Arch Microbiol. 1985 Apr;141(3):260-5.
Tetracycline uptake by susceptible Escherichia coli cells.

Argast M, Beck CF.

Experiments measuring the initial uptake of commercial (3H) tetracycline exhibit two distinct kinetic phases: a rapid phase followed by a slow phase. (3H) tetracycline purified by chromatography on a Dowex 50WX2 column exhibited only monophasic rapid uptake when tested with susceptible Escherichia coli cells. Cyanide inhibited the uptake of purified (3H) tetracycline only partially while transport of proline and maltose was entirely abolished. Energy independent accumulation of tetracycline may be accounted for by binding to cellular constituents. Uptake of tetracycline--as measured by inhibition of beta-galactosidase synthesis--was strongly affected by a shift in temperature from 37 degrees C to 21 degrees C while carrier-mediated transport systems revealed only minor reductions. Taken together with the non-saturability of tetracycline uptake and the evidence for diffusion of tetracycline through phospholipid bilayers [Argast and Beck (1984) Antimicrob Agents Chemother 26:263-265] these data support the hypothesis that tetracycline enters the cytoplasm by diffusion.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3923992&dopt=Abstract antibiotics, tetracycline

itg.be

BACKGROUND: Plasmid-mediated and chromosomal-mediated resistance of Neisseria gonorrhoeae to penicillin, tetracycline, thiamphenicol, and trimethoprim-sulfamethoxazole has spread dramatically in Africa. Monitoring of antimicrobial susceptibility is a key element in the control of sexually transmitted diseases. GOAL: To document antimicrobial susceptibilities of gonococci isolated during the past 15 years in Kigali, Rwanda. STUDY DESIGN: Minimal inhibitory concentrations of recently collected gonococcal isolates of eight antimicrobials were determined. The results were compared with data collected for isolates obtained since 1986. RESULTS: In 1986, 35% of the gonococcal isolates were penicillinase-producing N gonorrhoeae. Tetracycline-resistant N gonorrhoeae appeared in 1989. The prevalence of penicillinase-producing N gonorrhoeae and tetracycline-resistant N gonorrhoeae increased significantly to 70.5% and 89.2%, respectively. Chromosomal resistance to penicillin, tetracycline, and thiamphenicol increased temporarily, then decreased significantly. Chromosomal resistance to trimethoprim-sulfamethoxazole appeared in 1988 and increased to 21.6%. All the isolates were susceptible to ceftriaxone, ciprofloxacin, spectinomycin, and kanamycin. CONCLUSIONS: This study illustrated the rapidly increasing frequencies of penicillinase-producing N gonorrhoeae and tetracycline-resistant N gonorrhoeae. Chromosomal resistance to thiamphenicol and trimethoprim-sulfamethoxazole excludes these drugs as alternative treatment. Programs for antimicrobial susceptibility surveillance of N gonorrhoeae should urgently be established in Africa.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11518873&dopt=Abstract antibiotics, tetracycline

uza.be

BACKGROUND: Despite the rapid spread of antibiotic resistance in gonococci all over Southeast Asia, there is only limited surveillance for antibiotic susceptibility in Indonesia. GOAL: This study was undertaken to determine the frequency and diversity of antimicrobial resistance in gonococcal isolates from cohorts of female commercial sex workers in Bandung and Jakarta, Indonesia, and to characterize the Tet M plasmid among the tetracycline-resistant strains N gonorrhoeae. STUDY DESIGN: The antimicrobial susceptibility of 267 strains (85 strains from Bandung and 182 from Jakarta) to penicillin, spectinomycin, tetracycline, ciprofloxacin, cefotaxime, thiamphenicol, kanamycin, azithromycin, and trimethoprim-sulfamethoxazole (TMP-SMZ) was determined by agar dilution. Typing of the Tet M plasmid in tetracycline-resistant isolates was performed by PCR. RESULTS: Prevalence of penicillin and tetracycline resistance was extremely high: 60.0% of the isolates from Bandung and 70.9% of the isolates from Jakarta were resistant to penicillin. Of these, 60.0% and 62.1%, respectively, were penicillinase-producing N gonorrhoeae (PPNG). All the isolates from Bandung and 98.4% from Jakarta were resistant to tetracycline. All tetracycline-resistant isolates from Bandung and 97.8% from Jakarta carried a PCR fragment characteristic of the "Dutch" type Tet M plasmid. One isolate from Jakarta showed chromosomal resistance to tetracycline (0.6%). Chromosomal resistance to thiamphenicol (MIC, >/=2.0 microg/ml) was significantly higher in Jakarta than in Bandung (P < 0.05). All gonococcal isolates were susceptible to kanamycin, spectinomycin, cefotaxime, ciprofloxacin, and azithromycin. CONCLUSION: Spectinomycin, fluoroquinolones, and azithromycin are still useful primary drugs for treatment of gonococcal infections in Indonesia. Continued surveillance of antimicrobial susceptibility should be part of gonorrhea control in Indonesia.

