Search Results (637)

Trachoma, caused by Chlamydia trachomatis (Ct), persists as a major cause of preventable blindness despite the global SAFE strategy. Understanding how Ct genovars and genovariants influence infection dynamics and clinical outcomes is crucial for sustaining elimination efforts and informing vaccine development. A four-year longitudinal study was conducted in a trachoma-endemic region of Tanzania across multiple rounds of mass drug administration (MDA) with azithromycin. Ct infections were genotyped by ompA sequencing to identify genovars and genovariants. Associations between genetic variants, bacterial load, and clinical signs of trachoma were assessed. Following MDA, a shift in Ct genovar prevalence occurred from genovar B to genovar A. Genovar B was associated with more severe clinical signs, including follicles, papillae, and scarring, whereas genovar A infections exhibited higher bacterial loads. Among 121 individuals with recurrent infections, 94% were re-infected with the same genovar, indicating limited protective immunity and incomplete clearance despite MDA coverage exceeding 60%. The genovariants B2, B9, and A2 predominated, with an A → T amino acid substitution in B9 potentially modifying antigenic recognition. Post-MDA, normalized genovariant diversity increased, suggesting ongoing transmission or strain reintroduction. Distinct genovar-associated clinical and immunological patterns underscore the need to elucidate genovar-specific virulence and immune evasion mechanisms. These findings provide key insights for optimizing trachoma control and advancing vaccine development. Full article

Impacted mandibular third molars present a common challenge in oral surgery, often associated with postoperative complications such as delayed healing and periodontal defects; therefore, optimizing adjunctive therapies is clinically important. In this study, we aimed to evaluate the efficacy of platelet-rich fibrin (PRF) and preoperative azithromycin in modulating inflammation and enhancing wound healing following surgical extraction of impacted mandibular third molars. In this prospective clinical study, healthy subjects aged 18–50 years were randomly assigned to three groups: a control group receiving standard postoperative amoxicillin therapy, a PRF group receiving PRF with standard therapy, and a PRF-plus-azithromycin group receiving PRF, standard therapy, and a single preoperative dose of azithromycin. Clinical parameters were assessed and cytomorphometric analysis was performed preoperatively and postoperatively. Clinical parameters generally improved over time in all groups (p < 0.001). Differences between groups were observed for interincisal distance, Landry Index, and pain scores, with a trend toward more favorable outcomes in the combined-therapy group. Cytomorphometric analysis revealed cellular alterations in the control group, relative stability in the PRF group, and intermediate changes in the combined-therapy group. Within the limitations of this study, the combination of PRF and preoperative azithromycin showed potential benefits in several postoperative outcomes. However, given the study design and sample characteristics, these findings should be considered preliminary and require confirmation in larger prospective studies before definitive clinical recommendations can be made. Full article

Background/Objectives: Antimicrobial resistance (AMR) in Staphylococcus spp. associated with poultry production is an emerging concern with implications for animal and public health. This study aimed to characterize antimicrobial susceptibility patterns and detect targeted methicillin resistance determinants in Staphylococcus isolates recovered from broiler chickens affected by bacterial chondronecrosis with osteomyelitis (BCO). Methods: A total of 200 bacterial isolates were evaluated, of which 167 were confirmed as Staphylococcus spp. Species identification was performed using presumptive phenotypic characterization followed by 16S rRNA gene sequencing. Antimicrobial susceptibility was assessed using disk diffusion, while presumptive methicillin-resistant phenotypes were evaluated using oxacillin screening and CHROMagar MRSA. Targeted molecular detection of mecA and mecC was performed by PCR. Results: The isolates demonstrated substantial species diversity, with S. aureus as the predominant species. Antimicrobial resistance was mainly observed against β-lactam antibiotics, particularly penicillin (33.5%), whereas high susceptibility was retained for non-β-lactam agents, including ciprofloxacin, tetracycline, trimethoprim–sulfamethoxazole, and azithromycin. A targeted PCR detected mecA in 7.2% of isolates, while mecC was not detected. The detection of mecA in oxacillin-susceptible isolates suggested genotype–phenotype discordance. Conclusions: BCO-associated Staphylococcus spp. from broiler chickens showed diverse species distribution, penicillin-dominant resistance, and targeted mecA detection across multiple species, supporting the use of combined phenotypic and molecular approaches for methicillin resistance surveillance. Full article

