382
Correspondence
M.RAHMAN Department of Microbiology, King's MiU Hospital, Sutton-in-Ashfield, Notts NG17 4JL, England
References Churcher, G. M. & Human, R. P. Assessment of the in vitro activity against Bacteroides spp. of spectinomydn, metronidazole and clindamyrin.
Journal of Antimicrobial Chemotherapy 3: 363-
70 (1977). Pagan, F. S. Sensitivity of Bacteroides species to clindamycin. Journal of Antimicrobial Chemotherapy 4: 91 (1978).
Compatibility studies with various prostaglandins and antimicrobial agents Sir, Prostaglandins (PG) and PG-like compounds are widespread in nature and this fact suggests that such substances may represent a primitive recognition system. Experiments have verified that PGs and PG-like compounds can be demonstrated in various cells of living organisms in nanomole quantities. The low normal level in human cells is significantly elevated by doses used in clinical practice. During our experiments with PGs the questions arose as to whether higher levels of PG in patients have any effect upon the action of antimicrobial agents administered simultaneously to treat intercurrent infection. For this reason extensive experiments were performed in vitro in order to study the effect of PGs or PG-like substances on the susceptibility of Escherichia coli or Staphylococcus aureus to a range of antibiotics. Strains were chosen to include both sensitive and resistant organisms. In some strains resistance to antibiotics was plasmid mediated, in others resistance was chromosomally mediated. The MICs of penicillin, ampicillin, oxytetracycline, chloramphenicol, streptomycin, kanamycin, neomycin, gentamicin, tobramycin, sissomicin, amikacin, sulphadimidine, trimethoprim, nalidixic acid and primycin (Chinoin, Budapest) were determined for 8 strains of Staph. aureus and 14 strains of E. coli. The following concentrations of antibiotics were incorporated in Oxoid broth —0-01, 0-05, 0 1 , 0-5, 1, 2-5, 5, 7-5, 10, 15, 20, 40, 60, 80,100,150, and 200 ug/ml and results were read after 18 and 48 h incubation at 37°C. A similar method was used to compare the MICs of these antibiotics in the presence of 0-5, 0 1 , 0-5, 1, 5 and 10 Ug/ml of PG-F, alpha (Chinoin), PG-F,alpha (Upjohn), PG-A, (Chinoin), PG-Intermedier-9, PGIntermedier-12 and PG-Intermedier-14 (Chinoin). All strains showed similar susceptibility to the antibiotics tested regardless of the presence of high concentrations of prostaglandins.
Downloaded from http://jac.oxfordjournals.org/ at University of Arizona on April 19, 2015
these strains was determined by the agar plate dilution method. Strain 1 which did not show anyzonearound either lincomycin orclindamycin was inhibited by 45 ug/ml clindamycin. Strains 2 and 3 did not show any zone around lincomycin but both showed greatly reduced zones around clindamycin discs. Both strains were inhibited by 2-5 ug/ml clindamycin. These three strains were isolated from postoperative wounds of patients who had not received these antibiotics prophylactically or therapeutically. Operations had been performed by different surgeons in different theatres in successive weeks. The lincomycinclindamycin resistance could have been an intrinsic character of these strains. Resistance of strains 2 and 3 was moderate whilst that of strain 1 was high (MIC of clindamycin 45ng/ml). Churcher & Human (1977) were successful in inducing a high degree of resistance (MIC of clindamycin 4 to 32ug/ml) in strains of B. fragilis serially subcultured on solid media containing clindamycin. I am not aware of a report of a Bacteroides fragilis strain showing initial resistance to clindamycin at such a high degree as shown by the strain 1. A retrospective study of reports of Bacteroides isolation from this laboratory in the year 1977 revealed one other strain which showed lincomycin resistance in the disc diffusion test Resistance to clindamycin was assumed but not tested. Including this strain, a total of four resistant strains was found out of 148 isolated. Of the total 148 isolates, 24 were from vaginal or high vaginal swabs and the rest were from other parts of the body, mainly post-operative wounds and abscesses. It was interesting to note that none of the vagina] strains was found to be resistant and all of the four resistant strains were from post-operative abdominal wounds (three from appendicectomy and one from colostomy). Thus, it supports the observation by Pagan (1978) that the vaginal strains tend to be more sensitive than those derived from gut flora.
