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SUSCEPTIBILITY PATTERN OF COMMONLY ISOLATED MICROORGANISMS FROM CHRONIC SUPPURATIVE OTITIS MEDIA.

Byline: Zakirullah Zakirullah, Muhammad Ismail Khan and Israr Uddin Khan

ABSTRACT

Background: The knowledge of the local pattern of infection in chronic suppurative otitis media is essential to enable efficacious treatment for it. The objective of the study was to study the bacterial flora and their antimicrobial susceptibility pattern among isolated pathogens of chronic suppurative otitis media.

Material and Methods: This cross-sectional study was carried out in the Department of ENT, Khyber Teaching Hospital, Peshawar from January 2014 to December 2014. A sample size of 123 patients was selected through consecutive sampling technique. Swabs taken from the ear discharge were subjected to culture and sensitivity tests using modified Kirby Bauer disk diffusion method.

Results: Out of 123 specimens, there were 110 (89.45%) positive cultures for bacteria. The most common causal organisms isolated were Pseudomonas aeruginosa in 35 (31.8%) and Staphylococcus aureus in 32 (29.1%) followed by Proteus species in 16 (14.55%) and Morganella in nine (8.25%) cases. Antibiotic sensitivity pattern of Pseudomonas aeruginosa showed 100% sensitivity to meronem while Staphylococcus aureus were 100% sensitive to vancomycin.

Conclusion: The commonest isolates were Pseudomonas aeruginosa and Staphylococcus aureus in chronic suppurative otitis media patients. Pseudomonas aeruginosa showed 100% sensitivity to meronem while Staphylococcus aureus were 100% sensitive to vancomycin.

KEY WORDS: Suppurative otitis media; Culture; Kirby-Bauer disc diffusion method; Pseudomonas aeruginosa; Staphylococcus aureus; Morganella morganii; Escherichia coli; Vancomycin; Ceftazidime; Cefotaxime.

INTRODUCTION

The global prevalence of CSOM is approximately 65-330 million per year, with high prevalence from Southeast Asia, Western Pacific, and African continent.1 Chronic suppurative otitis media (CSOM) is a commonly encountered infection of middle ear. It is a condition associated with perforated tympanic membrane with persistent discharge from the middle ear that last for more than 6-12 weeks which is relatively difficult to treat.2,3 CSOM is usually initiated by an acute episode of infection where inflammation of the middle ear occurs. Thus the knowledge of the local pattern of infection is essential to enable efficacious treatment of CSOM. The most commonly reported microorganism is Pseudomonas aeruginosa followed by Staphylococcus aurous.4,5 Nevertheless, the etiology changes from time to time with changes in the susceptibility patterns of microorganisms to the commonly used antibiotics.

The objective of the study was to study the bacterial flora and their antimicrobial susceptibility pattern among isolated pathogens of chronic suppurative otitis media.

MATERIAL AND METHODS

This cross-sectional study was carried out in the Department of Otolaryngology and Head and Neck Surgery, Khyber Teaching Hospital, Peshawar, Pakistan from January 2014 to December 2014. A sample size of 123 patients was selected through consecutive non-probability sampling technique. An informed consent was taken from each patient. Ethical approval for the study was also taken from Hospital Ethical and Research Committee.

All patients with perforated tympanic membranes and active purulent discharge were included in the study. Patients who had received antibiotic therapy (topical or systemic) within last five days and patients with cholesteatoma were excluded.

Specimens were collected in sterile containers from the ear discharge using pre-packed cotton swabs and sent to Microbiology Department of Khyber Medical College, Peshawar without delay where they were cultured for 24 hours at 37C aerobically. Bacteria grown were cultured and identified using gram staining techniques and other relevant biochemical tests. Antibiotic susceptibility was determined by standard Kirby-Bauer disc diffusion method using different antibiotics from different groups of antimicrobial agents. Briefly describing, Mueller-Hinton agar was prepared in distilled water. The mixture was thoroughly mixed with constant agitation. Upon boiling for 1 minute, all the constituents were dissolved, autoclaved for 15 minutes at 121C and dispensed the sterilized medium to sterilized petri dishes with approximate 4 mm thickness of medium under aseptic condition.

Culture sensitivity discs for commonly used antibiotics (cephradine, ceftazidime, cefotaxime, cefexime, ciprofloxacin, levofloxacin, amikacin, tazocin, meronem and gentamicin) were used against the most commonly isolated microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, Proteus species and Morganella morgagni). Zone of inhibition was determined.

The demographic variables were sex and age grouping. The research variables were isolation of microorganisms and their susceptibility to various antimicrobials. Age in years was categorized as; less than 11 years, 11-20 years, 21-30 years, 31-40 years, 41-50 years, 51-60 years, and greater than 60 years. Age grouping was ordinal data and the rest were nominal data. Frequency and relative frequency were calculated using SPSS V. 16 (SPSS Inc., Chicago, IL, USA).

