susceptibility of S. typhi against Cefixime. MIC of. Azithromycin also improves with addition of Cefixime. Addition of Clavulanic acid improves antimicrobial action.
Indian Medical Gazette
101
— MARCH 2015
Comparative Study
In-Vitro Study of Antimicrobial Activities of Five Different Commercial Fixed Dose Combination Drugs in Indian Market Chhaya Sawant, Scientific Officer, SVKM’s Shri C. B. Patel Research Centre, Mumbai. Rucha Pandit, Medical Advisor, Abbott Truecare, Abbott Healthcare Pvt. Ltd., Mumbai.
Objective: In-vitro determination of antimicrobial activities of five different fixed dose combination drugs (FDC). Material and methods: Five antibiotic combination tablets [Cefadroxil plus Clavulanic acid (500:125 mg), Cefuroxime plus Clavulanic acid (500 : 125 mg), Cefixime plus Clavulanic acid (200 : 125 mg), Cefixime plus Ofloxacin (200 : 200 mg) and Cefixime plus Azithromycin (200 : 500 mg)] were tested for antimicrobial action against different microorganisms after their successful incubation for 18 hours at 37°C. Broth dilution or agar dilution methods were used to evaluate susceptibility of microorganisms. Results: z Minimum inhibitory concentration (MIC) of Cefadroxil in combination with clavulanic acid reduced by 25%, 29%, 85% and 50%, against S. aureus, K. pneumonia, H. influenzae and S. pneumoniae respectively. z No reduction was seen in MIC of Cefuroxime against S. aureus, K. pneumonia, H. influenzae, E. coli or S. pneumoniae after addition of Clavulanic acid. z MIC of Cefixime against S. pneumoniae reduced from 0.2 to 0.14 when combined with Clavulanic acid. z MIC of Ofloxacin against K. pneumoniae, E.coli and S. pneumoniae reduced by 82%, 50% and 85% respectively in combination with Cefixime. z MIC of Cefixime against E.coli, S. typhi and S. pneumoniae reduced by 95%, 90% and 40% respectively in combination with Ofloxacin. z MIC of Cefixime against S. typhi and S. pneumoniae reduced by 33.33% and 60% respectively with
addition of Azithromycin. z MIC of Azithromycin against S. typhi reduced by 70% after addition of Cefixime. Conclusion: Combination of Cefixime and Ofloxacin improves susceptibility of E. coli and S. pneumoniae. Addition of Azithromycin or Ofloxacin improves susceptibility of S. typhi against Cefixime. MIC of Azithromycin also improves with addition of Cefixime. Addition of Clavulanic acid improves antimicrobial action of Cefixime against S. pneumoniae and Cefadroxil against S. aureus, K. pneumonia, H influenza and S. pneumonia. Keywords antimicrobial susceptibility, combinations, in-vitro Introduction In clinical practice, antimicrobial combinations are often used to broaden the spectrum of antimicrobial coverage. While using combination therapy, it should be noted that individual components are not antagonistic to each other1. Moreover, combination of antimicrobials is attempted to prevent development of resistant strains. Increasing rates of antibiotic resistance is one of the major issues about antimicrobial therapy today2. The emergence of rising antimicrobial resistance is not just a result of misuse of antibiotics; rather it is a natural biological trend with use of
Indian Medical Gazette
102
antimicrobial over the period of time3. The discovery of new class of antimicrobial has lagged behind the emergence of speedy resistance. The globe witnessed one after the other discoveries of antimicrobial agents between 1930 and 19703; however, since last three decades, there seems a sluggish walk with limited success on the road of discovery for fighting against infections. On the other hand, rates of infection are amplifying. In a scenario of emerging multidrug resistance, physician has to look for an alternative therapeutic drug from the available options4. Today, even the alternatives are becoming limited because of an increase in rate of resistance in India. In this gloomy state, physicians have to rely on the combination of different antimicrobials for successful management of rising infections. Theoretically, beta-lactamase inhibitor, combined with betalactam antibiotic or combination of agents acting on different steps in metabolic pathway of microorganism, could be some of the strategies opted to enhance antimicrobial activity1. In India, even though multiple fixed dose combinations (FDC) of antimicrobials are available, many of these formulations do not have robust in-vitro data showing their microbiological efficiency or clinical efficacy. Objective The study was conducted to determine the antimicrobial activities of five different antimicrobial combinations (Cefadroxil plus Clavulanic acid, Cefuroxime plus Clavulanic acid, Cefixime plus Clavulanic acid, Cefixime plus Ofloxacin and Cefixime plus Azithromycin).
