Khalid S. Al-Maary

Extracellular biosynthesis of silver nanoparticles using Rhizopus stolonifer

Synthesis of silver nanoparticles (AgNPs) has become a necessary field of applied science. Biological method for synthesis of AgNPs by Rhizopus stolonifer aqueous mycelial extract was used. The AgNPs were identified by UV–visible spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FT-IR). The presence of surface plasmon band around 420 nm indicates AgNPs formation. The characteristic of the AgNPs within the face-centered cubic (fcc) structure are indicated by the peaks of the X-ray diffraction (XRD) pattern corresponding to (1 1 1), (2 0 0) and (2 2 0) planes. Spherical, mono-dispersed and stable AgNPs with diameter around 9.47 nm were prepared and affirmed by high-resolution transmission electron microscopy (HR-TEM). Fourier Transform Infrared (FTIR) shows peaks at 1426 and 1684 cm−1 that affirm the presence of coat covering protein the AgNPs which is known as capping proteins. Parameter optimization showed the smallest size of AgNPs (2.86 ± 0.3 nm) was obtained with 10−2 M AgNO3 at 40 °C. The present study provides the proof that the molecules within aqueous mycelial extract of R. stolonifer facilitate synthesis of AgNPs and highlight on value-added from R. stolonifer for cost effectiveness. Also, eco-friendly medical and nanotechnology-based industries could also be provided. Size of prepared AgNPs could be controlled by temperature and AgNO3 concentration. Further studies are required to study effect of more parameters on size and morphology of AgNPs as this will help in the control of large scale production of biogenic AgNPs.

Enhancement of Alkaline Protease Activity and Stability via Covalent Immobilization onto Hollow Core-Mesoporous Shell Silica Nanospheres.

The stability and reusability of soluble enzymes are of major concerns, which limit their industrial applications. Herein, alkaline protease from Bacillus sp. NPST-AK15 was immobilized onto hollow core-mesoporous shell silica (HCMSS) nanospheres. Subsequently, the properties of immobilized proteases were evaluated. Non-, ethane- and amino-functionalized HCMSS nanospheres were synthesized and characterized. NPST-AK15 was immobilized onto the synthesized nano-supports by physical and covalent immobilization approaches. However, protease immobilization by covalent attachment onto the activated HCMSS–NH2 nanospheres showed highest immobilization yield (75.6%) and loading capacity (88.1 μg protein/mg carrier) and was applied in the further studies. In comparison to free enzyme, the covalently immobilized protease exhibited a slight shift in the optimal pH from 10.5 to 11.0, respectively. The optimum temperature for catalytic activity of both free and immobilized enzyme was seen at 60 °C. However, while the free enzyme was completely inactivated when treated at 60 °C for 1 h the immobilized enzyme still retained 63.6% of its initial activity. The immobilized protease showed higher Vmax, kcat and kcat/Km, than soluble enzyme by 1.6-, 1.6- and 2.4-fold, respectively. In addition, the immobilized protease affinity to the substrate increased by about 1.5-fold. Furthermore, the enzyme stability in various organic solvents was significantly enhanced upon immobilization. Interestingly, the immobilized enzyme exhibited much higher stability in several commercial detergents including OMO, Tide, Ariel, Bonux and Xra by up to 5.2-fold. Finally, the immobilized protease maintained significant catalytic efficiency for twelve consecutive reaction cycles. These results suggest the effectiveness of the developed nanobiocatalyst as a candidate for detergent formulation and peptide synthesis in non-aqueous media.

Antimicrobial activity of some plant extracts against bacterial strains causing food poisoning diseases

Prevention of food spoilage and food poisoning pathogens is usually achieved by use of chemical preservatives which have negative impacts including: human health hazards of the chemical applications, chemical residues in food & feed chains and acquisition of microbial resistance to the used chemicals. Because of such concerns, the necessity to find a potentially effective, healthy safer and natural alternative preservatives is increased. Within these texts, Plant extracts have been used to control food poisoning diseases and preserve foodstuff. Antimicrobial activity of five plant extracts were investigated against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi using agar disc diffusion technique. Ethanolic extracts of Punica granatum, Syzygium aromaticum, Zingiber officinales and Thymus vulgaris were potentially effective with variable efficiency against the tested bacterial strains at concentration of 10 mg/ml while extract of Cuminum cyminum was only effective against S. aureus respectively. P. granatum and S. aromaticum ethanolic extracts were the most effective plant extracts and showed bacteriostatic and bactericidal activities against the highly susceptible strains of food borne pathogenic bacteria (S. aureus and P. aeruginosa) with MICs ranged from 2.5 to 5.0 mg/ml and MBC of 5.0 and 10 mg/ml except P. aeruginosa which was less sensitive and its MBC reached to 12.5 mg/ml of S. aromaticum respectively. These plant extracts which proved to be potentially effective can be used as natural alternative preventives to control food poisoning diseases and preserve food stuff avoiding healthy hazards of chemically antimicrobial agent applications.

