Aman IM, Esraa MA, Walaa ME
A total of one hundred infant milk powder samples were collected from different pharmacies in Kafrelsheikh Governorate for bacteriological examination. The obtained results revealed that B. cereus was detected in 19% and 11% (sporulated form) of the examined samples with average counts of 1.2 × 102 ± 5.2 × 102 and 4.0 × 102 ± 1.4 × 102 cfu/g, respectively. Subsequently, PCR assay to identify 2 virulent genes in 30 of the isolated strains was applied. The PCR targets selected were the hblc gene using FHBLC (F) and FHBLC (R) primers, and cytK gene using FCytK (F) and FR2ytK (R) primers. Eight (42%) of vegetative B. cereus isolates had hblC gene, and 3 isolates had cytK gene, while 7 isolates had both genes. Of the eleven B. cereus spore strains, 4 isolates had hblC gene, 2 had cytK gene and 2 had both genes. Additionally, E. sakazakii could be isolated from 3% of the examined samples, while salmonellae failed to be detected in any of the examined samples. Furthermore, 4 strains, one carrying hblC gene, one carrying cytK gene, one carrying both genes and one do not carry any of the genes were experimentally inoculated into reconstituted milk powder at concentration raged from 5 × 10 to 1.6 × 102 cfu/ml. The inoculated milk samples were incubated at 25ºC and examined for B. cereus count each 2 h up to 6 h storage. There was a remarkable increase of B. cereus organism's count without significance difference between the B. cereus inoculated genes. The results concluded that infant milk powder in spite of its low moisture content may at times suitable for supporting the growth of these organisms and subsequently be responsible for food poisoning to infants. The public health importance of the isolated microorganisms was discussed.