16S rRNA gene-based identification of bacteria in postoperative endophthalmitis by PCR-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) fingerprinting

Point-of-care microfluidic devices for pathogen detection

The rapid diagnosis of pathogens is crucial in the early stages of treatment of diseases where the choice of the correct drug can be critical. Although conventional cell culture-based techniques have been widely utilized in clinical applications, newly introduced optical-based, microfluidic chips are becoming attractive. The advantages of the novel methods compared to the conventional techniques comprise more rapid diagnosis, lower consumption of patient sample and valuable reagents, easy application, and high reproducibility in the detection of pathogens. The miniaturized channels used in microfluidic systems simulate interactions between cells and reagents in microchannel structures, and evaluate the interactions between biological moieties to enable diagnosis of microorganisms. The overarching goal of this review is to provide a summary of the development of microfluidic biochips and to comprehensively discuss different applications of microfluidic biochips in the detection of pathogens. New types of microfluidic systems and novel techniques for viral pathogen detection (e.g. HIV, HVB, ZIKV) are covered. Next generation techniques relying on high sensitivity, specificity, lower consumption of precious reagents, suggest that rapid generation of results can be achieved via optical based detection of bacterial cells. The introduction of smartphones to replace microscope based observation has substantially improved cell detection, and allows facile data processing and transfer for presentation purposes.

Changes in bacterial diversity associated with bioremediation of used lubricating oil in tropical soils

Used lubricating oil (ULO) is a widespread contaminant, particularly throughout tropical regions, and may be a candidate for bioremediation. However, little is known about the biodegradation potential or basic microbial ecology of ULO-contaminated soils. This study aims to determine the effects of used ULO on bacterial community structure and diversity. Using a combination of culture-based (agar plate counts) and molecular techniques (16S rRNA gene sequencing and DGGE), we investigated changes in soil bacterial communities from three different ULO-contaminated soils collected from motorcycle mechanical workshops (soil A, B, and C). We further explored the relationship between bacterial community structure, physiochemical soil parameters, and ULO composition in three ULO-contaminated soils. Results indicated that the three investigated soils had different community structures, which may be a result of the different ULO characteristics and physiochemical soil parameters of each site. Soil C had the highest ULO concentration and also the greatest diversity and richness of bacteria, which may be a result of higher nutrient retention, organic matter and cation exchange capacity, as well as freshness of oil compared to the other soils. In soils A and B, Proteobacteria (esp. Gammaproteobacteria) dominated the bacterial community, and in soil C, Actinobacteria and Firmicutes dominated. The genus Enterobacter, a member of the class Gammaproteobacteria, is known to include ULO-degraders, and this genus was the only one found in all three soils, suggesting that it could play a key role in the in situ degradation of ULO-contaminated tropical Thai soils. This study provides insights into our understanding of soil microbial richness, diversity, composition, and structure in tropical ULO-contaminated soils, and may be useful for the development of strategies to improve bioremediation.

PCR detection and identification of bacterial contaminants in ocular samples from post-operative endophthalmitis

BACKGROUND

Bacterial endophthalmitis is a sight-threatening complication of ocular surgery which requires urgent medical consideration including comprehensive diagnosis. Polymerase chain reaction (PCR) as a sensitive molecular method has been extensively used for detection of microbial species in clinical specimens.

AIM

The aim of this study was to identify the causative organisms of endophthalmitis in our patient population using a procedure based on PCR.

MATERIALS AND METHODS

Vitreous samples from 32 patients with post-operative endophthalmitis were collected. Total vitreous DNA was extracted and then assessed by agarose gel electrophoresis. Bacterial 16S rRNA gene was amplified from genomic DNA using PCR with a pair of HAD2 universal primers. Library of PCR products from 16S rRNA, cloned into the pTZ57R/T vector. The ligated products were then transformed into E. coli DH5α strain and grown in the LB-ampicillin/X-Gal/IPTG plate.

RESULTS

From the total of 32 vitreous samples, 18 specimens were positive, illustrating the presence of bacterial infection (56.4 %). Twelve species including Escherichia coli, Enterobacter cloacae, Bacillus subtilis, Neisseria gonorrhoeae, Streptococcus pneumoniae, Haemophilus influenzae, Chlamydia trachomatis, Staphylococcus aureus, Neisseria meningitides, Staphylococcus epidermidis, Pseudomonas aeruginosa and Bacillus cereus were identified using BLAST for known 16S rRNA sequences.

CONCLUSION

Polymerase chain reaction (PCR) accompanied with cloning and sequencing approved to be sensitive and specific. The rapid molecular technique was useful in detection of 12 major microbial species, in infectious endophthalmitis.

