International Journal of Medical Microbiology最新文献

Enteroaggregative Escherichia coli (EAEC) strains including those of serogroup O111 are important causes of diarrhea in children. In the Czech Republic, no information is available on the etiological role of EAEC in pediatric diarrhea due to the lack of their targeted surveillance. To fill this gap, we determined the proportion of EAEC among E. coli O111 isolates from children with gastrointestinal disorders ≤ 2 years of age submitted to the National Reference Laboratory for E. coli and Shigella during 2013–2022. EAEC accounted for 177 of 384 (46.1 %) E. coli O111 isolates, being the second most frequent E. coli O111 pathotype. Most of them (75.7 %) were typical EAEC that carried aggR, usually with aaiC and aatA marker genes; the remaining 24.3 % were atypical EAEC that lacked aggR but carried aaiC and/or aatA. Whole genome sequencing of 11 typical and two atypical EAEC O111 strains demonstrated differences in serotypes, sequence types (ST), virulence gene profiles, and the core genomes between these two groups. Typical EAEC O111:H21/ST40 strains resembled by their virulence profiles including the presence of the aggregative adherence fimbriae V (AAF/V)-encoding cluster to such strains from other countries and clustered with them in the core genome multilocus sequence typing (cgMLST). Atypical EAEC O111:H12/ST10 strains lacked virulence genes of typical EAEC and differed from them in cgMLST. All tested EAEC O111 strains displayed stacked-brick aggregative adherence to human intestinal epithelial cells. The AAF/V-encoding cluster was located on a plasmid of 95,749 bp or 93,286 bp (pAA_O111) which also carried aggR, aap, aar, sepA, and aat cluster. EAEC O111 strains were resistant to antibiotics, in particular to aminopenicillins and cephalosporins; 88.3 % produced AmpC β-lactamase, and 4.1 % extended spectrum β-lactamase. We conclude that EAEC are frequent among E. coli O111 strains isolated from children with gastrointestinal disorders in the Czech Republic. To reliably assess the etiological role of EAEC in pediatric diarrhea, a serotype-independent, PCR-based pathotype surveillance system needs to be implemented in the future.

The release of host mitochondrial cardiolipin is believed to be the main factor that contributes to the production of anti-cardiolipin antibodies in syphilis. However, the precise mechanism by which mitochondria release cardiolipin in this context remains elusive. This study aimed to elucidate the mechanisms underlying mitochondrial cardiolipin release in syphilis. We conducted a cardiolipin quantitative assay and immunofluorescence analysis to detect mitochondrial cardiolipin release in human microvascular endothelial cells (HMEC-1), with and without Treponema pallidum (Tp) infection. Furthermore, we explored apoptosis, a key mechanism for mitochondrial cardiolipin release. The potential mediator molecules were then analyzed through RNA-sequence and subsequently validated using in vitro knockout techniques mediated by CRISPR-Cas9 and pathway-specific inhibitors. Our findings confirm that live-Tp is capable of initiating the release of mitochondrial cardiolipin, whereas inactivated-Tp does not exhibit this capability. Additionally, apoptosis detection further supports the notion that the release of mitochondrial cardiolipin occurs independently of apoptosis. The RNA-sequencing results indicated that microtubule-associated protein2 (MAP2), an axonogenesis and dendrite development gene, was up-regulated in HMEC-1 treated with Tp, which was further confirmed in syphilitic lesions by immunofluorescence. Notably, genetic knockout of MAP2 inhibited Tp-induced mitochondrial cardiolipin release in HMEC-1. Mechanically, Tp-infection regulated MAP2 expression via the MEK-ERK-HES1 pathway, and MEK/ERK phosphorylation inhibitors effectively block Tp-induced mitochondrial cardiolipin release. This study demonstrated that the infection of live-Tp enhanced the expression of MAP2 via the MEK-ERK-HES1 pathway, thereby contributing to our understanding of the role of anti-cardiolipin antibodies in the diagnosis of syphilis.

Background

Aminopenicillins are recommended agents for non-invasive Haemophilus influenzae infections. One of the mechanisms of resistance to β-lactams is the alteration of the transpeptidase region of penicillin binding protein 3 (PBP3) which is caused by mutations in the ftsI gene. It was shown that exposure to beta-lactams has a stimulating effect on increase of prevalence of H. influenzae strains with the non-enzymatic mechanism of resistance.

Objectives

The aim of our study was to compare the mutational potential of ampicillin and cefuroxime in H. influenzae strains, determination of minimum inhibitory concentration and the evolution of mutations over time, focusing on amino acid substitutions in PBP3.

