Avicenna Journal of Clinical Microbiology and Infection
Year:2019 | Volume:6 | Issue:4|Papers Count:9

Background: Staphylococcus aureus is one of the most important pathogens acquired from the hospital and community. Increasing the resistance of S. aureus to antibiotics is a major health concentration, and thus the study of antibiotic resistance in S. aureus is very important. The aim of this study is to determine the typing of methicillin-resistant S. aureus (MRSA) in the region of the ccrB gene by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Methods: One hundred and six S. aureus were isolated from urine, blood, sputum, wound, and the trachea of patients hospitalized in Tehran during (March-April) 2016. Antibiotic susceptibility test was done by the disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI). In addition, molecular typing for staphylococcal cassette chromosome mec (Sccmec) type I-V was performed in MRSA isolates, followed by conducting PCR-RFLP by restriction enzymes BsmI and HinfI in the ccrB gene area. Results: PCR and typing showed that type II SCCmec was 40% (n=20), followed by types III (28, 56%), IVc (12, 24%), I (11, 22%), V (9, 18%) IVa (7, 14%), and IVb (5, 10%). However, SCCmec type IVd was not observed in the isolates. Finally, after the amplification of ccrB gene and RFLP, all isolates the same as the typing method represented types I, II, III, IVa, IVb, and IVc while no type V was detected by this method. Conclusions: The results of this study demonstrated that SCCmec (type I-IV) can be detected by PCR-RFLP in the ccrB gene, but this method identified no type V SCCmec in MRSA.

Background: Beta-lactam resistance is rising in gram-negative bacilli. The aim of this study was to assess the frequency of β-lactamase enzymes, including extended-spectrum β-lactamases (ESBLs), metallo-β-lactamase (MBL), and AmpC beta-lactamase in Escherichia coli isolated from urine samples of the patients referred to medical laboratories in Aliabad. Methods: A total of 780 urine samples were collected from patients suspected of having urinary tract infection (UTI). In positive urine samples, E. coli strains were identified by biochemical tests. The antibiotic resistance pattern was determined by disk diffusion method and phenotypic confirmatory test was performed for detecting ESBLs, MBL and AmpC beta-lactamases producers. Results: Out of 780 urine samples, 250 E. coli strains were isolated from the positive samples. The majority of the isolates (more than 90%) were resistant to ampicillin and amoxicillin. However, imipenem was an effective antibiotic among the isolates. The frequency of the ESBLs, MBL and AmpC beta-lactamases producers were determined to be 40%, 16. 8%, and 30%, respectively. Conclusions: In this study, the high frequency of MBL and AmpC beta-lactamases may suggest an increasing trend of resistance to cephalosporins and carbapenems. This could have a great impact on the management of UTI cases in and out of hospital. It seems that continuous monitoring is highly essential in detecting resistant cases.

Background: The molecular dynamics simulations have provided detailed information on the fluctuations and conformational changes of proteins. Mutation of GLu349 of diphtheria toxin (DT) to Lys inhibits the molecular cytotoxicity in mammalian cells. In this work, we thus aimed to evaluate the effects of the mutation on the structure and the conformation of DT using molecular dynamic simulations. Methods: PYMOL system was used for introducing the mutant amino acid to DT. Three dimensional structures were visualized using YASARA. The protonation fixing process was done using H++ server. SPD viewer was then applied to retrieve missing hydrogen atoms. Molecular dynamic simulations were also carried out using GROMACS software. Finally, RMSF, Rg, and RMSD graphs were drawn by Sigma Plot using GROMACS outputs. Results: The results of our analysis indicated that amino acid residue fluctuations in the catalytic domain (C) of DT were greater than those of its mutant (E349K). Moreover, residue fluctuations in the region, including Ile344-val347, Tyr514-Ser525, and Ile533-Lys534 of DT were greater than those of the mutant (E349K). However, residue fluctuations in the region including Cys186-Cys201 and Glu349-Val351 of DT were lower than those of E349K. In addition, the disulfide bridge (Cys186– Cys201) was formed in DT, whereas it was not observed in the mutant. The secondary structure analysis showed that the beta-sheet content of E349K decreased compared with DT. Additionally, the conformation of DT was different from that of E349K in the hinge loop regions (Ala379– Thr386 and Tyr514-Ser525). The radius of gyration (Rg) and the root mean square deviation (RMSD) of E349K were greater than those of DT. The conformational stability and compactness of DT were higher than those of E349K. Conclusions: The method used in this study can demonstrate the structural details of toxins as important aspects to predict activities of the receptor binding and the catalytic domains. Therefore, it can be used to evaluate conformational changes of toxins as well as other vaccine candidates.

Background: Staphylococcus aureus is one of the most important human pathogens that produces a wide range of toxins and causes various diseases. Staphylococcal enterotoxin is the most common cause of food poisoning. In addition, S. aureus enterotoxins are classified into 18 serotypes A to U based on serological and biological properties. Methods: The samples were isolated from clinical specimens and identified by routine bacteriological methods. The isolated S. aureus was evaluated by polymerase chain reaction (PCR) for the detection of the genes encoding SEA and SEA. Results: Based on the PCR results, 3 isolates possessed the enterotoxins B (SEB) gene while none of them showed enterotoxins A (SEA) gene. Conclusions: The obtained results revealed that the clinical samples might be a potential source of the enterotoxigenic strains of S. aureus.

