Streptococcus pneumoniae resistant strains

Mabe S, Champney WS. (2005) A comparison of a new oral streptogramin XRP 2868 with qninnpristindalfopristin against antibiotic-resistant strains of Haemophilus Influenzae, Staphylococcus Aureus, and Streptococcus Pneumoniae. Curr Microbiol 51 363-366. 

Worldwide Streptococcus pneumoniae % susceptibility to penicillin is decreasing. In some countries up to two-thirds of the clinical isolates have reduced susceptibility to penicillin or are highly resistant to this drug. Moreover, the rate of resistance to other drugs commonly used for RTI including erythromycin, tetracycline and trimethoprim-sulfamethoxazole is higher in penicillin-resistant than penicillin-susceptible strains. Monitoring local or hospital resistance patterns of pneumococci is, therefore, needed. 

Nosocomial pneumonia caused by Staphylococcus aureus (methicillin-susceptible and -resistant strains), or Streptococcus pneumoniae (penicillin-susceptible strains only). 

J Garcia-Bustos, A Tomasz. A biological price of antibiotic resistance major changes in the peptidoglycan structure of penicillin-resistant strains of Streptococcus pneumoniae. Proc Natl Acad Sci (USA) 87 5414-5419, 1990. 

Some streptococci have developed a different mechanism of acquired resistance to penicillin drugs. These bacteria have altered transpeptidases (also known as penicillin-binding proteins) that no longer bind penicillin, and thus peptidoglycan synthesis is not disrupted. This mechanism of resistance is found in Streptococcus pneumoniae. Estimates of penicillin-resistant S. pneumoniae in the United States range from 25% to 66%, including strains recovered from ocular and periocular infections. Many isolates of penicillin-resistant S.pneumoniae also are resistant to the cephalosporins, macrolides, and the older fluoroquinolones. Use of alternative antibiotics such as vancomycin is necessary for infections caused by penicillin-resistant isolates. 

Methicillin-resistant strains of Staphylococcus aureus and S. epidermidis and penicillin-resistant Streptococcus pneumoniae have been isolated from ocular infections. Therefore treatment of ocular infections caused by these organisms might require use of vancomycin for resolution. Vancomycin is also recommended for empiric intra-vitreal and topical therapy in bacterial endophthalmitis and for parenteral therapy in moderate to severe preseptal cellulitis (see Table 11-1). 

Barnes DM, Whittier S, Gilligan PH, Soares S, Tomasz A, Henderson FW. Transmission of multidrug-resistant serotype 23F Streptococcus pneumoniae in group day care evidence suggesting capsular transformation of the resistant strain in vivo. J Infect Dis 1995 171(4) 890-6. 

The MLS resistance was found in four of 137 consecutive clinical isolates of Streptococcus pyogenes (47). In two, both ermB and ermTR genes were present. In the other two, these genes were not identified, suggesting a new mechanism of high-level resistance to these antibiotics. Erm genes were detected in 45% of 173 strains of Streptococcus pneumoniae isolated from surveillance studies in day-care centers in Central Italy... 

Moxifloxacin is an 8-methoxyquinolone with enhanced potency against important Gram-positive pathogens, notably Streptococcus pneumoniae (penicillin-resistant and penicillin-susceptible strains), and class activity against Gram-negative bacteria. Its activity is not affected by beta-lactamases. Moxifloxacin may therefore represent a promising alternative for treatment of respiratory tract infections (1). 

A short report demonstrated the absence of a reliable correlation between kiUing kinetics and normal laboratory tests for pristinamycin susceptibility testing of some pneumococci (42). Eight selected multiresistant clinical isolates and two reference pristinamycin-resistant Streptococcus pneumoniae strains were studied. Disk diffusion susceptibility and MICs were determined by the agar dilution method, and all clinical isolates appeared to be susceptible to pristinamycin, whereas the two reference strains were not. In contrast, time-kill experiments identified a limited bactericidal effect of pristinamycin in three clinical and both reference strains. These three strains had been classified as pristinamycin-resistant by the Vitek-II system, which uses a kinetic turbidimetric measurement of bacterial growth. Epidemiological information is hindered by the use of highly selected strains for the study. 

While many natural products have been tested against hundreds of different strains of bacteria, the most common bacteria used in susceptibility tests include Bacillus cereus, Bacillus subtillis, Chlamydia pneumonia, Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pneumoniae, Klebsiella pneumoniae, vancomycin-resistant Enterococcus (VRE), Pseudomonas aeruginosa and Helicobacter pylori [18, 19], As the amount of published data describing the in vitro, in vivo and clinical antibacterial activities of natural products is so vast it could easily fill a book (or two), this review focuses only on natural products for which there is in vitro, in vivo and some clinical antibacterial data, as well as a plausible mechanism of action. 

Answer A- Microbial resistance to fluoroquinolones is increasing, and some strains of Streptococcus pneumoniae are now resistant to ciprofloxacin. The mechanism can involve changes in the structure of topoisomerase IV, one of the targets of fluoroquinolones, which inhibit nucleic acid synthesis. Pneumococcal resistance to penicillins is also increasing via changes in penicillin-binding proteins (PBPs). The other mechanisms listed underlie microbial resistance to other antibiotics as follows sulfonamides (choice B), macrolides (choice C), extended-spectrum penicillins (choice D), and beta-lactams (choice E). 

Children are most susceptible to ear infections from antibiotic-resistant strains of Haemophilus influenzae, Staphylococcus aureus. Streptococcus pneumoniae, and Branhamella catarrhalis. The above treatment plan has been found highly effective for treating such infections. 

Two glycolipids, D-glucosyldiglyceride and D-galactosyl-D-glucosyldiglyceride, were the major components of the polar lipid fraction from the membranes of the wild type and an aminopterin-resistant strain of Streptococcus pneumonia No relationship could be established between resistance to aminopterin and either polar lipid or fatty acid composition. However, in the presence of aminopterin, the wild type synthesized a higher proportion of unsaturated fatty acid. 

Cockeran, R., 2012. Effects of clarithromycin at sub-minimum inhibitory concentrations on early ermB gene expression, metabolic activity and growth of an eim(B)-expressing macrolide-resistant strain of streptococcus pneumoniae. Open J. Respir. Dis. 02 (01), 1—8. Available from http //dx.doi.org/10.4236/ojrd.2012.21001. 

Fosfomycin is one of a few natural products containing a carbon-phosphorus (C— P) bond isolated from Streptomyces fradiae, Streptomyces viridochromogenes, and Streptomyces wedmorensis [73]. It was also isolated from Pseudomonas syringae and Pseudomonas viridiflava [74, 75], Fosfomycin is a highly effective antibiotic of low toxicity clinically utilized for the treatment of lower urinary tract infections [76] as well as methicillin-resistant [77] and vancomycin-resistant [78] strains of S. aureus. Moreover, fosfomycin is effective for the treatment of cephalosporin- and penicillin-resistant Streptococcus pneumonia [79] and ciprofloxacin-resistant E. coli [80], The antimicrobial activity of fosfomycin has been ascribed to the inactivation of UDP-GlcAAc-3-O-enolpyruvyltransferase (MurA), an essential enzyme that catalyzes the first committed step in the biosynthesis of peptidoglycan, the main component of the cell wall, by covalent alkylation of an active site cysteine [81]. 

---