Background: Antimicrobial resistance, driven by inappropriate use and overuse of antibiotics, is a major public health threat. Diarrhea and respiratory illness are the leading causes of pediatric healthcare visits in low- and middle-income countries like Bangladesh. Despite clear WHO guidelines recommending limited use of antibiotics for these conditions, potentially inappropriate or non-prescription antibiotic use remains a concern. Methods: We interviewed caregivers of 3025 under-5 children via cellphones to assess common illnesses, associated care-seeking practices, and antibiotic use for diarrhea and respiratory illnesses experienced by their children in the prior 14 days. Caregivers were identified through hospital outpatient screening and were contacted over the phone for the interview at least two months after that hospital visit. Results: Among the participants, 116 (3.8%) reported diarrheal disease and 570 (18.8%) experienced respiratory illness during the preceding 2-week recall period. Among the children with diarrhea, 52.6% received antibiotics, and 73.8% obtained them over the counter from pharmacies. Among those with respiratory illness, 26.3% received antibiotics, and 58% procured them from local drugstores without a prescription from a registered physician. For diarrhea, azithromycin and metronidazole were the commonly used antibiotics, while for respiratory illness, cefixime and azithromycin were frequently used. Notably, 68% of the diarrheal children either sought care from local drugstores, were self-medicated, or did not receive any formal treatment. Conventional practice, long wait times at healthcare facilities, distance, and poverty were the main reasons for not seeking care from a registered healthcare provider. Conclusions: Understanding community-level antibiotic use and care-seeking behavior is essential to strengthening antibiotic stewardship and child health programs. Our findings suggest the need for context-sensitive community education, improved access to appropriate care, and enforcement of regulations restricting the over-the-counter sale of antibiotics to curb irrational and excessive antibiotic use. Full article

Background: The COVID-19 pandemic was associated with extensive empirical antibiotic exposure despite the predominantly viral etiology of the disease. Evaluating patterns of azithromycin use, prescribing determinants, and appropriateness provides insight into real-world antibiotic use under conditions of diagnostic uncertainty. Methods: We performed a retrospective cohort study including 3200 adult patients hospitalized with laboratory-confirmed COVID-19 at the General Hospital in Ferizaj between June 2020 and June 2022. Demographic characteristics, comorbidities, markers of disease severity, laboratory parameters, and antibiotic exposure were extracted from medical records. Azithromycin prescriptions were classified as appropriate, potentially appropriate, or inappropriate based on predefined clinical and laboratory indicators suggestive of bacterial co-infection. Drug utilization patterns, temporal trends, and independent determinants of inappropriate prescribing were assessed using descriptive analyses and multivariable logistic regression modeling. Results: Among 3200 hospitalized patients, 1968 (61.5%) received azithromycin. Of these prescriptions, 612 (31.1%) were classified as appropriate, 418 (21.3%) as potentially appropriate, and 938 (47.6%) as inappropriate. The proportion of inappropriate use decreased over time, from 52.4% in 2020–2021 to 38.7% in 2022 (p < 0.001). However, a substantial proportion of prescriptions remained inappropriate throughout the study period. In multivariable analysis, absence of laboratory markers suggestive of bacterial infection (OR 2.41; 95% CI 1.98–2.93), concomitant use of more than one antibiotic (OR 1.67; 95% CI 1.32–2.11), and lower clinical severity at admission (OR 1.54; 95% CI 1.21–1.95) were independently associated with inappropriate azithromycin prescribing. Conclusions: Azithromycin use was frequent among hospitalized adults with COVID-19, and a considerable proportion of prescriptions lacked clinical or laboratory justification. Although prescribing patterns changed over time, the persistence of inappropriate use highlights ongoing challenges in aligning antibiotic use with emerging evidence. These findings contribute to the understanding of antibiotic utilization patterns in acute care settings and underscore the importance of integrating objective diagnostic indicators into antimicrobial decision-making to strengthen stewardship practice. Full article

