MOSP - Macao Scientific Publishers

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Investigation of different infectious pathways used by Streptococcus suis type 2 and other bacteria in mice

Xingjian Cao, Zhaoming cao, Guohua Tao, Wei Xie, Xiang Chen and Shuo Wang

Abstract: The purpose of this study was to investigate the infectious pathways used by Streptococcus suis type 2 and enterohemorrhagic Escherchia coli O26 (EHEC O26) in mice. Six-week mice were intraperitoneally injected with mitomycin (0.2 mg/mouse) to decrease the protective immunity. The mice were then challenged with S. suis type 2 and EHEC O26 strains through wounded skin, stomach lavaging and intraperitoneal injection. Enterococcus faecalis ATCC 29212 and E. coli ATCC25922 were used as negative controls. Clinical and microbiological examinations were performed for all the infected mice routinely. The mortality rate of the mice infected with S. suis type 2 strain through wounded skin was 60% within 2 - 5 days. The mortality rate of the mice infected with S. suis type 2 strain through stomach lavaging was 60% within 7 - 10 days. S. suis type 2 can be isolated from the puncturing fluid of heart in the dead mice. Mortality was not observed in mice infected by S. suis type 2 and E. faecalis ATCC 29212 strains through intraperitoneal injection. However, intraperitoneal injection with EHEC O26 and E. coli ATCC25922 caused death of mice within 10 h. We demonstrated an important pathway used by S. suis type 2 strain in mouse infection model. Intraperitoneal injection with gram negative bacteria (E. coli ATCC25922 and EHEC O26) caused non-specific death in mice. These results provided fundamental bases for investigating the pathogenesis of S. suis type 2, designing vaccine and evaluating the efficiency of antimicrobial drugs.[...] Read More.

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Prevalence rate and antibiotic resistant pattern of methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis

Muhammad Arfat Yameen, Hina Nasim, Naeem Akhtar, Saira Iram, Imran Javed and Abdul Hameed*

Abstract: The aim of this study was to evaluate the prevalence rate and antibiotic resistant pattern of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). A prospective study was conducted at Holy Family Hospital Rawalpindi, Pakistan and Microbiology Research Laboratory, Quaid-i-Azam University, Islamabad, Pakistan during the period from December 2007 to August 2008. The antibiotic resistance pattern was studied for MRSA and MRSE isolated from nasal samples from patients admitted in medical and surgical intensive care units. The study was conducted on 283 isolates. The results depicted that 25% isolates of S. aureus were MRSA and 29.78% isolates of S. epidermidis were MRSE. All MRSA and MRSE were susceptible to vancomycin and quinopristin/dalfopristin while all isolates of MRSE were susceptible to teicoplanin. All the isolates of MRSA and MRSE were multidrug-resistant. The susceptibility of the isolates to the drugs varied greatly. The resistance rate of MRSA to various antibiotics was found to be as follow: cephalaxin (90%), cephalothin (58%), cephradine (86%), ciprofloxacin (80%), gentamicin (34%), imipenum (42%), levofloxacin (75%), tetracycline (49%), rifampicin (14%) and teicoplanin (3%). The resistance rate of MRSE to various antibiotics was found to be as follow: cephalaxin (64%), cephalothin (29%), cephradine (64%), ciprofloxacin (50%), gentamicin (21%), imipenum (7%), levofloxacin (21%), tetracycline (21%) and rifampicin (29%). The minimum inhibitory concentration (MIC) value for MRSA and MRSE in case of vancomycin ranged 1-4 g/ml, for tetracycline 4-128 g/ml, for rifampicin 0.5-32 g/ml and for gentamicin 0.5 – 64 g/ml. Both MRSA and MRSE showed variable susceptibility with different antibiotic groups but high susceptibility with streptogramin and glycopeptide antibiotics.[...] Read More.

Keywords: Antibiotic resistance, staphylococcus aureus, staphylococcus epidermidis, minimum inhibitory concentration.

