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

Pathogenic potential of bacteria isolated from commercial biostimulants

Microbial-based products are a promising alternative to agrochemicals in sustainable agriculture. However, little is known about their impact on human health even if some of them, i.e., Bacillus and Paenibacillus species, have been increasingly implicated in different human diseases. In this study, 18 bacteria were isolated from 2 commercial biostimulants, and they were genotypically and phenotypically characterized to highlight specific virulence properties. Some isolated bacteria were identified as belonging to the genus Bacillus by BLAST and RDP analyses, a genus in-depth studied for plant growth-promoting ability. Moreover, 16S rRNA phylogenetic analysis showed that seven isolates grouped with Bacillus species while two and four clustered, respectively, with Neobacillus and Peribacillus. Unusually, bacterial strains belonging to Franconibacter and Stenotrophomonas were isolated from biostimulants. Although Bacillus species are generally considered nonpathogenic, most of the species have shown to swim, swarm, and produced biofilms, that can be related to bacterial virulence. The evaluation of toxins encoding genes revealed that five isolates had the potential ability to produce the enterotoxin T. In conclusion, the pathogenic potential of microorganisms included in commercial products should be deeply verified, in our opinion. The approach proposed in this study could help in this crucial step.

Post-clear corneal phacoemulsification endophthalmitis: profile and management outcomes at a tertiary eye care center in western India

Background

Infectious endophthalmitis is a serious sight threatening intraocular inflammation that results from exogenous or endogenous spread of organisms into the eye.A retrospective case series to study the profile of endophthalmitis following clear corneal phacoemulsification in western India between years 2008 and 2014 was held in the National Institute of Ophthalmology, Pune, India. Cases of endophthalmitis post-clear corneal phacoemulsification were reviewed pertaining to demography, clinical history, surgeon experience, surgical complications, time of onset following surgery, duration between onset of symptoms and presentation to the center, presenting visual acuity and at follow-ups, slit-lamp examination and ultrasound findings, vitreous tap culture results, treatment, and final functional and anatomical outcomes.

Results

Of 60 cases, 34 were operated in the tertiary center and 26 were referred. The incidence of endophthalmitis post clear corneal phacoemulsification performed at the tertiary center was 0.17%. Mean time delay between onset of symptoms and presentation to the tertiary care center was 2.6 days. Fifty percent cases were culture +ve, of which 80% were Gram +ve and 20% were Gram −ve, no fungal isolates. Coagulase –ve staphylococcus was the most common causative organism; rare isolates included Sphingomonas paucimobilis and Streptococcus mitis. Twenty-six eyes underwent primary vitrectomy. Mean presenting visual acuity was 2.14 ± 0.07 logMAR units which improved to logMAR 0.98 ± 0.12 at final follow-up. Presenting VA was >20/200 in 13.3% and <HM in 60% cases. 66.7% of eyes had visual improvement; 26.7% cases achieved VA 20/40 at final follow-up. Gram +ve and culture –ve cases, better presenting VA, and less time delay between onset and presentation had a favorable visual outcome.

Conclusions

The shift of the clinico-microbiological spectrum of endophthalmitis could be due to change in surgical technique to clear corneal phacoemulsification. Predictors of good visual outcome include good presenting visual acuity, early presentation to the center, culture negativity, and coagulase negative organisms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12348-016-0115-y) contains supplementary material, which is available to authorized users.

Identification and Pathogenic Potential of Clinical Bacillus and Paenibacillus Isolates

The soil-related Bacillus and Paenibacillus species have increasingly been implicated in various human diseases. Nevertheless, their identification still poses problems in the clinical microbiology laboratory and, with the exception of Bacillus anthracis and Bacillus cereus, little is known on their pathogenicity for humans. In this study, we evaluated the use of matrix-assisted laser desorption—ionization time of flight mass spectrometry (MALDI-TOF MS) in the identification of clinical isolates of these genera and conducted genotypic and phenotypic analyses to highlight specific virulence properties. Seventy-five clinical isolates were subjected to biochemical and MALDI-TOF MS identification. 16S rDNA sequencing and supplemental tests were used to solve any discrepancies or failures in the identification results. MALDI-TOF MS significantly outperformed classical biochemical testing for correct species identification and no misidentification was obtained. One third of the collected strains belonged to the B. cereus species, but also Bacillus pumilus and Bacillus subtilis were isolated at high rate. Antimicrobial susceptibility testing showed that all the B. cereus, B. licheniformis, B. simplex, B. mycoides, Paenibacillus glucanolyticus and Paenibacillus lautus isolates are resistant to penicillin. The evaluation of toxin/enzyme secretion, toxin-encoding genes, motility, and biofilm formation revealed that B. cereus displays the highest virulence potential. However, although generally considered nonpathogenic, most of the other species were shown to swim, swarm, produce biofilms, and secrete proteases that can have a role in bacterial virulence. In conclusion, MALDI-TOF MS appears useful for fast and accurate identification of Bacillus and Paenibacillus strains whose virulence properties make them of increasing clinical relevance.