— MARCH 2015
Material and Methods In this in-vitro study conducted in 2011, five fixed dose combinations [Cefadroxil plus Clavulanic acid (500 : 125 mg/tablet), Cefuroxime plus Clavulanic acid (500 : 125 mg/ tablet), Cefixime plus Clavulanic acid (200 : 125 mg/tablet), Cefixime plus ofloxacin (200 : 200 mg/tablet), Cefixime plus Azithromycin (200 : 500 mg/tablet)] available in the India were tested to determine their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) individually and in FDC. Soybean casein digest agar, muller hinton broth nutrient agar, chocolate agar, chocolate broth and brain heart infusion agar were used for growth of microorganisms. For susceptibility testing, dilution methods were used to determine the minimal concentration of antimicrobial agent to inhibit or kill the microorganism achieved by dilution of antimicrobial agent either in agar or in broth media. The MIC against K. pneumoniae, E. coli, S typhi, and S. pneumoniae was determined using broth dilution method. The broth dilution method offers advantages of simplicity for testing as minimal as single microbial isolate and use of same tubes for further MBC test5. Revived stock culture of each of the test microorganism was inoculated onto the surface of suitable medium. Culture conditions for inoculum preparation were as follows (Table 1). After completion of the specified incubation period for the cultures, three to four colonies were transferred using a sterile Nichrom wire loop into sterile saline to obtain a suspension having turbidity equivalent to that
Table 1 Culture conditions for inoculums preparation Test organisms
Growth Medium
Incubation temperature (°C)
Incubation time
Staphylococcus aureus
Soybean Casein Digest Agar
37.0
18 - 24 hours
Klebsiella pneumoniae
Soybean Casein Digest Agar
37.0
18 - 24 hours
Moraxella catarrhallis
Brain Heart Infusion agar
37.0
18 - 24 hours
Haemophilus influenzae
Chocolate agar (Using Muller Hinton Agar)
37.0
24 - 48 hours
Escherichia. coli
Soybean Casein Digest Agar
37.0
18 - 24 hours
Salmonella typhi
Soybean Casein Digest Agar
37.0
18 - 24 hours
Streptococcus pneumoniae
Blood Agar (Using Muller Hinton Agar)
37.0
18 - 24 hours
N. gonorrhea
Chocolate Agar (Using Muller Hinton Agar)
37.0
24 - 48 hours
Indian Medical Gazette
— MARCH 2015
of McFarland’s 0.5 standard, having approximately 107-8 cells/ml. Pilot assay was carried out to determine the range of active concentration of the test drug. The master stock of the test drug was prepared using sterile distilled water. Tenfold serial dilutions of the test drug were prepared using sterile MH Broth as diluent for S. aureus, K. pneumoniae, M. catarrhalis, E. coli, S. typhi, and sterile MH broth with 7% blood as the diluent for S. pneumoniae. As Azithromycin was water insoluble, Dimethyl sulfoxide (DMSO) was used as a solvent. The separate set of DMSO concentrations was tested to check its effect on the test organism. DMSO was found to be ineffective on the test organisms. Each dilution tube was inoculated with 0.1 ml of cell suspension of the test organism having cell density of 107–8 organism/ ml. Tubes were incubated for 24 hours at 37°C for S. typhi, E. coli, and K. pneumoniae. Tubes inoculated with S. pneumoniae were incubated in a candle jar with 5 % CO2 at 37°C for 24 hours. Tubes were observed for turbidity. The range of MIC of the test drug was determined as the concentration of the drug in the tube having no turbidity. This range of concentrations was further used to determine the exact MIC of the test drug. Determination of MIC The master stock of the test drug was prepared using sterile distilled water. The working stock and the concentrations within the range (pilot assay) were prepared using the following formula: RT/G = V (R = Required concentration, T = Total volume, G = Given Concentration, V = Volume to be added). Each dilution tube was inoculated with 0.1 ml of cell suspension of test organism having cell density of 107 – 8 organism/ml. Tubes were incubated for 24 hours at 37 oC for S. aureus, K. pneumoniae, M. catarrhalis, E. coli, and S. typhi. Tubes inoculated with Streptococcus pneumoniae were incubated in a candle jar with 5 % CO2 at 37°C. Tubes were observed for turbidity. MIC was expressed as the lowest concentration of the test drug at which no turbidity was observed. Minimum Bactericidal Concentrations (MBC) 0.1 ml of aliquot from MIC tubes showing no turbidity was inoculated using spread plate technique on to Nutrient agar plates free of any antimicrobial agent for S. aureus, K. pneumoniae, M. catarrhalis, E. coli, S. typhi and blood agar plates free of any antimicrobial agent for S. pneumoniae.
