[Susceptibility of drug-resistant staphylococci isolated from different parts of the ocular anterior segment to common ophthalmic antibiotics]

Objectie To investigate the susceptibility of drug-resistant staphylococci isolated from different parts of the anterior segment to levofloxacin, tobramycin, cefazolin sodium, fusidic acid and clindamycin. Methods: Experimental Study. A total of 67 patients with anterior segment infection (33 cases of conjunctivitis, 6 cases of bacterial keratitis, 7 cases of blepharitis, 9 cases of neonatal dacryocystitis, 9 cases of neonatal dacryocystitis, 1 case of adult dacryocystitis and 11 cases of other infectious eye diseases) were collected from the conjunctival sac, cornea, eyelid margin and lacrimal sac. Minimum inhibitory concentration (MIC) determination of methicillin-resistant Staphylococcus (MRS) strains and β-lactamase-producing (β-Lac) strains by a micro-liquid-based method, according to the M100 standard of the American Institute for Clinical and Laboratory Standardization Susceptibility and resistance determinations were made. Data were statistically analyzed using Chi-square or Fisher's exact test. Results: Thirty-five MRS, 30 β-Lac and 2 β-Lac MRS isolates were identified from 67 multidrug-resistant Staphylococcus . There were 3, 9, 4, and 19 MRS isolates isolated from the lacrimal sac, cornea, eyelid margin and conjunctival sac, accounting for 3/4, 9/12, 4/8, 19/43 (44.2%) of the isolated sites respectively. There were 1, 3, 3, and 23 β-Lac isolates, accounting for 1/4, 3/12, 3/8 and 23/43 (53.5%) of the isolated sites, respectively. The highest proportion of β-Lac isolates isolated from patients with a diagnosis of conjunctivitis was 17 (25.3%) from the conjunctival sac. Among the MRS strains isolated from the cornea and lacrimal sac, 5 (7.5%) and 3 (4.5%) were from patients diagnosed with bacterial keratitis and neonatal tear, respectively. The number of MRS strains and β-Lac isolates isolated from patients with a diagnosis of blepharitis were both 3 (4.5%) from the lid margin.Among the strains isolated from the eyelid margin and the conjunctival sac, drug-resistant Staphylococcus epidermidis was the main strain, the drug-resistant Staphylococcus aureus was the major isolates in lacrimal sac and cornea. Among the 35 MRS isoaltes, 25, 24, 12, 12, and 11 were sensitive to cefazolin sodium, fusidic acid, levofloxacin, clindamycin and tobramycin, and the sensitivity rates were 71.4%, 68.6%, 34.3%, 34.3% and 31.4%, the difference was statistically significant (χ²=22.756, P<0.001), The sensitivity rates of levofloxacin, tobramycin, cefazolin sodium, fusidic acid and clindamycin against MRS isolates from the anterior segment were both statistically significant differences (χ²=18.493, 11.594, 8.906, 9.841, 16.059; all P<0.05). The susceptibility rates of MRS isolates against five antibiotics was statistically significant differences (χ²=33.080, P<0.001). Among the 30 β-Lac isolates, 27, 22, 19, 16, and 8 were sensitive to cefazolin sodium, fusidic acid, levofloxacin, tobramycin and clindamycin, and the sensitivity rates were 90.0 % , 73.3%, 63.3%, 53.3% and 26.7%, the difference was statistically significant (χ²=28.280, P<0.001). The sensitivity rates of five antibiotics against β-Lac isolates from the anterior segment were both statistically significant differences (χ²=50.971, 24.543, 48.147, 44.899, 18.676; all P<0.001). The susceptibility rates of β-Lac isolates against five antibiotics was statistically significant differences (χ²=23.383, P<0.001). The sensitivity of cefazolin sodium and fusidic acid against β-Lac isolates were higher than MRS isolates. Conclusions: Cefazolin sodium and fusidic acid may be the best choice for the treatment of drug-resistant Staphylococcus isolated from anterior conjunctival sac, cornea, eyelid margin and lacrimal sac, especially for β-Lac-producing drug-resistant Staphylococcus infection.