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Sex Transm Dis. 1997 Mar;24(3):142-8.
Antimicrobial susceptibilities of strains of Neisseria gonorrhoeae in Bangkok, Thailand: 1994-1995.

Knapp JS, Wongba C, Limpakarnjanarat K, Young NL, Parekh MC, Neal SW, Buatiang A, Chitwarakorn A, Mastro TD.

Division of AIDS, STD, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.

BACKGROUND AND OBJECTIVES: Failure of uncomplicated gonococcal infections acquired in the Far East to respond to doses of ciprofloxacin and ofloxacin recommended by the Centers for Disease Control and Prevention have been identified in Australia, the United Kingdom, and the United States. In the Republic of the Philippines, 54.3% of strains exhibited decreased susceptibility to fluoroquinolones; 12% of strains were resistant to ciprofloxacin. This study was undertaken to compare the antimicrobial susceptibilities of gonococcal isolates in Bangkok, Thailand, with those in the Republic of the Philippines. GOAL: To determine the frequency and diversity of antimicrobial resistance, particularly to fluoroquinolones, in gonococcal strains in Bangkok, Thailand. STUDY DESIGN: Strains of Neisseria gonorrhoeae isolated from 101 patients with uncomplicated gonorrhea in Bangkok, Thailand, in July, 1994 (46 strains) and November, 1994 to July, 1995 (55 strains), were characterized by auxotype/serovar class, antimicrobial susceptibilities, and plasmid profile. Susceptibilities were determined to penicillin G, tetracycline, ceftriaxone, cefixime, cefoxitin, ciprofloxacin, ofloxacin, norfloxacin, erythromycin, kanamycin, and thiamphenicol. RESULTS: Of 101 strains, 89.1% (90/101) were resistant to penicillin or tetracycline. Plasmid-mediated resistance to penicillin or tetracycline was identified in 33.7% (34/101) of the isolates: penicillinase-producing Neisseria gonorrhoeae (17.8%; 18/101), tetracycline-resistant Neisseria gonorrhoeae (7.9%; 8/101), and penicillinase-producing/tetracycline-resistant Neisseria gonorrhoeae (7.9%; 8/101). Most penicillinase-producing strains (96.2%; 25/26) possessed the 4.4-megadalton (Md) beta-lactamase plasmid; one strain possessed the 3.2-Md beta-lactamase plasmid. Chromosomally mediated resistance to penicillin and tetracycline was exhibited by 51.5% (52/101) of strains, and 4.0% (4/101) were tetracycline resistant. All strains were susceptible to spectinomycin. Of 21.8% (22/101) strains exhibiting decreased susceptibility to ciprofloxacin (minimal inhibitory concentration [MIC] > or = 0.125 microgram/ml), one strain (ciprofloxacin MIC, 0.5 microgram/ml; ciprofloxacin inhibition zone diameter of 23 mm) had MICs of 2.0 and 8.0 micrograms/ml for ofloxacin and norfloxacin, respectively, indicating resistance to these agents. Decreased susceptibility to ciprofloxacin was identified in strains with chromosomally mediated resistance to penicillin or tetracycline and in penicillinase-producing strains. CONCLUSIONS: In Bangkok, Thailand, gonococcal isolates exhibit resistance to penicillin, tetracycline, kanamycin, and thiamphenicol. Decreased susceptibility to fluoroquinolones is emerging in a variety of strains of N. gonorrhoeae. Thus, all gonococcal infections should be treated with antimicrobial therapies known to be active against all gonococcal strains to reduce the spread of strains exhibiting decreased susceptibilities to fluoroquinolones.

