Key Words: Antibiotic Sensitivity, Culture, Dubai

Over the past decade, antimicrobial resistance has emerged in all kinds of micro-organisms worldwide and Dubai is no exception. This is primarily due to the increase in antibiotic abuse.1 Early detection of emerging trends in antimicrobial resistance may facilitate implementation of effective control measures.

Dubai has a large expatriate population. Since it is the economic hub of the region, a large number of people travel in and out of Dubai. This may facilitate the importation of various micro-organisms to the region.

The laboratory testing of antibiotic susceptibility contributes directly to patient care and the expertise of the microbiology laboratory can have powerful influence on antibiotic usage. We present the data collected over a period of 17 months in a private clinic in Dubai, mainly catering to the expatriate Indian population.

This is a retrospective study of the antibiotic sensitivity profile of 107 positive culture samples collected over a period of 17 months starting from January 2004. The samples which included pus from various lesions, urine, stool, throat swab and vaginal swabs were carefully collected without contamination from external sources according to NCCLS guidelines.2 The culture media used in our study were nutrient agar, blood agar (incubated anaerobically if necessary), chocolate agar, CLED agar (for urine) and Mc Conkey's agar.

Bacterial growth was identified based on the colony characteristics, Gram's stain and biochemical reactions.3 Antimicrobial susceptibility tests were done by the Bauer - Kirby method using Mueller - Hinton agar.4 The diameter of the zone of inhibition in millimeters was scored as per Table 1.

Mean Sensitivity Score was calculated as per the following formula.
Mean Sensitivity Score = (Total Sensitivity score / No. Of samples analyzed) x 100

We collected data from 107 positive culture samples belonging to 74 male and 33 female patients. The age distribution is as per Figure 1. Urine and throat swabs showed maximum positivity with 37 and 28 each. The number of various samples showing positive culture is depicted in Figure 2. E-coli was the commonest organism grown in urine and stool while streptococcus pyogenes was predominantly seen in throat swabs. The complete list of all the organisms isolated is shown in Table 2. The Total sensitivity score of each organism against commonly used antibiotics is given in Table 3. E-coli showed maximum sensitivity to ciprofloxacin (Mean score = 85) while streptoccus aeureus and streptococcus pyogenes showed maximum response to penicillin G (Mean score = 100). The Mean sensitivity score of commonly used antibiotics is shown in Figures 3 and 4.

E.Coli was the predominant organism isolated in Urine and stool samples. However ear, nose and throat samples showed mainly gram +ve organisms like Staph. Aureus and Streptococcus pyogenes. Klebsiella was the commonest Gram -ve organism isolated from these samples.

Gram +ve organisms showed maximum sensitivity to Penicillin G and Erythromycin while Ciprofloxacin was most effective against Gram -ve organisms. Co-trimoxazole showed a broad spectrum of activity and it performed better than Amoxycillin with Clavulanic acid. Among the parenteral antibiotics Gentamycin fared better than most third generation Cephalosporins.

Co-Trimoxazole and Gentamycin are rarely used these days because of the allergic reactions5 and ototoxicity6 respectively. Hence these old antibiotics are still effective in most infections. However the widely used newer antibiotics are slowly becoming less effective in this region.

There are reports of even Methicillin Resistant Staph Aureus responding to Co trimoxazole.7 However the use of Co-Trimoxazole as a prophylactic antibiotic in HIV infected patients may change its sensitivity profile in the future.8 The objectives of an antibiotic strategy are to implement clinical guidelines which cover the treatment of an individual patient and the policies based on these which will have maximum effects in public health.9

Figure 1. Age distribution of patients.

Figure 2. Number of various samples showing positive culture.

Table 2. The growth of various organisms in the samples.

Table 3. The Total sensitivity score of each organism against commonly used antibiotics

Figure 3. Mean sensitivity of commonly used predominantly oral antibiotics.

Figure 4. Mean sensitivity of commonly used parenteral antibiotics.