Difference Between Streptomycin and Gentamicin

Streptomycin and Gentamicin are both aminoglycoside antibiotics, which are known for their effectiveness against a broad range of bacterial infections. Streptomycin, discovered in 1943, was the first antibiotic in this class and played a pivotal role in treating tuberculosis and plague. Its discovery marked a significant milestone in the battle against infectious diseases. Gentamicin, introduced later, is primarily used against Gram-negative bacterial infections and has been valuable in treating serious infections where other antibiotics might fail.

Both drugs work by inhibiting protein synthesis in bacteria, ultimately leading to bacterial cell death. Like all aminoglycosides, they have the potential to cause nephrotoxicity and ototoxicity, making careful dosing and monitoring essential.

Definition of Streptomycin

Streptomycin is an aminoglycoside antibiotic produced by the bacterium Streptomyces griseus. It is used primarily to treat tuberculosis and is also effective against certain other bacterial infections. Streptomycin works by interfering with the function of the 30S subunit of bacterial ribosomes, inhibiting protein synthesis and leading to bacterial cell death.

Due to the emergence of drug-resistant strains and the potential for side effects such as ototoxicity (hearing damage) and nephrotoxicity (kidney damage), its use has been reduced in favor of newer agents, but it remains an essential drug in specific clinical scenarios.

Mechanism of Action of Streptomycin

Streptomycin is an aminoglycoside antibiotic, and its primary mechanism of action is the inhibition of protein synthesis in susceptible bacteria. Here’s a more detailed breakdown of its mechanism:

1. Binding to the Ribosome: Streptomycin binds specifically to the 30S subunit of the bacterial ribosome. This binding interferes with the initiation complex between messenger RNA (mRNA) and the ribosomal subunit, effectively hampering the process by which translation is initiated.
2. Misreading of mRNA: The binding of Streptomycin induces a conformational change in the ribosome, leading to misreading of mRNA. This misreading results in the incorporation of incorrect amino acids into the growing polypeptide chain.
3. Inhibition of Translocation: Streptomycin also interferes with the translocation process. During protein synthesis, the ribosome moves along the mRNA, ensuring that tRNAs carrying the correct amino acids are positioned correctly. By affecting this translocation step, Streptomycin disrupts the elongation of the polypeptide chain.

The overall effect is the production of aberrant proteins within the bacterial cell, which can be non-functional or even harmful to the cell. Over time, this disruption in protein synthesis leads to bacterial growth inhibition and eventually bacterial cell death. It’s worth noting that because of the specificity of Streptomycin’s action on the bacterial 30S ribosomal subunit, it doesn’t have the same effect on human cells, which use 40S and 60S ribosomal subunits for protein synthesis.

Uses and Indications of Streptomycin

Streptomycin is an aminoglycoside antibiotic that has been historically significant in the treatment of various infections. Its use has decreased over time due to the development of drug-resistant strains and the availability of other antibiotics with fewer side effects.

Here are the primary uses and indications for Streptomycin:

1. Tuberculosis (TB):
   • Historically, Streptomycin was the first effective treatment for tuberculosis.
   • It’s used as a second-line agent for multidrug-resistant TB (MDR-TB).
2. Plague (caused by Yersinia pestis):
   • It can be used for both bubonic and pneumonic forms of the disease.
3. Tularemia (caused by Francisella tularensis):
   • Streptomycin is considered the drug of choice for this infection.
4. Brucellosis:
   • Although other antibiotics can be preferred, Streptomycin can be used in combination with other agents for brucellosis.
5. Endocarditis:
   • It may be used in combination with other antibiotics to treat endocarditis caused by enterococci.
6. Mycobacterium avium complex (MAC):
   • In some cases, it can be used for MAC infections in immunocompromised patients.

The above are the primary indications, but Streptomycin has been used for other infections historically. It’s worth noting that due to potential toxicities (like ototoxicity and nephrotoxicity), Streptomycin use is typically reserved for cases where other less toxic antibiotics are not effective or contraindicated. Always consult with a healthcare professional for appropriate therapeutic choices.

