Ocular Bacterial Isolates Research Articles

334 Metagenomic- and culture-based characterization of the ocular microbiome in cattle with infectious bovine keratoconjunctivitis

Abstract Pinkeye, clinically known as infectious bovine keratoconjunctivitis (IBK), is one of the most highly contagious diseases impacting cattle at all ages. Despite extensive use of antibiotics and vaccines targeting Moraxella bovis, the primary IBK pathogen, the incidence of pinkeye has been increasing in North American beef cow-calf operations. This highlights the incomplete understanding of the pathogenesis of this disease and the need for novel and alternative approaches to control IBK. The objectives of this study were to: 1) characterize the ocular microbiome of beef cattle with and without IBK using shotgun metagenomic sequencing; 2) investigate the genetic diversity of M. bovis, Moraxella bovoculi, and commensal ocular bacterial isolates; 3) evaluate whether selected ocular probiotic candidate strains inhibit Moraxella pathogen growth in the presence of the ocular microbiome in culture using qPCR. A total of 143 ocular swabs were collected from cattle with (n = 102) or without IBK (n = 42) and before antibiotic treatment from beef herds across North Dakota, USA. Fifty samples from IBK (n = 38) and healthy cattle (n = 12) were also subjected to shotgun metagenomic sequencing. Seven bacterial species were relatively more abundant (P < 0.05) in the healthy cattle ocular microbiome including Bifidobacterium globosum, Bacillus licheniformis, Pasteurella multocida, Ruminococcus sp900316555, and Ruminococcus sp900100595. Arthrobacter luteus was the only bacterial species significantly associated with IBK-affected cattle. From the metagenomes, 37 high-quality dereplicated metagenome-assembled genomes (MAGs) were recovered, nearly a third of which were identified as Mesomycoplasma bovoculi (n = 10). M. bovis (n = 5) and M. bovoculi (n = 13) were also isolated from the ocular swabs of both healthy and IBK-affected cattle. These isolates represented 9 M. bovoculi and 5 M. bovis strains (average nucleotide identity < 99.99%). We also isolated and sequenced several potentially beneficial bacterial species from healthy cattle including Bacillus pumilus, Lactiplantibacillus plantarum, Lentilactobacillus buchneri, Levilactobacillus brevis, and Weizmannia coagulans. Four of these probiotic candidates were also tested for their inhibitory effects against M. bovoculi in co-culture with the ocular microbiome after 24 h incubation using qPCR. The B. pumilus, L. buchneri, L. plantarum, and W. coagulans strains, as well as a mixture of all four isolates, significantly reduced the growth of Moraxella. In summary, our results provide important information on the culturable and non-culturable fraction of the bovine ocular microbiome potentially associated with IBK and suggest that certain bacterial species in the eye may inhibit the growth of Moraxella spp.

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience.

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

BACTERIAL CAUSES AND ANTIMICROBIAL SENSITIVITY PATTERN OF EXTERNAL OCULAR INFECTIONS IN SELECTED OPHTHALMOLOGY CLINICS IN SANA’A CITY

Objectives: The aim of the current study was to reveal the bacterial profile and pattern of sensitivity to antibiotics for external ocular infections for patients who attended selected ophthalmology clinics in the city of Sana’a.
 Methods: A cross-sectional study design was used from September 2016 to October 2017 where a total of 197 patients with infection of external eye were included in the study which included conjunctivitis, keratitis, blepharitis and Blepharoconjunctivitis. Samples were collected and transferred to the National Center of Public Laboratories (NCPHL), in Sana'a. Possible bacterial pathogens have been isolated and identified using regular laboratory techniques, and microbial sensitivity testing has been carried out using a disc diffusion method.
 Results: A total of 197 ocular samples were obtained for microbiological evaluation, of these 146 (74.1%) have bacterial growth. Bacteria of Gram positive accounted for 52.1% and the prevalent isolation was S. aureus (30.1%). Gram negative bacteria made up 47.9% and the predominant isolation was Pseudomonas aeruginosa (26.7%). The majority of Gram-positive bacteria were sensitive to ciprofloxacin (90% - 100%), vancomycin (86% - 100%) and Gram-negative isolates sensitive for amikacin (100%) and ciprofloxacin (63% - 100%).
 Conclusion: These results revealed that Gram-positive bacteria were the generally common bacteria isolated from infections of external eye and were more susceptible to vancomycin and ciprofloxacin while Gram-negative isolates were more susceptible to ciprofloxacin and amikacin. The high rate of resistance for most antibiotics in Yemen, leaves ophthalmologists with very few options of drugs to treat eye infections. Large-scale ongoing studies in the future should also be conducted in order to monitor the antimicrobial resistance of the external ocular bacterial isolates.
 Peer Review History: 
 Received 20 May 2020; Revised 25 June; Accepted 4 July, Available online 15 July 2020 
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 EPIDEMIOLOGY, BACTERIAL PROFILE, AND ANTIBIOTIC SENSITIVITY OF LOWER RESPIRATORY TRACT INFECTIONS IN SANA’A AND DHAMAR CITY, YEMEN

