|Year : 2012 | Volume
| Issue : 3 | Page : 317-322
Microbiological profile of orbital abscess
N Suneetha, MM Teena, V Usha, J Mary
Department of Ophthalmology, St. John's Medical College, Bangalore, Karnataka, India
|Date of Submission||20-Jan-2012|
|Date of Acceptance||26-Apr-2012|
|Date of Web Publication||8-Aug-2012|
M M Teena
Department of Ophthalmology, St. John's Medical College, Bangalore, Karnataka
Background: Knowledge of the culture and sensitivity pattern is necessary, for the institution of appropriate empirical antibiotic therapy in orbital abscess. Objective: The objective of this study is to describe culture and sensitivity patterns of specimens from the orbit and surrounding structures. Materials and Methods: Retrospectively the medical records of 56 cases of orbital abscess were reviewed. Results: Cultures were positive in 38/56 (68.8%) orbital specimens and the organisms included Staphylococcus aureus 18, Streptococci 7, Pseudomonas aeruginosa 3, 2 each of Enterobactersp, Escherichia coli, Proteus mirabilis, Acinetobacter sp. and 1 each of Actinomyces israelii, Diptheroids, Coagulase negative Staphylococcus, Citrobacter freundii, Methicillin-resistant S. aureus and Enterococcus faecalis. Four had polymicrobial infection. Culture of purulent nasal discharge, swabs taken from foci of infection on the face, and blood cultures were done in 26/56, and positive cultures were obtained in 16/26 (61.5%) specimens. In 12 patients, there was a concurrence in the organism cultured from the orbit and from cultures from other sites. Gram-negative organisms were associated with increased ocular morbidity. Conclusion: Gram-positive cocci, especially S. aureus are the most common organisms isolated from orbital abscesses. Infections by Gram-negative organisms were associated with more complications. Empirical intravenous antibiotic therapy should have a broad spectrum of activity effective against a wide range of Staphylococcal organisms and Gram-negative bacilli.
Keywords: Microbiology, orbital abscess, sensitivity patterns
|How to cite this article:|
Suneetha N, Teena M M, Usha V, Mary J. Microbiological profile of orbital abscess. Indian J Med Microbiol 2012;30:317-22
|How to cite this URL:|
Suneetha N, Teena M M, Usha V, Mary J. Microbiological profile of orbital abscess. Indian J Med Microbiol [serial online] 2012 [cited 2013 May 20];30:317-22. Available from: http://www.ijmm.org/text.asp?2012/30/3/317/99494
| ~ Introduction|| |
The potential for serious visual and life-threatening complications in orbital infections necessitates the early institution of appropriate antibiotic therapy.  Knowledge of the microbiological profile of orbital abscess in our population will help in achieving this goal better.  In this retrospective case series, we studied the microbiological profile of orbital abscesses to identify the common causative organisms and the sensitivity patterns. The concurrence of bacterial isolates from the orbit and surrounding structures like the paranasal sinuses and face was studied. The primary antibiotic therapy instituted and the requirement for culture-dependent change in the antibiotic regime was also evaluated.
| ~ Materials and Methods|| |
The records of 56 patients with orbital abscesses were reviewed. All the patients were treated in the department between January 1995 and May 2011. It was a retrospective case review, and the identity of the patients had been delinked from the data. Hence, Institutional Ethical Board clearance was not sought. Data evaluated included primary source of infection, organisms cultured, their sensitivity patterns, empirical antibiotic therapy administered, and the requirement for change of antibiotic regime.
On admission, all patients received empirical intravenous antibiotics. All patients underwent plain and contrast enhanced axial and coronal computerized scans of the orbit, paranasal sinuses, and brain. Following the detection of an orbital abscess, emergency surgical drainage was done. Purulent material, which was obtained from the abscess, was collected on multiple swabs, with strict aseptic precautions, was transferred to the microbiology lab immediately for bacterial cultures (both aerobic and anaerobic) and fungal cultures. Direct microscopy of the samples was done using Grams stain and KOH whenever indicated. The samples were then inoculated onto blood agar, MacConkey agar, and thiogllycolate broth and incubated for 24 h at 37°C. Organisms were further characterized using smears and appropriate biochemical reactions. If there was no growth, the samples were incubated for another 48 h. For fungal culture, Sabourads dextrose agar (SDA) medium without antibiotics, containing peptones, dextrose, and agar was used. The above protocol was used to process samples from other sites also.
Cultures from other sites were done in 26/56 patients and not done in remaining 30 patients, as this is a retrospective data and no set protocol was being followed in management of orbital abscess. Nasal swab cultures were done in 12/26 patients, swabs taken from foci of facial infections were cultured in 9 patients, and blood was cultured in 5 patients.
