A set of principles and practical suggestions for equitable fieldwork in biology.

Field biology is an area of research that involves working directly with living organisms in situ through a practice known as "fieldwork." Conducting fieldwork often requires complex logistical planning within multiregional or multinational teams, interacting with local communities at field sites, and collaborative research led by one or a few of the core team members. However, existing power imbalances stemming from geopolitical history, discrimination, and professional position, among other factors, perpetuate inequities when conducting these research endeavors. After reflecting on our own research programs, we propose four general principles to guide equitable, inclusive, ethical, and safe practices in field biology: be collaborative, be respectful, be legal, and be safe. Although many biologists already structure their field programs around these principles or similar values, executing equitable research practices can prove challenging and requires careful consideration, especially by those in positions with relatively greater privilege. Based on experiences and input from a diverse group of global collaborators, we provide suggestions for action-oriented approaches to make field biology more equitable, with particular attention to how those with greater privilege can contribute. While we acknowledge that not all suggestions will be applicable to every institution or program, we hope that they will generate discussions and provide a baseline for training in proactive, equitable fieldwork practices.

Effects of cancer-induced cachexia and administration of L-glutathione on the intestinal mucosa in rat.

Walker-256 tumor is an experimental model known to promote cachexia syndrome, oxidative stress, and systemic inflammation. This study evaluated the duodenal mucosa of rats with Walker-256 tumor administered with 1% L-glutathione, intending to evaluate the damage caused by cancer-associated cachexia in the gastrointestinal tract and the effects of antioxidant administration on mucosal protection. Twenty-four 55-day-old male Wistar rats were distributed into four groups: control (C); control administered with 1% L-glutathione (C-GSH); Walker-256 tumor (W) and Walker-256 tumor administered with 1% L-glutathione (W-GSH). After 14 days of treatment, the duodenum was harvested for morphometric analysis of the mucosa, proliferation, apoptosis, immunostaining of varicosities immunoreactive (IR) to vasoactive intestinal peptide (VIP) and 5-HT-IR cells, and quantification of mast cells and goblet cells. Walker-256 tumor-bearing rats showed cachexia syndrome, mucosal atrophy, reduced cell proliferation, reduced 5-HT-IR cells, and increased goblet cells and VIPergic varicosities, which were not reversed by L-glutathione. On the other hand, L-glutathione caused a reduction of cells in apoptosis and mast cell recruitment, demonstrating a partial recovery of the damage detected in the intestinal mucosa.

Associations Between Rank, Sex, and Parity With Musculoskeletal Injuries Sustained During Annual Military Physical Fitness Test.

ABSTRACT: Edwards, CM, da Silva, DF, Puranda, JL, Souza, SCS, Semeniuk, K, and Adamo, KB. Associations between rank, sex, and parity with musculoskeletal injuries sustained during annual military physical fitness test. J Strength Cond Res 38(2): 367-373, 2024-Musculoskeletal injuries pose a significant threat to the well-being of military personnel. Attempts to use physical employment standard test results as predictors of injury are underway, but little is known about injuries sustained during the tests. This study sought to identify body regions most likely to be reported as injured during the annual Canadian Armed Forces (CAF) physical fitness evaluation. In addition, sex, rank, and parity status are explored as possible associated factors for injury. A total of 1,796 actively serving CAF members were categorized by sex (1,030 male participants; 766 female participants), rank (1,142 Non-Commissioned Members [NCM]; 638 Officers), and parity (314 parous female participants; 435 nulliparous female participants). Sex, rank, and parity were associated with body regions reportedly injured during an annual CAF fitness assessment (significance p ≤ 0.05). When compared with male participants, female participants were more likely to be injured {aOR: 1.797 (95% [confidence interval] CI: 1.45-2.23)} and more prone to injury of the wrist (adjusted odds ratio [aOR]: 1.933 [95% CI: 1.20-3.12]), hip (aOR: 3.445 [95% CI: 2.07-5.728]), or lower back (aOR: 1.55 [95% CI: 1.18-2.04]). Non-Commissioned Members were more likely to injure the neck (aOR: 2.14 [95% CI: 1.18-3.88]) or shoulder (aOR: 2.03 [95% CI: 1.31-3.15]), when compared with Officers. Parous female participants reported pelvis/abdomen injury at a higher rate than the nulliparous group (5 vs. 1.7%, p = 0.019). Injuries sustained during an annual CAF fitness assessment differ based on sex, rank, and parity. Canadian Armed Forces female participants, NCM, and parous female participants may require specific physical fitness support in preparation for the annual physical fitness test.

