Antimicrobial Susceptibility Pattern of Bacterial Pathogens in Our Setup: Ear, Nose and Throat Perspective

With a high prevalence of infections involving the ear, nose, and throat, and the occurrence of drug resistance the antimicrobial susceptibility pattern of bacterial pathogens is of immense importance. Objective: To determine the antimicrobial sensitivity pro�le of pathogenic bacteria isolated from representative infected areas of patients with ear, nose, and throat infections. Methods: This cross-sectional observational study was conducted at Ear, Nose and Throat (ENT) Outpatient Department (OPD), Capital Hospital Islamabad, over two years. The sample included 639 pathogenic bacterial culture specimens, grown from the representative infected ear, nose, or throat of patients who attended ENT outpatients of the hospital. The bacterial cultures were subjected to the standard disc agar diffusion method to know the antimicrobial susceptibility pro�le. Data collected included the patient's age, gender, area/ site of infection, bacterial pathogen isolated, and sensitivity to antibiotics. Results: The sample included 49.30% males and 50.70% females and mean age of 30.13±19.24 years. Gram-positive organisms were predominant [n=441, (69.01%)] with Staphylococcus aureus being the commonest isolate (67.92%) followed by Pseudomonas spp. (26.13%). Gram-positive isolates were sensitive to Cefoperazone+Sulbactam, Ceftazidime, Cefoperazone, Amikacin, Pipercillin+Tazobactam, Vancomycin, Gentamycin, Linezolid, Amoxicillin + Clavulanate, and Ceftriaxone with resistance to Ce�xime, while the Gram-negative isolates were sensitive to Vancomycin and Meropenum, Cipro�oxacin, Levo�oxacin, Ceftriaxone and Ceftazidime and highly resistant to Ce�xime, Cefuroxime, Amoxicillin+Clavulanate and Co-trimoxazole. Conclusions: Since ENT infections are predominated by Staphylococcus aureus and Pseudomonas spp. When unavoidable the empirical therapy should cover these pathogens, however culture and sensitivity studies are justi�ed keeping in view the growing resistance to antimicrobials.

discouraged [8].Chew et al., in their study noted predominance of different pathogenic bacteria in ENT infections differing between tropical and non-tropical regions and proposed that tropical areas should not adopt the antibiotic guidelines meant for non-tropical in toto [9].Also, literature search revealed numerous other studies on bacterial ora and antimicrobial sensitivity of isolates worldwide including Pakistan with variation in bacterial ora in ENT infections in different areas including different areas of Pakistan [10][11][12][13].The difference may be due to so many factors including socioeconomic, access of masses to healthcare, food preferences and usage of different antimicrobials [14].Since different bacterial pathogens predominate in different parts of country, empirical prescription of antibiotics can contribute to drug resistance [15], therefore current study was conceived to nd out the locally prevalent bacterial ora and antimicrobial sensitivity pattern in a clinical setup to improve future drug prescription and hamper development of drug resistance.This study is of importance, since it will help clinicians in better prescription of antibiotics to their patients and hamper development of drug resistance., with DEFF=1, con dence limit of 5%, and population 1000000, and n=25 cultures with fungal growths excluded, leaving behind a sample of N= 639 which was utilized for the study, which were grown by routine microbiological culture methods form representative infected ear (535, 83.89%), nose (97, 15.18%) and throat (7, 0.93%) of patients, who visited Otorhinolaryngology outpatients of Capital Hospital, Islamabad with respective ENT infections and including both genders and all age groups.These were subjected to antimicrobial sensitivity testing using standard disc agar diffusion method and the inoculum to be tested were compared with 0.5 McFarland turbidity standard, to know the antimicrobial susceptibility pro le of bacterial pathogens.The antimicrobial discs used included Ceftriaxone (CRO) n=576, Ceftazidime (CAZ) n=196, Cefuroxime (CXM) n=265, Cefoperazone (CFP) n=4), Ce xime (CFM) n=516, Levo oxacin (LVX) n=587, Cipro oxacin (CIP) n=605, Vancomycin (VA) n=395, Amikacin (AMK) n=154, Gentamycin (GEN) n=454, piperacillin+ tazobactam (TZP) n=208, Cefoperazone + Sulbactam (SCF) n=32,Co-trimoxazole n=11, Meropenem (MEM) n=1, Linezolid (LZD) n=402, Amoxicillin + clavulanic acid (AMC) n=631 and Erthromycin (ERY) n=7.Following placement of antibiotic discs, plates were incubated for 16 to 18 hours at 37oC and zone size was interpreted against each antimicrobial disc for each organism and measured in millimeter (mm).Sensitivity was recorded as resistant, intermediate and sensitive using zone interpretation chart [16].Data collected and recorded included patient's age, gender, site of infection, bacterial isolate and sensitivity to antimicrobials.Data were collected, and analyzed using Microsoft Excel Worksheet and expressed in frequency, percentage and cumulative percentage and cross tabulated.Data were then compared with the local and international literature and deductions made were discussed.

