Shrivastava S. M, Shukla S. K, Kumar S, Chaudhary M. Microbial Efficacy Analysis of Potentox, a Fixed Dose Combination of Cefepime Amikacin with Cefepime and Amikacin Alone in a Citrobacter Braaki, Mycobacterium Smegmatis, Acinetobacter Baumanii and Neisseria mucosa. Biomed. Pharmacol. J.2009;2(1)

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Manuscript received on :February 02, 2009
Manuscript accepted on :March 10, 2009
Published online on: 12-11-2015

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Sanjay Mohan Shrivastava,* Sanjeev Kumar Shukla, Shailesh Kumar and Manu Chaudhary

Venus Medicine Research Centre, Hill Top Industrial Estate, Jharmajri EPIP, Phase I (Extn) Bhatoli Kalan, Baddi - 173 205 India.

Corresponding Author E-mail:dgmtechnical@venusremedies.com

Abstract

A newly developed extended spectrum fourth generation cephalosporins cefepime, has been shown to have good activity against both gram negative organisms. Amikacin is an aminoglycoside antibiotic used to treat different types of bacterial infections. Potentox, a Fixed Dose Combination (FDC)of cefepime and amikacin has a wider range of susceptibility to any of these drugs individually. The in vitro and in vivo effectiveness of Potentox was studied using a high inoculum of an extended spectrum b-lactamase producing Citrobacter braaki, Mycobacterium smegmatis, Acinetobacter baumanii and Neisseria mucosa strain. This study was aimed at evaluating microbial efficacy of Potentox, a FDC of cefepime and amikacin, in comparison with cefepime and amikacin alone. Efficacy was evaluated on the basis of Minimum Inhibitory Concentration (MIC), Antibiotic Susceptibility Test (AST) analysis in C. braaki, M. smegmatis, A. baumanii and Neisseria mucosa. In case of C. braaki, M. smegmatis, A. baumanii and Neisseria mucosa MIC were found to be in potentox 0.421mg/l, 0.625mg/l, 0.342mg/l and 0.423 mg/l. In cefepime alone the MIC were found to be 1.67mg/l, 0.52mg/l, 0.84mg/l and 2.67 mg/l respectively and in amikacin alone the MIC were found to be 3.34mg/l, 1.67mg/l, 2.67mg/l and 1.0mg/l respectively. Antibiotic susceptibility result are given below. In all organisms under study, potentox was found to have more bacterial inhibiting properties than cefepime and amikacin alone in vitro.

Keywords

MIC; Cefepime; Amikacin; Potentox

Introduction

Cefepime is a new broad spectrum parenteral fourth generation cephalosporin antibiotic with significant potential advantages over other broad  spectrum cephalosporins and some nontraditional β – lactam antibiotics.^{1, 2, 3} In addition to a very broad antimicrobial spectrum, cefepime appears to have low affinity for major chromosomally mediated, β – lactamases and those it less affected by the nonhydrolytic barrier mechanism of resistance in these bacteria.⁴  Its high affinity for essential penicillin binding proteins, and its zwitterionic structure.^{5, 6} Cefepime also appears to have a low propensity toward the development of resistance. Cefepime is generally active against gram negative bacteria resistance to other broad spectrum cephalosporins. Broad spectrum cephalosporins and aminoglycosides  are highly active against aerobic gram negative bacteria. However, resistance to these agents has developed during their clinical use. These in vitro advantages have been borne out in a number of in vivo  infection modal.⁷ It is a active against  a wider range of  gram positive and gram  negative aerobic organism.

Combination therapy with an aminoglycoside plus an anti pseudomonal β – lactam has commonly been recommended because this approach provides broad spectrum coverage, bactericidal activity and potential synergistic effects, and minimizes the development of resistance during treatment.⁸ Extended spectrum β – lactamases (ESBL) production is one of the main mechanisms of resistance to β – lactam antotics among the strains of family Enterobacteriaciaceae.⁹  The therapeutic choices in infections caused by such strains remain limited because of cross resistance.¹⁰

Conflicting reports have been published concerning the activities of the  broad – spectrum and fourth generation cephalosporins with an explanation of the inoculum effect.^{11, 12, 13} Cefepime and amikacin acts synergistically and has a broad spectrum in vitro activity that in enompasses a wide range of gram positive and gram negative bacteria. Cefepime has a low affinity  for chromosomally encoded  β –  lactamases.

Amikacin is an aminoglycoside antibiotic used to treat different types of bacterial infections. amikacin works by binding to the bacteria 30 S ribosome subunit, causing misreading of  m-RNA and leaving the bacterium unable to synthesize proteins vital to its growth. Amikacin is most often used for treating severe, hospital acquired infections with multi drug resistant gram negative bacteria such as  C. braaki, M. smegmatis, A. baumanii and Neisseria mucosa.

Amikacin is semi synthetic aminoglycoside antibiotic for the treatment of  some gram negative and other infection. Amikacin belong to the aminoglycosides and is active against aerobic gram negative bacilli, including pseudomonas. It dose not have activity against anaerobes, and alone they are inactive against streptococci. Aminoglycosides are usually used in the treatment of serious infections with aerobic gram negative bacilli, including  pseudomonas, complicated urinary tract infections.