Correspondence
383
This suggests that there is probably no contra- moment they came in contact with povidone indication in giving antibiotics and PGs iodine. This happened not only with the sensitive strain but also with noxythiolin resistant simultaneously. ANDREW E. NAGY organisms (Chattopadhyay, 1977). Even at a GABOR KULCSAR 1 in 4 dilution of this antiseptic and when the KLARA N. CSATARY size of the inoculum was increased from Szoenyi Tibor Hospital, H-2601 VAC 1 -5 x 10* to 10* organisms the same result was Chinoin Factory of Drugs and Chemicalobtained. Compounds Research Directory, Absence of bacterial resistance to povidone Budapest, Hungary iodine after serial passage has already been demonstrated (Houang et al., 1976). Our results also confirm this. However, the failure Susceptibility of noxytfaiolin resistant organisms of povidone iodine to prevent post-operative sepsis after colonic surgery (Gallard et al., to povidone iodine 1977) may be explained by various factors— Sir, namely the number of organisms at the site of In-vitro sensitivity to povidone iodine of operation may be much more numerous than noxythiolin resistant organisms failed to has been used in this study. Lack of diffusion, demonstrate any bacterial resistance to this impaired absorption and the presence of widely used antiseptic. There was instantan- organic matter may interfere with its pereous complete bactericidal effect on all formance in vivo. Even if there was diffusion occasions even at 1 in 4 dilution of the original the dry powder aerosol form of povidone neat solution which is recommended for use iodine, though used in a concentrated form, as a pre-operative skin preparation. The being hygroscopic, is perhaps diluted too probable causes of failure of povidone iodine much to exert the anticipated bactericidal to prevent post operative sepsis are discussed. effect. Since it has been suggested that Three different preparations of povidone tryptone water being rich in organic matter iodine were tested—alcoholic povidone iodine, will cause a reduction of available iodine, skin preparation without alcohol and surgical therefore, we decided not to neutralize any scrub containing 1 % and 0-75 % of available residual effect of povidone iodine by the iodine respectively. Tryptone water was used addition of sodium thiosulphate in order to to double dilute them from neat (1 in 1) to compensate for this. Because we felt this way 0-06 strength (1 in 16) to a final volume of the in vitro tests will simulate in vivo conditions 1 ml. Three organisms were used—noxythiolin more. Also in view of the reported biochemical resistant Pseudomonas aeruginosa, Klebsiella disturbance associated with povidone iodine aerogenes and a sensitive Pseudomonas (Pietsch & Meakins, 1976), it will be difficult to aeruginosa (NCTC 10662), singly and as a substitute this antiseptic always in place of mixture. Initially the size of the inoculum was noxythiolin when organisms resistant to the 150,000 organisms in 0-025 ml of nutrient latter causing infection are encountered in broth. This figure was derived by taking into clinical practice. consideration that in an abdominal operation B. CHATTOPADHYAY between 10 to 12 square inches of skin is ELIZABETH THOMAS normally cleansed with antiseptic, harbouring, Public Health Laboratory and as shown by the scrub technique, approxiDepartment of Microbiology, mately between 125,000 and 150,000 aerobic Whipps Cross Hospital, organisms (Selwyn & Ellis, 1972). Later a London Ell 1NR, England larger inoculum of 1,000,000 organisms was used to see whether or not the same effect is produced. Subcultures from the tryptone References broth were made on blood agar plates at 0, Chattopadhyay, B. Noxythiolin resistant organ10, 30 min and at 18 h. Since tryptone water isms in a district general hospital. British Medical was used instead of minimal salt solution, no Journal ii: 1121-2 (1977). attempt was made to neutralize the effect of Gallard, R. B., Saunders, J. H., Mosley, J. G. & povidone iodine by the addition of sodium Darrell, J. H. Prevention of wound infection in abdominal operations by per operative antithiosulphate after 30 min contact. The results which have been summarized in Table I show quite clearly that the organisms were killed off instantaneously the
biotics or povidone iodine. Lancet ii: 1043-5 (1977). Houang, E. T., Gilmore, O. J. A., Reid, C. & Shaw, E. J. Absence of bacterial resistance to
Correspondence
M.RAHMAN Department of Microbiology, King's MiU Hospital, Sutton-in-Ashfield, Notts NG17 4JL, England
References Churcher, G. M. & Human, R. P. Assessment of the in vitro activity against Bacteroides spp. of spectinomydn, metronidazole and clindamyrin.
