Penicillin-resistant strains

Promoting Optimal Response to Therapy The results of a culture and sensitivity test take several days because time must be allowed for the bacteria to grow on the culture media However, infections are treated as soon as possible In a few instances, the primary health care provider may determine that a penicillin is the treatment of choice until the results of the culture and sensitivity tests are known. In many instances, the primary health care provider selects a broad-spectrum antibiotic (ie, an antibiotic that is effective against many types or strains of bacteria) for initial treatment because of the many penicillin-resistant strains of microorganisms. 

Cethromycin Ketolide 2008 2009 2010 RTIs including those caused by macrolide and penicillin-resistant strains... 

Because of potential toxicity, bacterial resistance, and the availability of many other effective alternatives, chloramphenicol is rarely used. It may be considered for treatment of serious rickettsial infections such as typhus and Rocky Mountain spotted fever. It is an alternative to a B-lactam antibiotic for treatment of meningococcal meningitis occurring in patients who have major hypersensitivity reactions to penicillin or bacterial meningitis caused by penicillin-resistant strains of pneumococci. The dosage is 50-100 mg/kg/d in four divided doses. 

Rifampin is used in a variety of other clinical situations. An oral dosage of 600 mg twice daily for 2 days can eliminate meningococcal carriage. Rifampin, 20 mg/kg/d for 4 days, is used as prophylaxis in contacts of children with Haemophilus influenzae type b disease. Rifampin combined with a second agent is used to eradicate staphylococcal carriage. Rifampin combination therapy is also indicated for treatment of serious staphylococcal infections such as osteomyelitis and prosthetic valve endocarditis. Rifampin has been recommended also for use in combination with ceftriaxone or vancomycin in treatment of meningitis caused by highly penicillin-resistant strains of pneumococci. 

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. 

Newer fourth-generation fluoroquinolones such as gati-floxacin, gemifloxacin, and moxifloxacin have improved activity against pneumococci, including macrolide- and penicillin-resistant strains, and are often termed the respiratory quinolones. They are indicated for acute exacerbations of chronic bronchitis, community-acquired pneumonia, and sinusitis. 

The problem of (3-lactamases became critical in 1960 when the widespread use of penicillin G led to an alarming increase of Staph, aureus infections. These problem strains had gained the lactamase enzyme and had thus gained resistance to the drug. At one point, 80 per cent of all Staph, aureus infections in hospitals were due to virulent, penicillin-resistant strains. Alarmingly, these strains were also resistant to all other available antibiotics. 

Pharyngitis, scarlet fever, erysipelas, and cellulitis caused by S. pyogenes and pneumonia caused by S. pneumoniae respond to macrolides. They are valuable alternatives for treatment of patients who have a serious allergy to penicillin. Unfortunately, macrolide-resistant strains are increasingly encountered. Penicillin-resistant strains of S. pneumoniae also are very likely to be resistant to macrolides. 

Tyrothricin > 9 is bacteriostatic in concentrations of 0-01 figlml. and less for gram-positive cocci such as pneumococci, streptococci and staphylococci. At concentrations greater than 1 g/ml. it is bactericidal and some species of organisms, e.g. pneumococcus and staphylococcus are lysed. Gramnegative bacteria are much less sensitive. Many penicillin-resistant strains of cocci are sensitive to tyrothricin Table 1.7). 

Penicillin G is the drug of choice for meningococcal disease. Patients should be treated with high doses of penicillin given intravenously (see above). The rare penicillin-resistant strains should be considered in patients who are slow to respond to treatment. Penicillin G does not eliminate the meningococcal carrier state and is ineffective for prophylaxis. 

E. faecium and non-ji-lactamase-producing penicillin-resistant strains), staphylococci (including... 

Figure 7.8 Neisseria meningitides and N. gonorrhea are the only gram negatives that are susceptible to penicillin G and other narrow spectrum penicillins. Ceftriaxone has now replaced penicillin as the drug of choice for N. gonorrhea due to the emergence of penicillin-resistant strains.

Norfloxacin (Noroxin) Same mechanism. Covers enterics, P. aeruginosa (but not other pseudomonas strains), N. gonorrhea (including penicillin resistant strains), and S. aureus. Reduce dose with renal insufficiency. Urine levels high, serum levels low, not useful for infections outside urinary tract. 

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