Prevalence of enterotoxin-encoding genes among diverse Shigella strains isolated from patients with diarrhea, southwest Iran

Molecular Mechanisms of Shigella Pathogenesis; Recent Advances

Shigella species are the main cause of bacillary diarrhoea or shigellosis in humans. These organisms are the inhabitants of the human intestinal tract; however, they are one of the main concerns in public health in both developed and developing countries. In this study, we reviewed and summarised the previous studies and recent advances in molecular mechanisms of pathogenesis of Shigella Dysenteriae and non-Dysenteriae species. Regarding the molecular mechanisms of pathogenesis and the presence of virulence factor encoding genes in Shigella strains, species of this bacteria are categorised into Dysenteriae and non-Dysenteriae clinical groups. Shigella species uses attachment, invasion, intracellular motility, toxin secretion and host cell interruption mechanisms, causing mild diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome diseases in humans through the expression of effector delivery systems, protein effectors, toxins, host cell immune system evasion and iron uptake genes. The investigation of these genes and molecular mechanisms can help us to develop and design new methods to detect and differentiate these organisms in food and clinical samples and determine appropriate strategies to prevent and treat the intestinal and extraintestinal infections caused by these enteric pathogens.

In vitro evaluation of the antibacterial effects of Cinnamomum zeylanicum essential oil against clinical multidrug-resistant Shigella isolates

As there are little data about the antimicrobial effects of the cinnamon essential oils (EO) against multidrug-resistant (MDR) Shigella species, this study aimed to evaluate the antibacterial activities of Cinnamomum zeylanicum EO against the clinical MDR Shigella isolates. Totally 50 MDR Shigella isolates including 17 (34%) S. flexneri, 20 (40%) S. sonnei, and 13 (26%) S. boydii were collected. The isolates were identified by standard phenotypic and molecular methods. The MDR phenotypes were determined as resistant to three antibiotic classes using disc diffusion. The C. zeylanicum EO was analyzed by gas chromatography/mass spectrometry (GC/MS). The minimum inhibitory concentration (MIC) of cinnamon EO was evaluated by microtiter broth dilution. The most Shigella isolates 38% (n = 19) were resistant to six antibiotics. The ampicillin-amikacin-cefotaxime-erythromycin-ciprofloxacin-cotrimoxazole resistotype was the most prevalent pattern detected in five S. sonnei, four S. boydii, and three S. flexneri isolates. The result of GC/MS revealed the cinnamaldehyde (84.8%) as the main ingredient of C. zeylanycum EO. The most susceptible strain to the C. zeylanycum EO was S. boydii (MIC range = 0.15-0.62 μl/ml) followed by S. flexneri (MIC range = 0.07-1.25 μl/ml), and S. sonnei (MIC range = 0.15-1.25 μl/ml). The observed ranges of MIC and MBC values of cinnamon EO against Shigella spp. were 0.07-1.25 μl/ml and 0.31-1.25 μl/ml, respectively. The antibacterial effects of cinnamon EO in this study may increase the hope of finding suitable plant compounds to treat infections caused by MDR Shigella isolates.

Investigation of SCCmec types I-IV in clinical isolates of methicillin-resistant coagulase-negative staphylococci in Ahvaz, Southwest Iran

Today methicillin resistant coagulase-negative staphylococci (MR-CoNS) are important in terms of causing significant nosocomial infections. Besides, MR-CoNS are confirmed as the reservoir of SCCmec elements that carry mecA (methicillin-resistant) gene. Hence, the present study was designed to evaluate the susceptibility pattern, prevalence and diversity of SCCmec types I, II, III, and IV in MR-CoNS strains. In this cross-sectional study, 44 clinical isolates of MR-CoNS were identified using the cefoxitin disc method and further confirmation by polymerase chain reaction (PCR) amplification of the mecA gene. Antimicrobial susceptibility of isolates was investigated by disc diffusion. The identification of CoNS was done by amplification and sequencing of the tuf gene. Multiplex PCR method was done for the determination of SCCmec types. In the present study, the Staphylococcus epidermidis and Staphylococcus haemolyticus were the most predominant isolates with a prevalence of 45.4%. The highest resistance rates were observed against erythromycin (84.1%) and clindamycin (75%). Multiplex PCR revealed the SCCmec type I as the predominant type in the present study. Our study showed that there was no significant relationship between the presence of different types of SCCmec elements and resistance to antibiotics. The present study highlighted a frequent prevalence of MR-CoNS harboring SCCmec type genes in Ahvaz, southwest of Iran. Thus, the molecular typing and periodical monitoring of their drug resistance pattern should be considered in national stewardship programs to designing useful antibiotic prescription strategies.

