In vitro activity of clavulanic acid, amoxicillin, and ticarcillin against Chlamydia trachomatis

Deconstructing the Chlamydial Cell Wall

The evolutionary separated Gram-negative Chlamydiales show a biphasic life cycle and replicate exclusively within eukaryotic host cells. Members of the genus Chlamydia are responsible for many acute and chronic diseases in humans, and Chlamydia-related bacteria are emerging pathogens. We revisit past efforts to detect cell wall material in Chlamydia and Chlamydia-related bacteria in the context of recent breakthroughs in elucidating the underlying cellular and molecular mechanisms of the chlamydial cell wall biosynthesis. In this review, we also discuss the role of cell wall biosynthesis in chlamydial FtsZ-independent cell division and immune modulation. In the past, penicillin susceptibility of an invisible wall was referred to as the "chlamydial anomaly." In light of new mechanistic insights, chlamydiae may now emerge as model systems to understand how a minimal and modified cell wall biosynthetic machine supports bacterial cell division and how cell wall-targeting beta-lactam antibiotics can also act bacteriostatically rather than bactericidal. On the heels of these discussions, we also delve into the effects of other cell wall antibiotics in individual chlamydial lineages.

Chlamydia muridarum enters a viable but non-infectious state in amoxicillin-treated BALB/c mice

In culture, exposure to penicillin and other stressors induce chlamydiae to enter a non-infectious but viable state termed persistence. Chlamydiae may reenter their normal developmental cycle after stressor removal. Though aberrant RB similar to those present in culture models of persistence have been observed within infected tissues, the existence of persistent chlamydiae has not been definitively demonstrated in vivo. As a result, the role of persistent organisms in pathogenesis is undefined. In order to establish an experimentally tractable model of in vivo persistence, Chlamydia muridarum vaginally-infected mice were gavaged with either water or amoxicillin (amox). Vaginal swabs were collected for chlamydial titration and RNA isolated for quantification of pre-16s rRNA. Uterine tissue was analyzed by transmission electron microscopy (TEM). Although amox-treatment reduced vaginal shedding by >99%, C. muridarum pre-16s rRNA accumulation was unchanged by treatment. These data indicate that the amox-exposed organisms were viable but not infectious. Furthermore, TEM analyses demonstrated that inclusions in amox-treated animals contained primarily large, aberrant RB, but those observed in untreated control animals were normal. Collectively, these data suggest that amoxicillin treatment induces C. muridarum to enter the persistent state in vivo. This model also represents the first experimentally tractable animal model of chlamydial persistence.

In vitro activity and in vivo efficacy of clavulanic acid against Acinetobacter baumannii

Clavulanic acid (CLA) exhibits low MICs against some Acinetobacter baumannii strains. The present study evaluates the efficacy of CLA in a murine model of A. baumannii pneumonia. For this purpose, two clinical strains, Ab11 and Ab51, were used; CLA MICs for these strains were 2 and 4 mg/liter, respectively, and the imipenem (IPM) MIC was 0.5 mg/liter for both. A pneumonia model in C57BL/6 mice was used. The CLA dosage (13 mg/kg of body weight given intraperitoneally) was chosen to reach a maximum concentration of the drug in serum similar to that in humans and a time during which the serum CLA concentration remained above the MIC equivalent to 40% of the interval between doses. Six groups (n = 15) were inoculated with Ab11 or Ab51 and were allocated to IPM or CLA therapy or to the untreated control group. In time-kill experiments, CLA was bactericidal only against Ab11 whereas IPM was bactericidal against both strains. CLA and IPM both decreased bacterial concentrations in lungs, 1.78 and 2.47 log10 CFU/g (P < or = 0.001), respectively, in the experiments with Ab11 and 2.42 and 2.28 log10 CFU/g (P < or = 0.001), respectively, with Ab51. IPM significantly increased the sterility of blood cultures over that for the controls with both strains (P < or = 0.005); CLA had the same effect with Ab51 (P < 0.005) but not with Ab11 (P = 0.07). For the first time, we suggest that CLA may be used for the treatment of experimental severe A. baumannii infections.

How, and how efficiently, can we treat Chlamydia trachomatis infections in women?

Several antichlamydial active drugs are available for both non-pregnant and pregnant women, potentially allowing effective prevention of the consequences and transmission of infection. The choice of treatment regimen not only has to consider efficacy, but also side-effects, compliance and the cost of antibiotic drugs. In recent years there have been no significant changes to the guidelines for treating Chlamydia trachomatis infection as no new antibiotic has been included. Inclusion of a new antichlamydial drug in the guidelines must be supported by suitable, randomized trials. Furthermore, how much it will be used in clinical practice will also depend on considerations of a pharmacoeconomic nature.