Gestational weight loss and fetal growth in uncomplicated pregnancies among women with obesity: a population-based retrospective cohort study.

OBJECTIVE: The impact of gestational weight loss (GWL) on fetal growth among women with obesity remains unclear. This study aimed to examine the association between weight loss during pregnancy among women with body mass index (BMI) ≥ 30 kg/m2 and the risk of small-for-gestational-age (SGA) and large-for-gestational-age (LGA) neonates. METHODS: We conducted a retrospective, population-based cohort study of women with pre-pregnancy obesity that resulted in a singleton live birth in 2012-2017, using birth registry data in Ontario, Canada. Women with pregnancy complications or health conditions which could cause weight loss were excluded. GWL is defined as negative gestational weight change (≤0 kg). The association between GWL and fetal growth was estimated using generalized estimating equation models and restricted cubic spline regression analysis. Stratified analysis was conducted by obesity class (I:30-34.9 kg/m2, II:35-39.9 kg/m2, and III + : ≥40 kg/m2). RESULTS: Of the 52,153 eligible women who entered pregnancy with a BMI ≥ 30 kg/m2, 5.3% had GWL. Compared to adequate gestational weight gain, GWL was associated with an increased risk of SGA neonates (aRR:1.45, 95% CI: 1.30-1.60) and a decreased risk of LGA neonates (aRR: 0.81, 95% CI:0.73-0.93). Non-linear L-shaped associations were observed between gestational weight change and SGA neonates, with an increased risk of SGA observed with increased GWL. On the contrary, non-linear S-shaped associations were observed between gestational weight change and LGA neonates, with a decreased risk of LGA observed with increased GWL. Similar findings were observed from the stratified analysis by obesity class. CONCLUSION: These findings highlight that GWL in women with obesity may increase the risk of SGA neonates but reduce the risk of LGA neonates. Recommendations of GWL for women with obesity should be interpreted with caution.

Characteristics Associated with Pelvic Floor Disorders among Female Canadian Armed Forces Members.

OBJECTIVES: Urinary incontinence (UI) and pelvic organ prolapse (POP) are prevalent pelvic floor disorders (PFDs) among the female population. In the military environment, being a non-commissioned member (NCM), and physically demanding occupations are factors associated with higher PFD risk. This study seeks to characterize the profile of female Canadian Armed Forces (CAF) members reporting symptoms of UI and/or POP. METHODS: Present CAF members (18-65 years) responded to an online survey. Only current members were included in the analysis. Symptoms of UI and POP were collected. Multivariate logistic regressions analyzed the relationships between PFD symptoms and associated characteristics. RESULTS: 765 active members responded to female-specific questions. The prevalence of self-reported POP and UI symptoms were 14.5% and 57.0%, respectively, with 10.6% of respondents reporting both. Advanced age (adjusted odds ratio [aOR]: 1.062, CI 1.038-1.087), a body mass index (BMI) categorized as obese (aOR: 1.909, [1.183-3.081]), parity ≥1 (e.g., aOR for 1: 2.420, [1.352-4.334]) and NCMs (aOR: 1.662, [1.144-2.414]) were factors associated with urine leakage. Parity of ≥2 (aOR: 2.351, [1.370-4.037]) compared to nulliparous and having a perception of a physically demanding job (aOR: 1.933, [1.186-3.148]) were associated with experiencing POP symptoms. Parity of ≥2 increased the odds of reporting both PFD symptoms (aOR: 5.709, [2.650-12.297]). CONCLUSION: Parity was associated with greater odds of experiencing symptoms of UI and POP. Higher age, higher BMI, and being an NCM were associated with more symptoms of UI, and the perception of having a physically demanding role increased the likelihood of reporting POP symptoms.

