Background: Shigella continues to be important causes of acute pediatric diarrhea worldwide. Shigella produces numerous virulence factors involved in colonization and invasion into epithelial cells which eventually result in the disease. The present study was conducted to evaluate the prevalence of virulence genes and to investigate antibiotic resistance profiles among Shigella isolates obtained from pediatric patients in Iran. Methods: A total of 141 Shigella isolates were collected between March 2017 and September 2018 from stool of children under 14 who were suspected to have shigellosis. Shigella isolates were identified using standard microbiological and serological tests and antimicrobial susceptibility testing was carried out via Kirby–Bauer disk diffusion method. In addition, the presence of seven virulence determinants including ipaH, ipaB, ipaC, ipaD, ipgD, sen, and virA were evaluated using PCR. Results: S. sonnei (78.7%) was the most prevalent shigella spp. among children with shigellosis followed by S. flexneri (19.9%) and S. boydii (1.4%). Antimicrobial susceptibility testing revealed that most of the isolates were considered as multidrug-resistant (MDR) strains. Our findings also showed a high resistance rate against trimethoprim-sulfamethoxazole in Shigella isolates. The prevalence of ipaH, ipaC, sen, ipaD, virA, ipaB, and ipgD were 100%, 95.7%, 95.7%, 94.3%, 93.6%, 92.9%, and 80.8%, respectively. Conclusion: The current study revealed that S. sonnei was the predominant species isolated from children with shigellosis in Iran. Our results also indicated a high distribution of type III secretion system effector protein-encoding genes and high multidrug-resistance among shigella spp. in Iran. Therefore, it is suggested that antimicrobial susceptibility testing be performed prior to antibiotic prescription.

Background: β-Lactam antibiotics have been broadly used for the treatment of Acinetobacter baumannii infections, resulting in development of β-lactam inactivating β-lactamases. Here, we described antibiotic resistance rate, prevalence of β-lactamase-encoding genes, and clonal relationships of A. baumannii strains isolated from children referred to Children’s Medical Center in Tehran, Iran, during 2019–2020. Methods: A total of 60 non-replicate A. baumannii isolates were recovered from clinical specimens of pediatric patients. Antibiotic susceptibility testing was done by the disc diffusion method. Colistin susceptibility of isolates was performed by the broth microdilution method. β-lactamase-encoding genes were characterized by PCR. The presence of ISAba1 element upstream of the several oxacillinase genes was also checked. Genetic relatedness of isolates was determined by using random amplification of polymorphic DNA (RAPD) typing. Results: The antimicrobial susceptibility tests showed that 83.3% of A. baumannii isolates were MDR, and 40% XDR. Both MDR and XDR A. baumannii isolates were susceptible to colistin. The frequency of bla_OXA-51-like, bla_OXA-23-like, bla_TEM, bla_OXA-24-like, bla_PER, bla_SHV, bla_CTX-M, bla_OXA-58-like, and bla_IMP was 100, 93.33, 60, 36.67, 28.33, 8.33, 5, 3.33, and 1.67%, respectively. Coexistence of ISAba1/bla_OXA-23-like and ISAba1/bla_OXA-51-like was observed in 65% and 85% of isolates, respectively. RAPD analysis revealed 4 common types and 2 single types of A. baumannii isolates. Conclusions: The multiple clones harboring bla_OXA-23-like, ISAba1-bla_OXA-51-like, and ISAba1-bla_OXA-23-like were responsible for the spread of A. baumannii isolates in our clinical wards. Dissemination of the well-established clones is worrisome and would become therapeutic challenges due to the possible transferring genetic elements associated with resistance.