103
Plates were incubated for 24 hours at 37oC for for S. aureus, K. pneumoniae, M. catarrhalis, E. coli, and S. typhi. Tubes inoculated with S. pneumoniae were incubated in a candle jar with 5% CO2 at 37oC for 24 hours. Aliquot from the MIC tubes with the lowest concentration of the test drug that showed no growth on the sub-cultured plate was considered to be the MBC of the test drug for the test organism under investigation. Agar Dilution Method: (MIC against H. influenzae) The composition of the test medium plays an important role in the results of susceptibility test methods with H. influenzae6. H. influenzae being a fastidious microorganism requires blood in the medium making reading the tubes in the broth dilution method difficult. Hence agar dilution method was used for H. influenzae. Agar dilution is a highly reproducible and reliable method for antimicrobial susceptibility testing7. In this procedure, agar dilutions were prepared in petri dishes using solid media as a diluent for testing MIC against H. influenzae. Pilot assay was done to determine the range of active concentration of the test drug. Nutrient agar butts of 17 ml were prepared and sterilized by autoclaving at 121°C and 15lb psi pressure for 20 minutes. Tubes were removed from the autoclave and 1.25 ml sterile whole blood was added to each of the tubes containing hot medium to prepare a Chocolate Agar. Tubes were then cooled and used as diluents for the MIC assay. The master stock (1000 µg/ ml) of the test drug was prepared using sterile distilled water. Tenfold serial dilutions of the test drug to get the concentration range of 100µg/ml to 0.01µg/ml were carried out using sterile distilled water as a diluent. Two ml of each of the dilutions were added to each tube of the cooled media to obtain the required drug concentration and mixed well. The drug mixed media was then poured into the respective sterile petri plate, and allowed to solidify. After the media was solidified, 0.1 ml of cell suspension of the test organism having cell density of 107–8 organism/ml was spread on all the plates. The plates were incubated for 48 hours at 37°C in an atmosphere of 5% CO2. Plates were observed for growth on the surface of the media. The range of Minimum Inhibitory Concentration of the test drug was determined as the concentration of the drug in the plate having no growth on the surface and the successive plate having growth on the surface. This range of concentrations was further used to determine the exact Minimum Inhibitory Concentration of the test drug.
Indian Medical Gazette
104
— MARCH 2015
Determination of MIC
Determination of MBC
Nutrient agar butts of 18 ml were prepared and sterilized by autoclaving at 121°C and 15lb psi for 20 minutes. Tubes were removed from the autoclave and 1.25 ml sterile whole blood was added to each of the tubes containing hot medium to prepare Chocolate agar. Tubes were then cooled and used as diluent for the MIC assay. The master stock (1000 µg/ml) of the test drug was prepared using sterile distilled water. The working stock and the concentrations within the range (pilot assay) were prepared using the following formula: RT/G = V (R = Required concentration, T = Total volume, G = Given concentration, V = Volume to be added). Drug dilutions were prepared from the master stock using sterile distilled water as a diluent. These dilutions were made such that, when 1ml of each dilution was added to the blood agar tube, the required drug concentration was obtained in the medium. One ml of each drug dilution was added to tube of the cooled media and mixed well. The drug mixed media was then poured into the respective sterile petri plate, and allowed to solidify. After the media was solidified, 0.1 ml of cell suspension of the test organism having cell density of 107–8 organisms/ml was spread on all the plates. Plates were incubated for 48 hours at 37°C in an atmosphere of 5% CO2. Plates were observed for growth on the surface of the media. The MIC of the test drug was determined as the least concentration of the drug in the plate having no growth on the surface.