Virulence-Related Gene Distribution Among Shigella Isolates in Anhui, China: The Association with Antimicrobial Resistance

Objective

The aim of this study was to investigate the antimicrobial resistance profiles and distribution of virulence-related genes (VRGs) among Shigella isolates in Anhui, China, and to identify the correlation between the VRGs and antimicrobial resistance.

Materials and Methods

A total of 525 non-duplicate Shigella isolates (449 S. flexneri, 68 S. sonnei, 3 S. boydii, and 5 S. dysenteriae) were collected in Anhui Province, China between September 2011 and September 2015. The antimicrobial resistance of the strains was determined by the agar dilution method according to CLSI guidelines. The presence of 16 VRGs, including ipaH, ipaA-D, ial, virB, virF, set, sen, icsA, icsB, sigA, sat, pic, and sepA, was evaluated using PCR amplification and sequencing.

Results

Shigella flexneri was the most abundant (85.5%), followed by S. sonnei (13.0%). The proportion of males with S. flexneri was higher than that of females (57% vs 43%; P<0.0001). The most common resistance pattern was the combination of ampicillin, nalidixic acid, and tetracycline for S. flexneri (90.2%) and S. sonnei (94.1%). Resistance to ciprofloxacin and levofloxacin was more common among S. flexneri than among S. sonnei (49.7% vs.19.1%, P<0.0001; 30.5% vs 10.3%, P=0.001, respectively). All the isolates were positive for the ipaH gene, while the set, sat, pic, and sepA genes were not detected among the S. sonnei isolates. Except for sigA and sen, resistance to chloramphenicol and ciprofloxacin was more common among VRG-positive S. flexneri than among VRG-negative S. flexneri (P<0.05). Furthermore, resistance to ceftriaxone and ceftazidime was more frequently detected among sat- and set-positive S. flexneri than among sat- and set-negative S. flexneri (P<0.05). However, gentamicin resistance was more prevalent among VRG-negative (ial, virF, set, sat, pic, and sepA) S. flexneri than among VRG-positive S. flexneri (P<0.05).

Conclusion

Shigella flexneri remains the predominant species in Anhui, China, and the resistance to fluoroquinolones was more widespread among S. flexneri than among S. sonnei. Shigella flexneri strains harboring specific VRGs were associated with antimicrobial resistance. To the best of our knowledge, this is the first report of the correlation between the VRGs and antimicrobial resistance in Anhui, China.

Emergence of multidrug-resistant Shigella species harboring extended-spectrum beta-lactamase genes in pediatric patients with diarrhea from southwest of Iran

Owing to the scarce evidence about the multidrug-resistant (MDR) beta-lactamase-producing Shigella isolates in Iran, this study aimed to evaluate the occurrence of extended-spectrum beta-lactamases (ESBL) and AmpC β-lactamases in Shigella species collected in the southwest of Iran. This study was conducted on Shigella species isolated from stool samples of pediatric patients aged less than 15 years suffering from diarrhea. These isolates were identified by bacteriology tests, serotyping, and polymerase chain reaction (PCR). The antibiotic resistance was determined by disc diffusion. The production of ESBLs and AmpC was investigated by phenotypic confirmatory tests and PCR. In total, 79 Shigella isolates, including 46.8% (n = 37) of S. flexneri and 53.2% (n = 42) of S. sonnei, were isolated, respectively. The most effective antibiotic was imipenem with 93.7% of susceptibility followed by ampicillin (29.1%), and cotrimoxazole (30.4%).The resistance rates of ceftriaxone, ceftazidime, and cefotaxime were 41.8%, 34.2%, and 41.8%, respectively. Also, a total of 57 (72.2%) isolates showed MDR profiles. The phenotypic tests showed that 43.0% (34/79) of isolates can produce ESBLs, and no one was positive for ApmC. The frequency of bla_TEM and bla_CTX-M were 30.4% and 32.9%, respectively, while the bla_PER, bla_SHV, and AmpC genes were not detected. The ESBL-producing isolates had a significant (p-value ˂ 0.05) resistance rate against ceftriaxone, ceftazidime, cefotaxime, cefepime, erythromycin, and amikacin. The significant prevalence of MDR Shigella isolates harboring ESBL genes highlights the need for effective surveillance measures to prevent the more spread of drug resistance among species.

