The study design was a single blind comparative study that included forty three children aged between 2-14 years of both gender with recurrent tonsillitis who were scheduled for tonsillectomy with no history of allergy to beta-lactams or macrolides antibiotics. Patients with preexisting medical condition that might affect drug pharmacokinetics or requiring perioperative antibiotics (i.e., endocarditis), or with history of antibiotic use within 2 weeks prior to tonsillectomy or with history of significant hematological, renal and hepatic disease, were excluded from the study.

The study was conducted with the approval of the Ethical Committee of the College of Medicine, Hawler Medical University and informed consent was taken from parents of each patient after explaining the study protocol in keeping with the Ethical Committee policy.

The patients were allocated randomly into 2 groups. The children were given the drug suspension by a calibrated syringe so that the volume of suspension given is measured precisely. Group 1 patients (n=23) were given amoxicillin-clavulanic acid (Julmentin®; Julphar, UAE) and azithromycin (Zomzx®; Hikma, Jordan) was given to group 2 patients (n=20). The drugs were given orally a day before and approximately 2 hours before the scheduled time of surgery at the recommended dose of 10 mg/kg for azithromycin and 156mg/5ml (24.96 mg/kg/day) for amoxicillin-clavulanic acid. Before starting medications, sterile swabs were taken from the core of the tonsil of each patient for microbiological isolation of bacteria (11) and thereafter bacteria were identified to the species level by VITEK 2 colorimetric identification card (12). The minimum inhibitory concentration (MIC) of each isolate was determined by broth dilution method according to the National Committee for Clinical Laboratory Standards (13).

Samples from venous blood were taken from each patient before drug administration and at time of operation corresponding to 2 hours after drug administration. The blood samples were collected in heparinized tubes and plasma was obtained by centrifugation of blood samples for 10 minutes. Tonsils were taken at the time of operation at the surgical theatre at times relevant to timing of the blood samples, weighed, wiped gently with dry sterile gauze. Plasma and tonsils samples were immediately stored in deep freeze (-40 C) until analyzed by the microbiological assay method using standard S. aureus ATCC (6538P) sensitive to azithromycin and amoxicillin-clavulanic acid according to (14, 15) respectively.

For the determination of drugs concentrations, drug-free plasma and tonsil samples were spiked with different concentrations of each drug separately. The standard concentrations were analyzed in triplicate along with the samples by the microbiological assay method mentioned above and a standard curve was generated relating the diameter of zone of inhibition (mm) with different concentrations of either drug. Calculations of azithromycin and amoxicillin-clavulanic acid concentrations in plasma and tonsils samples were determined according to (16). The limit of detection for azithromycin and amoxicillin -clavulanic acid in plasma and tonsils were 0.01 µ g/ml and (0.05 µg/g respectively.

SPSS version 19 was used to analyze the differences between different concentrations of the drugs in plasma and tonsils samples. A P < 0.05 was considered statistically significant difference.

The mean age of children was 5.25±2.13 years and 5.7 ± 2.68 year for amoxicillin-clavulanic acid and azithromycin group respectively (Table 1). The children had a mean weight of 20.42 ±5.49 kg and the ratio of distribution of male: female was 1.53:1 (Table 1).

Different microorganisms were isolated from the tonsils taken from the patients and S. aureus was isolated from the majority of the patients (Table 2).

Table 2: Microorganisms isolated from the tonsils of patients in different treatment groups


S. pyogenes isolated from patients was resistant to both amoxicillin-clavulanic acid and azithromycin antimicrobial agents whereas S. agalactiae was sensitive to amoxicillin-clavulanic acid but resistant to azithromycin. Four S. aureus isolates were sensitive, 2 were intermediately sensitive and only one was resistant to amoxicillin-Clavulanic acid while all four isolates of S. aureus were resistant to azithromycin antimicrobial agent as shown in Table (3).

Table 3: Susceptibilities of different micro-organisms isolated from tonsils of the patients to amoxicillin-clavulanic acid and azithromycin


The mean concentrations of amoxicillin-clavulanic acid and azithromycin in plasma were 5.49± 0.33µg/ml and 0.27 ± 0.04µg/ml respectively. In the tonsils, the mean concentrations of azithromycin was 13.97 ± 2.75 µg/g whereas no detectable concentrations were determined for amoxicillin-clavulanic acid in tonsils according to the limit of detection of the assay (Table 4).

Table 4: The mean concentration of Amoxicillin-clavulanic group and Azithromycin in plasma and tonsils tissue

To obtain an effective clinical response to antimicrobial therapy, the drug should reach effective concentration at the site of infection greater than the MIC of the causative organisms (3, 4).