Background: Robust antimicrobial consumption monitoring and correlation with antibiotic resistance trends is critical to informing evidence-based antimicrobial stewardship and is recommended by the World Health Organization Global Action Plan on the containment of antimicrobial resistance. We estimated national and hospital-level antibacterial consumption patterns in Kenya. Materials and methods: National consumption data (January 2023–December 2024) was derived from aggregated import and donation permits at the Pharmacy and Poisons Board and standardized using the WHO ATC/DDD Index 2025. Consumption data for 2020 and 2021 that had been previously submitted by Kenya to WHO GLASS was retrieved and incorporated to allow a description of trends. Hospital-level data was collected from ten facilities across the country for the period from January 2024 to April 2025. Quality of use was evaluated using the WHO Access, Watch, and Reserve (AWaRe) categorisation with high-consumption antibiotics identified using the Drug Utilization 75% metric. Results: There was a gradual increase in national antibiotic consumption from 14.3 DID in 2020 to 22.2 DID in 2024. Oral formulations accounted for more than three quarters of antibiotics consumed. Access category antibiotic consumption ranged from 50.4% to 56.9% nationally and was 61.2% at hospital level. The national consumption of Watch antibiotics increased from 38.9% in 2020 to 46.1% in 2023 and declined to 40.7% in 2024. Amoxicillin and amoxicillin/clavulanic acid were the most commonly consumed antibiotics nationally in 2020 (40%), 2021 (27%) and 2024 (33%). Azithromycin was the most commonly consumed antibiotic in 2023 (27%), rising from 10% in 2020. Among parenteral antibiotics, benzylpenicillin was the most commonly consumed in 2020 and 2021, while ceftriaxone was the most commonly consumed agent in 2023 (24%) and 2024 (41%). At hospital level, ceftriaxone accounted for 56.5% of parenteral antibiotic use in county referral hospitals. Conclusions: Kenya’s antibacterial consumption is increasing. Use of Access antibiotics remains below the WHO target of 60%. The increasing use of Watch antibiotics, and in particular ceftriaxone and azithromycin, needs to be addressed to support Kenya’s efforts against antimicrobial resistance. Full article

Background/Objectives: Cryptosporidium parvum (C. parvum), a waterborne intestinal parasite, causes severe, persistent infections in immunocompromised hosts and has been linked to the onset of ileocecal adenocarcinoma. However, the molecular pathways linking chronic infection to carcinogenesis remain unclear. Nitazoxanide (NTZ), the only FDA-approved drug for this infection, shows limited efficacy. In contrast, azithromycin (AZM) possesses both antiparasitic and anticancer activity, though conclusive evidence supporting its effectiveness against cryptosporidiosis is still lacking. This study aimed to investigate the therapeutic potential of AZM against chronic cryptosporidiosis and its associated tumorigenic sequelae. Methods: Immunosuppressed mice were infected with C. parvum and treated with NTZ or AZM. Parasite burden was assessed by quantifying fecal oocyst shedding. Ileocecal tissues were analyzed for histopathology, inflammation (IL-6 and TNF-α), autophagy markers (LC3II, Beclin-1, and Atg7), PI3K/AKT signaling, and apoptotic markers (Bcl2, Bax, cleaved caspase-3, DR4, and DR5) using ELISA, real-time PCR, and Western blot. Results: Chronic C. parvum infection induced Vienna 4.4 adenocarcinoma, activated autophagy and PI3K/AKT signaling, and suppressed intrinsic and TRAIL-mediated apoptosis. AZM significantly reduced the parasitic load by 87%, outperforming NTZ (62%). It also restored epithelial integrity, attenuated inflammation, and counteracted pro-tumorigenic effects by inhibiting autophagy, downregulating the PI3K/AKT pathway, and stimulating apoptosis. Conclusions: AZM counteracted parasite-driven tumorigenic mechanisms by disrupting survival pathways and promoting apoptosis in infected and transformed cells. These findings provide evidence that AZM exerts dual antiparasitic effects and counteracts pro-tumorigenic signaling in chronic cryptosporidiosis, highlighting its potential as a therapeutic agent to prevent infection-associated ileocecal carcinogenesis. Full article