Identification of torque teno virus in culture-negative endophthalmitis by representational deep DNA sequencing

PURPOSE

To test the hypothesis that uncultured organisms may be present in cases of culture-negative endophthalmitis by use of deep DNA sequencing of vitreous biopsies.

DESIGN

Single-center, consecutive, prospective, observational study.

PARTICIPANTS

Aqueous or vitreous biopsies from 21 consecutive patients presenting with presumed infectious endophthalmitis and 7 vitreous samples from patients undergoing surgery for noninfectious retinal disorders.

METHODS

Traditional bacterial and fungal culture, 16S quantitative polymerase chain reaction (qPCR), and a representational deep-sequencing method (biome representational in silico karyotyping [BRiSK]) were applied in parallel to samples to identify DNA sequences corresponding to potential pathogens.

MAIN OUTCOME MEASURES

Presence of potential pathogen DNA in ocular samples.

RESULTS

Zero of 7 control eyes undergoing routine vitreous surgery yielded positive results for bacteria or virus by culture or 16S polymerase chain reaction (PCR). A total of 14 of the 21 samples (66.7%) from eyes harboring suspected infectious endophthalmitis were culture-positive, the most common being Staphylococcal and Streptococcal species. There was good agreement among culture, 16S bacterial PCR, and BRiSK methodologies for culture-positive cases (Fleiss' kappa of 0.621). 16S PCR did not yield a recognizable pathogen sequence in any culture-negative sample, whereas BRiSK suggested the presence of Streptococcus in 1 culture-negative sample. With the use of BRiSK, 57.1% of culture-positive and 100% of culture-negative samples demonstrated the presence of torque teno virus (TTV) sequences, compared with none in the controls (P=0.0005, Fisher exact test). The presence of TTV viral DNA was confirmed in 7 cases by qPCR. No other known viruses or potential pathogens were identified in these samples.

CONCLUSIONS

Culture, 16S qPCR, and BRiSK provide complementary information in presumed infectious endophthalmitis. The majority of culture-negative endophthalmitis samples did not contain significant levels of bacterial DNA. "Culture negativity" does not seem to be due to failure of growth of fastidious bacteria. The small DNA virus TTV was unexpectedly found in all culture-negative samples and some culture-positive samples. This study cannot distinguish whether TTV is a direct intraocular pathogen, an adjuvant for inflammation, a general marker of inflammation, or a commensal virus but provides a testable hypothesis for a pathogenic mechanism in culture-negative endophthalmitis.

Identification of polybacterial communities in patients with postoperative, posttraumatic, and endogenous endophthalmitis through 16S rRNA gene libraries

Endophthalmitis is a potential vision-threatening complication following surgical procedures (postoperative endophthalmitis [POE]), trauma (posttraumatic endophthalmitis [PTE]), and bacteremic seeding of the eye from a distant infection site (endogenous endophthalmitis [EE]). Several studies have revealed the polybacterial characteristics of endophthalmitis, which make the administration of antibiotics to treat the disease challenging. However, until now, the polybacterial communities of POE, PTE, and EE have not been precisely studied. Hence, the present study was designed to identify the bacterial community of endophthalmitis through 16S rRNA gene libraries. Of the 40 intraocular samples tested, 30 libraries were constructed with bacterial nested-PCR-positive samples. The obtained recombinant clones were screened through amplified rRNA gene restriction analysis (ARDRA) to identify unique clones. The multiple types of ARDRA patterns (P=0.345) and diverse bacterial sequences (P=0.277) within the libraries revealed the polybacterial nature of infection in POE, PTE, and EE. Moreover, to the best of our knowledge, this is the first report on polybacterial infection in EE. Gram-positive bacteria, including Bacillus spp. (n=19), Streptococcus spp. (n=18), Staphylococcus spp. (n=6), Exiguobacterium spp. (n=3), Gemella spp. (n=2), Enterococcus spp. (n=2), a Lysinibacillus sp. (n=1), a Clostridium sp. (n=1), and a Nocardia sp. (n=1), and Gram-negative bacteria, including Serratia spp. (n=18), Pseudomonas spp. (n=10), Enterobacter spp. (n=8), Acinetobacter spp. (n=3), Pantoea spp. (n=3), a Haemophilus sp. (n=1), and a Massilia sp. (n=1), were identified. Interestingly, among them, 10 bacterial species were not previously reported to be associated with endophthalmitis or other ocular infections. Besides, the presence of 4 unidentifiable clones suggests the possibility of novel organisms that might cause eye infections. Therefore, it is recommended that, in addition to the polybacterial nature of POE, PTE, and EE infections, the spectrum of the pathogenic bacterial community identified in this work should be considered while administering antibiotic therapy in suspected endophthalmitis cases.