Penicillin-resistant pneumococci

Cefaclor, cefuroxime axetil, cefprozil, and loracarbef can be given orally. The usual dosage for adults is 10-15 mg/kg/d in two to four divided doses children should be given 20-40 mg/kg/d up to a maximum of 1 g/d. Except for cefuroxime axetil, these drugs are not predictably active against penicillin-resistant pneumococci and should be used cautiously, if at all, to treat suspected or proved pneumococcal infections. Cefaclor is more susceptible to 13-lactamase hydrolysis compared with the other agents, and its usefulness is correspondingly diminished. 

Disease that is segmental or lobar in its distribution is usually caused by Streptococcus pneumoniae (pneumococcus). Haemophilus influenzae is a rare cause in this group, although it more often leads to exacerbations of chronic bronchitis and does cause pneumonia in patients infected with HIV. Benzyl-penicillin i.v. or amoxicillin p.o. are the treatments of choice if pneumococcal pneumonia is very likely alternatively, use erythromycin/clarithromycin in a penicillin-allergic patient. Seriously ill patients are best given benzylpenicillin (to cover the pneumococcus) plus ciprofloxacin (to cover Haemophilus and atypical pathogens). Where penicillin-resistant pneumococci are prevalent, i.v. cefotaxime is a reasonable best guess choice. 

The first cases of peniciUin-resistant pneumococci were reported in the 1960s in New Guinea and Australia. Penicillin-resistant pneumococci have now been registered in all continents. The highest rate was reported in 1989 in Hungary, amounting to 57% of all clinical isolates... 

Garcia-Bustos J, Tomasz A. A biological price of antibiotic resistance major changes in the peptidoglycan structure of penicillin-resistant pneumococci. Proc Natl Acad Sci USA 1990 87(14) 5415-19. 

For community-acquired pneumonia, the bacterial causes are relatively constant, even across geographic areas and patient populations. Unfortunately, pathogen resistance to standard antimicrobials is increasing (e.g., penicillin-resistant pneumococci), necessitating... 

Structural change in PBPs (eg, methicillin-resistant Staphylococcus aureus [MRSA], penicillin-resistant pneumococci)... 

Sulfate, amorphous red powder, uv max 283 nm (E 880). Freely sol in water. Slightly sol in methanol. Pract 2 cally inso in most other organic solvents. Aq solns have a bright orange color. Effective against penicillin-resistant pneumococci and staphylococci. The toxicity is comparable to that of penicillin. 

Most streptococci (but not enterococci) are very susceptible to the drug. However, penicillin-resistant viridans streptococci and S. pneumoniae are increasingly seen. Penicillin-resistant pneumococci also are resistant to third-generation cephalosporins and are especially common in children. More than 90% of staphylococcal isolates are now resistant to penicillin G, as are most strains of S. epidermidis and many strains of gonococci. With rare exceptions, meningococci are quite sensitive to penicillin G. 

Pneumococcal isolates with a minimal inhibitory concentration for penicillin G of greater than 2 pg/mL are highly resistant. Such strains are not killed by the concentrations of penicillin G or ampicillin that can be achieved in the cerebrospinal fluid. Nafcillin would be of value in a purulent meningitis suspected to be due to staphylococci but has minimal activity against penicillin-resistant pneumococci. Cefotaxime and ceftriaxone (not listed) are the most active cephalosporins against penicillin-resistant pneumococci, and the addition of vancomycin or rifampin is recommended in the case of highly resistant strains. As mentioned above, cefopera-zone does not readily cross the blood-brain barrier. The answer is (C). 

Blumberg HM, Rimland D. Nosocomial infection with penicillin-resistant pneumococci in patients with AIDS. J Infect Dis 1989 160 725-726. 

The following is the classical example. When sensitive pneumococci were cultivated in a medium to which an extract of penicillin-resistant pneumococci had been added, a proportion of the resulting organisms were penicillin-resistant and continued so on sub-culture. The transforming factor was foimd to be a DNA, and is the active part of a bacterial gene. In this way sensitive cells can be made resistant to penicillin without ever having been in contact with that drug (Hotchkiss, 1951), and streptomycin-resistance can be induced in the same way (Hotchkiss, 1955). 

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