Controlled study of the efficacy of clavulanic acid-potentiated amoxycillin in the treatment of Chlamydia psittaci in cats

Twenty-four specific pathogen-free cats were inoculated with 3 x 10(3) infectious units of a field isolate of Chlamydia psittaci on to the corneal surface. Seven days later they were assigned randomly to three groups of eight and treated orally for 19 days with either clavulanic acid-potentiated amoxycillin, doxycycline or a placebo. Both treated groups responded rapidly, with a marked reduction in isolation rates and clinical scores which were significantly lower than in the placebo group within two and four days, respectively. After two days the group treated with potentiated amoxycillin had a significantly lower isolation score than the group treated with doxycycline. Forty days after they were infected the clinical signs recurred in five of the eight cats treated with potentiated amoxycillin, but a four-week course of potentiated amoxycillin resulted in a complete clinical recovery with no evidence of a recurrence for six months.

Effect of azithromycin plus rifampin versus amoxicillin alone on eradication and inflammation in the chronic course of Chlamydia pneumoniae pneumonitis in mice

The effects of treatment with azithromycin plus rifampin (A+R), amoxicillin (A), or placebo (P) on the chronic course of experimental Chlamydia pneumoniae pneumonitis in mice were assessed by culture, PCR, and immunocytochemistry as well as by degree of inflammation in lung tissue. Eradication of the pathogen was significantly more frequent and inflammation in tissue was significantly reduced after treatment with A+R compared to after treatment with A or P. Combination therapy with azithromycin plus rifampin showed favorable effects in the chronic course of C. pneumoniae pneumonitis.

Chlamydia trachomatis in adolescents and adults. Clinical and economic implications

The aim of this article is to provide an overview of the epidemiology, diagnosis, screening and pharmacotherapy of Chlamydia trachomatis infections in adolescents and adults, together with a critical review of economic studies published on this topic. C. trachomatis continues to produce enormous social and economic consequences despite advances in prevention, screening and treatment. Both infected men and women are at risk of developing sequelae, although women tend to have more serious complications. Several strategies are available for diagnosis and screening. In populations with a high prevalence of disease, DNA-amplification assays may be the most cost-effective approach for diagnosis and screening. Empirical treatment of all patients is also cost effective; however, it may not be feasible for all health systems. A single dose of azithromycin is the most cost-effective antimicrobial agent for treatment of C. trachomatis infection.

Randomised comparison of amoxycillin and erythromycin in treatment of genital chlamydial infection in pregnancy

Erythromycin, the standard treatment for chlamydial infection in pregnant women, commonly causes side-effects, which limits its efficacy. In a randomised, double-blind study, we compared amoxycillin with erythromycin in this setting. 210 pregnant women with Chlamydia trachomatis infection were randomly assigned 7 days' treatment with amoxycillin (500 mg three times daily) or erythromycin (500 mg four times daily). Control cultures were obtained 21 days after treatment, during late pregnancy, and from the infant within a week of birth. Treatment was judged a failure if any post-treatment culture was positive or if the patient had to stop therapy because of severe side-effects. 11 women (5.2%) were lost to follow-up. 1 (of 100) amoxycillin-treated women had to stop treatment because of severe side-effects compared with 12 (of 99) erythromycin-treated women (p = 0.002). 1 woman in the amoxycillin group had a positive culture at the third-trimester examination. No positive post-treatment culture was found in the erythromycin group. Severe gastrointestinal side-effects were more common in women who received erythromycin (31 vs 6%, p < 0.001). The overall failure rate was therefore 2% in the amoxycillin group and 12% in the erythromycin group (p = 0.005). These results suggest that amoxycillin is an acceptable alternative to erythromycin for C trachomatis infection in pregnant women.

