J Antimicrob Chemother. 1996 Mar;37(3):483-9.
In-vitro activity of azithromycin [Zithromax] in against intracellular Helicobacter pylori.

Hulten K, Cars O, Hjelm E, Engstrand L.

Department of Infectious Diseases and Clinical Microbiology, University Hospital, Uppsala, Sweden.

We studied the effect in vitro of azithromycin [Zithromax] on the clinical strain Helicobacter pylori H:72 growing intracellularly in monolayers of HEp-2 epithelial cells. After using gentamicin to eradicate extracellular bacteria, different concentrations of azithromycin [Zithromax] were added to the infected cells and samples were taken after 0, 4, 8 and 24 h. Infected cells not exposed to antibiotic were included as controls. The MIC of azithromycin [Zithromax] to the H. pylori was 0.25 mg/L and the MBC 0.5 mg/L in a broth dilution plate count method. A bactericidal effect was observed on intracellular H. pylori, with inhibition increasing with increasing azithromycin [Zithromax] concentrations. However, extracellular concentrations of 200 x MBC were necessary to achieve intracellular killing. Our results show that azithromycin [Zithromax] is active against intracellular H. pylori suggesting that it might be possible to exploit this activity when treating infections due to the organism.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9182105&dopt=Abstract Zithromax azithromycin




J Antimicrob Chemother. 1997 May;39(5):623-30.
Delivery of azithromycin [Zithromax] to Chlamydia trachomatis-infected polarized human endometrial epithelial cells by polymorphonuclear leucocytes.

Paul TR, Knight ST, Raulston JE, Wyrick PB.

Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill 27599-7290, USA.

An in-vitro model was designed to evaluate whether polymorphonuclear leucocytes (PMN) loaded with azithromycin [Zithromax] could migrate and deliver the antibiotic in a bioactive form to chlamydia inclusions in polarized human endometrial epithelial (HEC-1B) cells infected with Chlamydia trachomatis. PMN chemotaxis through the extracellular matrix and between infected epithelial cells was readily observed if the HEC-1B cells had been infected with chlamydiae for 36 or 48 h. Inclusions in infected epithelial cells exposed to PMN loaded with azithromycin [Zithromax] were initially distinguished by deformed reticulate bodies and an excessive amount of chlamydial outer membrane vesicles. As the amount of PMN-delivered antibiotic increased, chlamydial inclusions were filled with large cell envelope 'ghosts' which were the remnants of lysed reticulate bodies. The lethal effect of azithromycin [Zithromax] was confirmed by a reduction in the viability of infectious progeny. Our results demonstrate that the damage to chlamydiae was due to transport and delivery of azithromycin [Zithromax] by PMN to infected genital epithelial cells. When infected HEC-1B cells were exposed to PMN not loaded with the antibiotic, chlamydial morphology was not obviously affected yet few viable progeny could be recovered. In this case, PMN-induced damage to host epithelial cells probably interrupted chlamydial nutrient acquisition and subsequent maturation and formation of infectious progeny.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9184362&dopt=Abstract Zithromax azithromycin




Antimicrob Agents Chemother. 1997 Aug;41(8):1673-6.
Efficacy of azithromycin [Zithromax] or clarithromycin for prophylaxis of viridans group streptococcus experimental endocarditis.

Rouse MS, Steckelberg JM, Brandt CM, Patel R, Miro JM, Wilson WR.

Infectious Diseases Research Laboratory, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.

The efficacy of azithromycin [Zithromax] or clarithromycin was compared to that of amoxicillin, clindamycin, or erythromycin for the prevention of viridans group streptococcus experimental endocarditis. Rabbits with catheter-induced aortic valve vegetations were given no antibiotics or two doses of amoxicillin at 25 mg/kg of body weight, azithromycin [Zithromax] at 10 mg/kg, clarithromycin at 10 mg/kg, clindamycin at 40 mg/kg followed by clindamycin at 20 mg/kg, or erythromycin at 10 mg/kg. Antibiotics were administered 0.5 h before and 5.5 h after intravenous infusion of 5 x 10(5) CFU of Streptococcus milleri. Forty-eight hours after bacterial inoculation, the rabbits were killed and aortic valve vegetations were aseptically removed and cultured for bacteria. Infective endocarditis occurred in 88% of untreated animals, 1% of animals receiving amoxicillin, 9% of animals receiving erythromycin, 0% of animals receiving clindamycin, 2.5% of animals receiving clarithromycin, and 1% of animals receiving azithromycin. All five regimens were more effective (P < 0.001) than no prophylaxis. Erythromycin was less effective (P < 0.05) than amoxicillin or clindamycin. Azithromycin [Zithromax] or clarithromycin was as effective as amoxicillin, clindamycin, or erythromycin for the prevention of viridans group streptococcus experimental endocarditis in this model.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9257739&dopt=Abstract Zithromax azithromycin




J Chemother. 1997 Aug;9(4):247-50.
Rapid drug susceptibility of Mycobacterium avium complex using a fluorescence quenching method.