Descriptive statistics including mean and percentages were calculated. The chi-square test was done to compare visual outcome between patients with Gram-positive infection and Gram-negative infection, with P < 0.05 being considered statistically significant.
| ~ Results|| |
A total of 56 patients treated for orbital abscess were included in the study. The age range was 1 year to 68 years and the M:F ratio was 42:14. Culture positivity was obtained in 38/56 (68.8%) specimens from the orbit and in 16/26 (61.5%) specimens from other sites. The organisms cultured from orbital specimens, organisms cultured from other sites and their culture and sensitivity pattern is detailed in [Table 1]. Staphylococcus aureus in 18 was the most common organism cultured from the orbit. Other organisms cultured included Streptococci 7, Pseudomonas aeruginosa 3, Enterobacter sp. 2, Escherichia More Details coli 2, Proteus mirabilis 2, Acinetobacter sp. 2 and 1 each of Actinomyces israelii, Diptheroids, coagulase negative Staphylococcus, Enterococcus faecalis, Citrobacter freundii and Methicillin-resistant Staphylococcus aureus. Polymicrobial cultures were obtained in four patients [Table 1].
|Table 1: Showing organisms cultured from the orbit and other sites, culture and sensitivity patterns, antibiotics used and visual outcome|
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Of the 26 patients in whom culture was done from other sites, culture positivity was obtained in 16/26 patients. There was a concurrence in the organisms cultured from the orbit and from other sites in 12 patients. The details of the organisms cultured are given in [Table 1]. Culture positivity was obtained in 8/9 facial infections, 7/12 nasal swabs, while only 1/5 showed a positive blood culture.
Acinetobacter infections of the orbit were very virulent; two cases with this infection developed severe visual loss despite early intervention. Of the 11 patients with Gram-negative infection, 7 had best corrected visual acuity of ≤6/60 (severe visual loss).However, only 5 out of 27 patients with Gram-positive infection have best corrected visual acuity of ≤6/60.This difference in visual outcome between Gram-positive and -negative organisms was statistically significant (P = 0.02).
Over the study period, a wide variety of antibiotic combinations have been used as empirical antibiotic therapy. Differences in the preferred antibiotic regime by different departments (ENT, Neurology and Ophthalmology) and between units of the same department and with the study duration being over a large period of time resulted in a wide variety of antibiotics used in the empirical therapy. Most effective antibiotic combination in this study population included (1) third-generation cephalosporin alone or with vancomycin, (2) second-generation cephalosporins and an aminoglycoside, and (3) amoxicillin clavulanate and metronidazole. A culture-dependent change in the antibiotic regime was required in 20/56. The most commonly implicated antibiotic which necessitated change in therapy was ciprofloxacin (6/20) followed by crystalline penicillin (3/20) and more recently amoxicillin clavulanate (2/20) [Table 1].
| ~ Discussion|| |
The nature and virulence of causative organisms influences the outcome of orbital abscesses. Administration of antimicrobial therapy along with surgery is an essential part of the management of orbital abscesses. Moreover, recent trends favor medical management of subperiosteal abscesses. , Hence, the selection of appropriate antibiotic regime is crucial for a successful outcome. Knowledge of culture and sensitivity patterns of specimens from the orbit and surrounding structures would guide the treating ophthalmologist in instituting early and appropriate antibiotic therapy.
Staphylococcus aureus was the most common organism implicated in our patients. This finding is in agreement in most other reports. ,,, Two recent reports have shown the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) in orbital cellulitis. , In both studies, the infections were community acquired. They have not offered explanation for this finding. In our case series, only one MRSA was identified. Unusual organisms cultured in this series included Acinetobacter sp. and Actinomyces israelii.
Infection with Gram-negative organisms was associated with more ocular sequelae than with Gram-positive organisms in this study and Kaban et al. concur with this.  Concurrence in recovered organisms from paired specimens from orbit and other sites have important clinical application in orbital cellulitis. Cultures from suspected sources of infection will help in instituting appropriate antibiotic therapy in the cellulitis stage, preventing progression to abscess formation. Other studies concur with these findings. ,
The culture of a large number of Gram-positive cocci including S. aureus and Streptococci necessitates the use of antibiotics effective against them. Antibiotics with either β lactamase-inhibiting (Amoxicillin + Clavulunate) or penicillinase-resistant properties (Cloxacillin) have to be included in the empirical antibiotic therapy of orbital infections.  Amikacin an aminoglycoside can be added to cover Gram-negative organisms. Third-generation cephalosporins have a wider spectrum of activity being effective against most Gram-positive and Gram-negative organisms and were found to be effective alone or in combination with Vancomycin. In our patients, intravenous fluoroquinolones were not found to be very useful in treating orbital infections and this finds agreement with the findings from other studies.  The shortcomings of this study is the retrospective study design, which resulted in some missing data and lack of uniformity in the management of the patients.
In conclusion, gram positive cocci are the most common organisms in bacterial orbital infections. Infections by Gram-negative organisms were associated with more complications. Empirical antibiotic therapy should include a combination of an antibiotic effective against beta lactamase- and penicillinase-producing gram-positive cocci and an aminoglycoside.
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