Methicillin-sensitive 5. aureus

Fluoroquinolones Not approved by the United States Food and Drug Administration for use in children except for anthrax (ciprofloxacin). MRSA, methicillin-resistant 5. aureus MSSA, methicillin-sensitive 5. aureus. 

To prevent development of resistance and promote synergy, inhaled tobramycin or colistin is usually added to an oral fluoroquinolone for P. aeruginosa coverage.1,3 Methicillin-sensitive S. aureus (MSSA) may be treated with oral amoxiciUin-clavulanic acid, dicloxacillin, first- or second-generation cephalosporins, trimethoprim-sulfamethoxazole, or clindamycin, depending on sensitivity. Likewise, methiciUin-resistant S. aureus (MRSA) may be treated with oral trimethoprim-sulfamethoxazole, clindamycin, minocycline, or linezolid. H. influenzae often produces... 

The antibiotics of choice for treating methicillin-sensitive S. aureus (MSSA) infections are penicillinase-stable penicillins and first-generation cephalosporins. 

MSSA methicillin-sensitive S. aureus MRSA methicillin-resistant S. aureus NBTE nonbacterial thrombotic endocarditis... 

D. B. Rapid discrimination between methicillin-sensitive and methicillin-resistant Staphylococcus aureus by intact cell mass spectrometry J. Med. Microbiol. 2000, 49, 295-300. 

Edwards-Jones, V. Claydon, M. A. Evason, D. J. Walker, J. Fox, A. J. Gordon, D. B. Rapid discrimination between methicillin-sensitive and methicillin-resistant Staphylococcus aureus by intact cell mass spectrometry. J. Med. Microbiol. 2000, 49, 295-300. 

Another important advance has been the application of PyMS with ANNs to discriminate between methicillin-resistant and methicillin-sensitive Staphylococcus aureusIn this study DFA and HCA showed that the major source of variation between the pyrolysis mass spectra of 15 methicillin-resistant (MRSA) and 22 methicillin-sensitive Staphylococcus aureus (MSSA) strains resulted from the phage group of the bacteria, rather than from their resistance or sensitivity to methicillin. By contrast, ANNs could recognize those aspects of the pyrolysis mass spectra that differentiated MRSA and MSSA strains. These results gave the first demonstration that the combination of PyMS with ANNs could provide a rapid and accurate antibiotic-susceptibility testing technique. 

MoAb monoclonal antibody mod moderate MRSA methicillin-resistant Staphylococcus aureus MS multiple sclerosis MSS A methicillin-sensitive Staphylococcus aureus MTT monotetrazolium MTX methotrexate (chemotherapy agent)... 

MSSA means methicillin-sensitive Staphylococcus aureus. M. and E. mean Micrococcus and Escherichia, respectively. A positive control used was amoxicillin (AMOX). ND, not determined. 

Staphylococcus aureus Abscesses bacteremia cellulitis endocarditis osteomyelitis pneumonia others If methicillin-sensitive nafcillin or oxacillin If methicillin-resistant vancomycin gentamicin or rifampin 1 st-generation cephalosporin clindamycin erythromycin trimethoprim-sulfamethoxazole a penicillin + a penicillinase inhibitor... 

Modification of target sites Alteration of the target site through mutation can confer resistance as occurs with the penicillin binding proteins in methicillin-resistant aureus, or the enzyme dihydrofolate reductase, which is less sensitive to inhibition in organisms resistant to trimethoprim. 

Due to its powerful specific activity against commonly isolated community-acquired respiratory tract pathogens [33,149-158], including penicillin-sensitive and -resistant Streptococcus pneumoniae, methicillin-sensitive Staphylococcus aureus, Haemophilus spp., Moraxella catarrhalis and atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella pneumophila and Klebsiella pneumoniae and anaerobic bacteria [159-162], moxifloxacin was developed as a respiratory tract anti-infective [163-168]. 

Fourth-Generation Cephalosporins. The fourth-generation cephalosporin, cefepime, has an extended spectrum of activity against both gram-positive (e.g., methicillin-sensitive S. aureus) and gram-negative organisms (e.g.. Pseudomonas). 

Figure 8.2. The action of -lactam antibiotics on the growing cell cross wall is illustrated by the effect of methicillin (0.5 iglml) in cultures of Staphylococcus aureus 5814S (methicillin-sensitive strain) [164], (a) Control (J4hr, 2 x17600) (b) Cells treated with methicillin (14 hr, 0.5p,glml methicillin 1.1 x 17600). (Electron-microscopepictures provided by Dr F. Rozgonyi, Institute of Microbiology, University Medical School, Debrecen, Hungary, to whom the authors are indebted)...

The recommended therapy for patients with left-sided IE caused by methicillin-sensitive S. aureus (MSSA) is 4 to 6 weeks of naf-cUlin or oxacillin, often combined with a short course of gentamicin (see Table 109-6). Erom in vitro studies, the combination of an aminoglycoside and peniciUinase-resistant penicillin or vancomycin enhances the activity of these drugs toward MSSA. In animal models of endocarditis, combinations of penicillin with an aminoglycoside eradicate organisms from vegetations more rapidly than penicillins... 

RW Lacy, A Catto. Action of povidone-iodine against methicillin-sensitive and -resistant cultures of Staphylococcus aureus. Postgrad Med J. 69 (suppl 3) S78-S85, 1993. 

A study in 8 healthy subjects found that rifampicin 900 mg daily for 10 days decreased the half-life and AUC0.12 of pefloxacin 400 mg twice daily by about 30%, due to a 35% increase in total plasma clearance. Despite these changes the serum pefloxacin levels still remained well above the minimal inhibitory concentrations (0.5 mg/L) for 90% of strains of methicillin-sensitive S. aureus and S. epidermis A single-dose study in 5 healthy subjects found that pefloxacin 500 mg increased the AUC of a single 600-mg dose of rifampicin by about twofold. In a further study the urinary recovery of rifampicin was increased from 15.6% of the dose to 20.1% by pefloxacin. ... 

Another study in 13 healthy subjects found that rifampicin 600 mg daily for a week increased the clearance of fleroxacin 400 mg daily by 15%. However, the fleroxacin levels remained above the MIC90 of methicillin-sensitive strains of S. aureus and S. epidermis for at least 24 hours. No special precautions would seem necessary if rifampicin is given with any of these quinolones. 

---