Microbiology Practice Exam

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What is considered the least effective antibiotic against bacterial infections?

Tetracycline
Penicillin
Ciprofloxacin
Erythromycin

The correct answer is: Penicillin

Penicillin is often regarded as having limited effectiveness against certain bacterial infections, particularly in strains that have developed resistance. While penicillin has historically been one of the cornerstones in treating various bacterial infections caused by gram-positive bacteria, its efficacy has diminished over time due to the emergence of antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). In contrast, tetracycline, ciprofloxacin, and erythromycin have broader spectrums of activity and can be used against a wider variety of bacterial pathogens. Tetracycline is effective against both gram-positive and gram-negative bacteria and has also been used for atypical pathogens. Ciprofloxacin, especially effective against gram-negative bacteria, is frequently utilized in treating urinary tract infections and respiratory infections. Erythromycin is effective against many gram-positive organisms and some gram-negative organisms, especially in patients who are allergic to penicillin. Hence, while penicillin remains valuable for treating certain infections, its limitations against resistant strains make it less effective compared to the other antibiotics listed.