Beta lactam Antibiotics list

Beta-Lactam Antibiotics

Beta-lactam antibiotics include penicillins, cephalosporins, carbapenems, and monobactams. Beta-lactam antibiotics have a four-member core ring structure and are bactericidal. They inhibit bacterial cell wall synthesis.

Beta-Lactam Antibiotics


 Penicillin was first used to treat a patient in Oxford, England, in 1941. It was initially effective against S. aureus in addition to streptococci, but resistance in staphylococci quickly developed. Group A Streptococcus, however, never developed resistance to penicillin. Methicillin was developed in 1961 as a penicillin derivative with efficacy against S. aureus, but this was subsequently replaced by less toxic alternatives, nafcillin and oxacillin. The name “methicillin” remains in “methicillin-susceptible S. aureus” (MSSA) and “methicillin-resistant S. aureus” (MRSA), and signifies susceptibility or resistance to beta-lactam antibiotics such as oxacillin, nafcillin, ampicillin-sulbactam, cefazolin, cefuroxime, ceftriaxone, and cefepime.


 The first cephalosporin was isolated in Oxford, England, in 1961 and the first clinically useful cephalosporin, cephalothin, was marketed in 1964. Subsequent development of multiple cephalosporins has led to their classification in “generations". Clinically important features that distinguish various cephalosporins include their activity against S. aureus (e.g., cefazolin, cefuroxime, cefepime), S. pneumonia (e.g., ceftriaxone), anaerobes (e.g., cefoxitin), and Gram-negative bacilli. All cephalosporins have activity against Gram-negative bacilli, but the number of susceptible pathogens generally increases as the generation of cephalosporin increases. The few cephalosporins (e.g., ceftazidime, cefepime) with activity against Pseudomonas are noteworthy. None of the cephalosporins had activity against MRSA until the advent of the fifth generation cephalosporins, ceftobiprole and ceftaroline.


 Carbapenems provide broad antibacterial therapy treating Gram-positive cocci, Gram-negative bacilli, and anaerobes. They are also active against most bacteria that have an extended-spectrum β-lactamase (ESBL) or an AmpC beta-lactamase (bacterial mechanisms of resistance). They are administered intravenously and include doripenem, ertapenem, imipenem-cilastatin, and meropenem. They are not active against MRSA or Stenotrophomonas maltophilia. Ertapenem is not active against Pseudomonas or Acinetobacter. Carbapenems have good penetration into many tissues, including into the central nervous system, and are valuable agents because of their broad-spectrum of activity. As with all antibiotics, resistance can emerge while on therapy and these agents should only be used when narrower spectrum antibiotics are not an option.


 The only FDA-approved monobactam to date is aztreonam, an antibiotic with a similar spectrum of activity as gentamicin and other aminoglycosides, but with significantly less toxicity. Aztreonam is effective against Gramnegative bacteria, including Pseudomonas, but has no activity against Gram-positive bacteria or anaerobes. Aztreonam is used primarily for treatment of Gram-negative infections in patients with severe penicillin or cephalosporin allergies, because nearly all patients with beta-lactam allergies can tolerate aztreonam. Aztreonam has a similar side chain as ceftazidime and should be used cautiously in patients with ceftazidime allergy. Aztreonam can be used to treat variety of infections including bacteremia, urinary tract infections, bone and joint infections, and skin and soft tissue infections. In can be used in combination with a Gram-positive antibiotic in cases requiring broad-spectrum therapy.


Aminoglycosides (e.g., amikacin, gentamicin, tobramycin) are often used in combination with beta-lactam antibiotics to treat some types of bacterial endocarditis and Gram-negative infections. Aminoglycosides have activity against nearly all Gram-negative bacilli, including Pseudomonas aeruginosa, and act synergistically with ampicillin to treat serious infections due to susceptible enterococci. Some aminoglycosides (e.g., streptomycin) are used as part of a regimen  to treat multidrug-resistant mycobacterial infections. Clinical use of aminoglycosides is largely reserved for the treatment of drug-resistant organisms because renal dysfunction and ototoxicity are significant side effects. Renal function and serum peak and trough aminoglycoside levels should be monitored frequently. Patients should be alerted to the possibility of ototoxicity, and hearing and vestibular function should be monitored unless the aminoglycoside course is expected to be very brief. Ototoxicity can affect hearing and/or vestibular function and usually begins with high-frequency sensorineural hearing loss. This may not be appreciated by the patient but can be detected on hearing tests. Vestibular toxicity may be more prevalent that auditory toxicity.

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