Vancomycin Health Dictionary

Most staphylococci (see STAPHYLOCOCCUS) have now evolved resistance to benzylpenicillin (see PENICILLIN) because of their ability to produce PENICILLINASE. Cloxacillin and ?ucloxacillin are antibiotics still e?ective against most staphylococci; at one time methicillin was used to combat resistant strains, but in hospital environments bacteria acquired immunity to this powerful drug (now withdrawn from use) and to cloxacillin. RIFAMPICIN, VANCOMYCIN, TEICOPLANIN and temocillin are still active against most penicillinase-producing gram-negative bacteria (see GRAM’S STAIN). There is, however, a growing threat to health because of the rise in the number of antibiotic-resistant bacteria, particularly in hospitals. The bacteria themselves are not more virulent than others, but the di?culty in treating them with a safe and e?ective antibiotic mean that they are more dangerous. It is likely that lapses in normal hygienic practice – such as frequent hand-washing – has resulted in an increase in MRSA disease.... methicillin-resistant staphylococcus aureus (mrsa)

The name given by Sir Alexander Fleming, in 1929, to an antibacterial substance produced by the mould Penicillium notatum. The story of penicillin is one of the most dramatic in the history of medicine, and its introduction into medicine initiated a new era in therapeutics comparable only to the introduction of ANAESTHESIA by Morton and Simpson and of ANTISEPTICS by Pasteur and Lister. The two great advantages of penicillin are that it is active against a large range of bacteria and that, even in large doses, it is non-toxic. Penicillin di?uses well into body tissues and ?uids and is excreted in the urine, but it penetrates poorly into the cerebrospinal ?uid.

Penicillin is a beta-lactam antibiotic, one of a group of drugs that also includes CEPHALOSPORINS. Drugs of this group have a four-part beta-lactam ring in their molecular structure and they act by interfering with the cell-wall growth of mutliplying bacteria.

Among the organisms to which it has been, and often still is, active are: streptococcus, pneumococcus, meningococcus, gonococcus, and the organisms responsible for syphilis and for gas gangrene (for more information on these organisms and the diseases they cause, refer to the separate dictionary entries). Most bacteria of the genus staphylococcus are now resistant because they produce an enzyme called PENICILLINASE that destroys the antibiotic. A particular problem has been the evolution of strains resistant to methicillin – a derivative originally designed to conquer the resistance problem. These bacteria, known as METHICILLINRESISTANT STAPHYLOCOCCUS AUREUS (MRSA), are an increasing problem, especially after major surgery. Some are also resistant to other antibiotics such as vancomycin.

An important side-e?ect of penicillins is hypersensitivity which causes rashes and sometimes ANAPHYLAXIS, which can be fatal.

Forms of penicillin These include the following broad groups: benzylpenicillin and phenoxymethyl-penicillin; penicillinase-resistant penicillins; broad-spectrum penicillins; antipseudomonal penicillins; and mecillinams. BENZYLPENICILLIN is given intramuscularly, and is the form that is used when a rapid action is required. PHENOXYMETHYLPENICILLIN (also called penicillin V) is given by mouth and used in treating such disorders as TONSILLITIS. AMPICILLIN, a broad-spectrum antibiotic, is another of the penicillins derived by semi-synthesis from the penicillin nucleus. It, too, is active when taken by mouth, but its special feature is that it is active against gram-negative (see GRAM’S STAIN) micro-organisms such as E. coli and the salmonellae. It has been superceded by amoxicillin to the extent that prescriptions for ampicillin written by GPs in the UK to be dispensed to children have fallen by 95 per cent in the last ten years. CARBENICILLIN, a semi-synthetic penicillin, this must be given by injection, which may be painful. Its main use is in dealing with infections due to Pseudomonas pyocanea. It is the only penicillin active against this micro-organism which can be better dealt with by certain non-penicillin antibiotics. PIPERACILLIN AND TICARCILLIN are carboxypenicillins used to treat infections caused by Pseudomonas aeruginosa and Proteus spp. FLUCLOXACILLIN, also a semi-synthetic penicillin, is active against penicillin-resistant staphylococci and has the practical advantage of being active when taken by mouth. TEMOCILLIN is another penicillinase-resistant penicillin, e?ective against most gram-negative bacteria. AMOXICILLIN is an oral semi-synthetic penicillin with the same range of action as ampicillin but less likely to cause side-effects. MECILLINAM is of value in the treatment of infections with salmonellae (see FOOD POISONING), including typhoid fever, and with E. coli (see ESCHERICHIA). It is given by injection. There is a derivative, pivmecillinam, which can be taken by mouth. TICARCILLIN is a carboxypenicillin used mainly for serious infections caused by Pseudomonas aeruginosa, though it is also active against some gram-negative bacilli. Ticarcillin is available only in combination with clarulanic acid.... penicillin

A glycopeptide antibiotic (see ANTIBIOTICS) which acts against aerobic and anaerobic gram-positive (see GRAM’S STAIN) bacteria. Like the similar drug, VANCOMYCIN, it is given in the prophylaxis and treatment of ENDOCARDITIS and other serious infections caused by gram-positive cocci, including STAPHYLOCOCCUS, which have developed resistance to other antibiotics. Its long duration of action means that it need be given only once a day. Teicoplanin can be given intramuscularly or intravenously. Its use should be carefully monitored as there is a range of adverse effects.... teicoplanin

see vancomycin.... glycopeptide antibiotics

(methicillin) n. a semisynthetic penicillin that was originally used to treat infections by penicillin-resistant staphylococci. It has been superseded for this purpose by *flucloxacillin but continues to be used to test the drug sensitivity of staphylococci. Meticillin-resistant staphylococci (MRS) can be responsible for increasing rates of infection in hospitals. Until recently, such infections have responded to *vancomycin, but strains of bacilli have emerged that are resistant to vancomycin, giving rise to infections that are very difficult to treat. See also superinfection.... meticillin

n. a genus of spherical Gram-positive bacteria formerly classified as species of *Streptococcus. They are normal inhabitants of the human and animal intestine but a few species, notably E. faecalis and E. faecium, can cause infections in humans. They are responsible for some hospital-acquired infections and have been found in teeth with persisting disease after root canal treatment. Enterococci have the ability to survive under adverse (starvation) conditions and are therefore difficult to eradicate; there is concern at the development of strains resistant to glycopeptide antibiotics, such as *vancomycin (glycopeptide-resistant enterococci, GRE).... enterococcus