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In a previous work, the optimized crude chitinase of Trichoderma viride exhibited strong inhibitory activity against food spoilage moulds (phytopathogens) Alternaria solani, Botrytis cinerea, Penicillium oxalicum and P. italicum, with the first species being the most affected. Currently, on testing the antagonistic activity of T. viride against the previous phytopathogens, the antagonist exhibited a strong activity particularly towards A. solani. The antagonist displayed more than one mechanism of parasitism on A. solani including penetration of the pathogen hyphae, abnormal pathogen hyphae swelling, lack of conidia formation, conidia malformation as well as degradation of the pathogen cell wall chitin through secretion of chitinase enzyme which is a major cause of antagonism. Fortunately, the present chitinase secreted by Trichoderma viride is found to be a constitutive enzyme. The previously optimized enzyme showed also a powerful insecticidal activity against home insects cockroach, spider and ant where the exoskeleton was softened and hydrolyzed, followed by rapid killing of the insects within 12 minutes.

Shiga toxin-producing Escherichia coli (STEC) strains have emerged as important foodborne pathogens of global public health concern, causing life-threatening diseases. Sheep and their products have been documented as important reservoirs for STECs, especially E. coli O157. The aim of this study was to investigate STECs from diarrheal human and sheep in Al-Madinah Al-Munawarah, Saudi Arabia. Fecal samples were collected between June and August, 2015 from diarrheal humans (n = 134) and sheep (n = 87). Presumptive E. coli human-and sheep-isolated strains were identified for their serotypes, the associated virulence genes (Shiga toxin [stx1 , stx2 ], haemolysin [ehxA] and intimin [eae]) by polymerase chain reaction and their susceptibility to antibiotics. Pulsed-field gel electrophoresis (PFGE) was used to demonstrate the genetic relatedness between Serotype O157:H7 human- and sheep-isolated strains. Forty eight (48/221; 21.7%) STECs were recovered from both human and sheep, their serotypes were as follows: O157:H7, O26:H11, O157:HNM, O26:HNM, O128:H2, O48:HNM, O111:HNM and OUT:HUT. Various virulence profiles and multiple antibiotic resistance were observed among the isolates. Twenty eight O157:H7 serotypes (17 human isolates and 11 sheep isolates) were identified in 13 PFGE pulsotypes, where human and sheep isolates were highly related. PFGE banding profiles together with serotypes and genotypes afford proof that human and sheep can be colonized and infected with similar E. coli O157:H7 strains. Our findings highlight the importance of epidemiological and microbiological surveillance of STECs; as well as the development of control measures to decrease risks associated with zoonotic O157:H7.

The aim of this study was to determine bacterial contamination in 28 refrigerated and unrefrigerated, commercial and home-made food items in Al Madinah Al Munawarah, Saudi Arabia. Of the 60 bacterial strains isolated, 53 were recovered from food samples refrigerated for 7 days and 7 from fresh, unrefrigerated food. The isolated bacteria were screened for lecithinase enzyme (toxin) production by the cup plate clearing zone technique. All isolates were positive on the basis of their ability to grow aerobically on egg yolk agar, giving black colonies as a characteristic feature of lecithinase production and opaque zones with diameters of 4–27 mm. Isolates were categorized into low, moderate and high lecithinase producers. Potent lecithinase-producing strains isolated from refrigerated green pepper (PS1) and lettuce (LS1) had a remarkably large zone measuring 27 ± 1.9 mm. All isolates also had additional toxic properties, including caseinase and haemolytic activities. Genotypic characterization by amplified ribosomal DNA restriction analysis showed that strains PS1 and LS1 were from same genus. Phenotypic characterization with biochemical tests and the Phoenix identification system suggested their affiliation to the Bacillus group. 16S rDNA sequence analysis of both strains showed them to be Bacillus cereus, with 99% sequence similarity to B. cereus strain J8B-67.