In Vitro Antimicrobial Activity of a New Ophthalmic Solution Containing Hexamidine Diisethionate 0.05% (Keratosept).

To assess the in vitro antimicrobial activity of a new commercial ophthalmic solution containing hexamidine diisethionate 0.05% (Keratosept). Staphylococcus aureus American Type Culture Collection (ATCC 43300), Pseudomonas aeruginosa ATCC 27853, 3 ocular bacterial isolates (1 Staphylococcus epidermidis, 1 S. aureus, and 1 P. aeruginosa), and 5 Candida species were used. The bacterial and fungal isolates were cultured on Columbia blood agar base and Sabouraud-dextrose agar plates, respectively, and incubated overnight at 37°C. Suspensions were prepared in a sterile saline solution with optical density equal to 0.5 McFarland standard (∼10 CFU/mL). Isolate suspensions were made in Keratosept solution to obtain a concentration of 10 CFU/mL. The suspensions were then distributed in conical tubes with a final volume of 1 mL and incubated at 37°C. After 1, 5, 10, 15, 20, 25, 30 minutes, and 24 hours, 10 μL of each suspension was removed, seeded on Columbia blood agar base and Sabouraud-dextrose agar plates and then incubated for 24 hours at 37°C. After 1-minute incubation, there was no growth on the plates seeded with S. aureus ATCC 43300, S. aureus clinical isolate, S. epidermidis clinical isolate, and all 5 Candida species tested. Conversely, Keratosept solution failed to kill the Pseudomonas isolates after 30 minutes exposure and needed 24 hours to eradicate the organisms. Keratosept ophthalmic solution showed in vitro antimicrobial activity against S. epidermidis, S. aureus, and Candida species. Results suggest that it may be a potential candidate for the treatment of staphylococcal and Candida infections of the ocular surface and have some role in antimicrobial prophylaxis before intravitreal injections.

In vitro antimicrobial activity of a new ophthalmic solution containing povidone-iodine 0.6% (IODIM® ).

To assess the in vitro antimicrobial activity of a new commercial ophthalmic solution containing povidone-iodine 0.6% (IODIM® ). Staphylococcus aureus ATCC 43300, Pseudomonas aeruginosa ATCC 27853, three ocular bacterial isolates (1 S.epidermidis, 1 S.aureus, 1 P.aeruginosa) and five Candida species were used. The bacterial and fungal isolates were cultured on Columbia blood agar base plates and Sabouraud-dextrose agar plates, respectively and incubated overnight at 37°C. Bacterial and fungal suspensions in sterile saline solution were prepared to an optical density equal to 0.5 McFarland standard (approximately 108 CFU/ml). Suspensions of the isolates were made in IODIM® solution to obtain a final concentration of 106 CFU/ml. The suspensions were then distributed in conical tubes in a final volume of 1ml and incubated at 37°C. At different time-points (1, 5, 10, 15, 20, 25, 30min and 24hr), 10μl of each suspension was removed, seeded on Columbia blood agar base and Sabouraud-dextrose agar plates and then incubated for 24hr at 37°C. Positive and negative controls were included in all experiments. After 5-min incubation, there was no bacterial growth on any plate. Conversely, IODIM® failed to kill the Candida isolates after 30min' exposure and needed 24hr to eradicate the organisms. IODIM® ophthalmic solution showed in vitro antimicrobial activity against S.epidermidis, S.aureus, P.aeruginosa and Candida species. Results suggest that it may be a potential candidate for the treatment of ocular surface infections and antimicrobial prophylaxis before intravitreal injections.

Biocidal Efficacy of a Hydrogen Peroxide Lens Care Solution Incorporating a Novel Wetting Agent.

