Iranian Journal of Microbiology
Volume:3 Issue: 2, Jun 2011

Streptococcus pneumoniae, a major human pathogen, is closely related to the commensal species S. mitis and S. oralis. S. pneumoniae surface proteins are implicated in virulence and host interaction of this species, but many of them have recently been detected in S. mitis B6 in silico. We tested for the presence of such genes usinga set of eight S. mitis and eleven S. oralis strains from different geographic locations. An oligonucleotide microarray was designed based on the genomes of S. pneumoniae R6 and TIGR4 as well as S. mitis B6 to include 63 cell surface proteins. The S. pneumoniae genes encoding neuraminidases, hyaluronidase and pneumolysin were also included. In addition to comparative genomic hybridization experiments, homologues were identified in silico in the genome of S. oralis Uo5.Results and The results document that many S. pneumoniae related surface proteins are ubiquitously present among the Mitis group of streptococci. All 19 samples hybridized with the pavA probe representing a gene important for adherence and invasion of S. pneumoniae. Only eight genes were not recognized in any strain, including the S. pneumoniae PcpC gene as the only virulence gene of the S. pneumoniae core genome.The fact that only 12 out of 26 genes present in the S. oralis Uo5 genome could be detected by microarray analysis confirms the sequence variation of surface components.

Group A beta-hemolytic streptococcus (GABHS) is an important pharyngotonsillitis etiologic agent in children. The objective of this study was diagnosis of streptococcal pharyngitis based on rapid antigen detection test and conventional pharyngeal culture. The rapid GABHS antigen detection test was compared to culture on blood agar, the gold standard for the diagnosis of this etiologic agent. Streptococcal antigen was detected in pharyngeal specimens of 34.5% of cases by rapid strip test. We detected group A Streptococcus in 17.2% of pharyngeal culture. There was no agreement between two methods (PV < 0.1). The negative pharyngeal culture results are probably due to antibiotic usage in 43.2 % of patients. Positive rapid test results in pharyngeal swab was age dependent (P < 0.05). There was good correlation between observing the "petechia in pharynx of patients" and positive rapid test in pharyngeal swab (P < 0.004). Throat culture results were relatated to previous antibiotic usage (P < 0.03). The rapid test in pharyngeal swab is helpful for rapid diagnosis and treatment of GABHS pharyngitis. Diagnosis of GABHS pharyngitis based on soley clinical findings is misleading in the majority of cases. Petechia observed in pharynx of the cases was highly predictive of streptococcal pharyngitis.

Each year, Enteroviruses infect millions of people and cause different diseases. The agents are usually detected using cell culture. RD (Rhabdomyosarcoma) and L20B (L cells) are among the recommended cells by the World Health Organisation (WHO) for this purpose. Even though cell culture is the most common method used in diagnosing Enteroviruses in stool specimens, this particular method poses some problems, which include false positive or negative results, lack of a unique cell line for diagnosing all Enterovirus types in addition to being time consuming. For these reasons, an attempt was made to find better techniques of Enterovirus detection. RT-PCR (Reverse Transcriptase Polymerase Chain Reaction) is a technique used in place of the cell culture method. In this study, the cell culture method was compared with RT-PCR for detection of Enteroviruses in stool specimens. First, the chloroform treated stool samples were inoculated onto five cell lines, including RD, L20B, Hep-2 (Human Epidermoid carcinoma cell line), Vero (Verde Reno) and GMK (Green Monkey Kidney). The results were then compared with data from Enterovirus detection using the RT-PCR technique.Results and The difference between RT-PCR and cell culture results was significant. Enteroviruses were detected in 24% of specimens using RT-PCR while cell lines could isolate Enteroviruses in just 14.4% of the samples.

Typhoid is a major health problem faced by the developing countries like Pakistan. More than 20 million cases are reported annually worldwide. Currently fluoroquinolones are the drugs of choice to treat typhoid fever. In vivo resistance to fluoroquinolones leading to therapeutic failure is developing rapidly and is becoming a major concern for the clinicians. The objective of this study was to determine the sensitivity pattern of Nalidixic acid over the last four years A descriptive cross sectional study was carried out at the Microbiology Department of the Army Medical College, National University of Sciences and Technology, Rawalpindi from January 2006 to December 2009. All the isolates were dealt with standard microbiological procedures. The antimicrobial sensitivity of Nalidixic acid and Ciprofloxacin was determined using Kirby-Bauer disc diffusion method as per the guidelines of Clinical and Laboratory Standard Institute (CLSI). Out of 240 isolates, 111 were Salmonella typhi and 129 were Salmonella paratyphi A. The resistance of the typhoidal Salmonella to Nalidixic acid has reached significant levels and it seems only a matter of time when hundred percent resistance will be encountered. All isolates were sensitive to Ciprofloxacin on disc diffusion method. Resistance to Nalidixic acid predicting therapeutic failure with fluoroquinolones is on a steady rise.

