Analytical Study of Conjunctival Bacterial Flora in Diabetic and Non Diabetic Patients
Correspondence Address :
Sandip Samaddar
179,28/C, Santosh Roy Road, Kolkata-700008, West Bengal, India.
E-mail: drsandipSamaddar@gmail.com
Introduction: Conjunctiva is a transparent mucous membrane that lines inside of the eyelids and covers the sclera. It is composed of non keratinised, stratified columnar epithelium with goblet cells. Normal microbial flora constitutes organisms which are present in eyelids and conjunctiva without causing any disease. At birth eyes are sterile but they are later infected by various organisms. Gram positive organisms are mostly prevalent in ocular flora. Diabetes mellitus is a multifactorial disease that can affect all ocular structures.
Aim: To compare the microbial flora between diabetic and non diabetic patients and to study there sensitivity to antibiotics.
Materials and Methods: This was an analytical study conducted on a total of 100 patients attending Department of Opthalmology of Medical College and Hospital, Kolkata, India between June 2019 to July 2019. They were not using any topical ocular preparation. Conjunctival swab was taken from upper fornix of the patients and cultured and the results obtained were analysed using Chi-Square test.
Results: Conjunctival flora of a total of 100 patients, 30 diabetic and 70 non diabetic, were screened. Among the 30 diabetic patients, there were 15 (50%) male and 15 (50%) female. The most common isolated bacteria in diabetic and non diabetic groups were staphylococcus aureus (diabetic 70%, non diabetic 85.7%). There was a statistically significant difference in microbial flora pattern between the diabetic and non diabetic group. There was higher proportion of staphylococcus epidermidis among diabetic patients compared to non diabetic patients (p-value <0.01) and there was a higher proportion of staphylococcus aureus among non diabetics (p-value <0.01).
Conclusion: Present study found statistically significant difference in the microbial flora between diabetics and non diabetics. This will help the clinician to plan for the antibiotic prophylaxis before surgery for patients attending the Out Patient Department (OPD).
Antagonism, Antibiotic sensitivity, Conjunctiva, Eye drops, Oral antibiotics, Virulence
The conjunctiva is a transparent membrane that is present inside the eyelids and covers the sclera. Conjunctiva is composed of non keratinised, stratified squamous epithelium, adenoid layer and fibrous layer. Conjunctival glands include mucin glands like goblet cells and accessory lacrimal glands. The major function of the conjunctiva is to lubricate the eyes by tears and mucus and also act as a barrier against infection (1).
The conjunctiva that is sterile at birth becomes infected with several microbes acquired throughout life. Lactoferrin, lysozyme and Immunoglobulin A (IgA) that are present in tears play an important role in maintaining normal flora (1). Ocular microbial flora also depend on environment, age, immunity, climate, ocular surface disease and general hygiene conditions (2). Staphylococcus sp., Streptococcus sp. and Micrococcus sp. that normally protects against several pathogenic organisms are prevalent in human ocular flora (3). The majority of pathogens causing popstoperative endophthalmitis are from conjunctiva, eye lid and even nasal mucosa (4).
Diabetes mellitus is a multifactorial disease that can affect all ocular surface and even the retina (5). Diabetic endophthalmitis patients have a slightly lower vision than non diabetic endophthalmitis patients and may require vitrectomy more often (6).
This study was aimed to compare the microbial flora between the diabetic and non diabetic patients and know their pattern of sensitivity to antibiotics. Bacterial resistance is one of the most serious problems now-a-days. Knowing the sensitivity pattern of the bacteria will help us to plan our treatment accordingly.
This was an analytical study in which subjects were selected from patients attending OPD at Regional Institute of Ophthalmology (RIO), Kolkata, between June 2019 to July 2019 after consideration of inclusion and exclusion criteria and informed consent from the subjects. Total 100 patients (30 diabetic and 70 non diabetic) who came to RIO OPD with complaints other than eye infections were included. Ethical clearance was obtained for the same from RIO Kolkata.
Inclusion criteria: All patients without any pre existing ocular disease, not using any topical ocular preparation who were attending OPD on every Tuesday during the months of June 2019 and July 2019.
Exclusion criteria: Patient with pre existing ocular disease, patient using any topical ocular preparations and antibiotics, and those undergoing any major ocular surgery were excluded.