Exploring weight bias internalization in pregnancy.

BACKGROUND: Recent research has shown that pregnant individuals experience weight stigma throughout gestation, including negative comments and judgement associated with gestational weight gain (GWG). Weight bias internalization (WBI) is often a result of exposure to weight stigma and is detrimental to biopsychological health outcomes. The purpose of this study was to explore WBI in pregnancy and compare scores based on maternal weight-related factors including pre-pregnancy body mass index (BMI), obesity diagnosis and excessive GWG. METHODS: Pregnant individuals in Canada and USA completed a modified version of the Adult Weight Bias Internalization Scale. Self-reported pre-pregnancy height and weight were collected to calculate and classify pre-pregnancy BMI. Current weight was also reported to calculate GWG, which was then classified as excessive or not based on Institute of Medicine (2009) guidelines. Participants indicated if they were diagnosed with obesity by a healthcare provider. Inferential analyses were performed comparing WBI scores according to pre-pregnancy BMI, excessive GWG, and obesity diagnosis. Significance was accepted as p < 0.05 and effect sizes accompanied all analyses. RESULT: 336 pregnant individuals completed the survey, with an average WBI score of 3.9 ± 1.2. WBI was higher among those who had a pre-pregnancy BMI of obese than normal weight (p = 0.04, η2 = 0.03), diagnosed with obesity than not diagnosed (p < 0.001, Cohen's d = 1.3), and gained excessively versus not (p < 0.001, Cohen's d = 1.2). CONCLUSIONS: Pregnant individuals who have a higher BMI, obesity and gain excessively may experience WBI. Given that weight stigma frequently occurs in pregnancy, effective person-oriented strategies are needed to mitigate stigma and prevent and care for WBI.

Physical Activity and Weight Gain Throughout Pregnancy Are Associated With Umbilical Cord Markers.

OBJECTIVE: Maternal serum and umbilical cord (UC) lipid and glucose levels are influenced by a variety of maternal factors over the course of pregnancy, including maternal physical activity (PA) levels and gestational weight gain (GWG). However, previous research has not assessed the interaction of these 2 variables. This study investigated mid-gestation (24-28 weeks) and late gestation (34-38 weeks) maternal and UC serum lipid and glucose profiles in relation to maternal PA status and GWG, independently and in combination. METHODS: This study had a longitudinal design. Pregnant participants (n = 40) were categorized as active or inactive based on the 2019 Canadian Guideline for Physical Activity throughout Pregnancy, and GWG was categorized as insufficient, appropriate, or excessive based on 2009 Institute of Medicine recommendations. Fasting maternal serum was taken in mid- and late gestation, and venous UC serum was taken at birth. RESULTS: No relationship was found between maternal serum values and PA and/or GWG. Infants born to individuals who were physically active across pregnancy, or who were active in mid-pregnancy and had their activity status drop in late gestation, had lower UC total cholesterol levels than those who were inactive throughout pregnancy (P < 0.0001). Participants who had gained weight appropriately at mid-gestation had significantly lower UC glucose levels than those who gained weight insufficiently (P = 0.040) or excessively (P = 0.021). CONCLUSION: In our study, PA, and GWG (independently and in combination) may not have affected maternal serum; however, meeting PA recommendations at mid-gestation may provide prophylactic effects on UC serum, potentially providing long-term health benefits to the newborn.

Evaluating the correlation between amniotic fluid volume and estimated fetal weight in healthy pregnant women.