To compare the antimicrobial effects of CLEAR CARE, a 3% hydrogen peroxide (H2O2) solution formulated for simultaneous cleaning, daily protein removal, disinfection, and storage of soft (hydrophilic) hydrogel, silicone hydrogel, and gas-permeable contact lenses, and CLEAR CARE PLUS, consisting of the 3% H2O2 solution plus a novel wetting agent, polyoxyethylene-polyoxybutylene (EOBO-21). Three lots each of the 2 solutions were incubated with 5 compendial microorganisms required by the Food and Drug Administration (FDA) 510(k) and International Organization for Standardization (ISO) 14729 stand-alone procedures, 4 clinical isolates of Gram-positive and Gram-negative bacteria, and trophozoites and cysts of 2 Acanthamoeba strains that are associated with microbial keratitis. Microbial loads were evaluated after disinfection and neutralization. Both solutions exceeded the FDA/ISO stand-alone primary criteria against Gram-positive and Gram-negative compendial bacteria, yeast, and mold after only 1.5-hr disinfection/neutralization. At the recommended minimum disinfection time, bacteria were reduced by 4.4 to 5.1 logs, yeast by 4.4 to 4.9 logs, and mold by 2.9 to 3.5 logs with and without organic soil. In addition, both solutions eliminated or effectively reduced populations of clinically relevant ocular bacterial isolates (4.5-5.0 logs), Acanthamoeba trophozoites (3.4-4.2 logs), and cysts (1.5-2.1 logs). Both solutions eliminated or reduced populations of FDA/ISO compendial bacteria and fungi as well as clinically relevant microorganisms and Acanthamoeba trophozoites and cysts. The addition of EOBO-21 to the 3% H2O2 lens care solution had no impact on antimicrobial activity.

In Vitro Evaluation of a Hypochlorous Acid Hygiene Solution on Established Biofilms.

The purpose of this study was to determine whether a commercial formulation of hypochlorous acid hygiene solution (0.01%), Avenova, can destroy existing biofilms formed by ocular clinical bacterial isolates, including blepharitis isolates of Staphylococcus aureus and coagulase-negative staphylococci, and a keratitis isolate of Pseudomonas aeruginosa. Biofilms grown in bacterial growth media on disposable contact lens cases were challenged with hypochlorous acid hygiene solution. At various time points, surviving bacteria were quantified by serial dilution and colony counts. Staphylococcus aureus biofilms formed on glass were challenged using a hypochlorous acid hygiene solution and imaged using vital staining and confocal laser scanning microscopy. Bactericidal activity (≥3 Log10; 99.9%) was observed for all tested bacterial species after a 30-min exposure. Staphylococcus aureus biofilms had a bactericidal level of killing by 10 min (P<0.01), Staphylococcus capitis by 5 min (P<0.001), Staphylococcus epidermidis by 30 min (P<0.001), and P. aeruginosa by 10 min (P<0.01). Confocal microscopy and crystal violet staining analysis of bacterial biofilms treated with hypochlorous acid solution both demonstrated that biofilm bacteria were readily killed, but biofilm structure was largely maintained. Hypochlorous acid (0.01%) hygiene solution was able to achieve bactericidal levels of killing of bacteria in biofilms but did not disrupt biofilm structures. Susceptibility of tested staphylococcal blepharitis isolates varied by species, with S. capitis being the most susceptible and S. epidermidis being the least susceptible.

Bacteria induce autophagy in a human ocular surface cell line

Autophagy protects cells from intracellular pathogens, but can be exploited by some infectious agents to their benefit. Currently it is not known if bacteria induce autohpagy in cells of the cornea. The goal of this study was to develop an ocular surface autophagy reporter cell line and determine whether ocular bacterial pathogens influence host responses through autophagy induction. The cell line was made using lentivirus transduction of an LC3-GFP fusion protein in human corneal limbal epithelial (HCLE) cells. LC3-GFP puncta in HCLEs were induced by rapamycin and ammonium chloride treatments, and prevented by the autophagy inhibitors 3-methyladenine (3′MA) and bafilomycin. Importantly, secretomes from Escherichia coli, Serratia marcescens, Staphylococcus aureus, methicillin sensitive (MSSA) and resistant (MRSA), were found to induce autophagy, whereas other bacteria, including Acinetobacter baumannii, Achromobacter xylosoxidans, Enterococcus faecalis, Klebsiella pneumoniae, Moraxella sp., and Stenotrophomonas maltophilia, did not. Our data indicates differences between tested ocular isolates of MRSA and MSSA in the activation of autophagy. HCLEs treated with 3′MA were slightly more susceptible to cytotoxic factors produced by S. marcescens and MRSA keratitis isolates, by contrast, bafilomycin A1 treatment caused no difference. This work demonstrates the successful development and validation of an autophagy reporter corneal cell line and indicates differences between ocular bacterial isolates in the activation of autophagy.