Procedure
The samples were collected from upper fornix of eyes by autoclaved swab sticks. The samples were transferred to sterile nutrient agar medium and incubated at 37°C for 3-5 days. Gram staining and Potassium Hydroxide (KOH) mount were then done for the inoculum of each plate.
Gram positive organisms found were staphylococcus sp, streptococcus sp and micrococcus sp. For gram positive cases catalase test and mannitol salt agar test were done.
Gram negative rods found were Escheria coli (E coli) and Klebsiella. They were further tested using phenol red lactose broth tests. Indole, Methyl Red (MR) positive but Voges-Proskauer (VP), citrate negative cases were cultured in Hi Chrome UTI Agar M1353 R. Indole, MR negative but VP, citrate positive cases were cultured in Hi chrome UTI Agar M1418. Mucoid purple colony gives confirmatory evidence of Klebsiella pneumonia.
In the diabetic patients’ eye swab, staphylococcus aureus and Klebsiella pneumonia were not found in same plate. So, to find out any antagonism between the two organisms, two containers of autoclaved nutrient agar were taken at a temperature of 50°C and inoculated with 50 mL broth culture of each organism. Each inoculated medium was taken in a petridish and left to solidify. Each such petridish was inoculated with 50 mL broth culture of second organism. Both plates incubated at 37°C for 24 hours.
Antibiotic sensitivity tests were done on nutrient agar plate by both antibiotic disc diffusion method (Oral antibiotics) and cup plate method (Liquid antibiotics) (7). The zone of diameter was measured in centimeter (cm). The antibiotics used were chloramphenicol, ciprofloxacin, tetracycline, polymyxin-B, rifampicin, co-trimoxazole, cephalexin and bacitracin used as discs. Moxifloxacin, Tobramycin and Gatifloxacin were antibiotic eye drops tested.
Susceptibility of microbes towards various stress conditions like heat, pH and Ultravoilet (UV) exposure were tested. Overnight broth cultures of microbes were incubated in water bath at 50°C for 10, 20 and 30 minutes for heat treatment. For pH treatment the pH of the medium was varied from 5, 8 and 10. For UV treatment microbes were UV exposed for 5, 10 and 15 minutes.
Statistical Analysis
All data were collected in a predesigned data sheet. Chi-square was applied to compare the study parameters between diabetic and non diabetic groups of patients. The result was considered statically significant when p-value was less than 0.05.
Conjunctival flora of a total of 100 patients, 30 diabetic and 70 non diabetic were screened. Among the 30 diabetic patients there were 15 (50%) male and 15 (50%) female patients and their mean age was 53.5 (±20.5) years. The mean duration of diabetes mellitus was 18 (±15) years. The non diabetic or control group included 43 (61%) male patients and 27 (39%) female patients and their mean age was 45 (±28) years. There was no negative culture amongst diabetic patients as compared to 5(7.14 %) among non diabetic patients (p-value=0.56). There was also no significant association between positive culture and duration (<1 year or >1year) of diabetes (p-value=0.30) and age (<55 years or >55 years) of the patient (p-value=0.16).
The microbial isolates are detailed in (Table/Fig 1). The most common isolated bacteria in both diabetic and non diabetic groups was staphylococcus aureus. There was a higher proportion of staphylococcus epidermidis among diabetic patients (43.3%) as compared to non diabetic (14.3%) patients (p-value=0.0031). There was a higher proportion of staphylococcus aureus among non diabetic patients (85.7%) as compared to diabetic patients (70%) (p-value=0.0043).
Antagonism among Microorganisms
In this study, no antagonism was found between the microorganisms Staphylococcus aureus and Klebsiella pneumoniae as shown in (Table/Fig 2).
Antibiotic Sensitivity Test
In this study, Staphylococcus aureus and Staphylococcus epidermidis isolated from the diabetic patients were more resistant than the same isolated from the non diabetic patients. Streptococci sp., Micrococcus roseus, E. coli isolated from the non diabetic patients were more resistant than the same isolated from the diabetic patients (Table/Fig 3), (Table/Fig 4).