Side Effects and Concerns of Streptomycin

Streptomycin, like other aminoglycosides, has a range of side effects. The following are some of the common and significant side effects and concerns related to the use of Streptomycin:

Side Effects:

1. Ototoxicity:
   • This can manifest as damage to the inner ear, leading to hearing loss or balance issues (vertigo). Vestibular damage (affecting balance) is more commonly associated with Streptomycin than cochlear damage (affecting hearing).
2. Nephrotoxicity:
   • Streptomycin can cause kidney damage, which might present as reduced renal function, proteinuria, or even acute kidney injury.
3. Allergic Reactions:
   • These can range from rashes to more severe reactions like anaphylaxis or serum sickness-like reactions.
4. Neuromuscular Blockade:
   • In some cases, Streptomycin can interfere with neuromuscular transmission, leading to muscle weakness or even paralysis.
5. Blood Disorders:
   • Pancytopenia, eosinophilia, and thrombocytopenia have been reported with Streptomycin use.
6. Gastrointestinal Reactions:
   • Nausea, vomiting, and occasional disturbances in bowel habits can occur.

Concerns:

1. Resistance:
   • The emergence of Streptomycin-resistant strains, especially in Mycobacterium tuberculosis, is a significant concern, limiting its effectiveness in treating tuberculosis.
2. Pregnancy and Lactation:
   • Streptomycin has been shown to cross the placental barrier, and there are concerns about its use during pregnancy, particularly regarding potential auditory toxicity to the fetus. It’s generally avoided or used with caution during pregnancy.
3. Drug Interactions:
   • Streptomycin can interact with certain medications. For instance, concurrent use with other ototoxic or nephrotoxic drugs might increase the risk of these adverse effects. Using Streptomycin with neuromuscular blocking agents can increase the risk of neuromuscular blockade.
4. Therapeutic Monitoring:
   • Due to potential toxicities, patients on Streptomycin may require monitoring, including renal function tests, auditory evaluations, and assessment of balance and coordination.

Given these side effects and concerns, Streptomycin use is typically reserved for specific clinical scenarios where its benefits outweigh the risks, and it’s imperative to use the drug judiciously. Always consult with a healthcare professional regarding therapeutic decisions.

Definition of Gentamicin

Gentamicin is an aminoglycoside antibiotic derived from the bacterium Micromonospora purpurea. It is used to treat various types of bacterial infections, especially those caused by Gram-negative organisms. Like other aminoglycosides, gentamicin works by binding to the 30S subunit of bacterial ribosomes, thereby inhibiting protein synthesis and leading to bacterial cell death.

Gentamicin is potent and effective against many bacterial pathogens, but its use can be associated with nephrotoxicity (kidney damage) and ototoxicity (damage to the ear, leading to hearing loss or balance problems). Due to these potential side effects, monitoring of drug levels and renal function is often necessary during treatment.

Mechanism of Action of Gentamicin

Gentamicin is also an aminoglycoside antibiotic, much like Streptomycin, and shares a similar mechanism of action primarily aimed at inhibiting protein synthesis in susceptible bacteria.

Here’s a detailed breakdown of its mechanism:

1. Binding to the Ribosome: Gentamicin binds to the 30S subunit of the bacterial ribosome. This binding specifically targets a region called the A-site of the ribosome, altering its structure and function.
2. Misreading of mRNA: Once bound to the ribosome, Gentamicin induces a misreading of the mRNA sequence. As the ribosome interprets the genetic code on the mRNA to incorporate amino acids into a growing protein chain, the presence of Gentamicin causes it to frequently choose the wrong amino acid. This misreading results in the synthesis of aberrant proteins that are non-functional or detrimental to the bacterial cell.
3. Inhibition of Translocation: Like other aminoglycosides, Gentamicin also affects the translocation process. After an amino acid is added to a growing protein chain, the ribosome must move, or “translocate,” to the next codon on the mRNA. Gentamicin interferes with this step, further disrupting protein synthesis.
4. Inhibition of Ribosomal Assembly: There is evidence suggesting that Gentamicin might also prevent the proper assembly of the 30S and 50S ribosomal subunits into a functional 70S ribosome, thus providing another level of protein synthesis inhibition.

The net result of these actions is the production of non-functional or toxic proteins within the bacterial cell, which leads to bacterial growth inhibition and cell death. Due to the specificity of Gentamicin’s binding to the bacterial 30S ribosomal subunit, human cells, which have 40S and 60S ribosomal subunits, are largely unaffected in terms of protein synthesis, granting the antibiotic its selective toxicity. However, the nephrotoxic and ototoxic side effects seen with Gentamicin arise from its impact on mammalian cells at certain concentrations.