Glycerol Monolaurate Inhibits Lipase Production by Clinical Ocular Isolates Without Affecting Bacterial Cell Viability

We sought to determine the relative lipase production of a range of ocular bacterial isolates and to assess the efficacy of glycerol monolaurate (GML) in inhibiting this lipase production in high lipase-producing bacteria without affecting bacterial cell growth. Staphylococcus aureus,Staphylococcus epidermidis,Propionibacterium acnes, and Corynebacterium spp. were inoculated at a density of 10(6)/mL in varying concentrations of GML up to 25 μg/mL for 24 hours at 37 °C with constant shaking. Bacterial suspensions were centrifuged, bacterial cell density was determined, and production of bacterial lipase was quantified using a commercial lipase assay kit. Staphylococcus spp. produced high levels of lipase activity compared with P. acnes and Corynebacterium spp. GML inhibited lipase production by Staphylococcal spp. in a dose-dependent manner, with S. epidermidis lipase production consistently more sensitive to GML than S. aureus. Glycerol monolaurate showed significant (P < 0.05) lipase inhibition above concentrations of 15 μg/mL in S. aureus and was not cytotoxic up to 25 μg/mL. For S. epidermidis, GML showed significant (P < 0.05) lipase inhibition above 7.5 μg/mL. Lipase activity varied between species and between strains. Staphylococcal spp. produced higher lipase activity compared with P. acnes and Corynebacterium spp. Glycerol monolaurate inhibited lipase production by S. aureus and S. epidermidis at concentrations that did not adversely affect bacterial cell growth. GML can be used to inhibit ocular bacterial lipase production without proving detrimental to commensal bacteria viability.

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.

External ocular surface bacterial isolates and their antimicrobial susceptibility patterns among pre-operative cataract patients at Mulago National Hospital in Kampala, Uganda

BackgroundEndophthalmitis is a severe complication of cataract surgery which leads to high ocular morbidity and visual loss even with antibiotic treatment. Bacterial ocular floras are the implicated causative agents. This study was undertaken to evaluate the external ocular surface bacterial isolates and their antimicrobial susceptibility patterns among pre-operative cataract patients at Mulago National Hospital.MethodsThis cross sectional study enrolled consecutively 131 patients scheduled for routine cataract surgery in the Department of Ophthalmology at Mulago National Hospital in Kampala, Uganda. Eyelid margin and conjunctival swabs were collected and processed using standard microbiological procedures to identify bacterial isolates and their respective antimicrobial susceptibility patterns.ResultsOf 131 patients involved (mean age 63.3 ± 14.5 years), 54.2% (71/131) were females. The eyelid margin and conjunctival samples were culture positive in 59.5% (78/138) and 45.8% (60/138) respectively. The most common organisms identified were Coagulase-negative Staphylococci (CoNS) [65.9% (91/138)] and Staphylococcus aureus [21.0% (29/138)]. CoNS showed the highest resistance to tetracycline (58.2%, 53/91) and erythromycin (38.5%, 35/91), whereas in S. aureus the resistance to tetracycline and erythromycin were 55.2% (16/29) and 31.0% (9/29) respectively. Methicillin resistant CoNS (MRS) and Methicillin resistance S. aureus (MRSA) were 31.9% (29/91) and 27.6% (8/29) respectively. There were low resistance rates for CoNS, S. aureus and other bacterial isolates to ciprofloxacin (11.1%-24.2%), gentamicin (5.6-31.0%), tobramycin (17.2% -25.3%) and vancomycin (0.0%).ConclusionCoNS and S. aureus are the most common bacterial isolates found on the external ocular surface of the pre-operative cataract patients. Ciprofloxacin, gentamicin, tobramycin and vancomycin showed the lowest resistance rates to all bacterial isolates, therefore may be used to reduce bacteria load in the conjunctiva sac among cataract patients prior to surgery.

Evaluation of the new OxyPlate™ Anaerobic System for the isolation of ocular anaerobic bacteria.