Marone P, Bono L, Carretto E, Barbarini D, Telecco S.

Laboratory of Bacteriology and Mycology, IRCCS Policlinico S.Matteo, Pavia, Italy.

Mycobacteria Growth Indicator Tube (MGIT) is a recently introduced rapid growth detection method which uses an oxygen quenched fluorescent indicator. The present study evaluated the ability of this new method to determine the drug susceptibility of Mycobacterium avium complex (MAC). Thirty strains recovered from patients with AIDS were tested for susceptibility to clarithromycin, rifabutin, ciprofloxacin, azithromycin [Zithromax] and amikacin using MGIT. Results were compared to susceptibilities determined by the agar dilution method. The results obtained showed a 100% correlation between MGIT and the agar dilution method for rifabutin and clarithromycin. There was a 100% correlation between the two methods for azithromycin [Zithromax] against 27 strains. MGIT was well correlated with the agar dilution method for detecting resistance to clarithromycin, rifabutin and azithromycin [Zithromax] in 4 days, but the correlation was poor when susceptibilities to ciprofloxacin and amikacin were determined. This rapid method is non-radiometric, noninvasive and does not require any special instruments.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9269603&dopt=Abstract Zithromax azithromycin

popcsi.unian.it

The in vitro activity of nitazoxanide alone and in combination with azithromycin [Zithromax] and rifabutin was investigated against four clinical isolates of Cryptosporidium parvum. The susceptibility tests were performed by inoculation of the isolates on toe cell monolayers and determination of the parasite count after 48 h incubation at 37 degrees C. The culture medium was supplemented with Dulbecco's modified Eagle's medium containing serial dilutions of each agent. Antibiotic-free plates were used as controls. Experiments were performed in triplicate. Nitazoxanide showed moderate anticryptosporidial activity: it suppressed the growth of parasites by >50% at 8 mg/L. A parasite reduction of 79.8-83.9% was observed when nitazoxanide 8 mg/L was combined with azithromycin [Zithromax] 8 mg/L and rifabutin 8 mg/L. The study suggests that nitazoxanide may be active in inhibiting C. parvum growth in vitro upon combination with azithromycin [Zithromax] or rifabutin.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10747821&dopt=Abstract Zithromax azithromycin




Arzneimittelforschung. 1997 Jul;47(7):866-8.
Intracellular activity of azithromycin [Zithromax] against Mycobacterium avium complex in human macrophages.

Wildfeuer A, Haberreiter A.

Pfizer/Mack, Illertissen, Germany.

In the concentration range examined (0.5-16 micrograms/ml) the azalide antibiotic azithromycin [Zithromax] (CAS 83905-01-5, Zithromax) inhibited the growth of mycobacteria in macrophages over 7 days. The higher concentrations of azithromycin, 8 and 16 micrograms/ml, reduced the number of phagocytized bacteria in macrophages by at least 1 log unit within 4 days. The system used, macrophages from healthy volunteers, is suitable for testing the intracellular activity of drugs against the Mycobacterium avium complex.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9272246&dopt=Abstract Zithromax azithromycin




Pharmacotherapy. 1997 Sep-Oct;17(5):985-9.
Microbiologic effect of bovine cerebrospinal fluid and azithromycin [Zithromax] against Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae.

Destache CJ, Pakiz CB, Kersting K.

Creighton University School of Pharmacy and Allied Health Professions, Omaha, Nebraska 68178, USA.

Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of azithromycin [Zithromax] against reference strains of Streptococcus pneumoniae ATCC 49619, Neisseria meningitidis ATCC 13090, and Haemophilus influenzae ATCC 49247 were determined by the macrodilution broth method with and without 10% bovine cerebrospinal fluid (CSF) supplementation. The MICs and MBCs were within one to two dilutions for N. meningitidis and S. pneumoniae, and no difference was observed for H. influenzae. Time-kill curves demonstrated enhanced killing by azithromycin [Zithromax] when 10% bovine CSF was added to media for N. meningitidis. The minimum azithromycin [Zithromax] concentration for a greater than 3 log10 reduction in inoculum with bovine CSF was 0.03 microg/ml and without CSF was 0.12 microg/ml, a 3-fold difference. Killing was not significantly different for either H. influenzae nor S. pneumoniae.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9324186&dopt=Abstract Zithromax azithromycin