Background: The prevalence of resistance to aminoglycosides among P. aeruginosa isolates has increased all around the world. The resistance is caused through different mechanisms. One of these mechanisms is the use of enzymes such as phosphoryltransferases, acetyltransferases, and nucleotidyltransferases. Objectives: The present study was conducted to determine the prevalence of Aph (3′)-Ib, Aph(6′)-VI, rmtA, aac (6′)-IIa, aadA, aadB, and armA genes among P. aeruginosa strains isolated from burn patients located in Tehran, Iran. Methods: This descriptive study was performed on patients hospitalized at the Shahid Motahari burn hospital during August 2014 to July 2015. Antibiotic susceptibility tests were performed by disc diffusion and minimum inhibitory concentration methods. Aph (3′)-Ib, Aph (6′)-VI, rmtA, aac (6′)-IIa, aadA, aadB, and armA genes were detected by PCR. Results: 60 isolates were evaluated for antimicrobial susceptibility testing. The resistance of P. aeruginosa isolates to the tested antibiotics was as follows: 56 (94%) to ciprofloxacin, 57 (95%) to gentamicin, 57 (95%) to Imipenem, 57 (95%) to meropenem, 56 (94%) to doripenem, 49 (82%) to piperacillin-tazobactam, 58 (97.2%) to amikacin, 45 (75%) to ceftazidime, 59(98%) to Ticarcillin, 56 (93%) to Cefepime, 54 (90%) to piperacillin, 54 (90%) to Aztreonam, and 0 (0%) to colistin. Minimum inhibitory concentration (MIC) for amikacin and Gentamicin was determined according to the guidelines of CLSI. The highest resistance rate according to the MIC method was observed for Gentamicin and amikacin in 128 (40%) and 256 (92%) of the isolates, respectively. In this study, 94% of the isolates were multiple drug resistance (MDR). The prevalence of Aph (3′)-Ib, Aph (6′)-VI, rmtA, aac (6′)-IIa, aadA, aadB, and armA genes were 60%, 85%, 45%, 10%, 87.5%, and 55% according to the PCR, method respectively. Conclusions: This study detected multiple drug resistance (MDR) in P. aeruginosa including aminoglycosides. Therefore, identification of drug resistance patterns in P. aeruginosa is of great importance in prevention and control of infections in burn patient centers. Keywords: P. aeruginosa; Multi Drug Resistance (MDR); Burn Patient; Aminoglycosides; Aminoglycoside-Modifying Enzymes

Background: : The distribution of drug resistance among clinical isolates of Escherichia coli and Klebsiella pneumoniae has limited the therapeutic options. The aim of this study was to report the prevalence of quinolone resistance genes among E. coli and K. pneumoniae clinical strains isolated from three educational hospitals of Tehran, Iran. Materials and methods: : A total of 100 strains of E. coli from Labbafinejad and Taleghani Hospitals and 100 strains of K. pneumoniae from Mofid Children and Taleghani Hospitals were collected between January 2013 and May 2014. Antimicrobial susceptibility tests were done by disk diffusion method based on Clinical and Laboratory Standards Institute guidelines. Detection of qepA, aac(6′)-Ib-cr, acrA, and acrB genes was done by polymerase chain reaction (PCR). Results: : In this study, fosfomycin and imipenem against E. coli and fosfomycin and tigecycline against K. pneumoniae had the best effect in antimicrobial susceptibility tests. PCR assay using specific primers demonstrated that the prevalence of qepA, aac(6′)-Ib-cr, acrA, and acrB genes among the 100 E. coli isolates was 0 (0%), 87 (87%), 92 (92%), and 84 (84%), respectively. The prevalence of qepA, aac(6′)-Ib-cr, acrA, and acrB genes among the 100 K. pneumoniae isolates was 4 (4%), 85 (85%), 94 (94%), and 87 (87%), respectively. Conclusion: : The distribution of qepA, aac(6′)-Ib-cr, acrA, and acrB resistance determinants in E. coli and K. pneumoniae is a great concern. Therefore, infection control and prevention of spread of drug-resistant bacteria need careful management of medication and identification of resistant isolates.

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) causes high rates of mortality and a substantial burden to health systems worldwide. Here, we investigated the antimicrobial susceptibility and molecular characteristics of MRSA isolated from children referred to Children’s Medical Center in Tehran. Materials and methods: A total of 98 MRSA isolates were collected from children. Antimicrobial resistance patterns were determined using the disk diffusion and E-test methods. The presence of biofilm encoding genes and the pvl gene were determined by PCR. We used the microtiter plate method to assess the ability of biofilm formation. The MRSA isolates were further analyzed using PFGE and SCCmec typing. Results: Antibiotic susceptibility testing showed that the highest and the lowest antibiotic resistance percentage were related to erythromycin (62%) and minocycline (10%), respectively. Overall, 63% of MRSA isolates were biofilm producers. Resistance to two antibiotics such as erythromycin (72% vs 28%, P=0.01) and clindamycin (71% vs 29%, P=0.04) was higher among biofilm producers than non-biofilm producers. All strains had biofilm-forming genes and the prevalence of pvl gene was 41%. Most MRSA isolates belonged to SCCmec IVa (75%) and SCCmec III (18%). In PFGE technique, 5 common types and 2 single types were identified; Common type 1 with 37 isolates was dominant clone. Conclusion: We thus report preliminary data on the prevalence and distribution of MRSA genotypes in Tehran Children’s Hospital. These findings characterize the MRSA colonization dynamics in child patients in Iran and may aid the design of strategies to prevent MRSA infection and dissemination.