Anaerobic bacteria can cause ocular infections. We tested the OxyPlate™ Anaerobic System (OXY) to isolate pertinent anaerobic bacteria that can cause ocular disease. OXY, which does not require direct anaerobic conditions (i.e. bags, jars), was compared to conventional isolation of incubating culture media in anaerobic bags. Standard colonies counts were performed on anaerobic ocular bacterial isolates under aerobic and anaerobic conditions (anaerobic bags) using agar media: 1) OXY (aerobic only), 2) 5% sheep blood (SB), 3) Chocolate, and 4) Schaedler. The bacteria tested were de-identified ocular isolates cultured from endophthalmitis and dacryocystitis that include 10 Propionibacterium acnes and 3 Actinomyces species. The colony counts for each bacteria isolate, on each culturing condition, were ranked from largest to smallest, and non-parametrically compared to determine the best culturing condition. All anaerobic conditions were positive for all of the anaerobic isolates. SB and Schaedler's agar under aerobic conditions did not support the growth of anaerobic bacteria. Sparse growth was noted on chocolate agar with Propionibacterium acnes. As an anaerobic system, SB in an anaerobic bag isolated higher colony counts than OXY (P=0.0028) and chocolate agar (P=0.0028). Although OXY did not test to be more efficient than other anaerobic systems, it appears to be a reasonable alternative for isolating anaerobic bacteria from ocular sites. The use of an agar medium in a specially designed plate, without the requirement of an anaerobic bag, rendered OXY as an advantage over other anaerobic systems.

Screening of OcularEnterobacteriaceaeIsolates for Presence of ChromosomalblaNDM-1and ESBL Genes: A 2-Year Study at a Tertiary Eye Care Center

Since, to our knowledge, there are no reports on the prevalence of the blaNDM-1 gene among ocular isolates of Enterobacteriaceae, and only limited information on the prevalence of extended spectrum beta-lactamases (ESBLs) among ocular bacterial isolates are available, our study was undertaken. A prospective study was done on 74 Enterobacteriaceae isolates from patients presenting with clinical suspicion of bacterial ocular infections during a period from January 2010-December 2011. All isolates were subjected to detection of ESBLs by double disc synergy and screened for the presence of CTX-M -I, II, III, and IV groups, and OXA, TEM, SHV, blaNDM-1 genes by PCR. Of 74 ocular Enterobacteriaceae isolates 57 (77%) were ESBL producers tested by the double disc diffusion test. PCR-based DNA sequencing of these 57 ocular isolates showed the presence of CTX-M-15 (14.0%), blaOXA-1 (5.2%), blaSHV-1 (8.7%), and blaTEM-1 (7.0%) types. The blaNDM-1 was absent among these ocular isolates. The most widely disseminated ESBL gene among ocular isolates was CTX-M-15. Phenotypic and genotypic results showed 100% correlation. To our knowledge, this is the first extensive study performed to genotype ESBL-producing ocular Enterobacteriaceae isolates. The isolation of ESBL-producing Enterobacteriaceae organisms predominantly from conjunctival specimens indicates community-acquired infections/colonization by these bacteria in the conjunctiva of the patients, and cases are not related to hospital-acquired infections because of the short stay of ophthalmic patients in the hospitals. A shift in the resistance rates of ceftazidime from 37.5% to 79.7% over the years proves the increase in drug resistance among ocular clinical isolates.

In-Vitro efficacy of antimicrobial agents used in the treatment of bacterial eye infections in Ibadan, Nigeria

Failure to cure eye infections, and reduced potency in topical antimicrobials had been observed in South Western Nigeria, this study sought to evaluate in vitro, the efficacy of antimicrobial agents in the treatment of ocular infections. A total of 46 ocular bacterial isolates were recovered from the diagnostic laboratory of the University College Hospital, Ibadan, from conjunctival swabs of patients having underlying eye diseases (Cataracts, glaucoma and esotrapia), and from patients presenting with other symptoms of eye infections. The pathogens incriminated were Staphylococcus aureus (73.5%), Coagulase negative Staphylococci (13.3%), Klebsiella species (10.3%), and Pseudomonas aeruginosa (2.0%). Disc diffusion tests (Bauer-Kirby method) were carried out using ciprofloxacin, gentamicin, chloramphenicol, erythromycin, augmentin, cefuroxime and levofloxacin. Broth dilution techniques were thereafter performed using gentamicin, chloramphenicol and ciprofloxacin. The microlide- erythromycin was 63.0% efficacious, augmentin and cefuroxime showed 71.1% and 76% efficacy. Minimum inhibitory concentrations (MIC) of commonly used topical antibiotics however showed different levels of resistance. Resistance to the aminoglycosides was marked, yielding 53.4% with MIC50= 8, MIC90 > 256, Resistance to chloramphenicol was even more marked 69.6% with MIC50= 16, MIC90= 64, the fluoroquinolones showed high efficacy- levofloxacin and ciprofloxacin showed 93.4% and 82.6% susceptibility respectively with MIC50 < 0.5, though slightly demonstrable resistance was observed (MIC90= 8). The study thus recommends the discontinuation of empirical therapy by physicians in order to stem the tide of resistance; it justifies the inclusion of the fluoroquinolones in susceptibility testing of ocular bacterial isolates, and its first line of choice if cure is warranted.doi: 10.4314/ajcem.v12i3.7

