INTRODUCTION
Antimicrobial resistance give raise to significant global concern, largely attributed to its uncontrolled assimilation. The rapid worldwide spread of resistant bacteria necessitates urgent action to control its spread [1]. In the United States of America (USA) alone, there was 2.8 million resistant infections were recorded annually, leading to 35,900 deaths. Additionally, Clostridium difficile infection, a consequence of antimicrobial disturbance of intestinal microbiome, reporting another 12,800 deaths annually [2]. Reports suggest that accurately monitoring the economic impact of AMR resistance remains challenging. AMR infections unquestionably indisputably impose increased costs on healthcare systems, stemming from extended treatment durations and prolonged hospitalization. The medications required for treatment can be costly and may have reduced tolerability. However, a standardized methodology for estimating the economic burden of resistant infections is currently uncovered [3]. Direct treatment costs for six prevalent multidrug-resistant pathogens amount to $4.6 billion annually, with an additional $1 billion attributed to Clostridium difficile, and billions more for drug-resistant gonorrhea, totaling another $133.4 million [4]. Silver and its compounds have a long history of use in therapeutic applications and especially as antibacterial, spanning thousands of eras. Ancient Romans and Greeks utilized silver vessels for water and food storage to prevent deterioration. Hippocrates employed silver prescriptions for treating abscesses and promoting healing. AgNO3 was used also for instrument disinfection and wound care. The early 19th century saw the development of silver preparations. Silver has historically been utilized for treating wound infections and managing burns. However, its medical applications were largely superseded by new clinical introductions in the 1940s [5]. Nano Silver have also served as antimicrobial agents since the 19th century, and their applications have now expanded to encompass diverse physical, chemical, and biological uses in contemporary research [6]. Silver nanoparticles SNPs have proven their exceptional efficiency in their use as effective antimicrobial, anti-inflammatory and anti-tumor activity [7]. The use of combination therapy leads to the emergence of synergistic reactions to eliminate bacteria. Examples of these reactions include increasing membrane permeability, inhibiting the protein synthesis process, disrupting biofilms, and other activities, this is called the synergistic effect [8]. Although there are many synergistic treatments, there are treatments that show an antagonism effect, and this effect is often undesirable [9]. Research is still ongoing to understand the mechanism of action of antagonism, because logically antagonism, especially strong antagonism that limits the response, may also limit the effectiveness of the drug combination [10]. Present study aimed to prepare an antibiotic substitute targeting resistant bacteria and synergistic effect between Bacteriogenic SNPs and some antibiotics.

MATERIALS AND METHODS
Samples collection
The most resistant-bacteria to SNPs were isolated from soil and identified using built-in vitek2 system. Two sterile beakers containing 50 ml distilled water (DW). Each flask was supplied with 0.3 gms of soil sampled from two different areas separately and mixed well. 200ul from each flask were inoculated into SNPs – Enriched Brain Heart Infusion (BHI) agar plates were incubated at 37°C for a duration of 24 hours. Growing bacterial colonies were selected, Identified and used as a catalyst. One liter of BHI broth was prepared according to the manufacturer’s instructions, inoculated with a colony of the screened silver resistant bacteria (Enterobacter sp.) and incubated for 24 hrs. at 37C, Cell free extract (CFE) harvested by filtration of the culture through fast filter paper θ11cm and used as a catalyst for synthesis of SNPs [11].

Preparation of chemicals 
Preparation of AgNO3 stock solution One molar (1M) silver nitrate stock solution prepared by dissolving 1.6987 g AgNO3 in 10 ml of reagent-grade deionized distilled water. One liter of 10 mM AgNO3 working solution was prepared by dilution of 10 ml of 1 M stock solution to 1000 ml with reagent-grade deionized distilled water. Preparation and storage of AgNO3 was performed in dark condition (its preferred to prepare and use rather than storge of AgNO3 solutions to avoid photolytic reactions) [11]. 
Preparation of NaOH Five ml of 2M NaOH have been prepared by dissolving 0.39997 g of pure NaOH in final volume 5 ml deionized water. 
Preparation of cell-free extract CFE 1.4ml of 10mM AgNO3 was added to 900ml of reagent-grade distilled water. The solution was placed on a magnetic stirrer (60 °C, 200 RPM). Then, 98.6ml of the CFE product was gradually added (dropwise addition) to the solution along one hour [10]. 
Preparation of gentamycin 900ml of distilled water was taken and 1.4ml of 10 mM AgNO3 was added to it, and it was placed on a magnetic mixer, where 100ml of the antibiotic gentamicin was added to it, drop by drop for an hour, and then it was placed in the incubator for 4 days. Then, two substances were added gradually: (100 ml of CFE) and (100 ml of gentamicin) to the reaction mix, the PH adjusted for 8 by NaOH solution and they were incubated at 37 °C for 4 days a shaking incubator at 150 RPM [11]. 

Synthesis of SNPs
Cell free extract was titrated against 10 mM AgNO3, in a ratio of 1:3 (v/v) to acquire 1L of reaction solution on heated magnetic stirrer 200 rpm and monitored for trans coloration. During this period, for 1h intervals and examined spectrophotometrically at 420 nm using U.V.-visible spectrophotometer, after 4 days, reaction solution centrifuged at 16000 xg and washed three times using deionized distilled water, by repeating resuspension-centrifugation step. The precipitated SNPs was dehydrated (desiccated) in an oven at 60 °C. Finally, the dehydrated AgNPs, collected for further physicochemical and biological characterization [11]. 

