Jundishapur Journal of Microbiology
Year:2017 | Volume:10 | Issue:6|Papers Count:8

Background: Staphylococcus aureus is an opportunistic pathogen that produces many virulence factors, and the most important regulator system of virulence factors expression in these bacteria is the agr system. Expression of virulence factors is not the same under in vitro conditions in standard laboratory medium and in vivo in the host. Objectives: This study aimed at evaluating the effects of adding blood on the virulence genes expression of S. aureus. Methods: In this study, the expression levels of agrA, RNAIII, hla (encoding alpha-toxin), spa (encoding protein A), and mecA (encoding resistance of methicillin) genes were determined during growth of S. aureus isolates in BHI broth and BHI broth, containing 5% sheep blood during different growth phases. The gyrB gene was used as an internal control. Results: The agr system in the BHI broth, containing 5% sheep blood, was active. The expression levels of agrA, RNAIII, hla, and mecA in the stationary phase relative to exponential phase of growth was increased by 2. 95, 5. 7, 2. 7 and 2. 08 folds, respectively. However, the expression of spa gene was decreased by 0. 78 folds. Conclusions: Aside from the growth phase, the expression levels of all of the genes in cultures containing blood relative to BHI broth alone were increased. During encounter with blood cells, the expression profile was similar to that seen in vivo conditions.

Background: Multidrug resistant (MDR) Acinetobacter baumanii strains have emerged as novel nosocomial pathogens threatening patients’ lives, especially in intensive-care units (ICU). Various types of extended-spectrum -lactamases (ESBLs) are involved in conferring resistance to -lactam antibiotics, making their genotypic characterization an essential prerequisite to take proper preventative measures. Objectives: The aim of this study was to determine the antimicrobial susceptibility and prevalence of blaTEM, blaSHV, blaCTX-M, blaOXA-2, and blaOXA-10 genes among A. baumanii isolates obtained from patients in Tabriz city, North-west Iran. Methods: The clinical isolates of A. baumanii were collected from patients hospitalized in the Imam Reza hospital of Tabriz. Antimicrobial susceptibility patterns were determined by the disk diffusion method. The frequency of different ESBLS resistance genes were determined by PCR. Results: Antimicrobial susceptibility testing through the disk diffusion method revealed that the lowest resistance rates were against polymyxin B (16%), colistin (23%), and rifampin (27%); whereas the highest resistance rate was observed against ticarcillin (100%), cefixime (100%), and ceftizoxim (100%). Screening by double disk synergy test showed that 60% of the isolates were ESBL producers. PCR technique on ESBL-positive isolates determined blaSHV gene as the most prevalent (31. 6%) and blaOXA-10 as the least prevalent (8. 3%) among the studied resistance genes. Conclusions: The high prevalence of resistance genes supported the essential role of ESBLs in antibiotic resistance of A. baumanii.

