1922 by a He–Ne laser (630 nm) with different laser doses (3, 6 & 12 J/cm2) prior to milk fermentation. This procedure sought to improve the probiotic bacteria’s activities while enhancing the labneh’s characteristics and consequently produce a more favorable labneh product with better marketing qualities. The photobiostimulated bacterial starter was found to induce increased titratable acidity with the moisture reduction of the labneh product under cold storage conditions for 20 days. The effect was most prominent when using a 12 J/cm2 laser dose. The flavor-aiding components, mainly diacetyl and acetaldehyde compounds, and sensory scores were increased in the labneh produced by irradiated L. casei when compared to the non-radiated probiotic culture after storing the products under cold conditions for 20 consecutive days. Moreover, the antioxidant and proteolytic activities of labneh produced by treated L. casei (12 J/cm2 laser dose) after cold storage were significantly elevated by 41 and 14%, respectively. In conclusion, we can report significantly improved selected characteristics in the final products after the employment of photobiomodulation process, the potential application of this concept on the industrial scale, and its implications on lengthening the product shelf life with improved qualities.

Bioethanol is a promising biofuel produced from agricultural wastes. The problem is that the bioconversion of cellulose to bioethanol takes a long time for excellent results. Predominantly, efficient enzymes and active microorganisms (yeast) can enhance the enzymatic saccharification and fermentation bioprocesses, respectively. The addition of nutrients and electron acceptors in form of nanomaterials was found to modify the bioenvironment and to biostimulate the microorganisms to accomplish the target bioprocesses efficiently. The objective of this investigation was to increase bioethanol production from agricultural wastes using nanomaterials. In this study, the bioethanol production from potato peels (as an example of agricultural wastes) was increased using ZnO nanomaterials and ZnO/g-C3N4 nanomaterials with the concentration of 5, 10, 15, 50, 100, and 150 mg/L each as well as the control (without the addition of nanomaterials). It was hypothesized that yeast treatment with nanomaterials (nutrients) leads to biostimulate yeast cells and increases cell activity. Consequently, it is hypothesized that these procedures increase bioethanol production from potato peels over a shorter Hydraulic Retention Time (HRT), i.e., residence time. It was found that the biostimulation of the fungi (yeast) Saccharomyces cerevisiae using 150 mg/L of ZnO/g-C3N4 nanomaterials generated the highest bioethanol concentration of 33.2% compared to all other treatments. © 2022 National Information and Documentation Center (NIDOC)

Agricultural and agro-industrial wastes (e.g., potato peel waste) are causing severe environmental problems. The processes of pretreatment, saccharification, and fermentation are the major obstacles in bioethanol production from wastes and must be overcome by efficient novel techniques. The effect of exposing the fungi (yeast) Saccharomyces cerevisiae to laser source with the addition of graphitic carbon nitride nanosheets (g-C3N4) with different concentrations on bioethanol production was investigated through the implementation of a batch anaerobic system and using potato peel waste (PPW). Dichromate test was implemented as quantitative analysis for quantification of the bioethanol yield. The benefits of this test were the appearance of green color indicating the identification of ethanol (C2H5OH) by bare eye and the ease to calculate the bioethanol yield through UV–visible spectrophotometry. The control sample (0.0 ppm of g-C3N4) showed only a 4% yield of bioethanol; however, by adding 150 ppm to PPW medium, 22.61% of ethanol was produced. Besides, laser irradiations (blue and red) as influencing parameters were studied with and without the addition of g-C3N4 nanomaterials aiming to increase the bioethanol. It was determined that the laser irradiation can trigger the bioethanol production (in case of red: 13.13% and in case of blue: 16.14% yields, respectively) compared to the control sample (in absence of g-C3N4). However, by adding different concentrations of g-C3N4 nanomaterials from 5 to 150 ppm, the bioethanol yield was increased as follows: in case of red: 56.11% and, in case of blue: 56.77%, respectively. It was found that using fungi and exposing it to the blue laser diode source having a wavelength of 450 nm and a power of 250 mW for a duration of 30 min with the addition of 150 mg L−1 of g-C3N4 nanomaterials delivered the highest bioethanol yield from PPW. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

λ-cyhalothrin is a widely used synthetic pyrethroid insecticide and its persistence in plant, soil and water exerts a detrimental effect on humans as well as the environment. There are many studies regarding isolated bacteria capable of degrading λ-cyhalothrin in vitro. However, limited work has been done examining the microbial degradation of λ-cyhalothrin together with plant growth promotion under greenhouse conditions. In this study, 43 bacterial strains were isolated from heavily polluted soil with λ-cyhalothrin by the enrichment technique. The plant growth promotion characteristics of all isolates were evaluated. The results revealed that five isolates were potential in λ-cyhalothrin biodegradation at high concentration (1200 mg/L) within only 24 h together with their high plant growth promotion abilities. The morphological, biochemical and 16S rDNA sequence analyses identified the isolates as Bacillus subtilis strains. The GC/MS analysis revealed that the selected isolates reached high levels of degradation after only two days, the degradation percentage ranged from 95.72 to 99.52% after 48 h of incubation. Furthermore, the degradation pathway for complete detoxification and metabolism of λ-cyhalothrin was established. Moreover, greenhouse experiment was conducted, the results indicate that the application of seed coat significantly enhanced Vicia faba seedling growth and caused an increase from 38.4 to 40.2% percentage of fresh and dry weight, respectively compared to untreated control. All isolates were effective to remove the pesticide residues in Vicia faba seedlings and recorded the highest degradation percentage of 83.79 under greenhouse conditions. Therefore, it can be concluded that the Bacillus subtilis strains isolated in this study have a dual potential role in complete mineralization of λ-cyhalothrin residues in vivo as well as effective biofertilization for future use in sustainable agriculture. © 2022, The Author(s).

Fish products are essential sources of animal proteins and numerous nutrients required for healthy human nutrition worldwide. However, some types of low-priced fish may look very similar to some other expensive types, and usually, it is not easy to differentiate between them for inexperienced customers. Moreover, in some markets, adulterating such high-priced fish types through its substitution by cheaper ones or mixing with bacterially spoiled ones, mostly when sold as fish fillets, is sometimes common. Certainly, fish microbial contamination in open markets represents serious hazards for people’s public health. Accordingly, seeking easy and fast fish fraud detection methods and their microbial contamination disclosure is crucial. Currently, available techniques are costly, time-consuming, and requiring special laboratories. In the present work, laser-induced fluorescence (LIF), as a spectrochemical analytical technique and diffuse optical measurements, has been used to discriminate between fillets of low-priced Tilapia and expensive Nile Perch and disclose microbial contamination in any. The experimental data have been analyzed and evaluated using the principal component analysis (PCA), partial least square regression (PLSR), and receiver operatic characteristic (ROC) methods. The results demonstrated the high advantages of optical and spectrochemical techniques in the fast and accurate discrimination between the two fish species. Moreover, LIF spectral band obtained at 490 nm showed a difference in microbial load between both species. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.