Azithromycin

Azithromycin is an antibiotic for inhibition of parasite growth with IC50 of 8.4 μM.

A Case-Control Study of Molecular Epidemiology in Relation to Azithromycin Resistance in Neisseria gonorrhoeae Isolates Collected in Amsterdam, the Netherlands, between 2008 and 2015.[Pubmed:28373191]

Antimicrob Agents Chemother. 2017 May 24;61(6). pii: AAC.02374-16.

Neisseria gonorrhoeae resistance to ceftriaxone and Azithromycin is increasing, which threatens the recommended dual therapy. We used molecular epidemiology to identify N. gonorrhoeae clusters and associations with Azithromycin resistance in Amsterdam, the Netherlands. N. gonorrhoeae isolates (n = 143) were selected from patients visiting the Amsterdam STI Outpatient Clinic from January 2008 through September 2015. We included all 69 Azithromycin-resistant isolates (MIC >/= 2.0 mg/liter) and 74 frequency-matched susceptible controls (MIC Azithromycin-resistant isolates had C2611T mutations in 23S rRNA (n = 62, 89.9%, P < 0.001) and were NG-MAST genogroup G2992 (P < 0.001), G5108 (P < 0.001), or G359 (P = 0.02) significantly more often than susceptible isolates and were more often part of NG-MLVA clusters (P < 0.001). Two resistant isolates (2.9%) had A2059G mutations, and five (7.3%) had wild-type 23S rRNA. No association between mtrR mutations and Azithromycin resistance was found. Twenty-four isolates, including 10 Azithromycin-resistant isolates, showed reduced susceptibility to extended-spectrum cephalosporins. Of these, five contained a penA mosaic gene. Four of the five NG-MLVA clusters contained resistant and susceptible isolates. Two clusters consisting mainly of resistant isolates included strains from men who have sex with men and from heterosexual males and females. The co-occurrence of resistant and susceptible strains in NG-MLVA clusters and the frequent occurrence of resistant strains outside of clusters suggest that Azithromycin resistance develops independently from the background genome.

A Waterborne Outbreak of Shigella sonnei with Resistance to Azithromycin and Third-Generation Cephalosporins in China in 2015.[Pubmed:28373192]

Antimicrob Agents Chemother. 2017 May 24;61(6). pii: AAC.00308-17.

Here, we report for the first time a waterborne outbreak of Shigella sonnei in China in 2015. Eleven multidrug-resistant (MDR) S. sonnei isolates were recovered, showing high resistance to Azithromycin and third-generation cephalosporins in particular, due to an mph(A)- and blaCTX-M-14-harboring IncB/O/K/Z group transmissible plasmid of 104,285 kb in size. Our study highlights the potential prevalence of the MDR outbreak of S. sonnei in China and its further dissemination worldwide with the development of globalization.

Decreased azithromycin susceptibility of Neisseria gonorrhoeae isolates in patients recently treated with azithromycin.[Pubmed:28369420]

Clin Infect Dis. 2017 Mar 24. pii: 3084699.

Background: Increasing Azithromycin usage and resistance in Neisseria gonorrhoeae threatens current dual treatment. Because antimicrobial exposure influences resistance, we analysed the association between Azithromycin exposure and decreased susceptibility of N. gonorrhoeae. Methods: We included N. gonorrhoeae isolates of patients visiting the Amsterdam STI Clinic between 1999 and 2013 (t0), with another visit in the previous 60 days (t-1). Exposure was defined as the prescription of Azithromycin at t-1. We included one isolate per patient. Using multivariable linear regression we assessed the association between exposure and Azithromycin minimum inhibitory concentration (MIC). Whole genome sequencing (WGS) was performed to produce a phylogeny, identify multilocus sequence types (MLST), multiantigen sequence types (NG-MAST), and molecular markers of Azithromycin resistance. Results: We included 323 isolates: 212 were unexposed to Azithromycin, 14 were exposed Azithromycin MIC was 0.28 mg/L (range: <0.016-24 mg/L). Linear regression adjusted for age, ethnicity, infection site, and calendar year showed a significant association between Azithromycin exposure Azithromycin Azithromycin was significantly associated with A39T or G45D mtrR mutations (p=0.046), but not with MLST or NG-MAST molecular types. Conclusions: The results suggest that frequent Azithromycin use in populations at high risk of contracting N. gonorrhoeae induces an increase in MIC, and may result in resistance.

Differential inhibition of activity, activation and gene expression of MMP-9 in THP-1 cells by azithromycin and minocycline versus bortezomib: A comparative study.[Pubmed:28369077]

PLoS One. 2017 Apr 3;12(4):e0174853.

Gelatinase B or matrix metalloproteinase-9 (MMP-9) (EC 3.4.24.35) is increased in inflammatory processes and cancer, and is associated with disease progression. In part, this is due to MMP-9-mediated degradation of extracellular matrix, facilitating influx of leukocytes into inflamed tissues and invasion or metastasis of cancer cells. MMP-9 is produced as proMMP-9 and its propeptide is subsequently removed by other proteases to generate proteolytically active MMP-9. The significance of MMP-9 in pathologies triggered the development of specific inhibitors of this protease. However, clinical trials with synthetic inhibitors of MMPs in the fight against cancer were disappointing. Reports on active compounds which inhibit MMP-9 should be carefully examined in this regard. In a considerable set of recent publications, two antibiotics (minocycline and azythromycin) and the proteasome inhibitor bortezomib, used in cancers, were reported to inhibit MMP-9 at different stages of its expression, activation or activity. The current study was undertaken to compare and to verify the impact of these compounds on MMP-9. With exception of minocycline at high concentrations (>100 muM), the compounds did not affect processing of proMMP-9 into MMP-9, nor did they affect direct MMP-9 gelatinolytic activity. In contrast, Azithromycin specifically reduced MMP-9 mRNA and protein levels without affecting NF-kappaB in endotoxin-challenged monocytic THP-1 cells. Bortezomib, although being highly toxic, had no MMP-9-specific effects but significantly upregulated cyclooxygenase-2 (COX-2) activity and PGE2 levels. Overall, our study clarified that Azithromycin decreased the levels of MMP-9 by reduction of gene and protein expression while minocycline inhibits proteolytic activity at high concentrations.

