In Vitro Susceptibility of Chlamydia pecorum to Macrolides, Tetracyclines, Quinolones and β‐Lactam

Abstract

The in vitro susceptibility of Chlamydia pecorum to two macrolides (clarithromycin and erythromycin), two tetracyclines (doxycycline and minocycline), two quinolones (ofloxacin and ciprofloxacin) and one beta-lactam (ampicillin) was determined. The MICs were 0.004 to 0.008 microg/ml for clarithromycin, 0.008 to 0.031 microg/ml for doxycycline and minocycline, 0.063 to 0.125 microg/ml for erythromycin, 0.25 to 0.5 microg/ml for ofloxacin and 0.25 to 1.0 microg/ml for ciprofloxacin. The MIC for ampicillin was greater than 1,024 microg/ml. The results show clarithromycin and doxycycline are the two most effective drugs against C. pecorum.

In vitro activity of chloramphenicol, florfenicol and enrofloxacin againstChlamydia pecorumisolated from koalas (Phascolarctos cinereus)

“…Additionally, C. pecorum susceptibility to chloramphenicol in vitro was similar to that of C. trachomatis isolated from humans (MIC 0.25–1.0 µg/mL; MIC 1.0 µg/mL; MIC 0.5–1.0 µg/mL), despite the lack of a standardised testing procedure for chlamydial susceptibility testing. This supports the previous observation that chlamydial patterns of antimicrobial susceptibility display consistency across chlamydial species …”

“…The C. pecorum susceptibility to enrofloxacin in this study was the same as that of C. pneumoniae isolated from western barred bandicoots (MIC 0.25-0.5 μg/mL); 34 C. psittaci isolated from turkeys (MIC 0.25 μg/mL); 35 and to the susceptibility of ruminant isolates of C. pecorum to other fluoroquinolones (ofloxacin MIC 0.25-0.5 μg/mL, ciprofloxacin MIC 0.25-1.0 μg/mL). 17 Additionally, C. pecorum susceptibility to chloramphenicol in vitro was similar to that of C. trachomatis isolated from humans (MIC 0.25-1.0 μg/mL; 22 MIC 1.0 μg/mL; 23 MIC 0.5-1.0 μg/mL), 24 despite the lack of a standardised testing procedure for chlamydial susceptibility testing. This supports the previous observation that chlamydial patterns of antimicrobial susceptibility display consistency across chlamydial species.…”

“…There are currently no internationally accepted standardised guidelines for the antimicrobial susceptibility testing of Chlamydia spp. Despite this, the results of in vitro antimicrobial susceptibility testing for different chlamydial species using different cell lines are often similar . An exception to this is macrolide susceptibility when tested using different cell lines; Chlamydia cultured in BGMK cells yield higher MIC values for macrolides than those cultured in various other cell lines .…”

“…Despite this, the results of in vitro antimicrobial susceptibility testing for different chlamydial species using different cell lines are often similar. 17,19,20 An exception to this is macrolide susceptibility when tested using different cell lines; Chlamydia cultured in BGMK cells yield higher MIC values for macrolides than those cultured in various other cell lines. 19 This was not the case for fluoroquinolones and the results of this study indicate it is unlikely to be the case with chloramphenicol or florfenicol, as susceptibilities to these drugs were similar to those previously published using other cell lines.…”

Population pharmacokinetics of doxycycline in the tears and plasma of northern elephant seals (Mirounga angustirostris) following oral drug administration

“…6,23,24 The MIC of doxycycline for various bacteria (including human isolates) is 0.06 to 2 µg/mL for Mycoplasma mycoides, 25 0.12 to 0.5 µg/mL for Staphylococcus aureus, 26,27 0.1 µg/mL for Bacillus anthracis, 28 0.016 to 0.5 µg/mL for Streptococcus pneumoniae, 29 and 0.008 to 0.031 µg/mL for Chlamydia pecorum. 30 Although doxycycline efficacy was not assessed in the present study, it can be estimated on the basis of the AUC:MIC ratio. As tetracyclines have both time-dependent and concentration-dependent pharmacodynamics, multiple studies 31,32 have determined that the AUC:MIC ratio is the best predictor of efficacy for tetracyclines.…”