OBJECTIVES: The establishment of cut-offs for normal amniotic fluid volume (AFV) is valuable to predict perinatal outcomes. However, the most common methods to measure AFV are not accurate enough. It is important to understand factors that may be able to increase the accuracy of the calculation of AFV cut-off values. The objective of this study was to verify the correlation between AFV and estimated fetal weight (EFW). METHODS: Records from almost 7,000 patients between 2012 and 2017 were accessed through hospital databases. The AFV measurements included in our analysis were obtained using the maximum vertical pocket technique. RESULTS: AFV was positively correlated with EFW in the overall, male and female samples; however, the magnitude of the association was small (0.1

Population characteristics associated with adherence to prenatal group-based exercise programs.

Community-based supervised group exercise may be an effective option to increase activity levels throughout pregnancy. Previous studies that have explored predictors of low adherence to exercise during pregnancy have not examined group-based settings. We analysed an international cohort of 347 pregnant women who participated in group-based prenatal exercise interventions (from <20 weeks to 34-36 weeks pregnant). Probable adherence predictors informed by previous literature that were assessed included: pre-pregnancy physical activity level and body mass index (BMI) classification, age, number of previous pregnancies, and education level. Adherence was measured by attendance. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were calculated to explore the relationship between the selected predictors and high adherence (≥70%). Post-secondary education level versus only secondary (aOR 5.28; CI 1.67; 16.72) or primary level (aOR 13.82; CI 4.30; 44.45) presented greater likelihood to have high adherence to the exercise intervention than low adherence. Future research and public health initiatives should consider implementing strategies to overcome education-related barriers to improve accessibility to prenatal exercise.

The role of IL-10 in immune responses against Pseudomonas aeruginosa during acute lung infection.

Pseudomonas aeruginosa is considered an opportunistic pathogen of great clinical importance. The clearance of this bacterium occurs through recognition of the pathogen by innate immune system receptors, leading to a lung inflammatory response. However, this response must be controlled via immunoregulatory pathways. In this study, we evaluate the role of endogenous murine IL-10 after acute infection with the virulent strain P. aeruginosa PA14. To assess the role of IL-10, intratracheal infection with the PA14 strain was performed in C57BL/6 or IL-10 KO mice. The PA14 strain was recovered in both types of animals, although IL-10 KO mice presented a higher number of viable bacteria in the lung when compared to the C57BL/6 group. Histopathological and stereological analyses showed that IL-10 KO mice had higher tissue damage and inflammatory infiltrate when compared to control animals. The activity of MMP-9 but not MMP-2, as well as IL-6 and TNF-α expression, were augmented in the lungs of infected animals and was much more evident in IL-10 KO animals when compared to the other analyzed groups. This work indicates that endogenous IL-10 control P. aeruginosa infection, the expression of pro-inflammatory genes, MMP-9 activity and histopathological processes of the infectious process in question.

The effects of intervening with physical activity in the early years (ages 3-5) on health-related quality of life: a secondary analysis of the Activity Begins in Childhood (ABC) trial.

PURPOSE: Limited research has measured the effect of physical activity (PA) interventions on health-related quality of life (HRQoL) among pre-school-aged children. This study evaluates the effect of the Activity Begins in Childhood (ABC) cluster-randomized controlled trial designed to increase PA in the ages 3-5 years on HRQoL. METHODS: This was a cluster-randomized controlled trial where the intervention group included PA education delivered to daycare providers only, or daycare providers and parents. In the current study, the two PA intervention groups were combined. The comparator group received standard daycare curriculum (COM). A total of 215 children were included (PA n = 161, COM n = 54). Parents completed the proxy Pediatric Quality of Life Inventory Generic Core Scale (PedsQL™ 4.0) to measure HRQoL at baseline and the end of the 6-month trial. HRQoL scores were analyzed as physical, psychosocial, and total domains. Baseline and 6-months measurements were compared for PA and COM groups, and mean changes in scores (95% confidence intervals) were measured using absolute values. RESULTS: No between-group differences were observed for the physical (p = 0.17), psychosocial (p = 0.95) or total scores (p = 0.20). Paired comparisons showed that only the PA group improved psychosocial- (PA mean difference = 2.18 (0.20, 4.15), p = 0.03; COM mean difference = 2.05 (- 1.03, 5.13), p = 0.19) and total-HRQoL scores (PA mean difference = 2.83 (1.83, 3.84), p < 0.001; COM mean difference = 0.19 (- 1.78, 2.16), p = 0.84) after 6 months. CONCLUSION: Although the within-PA group analysis showed an improvement in psychosocial and total HRQoL scores from baseline, no between-group differences were observed in the HRQoL over time among children aged 3-5 years.

