Current Concepts in Laboratory Testing to Guide Antimicrobial Therapy

Abstract

Antimicrobial susceptibility testing (AST) is indicated for pathogens contributing to an infectious process that warrants antimicrobial therapy if susceptibility to antimicrobials cannot be predicted reliably based on knowledge of their identity. Such tests are most frequently used when the etiologic agents are members of species capable of demonstrating resistance to commonly prescribed antibiotics. Some organisms have predictable susceptibility to antimicrobial agents (ie, Streptococcus pyogenes to penicillin), and empirical therapy for these organisms is typically used. Therefore, AST for such pathogens is seldom required or performed. In addition, AST is valuable in evaluating the activity of new and experimental compounds and investigating the epidemiology of antimicrobial resistant pathogens. Several laboratory methods are available to characterize the in vitro susceptibility of bacteria to antimicrobial agents. When the nature of the infection is unclear and the culture yields mixed growth or usual microbiota (wherein the isolates usually bear little relationship to the actual infectious process), AST is usually unnecessary and results may, in fact, be dangerously misleading. Phenotypic methods for detection of specific antimicrobial resistance mechanisms are increasingly being used to complement AST (ie, inducible clindamycin resistance among several gram-positive bacteria) and to provide clinicians with preliminary direction for antibiotic selection pending results generated from standardized AST (ie, ␤-lactamase tests). In addition, molecular methods are being developed and incorporated by microbiology laboratories into resistance detection algorithms for rapid, sensitive assessment of carriage states of epidemiologically and clinically important pathogens, often directly from clinical specimens (ie, presence of vancomycin-resistant enterococci in fecal specimens).

Antibiotic susceptibility testing in less than 30 min using direct single-cell imaging

“…Phenotypic antibiotic susceptibility tests (ASTs) are typically based on the detection of differential bacterial growth with and without antibiotics in liquid cultures or on solid agar plates (4). In liquid tests, detection is based on the change in OD, whereas the disk diffusion method is used on solid agar plates to identify inhibition zones (5).…”

Preparation of File (Sohan) by using the Probiotics with Chemical and Microbiologic Analysis for Individual's Health

“…Turbidity of pipe created by bacteria growth in the culture medium reported as +2, + 1 and -(minus) and power-plate was done in the MRS Agar and Mueller Hinton Agar culture medium [11][12][13][14][15][16].…”

“…Clinical studies show that Lactobacillus cells in in vitro conditions can decrease added cholesterol to the culture medium and in in vivo conditions also can reduce serum cholesterol. Jenkins [15] showed that increase of lipid in culture medium reduces the synthesis of lipid acids by lactic acid bacteria [20]. The findings indicate that probiotics are capable of absorbing cholesterol into their cell membranes in the presence of bile [23].…”

Role of the culture medium in porin expression and piperacillin-tazobactam susceptibility in Escherichia coli

“…Studies on hospital-acquired infections have also claimed the involvement of multidrug-resistant bacteria, and the recent emergence of carbapenem resistance has amplified the phenomenon (Khan et al, 2012;Theuretzbacher, 2012;Cohen, 2013). Consequently, an early diagnosis of resistant clinical isolates is key information for the clinician to select an appropriate treatment (Jorgensen & Ferraro, 2009;Orenga et al, 2009;Jenkins & Schuetz, 2012;Bhattacharya, 2013;Laxminarayan et al, 2013). Today, it is well recognized that the first step of antibiotic use is a key action that can govern the fate of the infection by selecting or rendering the bacteria more resistant via their adaptive response and resistosome (Schuldiner, 2009;Bhattacharya, 2013).…”

“…Reducing the time required for microbial identification and susceptibility tests represents a challenge and needs continuous improvement of methods, selected media and interpretation of raw data (Jorgensen & Ferraro, 2009;Jenkins & Schuetz, 2012;Bhattacharya, 2013). This detection is often carried out by automated systems that are based on early growth detection in an appropriate antibiotic containing medium that may differ in nutrients from the MuellerHinton (MH) reference medium (Livermore et al, 2002;Lee et al, 2008;Pitout et al, 2008;Jorgensen & Ferraro, 2009;Orenga et al, 2009).…”