Prevalence and antibacterial resistance patterns of extended-spectrum beta-lactamase producing Gram-negative bacteria isolated from ocular infections.

PURPOSE: Extended-spectrum beta-lactamases (ESBLs) mediated resistance is more prevalent worldwide, especially among Gram-negative bacterial isolates, conferring resistance to the expanded spectrum cephalosporins. As limited data were available on the prevalence of ESBLs in this area, the current study was undertaken to determine the prevalence, antibacterial resistance patterns, and molecular detection and characterization of ESBL encoding resistance genes among ocular Gram-negative bacterial isolates from ocular infections. MATERIALS AND METHODS: A prospective study was done on 252 ocular Gram-negative bacterial isolates recovered from ocular infections during a study period from February 2011 to January 2014. All isolates were subjected to detection of ESBLs by cephalosporin/clavulanate combination disc test and their antibacterial resistance pattern was studied. Molecular detection and characterization of ESBL encoding blaTEM -, blaSHV , blaOXA -, and blaCTX-M (phylogenetic groups 1, 2, 9, and 8/25) resistance genes by multiplex polymerase chain reaction and DNA sequence analysis. RESULTS: Of all Gram-negative bacteria, Pseudomonas aeruginosa (44%) was the most common strain, followed by Enterobacter agglomerans and Klebsiella pneumoniae each (10%). Among the 252, 42 (17%) were ESBL producers. The major source of ESBL producers were corneal scraping specimens, highest ESBL production was observed in P. aeruginosa 16 (38%) and Escherichia coli 7 (16.6%). Among ESBL-producing genes, the prevalence of blaTEM -gene was the highest (83%) followed by blaOXA -gene (35%), blaSHV -gene (18.5%), and blaCTX-M-1 -gene (18.5%) alone or together. CONCLUSION: The higher rate of prevalence of ESBLs-encoding genes among ocular Gram-negative bacteria is of great concern, as it causes limitation to therapeutic options. This regional knowledge will help in guiding appropriate antibiotic use which is highly warranted.

Imaging nanoscale features with plasmon-coupled leakage radiation far-field superlenses.

Optical images from nano-scale features were obtained by collection of leakage radiation coupled to surface plasmon polaritons excited by near-field fluorescence. Plasmonic crystals with spatial periods as small as 190 nm and non-periodic features separated by 80 nm, corresponding to ~λ/7, were clearly visible in the real plane images using this far-field technique. We show that the leaked light from the investigated samples carries detailed information to the far-field which is not present in the images obtained with conventional optical microscopy.

Microbiological profile of culture-proven cases of exogenous and endogenous endophthalmitis: a 10-year retrospective study.

PURPOSE: To identify the microbial aetiology of infectious endophthalmitis and to determine the in vitro antibacterial susceptibilities of bacterial isolates. METHODS: A retrospective analysis was carried out of all patients presenting between January 1997 and December 2006 with clinically diagnosed infectious endophthalmitis who underwent microbiological evaluation. Intraocular specimens (aqueous and vitreous fluids) were collected from all cases of clinically suspected infectious endophthalmitis. In addition to intraocular aspirates, blood specimens from endogenous endophthalmitis, and corneal and scleral scrapes from relevant cases were also collected. The collected intraocular specimens, blood specimens, and corneal and scleral scrapes were subjected to microbiological evaluation. RESULTS: Samples from 955 patients with endophthalmitis underwent microbiological analysis, of which 424 (44.4%) were found to be culture positive. Of 424, 364 (85.8%) had bacterial growth and the remaining 60 (14.2%) had fungal growth. Among post-surgical endophthalmitis, Gram-negative bacilli (75%) were found to be the predominant cause for developing fulminant onset, Staphylococcus spp. (68.6%) for acute, and Streptococcus spp. (75%) for chronic onset of infections, whereas in post-traumatic endophthalmitis, Gram-negative bacilli (65.2%) were found to be the predominant cause for fulminant onset, Gram-positive bacillus (28.4%) for acute onset, and fungi (52.3%) for chronic onset of infections. Endophthalmitis associated with microbial keratitis was mainly caused by filamentous fungi (37.2%) and Gram-negative bacilli (37.2%). Overall, gatifloxacin (97.7%) showed highest activity against bacterial isolates followed by ciprofloxacin (95.9%) and ofloxacin (95.1%). CONCLUSION: Gram-negative bacilli cause predominantly fulminant onset, Staphylococci and Gram-positive bacilli acute, and Streptococci, Nocardia, and fungi chronic endophthalmitis. Gatifloxacin demonstrated greatest efficacy against these bacterial isolates.

Epidemiology of bacterial keratitis in a referral centre in south India.

PURPOSE: To study the epidemiological characteristics of bacterial keratitis seen at a tertiary eye care referral centre in south India. METHODS: A retrospective review of medical records of all culture-positive bacterial keratitis which were seen over a 3 years period, from September 1999 through August 2002 was performed. After clinical evaluation corneal scrapings were collected and subjected to culture and microscopy using standard protocols in all patients. RESULTS: Out of 3183 corneal ulcers evaluated, 1043(32.77%) were found to be of bacterial aetiology. A total of 1109 bacterial pathogens were isolated from 1046 eyes with keratitis. The predominant bacterial species isolated was Streptococcus pneumoniae (37.5%). Males were 592(56.76%) and 451(43.24%) were females. There were 564(54.07%) rural residents and 479(45.93%) urban residents; this difference was statistically significant (p< 0.0001). Patients with age more than 50 years (60.2%) were affected significantly more than patients aged less than 50 years (30.8%). While 57.62% of patients were non-agricultural workers, 42.38% were farmers; this difference was statistically significant (p<0.0001). Co-existing ocular diseases predisposing to corneal ulceration were identified in 703(67.4%) patients, compared to other predisposing risk factors in 340(32.6%) patients. One hundred and seventy seven (16.97%) had corneal injury with soil and/or sand, compared to 115(11.03%) patients who had injury due to other materials and the difference was statistically significant. There was lower incidence of bacterial keratitis from June to September. CONCLUSIONS: The epidemiological characteristics of bacterial keratitis vary geographically. This study describing the features of bacterial keratitis would greatly help the practising ophthalmologist and other medical practitioners in the management of their patients.