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Preliminary in-vitro antibacterial activities of ethanolic extracts of Ficus sycomorus Linn. and Ficus platyphylla Del. (Moraceae)

Adeshina Gbonjubola Olusesan*, Okeke Claire-Lorentz Ebele, Osuagwu Nonyelum Onwuegbuchulam and Ehinmidu Joseph Olorunmola

Abstract: Antibacterial therapeutic failure due to emergence of resistant bacterial strain is a worldwide phenomenon. The search for effective antibacterial substances from sources such as plants has become a necessity to overcome emergent of bacterial resistant in clinical practice. The dried leaves and stem barks of Ficus sycomorus and Ficus platyphylla were collected in Samaru-Zaria, Nigeria in July 2006 and extracted with 70% aqueous ethanol at room temperature. The antibacterial activities such as susceptibility, Minimum inhibitory concentrations (M.I.C.) and the minimum bactericidal concentrations (M.B.C.) were determined using appropriate methods. Using the same concentration of the two test plants extracts, the zones of inhibition showed by F. sycomorus ranged between 11.5 - 21.5 mm while that of F. platyphylla was from 17.0 - 22.0 mm. The values of the M.I.C and M.B.C of F. sycomorus were 1.95, 31.3 and 3.91, 250 mg/ml, respectively. Similarly, F. platyphylla displayed 1.95 and 7.81 mg/ml M.I.C. values and 3.91 to 62.5 mg/ml M.B.C. values against the test organisms. The observed antibacterial activities in this study proved that the leaves and stem bark extracts of Ficus spp. obtained in Zaria support the forcloric claims of the use of Ficus plants in the treatment of ailment such as wound dressing.[...] Read More.

Keywords: Antibacterial activity, medicinal plants, bacterial resistance, Ficus spp.

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Development and evaluation of colloidal gold immunochromatographic strip for detection of Escherichia coli O157

Xihong Zhao, Xiaowei He*, Wenmei Li , Yao Liu, Liansheng Yang and Jihua Wang

Abstract: Escherichia coli O157:H7 is a serious and common human pathogen that can cause diarrhoea, haemorrhagic colitis, and haemolytic uraemic syndrome (HUS). In this study, the synthesis and identification of colloidal gold particles and antibody-colloidal gold conjugates probe specific to E. coli O157:H7 were performed, and the preparation of colloidal gold immunochromatographic strip based the biotin-streptavidin system was developed for detection of E. coli O157:H7.Monodispersional nanogold colloid was synthesized and preparation of nanogold-labeled polyclonal antibody probe to E. coli O157:H7 by citrate method. Combination of antibody with nanogold particles was also characterized by UV-visible (UV-vis) light absorption spectra and transmission electron microscopy (TEM). Furthermore, nanogold-labeled probe was used to develop an immunochromatographic (IC) strip for E. coli O157:H7 analysis. With this method, analysis could be completed in less than 10 min. Examination of the 65 known strains (36 E. coli O157 strains and 29 serotypes other than E. coli) showed 98.5% specifity and 100% sensitivity, only yield a false-positive reaction with Salmonella choleraesuis . The sensitivity of the IC strip was tested using 10-fold dilution E. coli O157 in foods, could be detected at a minimum of 2.3 × 103 CFU/ml without enrichment and 2.3 CFU/ml after enrichment. Application of IC strip test were performed on 265 water samples, 340 beef samples, 208 milk samples and 120 cake samples after enrichment, the specificity of the strip was 99.2, 97.9, 94.6 and 94.9%, respectively. The sensitivity of the strip was 100% agreement with tradition culture method. The established method is very useful for monitoring E. coli O157 containment in food samples.[...] Read More.

Keywords: Escherichia coli O157, colloidal gold immunochromatographic assay, rapid test.