Isolation of Xanthomonas campestris from soil has a wide range of applications from monitoring of phytopathogenic populations in soil to screening of improved xanthan-producing strains. Identification of Xanthomonas campestris and its pathovars requires pathogenicity tests in addition to phenotypic and molecular characterization. Thirty phenotypic tests were carried out on 57 yellow-pigmented bacterial isolates obtained from soil of cabbage farms after screening on Selective Xanthomonas (SX) agar and transferring on Yeast Malt agar. Absorption spectra of pigments and capability of biopolymer production were determined for the isolates. Some characteristics of the biopolymer produced and presence of a X. campestris-specific gene marker were investigated for nine putative X. campestris isolates. The present study introduces a set of simple phenotypic tests including urease, acid production from sucrose, mucoid growth on 5% sucrose, starch hydrolysis, growth in 4% NaCl, motility and utilization of asparagine as sole carbon and nitrogen source for quick and inexpensive tentative identification of Xanthomonas campestris. Validation of these tests was confirmed in 100% of the cases by characterization of bacterial exopolysaccharide as xanthan and production of genus-specific xanthomonadin pigment. Moreover, tracking of hrc gene among putative X. campestris isolates gave positive results in 80% of cases. The Minimal simple phenotypic tests facilitate the screening and differentiation of putative X. campestris isolates from other false bacterial strains isolated from soil on semiselective SX agar.

Lipases are particularly important due to the fact that they specifically hydrolyze acyl glycerol, oils and greases, which is of great interest for different industrial applications.Materialst and In this study, several lipase-producing bacteria were isolated from wastewater of an oil processing plant. The strain possessing the highest lipase activity was identified both biochemically and sequencing of 16S rRNA gene. Then we increase lipase activity by improving conditions of production medium. Also, lipase from this strain was preliminarily characterized for use in industrial application. The 16S rRNA sequensing revealed it as a new strain of Pseudomonas aeruginosa and the type strain was KM110. An overall 3-fold enhanced lipase production (0.76 U mL-1) was achieved after improving conditions of production medium. The olive oil and peptone was found to be the most suitable substrate for maximum enzyme production. Also the enzyme exhibited maximum lipolytic activity at 45°C where it was also stably maintained. At pH 8.0, the lipase had the highest stability but no activity. It was active over a pH range of 7.0-10.0. The lipase activity was inhibited by Zn2+ & Cu2+ (32 and 27%, respectively) at 1mM. The enzyme lost 29% of its initial activity in 1.0% SDS concentration, whereas, Triton X-100, Tween-80 & DMSO did not significantly inhibit lipase activity. Based on the findings of present study, lipase of P. aeruginosa KM110 is a potential alkaline lipase and a candidate for industrial applications such as detergent, leather and fine chemical industries.

Regarding the importance of finding new antibacterial drugs, screening of plants as a promising resource are now conducted worldwide. In this study, we report the application of a simple previously described method for screening of different plant seeds in order to find the best resources of plant antimicrobial peptides. Total water soluble protein of 10 different plant seeds were extracted and subjected to SDS-PAGE and subsequent agar-overlay bioassays. Standard strains of Staphylococcus aureus, Enterococcus faecium and Escherichia coli were included in the bioassays. This method also was used for total proteins precipitated by Ammonium sulphate which ensure the protein nature of the test substances. Molecular size and the amounts of effective peptides were estimated using Tricin-SDS-PAGE and densitometry. Two different plant seeds showed noticeable antibacterial activities against tested Gram positive bacteria and a moderate inhibitory effect on Gram negative ones. Based on the results of Tricin-SDS-PAGE analysis which were carried out in parallel to bioassays, it was concluded that effective antibacterial substances are peptides with molecular weight of slightly larger than 5 kDa. On the basis of results of agar-overlay experiments and by screening of 10 different herbal seeds, we could introduce seeds of M. sativa L. and Onobrychis sativa Lam., as great sources of putative plant antibacterial peptides. The proposed screening method can be used for screening of large number of different plant seeds and even other parts of the plant body, regarding some necessary modification in total water soluble protein extraction steps.