الكشف الجزيئي Molecular Identification والتصنيف القائم على التسلسل الجيني Sequence Based Typing لبكتيريا الليجيونيلا نيوموفيلا Legionella pneumophila في العينات البيئية والسريرية في فلسطين
محمود جميل اسحق عمرو
mahmod jameel ishaq amro
Legionellae are gram-negative bacteria, rod shaped, strictly aerobic and nutritionally fastidious. Legionella species are implicated in two clinical syndromes: Legionnaires’ Disease (LD), and Pontiac fever, which are collectively known as legionellosis. Among the 56 species and 70 serogroups of Legionella species, Legionella pneumophila is the major cause of sporadic and outbreak legionellosis (91.5%), and serogroup 1 is the predominant serotype (84.2%). Many studies have demonstrated that the main source for LD is the potable water systems in large buildings like hospitals and hotels. The contamination of hospitals' water systems with Legionella is high risk for patients with various diseases, especially immunocompromised and those who may stay hospitalized for long period of time. LD is acquired by inhalation of aerosols contaminated with Legionella spp. or less commonly by aspiration of contaminated drinking water. Previous work in the Microbiology Research Laboratory at AQU has shown high prevalence of Legionella spp. in the water and biofilm samples collected from eight hospitals in the West Bank over a two-year period December 2012- December 2014, by using culture method and 16S rRNA-based PCR. Moreover study of the prevalence of L. pneumophila in 195 respiratory samples (sputum or Broncho alveolar lavage (BAL)) by culture yielded only one positive. However, by PCR, 23% (44/195) of the respiratory samples were positive for L. pneumophila. BAL presented a higher percentage 35% (26/74) than sputum 15% (18 /121). Molecular diagnosis of L. pneumophila is well established and adopted worldwide especiallythat culture methods are time consuming and less efficient. Furthermore, genotyping of L. pneumophila is important for epidemiological investigation and control of legionellosisoutbreaks. The current gold standard for L. pneumophila genotyping is Nested PCR Sequence Based Typing (NPSBT), based on the sequence of seven loci (flaA, pilE, asd, mip, mompS, proA and neuA). NPSBT allows the Sequence Typing (ST) of L. pneumophila in the absence of isolates. This high-resolution molecular typing tool is recommended by the European Working Group for Legionella Infections (EWGLI). The previous results in the Microbiology Research Laboratory entitled the use of NPSBT to be able to do epidemiological typing of the respiratory samples in the absence of isolates and to relate the ST’s of environmental samples previously collected from the same hospital with the ST of the respiratory samples to evaluate possible nosocomial infection. The overall goal of this study was to determine the Sequence types (ST’s) of the PCR positive respiratory samples by NPSBT method. Also to determine the ST’s of the environmental samples obtained from the same hospital ward. Our sample study included a subset (34 samples) out of the 44 respiratory samples previously tested positive by PCR targeting 16S rRNA for L. pneumophila. These thirty-four positive samples were further subtyped by NPSBT method. Also DNA previously extracted from 15 biofilm samples previously collected from Makassed hospital wards and tested positive for L. pneumophila was also analyzed by NPSBT. Analysis of the seven allele profiles for the NPSBT of the 34 selected respiratory samples showed a full 7-allele profile for 3 /34 (8.8 %) specimens, a further 18/34 (52.9%) gave 5- or6-allele profiles (sufficient to identify the strain as one or two sequence types (ST’s), 6/34 (17.6%) gave 3- or 4-allele profiles (usually enough to differentiate different profiles), and 5 /34 (14.7%) gave 1- or 2-allele profiles (sufficient to distinguish strains). Overall, 24/34 (70%) samples gave ≥ 4 alleles profiles (4, 5, 6 and 7 alleles). However, 10 samples gave < 4 alleles profiles, these samples were excluded from sequencing in order to identify the ST. Analysis of the seven alleles’ products of the selected fifteen environmental samples revealed fourteen samples positive for six to seven alleles and one sample was positive for one allele, this sample was excluded from sequencing in order to identify the ST Sequence analysis showed the following ST’s in the 24 respiratory samples: ST1 (29.1%, 7/24On the other hand, 14 environmental samples typing showed: ST 1(28.6%, 4/14), ST 187 (21.4%, 3/14), one sample of each ST 2070, ST 461 and ST 187 (7.1 %, 1/14), while the rest of samples (28.5%, 4/14) were unspecified Sequence Types. Thus ST1 is the most prevalent sequence type in both the respiratory samples and the environmental samples representing 29.1% and 28.5% respectively. The other ST’s were unique to each type of sample. ST1 is also the most prevalent ST worldwide in clinical and environmental samplesST 461 (25%, 6/24), ST 1037 (4%, 1/24), and (41.9%, 10/24) gave incomplete profile.
الكيمياء الحيوية والاحياء الجزيئية , Biochemistry & Molecular Biology