Background: Chronic obstructive pulmonary disease (COPD) is a progressive respiratory condition where many patients are given antibiotics like amoxicillin and macrolides (clarithromycin, azithromycin, roxithromycin) for bacterial infections. Recent concerns about clarithromycin’s potential link to cardiovascular events have arisen, despite its effectiveness against respiratory pathogens. This study aims to compare the cardiovascular risk of macrolide antibiotics versus amoxicillin in suspected COPD patients. Method: We used the Danish National Health Service Prescription Database (DNHSP) to identify COPD patients and their use of antibiotics. The included COPD patients were divided into four groups: amoxicillin users, roxithromycin users, clarithromycin users and azithromycin users. Data from multiple registries were merged to track hospitalizations, causes of death, and major adverse cardiovascular events (MACEs) as the primary endpoint. Patients were followed for a 3-year period. We applied adjusted Cox regression and sensitivity analyses with IPTW and IPCW to address confounders and censoring. Results: Our study involved 45,869 patients who were prescribed a long-acting muscarinic antagonist, over the age of 40 years old and who received one of the following antibiotics: amoxicillin, azithromycin, clarithromycin, or roxithromycin. No increased risk of MACEs was observed in macrolide-treated patients compared to those treated with amoxicillin (azithromycin: HR 0.97: 95% CI 0.83–1.13 p = 0.69, clarithromycin: HR 1.06 95% CI 0.87–1.28 p = 0.57, roxithromycin: HR 1.04 95% CI 0.91–1.18 p = 0.60), as confirmed by the sensitivity analysis (azithromycin: HR 0.95 95% CI 0.82–1.11 p = 0.52, clarithromycin: HR 1.05 95% CI 0.87–1.27 p = 0.60, roxithromycin: HR 1.05 95% CI 0.92–1.19 p = 0.48). Similarly, hazard ratios for all-cause mortality and cardiovascular death among the antibiotic groups showed no significant statistical differences. Conclusions: These findings suggest that there is no difference in the risk of MACEs, all-cause mortality, or cardiovascular death between the amoxicillin group and the macrolide group in a large and unselected population of COPD patients. Full article

