Molecular investigation of extended-spectrum β-lactamases (ESBLs) genes in the Salmonella isolates obtained from children with acute diarrhea

Salmonellosis is an important public health concern among children in worldwide. Extended-spectrum β-lactams (ESBLs) cause resistance to clinically important beta-lactams which are generally used to treat invasive Salmonella infections. Therefore, the aim of this study was to investigate the presence of SHV, TEM and CTX-M genes in different strains of Salmonella isolated from children with acute diarrhea and to determine their resistance profile. In this cross-sectional study, 300 fecal samples were collected from children referred to the Amirkola Children's Hospital, Babol, Iran. Antibiotic susceptibility testing was done according to the CLSI guideline. ESBLs-producing strains were identified using double disk synergy test method on the Mueller-Hinton agar plates. Multiplex-PCR was performed using oligonucleotide specific primers to detect of SHV, TEM and CTX-M genes. In total, 7% (n; 21/300) salmonella were isolated, which 61.9%, 28.6% and 9.5% were Salmonella typhimurium, Salmonella enteritidis and Salmonella typhi, respectively. The prevalence of the ESBL-producing isolates were 52.4%. M-PCR results showed that 42.8%, 38.1% and 14.3% of isolates were carried CTX-M, TEM and SHV genes, respectively. Also, 18.2% of isolates harbored CTX-M, and TEM genes, simultaneously. The high rate of ESBLs-producing Salmonella strains in the pediatric patients is an alarm. It is also recommended that alternative drugs be used with less resistance, which requires further investigation

Mutation in mgrB is the major colistin resistance mechanism in Klebsiella pneumoniae clinical isolates in Tehran, Iran

Colistin is considered as one of a last resort antimicrobial agent against multidrug-resistant Gramnegative bacteria including Escherichia coli and Klebsiella pneumoniae. However, the recent emergence of colistin resistance (ColR) worldwide that severely restricts therapeutic options is a serious threat to global public health. In this study we have investigated the molecular determinants in ColR K. pneumoniae isolates collected from clinical specimens. A total of 98 E. coli and 195 K. pneumoniae clinical isolates were collected from two hospitals from August 2018 to December 2019 in Tehran, Iran. Colistin susceptibility and minimum inhibitory concentrations (MIC) were determined according to the Clinical and Laboratory Standards Institute by disk diffusion method, and microdilution method, respectively. For isolates with colistin MIC >= 4 mu g mL(-1), PCR was performed for the detection of mcr-1 to mcr-4 genes. Moreover, nucleotide sequences of mgrB, phoP, phoQ, pmrA, and pmrB genes were determined by sequencing. Finally, the transcriptional level of pmrK and pmrC genes was evaluated by quantitative reverse transcription PCR (RT-qPCR). None of the E. coli isolates were resistant to colistin while 21 out 195 K. pneumoniae isolates were identified as resistant, 19 of which carried mutation in the mgrB gene. Three different mutations were observed in the pmrB gene in 3 K. pneumoniae isolates. None of the ColR isolates showed alternations in pmrA, phoP, and phoQ genes. Furthermore, none of the plasmid-encoding genes were detected. Transcriptional level of the pmrK gene increased in all ColR isolates meanwhile, pmrC overexpression was detected in 16 out 21 (76.19%) isolates. Eventually, all ColR isolates were susceptible to tigecycline. Our results demonstrated that the alternation of mgrB gene is the main mechanism related to colistin resistance among ColR K. pneumoniae isolates in this study

Frequency and antibiotic resistance patterns of isolated bacteria from positive blood culture of hospitalized patients

