Journal of Medical Bacteriology
Volume:3 Issue: 3, 2014

Salmonella actively stimulates its own uptake into the epithelial cells by inducing cytoskeleton rearrangements and membrane ruffling triggered by some proteins secreted by Salmonella into the cytosol of the epithelial cells via a type III secretion system (TTSS) encoded by genes of the Salmonella pathogenicity island 1 (SPI-1). hilA is a transcriptional activator encoded on Salmonella Pathogenicity Island 1 (SPI-1) genes. To assess the importance of hilA in a simulation modeling of vertical infection and shedding of S. enteritidis in broiler chickens a long-term experiment was designed. Two groups of 200 fertile eggs were inoculated with 20 colony forming units (CFU) of hilA mutant of S. enteritidis or its parent strain just prior to incubation. Thirty five birds of each group were housed in separate rooms. On days 2, 4, 7, 14, 21, 28 and 35 of age, cloacal swabs from live birds as well as samples from internal organs (intestinal tract, liver and spleen) were evaluated by bacteriological or molecular methods. In most of sampling days colonization and invasion of parent strain S. enteritidis in intestine (especially ceaca) and internal organs of chickens were higher with compared to its hilA mutant but this mutant strain could still colonize in intestinal tract and even invade liver or spleen. Colonization of hilA mutant of S. enteritidis indicated that hilA gene is only one part of the modulators in Salmonella invasion mechanism. The ability of hilA mutant to multiply and persist in host internal organs including ceaca may promise further research for potential of hilA mutant to prevent the initial colonization of the intestinal tract by a virulent S. enteritidis strain.

Clostridium perfringens type C strains cause severe necrotizing enteritis in sheep, calves, goats, pigs and humans. Beta-toxin is introduced to be the essential virulence factor of this microorganism. In the present study, a new method was established for the purification of beta toxin from culture supernatant fluid of C. perfringens type C vaccinal strain. The four steps of the purification scheme involved ammonium sulfate precipitation, cation exchange chromatography (CM- Sepharose), anoion exchange chromatography (DEAECellulose) and gel filtration (Sephadex G-100). Beta toxin was purified about 78-fold from the Sephadex G-100 column with a yield of about 16.7% in terms of lethality of the toxin. The molecular weight of the beta toxin as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was approximately 37 KD. The LD50 for adult mice was 2.21 μg/kg. Human umbilical vein endothelial cells (HUVEC) exposed to CPB showed a cell border retraction, cytoplasmic blebbing, cell shrinkage and cell rounding. The toxin was heat labile and was inactivated by trypsin. In conclusion, the results of this study showed the new protocol is suitable for purification of beta toxin of C. perfringens type C regarding good purity, good yields and high activity of beta toxin.

Staphylococcus aureus (S. aureus) is one of the major virulence factors of hospital and community acquired infections. Healthcare workers can be the host of S.aureus for many months. And it is very important due to the possibility of transmission to patients. The aim of this study was to determine the prevalence of S.aureus nasal carriers, the antibiotic susceptibility pattern and its effective factors on Sina Hospital workers in Tehran, Iran. healthcare workers from different wards of Sina Hospital were studied in Tehran, Iran in 2010. Samples were taken from both nostrils of each individual. After 18-24hr incubation, the isolates were evaluated by gram stain, catalase, coagulase, DNase and manitol salt agar by which staphylococci were isolated. Disk diffusion antimicrobial susceptibility tests against oxacillin, cefoxitin and vancomycin was performed. Finally, by using PCR, the mecA gene was studied in methicillin-resistant strains (MRSA). 34of the 166 workers, were nasal carriers of S. aureus and one of them was MRSA. The ratio of carriers in operating room workers was more than other wards, without significant relationship (p.value>0.05). S.aureus was found in 34.3% of operating room, 13.8% of nurses and 22.7% of licensed and other personnel. There was a significant relationship between occupations and S.aureus carriage (p.value:0.03). According to the low prevalence of S. aureus and MRSA carriers in Sina hospital, it can be said that the role of the hospital staff as a source of infections caused by S. aureus especially is very low.

Gram-Negative bacteria are the most cause of nosocomial infection especially in burned patients. Carbapenem resistant strains can limit seriously the choice of antibiotictherapy. AmpC can make resistance to carbapenem and detection of that can be useful for identification of carbapenem resistant. The aim of this study was identification of ampC in most prevalent cause of nosocomial infection. boronic acid combined with meropenem in combination disc method was used for phenotypic method and PCR was used for molecular identification of ampC. Fifty one strains showed positive results in phenotypic method but 119 strains were harbored ampC gene. Combination disc method with meropenem and boronic acid showed 34.4% sensitivity and 78.5% specificity according to the results of this study. the results of this study were indicated the more prevalent of ampC in carbapenem resistant Gram-Negative bacteria. On the other hand use of boronic acid combined with meropenem showed low sensitivity for detection of ampC.