Background: Oral diseasesdependonthe relationshipbetweenhostandvarious species of a bacterialcommunity. The propagation of pathogenic bacteria within the mouth can cause periodontitis. Objectives: In this study, bacterial classifications were performed based on next-generation sequencing (NGS) of 16S ribosomalDNA (rDNA) in order to identify potential bacterial species associated with a periodontal disease in Thai patients. Methods: Dental plaques were collected from healthy controls (n = 5; mean age = 48. 4  4. 5 years) and patients with a chronic periodontitis (n =5; mean age = 47. 4  10. 1 years). Total DNA was extracted and then amplified by specific primers within a V3/V4 region of the 16S rDNA gene. The purified DNA from samples within the same group were pooled together and used to construct DNA libraries with different indexes. High-throughput sequencing with paired-end (250 2) was carried out on a MiSeq platform. Pass-filter sequencing reads (Q 30) were used for bacterial classification. Results: The comparative analysis of healthy controls and patients with a chronic periodontitis revealed that Porphyromonas gingivalis and Prevotella intermedia were significantly associated with a periodontal disease. Other bacteria such as Treponema denticola, T. medium, Tannerella forsythia, P. endodontalis and Filifactor alocis might be potentially associated with the periodontal disease in Thai patients. Conclusions: Several potential bacteria that might be associated with periodontal disease in Thai patients were identified. The obtained data from this study would be useful for understanding the bacterial communities which is responsible for periodontal disease that might be applied for more specific bacteria-targeted antimicrobial therapy of the disease.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has become a great concern to public health as it is one of the most successful and adaptable human pathogens. Antibiotic is still the main treatment for infected patients. Therefore, identifying the prevalence of antibiotic resistant genes is essential to reduce the mortality and morbility rate of MRSA-infected patients. Objectives: This study aimed to identify the prevalence of tetracycline resistance of MRSA and its determinants (tetK and tetM) and their relationship with SCCmec types. Methods: One hundred and seventeen MRSA isolates were collected from different body sites (eg, blood, pus, tissue, synovial fluid, eye, spinal fluid, wound, and nasal cavity) from patients with age of 1-to 90-years old. Antibiotic susceptibility tests were carried out in order to determine tetracycline resistant MRSA. Total DNA was extracted using modified spin column method and subjected to duplex PCR for the amplification of genes of interests (mecA, tetK and tetM) and multiplex PCR for the SCCmec types identification. Results: Out of 117 MRSA isolates, 76. 1% were found to be tetracycline resistant, 8. 5% were intermediate resistant and 15. 4% were susceptible to tetracycline. Among the tetracycline resistant isolates, 97. 8% carried tetM, while 42. 7% carried tetK. The two genetic determinants were found mostly associated with SCCmec type III MRSA, whereby 95. 0% harbored tetM while 37. 0% co-carried tetK. tetK was presented alone (9. 1%) in SCCmec type IV MRSA, although tetMwas found in SCCmec type V MRSA. Conclusions: Tetracycline determinant tetMis more prevalent than tetK in this region of study and most of these determinants are found encoded in SCCmec type III. Since tetracycline antibiotic is losing its efficacy, this antibiotic should be prescribed more wisely.

Background: Streptococcus pneumoniae is a causative agent of morbidity and mortality worldwide. Diagnosis of pneumococcal infection includes conventional culture-based and molecular methods. Differentiation of S. pneumoniae from other mitis group streptococci is not reliable. Objectives: We aimed to evaluate the efficacy of lytB gene along with lytA gene for detection of S. pneumoniae in isolates and clinical samples using conventional and real-time PCR methods. Methods: In this cross-sectional study, a total of 560 clinical specimens were collected from patients during February-September 2015. The samples were cultured on 5% sheep blood agar and suspected colonies were identified by biochemical assays. The antibiotic susceptibility test was performed by disk diffusion and serial microdilution methods. 46 culture-negative and 46 culturepositive samples were examined to evaluate the presence of lytA and lytB genes using conventional and real-time PCR methods. Results: A total of 46 (8. 2%) isolates of S. pneumoniae were identified in suspected specimens. 52% (24/46) of isolates exhibited multiple drug resistance (MDR). All 46 isolates contained both lytA and lytB genes. Real-time PCR assay detected both genes with low CT values in culture-positive samples. Among culture negative specimens, one sample was positive for both the genes. Conclusions: The lytB is similar to lytA in sensitivity for diagnosis of S. pneumoniae in isolates and clinical samples based on both the molecular methods. The results confirmed the applicability of real time PCR based on lytB genes for detection of S. pneumoniae.