Characteristics of murine model of genital infection with Chlamydia trachomatis and effects of therapy with tetracyclines, amoxicillin-clavulanic acid, or azithromycin

Following intravaginal inoculation of progesterone-treated outbred mice with Chlamydia trachomatis MoPn, 4 to 6 log10 inclusion-forming units were recovered in vaginal swabs for 21 days but all animals were culture negative after 28 days. Serum antibody titers were elevated and remained high for at least 70 days. Between 28 and 70 days, upper tract infection (inflammation and distension of the uterine horns, occlusion of oviducts with inflammatory exudate, pyosalpinx, and hydrosalpinx) was seen in > 80% of the animals. Mice were dosed orally, commencing at 7 days after infection, with minocycline, doxycycline, or amoxicillin-clavulanate. Further groups received azithromycin either as a single high dose or as lower once-daily doses. In addition, minocycline and amoxicillin-clavulanate were administered at 24 h after infection, and this early treatment prevented elevation of antibody titers whereas delayed therapy did not. Vaginal swabs from mice in all treatment regimens were culture negative except for 25% of mice receiving either early amoxicillin-clavulanate or low-dose azithromycin, which yielded low numbers (20 to 70 inclusion-forming units) of chlamydiae. Numbers of fertile mice in the early treatment regimens and their litter sizes were similar to those of noninfected controls, although 25% of amoxicillin-clavulanate-treated mice had unilateral hydrosalpinges. In comparison, 88% of untreated mice developed hydrosalpinges and only 25% conceived. Delayed dosing did not affect the outcome of amoxicillin-clavulanate therapy but did diminish the protective efficacy of minocycline such that 50% of treated mice had either unilateral hydrosalpinges or ovarian abscesses. Doxycycline and azithromycin were highly effective in restoring fertility. This model makes possible the study of both short- and long-term outcomes of chlamydial infection.

In Vitro Susceptibility Testing of Clinical Isolates of Chlamydia trachomatis

Penicillin class antibiotics have demonstrated varying degrees of in vivo and in vitro success when tested against Chlamydia trachomatis. The activity of ampicillin-sulbactam, an agent commonly utilized in the treatment of pelvic infections, was tested to ascertain if any antichlamydial activity is present. Up to six endocervical isolates of C. trachomatis were tested against each of five antibiotics including doxycycline, erythromycin, clindamycin, ampicillin/sulbactam, and sulbactam alone. McCoy cell monolayers were inoculated with high inclusion counts of 10,000–30,000 inclusion-forming units (IFU) per coverslip, and exposed to each antibiotic. Up to nine subsequent antibiotic free culture passes were performed to assess the viability of abnormal inclusions. Doxycycline, erythromycin, and clindamycin achieved 100% eradication of inclusions at concentrations of 4.0, 2.0, and 1.0 µg/mL. Exposure to ampicillin/sulbactam resulted in a greater than 99% reduction in the inclusion count at 32.0 µg/mL, while sulbactam by itself demonstrated considerably less activity. Abnormal inclusions were noted only in the ampicillin/sulbactam exposed cells, and these, plus all inclusions remaining following sublethal exposure to the other antibiotics, resulted in regrowth to control levels in subsequent passes. Doxycycline and erythromycin demonstrated excellent activity. Clindamycin and ampicillin/sulbactam also significantly reduced inclusion formation, and therefore may provide adequate C. trachomatis coverage in patients receiving these antibiotics for pelvic infections.

Amoxicillin/clavulanic acid. An update of its antibacterial activity, pharmacokinetic properties and therapeutic use

Clavulanic acid enhances the antibacterial spectrum of amoxicillin by rendering most beta-lactamase-producing isolates susceptible to the drug. In clinical trials amoxicillin/clavulanic acid is clinically and bacteriologically superior to amoxicillin alone and at least as effective as numerous other comparative agents, such as orally administered cephalosporins, cotrimoxazole, doxycycline and bacampicillin, in the treatment of adults and children with the most common forms of infection encountered in general practice, i.e. urinary tract infections, upper and lower respiratory tract infections, otorhinolaryngological infections, and skin and soft tissue infections. It may also provide effective treatment for uncomplicated gonorrhoea, chancroid and gynaecological infections as well as acting as a prophylactic agent against surgical infection. Thus, in general practice environments where beta-lactamase production has restricted the effectiveness of amoxicillin, the combination of clavulanic acid with amoxicillin has clearly extended the usefulness of a tried and proven first-line antibacterial agent.

In vitro activities of lomefloxacin, tetracycline, penicillin, spectinomycin, and ceftriaxone against Neisseria gonorrhoeae and Chlamydia trachomatis

In vitro lomefloxacin was highly active against 208 penicillin-susceptible and -resistant isolates of Neisseria gonorrhoeae. However, its MIC and MBC against 10 isolates of Chlamydia trachomatis were 2 and greater than 4 micrograms/ml, respectively.