hoda dezhkhi

Mycobacterium simiae has been identified as the most abundant species of slow-growing mycobacterium isolated from clinical specimens in Iran. One of the genetic fingerprinting methods used for this purpose is called Variable number tandem repeat (VNTR). In this study, in addition to the hsp65 PCR-RFLP method, the genetic pattern of Mycobacterium simiae was investigated using QUB11b, QUB4156, QUB26 loci and VNTR method for epidemiological studies. In this study, among 56 samples of atypical pulmonary and extrapulmonary mycobacteria isolated from patients with pulmonary tuberculosis symptoms, using culture on Lowenstein Jensen medium and differential tests including nitrate reduction, catalase activity test, niacin test, growth rate and pigment production and hsp65 PCR-RFLP method, all isolated mycobacterium simiae were identified. Out of 56 isolated non-tuberculous mycobacteria, 41 samples (73.2%) were slow-growing and 15 samples (26.7%) were fast-growing. Among the slow growths, 30 specimens (73.1%) were mycobacterium simiae and among the fast growths, the highest number was related to mycobacterium abscessus(80%). Among 30 mycobacterium simiae samples, (10%) of the samples were sensitive to amikacin and kanamycin and resistant to ciprofloxacin and (6.6%) were resistant to amikacin and kanamycin and sensitive to ciprofloxacin. The QUB11b locus had the highest differentiation power (HGI = 0.7) among the strains of mycobacterium simiae tested and was highly polymorphic.

QUB11b locus in both mycobacterium tuberculosis complex and mycobacterium simiae isolates has the highest discriminative power, 0.6 and 0.7, respectively. This locus can not be used to differentiate the two groups of mycobacterium tuberculosis complex and mycobacterium simiae, but this locus is suitable for differentiating mycobacterium simiae subtypes due to its high discriminative power.

Cream enabled the growth of most microorganisms due to the adequate moisture, pH close to neutral, and nutrient rich. The major cause of bitter flavour in cream is degradation of proteins to the hydrophobic peptides by protease enzyme derived from the thermostable bacteria resistant to the pasteurization temperature. The present study was aimed to investigate and molecular identify of bacteria spp. causing bitter flavour in pasteurized cream. The pasteurized cream samples were collected, then microbiological tests such as total count of microorganisms, psychrotrophic bacteria count, coliform bacteria count, thermostable bacteria count, sporogen bacteria count and also chemical tests such as acidity and pH measurement were carried out. The tests were fulfilled with three repetitions at 4ºC and 15ºC in first, third, fifth, seventh, ninth, and eleventh days after the cream production. The isolates causing bitter flavour in creams were identified by physiological, biochemical, phylogenetical, and molecular methods. The bacterial isolates were inoculated into the pasteurized creams and assayed for changing in flavour. The two species of bacteria causing bitter flavor were isolated from the pasteurized creams. The sequencing of 16S rRNA gene of isolates indicated that they were Bacillus cereus and Bacillus subtilis. The temperature of preservation is one of the most important agents of microorganisms’ activity and dairy product durability. Keeping raw milk for a long time before the pasteurization leads to increasing proteolytic bacteria resistant to the pasteurization temperature, producing protease by the organisms and finally, changing the product flavour.