دو ماهنامه میکروب شناسی پزشکی ایران
سال پانزدهم شماره 6 (آذر و دی 1400)

 Recently, coronavirus has become a major cause of death and hospital admission worldwide. This study was aimed to assess the factors associated with the presentation via ambulance and time to in-hospital death or discharge from the hospital using a multilevel joint modeling approach.

 In this historical cohort study, hospitalized patients with COVID-19 were included from 34 medical centers in Khuzestan province, Iran, from February 18th, 2020, to January 5th, 2021. Joint model analysis was used to assess the impact of demographic and clinical characteristics on the mode of hospital presentation and time to death/discharge from hospitals in Khuzestan province, Iran.

 Among 22,356 patients, 14.2% presented to the hospital via ambulance, and 11.2% died in the hospital. The odds of ambulance use was higher in patients with older age, male sex, comorbidities including respiratory disease, diabetes, cancer, and drug abuse, and symptoms such as respiratory distress and loss of consciousness. Older age, male sex, a higher burden of comorbidities, symptoms of chest pain, respiratory distress, and loss of consciousness, and admission to intensive care unit were predictors of in-hospital mortality. The median survival time was longer for patients with COVID-19 who self-presented to the hospital compared to those who presented with ambulance (31 vs 20 days; log-rank P<0.001).

 Several demographic and clinical factors were found to predict the EMS utilization and in-hospital mortality in patients hospitalized with COVID-19 and can be used for risk-stratification. Controlling for the predictors of ambulance use in COVID-19 infection may help improve patient outcomes.

 Staphylococcus aureus is one of the most important human pathogens and common causes of nosocomial and acquired infections in the world. The aim of this study was to investigate antibiotic resistance in methicillin-resistant S. aureus (MRSA) strains and the molecular properties of S. aureus strains.

 For this purpose, a descriptive study was performed in 2017 on 56 strains of S. aureus isolated from clinical specimens. MecA subclasses were also determined by Multiplex RCR reaction. The pvl and spa genes in these strains were determined by PCR reaction.

 The highest resistance of the strains was observed to be to the antibiotics oxacillin, cefoxytime and erythromycin, and vancomycin (12.5%). 100% of methicillin-resistant S. aureus strains contained mecA gene, and more than 50% of isolated strains were associated with nosocomial infections. In addition, 3SCCmec type and 1 SCCmec type were identified as the dominant subtypes in this study and (17.8%). Also, 10 isolated strains could not be typed.

 The results showed that the spa gene distribution was present in 82% of the samples. Out of 46 samples, 40 samples belonged to wound samples. Also, pvl gene was observed in 12% (7 samples) of samples. There is an association between mecA gene and resistance to the antibiotics oxacillin, cefoxitin, and erythromycin in methicillin-resistant S. aureus strains.

 Infectious diseases are one of the leading causes of death in the world. The use of antibiotics, in addition to limitations and side effects, causes the resistance of microorganisms. The use of drug delivery systems is an effective way to increase drug stability and reduce antibiotic use. This study aimed to load cefazolin into a niosomal drug delivery system.

 This study was performed in 2018 to investigate the effect of span 60, tween 60, and cholesterol on the synthesis of niosome nanoparticles loaded with cefazolin by the thin layer hydration method. Then the characteristics of synthetic niosome nanoparticles and their antibacterial activity were investigated.

 SEM images showed that all nanoparticles are spherical. The encapsulation efficiencies for the first, second, and third formulations were 33%, 19.7%, and 40.76%, respectively. The release of cefazolin from the first, second, and third formulations during 30 days was 48%, 81.5%, and 63%. The particle size and zeta potential of the third niosome formulation were estimated to be 154 nm and -24 mV. The MIC for Escherichia coli and Staphylococcus aureus were 4 and 150 μg/mL, respectively. The niosome nanoparticles prepared with the third formulation show an excellent antibacterial effect against Escherichia coli for six days, and the diameter of its growth inhibition zone remains almost constant.