[Comparison study on sensitivity of five ophthalmic antibiotics to common drug-resistant Staphylococci on ocular surface]

Objective: To investigate the in vitro antibacterial sensitivity of levofloxacin, tobramycin, cefazolin sodium, clindamycin and fusidic acid to 67 strains of Staphylococci in ocular surface infection. The purpose of this study is to provide reference for clinical selection of drugs. Methods: Experimental study. Sixth-seven strains of drug-resistant Staphylococci isolated from the Department of Microbiology, Henan Provincial Ophthalmic Hospital during January 2018 and May 2019 were collected. There were 67 strains of Staphylococci including 28 strains of drug-resistant Staphylococcus epidermidi, 17 strains of drug-resistant Staphylococcus aureus, 15 strains of drug-resistant Staphylococcus intermedius and a few other kinds of drug-resistant Staphylococci. The minimum inhibitory concentrations (minimum inhibitory concentration, MIC) of levofloxacin, tobramycin, cefazolin sodium, clindamycin and fusidic acid in 67 strains of drug-resistant Staphylococci were determined by microliquid-based method. The sensitivity was determined according to the American CLSI-M100 standard. The statistical analysis of the data was carried out by using two-dimensional test and Fisher accurate test. Results: Fourteen strains of fusidic acid were sensitive to 17 strains of MRS-Meca-resistant Staphylococcus epidermidis, the difference between fusidic and levofloxacin is statistically significant; 14 strains of cefazolin sodium and 11 strains of fusidic acid were sensitive to 14 strains of β-Lac enzyme-producing Staphylococcus aureus, and there were significant differences between the two drugs and levofloxacin; 6 strains of cefazolin sodium and 5 strains of fusidic acid were sensitive to 10 strains of MRS-Meca-resistant Staphylococcus intermedius, as compared to levofloxacin, there were significant differences between cefazolin sodium and levofloxacin (P=0.011,0.033). Cefazolin sodium was sensitive to 5 strains of MRS-Meca-positive other drug-resistant Staphylococci, which was significantly different from levofloxacin (P=0.048); 54 and 48 strains of cefazolin sodium and fusidic acid were sensitive to 67 strains of drug-resistant Staphylococci, and the sensitive rates were 80.1% and 71.6%, respectively, which were significantly higher than those of levofloxacin, tobramycin and clindamycin. There were significant statistical differences between drug sensitivity (χ²=18.377,9.940；P=0.000,0.003). Conclusions: The sensitivity of cefazolin sodium and fusidic acid to 67 strains of drug-resistant Staphylococci is better than that of levofloxacin, tobramycin and clindamycin, these findings may provide guidance for the clinical treatment of drug-resistant Staphylococci in ocular infection. (Chin J Ophthalmol, 2020, 56: 621-625).

[Topical voriconazole as an effective treatment for fungal keratitis]

OBJECTIVE

To evaluate the efficacy of topical voriconazole in patients with fungal keratitis caused by different fungal species.

METHODS

Interventional case series. Eighty-four patients aged 18 years or older from central China with confirmed fungal keratitis who presented at the outpatient department of Henan Eye Institute were enrolled in the study. The patients underwent in vivo confocal scanning laser microscopy examination, coneal scraping and microscopic examination and fungal culture, and then received topical voriconazole, closed curative effects were conducted. The sensitivity of three different diagnostic techniques, spectrum of the fungi, cure rate for fungal corneal infection related to each species were analyzed.

RESULTS

In our study, 84 patients were diagnosed with fungal keratitis based on clinical symptoms, and results of at least one of the examinations of in vivo confocal scanning laser microscopy, conventional smear, and corneal scraping culture and the sensitivity were 92.85%(78/84), 85.71%(72/84), 84.52%(71/84)respectively. In viro confocal scanning laser microscopy. Successful management was achieved in 83.33% of the patients. Topical voriconazole treatment failed in 14 patients(16.67%), who required surgical treatment. In 36 patients with Fusarium corneal infections, 26(72.22%)were successfully treated with topical voriconazole; however, in 18 patients with Aspergillus corneal infections and 7 patients with Alternaria corneal infections, 94.44% and 100.00% of them were successfully treated, respectively. In a case-based dynamic tracking study, in vivo confocal microscopy provided real-time dynamic detection of surviving hyphae. The existence of hyphae was(38.35±17.32)days for Fusarium,(25.00±16.11)days for Aspergillus,(21.00±4.36)days for Alternaria, and(41.50±31.68)days for the focus in the deep stroma. The duration of treatment was similar for all four groups.

CONCLUSIONS

Topical application of voriconazole is on effective method for the freatment of fungal keratitis Topical voriconazole is highly effective for fungal keratitis caused by Alternaria spp. and Aspergillus, however, for Fusarium, it is relatively low effective. (Chin J Ophthalmol, 2016, 52: 657-662).

Cytoplasmic phase separation in formation of galactosemic cataract in lenses of young rats

We have determined the age dependence of the characteristics of the cytoplasmic phase separation of lenses from normal and galactosemic young rats. In the normal lens, the temperature at which the phase separation occurs decreases monotonically with age. In the lenses of rats fed with a high galactose diet, the phase separation temperature becomes increasingly higher with the development of galactosemia. When the phase separation temperature becomes higher than the ocular temperature, the nuclear opacity appears in vivo. The opacity is the result of light scattering by spatial fluctuations of the refractive index formed by interspersed regions of two separated phases in the fiber cell cytoplasm. This shows that the nuclear opacity that develops in the lens of galactosemic rats is the manifestation of phase separation of the lens fiber cytoplasm.