PIP: To assess the frequency and diversity of antimicrobial resistant strains of Neisseria gonorrhoeae in Thailand, endocervical or urethral strains were isolated from 101 patients at a Bangkok sexually transmitted disease clinic. Of the 101 strains, 90 (89.1%) were resistant to penicillin or tetracycline. Plasmid-mediated resistance to penicillin or tetracycline was found in 33.7% of isolates; this included penicillinase-producing N gonorrhoeae (17.8%), tetracycline-resistant N gonorrhoeae (7.9%), and penicillinase-producing/tetracycline-resistant N gonorrhoeae (7.9%). Moreover, 51.5% of all strains exhibited chromosomally mediated resistance to penicillin and tetracycline. All strains were susceptible to spectinomycin. 22 strains (21.8%) showed decreased susceptibility to ciprofloxacin, while another fifth demonstrated resistance to both fluoroquinolones and norfloxacin. Finally, more than 75% of strains exhibited decreased susceptibility to kanamycin and thiamphenicol. The penicillin/tetracycline resistance phenotypes identified in Bangkok were more similar to those of isolates in the US than in the Philippines, where decreased susceptibility to fluoroquinolones predominates. Given evidence of antimicrobial resistance to penicillin, tetracycline, kanamycin, thiamphenicol, and fluoroquinolones in Thailand, the choice of agents for the treatment of uncomplicated gonococcal infection should be considered carefully and periodic surveillance of antimicrobial resistance is recommended to permit timely revision of treatment protocols.

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Genitourin Med. 1995 Feb;71(1):9-12.
Antimicrobial susceptibility, auxotype and plasmid content of Neisseria gonorrhoeae in northern Tanzania: emergence of high level plasmid mediated tetracycline resistance.

West B, Changalucha J, Grosskurth H, Mayaud P, Gabone RM, Ka-Gina G, Mabey D.

Department of Clinical Sciences, London School of Hygiene and Tropical Medicine, UK.

OBJECTIVE--To study the antimicrobial susceptibility, plasmid content, auxotype and serogroup of strains of Neisseria gonorrhoeae isolated from an urban population of STD clinic attenders in Northern Tanzania. METHODS--The minimum inhibitory concentrations of nine common antimicrobial agents were measured by the agar dilution method against 130 strains of Neisseria gonorrhoeae isolated in a free government STD clinic in Mwanza town. The auxotype, plasmid content and serogroup of these strains were also determined by conventional techniques. RESULTS--65 strains (50%) were penicillinase producers (PPNG), and 34 (26%) exhibited chromosomally mediated resistance to penicillin. Seven (5%) were sensitive to tetracycline; 78 (60%) showed intermediate levels of resistance, and 45 (35%) had high level plasmid mediated resistance (TRNG), all of which carried a 25.2 MDa plasmid. 79 strains (61%) showed decreased sensitivity to trimethoprim-sulphamethoxazole, and five (4%) were resistant to this agent. All isolates were fully sensitive to spectinomycin, azithromycin, cefotaxime, cefuroxime, norfloxacin and ciprofloxacin. One hundred and one strains (78%) were of type W11/111, 22 type W1, and seven cross reacting strains. The W1 strains were significantly more likely to be carrying plasmid mediated resistance to both penicillin and tetracycline. Six different auxotypes were present, the major type requiring proline. Plasmid profiles showed the presence of both the 3.2 MDa and the 4.4 MDa beta-lactamase encoding plasmids. CONCLUSION--a high proportion of gonococcal isolates remain resistant to penicillin in this region, and most isolates are now also resistant to tetracycline, with the emergence of plasmic mediated tetracycline resistance. Trimethoprim-sulphonamide sensitivity is also decreasing. The population of strains is heterogeneous, and both African and Asian beta-lactamase encoding plasmids are present.

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Sex Transm Dis. 1998 Aug;25(7):350-2.
Comparative in vitro susceptibility of a tetracycline-resistant Chlamydia trachomatis strain isolated in Toulouse (France).

Lefevre JC, Lepargneur JP.