 The optimal formulation of niosome nanoparticles included span 60 (0.060), tween 60 (0.090), and cholesterol (0.046). Continuous and controlled release of cefazolin from the niosome, along with increased drug penetration, reduces the growth of E. coli (ATCC 9637) and S. aureus (ATCC 12600).

 Salmonella typhi as a human pathogen stimulates the human immune system and triggers gene expression changing its pathogenesis. Therefore, we aimed to investigate the expression levels of ifn-γ and tnf-α cytokines in human blood macrophage-like monocytes in dealing with clinical and standard samples of Salmonella typhi in vivo.

 In this cross-sectional descriptive study, a total of 60 stool samples from patients with gastroenteritis were cultured and biochemical tests were used to diagnose Salmonella. Also, venous blood samples were taken for peripheral blood mononuclear cell (PBMC) isolation, and PBMCs were cultured in a culture medium containing 4×103cfu/mL treatments of Salmonella typhi pathogen and standard. Cytotoxicity tests were also performed to determine the concentrations. Finally, quantitative expression levels of ifn-γ and tnf-α were measured and the results were analyzed by statistical tests.

 The results of the cytotoxicity test showed the use of Salmonella typhi concentrations for treatment in an authorized culture medium at a concentration of 4×103 cfu / mL. In comparison to control samples, a significant increased expression levels of tnf-α gene have been detected in pathogen strain and ATCC strain (P<0.05) (P=0.0198). Furthermore, significantly increased expression levels of IFN-γ gene have been detected in the pathogen strain and ATCC strain (P<0.05) in comparison to the control sample (P=0.0001).

 Increased and significant expression of ifn-γ and tnf-α cytokines in the sample group treated with pathogen strain and ATCC strain indicates polarization of macrophages stimulated by Salmonella typhi in vitro.

 The healthy people’s fecal flora in the community represents a large potential reservoir. Therefore, the current study aimed to detect antibiotic resistance patterns and virulence factors in Klebsiella pneumoniae isolated from healthy volunteers’ feces.

 Three hundred and fifty stool specimens were collected from sales rep healthy individuals referring to the Northwest Tehran Health Centers to get a health card. Bacterial isolation, identification, and antimicrobial susceptibility testing were conducted according to the routine instructions. In addition, polymerase chain reaction (PCR) was used to detect the genetic factors responsible for producing extended-spectrum β-lactamases (ESBLs: SHV, TEM, and CTX-M) blaKPC and other virulence genes.

 Among fecal samples analyzed, 60 (17.1%) K. pneumoniae were isolated. The results demonstrated that the highest resistance rate was related to piperacillin-tazobactam (n=25, 41.6%), followed by and meropenem (n=17, 28.8%) and co-trimoxazole (n=11, 18.3%), respectively. Also, all strains were susceptible to amikacin, gentamicin, and imipenem. The PCR results of the virulence gene showed that 95% (n=57) of isolates were positive for fimH gene, 93.33% (n=56) for BssS gene, 27 (45%) for rmpA gene. The PCR results for antibiotic resistance genes showed that 41.66% (n=25) had blaTEM gene, 38.33% (n=23) blaCTX-M gene, 35% (n=21) blaSHV gene and 3.33% (n=2) isolates had blaKPC gene, and none of these isolates carried magA gene.

 Antibiotic resistance was common among K. pneumoniae isolated from healthy volunteers’ feces who participated in this study. Transmission of resistant bacteria and plasmids through oral-fecal sources threats to the public, which could complicate treatment options for community-acquired infections caused by K. pneumoniae.

 The present study aimed to evaluate the optimum conditions for extracting and purifying penicillinase enzyme. The enzyme source was Bacillus licheniformis 6346 obtained from the Iranian Research Organization for Science and Technology.

 B. licheniformis was cultured in a medium containing mineral salts, nitrogen compounds, and cultured carbon sources. Following the harvesting and preparation of bacterial suspension, the destruction of the bacterial cell wall and crude cell extraction was completed using a combination of lysozyme and weak ultrasonication. Afterward, enzyme amount was determined utilizing chromatography and electrophoresis. Furthermore, the optimum growth temperature and incubation time were assessed based on the absorbance of samples at 240 nm, enzyme activity, aerification intensity optimization, enzyme production time, and optimum pH.