Direct observation of delta-crystallin accumulation by laser light-scattering spectroscopy in the chicken embryo lens

By using the technique of laser light-scattering spectroscopy, direct observation has been made on the intracellular accumulation of a crystallin protein within the cells of chicken embryo lens during the process of development. Appearance of delta-crystallin has been detected as early as day 4, and its concentration reaches a plateau at day 19. The measurements constitute a noninvasive determination of accumulation of protein molecules that specifically characterize the process of cell differentiation.

Hemoglobin aggregation in single red blood cells of sickle cell anemia

A laser light scattering technique was used to observe the extent of hemoglobin aggregation in solitary red blood cells of sickle cell anemia. Hemoglobin aggregation was confirmed in deoxygenated cells. The light scattering technique can also be applied to cytoplasmic studies of any biological cell.

Phase separation in rat lenses cultured in low glucose media

Experimental evidence that indicates the nuclear opacity that develops in the hypoglycemic cataract in rat lenses is the result of a phase separation of the lens cytoplasm is presented. Phase diagrams of the cytoplasm of organ-cultured lenses were constructed for a series of incubation times in normal and hypoglycemic media. In normal media, the maximum phase separation temperature, Tmax, of the lens cytoplasm decreases with time. In hypoglycemic media, Tmax increases with time and exceeds 37 C after 24 hrs. The increase in Tmax can be stopped and reversed if the lens is returned to normal media within 8 hrs; in good agreement with an earlier biochemical analysis of the kinetics of hypoglycemic cataract formation.

Collapse of Gels in an Electric Field

An infinitesimal change in electric potential across a polyelectrolyte gel produces a discrete, reversible volume change. The volume of the collapsed gel can be several hundred times smaller than that of the swollen gel.

Fusion of phosphatidylserine and mixed phosphatidylserine-phosphatidylcholine vesicles. Dependence on calcium concentration and temperature

Dynamic light scattering has been used to study the temperature dependence of Ca2+-induced fusion of phosphatidylserine vesicles and mixed vesicles containing phosphatidylserine and different phosphatidylcholines. The final vesicle size after Ca2+ and EDTA incubation serves as a measure of the extent of fusion. With phosphatidylserine vesicles, the extent of fusion shows a sharp maximum at an incubation temperature which depends on the Ca2+ concentration between 0.8 and 2 mM. The shift in the fusion peak temperature with Ca2+ concentration is similar to the typical shift in the phase transition temperature with divalent cation concentration in acidic phospholipids. The results suggest a direct correlation between the fusion peak temperature and the phase transition temperature in the presence of Ca2+ prior to fusion. With mixed vesicles containing up to 33% of a phosphatidylcholine in at least 2 mM Ca2+, the extent of fusion as a function of incubation temperature also shows a maximum. The fusion peak temperature is essentially independent of the quantity and type of phosphatidylcholine and the Ca2+ concentration, and identical to that with pure phosphatidylserine in excess Ca2+. The results imply that Ca2+- induced molecular segregation occurs first, and fusion subsequently takes place between pure phosphatidylserine domains.

Temperature dependence of calcium-induced fusion of sonicated phosphatidylserine vesicles

We have measured the temperature dependence calcium-induced fusion of sonicated phosphatidylserine vesicles. The vesicles were incubated in the presence of calcium at a specified temperature until the resulting aggregation or fusion process had gone to completion. EDTA was then added and the resulting final size of the vesicle population was measured by using dynamic light scattering. This final size was plotted against incubation temperature to show the temperature dependence of calcium-induced fusion. This curve has a peak near 11 degrees C which may be associated with the phase transition of the sonicated phosphatidylserine vesicles in the presence of calcium prior to the aggregation or fusion process.

Dynamic light scattering study of calcium-induced fusion in phospholipid vesicles

Acidic sonicated phospholipid vesicles can undergo dramatic morphological changes due to fusion in the presence of divalent metal ions. For example, small spherical phosphatidylserine vesicles can form scroll-like cylinders which precipitate in the presence of Ca2+ above a threshold concentration. Subsequent addition of EDTA will yield large, unilamellar vesicles. These events have previously been established through the combined use of differential scanning calorimetry and freeze-fracture electron microscopy. We have applied the technique of dynamic light scattering to follow these fusion events rapidly, accurately, and non-perturbatively as they occur in solution at calcium concentrations slightly below threshold for precipitation.