Prevalence of the Antibiotic Resistance Genes in Coagulase-Positive-and Negative-Staphylococcus in Chicken Meat Retailed to Consumers

The use of antibiotics in farm management (growing crops and raising animals) has become a major area of concern. Its implications is the consequent emergence of antibiotic resistant bacteria (ARB) and accordingly their access into the human food chain with passage of antibiotic resistance genes (ARG) to the normal human intestinal microbiota and hence to other pathogenic bacteria causative human disease. Therefore, we pursued in this study to unravel the frequency and the quinolone resistance determining region, mecA and cfr genes of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-resistant coagulase-negative staphylococci (MRCNS) and methicillin-susceptible coagulase-negative staphylococci (MSCNS) isolated from the retail trade of ready-to-eat raw chicken meat samples collected during 1 year and sold across the Great Cairo area. The 50 Staphylococcus isolated from retail raw chicken meat were analyzed for their antibiotic resistance phenotypic profile on 12 antibiotics (penicillin, oxacillin, methicillin, ampicillin-sulbactam, erythromycin, tetracycline, clindamycin, gentamicin, ciprofloxacin, chloramphenicol, sulfamethoxazole-trimethoprim, and vancomycin) and their endorsement of the quinolone resistance determining region, mecA and cfr genes. The isolation results revealed 50 isolates, CPS (14) and CNS (36), representing ten species (S. aureus, S. hyicus, S. epidermedius, S. lugdunensis, S. haemolyticus, S. hominus, S. schleiferi, S. cohnii, S. intermedius, and S. lentus). Twenty seven isolates were methicillin-resistant. Out of the characterized 50 staphylococcal isolates, three were MRSA but only 2/3 carried the mecA gene. The ARG that bestows resistance to quinolones, β-lactams, macrolides, lincosamides, and streptogramin B [MLS(B)] in MRSA and MR-CNS were perceived. According to the available literature, the present investigation was a unique endeavor into the identification of the quinolone-resistance-determining-regions, the identification of MRSA and MR-CNS from retail chicken meat in Egypt. In addition, these isolates might indicate the promulgation of methicillin, oxacillin and vancomycin resistance in the community and imply food safety hazards.

Antimicrobial resistance and virulence characterization of Staphylococcus aureus and coagulase-negative staphylococci from imported beef meat

BackgroundThe objectives of this study were to characterize the diversity and magnitude of antimicrobial resistance among Staphylococcus species recovered from imported beef meat sold in the Egyptian market and the potential mechanisms underlying the antimicrobial resistance phenotypes including harboring of resistance genes (mecA, cfr, gyrA, gyrB, and grlA) and biofilm formation.ResultsThe resistance gene mecA was detected in 50% of methicillin-resistant non-Staphylococcus aureus isolates (4/8). Interestingly, our results showed that: (i) resistance genes mecA, gyrA, gyrB, grlA, and cfr were absent in Staphylococcus hominis and Staphylococcus hemolyticus isolates, although S. hominis was phenotypically resistant to methicillin (MR-non-S. aureus) while S. hemolyticus was resistant to vancomycin only; (ii) S. aureus isolates did not carry the mecA gene (100%) and were phenotypically characterized as methicillin- susceptible S. aureus (MSS); and (iii) the resistance gene mecA was present in one isolate (1/3) of Staphylococcus lugdunensis that was phenotypically characterized as methicillin-susceptible non-S. aureus (MSNSA).ConclusionsOur findings highlight the potential risk for consumers, in the absence of actionable risk management information systems, of imported foods and advice a strict implementation of international standards by different venues such as CODEX to avoid the increase in prevalence of coagulase positive and coagulase negative Staphylococcus isolates and their antibiotic resistance genes in imported beef meat at the Egyptian market.

Prevalence, serotyping and antimicrobials resistance mechanism of Salmonella enterica isolated from clinical and environmental samples in Saudi Arabia

Salmonella is recognized as a common foodborne pathogen, causing major health problems in Saudi Arabia. Herein, we report epidemiology, antimicrobial susceptibility and the genetic basis of resistance among S. enterica strains isolated in Saudi Arabia. Isolation of Salmonella spp. from clinical and environmental samples resulted in isolation of 33 strains identified as S. enterica based on their biochemical characteristics and 16S-rDNA sequences. S. enterica serovar Enteritidis showed highest prevalence (39.4%), followed by S. Paratyphi (21.2%), S. Typhimurium (15.2%), S. Typhi and S. Arizona (12.1%), respectively. Most isolates were resistant to 1st and 2nd generation cephalosporin; and aminoglycosides. Moreover, several S. enterica isolates exhibited resistance to the first-line antibiotics used for Salmonellosis treatment including ampicillin, trimethoprim–sulfamethoxazole and chloramphenicol. In addition, the results revealed the emergence of two S. enterica isolates showing resistance to third-generation cephalosporin. Analysis of resistance determinants in S. enterica strains (n = 33) revealed that the resistance to β-lactam antibiotics, trimethoprim–sulfamethoxazole, chloramphenicol, and tetracycline, was attributed to the presence of carb-like, dfrA1, floR, tetA gene, respectively. On the other hand, fluoroquinolone resistance was related to the presence of mutations in gyrA and parC genes. These findings improve the information about foodborne Salmonella in Saudi Arabia, alarming the emergence of multi-drug resistant S. enterica strains, and provide useful data about the resistance mechanisms.

