Probing the Fate of Different Structures of Beta-Lactam Antibiotics: Hydrolysis, Mineral Capture, and Influence of Organic Matter

Abstract

Beta-lactam antibiotics, which are used extensively in human and veterinary applications, are commonly detected in surface waters. To examine how the distinct structures of different generations of beta-lactam antibiotics can influence their persistence or degradation in environmental aqueous media, we examined the fate of two penams (amoxicillin and cloxacillin) and two cephems (cephalexin and ceftriaxone) at pH 5.0 and pH 7.0. By contrast to the lack of hydrolysis of the penam antibiotics at both pHs, we observed hydrolysis of cephalexin at pH 7.0 (t 1/2 = 12 d) and ceftriaxone at pH 5.0 (t 1/2 = 2.8 d). Using highperformance liquid chromatography coupled with a diode array detector or a high-resolution mass spectrometer, we were able to confirm thiotriazinone and 3-desacetyl cefotaxime as major hydrolysis products of ceftriaxone, and propose the hydrolytic cleavage of the benzene and cephem moieties from cephalexin. In addition, we studied the effects of smectite clay particles suspended in solutions without or with dissolved organic matter. The adsorption capacity of the clay was 4-to 9-fold higher at pH 7.0 than at pH 5.0. Subsequent X-ray diffraction analysis revealed that the antibiotic adsorption was not within the clay interlayer nanopores but occurred primarily on the external clay surfaces. The addition of dissolved organic matter interfered with the adsorption of a cephem antibiotic (ceftriaxone) on the clay, but the adsorption of a penam antibiotic (amoxicillin) remained unaffected. We employed molecular modeling simulations to probe the mechanisms of adsorption on the mineral surface. Our findings offer new insights on how the compound structures can dictate different fates of the beta-lactam class of antibiotics in environmental media.

Phosphonate herbicide interactions with quartz, montmorillonite, and quartz‐enriched agricultural soil

“…Furthermore, at the targeted circumneutral pH for both of our experiments and modeling, Damonte et al (2007) and Khoury et al (2010) reported that glyphosate adsorption on montmorillonite or bentonite (an adsorbent clay composed primarily of montmorillonite) was about fourfold less compared with adsorption conducted at low pH (pH 4); this difference was attributable to interlayer adsorption, which was proposed to be minimal at neutral or high pH. This pH-dependent adsorption whereby adsorption and intercalation were significantly decreased at circumneutral and high pH values was also reported for other ionizable contaminants, such as tetracycline antibiotics (Aristilde & Sposito, 2010; Aristilde et al, 2016), fluoroquinolone antibiotics (Okaikue-Woodi et al, 2018), and β-lactam antibiotics (Klein et al, 2021). According to Khoury et al, 2010, pH values greater than the point-of-zero charge would result in deprotonated clay edges, which can thus repel negatively charged adsorptives, the point-of-zero charge of montmorillonite was reported to be 3.4 ± 0.2 (Ijagbemi et al, 2009).…”

Degradation of Penicillinic Antibiotics and β‐Lactamase Enzymatic Catalysis in a Biomimetic Zn‐Based Metal–Organic Framework

“…The HPLC‐UV analysis shows, as a matter of fact, the formation of only one degradation product (Figure S12), which has been identified by HPLC‐ESI‐HRMS as the ion at m/z 414.0535 (Figure S13). This compound is produced by the hydrolysis of ceftriaxone at the sulfur atom of the carbamimidothioate group, previously characterized after hydrolysis at pH=5 after 12 days [43] …”

“…In turn, MOF 1 is also capable to degrade ceftriaxone, but following a different mechanism. Indeed, 1 is capable to efficiently hydrolyze ceftriaxone into thiotriazinone and 3-desacetyl cefotaxime, a reaction that without catalyst only occurs after 12 h. at pH = 5, [43] while leaving unchanged its four-membered β-lactam ring. Moreover, we have been capable to isolate and characterize, by single-crystal X-ray diffraction (SCXRD), a host guest aggregate containing MOF 1 and amoxicillin (see below, Figure 3), aiming at achieving unique snapshots of the hostguest interactions, ultimately responsible for the β-lactamase activity.…”

Quantitative Spectroscopic Analysis of Water Populations in the Hydrated Nanopore Environments of a Natural Montmorillonite

“…This force field has been shown to model appropriately the hydration of metal cations and interaction of MONT with organic and inorganic adsorptives. − Four interlayer nanopore environments with different Na + populations were modeled: a fully hydrated Na-MONTat 1.55 nm d 001 with 4 Na + and 40 waters, and two partially hydrated Na-MONT at with 4 Na + and 20 waters or at 1.24 nm d 001 with 4 Na + and 10 waters, and dry Na-MONT at 0.96 nm d 001 with 4 Na + . Each of these four systems were generated using the adsorption locator module in Materials Studio as previously described …”

“…Each of these four systems were generated using the adsorption locator module in Materials Studio as previously described. 72 The CASTEP NMR module of Materials Studio was employed to calculate the chemical shielding tensor and electric field gradient for the Na + in systems mentioned above. 73,74 Periodic cells were generated from the prepared fully hydrated Na + and Na + -MONT systems using the crystal building function in Materials Studio.…”