Cocci, gram-negative

4 GRAM-NEGATIVE BACTERIA 4.1 Gram-negative Cocci 

There are a number of groups of Gram-negative cocci but none of these are of significance in this book. 

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Except Ps. aeruginosa. All penicillins show some degree of activity against Gram-negative cocci. 

Gram-negative cocci Non-tuberculous mycobacteria Nocardia Ceftriaxone 50 mg/mL or Ceftazidime 50 mg/mL or Fluoroquinolones 3 mg/mL Amikacin 20-40 mg/mL or Oral clarithromycin 500 mg every 12 hours Amikacin 20-40 mg/mL or Trimethoprim 16 mg/mL and sulfamethoxazole 80 mg/mL wearers as indicated... 

Rifampicin, a semisynthetic derivative of the antimicrobial agent rifamycin B obtained from Strep-tomyces mediterranei, is bactericidal for intra- and extracellular bacteria. Bacterial RNA synthesis is inhibited by binding to the beta-subunit of DNA-dependent RNA polymerase. Human polymerases are not affected. It has activity against gram-positive and gram-negative cocci, chlamydia as well as mycobacteria. It is used in combination with dapsone for leprosy. 

Rifampin is a semisynthetic derivative of rifamycin, an antibiotic produced by Streptomyces mediterranei. It is active in vitro against gram-positive and gram-negative cocci, some enteric bacteria, mycobacteria, and chlamydia. Susceptible organisms are inhibited by less than 1 mcg/mL. Resistant mutants are present in all microbial populations at... 

Gram-negative cocci Spherical or ovoid do not retain color by Gram s method Neisseria gonorrhoeae (gonococcus), Neisseria meningitidis (meningococcus)... 

Gram-negative cocci Moraxella catarrhalis Otitis pneumonia sinusitis Amoxicillin + clavulanate ampicillin + sulbactam A cephalosporin azithromycin clarithromycin doxycycline erythromycin trimethoprim-sulfamethoxazole... 

These penicillins are resistant to staphylococcal Blactamases. They are active against staphylococci and streptococci but inactive against enterococci, anaerobic bacteria, and gram-negative cocci and rods. 

Gram-negative cocci that cause infections include Neisseria gonorrhoeae, which causes gonorrhea. Aetoena gonorrhoeae initially causes hyperpurulent conjunctivitis but can quickly invade the cornea and the rest of the eye. 

Viridans group of streptococci Gram-negative cocci Endocarditis, dental caries Conjunctivitis, comeal ulcer... 

The activity of these semis)mthetic penicillins extends beyond the Gram-positive and Gram-negative cocci which are susceptible to benzylpenicillin, and includes many Gram-negative bacilli. They do not resist P-lactamases and their usefulness has reduced markedly in recent years because of the increased prevalence of organisms that produce these enzymes. 

Gram-negative rod, aerobe Gram-positive rod Gram-negative cocci, aerobic Gram-negative, micro-aerobic rod... 

Vancomycin is a glycopeptide that has bactericidal action against gram-positive bacteria and some gram-negative cocci. Vancomycin is used because of its activity against methicillin-resistant staphylococci and corynebacteria. It has thus become popular for treatment of endocarditis and sepsis caused by these organisms. 

The fight against bacterial infection is one of the great success stories of medicinal chemistry. The topic is a large one and there are terms used in this chapter which are unique to this particular field. Rather than clutter the text with explanations and definitions, Appendices 4 and 5 contain explanations of such terms as antibacterial, antibiotic, Gram-positive, Gram-negative, cocci, bacilli, streptococci, and staphylococci. 

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