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Based upon a number of observations including that the gram-positive bacteria are the major producers of antibiotics and that, in general, gram-negative bacteria are resistant to them, it has been proposed that the outer cell membrane in gram-negative bacteria (diderms) has evolved as a protective mechanism against antibiotic selection pressure.
Antibiotic sensitivity testing is also conducted at a population level in some countries as a form of screening. [4] This is to assess the background rates of resistance to antibiotics (for example with methicillin-resistant Staphylococcus aureus), and may influence guidelines and public health measures. [4]
Beta-lactam (β-lactam) antibiotics are a broad-spectrum group that include some penams (penicillin derivatives such as methicillin and oxacillin) and cephems such as the cephalosporins. [1] Strains unable to resist these antibiotics are classified as methicillin-susceptible S. aureus, or MSSA.
Narrow-spectrum antibiotics have low propensity to induce bacterial resistance and are less likely to disrupt the microbiome (normal microflora). [3] On the other hand, indiscriminate use of broad-spectrum antibiotics may not only induce the development of bacterial resistance and promote the emergency of multidrug-resistant organisms, but also cause off-target effects due to dysbiosis.
A Gram stain is performed to show Gram-positive cocci in chains. Then, the organism is cultured on blood agar. The rapid pyrrolidonyl arylamidase (PYR) test is commonly used, wherein a positive reaction confers a presumptive identification of group A beta-hemolytic streptococci if the appearance and clinical context is consistent.
MDR bacteria can be broken into 3 main categories: Gram-positive, Gram-negative, and other . These bacteria employ various adaptations to avoid or mitigate the damage done by antimicrobials. With increased access to modern medicine there has been a sharp increase in the amount of antibiotics consumed. [3]
S. pyogenes is sensitive to penicillin, and has not developed resistance to it, [42] making penicillin a suitable antibiotic to treat infections caused by this bacterium. Failure of treatment with penicillin is generally attributed to other local commensal microorganisms producing β-lactamase, or failure to achieve adequate tissue levels in ...
Appropriate methodologies (including inducible clindamycin resistance) for testing antibiotic susceptibility are important because resistance to clyndamicin (antimicrobial resistance) can occur in some GBS strains that appear susceptible (antibiotic sensitivity) to clyndamicin in certain susceptibility tests.