Background: Pulmonary fibrosis (PF) is a major global health issue associated with substantial morbidity across all age groups. One of the important etiological factors contributing to PF is drug-induced lung injury, which can result from both direct and indirect damage to the pulmonary parenchyma caused by various pharmacological agents, including chemotherapeutics, antirheumatic drugs, cardiovascular medications, and certain antimicrobial agents. The aim of our study was to assess the structure of antibacterials involved in drug-induced PF (DIPF) and analyze signals of DIPF, calculating the reporting odds ratio (ROR) and proportional reporting ratio (PRR) using spontaneous reports (SRs) extracted from the Russian National Pharmacovigilance database. Methods: A retrospective, descriptive pharmacoepidemiological analysis of SRs from the AIS database for the period 1 April 2019–31 March 2025 was conducted. Results: A total of 130 SRs with data on DIPF associated with antibacterial agents were identified, with patients’ mean age of 59.1 ± 14.46 years. Death was reported in 65 SRs (50%) with a mean age of 53.0 ± 13.66 years. Next, antibacterials were identified as leaders: sulfamethoxazole (used alone or in combination with trimethoprim, 20.7% (n = 50)), azithromycin (18.2%, n = 44), levofloxacin (12.4%, n = 30), doxycycline (11.6%, n = 28), and cefuroxime (10.7%, n = 26). Disproportionality analysis performed with PRR and ROR calculation revealed the strongest association with DIPF for cefuroxime (PRR = 15.11, 95% confidence interval, CI: 10.25–22.27; ROR = 15.31, 95% confidence interval, CI: 10.33–22.68). Conclusions: Cefuroxime was revealed as a drug with an unexpected but robust safety signal for DIPF, warranting heightened clinical awareness and further investigation. The observed associations between antibacterial agents and DIPF should be interpreted with caution, as they may reflect protopathic bias (antibiotics prescribed for early symptoms of unrecognized pulmonary fibrosis) or context-dependent biological effects rather than true pro-fibrotic drug properties. Our findings do not establish causality but rather generate safety signals that warrant validation through prospective studies with detailed clinical phenotyping and mechanistic investigations using human cell lines. Full article

Babesiosis is a zoonosis caused by protozoan parasites of the genus Babesia. It has a worldwide distribution and affects many kinds of mammals, principally domestic animals and humans. Because there are no safe and effective vaccines available, the treatment and control for babesiosis continues to involve the use of chemotherapeutics. For years, only a few drugs have been used for clinical treatment, namely atovaquone plus azithromycin or clindamycin plus quinine for human, and imidocarb dipropionate and diminazene aceturate for domestic animals. Although screening and developing alternative drugs are continuously pursued, only a few drugs have been prospected to have clinical applications. Of these, tafenoquine has shown wide and potent antibabesial activity, offering a new option to control babesiosis. This article aims to present the current clinical therapeutic strategies for babesiosis and their limitations, as well as the prospect of tafenoquine as a promising drug to treat babesiosis. Full article

Background/Objectives: Scrub typhus, a life-threatening infection caused by Orientia tsutsugamushi, is treated with doxycycline or azithromycin. In severe disease, combination therapy with azithromycin and doxycycline had better clinical outcomes than either drug alone. However, it is not clear what causes the improved efficacy. To understand the same, we examined the plasma concentrations, intracellular concentrations, and efficacy of doxycycline, azithromycin, and both drugs in combination in 51 patients with severe scrub typhus. Methods: A randomly selected subset of adult (>18 years) participants from the INTREST trial (Clinical Trials Registry–India, number CTRI/2018/08/015159), who had been randomized in a 1:1:1 ratio to receive doxycycline, azithromycin, or both drugs, respectively, were included in this study for comparative drug concentration analysis. Blood samples were collected on days 0, 1, 3, and 7 to monitor bacterial load using quantitative polymerase chain reaction (PCR). Five milliliters of sterile blood were collected 3–10 h after the final dose on day 7 for comparative drug concentration measured using high-resolution multiple reaction monitoring. Data were analyzed in GraphPad Prism v.10.0.3. Results: Fifty-one patients (males, 59%; median age, 52 years) were enrolled. Fifteen, seventeen, and nineteen patients received azithromycin, doxycycline, and both, respectively. Doxycycline achieved a median plasma concentration of 1112 (42.51–5697) ng/mL and was undetectable intracellularly. The intracellular concentration of azithromycin (1127 [16.78–19,250] ng/mL) surpassed its plasma concentration (227.1 [48.78–1022] ng/mL). On day 3, PCR negativity rates were 56.24%, 93.3%, and 94.7% in the doxycycline, azithromycin, and combination groups, respectively. Conclusions: The high plasma concentrations of doxycycline and intracellular accumulation of azithromycin may contribute to improved clinical outcomes when used in combination. Full article