Journal of Antimicrobial Chemotherapy 3: 363-
70 (1977). Pagan, F. S. Sensitivity of Bacteroides species to clindamycin. Journal of Antimicrobial Chemotherapy 4: 91 (1978).
Compatibility studies with various prostaglandins and antimicrobial agents Sir, Prostaglandins (PG) and PG-like compounds are widespread in nature and this fact suggests that such substances may represent a primitive recognition system. Experiments have verified that PGs and PG-like compounds can be demonstrated in various cells of living organisms in nanomole quantities. The low normal level in human cells is significantly elevated by doses used in clinical practice. During our experiments with PGs the questions arose as to whether higher levels of PG in patients have any effect upon the action of antimicrobial agents administered simultaneously to treat intercurrent infection. For this reason extensive experiments were performed in vitro in order to study the effect of PGs or PG-like substances on the susceptibility of Escherichia coli or Staphylococcus aureus to a range of antibiotics. Strains were chosen to include both sensitive and resistant organisms. In some strains resistance to antibiotics was plasmid mediated, in others resistance was chromosomally mediated. The MICs of penicillin, ampicillin, oxytetracycline, chloramphenicol, streptomycin, kanamycin, neomycin, gentamicin, tobramycin, sissomicin, amikacin, sulphadimidine, trimethoprim, nalidixic acid and primycin (Chinoin, Budapest) were determined for 8 strains of Staph. aureus and 14 strains of E. coli. The following concentrations of antibiotics were incorporated in Oxoid broth —0-01, 0-05, 0 1 , 0-5, 1, 2-5, 5, 7-5, 10, 15, 20, 40, 60, 80,100,150, and 200 ug/ml and results were read after 18 and 48 h incubation at 37°C. A similar method was used to compare the MICs of these antibiotics in the presence of 0-5, 0 1 , 0-5, 1, 5 and 10 Ug/ml of PG-F, alpha (Chinoin), PG-F,alpha (Upjohn), PG-A, (Chinoin), PG-Intermedier-9, PGIntermedier-12 and PG-Intermedier-14 (Chinoin). All strains showed similar susceptibility to the antibiotics tested regardless of the presence of high concentrations of prostaglandins.
Downloaded from http://jac.oxfordjournals.org/ at University of Arizona on April 19, 2015
these strains was determined by the agar plate dilution method. Strain 1 which did not show anyzonearound either lincomycin orclindamycin was inhibited by 45 ug/ml clindamycin. Strains 2 and 3 did not show any zone around lincomycin but both showed greatly reduced zones around clindamycin discs. Both strains were inhibited by 2-5 ug/ml clindamycin. These three strains were isolated from postoperative wounds of patients who had not received these antibiotics prophylactically or therapeutically. Operations had been performed by different surgeons in different theatres in successive weeks. The lincomycinclindamycin resistance could have been an intrinsic character of these strains. Resistance of strains 2 and 3 was moderate whilst that of strain 1 was high (MIC of clindamycin 45ng/ml). Churcher & Human (1977) were successful in inducing a high degree of resistance (MIC of clindamycin 4 to 32ug/ml) in strains of B. fragilis serially subcultured on solid media containing clindamycin. I am not aware of a report of a Bacteroides fragilis strain showing initial resistance to clindamycin at such a high degree as shown by the strain 1. A retrospective study of reports of Bacteroides isolation from this laboratory in the year 1977 revealed one other strain which showed lincomycin resistance in the disc diffusion test Resistance to clindamycin was assumed but not tested. Including this strain, a total of four resistant strains was found out of 148 isolated. Of the total 148 isolates, 24 were from vaginal or high vaginal swabs and the rest were from other parts of the body, mainly post-operative wounds and abscesses. It was interesting to note that none of the vagina] strains was found to be resistant and all of the four resistant strains were from post-operative abdominal wounds (three from appendicectomy and one from colostomy). Thus, it supports the observation by Pagan (1978) that the vaginal strains tend to be more sensitive than those derived from gut flora.