Uses and Indications of Gentamicin

Gentamicin is an aminoglycoside antibiotic widely used for its efficacy against a broad spectrum of bacterial pathogens. Here are the primary uses and indications for Gentamicin:

1. Gram-negative bacterial infections:
   • Gentamicin is particularly effective against several Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella, Serratia, and Salmonella species, among others.
2. Serious Infections:
   • Given its potency, it is used to treat severe infections like sepsis, intra-abdominal infections, complicated urinary tract infections, and certain respiratory tract infections.
3. Endocarditis:
   • Gentamicin can be used in combination with other antibiotics to treat endocarditis, especially when caused by Gram-negative bacteria or certain strains of enterococci.
4. Bone and Joint Infections:
   • It may be used as part of combination therapy for osteomyelitis or septic arthritis.
5. Pelvic Inflammatory Disease (PID):
   • Gentamicin can be used in combination with other agents for the treatment of PID.
6. Neonatal Infections:
   • Gentamicin is frequently used in neonatal units to treat serious bacterial infections in newborns due to its efficacy against many pathogens common in this population.
7. Topical Applications:
   • Gentamicin is available in topical forms, such as creams, ointments, and eye drops, for the treatment of bacterial skin infections, burns, or eye infections.
8. Peritonitis:
   • It is used in patients undergoing peritoneal dialysis who develop peritonitis.
9. Prophylaxis:
   • Sometimes used for prophylactic purposes during surgeries, especially gastrointestinal or genitourinary procedures, to prevent postoperative infections.

While Gentamicin is a powerful antibiotic, its potential side effects (like ototoxicity and nephrotoxicity) mean that it should be used judiciously, with careful monitoring of drug levels and renal function. As with all antibiotics, the emergence of drug-resistant strains is a concern, so appropriate use and stewardship are essential. Always consult with a healthcare professional for therapeutic decisions.

Side Effects and Concerns of Gentamicin

Gentamicin, an aminoglycoside antibiotic, is effective against a broad range of bacterial pathogens. Like other drugs in its class, it comes with potential side effects and concerns. Here are the main side effects and concerns related to the use of Gentamicin:

Side Effects:

1. Ototoxicity:
   • Gentamicin can cause damage to the inner ear. This damage can lead to hearing loss (cochlear toxicity) or problems with balance (vestibular toxicity).
2. Nephrotoxicity:
   • This refers to kidney damage. Gentamicin can affect the renal tubules, leading to reduced kidney function or even acute kidney injury. Signs might include increased serum creatinine and blood urea nitrogen, reduced urine output, or the presence of proteins or blood cells in the urine.
3. Neuromuscular Blockade:
   • Rarely, Gentamicin can interfere with the function of neuromuscular junctions, leading to muscle weakness or even respiratory paralysis, especially when administered with anesthetic or neuromuscular blocking agents.
4. Allergic Reactions:
   • Rashes, itching, and in rare cases, more severe reactions like anaphylaxis can occur.
5. Blood Disorders:
   • Some patients may experience changes in blood cell counts, such as eosinophilia or thrombocytopenia.
6. Injection Site Reactions:
   • Pain, irritation, or inflammation might occur at the site of injection.

Concerns:

1. Therapeutic Drug Monitoring:
   • Due to its narrow therapeutic window and potential for toxicity, it’s often necessary to monitor blood levels of Gentamicin, especially during prolonged therapy, to ensure they are within a safe and effective range.
2. Resistance:
   • Misuse or overuse can lead to the development of Gentamicin-resistant bacterial strains, reducing its effectiveness.
3. Pregnancy and Lactation:
   • Concerns exist about the use of Gentamicin during pregnancy due to potential risks to the fetus, particularly related to ototoxicity. It’s generally used with caution during pregnancy.
4. Drug Interactions:
   • Gentamicin can interact with various other medications, increasing the risk of ototoxicity, nephrotoxicity, or neuromuscular blockade when combined with other drugs with similar side effects or mechanisms.