Saline washing (0.1 ml obtained using 2 ml sterile saline) from MIC plates showing no growth on the surface was inoculated using spread plate technique on to Chocolate agar plates free of any antimicrobial agent. Plates were incubated for 48 hours at 37°C in an atmosphere of 5% CO2. Aliquot of the saline washings form the plates with the lowest concentration of the test drug that showed no growth on the sub-cultured plate was considered to be the MBC of the test drug for the test organism. During testing of MIC and MBC for each antimicrobial, positive control (no drug, only test organism), negative control (no drug, no test organism) and drug control (only drug, no test organism) were studied. Results With addition of Clavulanic acid, MIC of Cefadroxil against S. aureus, K. pneumoniae, H. influenzae and S. pneumoniae reduced by 25%, 29%, 85% and 50% respectively. There was no change in MIC against H. influenzae after addition of Clavulanic acid. The MBC of Cefadroxil against S. aureus, K. pneumonia, M. catarrhalis and S. pneumoniae reduced by 50%,40%,33.3% and 75% respectively after addition of Clavulanic acid. The MIC and MBC of Cefadroxil plus
Table 2 MIC and MBC of Cefadroxil plus Clavulanic acid (individual and in FDC) Cefadroxil mcg/ml
Cefadroxil : Clavulanic Acid (500 : 125 mg/tablet) Organism
MIC
MBC
MIC
Concentration of
Concentration of
MBC
Concentration of
Concentration of
Tablet
Cefadroxil (mcg) at MIC of Tablet
Clavulanic acid (mcg) at MIC of Tablet
Tablet
Cefadroxil (mcg) at MBC of Tablet
Clavulanic acid (mcg) at MBC of Tablet
S. aureus
3
1.5
0.375
5
2.5
K. pneumoniae
20
10
2.5
30
M. catarrhalis
2
1
0.25
H. influenzae
30
15
S. pneumoniae
2
1
MIC
MBC
0.625
2
5
15
3.75
14
25
2
1
0.25
1
1.5
3.75
200
100
25
>100
>100
0.25
2
1
0.25
2
4
Indian Medical Gazette
105
— MARCH 2015
Clavulanic acid against S. aureus, K. pneumoniae, H. influenzae, M. catarrhalis and S. pneumoniae is shown in Table 2. There was no reduction in MIC of Cefuroxime after addition of Clavulanic acid against S. aureus, K. pneumonia, H. influenzae, E. coli or S. pneumoniae. The MIC and MBC of Cefuroxime plus Clavulanic acid against four microorganisms is shown in Table 3.
MIC of cefixime against S. pneumoniae reduced from 0.2 to 0.14 mcg/ml, when combined with clavulanic acid. No significant change in MIC was observed against S. aureus, M. catarrhalis, H. influenzae and E. coli. After addition of clavulanic acid, MBC of cefixime against E. coli and S. aureus reduced by 33.33% and 60% respectively. The MIC and MBC of cefixime plus clavulanic acid is shown in Table 4.