S. aureus was the most predominant organism (27.27%) isolated from the patients in the present study and has also been reported in other studies as the most predominant pathogen isolated from children with recurrent tonsillitis (6, 11). S. pyogenes was only isolated from 2 patients (4.55%) in the present study, which is also in accordance to other findings (11, 17). Another study stated that among a total of 294 children with acute tonsillitis, Group A streptococci was isolated only from three children (18).

The mean plasma amoxicillin concentration (5.49±0.33 µg/ml) estimated in the plasma of the patients, indicates that amoxicillin is well absorbed into systemic circulation. Indeed amoxicillin has high oral bioavailability (70-90%) with peak plasma levels occurring within 1 to 2 hours (19-21). This mean plasma levels (5.49 µ g/ml) is close to those determined (4.7 µ g/ml) in children (22) although higher peak concentration of 7.32 µg/ml and 10.8 µg/ml was detected 2 hours in adult volunteers given amoxicillin-clavulanic acid at a dose similar to those administered in the present study (20,21). The differences in the concentrations is most likely related to differences in the drug formulations, amount of dose given or to the analytical method of analysis. Based on recommendations of therapeutic effectiveness of beta-lactams in humans and experimental studies; the concentrations of antibiotic is required to be four to five times the MIC or higher when associated with improved outcome especially with resistant strains (23,24) thus, although levels of amoxicillin-clavulanic acid in plasma were higher than the MICs of the isolated species, this antibiotic did not attain effective concentrations in the site of infection (tonsils) to eradicate the resistant organisms ( 24). The S. pyogenes that was isolated from the patients was considered resistant according to the breakpoint therefore this antibacterial agent would not provide an effective treatment especially in recurrent cases with resistant organisms.

Furthermore, although plasma concentrations are generally a good indicator of drug effectiveness they are usually a poor indicator of intracellular concentrations, which is of major importance for intracellular pathogens including S. aureus as well as S. pyogenes that are also shown to be intracellular pathogen of tonsils (25, 26). One of the properties that characterize beta-lactams including amoxicillin is that they are weak acids and quickly diffuse into cells and because the cell cytosol is more acidic than extracellular milieu they will be more in unionized form so they are prevented from accumulating in the cells and will readily be absorbed to systemic circulation (27, 28). Studies recommended administering amoxicillin-clavulanic acid at higher dose are based on their finding that one high dose of amoxicillin-clavulanic acid would inhibit the biofilm formed in the tonsillar tissue therefore exposing the bacteria to effective treatment since recurrent pharyno-tonsillitis and failure of treatment has been attributed to biofilm formation (29, 30).

Concerning azithromycin, the mean plasma concentrations of (0.27 ± 0.04 µg/ml) is close to those reported (0.24 ?g/ml) in children receiving 30 mg azithromycin (31). However, lower concentrations in plasma (0.18 µ g/ml) were estimated by (32) and 0.13 µg/ml by (33). These differences are related to differences in dosing, different drug formulations and method of drug analysis. The mean azithromycin concentrations (13.96 ± 2.75 µg/g) in tonsillar tissues indicate this drug undergoes rapid uptake from systemic circulation into the infection site thus exposing the local compartment (tonsils) to azithromycin concentrations higher than plasma levels. High ratio of azithromycin concentration in tonsils to that in plasma was also reported and shown to be greater than plasma concentrations by many fold for all time intervals after administration (15, 33).

One of the remarkable features of azithromycin is its ability to accumulate in intracellular compartments, mainly in fibroblasts, phagocytic cells, and other white blood cells (34). This prominent character is explained by its dibasic molecular structure that allows azithromycin to be concentrated within the acidic lysosomes of white blood cells due to an ion-trapping mechanism from where it will be released very slowly from intracellular compartments (35). This characteristic is believed to account for the prolonged drug concentrations in tissues which are reported to persist long after the end of therapy and reflected by a long elimination half-life of up to 5 days (36 ).

In conclusion; although amoxicillin-clavulanic acid is clinically considered more effective against beta-lactamase producing organisms and is the most frequently prescribed antibiotic for such infection (9,37) azithromycin's good tissue penetration, once daily administration, besides its immunomodulatory effects provides further benefits along with its dual antibacterial mode of action (38, 39) and makes this antibiotic a good choice when the standard penicillin V therapy of tonsilo-pharyngitis fails. Furthermore, the consequences of the low amoxicillin-clavulanic acid levels in tonsils might lead to potentially negative effects on clinical response and emergence of resistances (40).

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