Beta-lactamases, (β-lactamases) are enzymes produced by bacteria that provide multi-resistance to beta-lactam antibiotics such as penicillins, cephalosporins, cephamycins, monobactams and carbapenems (ertapenem), although carbapenems are relatively resistant to beta-lactamase. Beta-lactamase provides antibiotic resistance by breaking the antibiotics' structure. These antibiotics all have a common element in their molecular structure: a four-atom ring known as a beta-lactam (β-lactam) ring. Through hydrolysis, the enzyme lactamase breaks the β-lactam ring open, deactivating the molecule's antibacterial properties.
An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics.
Aztreonam, sold under the brand name Azactam among others, is an antibiotic used primarily to treat infections caused by gram-negative bacteria such as Pseudomonas aeruginosa. This may include bone infections, endometritis, intra abdominal infections, pneumonia, urinary tract infections, and sepsis. It is given by intravenous or intramuscular injection or by inhalation.
Ceftazidime, sold under the brand name Fortaz among others, is a third-generation cephalosporin antibiotic useful for the treatment of a number of bacterial infections. Specifically it is used for joint infections, meningitis, pneumonia, sepsis, urinary tract infections, malignant otitis externa, Pseudomonas aeruginosa infection, and vibrio infection. It is given by injection into a vein, muscle, or eye.
Piperacillin is a broad-spectrum β-lactam antibiotic of the ureidopenicillin class. The chemical structure of piperacillin and other ureidopenicillins incorporates a polar side chain that enhances penetration into Gram-negative bacteria and reduces susceptibility to cleavage by Gram-negative beta lactamase enzymes. These properties confer activity against the important hospital pathogen Pseudomonas aeruginosa. Thus piperacillin is sometimes referred to as an "anti-pseudomonal penicillin".
Pseudomonas aeruginosa is a common encapsulated, gram-negative, aerobic–facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, P. aeruginosa is a multidrug resistant pathogen recognized for its ubiquity, its intrinsically advanced antibiotic resistance mechanisms, and its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes.
Antibiotic sensitivity testing or antibiotic susceptibility testing is the measurement of the susceptibility of bacteria to antibiotics. It is used because bacteria may have resistance to some antibiotics. Sensitivity testing results can allow a clinician to change the choice of antibiotics from empiric therapy, which is when an antibiotic is selected based on clinical suspicion about the site of an infection and common causative bacteria, to directed therapy, in which the choice of antibiotic is based on knowledge of the organism and its sensitivities.
Stenotrophomonas maltophilia is an aerobic, nonfermentative, Gram-negative bacterium. It is an uncommon bacterium and human infection is difficult to treat. Initially classified as Bacterium bookeri, then renamed Pseudomonas maltophilia, S. maltophilia was also grouped in the genus Xanthomonas before eventually becoming the type species of the genus Stenotrophomonas in 1993.
Azlocillin is an acyl ampicillin antibiotic with an extended spectrum of activity and greater in vitro potency than the carboxy penicillins. Azlocillin is similar to mezlocillin and piperacillin. It demonstrates antibacterial activity against a broad spectrum of bacteria, including Pseudomonas aeruginosa and, in contrast to most cephalosporins, exhibits activity against enterococci.
In microbiology, the minimum inhibitory concentration (MIC) is the lowest concentration of a chemical, usually a drug, which prevents visible in vitro growth of bacteria or fungi. MIC testing is performed in both diagnostic and drug discovery laboratories.
The disk diffusion test is a culture-based microbiology assay used in diagnostic and drug discovery laboratories. In diagnostic labs, the assay is used to determine the susceptibility of bacteria isolated from a patient's infection to clinically approved antibiotics. This allows physicians to prescribe the most appropriate antibiotic treatment. In drug discovery labs, especially bioprospecting labs, the assay is used to screen biological material and drug candidates for antibacterial activity. When bioprospecting, the assay can be performed with paired strains of bacteria to achieve dereplication and provisionally identify antibacterial mechanism of action.