Methods

30 days of serial passaging of strains in liquid broth containing increasing concentrations of ampicillin or cefuroxime was followed by whole-genome sequencing.

Results

On average, cefuroxime increased the minimum inhibitory concentration more than ampicillin. The minimum inhibitory concentration was increased by a maximum of 32 fold. Substitutions in the PBP3 started to appear after 15 days of passaging. In PBP3, cefuroxime caused different substitutions than ampicillin.

Conclusions

Our experiment observed differences in mutation selection by ampicillin and cefuroxime. Selection pressure of antibiotics in vitro generated substitutions that do not occur in clinical strains in the Czech Republic.

Staphylococcus aureus is a notorious pathogen responsible for various severe diseases. Due to the emergence of drug-resistant strains, the prevention and treatment of S. aureus infections have become increasingly challenging. Vancomycin is considered to be one of the last-resort drugs for treating most methicillin-resistant S. aureus (MRSA), so it is of great significance to further reveal the mechanism of vancomycin resistance. VraFG is one of the few important ABC (ATP-binding cassette) transporters in S. aureus that can form TCS (two-component systems)/ABC transporter modules. ABC transporters can couple the energy released from ATP hydrolysis to translocate solutes across the cell membrane. In this study, we obtained a strain with decreased vancomycin susceptibility after serial passaging and selection. Subsequently, whole-genome sequencing was performed on this laboratory-derived strain MWA2 and a novel single point mutation was discovered in vraF gene, leading to decreased sensitivity to vancomycin and daptomycin. Furthermore, the mutation reduces autolysis of S. aureus and downregulates the expression of lytM, isaA, and atlA. Additionally, we observed that the mutant has a less net negative surface charge than wild-type strain. We also noted an increase in the expression of the dlt operon and mprF gene, which are associated with cell surface charge and serve to hinder the binding of cationic peptides by promoting electrostatic repulsion. Moreover, this mutation has been shown to enhance hemolytic activity, expand subcutaneous abscesses, reflecting an increased virulence. This study confirms the impact of a point mutation of VraF on S. aureus antibiotic resistance and virulence, contributing to a broader understanding of ABC transporter function and providing new targets for treating S. aureus infections.

Objectives

We report a case of bacteremia with pyelonephritis in an adult male with an underlying disease caused by α-hemolytic streptococci. α-Hemolytic streptococci were isolated from blood, but it was challenging to identify its species. This study aimed to characterize the causative bacterium SP4011 and to elucidate its species.

Methods

The whole-genome sequence and biochemical characteristics of SP4011 were determined. Based on the genome sequence, phylogenetic analysis was performed with standard strains of each species of α-hemolytic streptococci. Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values were calculated.

Results

SP4011 showed optochin susceptibility and bile solubility, but did not react with pneumococcal omni antiserum. Phylogenetic analysis of the whole-genome sequence showed that SP4011 clustered with S. pneumoniae and S. pseodopneumoniae and was most closely related to S. pseodopneumoniae. Genomic analysis revealed that ANI and dDDH values between SP4011 and S. pseodopneumoniae were 94.0 % and 56.0 %, respectively, and between SP4011 and S. pneumoniae were 93.3 % and 52.2 %, respectively. Biochemical characteristics also showed differences between SP4011 and S. pseodopneumoniae and between SP4011 and S. pneumoniae. These results indicate that SP4011 is a novel species.

Conclusion

Our findings indicate that SP4011 is a novel species of the genus Streptococcus. SP4011 has biochemical characteristics similar to S. pneumoniae, making it challenging to differentiate and requiring careful clinical diagnosis. This isolate was proposed to be a novel species, Streptococcus parapneumoniae sp. nov. The strain type is SP4011^T (= JCM 36068^T = KCTC 21228^T).

Background

The increasing prevalence of antibiotic-resistant Helicobacter pylori strains poses a significant threat to children's health. This study investigated antibiotic resistance rates in Helicobacter pylori strains isolated from children in Shanghai and analyzed the presence of virulence genes in these strains.

Methods

We obtained 201 Helicobacter pylori strains from pediatric patients with upper gastrointestinal symptoms who underwent gastrointestinal endoscopy between 2019 and 2022. Subsequently, we performed antibiotic susceptibility tests and virulence gene PCR assays on these strains.

Results

Helicobacter pylori resistance rates of 45.8%, 15.4%, 1.0%, and 2.5% were detected for metronidazole, clarithromycin, amoxicillin, and levofloxacin, respectively. Among all isolates, 64.7% exhibited resistance to at least one antibiotic. Resistance to metronidazole and clarithromycin increased from 2019 to 2022. The predominant vacA gene subtype was vacA s1a/m2. The prevalence of vacA m2 and dupA exhibited an upward trend, while oipA presented a decreasing trend from 2019 to 2022. The prevalence of dupA was significantly higher in gastritis than peptic ulcer disease, and in non-treatment compared to treatment groups.