Poultry and beef meat as potential seedbeds for antimicrobial resistant enterotoxigenic Bacillus species: a materializing epidemiological and potential severe health hazard

Although Bacillus cereus is of particular concern in food safety and public health, the role of other Bacillus species was overlooked. Therefore, we investigated the presence of eight enterotoxigenic genes, a hemolytic gene and phenotypic antibiotic resistance profiles of Bacillus species in retail meat samples. From 255 samples, 124 Bacillus isolates were recovered, 27 belonged to B. cereus and 97 were non-B. cereus species. Interestingly, the non-B. cereus isolates carried the virulence genes and exhibited phenotypic virulence characteristics as the B. cereus. However, correlation matrix analysis revealed the B. cereus group positively correlates with the presence of the genes hblA, hblC, and plc, and the detection of hemolysis (p < 0.05), while the other Bacillus sp. groups are negatively correlated. Tests for antimicrobial resistance against ten antibiotics revealed extensive drug and multi-drug resistant isolates. Statistical analyses didn’t support a correlation of antibiotic resistance to tested virulence factors suggesting independence of these phenotypic markers and virulence genes. Of special interest was the isolation of Paenibacillus alvei and Geobacillus stearothermophilus from the imported meat samples being the first recorded. The isolation of non-B. cereus species carrying enterotoxigenic genes in meat within Egypt, suggests their impact on food safety and public health and should therefore not be minimised, posing an area that requires further research.

Molecular characterization of the capsular antigens of Pasteurella multocida isolates using multiplex PCR

The use of molecular techniques for detection and characterization of the Pasteurella multocida is very important for rapid and specific detection and characterization of the organism. During the period from 15th February, 2014 to 15th April, 2015, 425 nasopharyngeal swabs and 175 lung and spleen samples were collected and examined by conventional methods, 80 strains (18.82%) of P. multocida were isolated from the calves, sheep and goat with respiratory manifestation. Meanwhile, 77 strains (44%) were isolated from emergency slaughtered animals. All the recovered strains were positive for specific PCR for detection of P. multocida strains previously identified as P. multocida by standard microbiological techniques. Multiplex PCR for molecular typing of the capsular antigens of the recovered P. multocida revealed positive amplification of 1044 bp fragments specific to the capsular antigen type A with 105 strains (66.88%), and amplification 511 bp fragments of the capsular antigen type E with 52 strain (33.12%) and absence of B, D and F antigens. Multiplex PCR for molecular typing of the capsular antigens of P. multocida can be used as a simple, sensitive, rapid, reliable technique instead of the serological techniques for identification of the capsular antigens of P. multocida

Phenotypic and genotypic analysis of pathogenic Escherichia coli virulence genes recovered from Riyadh, Saudi Arabia

The current study was carried out to evaluate the phenotypic and genotypic characterization of avian pathogenic Escherichia coli recovered from Riyadh, Saudi Arabia. During the period of 10th February–30th May 2015, 70 E. coli strains were isolated from chicken farms located in Riyadh, Saudi Arabia. All strains were tested phenotypically by standard microbiological techniques, serotyped and the virulence genes of such strains were detected by polymerase chain reaction (PCR). Most of the recovered strains from chickens belonged to serotype O111:K58 25 strains (35.7%), followed by serotype O157:H7 13 strains (18.57%), followed by serotype O114:K90 10 strains (14.29%), then serotype O126:K71 9 strains (12.9%), serotype O78:K80 8 strains (11.43%) and in lower percentage serotype O114:K90 and O119:K69 5 strains (7.14%). The virulence genotyping of E. coli isolates recovered from broilers revealed the presence of the uidA gene in all the field isolates (6 serovars) examined in an incidence of 100%, as well as the cvaC gene was also present in all field isolates (6 serovars), while the iutA gene and the iss gene were detected in 5 out of 6 field serovars in an incidence of 81.43% and 64.29%, respectively. Phenotypical examination of the other virulence factors revealed that 65 isolates were hemolytic (92.9%), as well as 15 isolates (21.42%) were positive for enterotoxin production. Meanwhile, 21 isolates (30%) were positive for verotoxin production, 58 isolates (82.86%) for the invasiveness and 31 isolates (44.29%) for Congo red binding activities of the examined serotypes.