Background: Bloodstream infections are the most important causes of morbidity and mortality in hospitalized patients. Blood culture plays an important role in identifying most of bacterial agents of bloodstream infections. Knowledge about bacterial agents of bloodstream infections and also antibiotic resistance of these bacteria are important. Antibiotic resistance among bacterial agents of bloodstream infection including Acinetobacter, Klebisella, Pseudomonas, Escherichia coli, Enterobacter, Enterococcus, Staphylococcus aureus and Staphylococcus coagulase negative (CoNS) is one of the major challenges faced by physicians in treating. Therefore, this study was aimed to determine the frequency and antibiotic resistant patterns of bacterial isolates from hospitalized patient's blood cultured samples in the hospital, Tehran, Iran. Methods: This research is a descriptive and retrospective study based on recorded data in Shariati hospital laboratory and under the supervision of Tehran University of Medical Sciences. The bacterial isolates were collected from positive blood cultures from October 2013 to March 2014. The frequency of bacterial isolates were determined by phenotypic and biochemical tests. The antibiotic resistance patterns of isolated bacteria were found by disk diffusion agar method. The diameters of inhibition zone were recorded and interpreted according to Clinical and Laboratory Standards Institute (CLSI) 2013. Results: The frequency of bacterial isolates was determined among 595 positive blood cultures as followed: 41% Pseudomonas, 20% Staphylococcus epidermidis, 10% Escherichia coli, 6% Acinetobacter lwoffii, 6% Staphylococcus aureus, 5% Stenotrophomonas, 3% Acinetobacter baumannii. The antibiogram test showed that 96.2% of Acinetobacter lwoffii, 92.8% of Acinetobacter baumannii, 66% of Pseudomonas aeruginosa, 85.7% of Staphylococcus epidermidis, 65% of Staphylococcus aureus, 75% of Klebsiella, 73.7% of Escherichia coli, and 50% of Stenotrophomonas were resistant to imipenem, piperacillin, piperacillin, erythromycin, erythromycin, ciprofloxacin, trimethoprim-sulfamethoxazole, and ceftazidime respectively. Conclusion: The most prevalent bacterial isolate among the blood cultures of patients was Pseudomonas. The patients more than 50 years were more susceptible to blood stream infections. The most bacteria were isolated from the internal medicine department of hospital. The antibiotic resistance was also increasing especially in Acinetobacter, Staphylococcus coagulase negative, Escherichia coil and Klebsiell

Prevalence and molecular mechanisms of colistin resistance in Acinetobacter baumannii clinical isolates in Tehran, Iran

Colistin is one of the last remaining active antibiotics against multidrug resistant Gram-negative bacteria. However, several recent studies reported colistin-resistant (ColR) Acinetobacter baumannii from different countries. In the current study, we investigated molecular mechanisms involved in colistin resistance in A. baumannii isolates from different clinical samples. A total of 110 clinical A. baumannii isolates were collected from two hospitals in Tehran. Minimum inhibitory concentrations (MICs) were determined by broth microdilution according to the Clinical and Laboratory Standards Institute. For the ColR isolates, mutation was detected in pmrA, pmrB, lpxA, lpxC, and lpxD genes using the polymerase chain reaction (PCR) and sequencing. Moreover, the relative expression of the pmrC gene was calculated using quantitative reverse transcription PCR. Three colistin resistant isolates were identified with MIC between 8 and 16 mg/mL and were resistant to all the tested antimicrobial agents. All the three isolates had a mutation in the pmrB, pmrA, lpxA, lpxD, and lpxC genes. Moreover, the overexpression of pmrC gene was observed in all isolates. Our results showed that the upregulation of the PmrAB two component system was the primary mechanism linked to colistin resistance among the studied colistin resistant A. baumannii isolates

Phenotypic and genotypic characterization of Candida species isolated from candideamia in Iran

