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Carbapanem-resistant Klebsiella pneumoniae is a globally healthcare crisis. The distribution of plasmids carrying carbapenemase genes among K. pneumoniae poses a serious threat in clinical settings. Here, we characterized the genetic structure of plasmids harboring major carbapenemases (e.g. blaKPC, blaNDM, blaOXA-48-like, and blaGES) from K. pneumoniae using bioinformatics tools. The plasmids carrying at least one major carbapenemase gene were retrieved from the GenBank database. The DNA length, Inc type, and conjugal apparatus of these plasmids were detected. Additionally, allele types, co-existence, co-occurrence of carbapenemase genes, gene repetition, and sequence types of isolates, were characterized. There were 2254 plasmids harboring carbapenemase genes in the database. This study revealed that blaKPC-2, blaNDM-1, blaOXA-48, and blaGES-5 were the most prevalent allele types. Out of 1140 (50%) plasmids were potentially conjugative. IncFII, IncR, IncX3, and IncL replicon types were predominant. The co-existence analysis revealed that the most prevalent of other resistance genes were blaTEM-1 (related to blaKPC), blaOXA-232 (related to blaOXA-48), bleMBL (related to blaNDM), and aac (6')-Ib4 (related to blaGES). The co-occurrence of carbapenemases was detected in 42 plasmids while 15 plasmids contained carbapenemase gene repetitions. Sequence alignments highlighted that plasmids carrying blaKPC and blaOXA-48-like were more homogeneous whereas the plasmids carrying blaNDM were divergent. It seems that K. pneumoniae utilizes diversity of genetic flexibility and recombination for resistance against carbapenems. The genetic structure of the plasmids showed that class I and III, Tn3 family, Tn5403 family derivatives, and Tn7-like elements were strongly associated with carbapenemases. The mobilizable plasmids carrying carbapenemases play an important role in the spread of these genes. In addition, gene repetition maybe is related to carbapenem heteroresistance. According to MST (minimum spanning tree) results, the majority of plasmids belonged to sequence type (ST) 11, ST14, and ST12. These international clones have a high capacity to acquire the carbapenemase-containing plasmids.

Porphyromonas gingivalis is a primary causative agent of chronic periodontitis. Moreover, it leads to several systemic diseases, including rheumatoid arthritis, cardiovascular, neurodegenerative, and Alzheimer's diseases. It seems that the development of a vaccine against this bacterium is necessary. Thus, this study decided to identify novel immunogenic targets and developed multiple epitope-based vaccines against P. gingivalis. For this purpose, the pan/core-proteome of this bacterium was studied, and the suitable vaccine targets were selected based on different properties, including exposed localization of proteins, antigenicity, non-allergenicity, non-similarity to host proteome, stability, B-cell epitopes and MHC II binding sites, sequence conservation, molecular docking, and immune simulation. Through the quartile scoring method, 12 proteins with ≥ 20 scores were considered as suitable immunogenic targets. The results of the protein domain and functional class search showed that most of the immunogenic proteins were involved in the transport and metabolism of inorganic ions and lipids. In addition, two unknown function proteins, including WP_004584259.1 and WP_099780539.1 were detected as immunogenic targets. Three constructions carrying multi-epitopes were generated including Naked, LCL, and as chimeric structures. Among them, FliC chimeric protein had the strongest affinity to the human TLR2, 4, and 6, while the LCL platform represented the highest level of immune stimulation response. The obtained results from this study revealed new insights into prophylactic routes against P. gingivalis by introducing novel immunogenic targets. However, further investigations, including site-directed mutation and immunoassay are needed to confirm the pathogenic role and protectivity of these novel proteins.

Background Enterobacter is a major nosocomial genus of Enterobacteriaceae responsible for a variety of nosocomial infections, particularly in prolonged hospitalized patients in the intensive care units. Since current antibiotics have failed treating colistin- and carbapenem-resistant Enterobacteriaceae, efforts are underway to find suitable alternative strategies. Therefore, this study conducted a reverse vaccinology (RV) to identify novel and putative immunogenic targets using core proteome of 20 different sequence types (STs) of clinical Enterobacter spp. Moreover, we introduced a structural-based approach for exploration of potential vaccine candidates against the Enterobacteriaceae family using their conserved domain analysis. Results A number of 2616 core coding sequences (CDSs) were retrieved from 20 clinical strains of Enterobacter spp. with a similarity of ≥ 50%. Nine proteins with a score of ≥ 20 considered as the shortlisted proteins based on the quartile scoring method, including three TonB-dependent receptors, WP_008500981.1, WP_058690971.1 and WP_058679571.1; one YjbH domain-containing protein, WP_110108068.1; three flagellar proteins, WP_088207510.1, WP_033145204.1 and WP_058679632.1; one spore-coat U domain-containing protein, WP_039266612.1; and one DD-metalloendopeptidase family protein, WP_025912449.1. In this study, proteins WP_058690971.1 and WP_110108068.1 were detected as the top candidates with regard to immune stimulation and interactions with TLRs. However, their efficacy is remaining to be evaluated experimentally. Conclusions Our investigation introduced common ferrichrome porins with high sequence similarity as potential vaccine candidates against the Enterobacteriaceae family. These proteins belong to the iron acquisition system and possess all criteria of suitable vaccine targets. Therefore, they need to be specifically paid attention for vaccine development against clinically important members of Enterobacteriaceae family.

ObjectivesPertussis remains endemic despite high vaccine coverage in infants and toddlers. Pertussis vaccines confer protection but immunity wanes overtime and boosters are needed in a lifetime. Iran, eligible for the Expanded Program on Immunization that includes the primary immunization, implemented two additional booster doses using a whole-cell vaccine (wPV) at 18 months-old and about 6 years-old. Duration of protection induced by the wPVs currently in use and their impact as pre-school booster are not well documented. This study aimed at assessing vaccination compliance and at estimating the duration of protection conferred by vaccination with wPV in children aged < 15 years in Tehran, Iran.MethodsDetailed information on vaccination history and capillary blood samples were obtained from 1047 children aged 3-15 years who completed the 3 doses-primary pertussis immunization, in Tehran. Anti-pertussis toxin IgG levels were quantified by ELISA.ResultsCompliance was very high with 93.3% of children who received the three primary and 1st booster doses in a timely manner. Timeliness of the 2nd booster was lower (63.3%). Rate of seropositive samples continuously and significantly increased from 1-2 to 5-6 years after 1st booster attaining 30.4% of children exhibiting serological sign of recent contact with B. pertussis. Second booster dating back 1 or 2 years was associated with high antibody titers, which significantly decreased within 3 years from injection. Among children who received 2nd booster injection more than 2 years before serum analysis, seroprevalence of pertussis infection was 8.4% and seropositivity rate was higher from the 10 years-old group.ConclusionSeropositivity in children aged 6-7 years with no 2nd booster supports the need for a vaccination at that age. Adolescent booster may also be considered.