Background: The incidence of Clostridium difficile infection (CDI) has markedly increased over the past decade. Although its epidemiology has been previously investigated in tertiary hospitals, no studies have investigated the prevalence of CDI in county level hospitals in China. Objectives: This study aimed at describing the molecular characteristics of toxigenic C. difficile isolated from a community level hospital and evaluating physicians’ knowledge on CDI. Methods: We conducted a 15-month study at a country level hospital to characterize clinical isolates of C. difficile. A total of 61 toxigenic strains were isolated including 54 strains (88. 5%), with both tcdA and tcdB genes positive and the remaining positive for the tcdB gene alone. Results: No binary toxin was detected. The toxigenic strains were found to be susceptible to vancomycin and metronidazole and exhibited high levels of resistance to clindamycin, levofloxacin, erythromycin, and ciprofloxacin. The most toxigenic C. difficile isolate was obtained from the gastroenterology and infection ward. Additionally, 13 sequence types (STs) were identified; ST-54 (32. 8%), ST-3 (16. 4%), ST-35 (13. 1%), and ST-37 (11. 5%) were the most common types. Conclusions: The results of the present study indicate that CDI may be a common problem, and large-scale multicenter studies are required to reveal the actual extent of the burden of CDI in county level hospitals.

Background: Blastocystis is one of the most common anaerobic protozoa found in the intestinal tract of humans and various animals, with a worldwide distribution. The parasite has been linked to the pathogenesis of the irritable bowel syndrome (IBS), previously. Objectives: The aim of this study was to evaluate the prevalence of Blastocystis in IBS patients compared to healthy individuals. Methods: The collected feces from 152 patients with Gastrointestinal (GI) symptoms, and 130 healthy volunteers from Ahvaz, southwest Iran, were examined using the direct saline smear, Lugol’ s iodine staining, and inoculated in a Jones’ medium for Blastocystis detection. The DNA was extracted from all culture-positive samples, and then the polymerase chain reaction (PCR) was performed by the SSU-rDNA gene. Results: Blastocystis was identified in 18 (6. 4%) samples, including two (1. 3%) of the IBS patients and 16 (12. 3%) of the control group by microscopy. Stool culture was positive in 15 with IBS, one without IBS, and 40 control samples. From these, the expected 600 bp fragments of the SSU-rDNA gene were identified in 15 (27. 3%) cases and 40 (72. 7%) controls. Subtypes (STs) 1, 2, and 3 were identified from the 54 successfully sequenced samples. Subtype 3 was the most common ST with the frequency of 46. 3%, followed by ST2, 37% and ST1, 16. 7% in the case and control groups. The highest frequency of Blastocystis STs (27. 8%) was identified in the age group of 31-40 years and the lowest was found in the age groups of under 10 years and over 81 years. Conclusions: The findings of the current studyshowedthat Blastocystis wasmorecommonin the control group compared to the IBS patients. Therefore, our findings highlight the contrast between Blastocystis infection and GI disorders. Furthermore, these results support the hypothesis that Blastocystis could be a GI health marker.

Background: Escherichia coli is one of the mostcommoncauses of different infections. Biofilm structure allows the strains to persist on the biotic and abiotic surfaces for a long time and impairs eradication. Surface colonization of E. coli could be done with several extracellular appendages, which are effective productive events leading to biofilm maturity. Objectives: In this study, the possible relationship between the presence of fimA (encoding large subunit of Type I fimbriae) and csgA (encoding curli fimbriae) genes with biofilm formation in extraintestinal pathogen E. coli isolates was evaluated. Methods: For this study, 35 isolates of E. coli were collected from human urine samples of those referred to oil big hospital. After isolating and identifying E. coli strains by common biochemical tests, we examined the biofilm formation of isolates in brain heart infusion broth, which contained 3% sucrose, using microtiter plate crystal violet method. Presence of the 2 studied genes in the isolates was evaluated using multiplex polymerase chain reaction (m-PCR) assay. Results: In the present study, 27 strains from 35 isolates were expressed in the 2 studied attachment-associated factors, but 5 and 2 strains were expressed by csgA and fimA, respectively. Except 2 strains that could not produce biofilm, 1 strain was detected as a moderate biofilm producer, and the 32 remaining strains were detected as weak biofilm producers. Conclusions: All the positive and the 2 negative biofilm producer strains could be expressed in the 2 studied genes. The correlation between the presence of studied genes and biofilm production ability was suspected, but because of the high percentage of biofilm production in the studied strains, the need to use good hygiene practices is highly recommended.