Conclusions

Helicobacter pylori antibiotic resistance remains high in children and has risen in recent years. Therefore, the increasing use of metronidazole and clarithromycin requires increased monitoring in children. No association was observed between antibiotic resistance and virulence gene phenotypes.

Objectives

Staphylococcus aureus (S. aureus) spreads worldwide and occurrence of mastitis caused by it holds significant implications for public health. We aim to reveal the molecular typing, antibiotic resistance and virulence gene profile of S. aureus causing mastitis through investigation.

Methods

A total of 200 isolates of S. aureus were collected from outpatients infected with mastitis in a hospital in Beijing from 2020.7 to 2021.7. The molecular characteristics were analyzed by MLST and spa typing, virulence genes were screened by PCR, antibiotic susceptible test was performed by VITEK® 2 Compact system and phylogenetic analysis was performed by MEGA11 and iTOL.

Results

Nineteen sequence types (STs) belonging to 9 clone complexes (CCs) were identified. ST22 was the most dominant clone (77.0%, 154/200). MRSA accounted for 19.0% (38/200) and 89.5% (34/38) of MRSA isolates belonged to CC22 and CC59. The isolates had relatively low levels of antibiotic resistance, with the exception of β-lactams and macrolides with resistance rates above 50.0%. The carrying rate of pvl in the ST22-MRSA strains were 84.2% and the detection rates of seb and pvl in the MRSA isolates were significantly higher than those in the MSSA isolates, while the hlg, fnbA and sdrD showed opposite results. Whole genome sequenced specimens of MRSA strains X4 and B5 show the same evolutionary origin as ST22 EMRSA-15 (HE681097), which is popular in Europe.

Conclusions

The method based on molecular epidemiology is an important tool for tracking the spread of S. aureus infections. We need to be alert to the major MRSA clones CC22 and CC59 in the region and be vigilant to the possible pandemic and spread of ST22 EMRSA-15.

Preterm infants face a high risk of various complications, and their gut microbiota plays a pivotal role in health. Delivery modes have been reported to affect the development of gut microbiota in term infants, but its impact on preterm infants remains unclear. Here, we collected fecal samples from 30 preterm infants at five-time points within the first four weeks of life. Employing 16 S rRNA sequencing, principal coordinates analysis, the analysis of similarities, and the Wilcoxon rank-sum test, we examined the top dominant phyla and genera, the temporal changes in specific taxa abundance, and their relationship with delivery modes, such as Escherichia-Shigella and Enterococcus based on vaginal delivery and Pluralibacter related to cesarean section. Moreover, we identified particular bacteria, such as Taonella, Patulibacter, and others, whose proportions fluctuated among preterm infants born via different delivery modes at varying time points, as well as the microbiota types and functions. These results indicated the influence of delivery mode on the composition and function of the preterm infant gut microbiota. Importantly, these effects are time-dependent during the early stages of life. These insights shed light on the pivotal role of delivery mode in shaping the gut microbiota of preterm infants and have significant clinical implications for their care and management.

Staphylococcus epidermidis is part of the commensal microbiota of the skin and mucous membranes, though it can also act as a pathogen in certain scenarios, causing a range of infections, including periprosthetic joint infection (PJI). Transcriptomic profiling may provide insights into mechanisms by which S. epidermidis adapts while in a pathogenic compared to a commensal state. Here, a total RNA-sequencing approach was used to profile and compare the transcriptomes of 19 paired PJI-associated S. epidermidis samples from an in vivo clinical source and grown in in vitro laboratory culture. Genomic comparison of PJI-associated and publicly available commensal-state isolates were also compared. Of the 1919 total transcripts found, 145 were from differentially expressed genes (DEGs) when comparing in vivo or in vitro samples. Forty-two transcripts were upregulated and 103 downregulated in in vivo samples. Of note, metal sequestration-associated genes, specifically those related to staphylopine activity (cntA, cntK, cntL, and cntM), were upregulated in a subset of clinical in vivo compared to laboratory grown in vitro samples. About 70% of the total transcripts and almost 50% of the DEGs identified have not yet been annotated. There were no significant genomic differences between known commensal and PJI-associated S. epidermidis isolates, suggesting that differential genomics may not play a role in S. epidermidis pathogenicity. In conclusion, this study provides insights into phenotypic alterations employed by S epidermidis to adapt to infective and non-infected microenvironments, potentially informing future therapeutic targets for related infections.