Stress Condition Sensitivity Test
The results of stress condition sensitivity test can be represented by arbitrary scale analysis. From this analysis, we can compare the virulence of the microbes isolated from diabetic and non diabetic cases. In this analysis, virulence level in respect to 3 stress conditions (heat, pH and UV exposure) was considered. In this study, Staphylococcus aureus and Staphylococcus epidermidis has higher virulence as compared to Streptococcus sp., Micrococcus sp., E. coli, Klebsiella sp. The results are documented in (Table/Fig 5).
In this study, total 100 patients (30 diabetic and 70 non diabetics) were examined and their conjunctival flora was compared. The present study showed that staphylococcus aureus is the most common isolate in both the diabetic and non diabetic group, as is found by Adam M et al., (8). Ashtamkar S et al., found Staphylococcus epidermidis to be the most common organism (13.2%) isolated from diabetics (9). Study by Venkataraman M et al., showed coagulase negative Staphylococci as the most common organism in diabetics (10). Similar results were found in other studies (11),(12),(13),(14). Rajeshkannan R et al., found that gram negative organisms were more common among diabetics (15) which was opposite with the present study.
This study shows the prevalence of positive culture among diabetic patients that may be due to altered chemotaxis, adherence, phagocytosis, intracellular killing and bactericidal activity found in diabetes (16),(17),(18). Study by Rajeshkannan R et al., showed that diabetics had a positive culture of 68% as compared to non diabetics (15). Another study showed that the microbial growth in diabetic patients was 62.27% compared to 46.67% in non diabetics (19). Similar result was also found in study by Martins EN et al., (14). In the same study, age and gender had no effect on frequency of culture.
It was found that the frequency of gram negative bacteria was four times higher in diabetics with chronic rhinosinusitis than in non diabetic patients (20). In the present study, Klebsiella pneumoniae was most common among gram negative in diabetic patients (23.3%). In study done by Lim HW et al., the percentage was found to be 45.61% (21).
Previously several authors carried out antibiotic sensitivity tests. Long C et al., did antibiotic susceptibility analysis of microbes isolated between different time periods and showed that ciprofloxacin was the most effective against bacterial isolates, followed by cefoperazone during the first decade (1990-1999), but during the second decade (2000-2009) ceftazidime showed the greatest level of activity against most bacterial isolates, followed by cefuroxime. They also showed several gram negative organisms like P aeruginosa, B. proteus and E. coli were multidrug (gentamycin, neomycin, chloromycetin, ofloxacin) resistant (22). Study by Ashtamkar S et al., found Staphylococcus epidermidis was sensitive to gentamycin, vancomycin, linezolid (9).
Rajeshkannan R et al., studied antibiotic resistance to erythromycin, ampicilin, cephalosporin. They found that diabetics were more resistant to all three antibiotics (22.7%) compared to non diabetics (16.6%). Resistance of diabetics to erythromycin and ampicilin is 47.7% compared to non diabetics that is 36.6% (15). In another study, it was found that the gram positive staphylococci sp. has maximum resistance against erythromycin (38%) among the diabetic group and in the non diabetic group maximum resistance was seen with ampicillin (30%). The gram negative bacilli such as pseudomonas showed maximum resistance against ampicillin in both the groups (56%) (1). In the present study, usually topical antibiotics were preferred for ocular application due to its greater local concentration. Also, drops were more preferred over ointments normally as ointments were sticky and may hamper vision just after applying it. Hence, use of eye drops of antibiotics like moxifloxacin can be potential in clinical settings.
Limitation(s)
It was done on a limited number of patients over a short period of time. The study on the susceptibility of the organisms to stress conditions has to be done on a larger scale for better comparison. Authors plan to further continue this study on a larger scale.
The diabetic patients were more prone to ocular infection and hence it can be concluded that they must receive a more stringent antibiotic prophylaxis. Secondly, the study showed that the organism isolated from both the diabetic and the non diabetic patients were more sensitive to moxifloxacin, tobramycin and gatifloxacin. Hence, authors recommend the use of these drugs in antibiotic prophylaxis of patients before planned surgery.
10.7860/JCDR/2020/47457.15150
Date of Submission: Oct 26, 2020
Date of Peer Review: Dec 28, 2020
Date of Acceptance: May 25, 2021
Date of Publishing: Jul 01, 2021
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. NA
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