Table 3 MIC and MBC of Cefuroxime plus Clavulanic acid (individual and in FDC) Cefuroxime mcg/ml
Cefuroxime : Clavulanic Acid (500 : 125 mg/tablet)
Organism
MIC
MBC
MIC
MBC
Concentration Concentration of of
MIC
Concentration of
Concentration of
Tablet mcg/ml
Cefuroxime (mcg) at MIC of Tablet
Cefuroxime Clavulanic acid Clavulanic acid Tablet (mcg) at MBC (mcg) at MBC (mcg) at MIC mcg/ml of Tablet of Tablet of Tablet
S. aureus
50
25
6.25
>500
>100
>100
3
>10
K. pneumoniae
60
30
7.5
70
35
8.7
3
3
H. influenzae
80
40
10
500
250
62.5
1.5
14
E. coli
60
30
7.5
200
100
25
4
4
S. pneumoniae
0.2
0.1
0.025
> 10
>5
> 1.25
0.03
0.2
MBC
Table 4 MIC and MBC of Cefixime plus Clavulanic acid (individual and in FDC) Cefixime mcg/ml
Cefixime : Clavulanic Acid (200 : 125 mg/tablet)
Organism
MIC
MBC Concentration of
MIC
MBC
Concentration of
MIC
Concentration of
Concentration of
Tablet mcg/ml
Cefixime(ìg) at MIC of Tablet
Clavulanic Cefixime(mcg) Clavulanic Tablet acid (mcg) at at MBC of acid (ìg) at mcg/ml MBC of Tablet Tablet MIC of Tablet
S. aureus
40
8
5
40
8
5
8
>20
M. catarrhalis
0.2
0.04
0.025
0.2
0.04
0.025
0.02
0.02
H. influenzae
1
0.2
0.125
4
0.8
0.5
0.2
0.4
E. coli
2
0.4
0.25
2
0.4
0.25
0.4
0.6
0.7
0.14
0.0875
2
0.4
0.25
0.2
0.4
S. pneumoniae
MBC
Indian Medical Gazette
106
— MARCH 2015
Table 5 MIC and MBC of cefixime plus ofloxacin (individual and in FDC) Cefixime mcg/ml
Cefixime : Ofloxacin (200 : 200 mg/tablet)
Organism
MIC
MBC
MIC MBC MIC MBC
MIC
Concentration of
Concentration of
MBC
Concentration of
Concentration of
Tablet mcg/ml
Cefixime (mcg) at MIC of Tablet
Ofloxacin (mcg) at MIC of Tablet
Tablet mcg/ml
Cefixime (mcg) at MBC of Tablet
Ofloxacin (mcg) at MBC of Tablet
K. pneumonia
0.08
0.016
0.016
0.08
0.016
0.016
E. coli
0.1
0.02
0.02
0.2
0.04
0.04
0.4
S. typhi
0.05
0.01
0.01
0.07
0.014
0.014
S. pneumonia
0.6
0.12
0.12
> 5.0
> 1.0
> 1.0
The MIC of ofloxacin against K. pneumoniae reduced from 0.09 to 0.016 mcg/ml (82% reduction); against E.coli from 0.04 to 0.02 mcg/ml (50% reduction); against S. pneumoniae from 0.8 to 0.12 mcg/ml (85% reduction) in combination with cefixime. The MIC of Cefixime against E.coli reduced from 0.4 to 0.02mcg/ml (95% reduction); against S. typhi from 0.09 to 0.01 mcg/ml (90% reduction) and against S. pneumoniae from 0.2 to 0.12 mcg/ml (40% reduction) in combination with Ofloxacin. The MBC of Ofloxacin against K. pneumoniae reduced by 92% when combined with Cefixime. In combination, MBC of Ofloxacin against E. coli reduced by 50% while that of Cefixime
Ofloxacin mcg/ml
0.09
0.2
0.6
0.04
0.08
0.09
0.2
0.009
0.02
0.2
0.4
0.8
2
reduced by 93.3%. For S. typhi, there was 93% reduction in Cefixime’s MBC and 30% reduction in Ofloxacin’s MBC. The MIC and MBC of Cefixime plus Ofloxacin against different microorganisms is shown in Table 5. The MIC and MBC of Cefixime plus Azithromycin against S. typhi and S. pneumoniae is shown in Table 6. The MIC of Cefixime against S. typhi reduced from 0.09 to 0.06 mcg/ml (33.33% reduction), against S. pneumoniae from 0.2 to 0.08 mcg/ml (60% reduction) after addition of Azithromycin. The MIC of azithromycin against S. typhi reduced from 0.5 to 0.15 mcg/ml (70% reduction)
Table 6 MIC and MBC of cefixime plus azithromycin (individual and in FDC) Cefixime mcg/ml
Cefixime : Azithromycin (200 : 500 mg/tablet)
Organism
MIC
MBC
MIC
Concentra -tion of
Concentration of
Tablet mcg/ml
Cefixime (ìg) at MIC of Tablet
S. typhi
0.3
0.06
0.15
S. pneumoniae
0.4
0.08
0.2
MIC MBC
Concentration of
Concentration of
Cefixime (mcg) at MBC of Tablet
Azithromycin (mcg) at MBC of Tablet
0.4
0.08
0.2
0.09
0.2
> 5.0
> 1.0
> 2.5
0.2
0.4
MBC
Azithromycin (mcg) at Tablet MIC of mcg/ml Tablet
Azithromycin mcg/ml MIC
MBC
0.5
0.7
Indian Medical Gazette
107
— MARCH 2015
after addition of Cefixime. The MBC of Cefixime against S. typhi, reduced by 60% while that of Azithromycin by 71.43% in combination therapy.