Eating Habits, Advice from Family/Friends, and Limited Personal Effort May Increase the Likelihood of Gaining Outside Gestational Weight Gain Recommendations.

OBJECTIVES: The present study analyzed the association between (i) eating habits during pregnancy, (ii) advice from family or friends about gestational weight gain (GWG), and iii) personal effort to stay within weight gain limits, and meeting GWG recommendations. METHODS: Participants included pregnant and postpartum women who completed the validated electronic maternal health survey (EMat). Sociodemographic, lifestyle variables, and body mass index were covariates used in the analyses. RESULTS: Among all eligible women (1171), and a subset of women receiving a specific GWG target from HCP (365, 31.2%), participants who considered that their eating habits became less healthy, or could not evaluate if habits changed, had a higher likelihood of gaining above (adjusted odds ratio, aOR = 2.62; 95% CI 1.84; 3.73 for the total sample (TS); aOR = 4.79; CI 2.32;9.88 for the subset) GWG guidelines after adjusting for the covariates. Women who received advice from family or friends about how much weight they should gain while pregnant were more likely to experience GWG below (TS: aOR = 1.49; CI 1.02;2.17; subset: aOR = 1.95; CI 1.03;3.68) and above (TS: aOR = 1.42; CI 1.01;1.99; subset: aOR = 1.92; CI 1.06;3.48) guidelines, when compared to women who did not receive family/friends advice. Moreover, lower personal effort to stay within weight gain limits was associated with gaining below (TS: aOR = 1.77; CI 1.07;2.92; subset: aOR = 2.71; CI 1.30; 5.65) GWG guidelines. CONCLUSIONS FOR PRACTICE: Women self-reporting less healthy eating habits than before pregnancy, receiving advice from family/friends about GWG, and lower personal effort to stay within guidelines, had an increased odds of weight gain discordant with recommendations.

The Antibiotic Trimethoprim Displays Strong Mutagenic Synergy with 2-Aminopurine.

We show that trimethoprim (TMP), an antibiotic in current use, displays a strong synergistic effect on mutagenesis in Escherichia coli when paired with the base analog 2-aminopurine (2AP), resulting in a 35-fold increase in mutation frequencies in the rpoB-Rifr system. Combination therapies are often employed both as antibiotic treatments and in cancer chemotherapy. However, mutagenic effects of these combinations are rarely examined. An analysis of the mutational spectra of TMP, 2AP, and their combination indicates that together they trigger a response via an alteration in deoxynucleoside triphosphate (dNTP) ratios that neither compound alone can trigger. A similar, although less strong, response is seen with the frameshift mutagen ICR191 and 2AP. These results underscore the need for testing the effects on mutagenesis of combinations of antibiotics and chemotherapeutics.

Biofilm formation by Salmonella Enteritidis and Salmonella Typhimurium isolated from avian sources is partially related with their in vivo pathogenicity.

