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Objective To investigate the mechanism of cross resistant inducibility of ciprofloxacin and imipenem which led to cross resistance in Pseudomonas aeruginosa in vivo. Methods Cross resistant mutant strains were selected and induced with clinical isolates of P.aeruginosa PA5 susceptible to ciprofloxacin and imipenem by experiment of murine peritonitis. Mutation of DNA gyrase gene, drug uptake and membrance proteins of P.aeruginosa PA5 and its mutants resistant to ciprofloxacin and imipenem were examined. Results Both ciprofloxacin and imipenem could induce resistant strain of P.aeruginosa in experimental murine peritonitis, the cross resistance rates after ciprofloxacin and imipenem challenge were 3.8% and 0.98% respectively. The results of PCR SSCP showed that 3 of six cross resistant of P.aeruginosa strains had gyrA gene mutation. Electrophoresis of outer and inner membrane proteins did not exist any difference between cross resistant strains and their parent strain PA5. Fluorometric assay for ciprofloxacin uptake by bacterial cells indicated that the accumulation of ciprofloxacin in all cross resistant variants decreased to 1/2～1/3 compared with that of PA5. After chanllenge with CCCP, the drug uptake in cross resistance mutants increased to the same level as in PA5. Conclusions The results show that cross resistant strains of P. aeruginosa could be selected and induced in vivo. Active drug efflux is the major factor contributing to the cross resistance of P. aeruginosa to both quinolone and imipenem.
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Objective To study the relationship between the gene mutations of DNA gyrase subunit A(gyrA)and quinolone resistance in Salmonella typhi. Methods The genes of gyrA DNA of Salmonella typhi S275(a clinically isolated quinolone susceptible strain)and its spontaneous quinolone-re-sistant mutant RGl were examined in this study with polymerase chain reaction(PCR),restrictive frag-ments length polymorphism(RFLP),single strand conformational polymorphism(SSCP)and nucleotide sequencing. Results Nudeotide sequencing of gyrA in Salmonella typhi S275 revealed that the bases of 128～426 kept highly conservative as compared with those of Escherichia coli KL-16,with only 7.49%difference in the gyrA nucleotides 128～426 between the two strains.Most of the mutations were silent mutations,which contributed to 3 amino acid substitutions in gyrase(including Thr-45→His,Arg-49→Leu and Val-56→Gly),and all these substitutions were located outside the quinolone resistance determining re-gion(amino acids 67-106 of subunit A of gyrase).In comparison with Salmonella typhi S275,a single mutation was found at base 247 of gyrA of Salmonella typhi RG1,with change transferred from T to G and led to a substitution of Ser-83→Ala.The mutation might be responsible for the increase of MICs of nalidixic acid,ofloxacin and ciprofloxacin against Salmonella typhi from 2,0.06 and<0.03 to 512,2,and 1 mg/L respectively.Ser-83→A1a was also a newly discovered substitution in gyrA of Salmonella spp.The results of PCR-RFLP and SSCP were in concordance with results of nucleotide sequencing. Conclu.sions The mutation of gyrase at the 83rd amino acid maybe play a principal role in the resistance of Salmonella typhi to quinolone.
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This paper reports the changes in susceptibility of Salmonella spp. to 32 antimicrobial agents from 1959 to 1988. The clinical observation on the treatment of typhoid fever caused by drug-sensitive and resistant strains of S. typhi arc also reported. Resistant Salmonella began to appear from the year of 1986. The in vitro studies indicated that drug-resistant S. typhi were resistant to commonly anti-typhoid agents such as chloramphenicol, SMZ/TMP, ampicillin and other drugs, but were very sensitive to new quinolones and the third generation cephalosporins. The .therapeutic effects correlate well with the in vitro sensitivity tests. Typhoids caused by drug-sensitive strains responded well when treated with chloramphenicol, SMZ/TMP or ampicillin, while those caused by resistant strains only responded well to norfloxacin or its combi-nation with other drugs
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Albendazole and mebendazole were comparatively evaluated in 22 adult patients for their in vivo effects on hookworm eggs. Both drugs were given 200mg twice daily for three consecutive days. Stool specimens wore collected before treatment and during the following five days. The Stool egg count was carried out by Stolls method and each specimen was also cultured by Hara-da-Mori technique for at least eight days. The mean pre-treatment percentage of incubated hookworm eggs that developed to larvae was 75.3% in albendazole group and 68.8% in mebendazole group respectively. One day following the initiation of treatment the mean percentage was remarkably reduced to 0.25% in albeadaole group and no eggs developed to larval stage beyond day 1. 0ne day and two days following the initiation of treatment the mean percentage was 16.23% and 23.13% respectively in mebendazole group. No eggs developed to larval stage on day 3 and thereafter. Albendazole seems to have better ovicidal effect than mebendazole.Albendazole and mebendazole were also comparatively evaluated in 123 adult patients with single or mixed infections of hookworm, ascarisis, and trichuris. A single dose of 400mg was used for both drugs. 2 and 4 weeks after treatment, their stools were examined by brine flotation technique. The hookworm eggs negative conversion ratss 2 weeks after treatment were 78.8% and 26.4% respectively in albeadazole and mebendazole group; while those 4 weeks after treatment were 74.1% and 25.5% respectivley. For ascariasis, the eggs negative conversion rates were 98.0% and 92.0% respectively. For trichuriasis, the negative conversion rates were only 20.6% and 27.7% respectively
ABSTRACT
A preliminary serologic survey of TORCH infections in Chongqing was performed.Sera from 160 adults,most of them were women of child bearing age and from 100 newborn cord blood,were collected. They were tested for antibody to Toxoplasma gondii(total and IgM)by the IFA technique, cytomegalovirus (CMV) IgG and IgM by ELISA, rubella virus by latex agglutination test,and herpes simplex virus(HSV)by complement fixation (CF). The positive rates among adults for antibody to T. gondii, CMV, rubella virus and herpes simplex virus were 32.6%, 72.0%, 89.4% and 79.4% respectively; and the positive rates of cord sera were 21.4%, 78.3%,78.9% and 90.7% respectively. From these result, rubella vaccination appears indicated along with education concer-ning the dangers of and methods of avoiding T. gondii, CMV, and HSV infections.