Given these side effects and concerns, it’s essential to use Gentamicin judiciously and under the supervision of a healthcare professional. Regular monitoring and appropriate dosing can help minimize risks. Always consult a medical expert for therapeutic decisions and for understanding the potential impacts of the drug.

Comparison table of Streptomycin and Gentamicin

Here’s a comparison table between Streptomycin and Gentamicin:

While this table provides a general comparison, the specific features, advantages, and disadvantages of each drug can be more intricate. Always consult with a healthcare professional for detailed information and clinical decisions.

Importance in Modern Medicine

Aminoglycosides, which include both Streptomycin and Gentamicin, hold a significant place in modern medicine due to their potent antibacterial properties, especially against certain difficult-to-treat infections. Here’s a breakdown of their importance:

1. Treatment of Serious Infections: Aminoglycosides, particularly Gentamicin, are often used for severe bacterial infections, including those caused by Gram-negative bacteria like Pseudomonas aeruginosa, Escherichia coli, and Klebsiella. These pathogens can lead to life-threatening conditions like sepsis or meningitis.
2. Tuberculosis Management: While the use of Streptomycin has diminished over the years due to resistance, it historically represented a breakthrough in the treatment of tuberculosis (TB). It is still used in certain cases, especially multidrug-resistant TB, albeit less frequently than before.
3. Synergistic Use: Aminoglycosides are sometimes combined with other classes of antibiotics, like beta-lactams or vancomycin, to treat certain bacterial infections. This combination can offer a synergistic effect, where the combined action is greater than the sum of the individual effects.
4. Empirical Therapy: Given their broad spectrum, aminoglycosides are sometimes used empirically (before the causative organism is identified) for patients who are critically ill, especially when a Gram-negative bacterial infection is suspected.
5. Replacement for Penicillin-allergic Patients: In certain clinical scenarios where beta-lactam antibiotics are the drugs of choice but cannot be used due to patient allergies, Gentamicin might be a viable alternative.
6. Localized Treatment: Apart from systemic use, aminoglycosides like Gentamicin are available in topical forms for treating external infections, such as eye or ear infections.
7. Continued Research: As bacterial resistance becomes an increasing concern in modern medicine, there’s ongoing research into modifying aminoglycosides to overcome resistance while minimizing their side effects. This illustrates the continued relevance of this class of antibiotics.

Their importance in modern medicine is counterbalanced by concerns about their toxicities (notably nephrotoxicity and ototoxicity) and the emergence of resistant bacterial strains. Proper dosing, monitoring of drug levels, and clinical assessments are crucial when using aminoglycosides to ensure patient safety while effectively combating bacterial infections.

Similarities between Streptomycin and Gentamicin

Streptomycin and Gentamicin, both belonging to the aminoglycoside class of antibiotics, share several similarities:

1. Mechanism of Action: Both antibiotics primarily act by binding to the 30S subunit of bacterial ribosomes, disrupting protein synthesis.
2. Bactericidal Nature: They are both bactericidal, meaning they kill bacteria rather than just inhibiting their growth.
3. Gram-negative Coverage: Both are effective against a range of Gram-negative bacteria.
4. Ototoxicity and Nephrotoxicity: Both drugs can cause side effects such as damage to the ears (ototoxicity) and kidneys (nephrotoxicity).
5. Resistance Concerns: Bacterial resistance can develop to both antibiotics if they are overused or misused.
6. Treatment of Serious Infections: They are often reserved for treating severe infections due to their potent antibacterial effects and potential toxicities.

These shared properties reflect the common characteristics of the aminoglycoside class but also highlight the need for careful and judicious use in clinical settings.

Conclusion

Streptomycin and Gentamicin are both aminoglycoside antibiotics primarily known for their ability to inhibit protein synthesis in susceptible bacteria. While Streptomycin was one of the first effective treatments for tuberculosis, its usage has decreased due to the emergence of resistant strains. Gentamicin, on the other hand, is widely employed against a variety of Gram-negative bacterial infections.

Both antibiotics bind to the 30S subunit of bacterial ribosomes, disrupting protein synthesis by inducing misreading of mRNA and inhibiting translocation. While they are potent antibacterial agents, their therapeutic use is tempered by concerns of ototoxicity and nephrotoxicity. Proper monitoring and judicious use are crucial to maximize their benefits while minimizing potential side effects.