Background/Objectives: Staphylococcus aureus, particularly methicillin-resistant strains, is a leading cause of severe pneumonia. Understanding local molecular epidemiology, including virulence gene profiles and antimicrobial resistance (AMR) mechanisms, is crucial for effective infection control. This pilot study aimed to characterize S. aureus isolates from pneumonia patients in Karaganda, Kazakhstan. Methods: We collected 48 respiratory samples from patients with pneumonia across three medical institutions. Bacterial identification was performed using MALDI-TOF MS. Antimicrobial susceptibility testing (AST) was carried out using European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Whole-genome sequencing of S. aureus isolates was conducted on an Ion Torrent S5 platform. Genomic analysis included multilocus sequence typing (MLST), identification of virulence and AMR genes, and phylogenetic reconstruction. Results: S. aureus was identified in 14.6% (n = 7) of pneumonia cases included in this study. All isolates (100%, n = 7) were phenotypically resistant to benzylpenicillin. The mecA gene was detected in 57.1% of isolates (n = 4), while phenotypic resistance to methicillin was observed in 28.6% (n = 2) of the isolates. Resistance to azithromycin (57.1%, n = 4) and levofloxacin (42.9%, n = 3) was observed among the isolates. Two isolates (28.6%) were multidrug-resistant (MDR). Genomic analysis revealed the prevalence of the ST22 clone (57.1%, n = 4) in the studied cohort. Other sequence types were ST97, ST8, and ST45 (14.3% each). Phylogenetic analysis showed clustering consistent with MLST profiles. All isolates carried a conserved core virulence arsenal, including hemolysin (hla, hlg), biofilm-forming genes (icaADBC), immune evasion genes (sak, scn), and iron acquisition genes (isd). The Panton–Valentine leukocidin (PVL) genes were detected in three isolates. AMR gene analysis revealed the ubiquitous presence of mepA and tetracycline efflux pump genes, along with regulatory genes (arlRS, mepR, mgrA). The blaZ and ermA genes were not detected despite high phenotypic resistance to penicillin and macrolides. Conclusions: This study reports the identification of the virulent and resistant ST22 S. aureus clone in pneumonia cases in Karaganda, Kazakhstan. The discordance between phenotypic and genotypic AMR profiles underscores the necessity for integrated diagnostic approaches. Full article

Objectives: Outpatient antibiotic prescribing is a major driver of antimicrobial resistance, yet detailed long-term analyses of prescribing patterns in Croatia remain limited. This study aimed to analyze trends in outpatient antibiotic prescriptions issued in Croatian primary healthcare from 2015 to 2024, stratified by antibiotic class, substance, and the WHO AWaRe classification. Methods: A retrospective analysis of nationwide data on antibiotic prescriptions issued in primary care outpatient settings was conducted using the data from the Central Health Information System of the Republic of Croatia. All prescriptions for ATC group J01 antibiotics issued between 1 January 2015 and 31 December 2024 were included. The primary outcome was the annual number of issued outpatient antibiotic prescriptions, described overall and by substance. Annual counts were additionally expressed as a percentage of the 2015 baseline (index year = 100%) to enable the comparison across substances with different prescribing volumes. The prescriptions were classified according to the WHO AWaRe framework. Results: A total of 31,048,414 outpatient antibiotic prescriptions were issued between 2015 and 2024. Overall prescribing declined by 5.6% from 2015 to 2019, followed by a marked decrease of 21.0% in 2020, and subsequently rebounded to 3,338,235 prescriptions by 2024, a number virtually identical to pre-pandemic levels. Co-amoxiclav and azithromycin together accounted for 49.5% of all prescriptions. By 2024, prescribing third-generation cephalosporins increased by 281.9% compared to the 2015 levels, while prescribing amoxicillin decreased by 43.6% over the same period. The proportion of Access antibiotics declined from 64.7% in 2015 to 57.9% in 2024. Conclusions: The main challenge for antimicrobial stewardship in Croatia lies not only in overall prescribing volume but in prescribing composition. Targeted interventions are needed to reduce reliance on broad-spectrum agents and promote the use of narrower-spectrum first-line alternatives. Full article