Correspondence
383
This suggests that there is probably no contra- moment they came in contact with povidone indication in giving antibiotics and PGs iodine. This happened not only with the sensitive strain but also with noxythiolin resistant simultaneously. ANDREW E. NAGY organisms (Chattopadhyay, 1977). Even at a GABOR KULCSAR 1 in 4 dilution of this antiseptic and when the KLARA N. CSATARY size of the inoculum was increased from Szoenyi Tibor Hospital, H-2601 VAC 1 -5 x 10* to 10* organisms the same result was Chinoin Factory of Drugs and Chemicalobtained. Compounds Research Directory, Absence of bacterial resistance to povidone Budapest, Hungary iodine after serial passage has already been demonstrated (Houang et al., 1976). Our results also confirm this. However, the failure Susceptibility of noxytfaiolin resistant organisms of povidone iodine to prevent post-operative sepsis after colonic surgery (Gallard et al., to povidone iodine 1977) may be explained by various factors— Sir, namely the number of organisms at the site of In-vitro sensitivity to povidone iodine of operation may be much more numerous than noxythiolin resistant organisms failed to has been used in this study. Lack of diffusion, demonstrate any bacterial resistance to this impaired absorption and the presence of widely used antiseptic. There was instantan- organic matter may interfere with its pereous complete bactericidal effect on all formance in vivo. Even if there was diffusion occasions even at 1 in 4 dilution of the original the dry powder aerosol form of povidone neat solution which is recommended for use iodine, though used in a concentrated form, as a pre-operative skin preparation. The being hygroscopic, is perhaps diluted too probable causes of failure of povidone iodine much to exert the anticipated bactericidal to prevent post operative sepsis are discussed. effect. Since it has been suggested that Three different preparations of povidone tryptone water being rich in organic matter iodine were tested—alcoholic povidone iodine, will cause a reduction of available iodine, skin preparation without alcohol and surgical therefore, we decided not to neutralize any scrub containing 1 % and 0-75 % of available residual effect of povidone iodine by the iodine respectively. Tryptone water was used addition of sodium thiosulphate in order to to double dilute them from neat (1 in 1) to compensate for this. Because we felt this way 0-06 strength (1 in 16) to a final volume of the in vitro tests will simulate in vivo conditions 1 ml. Three organisms were used—noxythiolin more. Also in view of the reported biochemical resistant Pseudomonas aeruginosa, Klebsiella disturbance associated with povidone iodine aerogenes and a sensitive Pseudomonas (Pietsch & Meakins, 1976), it will be difficult to aeruginosa (NCTC 10662), singly and as a substitute this antiseptic always in place of mixture. Initially the size of the inoculum was noxythiolin when organisms resistant to the 150,000 organisms in 0-025 ml of nutrient latter causing infection are encountered in broth. This figure was derived by taking into clinical practice. consideration that in an abdominal operation B. CHATTOPADHYAY between 10 to 12 square inches of skin is ELIZABETH THOMAS normally cleansed with antiseptic, harbouring, Public Health Laboratory and as shown by the scrub technique, approxiDepartment of Microbiology, mately between 125,000 and 150,000 aerobic Whipps Cross Hospital, organisms (Selwyn & Ellis, 1972). Later a London Ell 1NR, England larger inoculum of 1,000,000 organisms was used to see whether or not the same effect is produced. Subcultures from the tryptone References broth were made on blood agar plates at 0, Chattopadhyay, B. Noxythiolin resistant organ10, 30 min and at 18 h. Since tryptone water isms in a district general hospital. British Medical was used instead of minimal salt solution, no Journal ii: 1121-2 (1977). attempt was made to neutralize the effect of Gallard, R. B., Saunders, J. H., Mosley, J. G. & povidone iodine by the addition of sodium Darrell, J. H. Prevention of wound infection in abdominal operations by per operative antithiosulphate after 30 min contact. The results which have been summarized in Table I show quite clearly that the organisms were killed off instantaneously the
biotics or povidone iodine. Lancet ii: 1043-5 (1977). Houang, E. T., Gilmore, O. J. A., Reid, C. & Shaw, E. J. Absence of bacterial resistance to