Salmonella Enteritidis and Salmonella Typhimurium are among the most prevalent serotypes isolated from salmonellosis outbreaks and poultry. Salmonella spp. have the capacity to form biofilms on several surfaces, which can favour survival in hostile environments, such as slaughterhouses. Salmonella strains present differences in pathogenicity. However, there is little information regarding the pathogenicity of S. Enteritidis and S. Typhimurium isolated from avian sources and their relationship to biofilm production. The aim of this study was to use a novel pathogenicity index and a biofilm production assay to evaluate their relationships within these serotypes. In addition, we detected the presence of the spiA and agfA genes in these strains. Biofilm formation was investigated at two temperatures (37 °C and 28 °C) using microtiter plate assay, and the results were compared with the individual pathogenicity index of each strain. PCR was used to detect spiA and agfA, virulence genes associated with biofilm production. S. Enteritidis and S. Typhimurium strains were capable of producing biofilm at 37 °C and 28 °C. Sixty-two percent and 59.5% of S. Enteritidis and 73.8% and 46.2% of S. Typhimurium produced biofilm at 37 °C and 28 °C, respectively. Biofilm production at 37 °C was significantly higher in both serotypes. Only S. Enteritidis was capable of adhering strongly at both temperatures. Biofilm production was related to pathogenicity index only at 28 °C for S. Enteritidis. spiA and agfA were found in almost all strains and were not statistically associated with biofilm production.

Phenotypic and Molecular Characterization of Salmonella Enteritidis SE86 Isolated from Poultry and Salmonellosis Outbreaks.

Salmonella Enteritidis remains a standout among the leading causes of foodborne diseases worldwide. Previous studies have demonstrated that a unique clonal group of Salmonella Enteritidis, named SE86, is involved in foodborne outbreaks in southern Brazil and is frequently identified among strains isolated from poultry. The aim of this study was to determine the influence of the isolation source (food products involved in salmonellosis outbreaks and poultry sources) on the phenotypic and molecular characteristics of Salmonella Enteritidis SE86. A biofilm formation assay, antimicrobial susceptibility test, polymerase chain reaction identification of virulence-associated genes, and phage type 4 (PT4) assessment were performed to characterize Salmonella Enteritidis SE86. The human strains presented less antimicrobial resistance than the poultry strains. Resistance to some substances was related to the isolation source of the strain. Strains of the same clonal group presented different biofilm production abilities. Biofilm formation was independent of the isolation source at all temperatures. Temperature influenced biofilm formation only by the poultry strains. Most of the investigated genes presented a high frequency and a regular distribution, regardless of the isolation source. The spvB, spiA, pagC, sipB, prgH, spaN, sitC, and lpfC genes were associated with the avian strains, whereas iroN was associated with the strains isolated from food products involved in salmonellosis outbreaks. Most strains belonged to PT4. No relationship was found between biofilm production and antimicrobial resistance or between the virulence profile and biofilm production or antimicrobial resistance.

Restoration of density of interstitial cells of Cajal in the jejunum of diabetic rats after quercetin supplementation.

BACKGROUND: Interstitial cells of Cajal (ICC) are required for normal motility in the gastrointestinal tract. Depletion of ICC has been associated with diabetic gastroenteropathy. PURPOSE: To determine the effect of quercertin supplementation on anoctamin-1 (Ano1) immunoreactive ICC in the myenteric region (ICC-MY) and deep muscular plexus (ICC-DMP) in the jejunum of diabetic rats. METHODS: Thirty-two 90-day-old male Wistar rats were distributed into the following groups: normoglycemic (C), normoglycemic supplemented with quercetin (CQ; 40 mg daily), diabetic (D), and diabetic supplemented with quercetin (DQ; 40 mg daily). Diabetes was induced by streptozotocin injection. After 120 days, preparations of the jejunal muscular and submucosal layers were immunostained for Ano1 to visualize ICC. Evaluation of the immunofluorescence intensity as well as density of ICC was performed. RESULTS: The density of ICC-MY was 46% lower in group D compared to group C (p < 0.01); ICC-DMP were reduced by 37% (p > 0.05). After quercertin treatment, the densities of ICC-MY were significantly higher in the DQ group compared to group D (ICC-MY: 58%, p < 0.05). Supplementation with quercetin in normoglycemic animals (CQ) compared with group C did not significantly change the ICC density (p > 0.05). CONCLUSIONS: In STZ-treated diabetic rats, diabetes promoted a reduction in the density of jejunal ICC-MY with no significant effect on ICC-DMP. Supplementation with quercetin (DQ) appeared to protect ICC-MY from depletion in diabetes possibly due to its antioxidant action.