Laboratoire de Prevention des Maladies Transmissibles Sexuellement, Faculte de Medecine Purpan, Toulouse, France.

BACKGROUND AND OBJECTIVES: We recently reported the first isolation of a tetracycline-resistant Chlamydia trachomatis strain in Toulouse from a woman treated with tetracycline. To characterize this isolate, its in vitro susceptibility was compared with those of 34 other C. trachomatis isolates recovered in Toulouse. STUDY DESIGN: The susceptibilities of C. trachomatis strains were determined in terms of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) using McCoy cells in 96-well microdilution plates, with an inoculum of 5.10(3) to 1.10(4) inclusion-forming units/ml. The antimicrobial agents tested were tetracycline, azithromycin, erythromycin, ofloxacin, and pristinamycin. RESULTS: No difference was observed between the MICs and MBCs except for the tetracycline. Tetracycline-resistant strain MIC and MBC were > 64 micrograms/ml, although < 1% of the bacterial population showed resistance. For the other isolates, the MIC of tetracycline was < or = 0.25 microgram/ml. The antibiotics other than tetracycline were active in vitro against all strains. CONCLUSIONS: These results show that the tetracycline resistance observed in Toulouse differs from the "heterotypic resistance" described previously in the United States in multiresistant C. trachomatis isolates. They confirm that the resistance we observed may be a new phenomenon.

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Am J Clin Pathol. 1978 Nov;70(5):821-5.
Aerobic and anaerobic susceptibility tests with three tetracyclines. Reassessment of the "class concept" of disk testing.

Barry AL, Draper DL, Wong MK.

Both aerobic and anaerobic susceptibility tests were performed with tetracycline, doxycycline, and minocycline, using disk diffusion and agar dilution technics. The data were examined in order to reassess the concept of testing a single disk, representative of the tetracycline class of antimicrobics. All strains that were susceptible to a tetracycline disk were predictably susceptible to the tetracycline analogs. Some strains that gave zones in the resistant or intermediate range were susceptible or moderately susceptible to doxycycline and minocycline by agar dilution methods. However, disk tests with the more active analogs were often unproductive, since most tetracycline-resistant strains gave indeterminate results with doxycycline or minocycline disks. It was concluded that the "class concept" of disk testing is still appropriate and that tests with tetracycline disks predict susceptibility to the other tetracycline analogs reasonably well.

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J Vet Pharmacol Ther. 1990 Mar;13(1):49-58.
Chlortetracycline in swine--bioavailability and pharmacokinetics in fasted and fed pigs.

Kilroy CR, Hall WF, Bane DP, Bevill RF, Koritz GD.

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Illinois, Urbana.

Chlortetracycline hydrochloride was administered intra-arterially (11 mg/kg) and as an oral drench (33 mg/kg) to ten 21.0-31.5-kg pigs. Five of the pigs were fasted 18 h prior to dosing and five of the pigs were fed ad libitum prior to dosing. The mean volume of distribution determined by area-under-the-curve calculations for the fasted pigs (0.967 +/- 0.210 l/kg) was significantly less (P less than 0.05) than the mean volume of distribution for the fed pigs (1.39 +/- 0.31 l/kg). Mean total body clearance of the drug was also significantly less (P less than 0.05) in the fasted pigs (0.165 +/- 0.055 l/kg/h) as compared to the fed pigs (0.307 +/- 0.053 l/kg/h). The elimination constants (beta) were not found to be statistically different (P less than 0.05): 0.1811 +/- 0.0057 for the fasted pigs; 0.2260 +/- 0.0461 for the fed pigs. The bioavailability for both groups was similar; 19.12 +/- 8.3% for the fasted pigs and 17.88 +/- 5.3% for the fed pigs. In a second experiment three groups of six pigs which weighed 34.5-44.1 kg were fed a corn-soy diet ad libitum. The rations were fortified with chlortetracycline at 100, 400 or 1000 mg chlortetracycline hydrochloride/kg feed. Chlortetracycline concentrations were determined in plasma samples collected over a 6-day period. Plasma chlortetracycline concentrations reach a plateau within 24 h after initial access to the trial diets and were highly correlated with the dose of the drug consumed (r2 = 0.97).

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