against S. aureus, M. catarrhalis, H. influenzae and E. coli. Addition of Clavulanic acid also reduced MIC of Cefadroxil against S. aureus, K. pneumonia, H. influenzae and S. pneumoniae.
Discussion Microorganisms have developed resistance to extendedspectrum cephalosporins Cefixime and Ceftriaxone 8. Clavulanic acid is a potent inhibitor of many beta lactamases9 and is been used in clinical practice since long time in combination with Amoxycillin. Clavulanic acid progressively inhibits lactamases from multiple bacteria including E coli, K aerogenes, P mirabilis, and S aureus9. After seeing the widespread success of Amoxicillin-Clavulanic acid combination, with the rationale of preventing inhibition of lactamases from different bacteria, Clavulanic acid has been added to cephalosporins such as Cefadroxil, Cefuroxime and Cefixime. However there is no strong clinical and microbiological evidence for combination of cephalosporin plus Clavulanic acid. In the present study, we evaluated antimicrobial action of three different cephalosporins (Cefadroxil, Cefuroxime and Cefixime) alone or in combination with Clavulanic acid. Broth dilution method has been used to evaluate resistance of E. coli, P. aeruginosa, S. aureus, S. typhi and K. pneumoniae in published literature10. In this study we used broth dilution method for evaluating susceptibility of S. aureus, K pneumoniae, M catarrhalis, E coli, S typhi and S pneumonia. Addition of Clavulanic acid to Cefadroxil resulted in reduction of MIC against S. aureus, K. pneumoniae, H influenzae and S. pneumoniae by 25%, 29%, 85% and 50% respectively. The results showed that activity of Cefadroxil against these microorganisms can be improved by addition of Clavulanic acid. There was no reduction in MIC of Cefuroxime after addition of Clavulanic acid against S. aureus, K. pneumonia, H. influenzae, E. coli or S. pneumonaie. Lack of beta lactamase production by these microorganisms could be one of the possible explanations for no improvement in the susceptibility against tested microorganisms. MICs of Cefixime against S. pneumoniae reduced from 0.2 to 0.14 mcg/ml with Clavulanic acid combination. Pneumococci are frequently involved in infections of the upper as well as lower respiratory tract and may act as reservoir for bacteremia11. In this regards, Cefixime plus Clavulanic acid combination could be useful in tackling such infections. Addition of Clavulanic acid did not result in significant change in the MIC of Cefixime
Ofloxacin or Ciprofloxacin are the recommended antibiotics for cases with fully sensitive and uncomplicated typhoid fever12. However, today, multidrug-resistant typhoid fever is one of the significant public health problems in developing countries13. Emergence of multidrug resistance and decreased susceptibility in S typhi may result in suboptimal response to Ofloxacin. Azithromycin is a promising antimicrobial for use in typhoid fever 14. Azithromycin is considered as an alternative treatment for multidrug resistance typhoid fever12. The MIC of Cefixime against S. typhi reduced by 90% reduction in combination with Ofloxacin. After addition of Azithromycin, MIC of Cefixime against S. typhi and S. pneumoniae reduced from 0.09 to 0.06 mcg/ml and 0.2 to 0.08 mcg/ml respectively. The MIC of Azithromycin against S. typhi reduced by 70% after addition of Cefixime. Cefixime and Azithromycin combination resulted in reduced MIC against S. typhi for both the agents indicating their synergistic action against S. typhi. The MIC of Cefixime against E.coli and S. pneumonia reduced by 95%, and 40% respectively in combination with Ofloxacin. Cefixime was also found to be more potent against S. pneumoniae when used in combination with Azithromycin. The MICs of Cefixime against E. coli, S. typhi and S. pneumonia reduced in combination with Ofloxacin. The MICs of Ofloxacin also reduced significantly against K. pneumoniae, E. coli and S. pneumoniae. Conclusion Few antimicrobial introductions on one hand and steadily rising antibiotic resistance on the other demands judicious use of available options and preparing novel fixed dose combinations to deal with the current scenario. The findings of this study conclude that addition of Clavulanic acid, a time tested beta lactamase inhibitor increases antimicrobial activity of Cefadroxil. Cefixime also work better against S. pneumoniae in combination with Clavulanic acid. Cefixime and Azithromycin combination reduces MIC of both agents against S. typhi, indicating their synergistic action in typhoid fever. Substantial reduction in MIC of ofloxacin is seen when combined with Cefixime against K. pneumoniae, E.coli and S. pneumoniae. Similarly, MIC of Cefixime
Indian Medical Gazette
108
against E.coli, Salmonella and Strep pneumoniae is reduced when combined with Ofloxacin. Fixed dose combinations of Cefadroxil plus Clavulanic acid, Cefixime plus Clavulanic acid, Cefixime plus Ofloxacin and Cefixime plus Azithromycin could be useful options in clinical practice based on their sensitivity pattern in a particular individual. References 1.