Normal conjunctival flora in healthy infants aged from 1 to 4 months

To investigate the normal conjunctival bacterial flora isolated from healthy infants aged from 1 to 4 months and to analyze its correlated factors. This was a cross-sectional study. From January to March 2009, 109 cases of healthy babies aged from 1 to 4 months were selected through simple random sampling when they accepted health examination provided by Tianjin Medical University Eye Center and Tianjin Women and Children's Health Center. Conjunctival swabs were taken from both eyes and inoculated onto blood agar plates. The isolated bacteria were classified professionally. The distribution of different bacteria was investigated as well as the possible correlated factors by using t-test, χ(2) test and binary logistic regression of SPSS 11.5. 26 cases of healthy babies (23.9%) got positive culture results which consisted 44 strains of ocular bacterial isolates. 25 strains were gram-positive cocci, while 18 strains gram-positive bacilli, and 1 strain gram-negative bacillus. The first three isolated bacteria were Diphthamide bacillus (17/44, 38.6%), Staphylococcus epidermidis (16/44, 36.4%), and Staphylococcus aureus (6/44, 13.6%). The two subtypes of Staphylococci coexisted with Diphthamide bacillus in 8 eyes of 36 eyes from which bacteria were isolated. The bacterial isolation rate through every month age group had no significant difference (χ(2) = 0.351, P > 0.05). There was no significant difference in the group of positive isolation (26 cases, 36 eyes) or negative isolation (83 cases, 166 eyes) through breast, formula or mixed feeding (χ(2) = 1.182, P > 0.05). The gender had no influence on the detection of bacteria (χ(2) = 0.001, P > 0.05). The birth weight, gestational age or examined age between the two groups had no significant difference (t = 0.078, t = 0.940, t = 0.686, P > 0.05). The gender, age, birth weight, gestational age and the way of feeding had no correlation with existence of conjunctival flora in these healthy infants (Wald χ(2) = 0.001, Wald χ(2) = 0.003, Wald χ(2) = 0.117, Wald χ(2) = 1.307, Wald χ(2) = 1.490, P > 0.05). The normal conjunctival flora might establish during the initial months of little babies. Staphylococcus epidermidis and Diphthamide bacillus are the most common bacteria. Future studies should be conducted to make sure whether there would be some factors correlated with the culture results.

Etiology and antibacterial susceptibility pattern of community-acquired bacterial ocular infections in a tertiary eye care hospital in south India.

Aims:To identify the etiology, incidence and prevalence of ocular bacterial infections, and to assess the in vitro susceptibility of these ocular bacterial isolates to commonly used antibiotics.Materials and Methods:Retrospective analysis of consecutive samples submitted for microbiological evaluation from patients who were clinically diagnosed with ocular infections and were treated at a tertiary eye care referral center in South India between January 2002 and December 2007.Results:A total of 4417 ocular samples was submitted for microbiological evaluation, of which 2599 (58.8%) had bacterial growth, 456 (10.3%) had fungal growth, 15 (0.34%) had acanthamoebic growth, 14 (0.32%) had mixed microbial growth and the remaining 1333 (30.2%) had negative growth. The rate of culture-positivity was found to be 88% (P < 0.001) in eyelids’ infection, 70% in conjunctival, 69% in lacrimal apparatus, 67.4% in corneal, 51.6% in intraocular tissues, 42.9% in orbital and 39.2% in scleral infections. The most common bacterial species isolated were Staphylococcus aureus (26.69%) followed by Streptococcus pneumoniae (22.14%). Sta. aureus was more prevalent more in eyelid infections (51.22%; P = 0.001) coagulase-negative staphylococci in endophthalmitis (53.1%; P = 0.001), Str. pneumoniae in lacrimal apparatus and corneal infections (64.19%; P = 0.001), Corynebacterium species in blepharitis and conjunctivitis (71%; P = 0.001), Pseudomonas aeruginosa in keratitis and dacryocystitis (66.5%; P = 0.001), Haemophilus species in dacryocystitis and conjunctivitis (66.7%; P = 0.001), Moraxella lacunata in blepharitis (54.17%; P = 0.001) and Moraxella catarrhalis in dacryocystitis (63.83%; P = 0.001). The largest number of gram-positive isolates was susceptible to moxifloxacin (98.7%) and vancomycin (97.9%), and gram-negative isolates to amikacin (93.5%) and gatifloxacin (92.7%).Conclusions:Gram-positive cocci were the most frequent bacteria isolated from ocular infections and were sensitive to moxifloxacin and vancomycin, while gram-negative isolates were more sensitive to amikacin and gatifloxacin.

