**21. Conclusion**

*Pathogenic Bacteria*

**19. Antimicrobial property by hydrogen peroxide production**

**20. Antibacterial activity of nanoparticles (NPs)**

Bacterial enzymatic activity is destroyed by hydrogen peroxide which is a thermodynamically unstable and produced by Lactobacillus [95]. Other lactic-acidproducing bacteria and lactobacillus both are lacking heme and thus not utilizing the cytochrome systems for terminal oxidation. Flavoproteins are used by Lactobacilli, which convert oxygen to hydrogen peroxide and this mechanism, results in the formation of hydrogen peroxide in amounts which are degraded by the organism [96].

The nanotechnology applications used in the food industry for food safety, disease treatment, for molecular and cellular biology as new tools, and for pathogen detection and protection [94]. NPs reported as applied in the nano tracer and nanosensor fields in food industries [97, 98]. Nanotechnology used in food packaging to

After exposure to zinc oxide (ZnO) NP minimal inhibition concentration *Staphylococcus aureus (S. aureus) and Salmonella typhimurium* (S. *typhimurium*) were reduced to 0 within 4 and 8 h, respectively. Scanning electron micrographs of the targeted cell showed the completely lysis of the cells. *Pseudomonas* spp. were the most resistant and *Bacillus cereus* was the most sensitive among all of the studied

Higher concentrations of Ag NPs showed the stronger antimicrobial activity. Ag NPs are used as antibacterial agents against *Escherichia coli (E. coli)* (Gram

The studied showed same results of Ag NPs between *S. aureus, E. coli* [110]. It was reported that smaller Ag NPs had effective antibacterial activity but having higher cytotoxicity. The antibacterial activity of Ag NPs is not only against the *S. aureus* and *E. coli* and*,* but also, *P. aeruginosa* [111]*.* ZnO NP inform of powders are widely used in coating electronic devices, cosmetics, catalysts and pigments. Instead of the extensive use of ZnO NPs, the safety of ZnO NPs for humans is not clear yet. In many studies the toxicity of metal oxide NPs and ZnO NPs towards

There are many types of NPs, and a variety of others are expected to introduce by the future researchers. Antibacterial agents are important and used in many industries, mainly in food industry. Cintas currently used antibacterial agents in the food industry are classified into two groups: inorganic agents and organic [101]. Inorganic antibacterial agents including NPs are used in food industry as they are stable under high pressures and temperatures conditions are required in food-processing, and regarded as safe to use for human and animals, as compared to organic materials [102, 103]. Studies showed that few NPs have selective toxicity to bacteria having lesser effects on human cells [104]. Foodborne outbreaks all over the world are increasing day by day and is important to control the causes. NPs are useful antibacterial agents that applied in the food industry. Silver (Ag) NPs are used in the medical and pharmaceutical industries. Ag NPs are very significant for the potential use in wide range of biological applications, as an antibacterial and antifungal agent for antibiotic resistant organisms to prevent infections. The concentration of NPs is linked with antibacterial activity. However, studies disagree with one another, indicating the mechanisms of NPs which causing antibacterial activity and toxicity to bacterial cells are very complex one [105–107]. Thus, it is challenging to classify the NPs as or adverse NPs or beneficial NPs towards bacteria. The tolerance property of bacteria having lesser growth rate is associated with the expression of genes related

prevent contamination and to improve the shelf life of food [99, 100].

**26**

to stress-response [108].

strains against ZnO NPs.

negative bacteria) [109].

From the total *P. aeruginosa* isolates 66 to >90% were from the Lahore region and showed *in vitro* resistance to many of the commercially available antibiotics tested. Meropenem, Piperacillin, and Amoxicillin were the drugs for which there was the greatest susceptibility and represent recommended treatments for infections due to *P. aeruginosa* in our region. A significant killing of these *resistant P. aeruginosa* strains by factors present in supernates of *Lactobacilli* spp. was observed, suggesting that the use of *Lactobacilli* spp. as probiotics may be of value for the treatment or prevention of *P. aeruginosa* colonization. We also found strong *in vitro* anti-bacterial efficacy of Ag, Zn and Fe3 oxide NPS against the local *P. aeruginosa* isolates, suggestive of additional research into their practical application in a healthcare department [117]. The differences in pathogenicity due to between the *P. aeruginosa* isolates, which could be due to genes involved in the quorum sensing and biofilm formation which having the ability to develop infections. The research could be important in future studies as the already reported isolates used are have same environmental conditions which having the multidrug resistant *P. aeruginosa* strains. The genomic variations between the isolates of *P. aeruginosa* are also observed for detection of virulence genes in strains of *P. aeruginosa* could highlight the link between acute and chronic respiratory infections. The collected and provided data could conclude that the virulence genes are important in severity of acute and chronic respiratory infections in human beings.