Mutagen Synergy: Hypermutability Generated by Specific Pairs of Base Analogs.

UNLABELLED: We tested pairwise combinations of classical base analog mutagens in Escherichia coli to study possible mutagen synergies. We examined the cytidine analogs zebularine (ZEB) and 5-azacytidine (5AZ), the adenine analog 2-aminopurine (2AP), and the uridine/thymidine analog 5-bromodeoxyuridine (5BrdU). We detected a striking synergy with the 2AP plus ZEB combination, resulting in hypermutability, a 35-fold increase in mutation frequency (to 53,000 × 10(-8)) in the rpoB gene over that with either mutagen alone. A weak synergy was also detected with 2AP plus 5AZ and with 5BrdU plus ZEB. The pairing of 2AP and 5BrdU resulted in suppression, lowering the mutation frequency of 5BrdU alone by 6.5-fold. Sequencing the mutations from the 2AP plus ZEB combination showed the predominance of two new hot spots for A·T→G·C transitions that are not well represented in either single mutagen spectrum, and one of which is not found even in the spectrum of a mismatch repair-deficient strain. The strong synergy between 2AP and ZEB could be explained by changes in the dinucleoside triphosphate (dNTP) pools. IMPORTANCE: Although mutagens have been widely studied, the mutagenic effects of combinations of mutagens have not been fully researched. Here, we show that certain pairwise combinations of base analog mutagens display synergy or suppression. In particular, the combination of 2-aminopurine and zebularine, analogs of adenine and cytidine, respectively, shows a 35-fold increased mutation frequency compared with that of either mutagen alone. Understanding the mechanism of synergy can lead to increased understanding of mutagenic processes. As combinations of base analogs are used in certain chemotherapy regimens, including those involving ZEB and 5AZ, these results indicate that testing the mutagenicity of all drug combinations is prudent.

Exploring Synergy between Classic Mutagens and Antibiotics To Examine Mechanisms of Synergy and Antibiotic Action.

We used classical mutagens in Gram-negative Escherichia coli to study synergies with different classes of antibiotics, test models of antibiotic mechanisms of action, and examine the basis of synergy. We used 4-nitroquinoline 1-oxide (4NQO), zebularine (ZEB), 5-azacytidine (5AZ), 2-aminopurine (2AP), and 5-bromodeoxyuridine (5BrdU) as mutagens (with bactericidal potency of 4NQO > ZEB > 5AZ > 2AP > 5BrdU) and vancomycin (VAN), ciprofloxacin (CPR), trimethoprim (TMP), gentamicin (GEN), tetracycline (TET), erythromycin (ERY), and chloramphenicol (CHL) as antibiotics. We detected the strongest synergies with 4NQO, an agent that oxidizes guanines and ultimately results in double-strand breaks when paired with the bactericidal antibiotics VAN, TMP, CPR, and GEN, but no synergies with the bacteriostatic antibiotics TET, ERY, and CHL. Each of the other mutagens displays synergies with the bactericidal antibiotics to various degrees that reflect their potencies, as well as with some of the other mutagens. The results support recent models showing that bactericidal antibiotics kill bacteria principally by ultimately generating more double-strand breaks than can be repaired. We discuss the synergies seen here and elsewhere as representing dose effects of not the proximal target damage but rather the ultimate resulting double-strand breaks. We also used the results of pairwise tests to place the classic mutagens into functional antibacterial categories within a previously defined drug interaction network.