Evaluation of the phytoconstituents of Auricularia auricula-judae mushroom and antimicrobial activity of its protein extract

INTRODUCTION

The growing resistance to antibiotics and the complexity of defeating multi-drug resistant bacteria have led to an increase in the search for novel and effective antimicrobials from various plants. This study aimed to determine the bioactive contents of Auricularia auricular-judae mushroom and evaluate the antimicrobial potential of its protein extract against some selected human bacterial and fungal pathogens which could serve as a lead to the discovery of new antimicrobial agents.

METHODS

The constituents of the A. auricular-judae were evaluated by standard phytochemical analysis methods. The agar well diffusion, micro-broth dilution, and time-kill kinetic assays were used to determine the antimicrobial activity of the extracts against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, yeast (Candida albicans), and dermatophytic pathogens.

RESULTS

The preliminary phytochemical analysis of the extracts revealed the presence of carbohydrate (43.15 %; 38.30 %) proteins (23.75 %; 23.75 %), flavonoids (1.20 %; 0.80 %), alkaloids (0.60 %; 1.00 %), saponin (6.00 %; 2.40 %), tannin (1.65 %; 1.57 %), cyanide (0.24 %; 0.40 %), ash (12.40 %; 10.40 %), moisture (6.00 %;6.00 %), lipids(6.00 %;6.00 %), and fiber (8.70 %; 6.45 %) for the Tris buffer and warm aqueous extracts, respectively. The Tris and warm aqueous protein extracts showed antimicrobial effects toward all the human bacterial pathogens and two fungal isolates.

CONCLUSIONS

This study revealed the potential ability of A. auricula-judae for use as a herbal antimicrobial in the treatment of human bacterial and fungal pathogens.

Molecular characterization of Shigella species isolated from diarrheal patients in Tehran, Iran: phylogenetic typing and its association with virulence gene profiles and a novel description of Shigella invasion associated locus

The present study aims to employ a multiplex PCR-based method for phylogenetic typing of Shigella and determine the frequency of several virulence genes among Shigella phylogenetic clades and species. Species identification, phylogenetic typing of 44 previously diagnosed Shigella isolates, and frequency of virulence genes and loci, virA, virB, virF, ipaBCD, ial, sen, and set1A were investigated through performing several PCR assays. Distribution of virulence genes among Shigella phylogenetic clades and species was determined by the statistical analysis. The identities of 40 isolates out of 44 were confirmed as Shigella, and these isolates were classified in four phylogenetic clades, S1 (7.5%), S2 (52.5%), S3 (20%), and S5 (20%) and 4 species, S. sonnei (52.5%), S. flexneri (22.5%), S. dysenteriae (20%), and S. boydii (5%). The prevalence of virA, virB, virF, ipaBCD, ial, sen, and set1A was determined as 67.5%, 72.5%, 72.5%, 65%, 75%, 40%, and 5%, respectively. The presence of sen, uidA, or set1A was found to be statistically correlated with either of Shigella phylogenetic clades or species. A significant statistically association was also determined between set1A and Shigella phylogenetic clades. Furthermore, the nucleotide sequence of invasion-associated locus (ial) was determined and mapped on Shigella genome through in silico analysis. The current study shows the distribution of Shigella isolates and its key virulence genes within the five recently described phylogenetic clades for the first time in the Asia. This is also the first description of ial nucleotide sequence and its exact location on Shigella genome after its initial identification.