Tability of the penicillin solution at 37uC. This may be one

Tability of the penicillin solution at 37uC. This may be one of the reasons why the decontamination efficacy of penicillin-streptomycin combination may not be as effective. Furthermore, there is a high incidence of penicillin resistance among bacteria recovered from our clinical samples. This is part of the well-known worldwide problem of rising antimicrobial resistance. For instance, by the 1950s to 1970s, a consistent prevalence of 65 to 85 of penicillinase-producing Staphylococcus aureus strains was discovered in Copenhagen and the United States. Since the introduction of penicillin in 1941, it took 15 toyears for the prevalence rates of resistance to reach 25 in the community [6]. In our microbiological surveillance, our team analysed the species of bacterial isolates from tissue and solution samples, as well as their antibiotic susceptibilities from 2008 to 2009. The kind of antibiotics tested is dependent on the type of bacteria recovered according to international guidelines and the availability of antibiotics in our hospital formulary. As such, the various bacteria are tested for susceptibilities to only specific antibiotics. In general, aminoglycosides are bactericidal and are active invitro against a wide spectrum of aerobic and facultative Gramnegative bacilli [7]. The first aminoglycoside discovered in 1943, streptomycin, currently has limited usage in clinical medicine due to widespread drug resistance [8,9]. The results of this review favoured the substitution of streptomycin with another newer aminoglycoside, amikacin. Due to the presence of the aminohydroxy-butyryl group, this prevents enzymatic modification of amikacin at multiple positions. This renders amikacin a more effective decontaminating agent as micro-organisms which develop resistance to other aminoglycosides remain susceptible to amikacin [10]. This also gives amikacin a broader spectrum than the other aminoglycosides currently in use. For instance, a study conducted in Egypt TBHQ revealed that the isolates of Gram-negative bacteria in clinical samples exhibited maximal resistance against streptomycin at 83.4 , minimal resistance against amikacin at 17.7 and intermediate resistance against the other aminoglycosides. It was also discovered that amikacin was more active against Gram-negative bacteria than the other aminoglycosides tested [11]. Apart from the types of antibiotics used, the temperature of incubation also determines the efficacy of decontamination of theTable 2. Potencies of antibiotics after subjecting them to different incubation time and temperatures.ConditionsVancomycin/Percentage of Potency 1 teststAmikacin/Percentage of Potency AN-3199 Average 104.58 97.03 106.14 1st test 102.55 107.52 61.25 75.70 2nd test 119.09 54.01 65.55 Average 113.31 57.63 70.2 -ndtest0 hour (control) 4oC at 6 hours 376C at 6 hours 46C at 24 hours102.77 99.89 100.49 105.109.27 93.57 107.doi:10.1371/journal.pone.0051605.tAntibiotic Decontamination of Homografts-SingaporeTable 3. Type of micro-organisms isolated from cardiovascular homografts from 2008 to 2012.HomograftPost-Recovery Tissue or Solution CulturePost-Antibiotic Incubation Tissue or Solution CulturePenicillin Streptomycin (February 2008 ?December 2009), n = 36 1 2 3 4 5 6 7 Negative Pseudomonas species Coagulase-negative Staphylococcus, Escherichia coli Acinetobacter species Negative # * MRSA Rhodococcus species, Staphylococcus aureus, Propionibacterium acnes Staphylococcus aureus, Propionibacterium acnes Negative *.Tability of the penicillin solution at 37uC. This may be one of the reasons why the decontamination efficacy of penicillin-streptomycin combination may not be as effective. Furthermore, there is a high incidence of penicillin resistance among bacteria recovered from our clinical samples. This is part of the well-known worldwide problem of rising antimicrobial resistance. For instance, by the 1950s to 1970s, a consistent prevalence of 65 to 85 of penicillinase-producing Staphylococcus aureus strains was discovered in Copenhagen and the United States. Since the introduction of penicillin in 1941, it took 15 toyears for the prevalence rates of resistance to reach 25 in the community [6]. In our microbiological surveillance, our team analysed the species of bacterial isolates from tissue and solution samples, as well as their antibiotic susceptibilities from 2008 to 2009. The kind of antibiotics tested is dependent on the type of bacteria recovered according to international guidelines and the availability of antibiotics in our hospital formulary. As such, the various bacteria are tested for susceptibilities to only specific antibiotics. In general, aminoglycosides are bactericidal and are active invitro against a wide spectrum of aerobic and facultative Gramnegative bacilli [7]. The first aminoglycoside discovered in 1943, streptomycin, currently has limited usage in clinical medicine due to widespread drug resistance [8,9]. The results of this review favoured the substitution of streptomycin with another newer aminoglycoside, amikacin. Due to the presence of the aminohydroxy-butyryl group, this prevents enzymatic modification of amikacin at multiple positions. This renders amikacin a more effective decontaminating agent as micro-organisms which develop resistance to other aminoglycosides remain susceptible to amikacin [10]. This also gives amikacin a broader spectrum than the other aminoglycosides currently in use. For instance, a study conducted in Egypt revealed that the isolates of Gram-negative bacteria in clinical samples exhibited maximal resistance against streptomycin at 83.4 , minimal resistance against amikacin at 17.7 and intermediate resistance against the other aminoglycosides. It was also discovered that amikacin was more active against Gram-negative bacteria than the other aminoglycosides tested [11]. Apart from the types of antibiotics used, the temperature of incubation also determines the efficacy of decontamination of theTable 2. Potencies of antibiotics after subjecting them to different incubation time and temperatures.ConditionsVancomycin/Percentage of Potency 1 teststAmikacin/Percentage of Potency Average 104.58 97.03 106.14 1st test 102.55 107.52 61.25 75.70 2nd test 119.09 54.01 65.55 Average 113.31 57.63 70.2 -ndtest0 hour (control) 4oC at 6 hours 376C at 6 hours 46C at 24 hours102.77 99.89 100.49 105.109.27 93.57 107.doi:10.1371/journal.pone.0051605.tAntibiotic Decontamination of Homografts-SingaporeTable 3. Type of micro-organisms isolated from cardiovascular homografts from 2008 to 2012.HomograftPost-Recovery Tissue or Solution CulturePost-Antibiotic Incubation Tissue or Solution CulturePenicillin Streptomycin (February 2008 ?December 2009), n = 36 1 2 3 4 5 6 7 Negative Pseudomonas species Coagulase-negative Staphylococcus, Escherichia coli Acinetobacter species Negative # * MRSA Rhodococcus species, Staphylococcus aureus, Propionibacterium acnes Staphylococcus aureus, Propionibacterium acnes Negative *.

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