 Approximately 8 g of cells were retrieved in one liter of culture. The optimum pH was determined as 6.8. The heat stability evaluation of the enzyme at different times revealed that the enzyme was stable for more than 1 h at 20°C-45°C, while it is inactivated in 10 min at 60°C. Moreover, the best incubation time for this bacterium was obtained as 9 h at 30°C. In terms of aerification intensity, the highest enzyme production rate of 2394 U/mL was achieved in a 250 mL Erlenmeyer flask with a 50 mL culture medium at 200 RPM. More aerification led to the inhibitory effect of oxygen and reduced enzyme activity.

 Our findings showed that the bacterium B. licheniformis 6346 can be used for producing penicillinase enzyme in optimum conditions.

 Enterococcal infections are considered the most common nosocomial infections. Nowadays, enterococci show high resistance to common antibiotics, especially vancomycin. Vancomycin-resistant Enterococcus faecium is one of the most common nosocomial infections, which is included in the World Health Organization priority pathogens list for research and development of new antibiotics. In this case, we focused on the E. faecium EntfacYE genome and its antibiotic-resistant genes to understand the reasons that caused this bacteria to be resistant to antibiotics.

 In total, 25 enterococcal samples were isolated from patients' blood. Bacteriophages were isolated on a multidrug-resistant Enterococcus faecium EntfacYE in our previous study. In this study, the isolated E. faecium EntfacYE strain was verified using Sanger partial sequencing of the bacterial elongation factor Tu. EntfacYE strain was assessed for antibiotic resistance, and the bacterial genome was extracted and completely sequenced. The sequenced genome was analyzed, and the genes were annotated in the DNA Data Bank of Japan.

 Totally, EntfacYE genome subsystems included 23 various categories with 59 genes belonging to antimicrobial resistance genes, such a way that 49 antibiotic resistance genes were included in specific subsystems, while ten genes lacked specific subsystems. Moreover, cadmium, cobalt, copper, zinc, and mercury resistance genes were identified in the EntfacYE genome.

 In conclusion, studies on bacterial genomes help researchers to identify characteristics of common pathogens, including virulence and antibiotic-resistance genes, and hence better understand bacterial pathogenesis to provide novel solutions for the treatment of common infections.

 In the current study, the relevance of the respiratory infection with the age, sex, and seasonal variation of the year were studied side by side with the determination of the responsible bacterial pathogen and their antibiotic sensitivity patterns.

 One hundred sputum samples were collected to determine the causative bacteria of respiratory distress. An antibiotic susceptibility test was done to determine the susceptibility pattern of the isolates.

 The study found six distinct bacteria causing respiratory infections (Pseudomonas spp., Klebsiella spp., Acinetobacter spp., Enterobacter spp. Escherichia coli, and Serratia spp.). Out of 100 isolates, 21 isolates were susceptible to all of the fourteen antibiotics used in the study, and 4 isolates were completely resistant towards all of the antibiotics which were used in the study. The choice of antibiotic was based on the most prescribed medicines given by the doctors of Bangladesh.

Coronavirus infection is nowadays a major public health issue which affected societies and economics worldwide. It is therefore necessary to attempt to conduct research to find how the disease affect the human health. In this regard, the Student Research Committees (SRC), subdivision of research vice-chancellor of Iranian Universities of medical sciences have effectively contributed to provide suitable platform for medical students to learn how to conduct scientific researches. The purpose of this study is to evaluate the studies conducted by student research committees in the field of Covid-19 because Covid-19 is currently one of the most fundamental health issues in the world as well as in our country. This field can increase students' ability to solve problems and gain experience to deal with health challenges and problems. According to the scientometrics system of SRCs of medical universities of the country, the research activity of the SRC of Shahid Beheshti University of Medical Sciences has always been growing, which shows the increased motivation and spirit of cooperation among students of this university in the field of research. In this context, programs and progress of Shahid Beheshti University of Medical Sciences SRC can be considered as a model for other universities to focus on the potential and capability of young student researchers to deal with these concerning health challenges and issues.