Moellering R.C. Jr. — Rationale for use of antimicrobial combinations. Am J Med. 75 (2A):4-8, 1983.
2.
Diaz J.A., Silva E., Arias M.J., Garzon M. — Comparative in vitro study of the antimicrobial activities of different commercial antibiotic products of vancomycin. BMC Clinical Pharmacology. 11:9, 2011.
3.
Silva I.F. Jr, Filho V.C., Zacchino S.A., Lima J.C.S., Martins D.T.O. — Antimicrobial screening of some medicinal plants from Mato Grosso Cerrado. Braz J. Pharmacogn. 19 (1B):243-248, 2009.
4.
Aggarwal A., Ghosh A., Gomber S., Mitra M., Parikh A.O. — Efficacy and safety of azithromycin for uncomplicated typhoid fever: An open label noncomparative study. Indian Pediatrics. 48:553-556, 2011.
5.
Taniguchi M., Kubo I. — Ethnobotanical drug discovery based on medicine men’s trials in the African savanna: screening of east African plants for antimicrobial activity II. J Nat Prod. 56: 1539-1546, 1993.
6.
Doern G.V., Jones R.N. — Antimicrobial susceptibility testing of Haemophilus influenzae, Branhamella catarrhalis, and Neisseria gonorrhoeae. Antimicrobial
— MARCH 2015
Agents and Chemotherapy. 32;12:1747-1753, 1988. 7.
Luangtongkum T., Morishita T.Y., El-Tayeb A.B., Ison A.J., Zhang Q. — Comparison of antimicrobial susceptibility testing of Campylobacter spp. by the agar dilution and the agar disk diffusion methods. Journal of Clinical Microbiology. 45;2:590-594, 2007.
8.
Pereira R., Cole M.J., Ison C.A. — Combination therapy for gonorrhoea: in vitro synergy testing. J Antimicrob Chemother. Nov 2012 doi:10.1093/jac/ dks449
9.
Reading C., Cole M. — Clavulanic acid: a Betalactamase-inhibiting beta-lactam from Streptomyces clavuligerus. Antimicrobial Agents and Chemotherapy. 11;5:852-857, 1977.
10. Ali S.Q., Zehra A., Naqvi B.S., Shah S., Bushra R. — Resistance pattern of ciprofloxacin against different pathogens. Oman Medical Journal. 25;4: 294-298, 2010. 11. Kadioglu A., Taylor S., Iannelli F., Pozzi G., Mitchell T.J., Amdreq P.W. — Upper and lower respiratory tract infection by Streptococcus pneumoniae is affected by pneumolysin deficiency and differences in capsule type. Infect Immun. 70 (6): 2886-2890, 2002. 12. Butler T. — Treatment of typhoid fever in the 21st century: promises and shortcomings. Clin Microbiol Infect. 17: 959–996, 2011. 13. Zaki S.A., Karande S. — Multidrug-resistant typhoid fever: a review. J Infect Dev Ctries. 5 (5):324-337, 2011. 14. Bhutta Z.A. — Current concepts in the diagnosis and treatment of typhoid fever. BMJ. 333:78-82, 2005.
