TEM-1

TEM-1

TEM-1 is a type of beta-lactamase enzyme that confers resistance to beta-lactam antibiotics such as penicillins. It is one of the most common beta-lactamases found in Gram-negative bacteria, particularly in species such as Escherichia coli and Klebsiella pneumoniae. The enzyme is named after the patient Temoniera, from whom the first strain was isolated.

Structure and Function

TEM-1 is a member of the class A beta-lactamases, which are characterized by their ability to hydrolyze the beta-lactam ring of penicillins and cephalosporins. The enzyme is encoded by the bla_TEM-1 gene, which can be located on plasmids, facilitating its spread among bacterial populations.

The structure of TEM-1 consists of a single polypeptide chain that forms a compact, globular protein. The active site of the enzyme contains a serine residue that plays a crucial role in the hydrolysis of the beta-lactam ring. This serine acts as a nucleophile, attacking the carbonyl carbon of the beta-lactam ring, leading to its opening and subsequent inactivation of the antibiotic.

Clinical Significance

The presence of TEM-1 in bacterial pathogens is a significant concern in clinical settings, as it can lead to treatment failures with commonly used antibiotics. The enzyme is capable of hydrolyzing a wide range of penicillins, including ampicillin and amoxicillin, and some early cephalosporins.

Resistance mediated by TEM-1 can be overcome by using beta-lactamase inhibitors such as clavulanic acid, sulbactam, or tazobactam, which are often combined with beta-lactam antibiotics to restore their efficacy.

Evolution and Variants

Since its discovery, numerous variants of TEM-1 have been identified, each with different substrate specificities and resistance profiles. These variants arise through point mutations in the bla_TEM-1 gene, leading to changes in the amino acid sequence of the enzyme.

Some of these variants, such as TEM-3 and TEM-10, have extended-spectrum beta-lactamase (ESBL) activity, allowing them to hydrolyze third-generation cephalosporins and aztreonam, further complicating treatment options.

Detection and Characterization

Detection of TEM-1 and its variants in clinical isolates is crucial for appropriate antibiotic therapy. Molecular techniques such as polymerase chain reaction (PCR) and sequencing are commonly used to identify the presence of the bla_TEM genes and determine the specific variant present.

Phenotypic methods, such as the use of indicator antibiotics and beta-lactamase inhibitors, can also provide information on the presence of TEM-1 and its activity.

Prevention and Control

Preventing the spread of TEM-1 and other beta-lactamases involves a combination of infection control measures, antibiotic stewardship, and surveillance. Hospitals and healthcare facilities implement strict hygiene protocols to reduce the transmission of resistant bacteria.

Antibiotic stewardship programs aim to optimize the use of antibiotics, reducing the selection pressure that drives the emergence and spread of resistant strains.

Also see

• Beta-lactamase
• Antibiotic resistance
• Extended-spectrum beta-lactamase
• Escherichia coli
• Klebsiella pneumoniae