Analysis on the susceptibility of fusidic acid for common gram positive bacteria

To assess in vitro susceptibility of the fusidic acid, vancomycin, tobramycin and ofloxacin for 8 kinds of ocular gram-positive bacteria. It was an experimental study. One hundred strains of ocular gram-positive bacterial isolates selected from Beijing Institute of Ophthalmology, cultivated and identified by the routine, were tested for their susceptibilities to fusidic acid, vancomycin, tobramycin and ofloxacin, with in vitro by the Kirby-Bauer disk diffusion method. Significant differences between groups were evaluated by SPSS 11.5 chi-square test of four-fold table. In the study, the percentage of susceptibility for in vitro gram-positive bacterial isolates to tobramycin, ofloxacin, vancomycin and fusidic acid was 55.0%, 65.0%, 98.0% and 53.0%. The susceptibility to vancomycin was significantly higher than to tobramycin, ofloxacin and fusidic acid (chi(2) = 51.425, 36.113, 54.737; P < 0.05). The susceptibility of common staphylococci to fusidic acid (85.5%) was just lower than to vancomycin (100.0%) (chi(2) = 6.605, P < 0.05), but was significantly higher than to tobramycin (58.2%) and ofloxacin (54.5%) (chi(2) = 10.106, 12.511; P < 0.05). The susceptibility of common streptococcus to fusidic acid (0.0%) was lower than to vancomycin (100.0%) and ofloxacin (85.0%) (chi(2) = 40.000, 29.565; P < 0.05), but the susceptibility to fusidic acid and tobramycin (15.0%) were equivalent (chi(2) = 1.441, P > 0.05). The gram-positive bacilli and nocardia showed significantly lower susceptibility to fusidic acid (24.0%) than that to the other three antibiotics (tobramycin 80.0%, ofloxacin 72.0%, vancomycin 92.0%) (chi(2) = 23.727, 22.430, 11.538; P < 0.05). The in vitro susceptibility of fusidic acid to staphylococci is higher, while to streptococcus and gram-positive bacilli is obviously lower than other three kinds of antibiotics.

Analysis on susceptibility of ocular bacterial pathogens to four kinds of fluoroquinolone

To assess the in vitro susceptibilities of ocular bacterial isolates to Gatifloxacin and other fluoroquinolones which are often used in ophthalmic treatment. Non-randomized, non-comparative, retrospective study. Ocular bacterial isolates (n = 619) from Beijing Institute of Ophthalmology were tested for their susceptibilities to gatifloxacin, ciprofloxacin, ofloxacin and levofloxacin in vitro by the Kirby-Bauer disk diffusion method. The total number of ocular bacterial isolates was 619 from January, 2005 to December, 2006 including gram-positive cocci 372(60.1%), gram-negative cocci 7 (1.1%), gram-positive bacilli 60 (9.7%), gram-negative bacilli 177 (28.6%), other 3 (0.5%). The percentage of susceptibility in total ocular bacterial isolates to gatifloxacin, ciprofloxacin, ofloxacin and levofloxacin was 88.4%, 72.1%, 64.8% and 54.4%. The susceptibility of Staphylococcus species to gatifloxacin (89.9%) was significantly higher than ciprofloxacin (38.8%), ofloxacin (48.2%) and levofloxacin (61.6%). Streptococcus species showed significantly higher susceptibility to gatifloxacin (93.2%), levofloxacin (89.2%) and ofloxacin (87.8%) than ciprofloxacin (62.2%). The susceptibility of gram-positive bacilli to gatifloxacin (86.7%) was significantly higher than ciprofloxacin (58.3%); All above differences are significant (P < 0.0083). Gram-negative cocci, enteric bacilli family and Pseudomonas species have the equivalent susceptibility to gatifloxacin, ciprofloxacin, ofloxacin and levofloxacin (P > 0.05). Most of ocular bacterial are susceptible to gatifloxacin in vitro, especially gram-positive bacteria including Staphylococcus species, Streptococcus species and gram-positive bacilli.

