Cephalosporins represent a group of antibiotics derived from cephalosporin-C. Like penicillins, they contain a beta-lactam ring, which is responsible for the effectiveness of these drugs against bacteria. Cephalosporins are generally well tolerated and cause fewer side effects than other antibiotics.
What are cephalosporins?
Cephalosporins represent a group of antibiotics derived from cephalosporin-C. Cephalosporins are antibiotics whose action is caused by the beta-lactam ring. There are a variety of cephalosporins. However, their basic structure is the same. As the most important structural element, they contain a beta-lactam ring. Only the atomic groups at the opposite ends of the molecule vary. Thus, there are many combinations, which also form the basis for a number of different antibiotically active drugs. Cephalosporins can be divided into six different groups based on their spectrum of activity. All active ingredients have in common that they disrupt the structure of the cell wall of bacteria. The potency of the individual cephalosporins varies and is influenced only by the different atomic groups attached to the chemical backbone of the molecule. Group 1 cephalosporins have weak activity. The only representative of this group today is cefazolin. In addition, a second group of active ingredients includes the so-called transitional cephalosporins, which are mainly used to combat the germ Haemophilus influenzae. The third group includes antibiotics that are particularly effective against anaerobic bacteria. Another group includes broad-spectrum cephalosporins. They are effective against both Gram-positive and Gram-negative bacteria. Narrow-spectrum cephalosporins are only effective against Pseudomonas aeruginosa. All five of the above groups can only be applied by infusion, as they would be destroyed if taken orally. However, there are also persistent cephalosporins that can be taken orally, thereby grouping them into a sixth group.
Pharmacologic action
The pharmacologic action of cephalosporins results from blockade of the bacterial enzyme transpeptidase by the beta-lactam ring in the molecule. Transpeptidase is responsible for building the murein layer of the bacterial cell wall. In this process, it catalyzes the combination of N-acetylglucosamine with N-acetylmuramic acid, which forms the basis for the murein layer. Upon exposure of the transpeptidase to cephalosporins, the beta-lactam ring opens, forming a bond with the active sites of the enzyme. In this process, the enzyme is inactivated and bacterial cell wall assembly ceases. However, existing cell walls are not attacked. Only the build-up of the murein layer during bacterial proliferation is disturbed. Bacterial growth is thus inhibited. The structure of the cell walls of gram-positive and gram-negative bacteria is different. Although all bacteria form murein layers in the cell wall, this layer is thinner in gram-negative bacteria. Furthermore, some bacteria produce the enzyme beta-lactamase, which destroys the beta-lactam ring of antibiotics. Thus, the individual cephalosporins develop different efficacies. For example, if the lateral atom groups can shield the beta-lactam ring well against beta-lactamase, the corresponding cephalosporin is able to fight bacteria where other antibiotics have already lost their effect.
Medical application and use
As a class of drugs, cephalosporins have a broad spectrum of activity. Although not all antibiotics in this substance group are effective against all bacteria, different cephalosporins can fight different germs. That is why these agents are widely used for bacterial infectious diseases. For application, however, it is important to know which bacteria are present. The broad-spectrum cephalosporins ceftazidime, ceftriaxone, cefotaxime or cefodizime, among others, are effective against several bacterial strains. Cefsulodin, in turn, is a narrow-spectrum cephalosporin that is active only against Pseudomonas aeruginosa. The transitional cephalosporins cefuroxime, cefotiam, or cefamandol are used for Haemophilus influenzae infection. All of the cephalosporins mentioned can only be injected, as they would be inactivated if absorbed via the digestive tract.The active ingredients cefizime, cefalexin or cefaclor, among others, can be taken orally. The most important areas of application for cephalosporins include respiratory tract infections, tonsillitis, middle ear infections, urinary tract infections or skin infections. These agents are also frequently used for Lyme disease and meningitis. However, all known cephalosporins are ineffective against enterococci because they have primary resistance to this class of agents.
Risks and side effects
In general, cephalosporins are well tolerated. Unlike other antibiotics, side effects rarely occur. Furthermore, this class of drugs can be used without concern in pregnant women and children. Nevertheless, cephalosporins are not entirely free of side effects. For example, about ten percent of patients treated with cephalosporins complain of discomfort. The most common complaints include digestive problems such as diarrhea, nausea and vomiting. However, these gastrointestinal complaints are significantly more common with the use of other antibiotics. Pseudomembranous colitis has also been observed in isolated cases. It has not yet been investigated whether this problem also occurs with other antibiotics. Skin problems with rash and itching occur in about one percent of patients. Neurological complaints such as headaches and hematological changes are even rarer. Allergic reactions are also very rare with cephalosporins. These occur only in individuals who are also allergic to penicillin. Thus, cross-allergies between cephalosporins and penicillin are found in two to ten percent of patients. Cephalosporins should not be used in patients who have already experienced anaphylactic shock to penicillin. Orally ingested cephalosporins may decrease the effectiveness of live vaccines and contraceptive agents.