THE EFFECT OF SUBMINIMUM INHIBITORY CONCENTRATION OF ROCEPHIN(R) ON TWO ISOLATES OF PSEUDOMONAS AERUGINOSA

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Date
1988-10
Authors
JAMIU, OLADAPO SALAMI
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Abstract
ABSTRACT THE EFFECT OF SUBMINIMUM INHIBITORY CONCENTRATION OF ROCEPHIN(R) ON TWO ISOLATES OF PSEUIOMONAS AERUGINOSA The effect of subminimum inhibitory concentration (Sub M.I.C) of Rocephin(R) (Ceftriaxone) was tested on two isolates (a clinical isolate and a wild type) of Pseudomonas aeruginosa. The concentration tested has little or no effect on the growth rate of these isolates. The M.I.C of Rocephin(R) against the clinical isolate was l80ug/ml and that agaiist the wild was 300ug/ml. The subMIC used was 7.5ug/ml for the clinical and 12.5ug/ml for the wild (which were 1/24 of the M.I.Cs). It was found that there is a strain-dependent optimum antibiotic concentration below the M.I.C for maximal filamentation. The clinical isolate showed greater filamentation with increasing antitiotic concentration up to a point (l50ug/ml) whereas the wild type showed increase in length of filament with lowering antibiotic concentration, with optimum at about 40ug/ml while being at the same time more resistant than the clinical isolate. The antibiotic untreated cells were more phagocytosed by fresh human polymorphonuclear -viiineutrophils (PMN) in the exponential phase than in the stationary phase for both isolates. Relatively, the clinical isolate was more susceptible to phagocytic uptake than the wild type in the exponential phase. However, this relative susceptibility was reversed in the stationary phase. The two isolates were moderately hydrophobic with the clinical isolate being more hydrophobic than the wild type. When the cells were treated with Rocephin(R) at a concentration of 1/24 of M.I.C, there was an increase in phagocytic uptake of both isolates at both phases of growth and the observed effect of phase of growth on relative susceptibility was maintained. The subMIC also increased cell surface hydrophobicity of both isolates, with increase in the wild type being more than that of the clinical isolate at both exponential and stationary phases of growth. However, antibiotic treatment reversed the order of relative hydrophobicity observed in the untreated cells. Serum increased cell surface hydrophobicity of both isolates at both phases of growth but the increase at the stationary phase was not as pronounced -ixas in the exponential phase. When the cells were treated with Rocephin and serum together there was a general increase in the hydrophobicity at both phases of growth, greater than when the cells were treated with either the antibiotic or serum alone. However, this combination nullified the reversal of relative hydrophobicity between the isolates observed with Rocephin(R) alone, in favour of the clinical isolate. When the ability of the isolates to adhere to surfaces was tested, the clinical isolate as found to adhere less than the wild type in the exponential phase, while in the stationary phase the clinical isolate adhere more. However, the effects of Sub M.I.C. of Rocephin(R), serum individually and the combination of the two appeared to be dependent on the cells, phase of growth and the test material.
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A thesis submitted to the Postgraduate School, Ahmadu Bello University, Zaria in partial fulfillment Of the requirements for the award of the degree of MASTER OF SCIENCE IN PHARMACEUTICAL MICROBIOLOGY
Keywords
EFFECT, SUBMINIMUM, INHIBITORY, CONCENTRATION, ROCEPHIN(R), ISOLATES, PSEUDOMONAS, AERUGINOSA
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