Materials and Methods

Bacterial Strains

Following strains obtained from Microbial Type Collection Center of Institute of Microbial Technology, Chandigarh, India were used for the study, Citrobacter braaki (MTCC No. – 2690), Mycobacterium smegmatis (MTCC No. – 995), Acinetobacter baumanii (MTCC No. – 1425) and Neisseria mucosa (MTCC No. – 1722).

Antibiotic

Cefepime amikacin and potentox used in study were provided by manufacturer (Venus Remedies Limited, India) for the study.

Medium

Mueller Hinton (MH) broth supplemented with calcium (25 mg/l) and Magnesium (1.25 mg/l) was used for susceptibility tests. Colony counts were determined with MH agar plates.

Susceptibility  Testing

The Minimum Inhibitory Concentration (MIC) of potentox, cefepime and amikacin alone, against C. braaki, M. smegmatis, A. baumanii and N. mucosa were determined by broth microdiluction method as per the standard National Committee for Clinical Laboratory Standards.¹⁴ Overnight MH broth cultures were used to prepare inocula of 10⁵ CFU/ml. The MIC was defined as the lowest concentration of antimicrobial  agent that prevented  turbidity after 24 hours of  incubation at 37 ⁰C.

Results

MIC studies

In case of C. braaki, M. smegmatis, A. baumanii and N. mucosa MIC were found to be in potentox 0.421mg/l, 0.625mg/l, 0.342mg/l and 0.423 mg/l. In cefepime alone the MIC  were found to be 1.67mg/l, 0.52mg/l, 0.84mg/l and 2.67 mg/l respectively and  in amikacin alone the MIC were found to be 3.34mg/l, 1.67mg/l, 2.67mg/l and 1.0mg/l. (Table -1)

Table 1 : Results of  Minimal Inhibitory Concentration Studies of  potentox, a fixed dose combination of cefepime amikacin with cefepime and amikacin alone.

Susceptibility Studies

Antimicrobial Susceptibility Test of all microbial strains under study resulted in significant reduction in potentox  when compared with cefepime and amikacin alone. (Table – 2)

Table 2: Results of Antimicrobial Susceptibility Test studies of  potentox, a fixed dose combination of cefepime amikacin with cefepime and amikacin alone.

Note – Mean value ± Standered deviation value

In case of C. braaki, M. smegmatis, A. baumanii and N. mucosa AST were found of zone diameter to be 30.71mm, 23.50mm, 30.70mm and 32.70mm respectively of cefepime, for amikacin 21.70mm, 22.63mm, 17.65mm and 21.80mm respectively and for potentox 33.20mm, 29.11mm, 32.80mm and 34.15mm respectively.

Discussion

The inappropriate use of antibiotics has contributed to the emergence of resistance globally with gram negative bacilli and gram positive bacteria.¹⁵ The emerging mechanism of antibacterial resistance have compromised the effectiveness of the  β – lactam. Cefepime is a newly developed fourth generation  cephalosporins with an extended spectrum of activity against many gram positive bacteria and gram negative organism, including multi resistance gram negative bacteria. Amikacin is particularly effective when used against bacteria that are resistant to other aminoglycosides, since its chemical structure makes it less  susceptible to several inactivating enzymes. Antibiotic combinations including a β – lactam and an aminoglycoside have frequently produced an increased bactericidal effect in in vivo experimental models of aerobic gram negative bacillary infections which has generally paralleled an increased rate of  killing in vitro.¹⁶

Combination therapy with an aminoglycoside plus an anti pseudomonal β – lactam has commonly been recommended because this approach provides broad spectrum coverage, bactericidal activity and potential synergistic effects, and minimizes the development of resistance during treatment. To start with mono therapy/combination  broad spectrum empiric antibiotics are used, then switching to narrow  spectrum specific therapy as guided by microbiological result. Appropriate β – lactam antibiotics are recommended in international and German guidelines for the treatment of mono therapy and combination therapy.¹⁷ In comparison with older cephalosporins, cefepime crosses the bacterial outer membrane faster. Cefepime has advantages of rapid penetration in periplasmic space and extended spectrum of activity that include gram positive and gram negative organisms.¹⁸

The therapeutic choices in infections caused by such strains remain limited  because of cross resistance. Potentox  acts synergistically  and  has a broad spectrum in vitro activity  that encompasses a wide range of gram positive and gram negative bacteria. Susceptibility data from our study demonstrated  that  potentox  has lower MIC value than cefepime and amikacin alone, suggesting higher bactericidal activity in potentox. The in  vitro susceptibilities of ESBL  producing strains to cefepime have been found to be 52 or 90%.¹⁹ Cefepime was recommended for the treatment based on this in vitro susceptibility.²⁰ Cefepime and amikacin acts synergistically and  has a broad spectrum  in vitro  activity  that  encompasses a wide range of gram positive  and gram negative bacteria. Cefepime has a low affinity  for  chromosomally encoded β – lactamases.

In conclusion, the results by the statistical analysis of MIC and AST studies are in similar pattern for C. braaki, M. smegmatis, A. baumanii and N. mucosa Potentox has shown better bactericidal effect than cefepime and amikacin alone in organisms under study.

Reference

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