The minimum bactericidal concentration (MBC) is the lowest concentration of an antibacterial agent required to kill a particular bacterium. It can be determined from broth dilution minimum inhibitory concentration (MIC) tests by subculturing to agar plates that do not contain the test agent. The MBC is identified by determining the lowest concentration of antibacterial agent that reduces the viability of the initial bacterial inoculum by ≥99.9%. The MBC is complementary to the MIC; whereas the MIC test demonstrates the lowest level of antimicrobial agent that inhibits growth, the MBC demonstrates the lowest level of antimicrobial agent that results in microbial death. This means that even if a particular MIC shows inhibition, plating the bacteria onto agar might still result in organism proliferation because the antimicrobial did not cause death. Antibacterial agents are usually regarded as bactericidal if the MBC is no more than four times the MIC. Because the MBC test uses colony-forming units as a proxy measure of bacterial viability, it can be confounded by antibacterial agents which cause aggregation of bacterial cells. Examples of antibacterial agents which do this include flavonoids and peptides.
Cefoxitin is a second-generation cephamycin antibiotic developed by Merck & Co., Inc. from Cephamycin C in the year following its discovery, 1972. It was synthesized in order to create an antibiotic with a broader spectrum. It is often grouped with the second-generation cephalosporins. Cefoxitin requires a prescription and as of 2010 is sold under the brand name Mefoxin by Bioniche Pharma, LLC. The generic version of cefoxitin is known as cefoxitin sodium.
Cefsulodin is a third-generation cephalosporin antibiotic that is active against Pseudomonas aeruginosa and was discovered by Takeda Pharmaceutical Company in 1977.
Sisomicin, is an aminoglycoside antibiotic, isolated from the fermentation broth of Micromonospora inositola. It is a newer broad-spectrum aminoglycoside most structurally related to gentamicin.
Mueller Hinton agar is a type of growth medium used in microbiology to culture bacterial isolates and test their susceptibility to antibiotics. This medium was first developed in 1941 by John Howard Mueller and Jane Hinton, who were microbiologists working at Harvard University. However, Mueller Hinton agar is made up of a couple of components, including beef extract, acid hydrolysate of casein, and starch, as well as agar to solidify the mixture. Meanwhile, The composition of Mueller Hinton agar can vary depending on the manufacturer and the intended use, but the medium is generally nutrient-rich and free of inhibitors that could interfere with bacterial growth.
Virtual colony count (VCC) is a kinetic, 96-well microbiological assay originally developed to measure the activity of defensins. It has since been applied to other antimicrobial peptides including LL-37. It utilizes a method of enumerating bacteria called quantitative growth kinetics, which compares the time taken for a bacterial batch culture to reach a threshold optical density with that of a series of calibration curves. The name VCC has also been used to describe the application of quantitative growth kinetics to enumerate bacteria in cell culture infection models. Antimicrobial susceptibility testing (AST) can be done on 96-well plates by diluting the antimicrobial agent at varying concentrations in broth inoculated with bacteria and measuring the minimum inhibitory concentration that results in no growth. However, these methods cannot be used to study some membrane-active antimicrobial peptides, which are inhibited by the broth itself. The virtual colony count procedure takes advantage of this fact by first exposing bacterial cells to the active antimicrobial agent in a low-salt buffer for two hours, then simultaneously inhibiting antimicrobial activity and inducing exponential growth by adding broth. The growth kinetics of surviving cells can then be monitored using a temperature-controlled plate reader. The time taken for each growth curve to reach a threshold change in optical density is then converted into virtual survival values, which serve as a measure of antimicrobial activity.
Ceftolozane/tazobactam, sold under the brand name Zerbaxa, is a combination antibiotic medication used for the treatment of complicated urinary tract infections and complicated intra-abdominal infections in adults. Ceftolozane is a cephalosporin antibiotic, developed for the treatment of infections with gram-negative bacteria that are resistant to conventional antibiotics. It was studied for urinary tract infections, intra-abdominal infections and ventilator-associated bacterial pneumonia.
Broth microdilution is a method used to test the susceptibility of microorganisms to antibiotics. It is the most commonly used method to perform this test in the United States.
Agar dilution is one of two methods used by researchers to determine the Minimum Inhibitory Concentration (MIC) of antibiotics. It is the dilution method most frequently used to test the effectiveness of new antibiotics when a few antibiotics are tested against a large panel of different bacteria.
