Penicillin G potassium (Benzylpenicillin potassium)

Penicillin G potassium (Benzylpenicillin potassium), the potassium salt form of Penicillin G, is a narrow-spectrum β-lactam antibiotic with potent antimicrobial activity that exerts its bactericidal effect by inhibiting bacterial cell wall synthesis^[1,2]. Penicillin G potassium is primarily active against Gram-positive bacteria (such as Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus spp.) and certain Gram-negative bacteria (Neisseria meningitidis), and is commonly used for the treatment and research of diseases caused by bacterial infections^[3,4].

In vitro, Penicillin G potassium (0.8mg/mL) significantly increases the relative electrical conductivity of Agrobacterium tumefaciens T-37 after 5h of co-incubation, indicating altered membrane structure and enhanced permeability. Furthermore, after 18h of treatment, increases in nucleic acid (OD₂₆₀) and protein (OD₂₈₀) absorbance values demonstrate disruption of membrane integrity and leakage of cellular contents. SDS-PAGE analysis confirmed a time-dependent decrease in total intracellular protein levels over 4-16h of exposure, consistent with membrane damage and subsequent protein leakage^[5].

In vivo, following a single intramuscular injection (38mg/kg) in the gluteal muscle of six-month-old New Zealand White rabbits, Penicillin G potassium reached a mean peak plasma concentration of 9.5μg/mL within 36min. The plasma concentration declined to 0.32μg/mL and 0.13μg/mL at 9 and 12h post-administration, respectively, indicating a relatively short elimination half-life^[6]. In a murine model of pneumonia, intranasal administration of Penicillin G potassium (40μL; 1μg/μL; once daily for 3 days), initiated 4h after intranasal inoculation with Staphylococcus aureus (8.3×10⁹CFU/mL; 50μL), significantly reduced bacterial loads in the lungs and preserved alveolar structure in BALB/c mice^[7].

References:
[1] Bush K. Beta-lactam antibiotics: Penicillins[J]. Antibiotic and chemotherapy, 2010: 200-225.
[2] Prescott J F. Beta-lactam antibiotics: penam penicillins[J]. Antimicrobial therapy in veterinary medicine, 2013: 133-152.
[3] Nathwani D, Wood M J. Penicillins: a current review of their clinical pharmacology and therapeutic use[J]. Drugs, 1993, 45(6): 866-894.
[4] COCCI A G P. Benzylpenicillin (Penicillin G)[J]. Kucers' The Use of Antibiotics: A Clinical Review of Antibacterial, Antifungal, Antiparasitic, and Antiviral Drugs, -Three Volume Set, 2017: 23.
[5] Guo K, Zhang Q, Zhao J, et al. Antibacterial mechanism of Aspergillus niger xj spore powder crude extract B10 against Agrobacterium tumefaciens T-37[J]. Biotechnology & Biotechnological Equipment, 2021, 35(1): 162-169.
[6] Jekl V, Hauptman K, Minarikova A, et al. Pharmacokinetic study of benzylpenicillin potassium after intramuscular administration in rabbits[J]. Vet Rec, 2016, 179(1): 18.
[7] Liu Y, Li S, Shen T, et al. N-terminal myristoylation enhanced the antimicrobial activity of antimicrobial peptide PMAP-36PW[J]. Frontiers in Cellular and Infection Microbiology, 2020, 10: 450.

Penicillin G potassium (Benzylpenicillin potassium)是青霉素G的钾盐形式，是一种具有高效抗菌活性，通过抑制细菌细胞壁合成发挥杀菌作用的窄谱β-内酰胺类抗生素^[1,2]。Penicillin G potassium主要对革兰氏阳性菌（如金黄色葡萄球菌、肺炎球菌、链球菌）及部分革兰氏阴性菌（脑膜炎双球菌）具有活性，常用于细菌感染所引起的相关疾病治疗与研究^[3,4]。

在体外，Penicillin G potassium（0.8mg/mL）与T-37菌液混合培养5h后，能引起相对电导率的显著升高，表明细胞膜的基本结构发生了变化，提高了膜的通透性。Penicillin G potassium（0.8mg/mL）与T-37菌液混合培养18h，导致核酸吸光度（OD₂₆₀）和蛋白质吸光度（OD₂₈₀）增加，表明可以破坏细胞膜的完整性，使内容物泄露。Penicillin G potassium（0.8mg/mL）与T-37菌液混合培养4-16h，菌体内总蛋白含量随时间延长而降低，与细胞膜被破坏导致蛋白泄露的结果相互印证^[5]。

在体内，Penicillin G potassium（38mg/kg）通过单次臀部肌肉注射给药6月龄的新西兰白兔，在给药前0h和给药后0.25-24h进行药代动力学测定，Penicillin G potassium平均血浆浓度在36min内达到峰值9.5μg/mL，在9h和12h平均血浆药物浓度分别下降至0.32μg/mL和0.13μg/mL，半衰期较短^[6]。鼻内接种金黄色葡萄球菌感染BALB/c小鼠（8.3×10⁹CFU/mL; 50μL），4h后鼻腔给药Penicillin G potassium（40μL; 1μg/μL; qd）治疗小鼠3天，能显著降低肺部细菌数量并保证小鼠肺泡结构完整^[7]。