Background and Purpose: Candidemia is one of the most important fungal infections caused by Candida species. Infections and mortality caused by Candida species have been on a growing trend during the past two decades. The resistance of yeasts to antifungal drugs and their epidemiological issues have highlighted the importance of accurately distinguishing the yeasts at the species level. The technique applied for yeast identification should be fast enough to facilitate the imminent initiation of the appropriate therapy. Candidemia has not been studied comprehensively in Iran yet. Regarding this, the current study aimed to assess the epidemiology of candidemia at Tehran hospitals and compare the results with the previous findings. Materials and Methods: This study was conducted on 204 positive blood cultures obtained from 125 patients hospitalized in several hospitals located in Tehran, Iran, within a period of 13 months. The yeast isolation and species identification were accomplished using several phenotypic methods (i.e., production of germ tube in human serum, culture on CHROMagar Candida, and Corn meal agar containing Tween 80) and molecular methods, such as polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In addition, unknown cases were subjected to PCR sequencing. These methods were then compared in terms of accuracy, sensitivity, and speed of identification. Results: According to the results, C. albicans (62.4%) was the most common isolate, followed by C. parapsilosis (n=36, 17.5%), C. glabrata (n=18, 8.8%), C. tropicalis (n=13, 6.3%), Trichosporon asahii (n=3, 1.5%), C. kefyr (n=2, 1.0%), C. lusitaniae (n=2, 1.0%), C. intermedia (n=1, 0.5%), C. guilliermondii (n=1, 0.5%), and C. krusei (n=1, 0.5%), respectively. Conclusion: As the findings indicated, the most common species causing candidemia were C. albicans, C. parapsilosis, and C. glabrata, respectively. Children less than one year old and people with cancer were at higher risk for candidemia, compared to other groups. Moreover, phenotypic and molecular methods resulted in the identification of 65.2% and 96.6% of the isolates, respectively. Consequently, PCR-RFLP could be concluded as a more favorable technique for species identification

Evaluation of anti-biofilm potential of biosurfactant extracted from Nocardia species

Introduction: Bacterial natural products such as biosurfactants and surface-active agents are important compounds which exhibit many applications in the fields of medicine.Aim: The aim of the present study was to isolate and identify Nocardia strains with high biosurfactant production and antibiofilm ability.Materials and methods: In the present study, a biosurfactant producing Nocardia species was isolated and identified by a laboratory method. Nocardia species were initially screened and then tested for their ability to produce biosurfactant. The oil spreading test and the surface tension measurements showed that one strain was a biosurfactant producer. The strain with the best surface activity results was selected for further studies and identified by 16S rRNA gene sequencing method. Fourier transform infrared spectroscopy (FTIR) and compositional analysis proved a biosurfactant structure.Results: Oil spreading test and blue agar plate test confirmed biosurfactants and extracellular anionic glycolipids. E24% assay using olive oil revealed strong emulsifying characteristic of the extracted biosurfactant with 100% emulsifying strength. FTIR spectrum indicated the presence of aliphatic hydrocarbon chain (lipid) along with the polysaccharide portion, confirming the glycolipid nature of the biosurfactant. The stability of the biosurfactant produced in different conditions was significant. Increasing concentration of BS significantly inhibited Pseudomonas aeruginosa biofilm.Conclusions: N. coubleae can be a representative of the genus Nocardia for the production of biosurfactants with beneficial physicochemical properties

Evaluation of anti-biofilm potential of biosurfactant extracted from Nocardia species

Introduction: Bacterial natural products such as biosurfactants and surface-active agents are important compounds which exhibit many applications in the fields of medicine.Aim: The aim of the present study was to isolate and identify Nocardia strains with high biosurfactant production and antibiofilm ability.Materials and methods: In the present study, a biosurfactant producing Nocardia species was isolated and identified by a laboratory method. Nocardia species were initially screened and then tested for their ability to produce biosurfactant. The oil spreading test and the surface tension measurements showed that one strain was a biosurfactant producer. The strain with the best surface activity results was selected for further studies and identified by 16S rRNA gene sequencing method. Fourier transform infrared spectroscopy (FTIR) and compositional analysis proved a biosurfactant structure.Results: Oil spreading test and blue agar plate test confirmed biosurfactants and extracellular anionic glycolipids. E24% assay using olive oil revealed strong emulsifying characteristic of the extracted biosurfactant with 100% emulsifying strength. FTIR spectrum indicated the presence of aliphatic hydrocarbon chain (lipid) along with the polysaccharide portion, confirming the glycolipid nature of the biosurfactant. The stability of the biosurfactant produced in different conditions was significant. Increasing concentration of BS significantly inhibited Pseudomonas aeruginosa biofilm.Conclusions: N. coubleae can be a representative of the genus Nocardia for the production of biosurfactants with beneficial physicochemical properties