Characterization of Bacteriogenic SNPs 
Physicochemical characterization. Bacteriogenic SNPs was indicated by color change and U.V. – visible spectroscopy; FESEM for morphology, homogeneity, and size distribution; Zeta potential for dispersity in colloids [12,13]. 
Antimicrobial activity: Antimicrobial activity was examined using Kirby Bauer method. SNPs were used against three types of bacteria, and SNPs were used with the antibiotic (gentamicin) also against resistant bacteria [14,15]. 
Erythrocyte toxicity (Biocompatibility) of bacteriogenic silver nanoparticles (SNPs) was assessed through an erythrocyte lysis assay. Human blood was sampled into heparinized tubes, and RBCs were separated by centrifugation (Eppendorf Minispin, Germany) at 2200 rpm for 10 minutes at 4 °C. sediment was carefully washed three times with phosphate buffer saline (pH 7.4), and re-suspended in the same buffer, and subsequently utilized for the test. For experimental purposes, 500 µL of SNP colloidal dispersion or 1% Triton w/v used as (positive control) was added to 500 µL of RBCs suspension. The suspension then incubated at 37 °C for one hour with continuous shaking. Post-incubation, the tubes were centrifuged. Supernatant was spectrally analyzed at 540 nm by UV–visible spectrophotometry (Shimadzu, Japan) to quantify hemolysis [15]. The supernatant from untreated blood served as the blank. All assays were triplicated, and the ratio of RBCs cytotoxicity (cell viability index) was computed using the following formula: 

RESULTS AND DISCUSSION
Colorimetric evidence Through reaction period trans coloration from yellowish to brown of the reaction solution indicate formation of silver nanoparticles (Fig. 1) and the gradient density of the brown color profiles the nucleation and growing of the nanoparticles. 
Spectrophotometric (U.V.-Visible) analysis of the reaction mix, revealed an optical absorption peak at approximately 420nm. This finding aligns with previous research, specifically the work of Xu and coworkers, which found that absorbance at λ 420nm was linked with the reduction of ionic (Ag+) to atomic (Ag°). The brown color suggests formation of AgNPs this finding was in accordance wth that of Xu and colleagues in 2020 [13]. 

FE-SEM Results 
Interpretation of FE-SEM image (Fig. 2) shows homogeneously shape distributed spherical SNPs with an average size of approximately 33 nm. These results are within the range consistent with the majority of researchers, as these properties obtained from bacteriogenic SNPs are considered ideal for biological applications and are consistent with the results of the researcher [12,16]. 

Results of Atomic Force Microscopy AFM 
AFM analysis revealed size distribution indicated by arithmetic mean height RMH 32 nm (Fig. 3), and root means require height RMSH 52.78. Homogeneous mesh improves the biomedical application of bacteriogenic SNPs was supported by the work of Al-Turnachy 2018, Xu 2020, and Luna 2021 [12,13,15].

Antibacterial activity
Antibacterial activity of bacteriogenic SNPs produced by Enterobacter sp. has been assayed using agar well diffusion method (Kirby-Bauer). Five concentrations (4.5, 1.8, 0.7, 0.3 and 0.1) mg/ml were examined against antibiotic resistant members of both gram-negative and gram-positive isolates (Staphylococcus sp. Klebsiella sp.), and synergism between SNPs and garamycin. Results showed MIC (0.4.5mg/ml) for SNPs against both (Staphylococcus sp. Klebsiella sp.) and stronger activity against G+ bacteria represented by staphylococcus sp. For garamycin, MIC was (0.28 mg/ml) against Staphylococcus sp., and (1.8 mg/ml) against Klebsiella sp. MIC for SNPs-Garamycin 
combination revealed (1.8 mg/ml) for both G+ and G- represented by (Staphylococcus sp. Klebsiella sp.) respectively, stronger activity against G+ bacteria represented by staphylococcus sp. Antagonistic activity of SNPs against Garamycin was recorded at concentration (0.3 mg/ml), (0.7 mg/ml) (Table 2). While weak synergism has recorded for staphylococcus between SNPs and Garamycin (4.50 mg/ml). For Klebsiella, neither synergism nor antagonism was recorded at concentration (4.50 mg/ml) these results found to be disagreed with the finding of Dove and coworkers their findings concluded that there was synergistic mechanism between AgNPs and Aminoglycosides [17-20].

Blood biocompatibility (RBCs toxicity Assay)
Cytotoxicity of silver nanoparticles (SNPs) was assessed in vitro using human erythrocytes. Hemolysis Index (HI) was quantified by measure the absorbance at 540 nm. Findings revealed that at concentration 1 mg/ml of bacteriogenic SNPs, hemolytic Index (HI) recorded a highest value (5.84±0.425), and at 0.5mg/ml (4.59±0.425), while at 0.1mg/ml it was recorded the lowest HI (4.24±0.425) (Table 3). However, hemolytic index found increased proportionally with AgNP concentrations, suggesting membrane disruption as an underlying mechanism. These findings highlight the importance of evaluating erythrocyte cytotoxicity alongside antibacterial activity. Luna and colleagues finding support this finding [21]. 

Zeta potential 
Results of Zeta potential for SNPs revealed (+21.1 mV) (Figure 4). Zeta potential serves as a crucial technique for assessing the stability of dispersion in the colloidal solutions, indicating the balance between repulsive and attractive electrostatic forces among charged silver nanoparticles (SNPs). Particles exhibiting stronger repulsive forces establish more powerful Brownian motion these results supported by the findings of Ntolia and coworkers [22].

CONCLUSION 
The results of this study concluded that the bacterial extract that stimulates the manufacture of nanoparticles supports the antimicrobial activity, as the bacterial biproducts present in the cell free extract protect and synergize the biomedical potential of the SNPs and cover the nanoparticles, but when silver nanoparticles are mixed with the antibiotic gentamycin, an antagonistic interaction appears, which reduces the effectiveness of the SNPs. Nano silver and also the antimicrobial activity of gentamycin [19].

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.