Search

Objective To isolate, sequence, and identify biological characterization and complete genome sequencing of a virulent Staphylococcus aureus (S. aureus) bacteriophage vB_SauH_IME522. Methods A phage was isolated from sewage of PLA Chinese General Hospital using a clinically isolated S. aureus strain as host bacteria. The double-layer agar plate was used to determine the optimal multiplicity of infection (optimal MOI) and one-step growth curve. Phage morphology was observed by transmission electron microscopy after purification using sucrose gradient separation. Phage DNA was sequenced using the Illumina Miseq sequencing platform. The complete genome sequence was annotated, then comparative genomics and evolutionary analyses were performed. Results A lytic phage of S. aureus was isolated from hospital sewage and named as vB_SauH_IME522. The optimal MOI of the phage was 0.01. One step growth curve showed that its latent period and burst period were 20 and 200 min, respectively. The burst size was about 89 PFU/cell. Electron microscopy displayed the phage having an icosahedral head (70±1) nm and a long contractile tail (135±2) nm. Genome sequencing results showed that the total length of the phage genome was 140 246 bp and the G+C content accounted for 30.2%. The genomic annotation revealed that the phage contained 223 genes coding proteins, 164 putative promoters, 66 terminators, 4 tRNAs, and 7 resistance-related regions. Phylogenetic analysis suggested that the phage was a member of the genus Kayvirus within the subfamily Twortvirinae. Conclusion A lytic phage of S. aureus vB_SauH_IME522 is identified as a new member of the Twortvirinae subfamily, with strong lytic ability and short latent period.

Objective: To evaluate the auxiliary diagnostic value of Japanese respiratory society (JRS) scoring system for the rapid diagnosis of Mycoplasma pneumoniae pneumonia (MP) in inpatients with community acquired pneumonia (CAP)., Methods: The clinical data of inpatients with CAP between January 2013 and Novermber 2013 were retrospectively analyzed. The gold standard for identification of MP infection was determined by both positive culture and real time polymerase chain reaction (PCR) methods. Blood and sputum culture were used to detect other bacteria and fungi, and real time PCR to detect Chlamydia and Legionella pneumonia and the common respiratory viruses. Diagnostic test results consistency inspection was performed by Kappa test and continuous variable analysis was performed using t test., Results: Data from 139 CAP inpatients were analyzed. An aetiological diagnosis was made for 61 patients (43.9%). Thirty-five cases (25.2%) were diagnosed as MP infection by the gold standard, while 72 cases (52.0%) by the JRS scoring system. The sensitivity of JRS scoring system for the diagnosis of MP infection was 85.7% (30/35), specificity 59.6% (62/104), positive predictive value 41.7% (30/72)and negative predictive value 92.5% (62/67). According to age, for the patients younger than 40 years old, the sensitivity of JRS routine scoring system for the diagnosis of MP infection was 24/24, specificity was 4/29, positive predictive value 24/49 and negative predictive value was 4/4., Conclusions: The JRS scoring system provides an auxiliary value for the identification of MP pneumonia. It has a high sensitivity and a strong negative predictive value. For patients younger than 40 yrs with low grades of JRS swring system. MP infection can be almost excluded from.