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The identification of the first isolate of influenza B virus using a duplex RT- PCR DNA sequencing in Saudi Arabia (B/Riyadh/01/2007)

Fahad N. Almajhdi

Abstract: Although Influenza virus infections threaten thousands of lives each year worldwide and bear the risk of been an epidemic, little is known about the circulating strains in Saudi Arabia. The availability of a rapid and accurate diagnostic approach is essential for effective treatment and disease control. In the current study, we optimized a duplex RT-PCR assay for the simultaneous detection of influenza A and B viruses in clinical samples. The developed assay was utilized for testing 100 nasopharyngeal aspirates collected from young children hospitalized with acute respiratory tract infection in Riyadh. Influenza B not A viruses, were identified as possible causes of the disease syndrome. Recovery of influenza B virus from clinical samples was achieved by serial passage in chicken embryos and the virus isolate was designated as Influenza B/Riyadh/01/2007. The identity of B/Riyadh/01/2007 was confirmed by sequencing the RT-PCR product. The sequenced data was submitted to the Gene Bank under the accession number GU135839. An almost complete homology was recognized with all Influenza B virus strains available on Gene Bank. Although several studies suggested the presence of influenza B virus in respiratory tract infection of Saudi children, this is the first report that describes the isolation and partial identification of the circulating virus. Further studies that fully characterize the isolated strain are ongoing.[...] Read More.

Keywords: Influenza B virus, isolation, RT-PCR, DNA sequencing, Saudi Arabia.

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The effect of cultivation conditions on the mycelial growth of a dark-septate endophytic isolate

Ya-li Lv, Li-hua Sun, Fu-sheng Zhang, Yue Zhao and Shun-xing Guo*

Abstract: The EF-37 isolate, one of DSE fungi, is beneficial to the growth and development of its host plant, Saussurea involucrata Kar. et Kir. The cultivation requirements including basic culture medium, temperature, light, pH, carbon source and nitrogen compounds were studied for their effects on mycelial growth of a dark-septate endophytic (DSE) fungus EF-37 by using one-factor-at-a- time method. Potato dextrose agar (PDA) was the best medium for the growth of endophyte EF-37. Our studies showed that 20°C, 24 h dark cultivation and pH 7 significantly influenced the growth of endophyte EF-37 on PDA medium. Moreover, glucose and calcium nitrate were found to be the best nutrients for EF- 37 growth. Under the optimal cultivation conditions, DSE fungus EF-37 isolate could grow actively. This is the first study about the effect of cultivation conditions on the growth of this strain, which provides the preparatory knowledge for the biological characteristics of DSE fungus EF-37.[...] Read More.

Keywords: Cultural conditions, dark-septate endophytic (DSE) fungus EF-37, mycelial growth, optimization, Saussurea involucrata Kar. et Kir.

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Fingerprinting of repetitive DNA sequences in the genus Anabaena using PCR- based techniques

Anbalagan Ezhilarasi* and Narayanaswamy Anand

Abstract: In this study, ten species of Anabaena were used to test the congruence between the traditional morphological classification system and the present molecular classification system. The electrophoretic patterns for 10 cyanobacterial strains belonging to the genera (Anabaena) were used for molecular analysis using the repeated PCR technique. Genetic diversity was assessed using the banding patterns of repetitive DNA sequences including the HIP1 sequences, enterobacterial repetitive intergenic consensus [ERIC] sequences and REP sequences that are present in the cyanobacterial genome. PCR with different sets of repetitive oligonucleotides as primers were used to evaluate the various repetitive DNA sequences. The dendrograms based on the HIP1, ERIC and REP sequences did not show a clear correlation with morphological dendrogram based on traditional classification.[...] Read More.

Keywords: Anabaena, cyanobacteria, highly iterated palindromic sequences, enterobacterial repetitive intergenic consensus sequences, repetitive extragenic palindromic sequences, polymerase chain reaction.

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Antibacterial activity and mechanism of recombinant human - defensin 5 against clinical antibiotic-resistant strains

