دو ماهنامه میکروب شناسی پزشکی ایران
سال چهاردهم شماره 5 (مهر و آبان 1399)

Moraxella catarrhalis a gram-negative bacterium, is a significant cause of lower and upper respiratory infections. The RND family efflux pumps lead to multidrug resistance in gram-negative bacteria. One of the well-known pumps in M. catarrhalis is AcrAB-OprM system. This study aimed to investigate the antibiotic resistance in M. catarrhalis and to determine its antibiotic resistance dependence on the efflux pump.

In this study, 137 different clinical samples were collected. M. catarrhalis isolates were confirmed by biochemical assays and PCR. The antibiotic susceptibility pattern was investigated by disc diffusion method according to CLSI. Phenotypic study of the efflux pumps activity was done using cartwheel method. Study of the acra, acrb, and oprm genes were performed by, PCR. In addition, the association of efflux pump with antibiotic resistance was investigated using phenylalanine-arginine β-naphthylamide.

Of 10 isolated M. catarrhalis, 70% (7 isolates) showed multiple antibiotic resistance. The resistance to cefazolin, ceftazidime, tetracycline, chloramphenicol, and ciprofloxacin antibiotics was also dependent on the efflux pump.

The results showed that multiple antibiotic resistance has increased in Moraxella catarrhalis. The 70% presence of acra, acrb, oprm efflux genes of the efflux pumps in this bacterium and antibiotic resistance reduction in the presence of efflux pump inhibitor shows the importance of examining these genes’ presence to suggest a suitable treatment model for the patients infected with M. catarrhalis.

 The widespread consumption of industrial fermented products instead of traditional products leads to the loss of various lactic acid bacteria (LAB), especially the strains producing bioactive compounds. The present study aimed to isolate and molecularly identify LAB and investigate their antifungal impact on Aspergillus niger growth.

Oat bran was purchased from the Gorgan city market in 2019 and sourdough was prepared. Afterwards, bacteria were isolated and identified in the Microbiology Laboratory of Golestan University of Medical Sciences, Gorgan, Iran. Next, the antifungal activity of LAB and their supernatant against A. niger was investigated. Finally, the identification of the cell-free supernatant of LAB was completed using gas chromatography-mass spectrometry.

Findings of the current study demonstrated that Lactobacillus brevis and Lactobacillus sakei had the highest inhibitory effects of 30.25% and 18.47% against A. niger, respectively. Moreover, the minimum inhibitory concentration of L. brevis and L. sakei supernatants against A. niger was found as 3%. We observed that the greater effect of the supernatant of L. brevis could be due to the presence of ester, phenolic, and barbiturate compounds.

According to our results, dominant LAB from oat bran sourdough, as well as their cultured pellets have suitable antifungal potential against A. niger. Therefore, these bacteria can be used as a starter culture or co-culture in the fermentation products process, such as sourdough to decrease fungal contamination.

 The prevalence of Brucella infections in animals and humans has indicated the important need for different regional/local reference laboratories to use valid species-determining approaches to facilitate and compare data exchange. The purpose of current study was to evaluate the RNA Polymerase Beta Subunit (rpoB) as a molecular marker in Brucella species differentiation and to determine the genotype of Brucella melitensis species using single-nucleotide polymorphism (SNP) analysis.

  In this study, blood and cerebrospinal fluid (CSF) samples were taken from 108 patients with brucellosis. After culturing the samples insupplemented Brucella agar, eleven isolates of Brucella bacteria were isolated and identified by classical and molecular biotyping methods. Then the complete sequence of their rpoB gene was multiplied and sequenced. Sequencing results were analyzed by Mega6 program.

   According to the results, the rpoB gene was able to differentiate between Brucella species and other bacteria.Moreover, the rpoB typing grouped the majority of Iranian isolates in the rpoB type 2, while only one strain belonged to the rpoB type 1. Among the 10 isolates of rpoB type 2, there are six different isolates with only one unique type-2 SNPs in codon 985, which gives rise to new genotype 2 variants.

  Our results shown a high discriminative power of rpoB gene among B. melitensis strains from some regions of Iran, which leads to accurate genotype and identification of these bacteria.

 Staphylococcus aureus is one of the most important bacteria causes nosocomial infections, which by the biofilm formation can be effective in the creation of chronic diseases, and the creation and strengthening of drug resistance. The present study aimed to evaluate the genotypic and phenotypic biofilm formation by S. aureus isolated from clinical samples and their association with antimicrobial resistance.

   In this descriptive cross-sectional study from Dec 2019 to Sep 2019, 200 clinical samples were obtained from AJA hospitals in Tehran. All samples were analyzed using blood agar, Baird-Parker Agar, mannitol salt agar and catalase, OF and coagulase assays. Antimicrobial resistance pattern of isolates was determined by the disc diffusion method. Multiplex PCR method was used to identify biofilm formation genes, includes icaA, icaB, icaC, and icaD genes. Data analyzed using SPSS 20 and the X2 test.

Out of 200 cultivated samples, 83 (41.5%) cases were confirmed as S. aureus. The highest resistance was observed to Penicillin (94%), Tetracycline (72%), Ampicillin (54%), and Cefoxitin (51%), respectively. Phenotypic biofilm formation ability reported in 65% of isolates. The frequency of presence of icaA, icaB, icaC, and icaD genes was estimated at 67.4%, 60.2%, 61.4%, and 62.6%, respectively. Eighty-seven percent of biofilm producing strains were multidrug-resistant, while all the biofilm negative strains were non- multiple drug resistance (P< 0/05).