Reports on the association of nosocomial bacterial infections with indwelling medical devices such as intravenous catheters (IVC) has increased in recent years. The potential to form biofilm on these devices seems to be the main reason for establishment of such infections. The aim of this study was to measure the potential of biofilm formation by bacterial isolates from IVCs. Seventy-one IVCs were collected from hospitalized patients in ICU, NICU, hematology and oncology wards at Taleghani Hospital from Jan 2010 to Jan 2011. The bacterial isolates were identified using the standard biochemical tests and the potential to form biofilms was determined by the microtiter plate assay method (MTP) and colony morphology using Congo red agar plates (CRA). Overall, 54 (71%) IVCs were colonized and 76 bacteria were isolated among which, 64 (84.2%) were coagulase negative staphylococci (CoNS), 3 (3.9%) S. aureus, 3 (3.9%) Enterococcus spp., 2 (2.6%) E. coli and 4 (5.3%) were miscellaneous isolates not further identified. Among the CoNS, biofilm formation was observed in 68.7% and 82.8% of bacteria using MTP and CRA methods, respectively. S. aureus and E. coli isolates also were biofilm producers but Enterococcus and other unknown isolates were biofilm negative. Our results confirm that the prevalent biofilm forming bacteria on IVCs were CoNS and that was the reason for high rates of nosocomial infections.

Staphylococcus aureus colonization has been recognized as one of the most important risk factors for subsequent infections with this microorganism. In this study, we intended to identify all patients who were MRSA-positive upon admission and compare the prevalence of MRSA colonization on different days of study admitted in Imam Reza hospital in Mashhad, Iran. This cross-sectional study was done on 600 admitted patients in Infectious disease ward. Samples of patients were drawn from patients’ nares (and if they were culture negative, re-cultures were done on days 3, 7 and finally on discharge time. After identification of the isolates, their susceptibility to methicillin was evaluated. Before we collect nasal swabs, patients filled out a survey questionnaire. S. aureus colonization early after hospitalization in infectious ward was observed in 39.8% (n=239) of patients, of which 59% (n=141) were resistant to methicillin. On the third day of admission, S. aureus new colonization rate was 15.8% (n=57), of which 87.7% (n=50) were methicillin resistant. On the seventh day, S. aureus were found in 13% (n=32) patients with 90.6% (n=29) were methicillin-resistant. Upon discharge, 8.2% (n=13) patients were S. aureus positive and 92.3% (n=12) were resistant to methicillin. Most of the carriers had the methicillin resistant strains of bacteria at the time of admission, and the number of colonized patients with resistant bacteria increased in time. The most common risk factors in methicillin-resistant S. aureus carriers were taking antibiotic, history of prior hospitalization and being an intravenous (IV) drug abuser.

Enteroaggregative E. coli (EAEC) is increasingly recognized as a cause of often persistent diarrhea in children and adults in both developing and developed countries. The aim of the present study was to investigate the presence and the frequency of EAEC as etiologic agent of diarrhea in Shiraz. A total of 715 stool samples were collected from patients with diarrhea in Shiraz. Diarrheagenic E. coli were isolated by biochemical tests and culture from 715 stool samples collected from different hospitals. Diarrheagenic E. coli strains isolated from diarrheal stool samples were examined for the detection of the aggR gene by Real time PCR and PCR method. In this study, a total of 101 (14.12%) diarrheagenic E. coli were isolated from 715 stool samples collected from different hospitals. The infected patients were 58 (57%) males and 43 (43%) females. Out of these 101 diarrheagenic E. coli identified, 5 were confirmed as EAEC in patient. The EAEC strains were isolated from 3 of the 43 females (43%) and 2 of the 58 males (57%) with the mean age of 11.4±1.2 age. In this study, 5 EAEC strains were isolated from one patient with bloody diarrhea and 4 patients with watery diarrhea. The high prevalence of EAEC isolates was also found in watery diarrhea. We therefore, recommend the routine isolation and identification of EAEC strains from patient with diarrhea in all the clinical laboratories and other pathotype diarrheagenic E. coli in Iran.

Brucellosis is a zoonotic disease that is widely distributed throughout the developing countries. In this review, an overview of the epidemiological and epizootic status of brucellosis in Islamic republic of Iran is presented. In Iran, the disease was first recognized in 1932, which is now endemic in the entire country. The first animal vaccination program was carried out in 1949. Brucellosis has been found in humans, cattle, sheep, goats, camels, horses, buffaloes, dogs and the prevalence of bovine brucellosis is estimated 0.3%. The successful implementation of a national brucellosis control program requires enough compensation, farmers’ cooperation, accurate diagnosis of infected animals and impetus of health system is required to overcome the disease.