Current pathogens infecting open fracture tibia and their antibiotic susceptibility at a tertiary care teaching hospital in South East Asia.

BACKGROUND: Tibia fractures represent the most prevalent open long-bone injuries. Indiscriminate, extensive, and unnecessary use of antibiotics has led to the emergence of infections caused by multidrug resistant organisms that increase morbidity and mortality. This study evaluated the spectrum of current organisms infecting the open tibia fractures and their antibiotic susceptibility pattern. This research did not alter the exiting practice of the institute to evaluate the current status. METHODS: This was a cross-sectional study on 628 patients presenting with open fractures of the tibia from July 2018 to July 2020. Sampling for three successive culture (and sensitivity) tests were carried out, 1st on specimens taken in the emergency room (upon patient presentation), 2nd in the emergency theatre after initial debridement, and 3rd in the ward between 12 to 14 days post operatively. RESULTS: The average age of the patients was 36.2± 15.4 years, with motor vehicle accidents being the predominant aetiology (72.2%). Results of specimen culture demonstrated that debridement could reduce microbial contamination significantly (P<.05) from 38.5 % to 26.4%. But from the ward sample, the infection rate was 45.1%, while contamination at entering the ward was only 26.4%. The bacteriological study found predominant multidrug-resistant Gram-negative organisms, namely Pseudomonas spp., Escherichia coli, Klebsiella spp., Acinetobacter spp., Enterobacter spp. and Proteus spp. Though Gram-positive Staphylococcus aureus was found significantly in the initial culture, they contributed minimally (1.4%) to infect the fracture site. CONCLUSION: The current study found a predominant shift in the trend toward multidrug-resistant Gram-negative organisms in orthopaedic infection, which was accompanied by a worrying pattern of hospital-acquired infection. These results will help to inform future research and policies within our institution.

Cytosine methylation is associated with RNA silencing in silenced plants but not with systemic and transitive RNA silencing through grafting.

RNA silencing is often associated with methylation of the target gene. The DNA methylation level of transgenes was investigated in post-transcriptionally silenced or non-silenced Nicotiana benthamiana carrying either the 5' region (200 or 400 bp) or the entire region of the coat protein gene (CP, including the 3' non-translated region) of Sweet potato feathery mottle virus. Higher levels of transgene cytosine methylation were observed in both symmetrical (CpG, CpNpG) and non-symmetrical (CpHpH) contexts (CpG>CpNpG>CpHpH) in silenced lines, but there was very lower levels or no transgene methylation in non-silenced lines. RNA silencing was induced in non-silenced scions from silenced rootstocks and spread to the 3' region of the transgene mRNA (Haque et al., Plant Mol. Biol. 2007; 63: 35-47). In this system, transgene methylation levels were analyzed in scions at different time intervals after being grafted onto silenced or non-silenced rootstocks to investigate if transgene methylation was associated with induction or transitivity of RNA silencing. We observed that, there was no change of transgene methylation level in the initial target or in extended regions in scions. These results showed that transgene methylation was associated with RNA silencing in individual transformants, but it was not associated with systemic RNA silencing and/or transitive RNA silencing through grafting.

Analysis of transitive RNA silencing after grafting in transgenic plants with the coat protein gene of Sweet potato feathery mottle virus.

We have previously reported the graft transmission of target specificity for RNA silencing using transgenic Nicotiana benthamiana plants expressing the coat protein gene (CP, including the 3' non-translated region) of Sweet potato feathery mottle virus. Transgenic plants carrying the 5' 200 and 400 bp regions of CP were newly produced. From these plants, two silenced and two non-silenced lines were selected to investigate the manifestation of transitive RNA silencing by graft experiments. Non-silenced scions carrying the entire transgene were grafted onto either 5' or 3' silencing inducer rootstocks. When non-silenced scions were grafted onto 5' silencing inducer rootstocks, RNA silencing was induced in the non-silenced scions and spread toward the 3' region of the transgene mRNA. Similarly, when non-silenced scions were grafted onto 3' silencing inducer rootstocks, RNA silencing was induced in the non-silenced scions, but was restricted to the 3' region of the transgene and did not spread to the 5' region. In addition, results from crossing experiments, involving non-silenced and 3' silencing inducer plants, confirmed the above finding. This indicates that RNA silencing spreads in the 5'-3' direction, not in the 3'-5' direction, along the transgene mRNA.