RESULTS

Out of 123 specimens, 69 (56.1%) were from male and 54 (43.9%) from female patients. The modal age group was of 11-20 years with frequency of 43 (34.95%). Table 1

Out of 123 specimens, there were 110 (89.45%) positive cultures for bacteria. One hundred and six patients (63.3%) had a single organism isolated from the culture; four (3.25%) patients had two or more organisms isolated, and the remaining 13 (10.56%) patients had sterile cultures. The most common causal organism isolated was Pseudomonas aeruginosa in 35 (31.8%). Table 2 Antibiotic sensitivity pattern of Pseudomonas aeruginosa showed 100% sensitivity to meronem while Staphylococcus aureus were 100% sensitive to vancomycin. Table 3 and Table 4

DISCUSSION

The frequency of complications of CSOM was very high i.e. 2.3% of the cases in the past; it has decreased to 0.15-0.4% with the development of newer antibiotics. But it is still high in the underdeveloped countries like Pakistan because of late presentation and poor socioeconomic status of the people.6 The treatment of active stage of chronic suppurative otitis

Table 1: Patients with CSOM in different age groups. (n=123)

Age (years)###Frequency###Relative frequen-

###cy (%)

less than 10###10###08.10

11-20###43###34.95

21-30###19###15.45

31-40###22###17.95

41-50###16###13.00

51-60###08###06.55

reater than 60###05###04.00

Total###123###100.00%

Table 2: Isolated microorganisms from the swab of CSOM patients (n=110)

S. Types of###Frequen-###Relative

No. organisms###cy of###frequency

###isolates###of isolates

1###Pseudomonas###35###31.80

###aeruginosa

2###Staphylococcus###32###29.10

###aureus

3###Proteus spp.###16###14.55

4###Morganella###09###08.25

###morganii

5###Escherichia coli###04###03.65

6###Citrobacter spp.###04###03.65

7###Enterobacter spp.###02###01.80

8###Klebsiella pneu-###01###00.90

###monia

9###Aspergillus###01###00.90

10###Serratia###01###00.90

11###Staphylococcus###01###00.90

###epidermidis

12###Pseudomonas+-###03###02.70

###Staph

13###Staph+Entero-###01###00.90

###bacter

###Total###110###100%

Table 3: Sensitivity of Pseudomonas aeruginosa to various antibiotics (n=35)

S. Antibiotics###Frequency###Relative

No.###of sensitive###frequen-

###Isolates###cy

1###Ceftazidim###31###88.55

2###Cefotaxime###13###37.15

3###Cefixime###00###00.00

4###Ciprofloxacin###18###51.40

5###Levofloxacin###09###25.70

6###Amikacin###27###77.10

7###Tazocin (Tazobac-###33###94.28

###tum-Piperacillin)

8###Meronem###35###100.00

9###Gentamicin###12###34.00

Table 4: Sensitivity of Staph. Aureus to various antibiotics (n=32)

S. Antibiotics###Frequency###No of

No.###of sensitive sensitive

###Isolates###Isolates

1###Ceftazidim###23###71.90

2###Cefotaxime###25###78.10

3###Levofloxacin###22###68.74

4###Cefixime###13###40.60

5###Ciproxin###23###71.90

6###Amikacin###30###93.75

7###Tazocin (Tazobac-###31###96.85

###tum-Piperacillin)

8###Gentamicin###17###53.10

9###Vancomycin###32###100.00

media needs to be instituted as early as possible to avoid its related complications like labyrinthitis, facial nerve paralysis and intracranial abscesses. In our study majority of the patients were in their second decade of life, which is also supported by another local study.7 Contrary to our reports another study has reported majority of the patients in third decade of life.8 Our study reveals male predominance, with similar results reported by other studies as well.7,8 But on the other hand another local study has reported a female predominance.9 The most probable reason for predominance of male patients in our study may be due to reason that female patients are not brought out of their homes in our society, and they do not get the preferential treatment.

Our results showed that active CSOM infection in the tertiary care hospital is mainly due to Pseudomonas aeruginosa and Staphylococcus aureus.

Almost similar results regarding the pattern of CSOM infection have been reported by other studies.10-13

Contrary to our results other studies14,15 have reported an isolation of anaerobes in significant number of their patients.

In the present study Pseudomonas aeruginosa was shown to be 100% sensitive to meronem; a carbapenem group of antibiotics. Local literature has also reported similar results.16,17 Third-generation cephalosporins are most frequently prescribed in active stage of CSOM and displays an extended gram negative coverage. In our study 88% of P. aeruginosa isolates were found to be sensitive to ceftazidime which is also supported by another study.18 On the other hand only 37% of isolates showed sensitivity to cefotaxime in our study; meaning that in our set up, ceftazidim is effective but resistance against cefotaxime has increased in the recent past.

Staphylococcus aureus; the second most common isolate in our study was 100% sensitive to vancomycin, 97% to tazocin, 93% to amikacin, 78% to cefotaxime and 72% to ceftazidim. This susceptibility pattern of Staphylococcus aureus found in our study against most of the antimicrobials is almost consistent with local literature.13,19,20 The third most commonly isolated organism Proteus spp. was sensitive to ceftazidime, cefotaxime, ciprofloxacin, amikacin, tazosin, and ceftriaxone in descending order.

CONCLUSION

The commonest isolates were Pseudomonas aeruginosa and Staphylococcus aureus in chronic suppurative otitis media patients. Pseudomonas aeruginosa showed 100% sensitivity to meronem while Staphylococcus aureus was 100% sensitive to vancomycin.

Acknowledgements: Dr. Muhammad Marwat, Gomal Medical College, D.I. Khan is acknowledged for critical appraisal of the manuscript.

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18. Mansoor T, Musani MA, Khalid G, Mamal M. Pseudomonas aeruginosa in chronic suppurative otitis media: sensitivity spectrum against various antibiotics in Karachi. J Ayub Med Coll Abbottabad 2009; 21: 120-3.

19. Ahmad A, Usman J, Hashim R. Isolates from chronic suppurative otitis media and their antimicrobial sensitivity. Pak Armed Forces Med J 1999; 49: 82-5.

20. Ahmad B, Hydri AS, Afridi AAK, Ejaz A, Farooq S, Zaidi SK. Microbiology of ear discharge in Quetta. J Coll Physcians Surg Pak 2005; 15: 583-4.
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Publication:Gomal Journal of Medical Sciences
Article Type:Report
Date:Jun 30, 2015
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