Background: Dogs play a significant role in the maintenance of various pathogens in the environment and their possible transmission to humans. In the case of Brucella spp., infected dogs can shed organisms into the environment via urine and vaginal discharges, and aborted materials or feces. This study aimed to investigate the seroprevalence of Brucella sp. infection in dogs in the rural regions of Hamedan, western Iran. Methods: Between June and November 2018, Blood samples were obtained from cephalic or saphenous veins of 180 stray dogs from 6 rural regions of Hamedan during June and November 2018. The sera samples were evaluated for the presence of antibodies against Brucella spp. using Rose Bengal plate test (RBT) and Wright’ s serum agglutination test (Wright SAT). Results: Seroprevalence rate of Brucella infection was 3. 3% by RBT. (6/180; 95% CI: 0. 7%– 5. 9%). All of the serum positive dogs had titers of 1: 80 by Wright SAT. The seropositivity was 3. 1% in males, 3. 4% in females, 3. 2% in <1-year-old, 1. 8% in 1– 2-year-old, and 4. 9% in >2-year-old dogs. No statistically significant correlation was found between the infection rate and gender of dogs (P = 0. 907) or age groups (P = 0. 772). Conclusions: The presence of infected dogs in rural regions is an important risk factor for the transmission of Brucella to humans and livestock. It is suggested that villagers, shepherds, and their families especially children should be provided with the information about risks of getting infection when handling an infected dog.

Background: Leishmaniasis is a vector-borne disease caused by Leishmania species. The transcription factor (NF-κ B) activates and the innate immune system starts working when this parasite attacks macrophages. In addition, glucocorticoids increase nitric oxide (NO) and INFγ leads to the apoptosis of the cell by inhibiting the NF-κ B activity. The aim of this study was the in vitro investigation of the effects of the glucocorticoids on Leishmania major amastigotes. Methods: Leishmania major was produced in a massive volume. Then, promastigotes penetrated into macrophages and converted to amastigotes by adding promastigotes to the J774 mouse macrophage cell line and providing appropriate conditions. Next, the infected macrophages with L. major parasite were treated with different concentrations of prednisolone and mometasone. After 24 and 48 hours, the effect of the drugs was evaluated based on the average number of amastigotes in the infected macrophages. In addition, the amount of NO and the mean interleukin 12 (IL-12) level secreted by the infected macrophages treated with different concentrations of drugs were measured by Griess reagent and ELISA reader, respectively. Results: The average number of amastigotes in the infected macrophages treated with different concentrations of the drug was significantly different from the control group. Further, the amount of NO and the mean level of IL-12 secreted by infected macrophages had a direct and significant relationship with different concentrations of drugs, but the results of Tukey post hoc test showed that the reduction in the number of promastigotes was not time-dependent. Conclusions: In general, prednisolone and mometasone stimulated macrophages increased the IL-12 levels and NO secretion and finally decreased the number of parasites in infected macrophages.

The invention of the microscope was a great help to science to reach a new extension, especially biology. By employing microscopes, the researchers were able to prove new dimensions of living such as a microorganism, work, and cell study, and go in-depth of the minute part of fungi, plants or even the animals. In the mid-20th century, the electron was a great help and opened a new horizon. The scanning microscopes are even more delicate and sophisticated and also have higher magnification power compared to light microscopes. Basically, microscopes utilize the simply visible rays which refract the lenses, X-rays, electron, and infrared rays. In addition, they are designed to detect smaller and smaller particles and structures. Further, scanning electron microscopes are capable of resolving viruses which are extremely smaller than any microorganism and cell, they can enlarge the view of small viruses, which allows the researcher and scientists to develop the cure or a new vaccine for related diseases in animals or even humans. Furthermore, scanning electron microscopes have the power of magnification even till million times, almost molecule size, viruses and also nanoparticles. Moreover, they use software for correcting and enhancing the magnification and resolution of the image. The software helps to view the desired objects even if they are a few molecules thick. This mini-review extensively discusses each type and their different available classifications.

Accurate diagnosis of nosocomial infections is crucial for appropriate antibiotic therapy, as well as avoiding unnecessary use of drugs. Mainly 3 gram-negative bacteria including Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia are involved in nosocomial infections. These bacteria are possibly misdiagnosed with together in traditional diagnostic methods. In this regard, a rapid molecular diagnostic kit was developed in Shiraz Burn Research Center. Using this diagnostic kit, the sensitivity and specificity analyses showed following results, respectively: P. aeruginosa: 100%, 96. 8%; A. baumannii: 100%, 100%, and S. maltophilia: 96. 7%, and 93. 8%. Therefore, this multiplex polymerase chain reaction (PCR) method with 3 primer sequences could be a responsive technique in timely and appropriate detection of studied bacteria.

Dear Editor, Enterococci are gram-positive bacteria and the source of recurrent nosocomial infections with high levels of antibiotic resistance (1), of which we can name resistance to cephalosporins, aminoglycosides, monobactams, penicillinase resistance penicillins, and most importantly, vancomycin (2). Between 85% to 90% of the enterococci infections are caused by Enterococcus faecium (2), and macrolide-lincosamide-streptogramin is an antibiotic, which can be useful for treating enterococcal infections (1). M phenotype refers to a resistance mechanism to macrolides (such as erythromycin) and includes activedrug efflux pumps that are encoded by mef genes (3, 4). For the first time, bacterial antibiotic efflux was reported in 1970 (3). The presence of mef genes have been reported in previous studies (6). In the current study, we reported mefE gene in E. faecium ATCC (American Type Culture Collection) 51559. Acinetobacter baumannii is a gramnegative bacterium that has turned into a great concern in the health care centers especially in intensive care units (4)...