Macrolide antibiotics inhibit 50S ribosomal subunit assembly in Bacillus subtilis and Staphylococcus aureus.[Pubmed:8540733]

Antimicrob Agents Chemother. 1995 Sep;39(9):2141-4.

Macrolide antibiotics are clinically important antibiotics which are effective inhibitors of protein biosynthesis in bacterial cells. We have recently shown that some of these compounds also inhibit 50S ribosomal subunit formation in Escherichia coli. Now we show that certain macrolides have the same effect in two gram-positive organisms, Bacillus subtilis and Staphylococcus aureus. Assembly in B. subtilis was prevented by erythromycin, clarithromycin, and Azithromycin but not by oleandomycin. 50S subunit formation in S. aureus was prevented by each of seven structurally related 14-membered macrolides but not by lincomycin or two streptogramin antibiotics. Erythromycin treatment did not stimulate the breakdown of performed 50S subunits in either organism. The formation of the 30S ribosomal subunit was also unaffected by these compounds. Assembly was also inhibited in a B. subtilis strain carrying a plasmid with the ermC gene that confers macrolide resistance by rRNA methylation. These results suggest that ribosomes contain an additional site for the inhibitory functions of macrolide antibiotics.

Pharmacokinetic and in vivo studies with azithromycin (CP-62,993), a new macrolide with an extended half-life and excellent tissue distribution.[Pubmed:2830841]

Antimicrob Agents Chemother. 1987 Dec;31(12):1948-54.

Azithromycin (CP-62,993), a new acid-stable 15-membered-ring macrolide, was well absorbed following oral administration in mice, rats, dogs, and cynomolgus monkeys. This compound exhibited a uniformly long elimination half-life and was distributed exceptionally well into all tissues. This extravascular penetration of Azithromycin was demonstrated by tissue/plasma area-under-the-curve ratios ranging from 13.6 to 137 compared with ratios for erythromycin of 3.1 to 11.6. The significance of these pharmacokinetic advantages of Azithromycin over erythromycin was shown through efficacy in a series of animal infection models. Azithromycin was orally effective in treating middle ear infections induced in gerbils by transbulla challenges with amoxicillin-resistant Haemophilus influenzae or susceptible Streptococcus pneumoniae; erythromycin failed and cefaclor was only marginally active against the H. influenzae challenge. Azithromycin was equivalent to cefaclor and erythromycin against Streptococcus pneumoniae. In mouse models, the new macrolide was 10-fold more potent than erythromycin and four other antibiotics against an anaerobic infection produced by Fusobacterium necrophorum. Similarly, Azithromycin was effective against established tissue infections induced by Salmonella enteritidis (liver and spleen) and Staphylococcus aureus (thigh muscle); erythromycin failed against both infections. The oral and subcutaneous activities of Azithromycin, erythromycin, and cefaclor were similar against acute systemic infections produced by Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus viridans, or S. aureus, whereas Azithromycin was more potent than erythromycin and cefaclor against the intracellular pathogen Listeria monocytogenes. The pharmacokinetic advantage of Azithromycin over erythromycin in half-life was clearly demonstrated in prophylactic treatment of an acute mouse model of S. aureus infection. These properties of Azithromycin strongly support the further evaluation of this new macrolide for use in community-acquired infections of skin or soft tissue and respiratory diseases.

Spectrum and mode of action of azithromycin (CP-62,993), a new 15-membered-ring macrolide with improved potency against gram-negative organisms.[Pubmed:2449865]

Antimicrob Agents Chemother. 1987 Dec;31(12):1939-47.

The macrolide antibiotic Azithromycin (CP-62,993; 9-deoxo-9a-methyl-9a-aza-9a-homoerythromycin A; also designated XZ-450 [Pliva Pharmaceuticals, Zagreb, Yugoslavia]) showed a significant improvement in potency against gram-negative organisms compared with erythromycin while retaining the classic erythromycin spectrum. It was up to four times more potent than erythromycin against Haemophilus influenzae and Neisseria gonorrhoeae and twofold more potent against Branhamella catarrhalis, Campylobacter species, and Legionella species. It had activity similar to that of erythromycin against Chlamydia spp. Azithromycin was significantly more potent versus many genera of the family Enterobacteriaceae; its MIC for 90% of strains of Escherichia, Salmonella, Shigella, and Yersinia was less than or equal to 4 micrograms/ml, compared with 16 to 128 micrograms/ml for erythromycin. Azithromycin inhibited the majority of gram-positive organisms at less than or equal to 1 micrograms/ml. It displayed cross-resistance to erythromycin-resistant Staphylococcus and Streptococcus isolates. It had moderate activity against Bacteroides fragilis and was comparable to erythromycin against other anaerobic species. Azithromycin also demonstrated improved bactericidal activity in comparison with erythromycin. The mechanism of action of Azithromycin was similar to that of erythromycin since Azithromycin competed effectively for [14C]erythromycin ribosomebinding sites.