Background/Objectives: Atopic dermatitis (AD) is associated with gut dysbiosis linked to early-life antibiotic use and Staphylococcus aureus colonization. Gum Arabic (GA), a prebiotic, may modulate this dysbiosis and influence AD-related microbial balance. This study evaluated whether GA could support AD-associated probiotics-Lactobacillus casei, Bifidobacterium bifidum, and Bifidobacterium infantis-under amoxicillin- or azithromycin-containing conditions, examined the response of S. aureus under the same screening conditions, and developed GA-phospholipid-based semisolid carriers for topical application. Methods: Probiotic strains were cultured with 1–5% GA in the presence and absence of antibiotics, and viable cell counts were assessed. Sixteen topical formulations containing propylene glycol or isopropyl myristate in a hydrogenated phosphatidylcholine base were prepared and screened for rheological properties and galactose release using in vitro release testing (IVRT) and HPLC-UV. Results: GA at 1–2% concentrations promoted probiotic growth in antibiotic-free conditions. GA preserved B. infantis viability under azithromycin exposure in this in vitro screening model. For S. aureus, numerical CFU differences were observed between antibiotic-only and GA-containing conditions; however, the present screening design was not intended to determine antibiotic interaction outcomes. Formulations F14 (2% GA + 7% IPM) and F15 (3% GA + 7% IPM) exhibited optimal spreadability. IVRT showed that 6 h cumulative galactose release varied by formulation (F6 > F10 > F14 > F15). Conclusions: GA demonstrated dose-dependent prebiotic activity and preserved B. infantis viability under azithromycin exposure in this in vitro screening model. For S. aureus, the observed CFU differences between antibiotic-only and GA-containing conditions should be considered exploratory only and do not allow for conclusions regarding interference with antibiotic efficacy. Optimized GA-HPC systems with suitable rheological and release characteristics represent promising candidates for further preclinical investigation. Full article

Salmonella enterica remains a major food safety concern in poultry, and processing-related stress can influence its survival and persistence. This study evaluated the phenotypic expression of S. enterica serotypes Kentucky (SK), Infantis (SI), Schwarzengrund (SS), and Typhimurium (ST) following antimicrobial and temperature stressors. A pre-harvest isolate of each serotype was gradually exposed to increasing concentrations of peracetic acid (PAA) and quaternary ammonium compounds (QACs), starting at 40 ppm and 1 ppm, respectively, until minimum inhibitory and bactericidal concentrations (MICs/MBCs) were established. Stressed cells were then subjected to cold (4 °C, 60 min) and heat (55 °C, 6 min) shock and assessed for sanitizer tolerance, biofilm formation and recovery, and antibiotic resistance. Sanitizer tolerance after daily conditioning varied among S. enterica serotypes, with ST and SK showing the highest tolerance to PAA and QACs, respectively. The tolerance of PAA variants increased by 10–20 ppm and QAC variants by 2–8 ppm following stress exposure. The double-stressed variants of ST significantly (p < 0.05) formed more biofilm than the control after PAA, whereas no significant differences were observed among the variants for other serotypes. Biofilm recovery was higher for the stressed variants of SI and SS (p < 0.05) following PAA stress but remained the same across all serotypes after QAC stress. QAC-stressed variants showed more phenotypic changes across the antibiotics tested. Notably, the stressed variants of SK, SS, and ST displayed increased MICs, including a 2- to 4-fold rise in azithromycin for the SK and ST variants. There was an increase in the MICs of ceftriaxone and nalidixic acid for some SK and SS variants. These findings suggest that environmental stress can significantly enhance the tolerance, survival, and persistence of S. enterica. Full article