A. P. Wang, Y. P. Su, S. Wang, M. Q. Shen, F. Chen, M. Chen, X. Z. Ran, T. M. Chen and J. P. Wang*

Abstract: The increasing clinical bacterial strains resistant to conventional antibiotics have being a great challenge to the public’s health. As a novel kind of antimicrobial agent, defensins are undoubtedly worthy of exploitation for the treatment of antibiotic-resistant bacteria. To evaluate the antibacterial potency of recombinant mature human -defensin 5 (rmHD5) against clinical pathogenic strains, we examined its antibacterial kinetics and bactericidal efficacy on forty-nine bacterial strains (belonging to eleven species) with different antibiotic-resistant phenotypes, isolated from digestive and urogenital tracts of the inpatient. Meanwhile, the action mechanism of rmHD5 was analyzed by transmission electron microscopy observation and membrane permeability detection. The peptide of rmHD5 was found to possess high potency against all the tested isolates at concentrations of 6 - 12 g/ml for gram-negative (G-) bacteria and 28 - 32 g/ml for gram-positive (G+) bacteria. G- bacteria were more susceptible to the peptide than G+ bacteria. Abnormal morphological changes and increased permeabilization of the cytomembrane were observed in both G - bacteria and G+ bacteria treated with rmHD5. The antibacterial activity of rmHD5 may be tightly associated with the biomembrane permeabilization. Recombinant mHD5 is a promising candidate to be developed into therapeutic agents for bacterial infections[...] Read More.

Keywords: Antibacterial activity, mechanism, antibiotics resistant strain, human alpha defensin 5.

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Oral colonization and boric acid susceptibility of yeast in boron mineral workers

Zafer Cetinkaya*, Semsettin Karaca , Mustafa Kulac , Ihsan Hakki Ciftci, Gulsah Asık, Osman Cenet and Nuri Kiraz

Abstract: In this study, we aimed to investigate the effects of boron on in vivo oral yeast colonization in study groups which are exposed to boron dust in different sections of the boron mine. The study was carried out in the boron mining areas of two districts (Eskisehir and Balikesir) of Turkey. We included 184 people working in open quarry and stone milling unit, 144 people working in the factory and 150 people as control group. Specimens were taken from four oral mucosal regions and cultured onto Sabouraud dextrose agar. After incubation for 3 - 7 days at 30°C, the total number of yeast colonies on the plates was considered the relative intensity of carriage, and the total number of yeast colonies on the plates was considered the relative intensity of oral carriage. The susceptibility of Candida spp. to boric acid was investigated. The frequency of Candida colonization in boron intensive area workers was found significantly higher than automatic factory workers and control groups (p = 0.012), there were no difference between automatic factory workers and control groups in point of Candida colonization (p = 0.749). We observed that oral yeast colonization had increased directly proportional with boron powder exposure in boron mine (p = 0.005) . Mean minimum inhibitory concentrations (MICs) of boric acid for Boron intensive area, 0.87 - 2.0% for automatic factory and 0.83 - 2.0% for control subjects. We observed that intensive exposure to boron mineral powders was strictly related to oral yeast colonization. Exposure to industrial boron mineral powder may cause important health problems by increasing Candida colonization in oral cavity. It may be useful to do periodical health control in boron mineral workers and population under risk.[...] Read More.

Keywords: Candida, boric acid, boron mineral, oral yeast colonization.

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Antimicrobial activity of various extracts of Centaurea cankiriense A. Duran and H. Duman

Arzu Cansaran, Nazime Mercan Do an*, Mehtap Öztekin and Gülümser Acar

Abstract: The antimicrobial activity was determined using the single disc diffusion method. The hexane, methanol and ethyl acetate extracts were assessed for antimicrobial activity against 13 bacteria and a yeast-like fungus, Candida albicans. While flower extracts of Centaurea cankiriense showed significant antibacterial activity against tested strains, the susceptibility of the test microorganisms was less pronounced in the cases of the stem extracts. Hexane extracts from both flower and stem did not show any antibacterial activity against gram-negative bacteria at test concentration, whereas ethyl acetate and methanol extract of C. cankiriense demonstrated the growth of both the gram-positive and the gram-negative bacteria. But, methanol extract inhibited the bacteria with the exception of two gram-negative bacteria namely Escherichia coli and Klebsiella pneumoniae. Minimum inhibition concentration (MIC) was determined on ethyl acetate extracts of flower and stem that showed high activity against the test bacteria. The MIC values for bacterial strains were in the range of 7.8 - 250 mg/ml. The results confirmed that E. coli (MIC = 250 mg/ml) and Morganelle morganii (MIC = 125 mg/ml) was the most resistant organisms to plant extracts. The flower extract of C. cankiriense was found to possess the strongest effect on Bacillus cereus with 7.8 mg/ml concentration.[...] Read More.

Keywords: Centaurea cankiriense, antimicrobial activity, minimum inhibition concentration, disc diffusion.

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