M E T H O D S
Of a total number of 639 samples (swabs) with pathogenic bacterial cultures isolated for the study obtained from infected patients' representative infected areas of ear, nose and throat.These included samples from 49.30% males and 50.70% females (Figure 1) with mean age of 30.13 + SD 19.24 years with majority i.e., 73.08% pathogenic cultures isolated in less than 40 years age groups (Table 1).Gram Negative organisms showed high sensitivity to VA and MEM (100%), very good sensitivity to CIP (89.69%),LVX (89.01%),CRO (87.79%) and CAZ (82.6%), while the gram-negative organisms were highly resistant to CFM 74.73%, CXM (59.73%),AMC (56.93%) and Co-Trimoxazole (50%).Sensitivity pattern of the most prevalent Gram positive (Staphylococcus aureus) and Gram negative (Pseudomonas spp.) is given in table 4. Staphylococcus aureus which was predominant organism was sensitive to Amoxicillin+Clavulanate (93.47%) and most other drugs but resistant to Ce xime (45%) (Table 4).In another local study by Marium et al.,[11] in CSOM cases, the predominating organism was Staphylococcus aureus 30 (65.2%) followed by Pseudomonas (15.2%),Proteus mirabilis (13.1%) and Escherichia coli (6.5%) which were sensitive to Ceftriaxone (89.2%) followed by O oxacin (82.6%), Cefotaxime (69.6%),Cephradine (63.1%),Augmentin (60.9%),Erythromycin (52.2%),Ampicillin (2.9%) and Cephalexin (26.1%) with the least sensitivity to Ce xime (39.2%), which was also found to be least sensitive in our study.Abdullah et al.,(13) in a study on infected ears, noted that the most effective antimicrobials for empirical t r e a t m e n t w e r e P i p e r i c i l l i n + T a z o b a c t a m , Cefoperazone+Sulbactam, Imipenam, and Fosfomycin.Whereas Cipro oxacin and Amoxicillin+Clavulanate showed intermediate sensitivity, and the majority of the bacterial isolates were indifferent to Cotrimoxazole, Ce xime, Lincomycin, Doxycycline and Polymyxin B. According to Elies et al.,[19], Pseudomonas aeruginosa is a bug that should be well covered by antimicrobial therapy.According to them though, Cipro oxacin and Ceftazidime are widely used however, Cipro oxacin resistance increased, while Ceftazidime sensitivity is unchanged.Also, Afolabi et al., found Pseudomonas aeruginosa to be the commonest middle ear pathogen which has sensitivity in favor of cipro oxacin (20).In a local study by Arshad et al., Staphylococcus aureus and Pseudomonas were equally prevalent in otitis externa and showed excellent sensitivity to Imipenem, Enoxacin, Cipro oxacin, and O oxacin but resistance to Amoxicillin,and Erythrocin [21].In a prospective randomized study in cases of COM with Pseudomonas aeruginosa as the commonest pathogen, Khanna et al., noted no role of culture and sensitivity in initial management and proposed broad spectrum antimicrobials keeping culture and sensitivity reserved for failed cases [22].However, it is advisable to study resistance pro les and uctuations to ensure suitability of empirical treatment [23].On the other hand,

D I S C U S S I O N
The current study revealed a predominance of Gram-Positive organisms to the tune of 69.02% (n=441) with a s e n s i t i v i t y a s s h o w n i n t a b l e 3 , o f 1 0 0 % w i t h Cefoperazone+Sulbactam, Ceftazidime, Cefoperazone, and Amikacin, while this group was highly resistant to Ce xime.In another local study, Kabeer S et al noted a high sensitivity of Gram-positive organisms to Vancomycin (100%) followed by amikacin (94.87%) [10].In the current study, Gram Negative organisms which accounted for 30.98% (n=198) of cultures, showed excellent sensitivity to Vancomycin and Meropenum (100%), very good sensitivity to Cipro oxacin (89.69%),Levo oxacin (89.01%),Ceftriaxone (87.79%) and Ceftazidime (82.6%), while they were highly resistant to Ce xime (74.73%),Cefuroxime (59.73%),Amoxicillin+Clavulanate (56.93%) and Co Trimoxazole (50%).In contrast, Kabeer et al.,[10], reported that susceptibility was high to Sulbactam/ Cefoperazone (96.46%),Piperacillin+Tazobactam (96.1%).Here, in contrast to our study Gram-negative organisms showed ve r y p o o r s e n s i t i v i t y to C e f t r i a xo n e ( 3 8 .9 4 % ) , Chloramphenicol (38.05%),Cefotaxime (31.86%),Amoxicillin+Clavulanic acid (30.09%) and Cefuroxime (23.01%).Current study revealed that the dominating organism was Staphylococcus aureus (67.92%) followed by Pseudomonas (26.13%).Similarly, in a Nepalese study by Dechen, Staphylococcus aureus was predominant with overall sensitivity to Amoxicillin (53.84%),Cloxacillin (53.84%),Cipro oxacin (46.15%),Gentamicin (46.15%), and Cephalosporin (46.15%) and resistance to Erythromycin, Tetracycline, Co-Trimoxazole and Nor oxacin [17].In contrast in a local study Pseudomonas Spp. was the predominant organism followed by Staphylococcus aureus [10,12].Similarly, in an Ethiopian study by Hailu et al.,[18] the predominating organism was Pseudomonas (29.7 %) followed by Staphylococcus aureus (26.3 %) with a high level of resistance to Amoxicillin+Clavulanic acid, Ampicillin, and Penicillin.In our study, Pseudomonas was r e s i s t a n t to A m ox i c i l l i n + C l a v u l a n a te ( 5 8 . This cross-sectional observational study using convenient s a m p l i n g , w a s c o n d u c t e d a t D e p a r t m e n t o f Otorhinolaryngology, Capital Hospital, and Islamabad, Pakistan over a period of two years.Study was conducted after obtaining ethical approval from Institutional Research Board of Capital Hospital vide letter No. 2024-03-007.The sample of the study included 639 pathogenic bacterial culture specimens.A sample size of n=664 was calculated using the formula: n = [DEFF*Np(1-p)]/ [(d2/Z21α/2*(N-1)+p*(1-p)]

Table 3 :
Antimicrobial Susceptibility Pattern of Gram Positive and Gram Negative Bacteria: Antimicrobial Drug * Microbial Group.Cross Tabulation (n = 639)

Table 4 :
Antimicrobial Susceptibility Pattern of Prevalent Gram Positive and Gram Negative Bacteria Isolated