  According to the results, Biofilm-positive strains have a very high propensity to demonstrate antimicrobial resistance, multidrug resistance and resistance to methicillin.

 Some venoms and their isolated compounds have been shown to have antibacterial properties. Snake, scorpion and bee venoms are a complex mixture of proteins such as phospholipase and melittin, which have an effect on bacterial growth inhibition. This study aimed to investigate of antibacterial effect of three different venoms against selected bacterial strains.

Crude venoms obtained from snake (Echis carinatus), scorpion (Mesosobuthus epues) and bee (Apis mellifera) were selected. The crude venoms from these species was purified by using gel filtration chromatography and the molecular weights of the compounds in these venoms estimated by using SDS-PAGE. The approximate lethal dose values of venoms were determined. Antibacterial activity of venoms against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli were evaluated. Venoms and its isolated fractions and standard antibiotic were tested by using the disc diffusion method.

 E. carinatus crude venom and fraction 2 were effective against S. aureus and E. coli.  M. eupeus crude venom and fraction 1 and 4 were effective against B. subtilis. A. mellifera crude venom demonstrated antibacterial activity against E. coli, S. aureus and Fraction 3 of this venom has an inhibition effect for E. coli and S. aureus.

Snake, scorpion and bee venoms inhibit the growth and survival of bacterial strains and that these venoms can be used as a complementary antimicrobial agent against pathogenic bacteria.

 Staphylococcus aureus is one of the most important food-borne pathogens. The objective of this study was to determine the prevalence, molecular types and drug resistance pattern of S. aureus isolated from retail meat in Tabriz city.

 60 raw meat samples (chicken and beef) were taken from different markets and were inoculated in selective Mueller Hinton broth media supplemented with 10% NaCl. Identification of S. aureus isolates was performed using conventional biochemical tests. Susceptibility to different antibiotics and genotypes of isolates were determined by disc diffusion and spa typing methods respectively.

   Fifteen S. aureus strains were isolated from 60 different meat samples which belonged to spa types t14870, t3802, t1814, t491, t386, t3424 and spa type t14870 with the frequency of 33.3% was the most prevalent genotype among S. aureus isolates. spa types of three isolates were not found in Ridom Spa Server data base and were considered as novel types. About 46.6% of isolates were resistant to more than one antibiotic and 13.3% of isolates were identified as methicillin resistant S. aureus (MRSA). Tigecycline, imipenem and ceftaroline were found to be the most effective agents against S. aureus isolates.

  Oure results revealed a 25% contamination rate with S. aureus. Most of the molecular types of isolates were found to be linked to human infections. High rate of antibiotic resistance was observed among the isolates which poses a great threat to public health.

The current study was aimed to evaluate the antibacterial and antioxidant activities of some Saudi Arabia honey products.

For this investigation, sixty Saudi Arabia honey products were tested to determine the antimicrobial activity against highly antibiotic-resistant pathogens as well as antioxidant activity in comparison with Manuka honey as a standard.

Testing Saudi Arabia honeys, different levels of growth suppression were observed against five bacterial strains. The pathogenic strains were Staphylococcus aureusas, Escherichia coli, Proteus vulgaris, Citrobacter diversus and Salmonella enterica. These suppression levels depended on the type of honey. The comparative study of Saudi Arabia honeys revealed a strong correlation between total polyphenol and flavonoid contents and significant radical scavenging activities.

 It was concluded that Saudi Arabia honey products have the capacity to suppress the growth of pathogenic bacteria and perform significant radical scavenging activities.

 Shigella species are one of the most common causes of bacillary dysentery and sometimes death especially in children and immune-compromised individuals. The diversity of disease-causing species and the emergence of drug resistance make it difficult to select the appropriate antibiotic to treat shigellosis. One of the important causes of resistance in Shigella isolates is the presence of genes encoding broad-spectrum beta-lactamase enzymes. The aim of this study was to determine the frequency of Shigella sonnei strains producing CTX-M-2, CTX-M-8, and CMY beta-lactamase genes by Multiplex PCR and to investigate their association with antibiotic resistance in Shigella sonnei strains.

   This descriptive cross-sectional study was conducted in a period of 6 months from the beginning of June to the end of October 2016. A total of 200 diarrhea specimens were collected from the patients with suspected shigellosis from the Childrenchr('39')s Medical Center (Tehran). The antibiotic susceptibility testing was performed using disk diffusion method on Müller-Hinton agar in accordance with CLSI instructions. After DNA extraction, the presence of CTX-M-2, CTX-M-8, and Ampc-dependent CMY genes was determined by Multiplex-PCR using specific primers.

   From all the samples, 60 (30%) Shigella sonnei strains were obtained using standard microbiological and biochemical tests. Majority of the strains were resistant to erythromycin (26 strains, 43.3%) and cefepime (24 strains, 40%). The molecular test results showed that 40 (66.6%) and 33 (55%) of the strains carried the CTX-M-8 and CMY genes, respectively (P<0.05). The CTX-M-2 gene was not detected in any of the samples.

  The results indicate a high frequency of CMY gene among Shigella sonnei isolates and higher resistance of these strains was found against erythromycin and cefepime. Therefore, careful medical care and proper and timely use of appropriate antibiotics to prevent the spread of resistant isolates seems inevitable.