Antibacterial Effects of Garcinia Kolanut Extracts on Ocular Bacterial Isolates in Lagos

The is a prospective study of six month duration, March 1995 to August 1995. The aim of the study is to evaluate the antibacterial activities of the extracts of Garcinia kola nuts on common bacteria isolated from ocular discharges of eye clinic patients, in the Guinness Eye Centre, Lagos University Teaching Hospital. Following some study on laboratory animals at the College of Medicine University of Lagos using water extracts of the nuts to show anti-glaucomatous activities as claimed by an octogenarian, another probable antibacterial activity of the same extract was highlighted after accidental instillation of the same improved redness of the eyes. Common ocular bacterial micro-organisms were isolated from wet conjunctival swabs obtained from 95 clinic consecutive patients with purulent ocular discharges, at the Guinness Eye Centre of the – LUTH. Study was non-invasive. Swabs were sent to the micro-biologist for microscopy, culture and sensitivity assay patients were treated with orthodox antibiotics according to sensitivity results. The inhibitions of the isolated organisms by the extracts of Garcinia kola nuts were observed, measured and recorded. Two methods of extractions were used. The first extraction is distilled water compared effects with those in methanol extract. The second in distilled water compared with effects of a known broad spectrum antibiotic, ciprofloxacin (ciproxin). The water extract had strong inhibitory activities on Escherchia coli, Enterococcus faecalis, proteus mirabilis. There was a better statistical difference p>0.5%. The methanol extract only inhibited staphylococcus aureus and pseudomonas aeruginosa better. Both extracts inhibited staphylococcus albus equally. When the effects of the 5% of the water extract was compare with that of 0.05% ciprofloxacin there was no statistical difference p

In Vitro Activity of Fluoroquinolones Against Ocular Bacterial Isolates in São Paulo, Brazil

To compare the in vitro susceptibility profiles of bacterial ocular isolates and to determine minimum inhibitory concentrations (MICs) of gatifloxacin and moxifloxacin (fourth-generation fluoroquinolones) versus ciprofloxacin and ofloxacin (second-generation fluoroquinolones). Gram-positive and gram-negative isolates were recovered from cases of keratitis, conjunctivitis, and endophthalmitis between 2002 and 2004 and were identified and extracted from the Microbiology Data Bank of the Federal University of São Paulo, São Paulo, Brazil. The comparison of in vitro MIC and susceptibility profiles for ofloxacin, ciprofloxacin, gatifloxacin, and moxifloxacin in gram-positive and gram-negative (n = 219) isolates was performed using the E test method. The fourth-generation fluoroquinolones were statistically more potent than the second generations for gram-positive bacteria. The MIC90 level was lower for moxifloxacin than that for gatifloxacin against Staphylococcus aureus, methicillin-susceptible coagulase-negative Staphylococcus (CoNS), and S. pneumoniae, whereas the levels were equal against S. viridans and the gatifloxacin MIC90 was lower in methicillin-resistant CoNS. There was no statistically significant difference between moxifloxacin and gatifloxacin when the permutation method from the MULTTEST procedure (SAS proc multtest) was used to obtain the adjusted P value. MIC90 for ciprofloxacin was lower in gram-negative bacteria. MIC90 for ofloxacin was higher against Haemophilus spp. and Moraxella spp. Ciprofloxacin was the most statistically potent fluoroquinolone for Pseudomonas spp. Ciprofloxacin was statistically just as potent as gatifloxacin for the other gram-negative isolates. From susceptibility profiles achieved with in vitro testing, the fourth-generation fluoroquinolones may offer some advantages over the currently available fluoroquinolones; however, a combination of the pharmacodynamics and pharmacokinetics of the drug, infection site, and the MIC is needed to predict the in vivo efficacy and best clinical applicability.