Absence Of Antibiotic Exposure Research Articles

Macrolide and fluoroquinolone resistance associated mutations in Mycoplasma genitalium in men who have sex with men attending STI clinic: A pilot study from India.

Background Increasing rates of macrolide and fluroquinolone resistance in Mycoplasma genitalium (MG) are being reported worldwide with resultant treatment failure. Aims and objectives We aimed to determine the level of antibiotic resistance of MG in men who have sex with men (MSM) attending a sexually transmitted infections (STIs) clinic in New Delhi, India. Methods Real-time polymerase chain reaction (PCR) assays targeting MgPa and pdhD genes were performed to detect MG rectal, urogenital or oropharyngeal infections in 180 MSM between January 2022 and June 2023. Macrolide resistance-associated mutations (MRM) and quinolone resistance-associated mutations (QRM) were detected by specific amplification of domain V of 23SrRNA gene and appropriate regions of parC and gyrA genes respectively followed by sequencing. PCR-based screening for Chlamydia trachomatis (CT) infection was also performed. Results A total of 13 (7.2%) MSM were positive for MG infection. The most common site of infection was anorectum (8/13; 61.5%) followed by the urethra (5/13; 38.5%). None of the patients had infection at both the sites, and no oropharyngeal MG infection was detected. CT infection was detected in 37 (20.6%) MSM. Of the 13 MG-infected MSM, 6 (46.2%) were co-infected with CT. MRM and QRM were found in five (46.2%) and two (15.4%) strains, respectively. Both Quinolone resistance mutation (QRM)-harbouring strains also harboured MRM. All the five MG isolates carried the MRM A2071G. Both the QRM isolates co-harboured the parC and gyrA single-nucleotide polymorphisms. There was no correlation between the presence of antibiotic resistance and co-infection with CT (P = 0.52). Limitation Because all patients in the study were MSM, the high rate of resistance to macrolides and fluoroquinolones could not be extrapolated for non-MSM patients. Conclusion This is a report of an initial survey of antibiotic resistance to MG in a country where its diagnosis and treatment are not routinely available. We found a high prevalence of MG-carrying MRM, QRM and dual-class resistance in MSM in the absence of antibiotic exposure. This study mandates the need for both screening and detection of antimicrobial resistance against MG.

ESBL Escherichia coli Isolates Have Enhanced Gut Colonization Capacity Compared to Non-ESBL Strains in Neonatal Mice.

ABSTRACTExtended-spectrum beta-lactamase (ESBL)-producing Escherichia coli can cause invasive infections in infants and immunocompromised children with high associated morbidity and mortality. The gut is a major reservoir of these strains in the community. Current dogma dictates that antimicrobial resistance is associated with a fitness cost. However, recent data show that some contemporary ESBL E. coli strains may be more “fit” compared to nonresistant E. coli strains. Here, we use whole-genome sequencing to first characterize 15 ESBL E. coli strains isolated from infants in a Pakistani community, a clinical extraintestinal pathogenic ESBL E. coli ST131 strain, and a non-ESBL commensal E. coli strain, and then use a novel animal model of early life gut colonization to assess the ability of these strains to colonize the infant mouse gut. We determined that CTX-M-15 was present in all the ESBL strains, as well as additional beta-lactamases and genes conferring resistance to multiple antibiotic classes. In the animal model, 11/16 ESBL E. coli strains had significantly higher burden of colonization at week four of life compared to commensal strains, even in the absence of selective antibiotic pressure, suggesting that these strains may have enhanced fitness despite being highly antimicrobial resistant.IMPORTANCE Antimicrobial resistance is a global public health emergency. Infants, especially preterm infants and those in the neonatal intensive care unit, immunocompromised hosts, and those with chronic illnesses are at highest risk of adverse outcomes from invasive infections with antimicrobial-resistant strains. It has long been thought that resistance is associated with a fitness cost, i.e., antimicrobial-resistant strains are not able to colonize the gut as well as nonresistant strains, and that antibiotic exposure is a key risk factor for persistent colonization with resistant strains. Here, we use a novel infant mouse model to add to the growing body of literature that some highly-resistant contemporary Escherichia coli strains can persist in the gut with a significant burden of colonization despite absence of antibiotic exposure.

The pandemic Escherichia colisequence type 131 strain is acquired even in the absence of antibiotic exposure.

The pandemic Escherichia colisequence type 131 strain is acquired even in the absence of antibiotic exposure.

Maternal gut and breast milk microbiota affect infant gut antibiotic resistome and mobile genetic elements

The infant gut microbiota has a high abundance of antibiotic resistance genes (ARGs) compared to adults, even in the absence of antibiotic exposure. Here we study potential sources of infant gut ARGs by performing metagenomic sequencing of breast milk, as well as infant and maternal gut microbiomes. We find that fecal ARG and mobile genetic element (MGE) profiles of infants are more similar to those of their own mothers than to those of unrelated mothers. MGEs in mothers’ breast milk are also shared with their own infants. Termination of breastfeeding and intrapartum antibiotic prophylaxis of mothers, which have the potential to affect microbial community composition, are associated with higher abundances of specific ARGs, the composition of which is largely shaped by bacterial phylogeny in the infant gut. Our results suggest that infants inherit the legacy of past antibiotic consumption of their mothers via transmission of genes, but microbiota composition still strongly impacts the overall resistance load.

Biofilm: A Hotspot for Emerging Bacterial Genotypes.

Bacteria have the ability to adapt to changing environments through rapid evolution mediated by modification of existing genetic information, as well as by horizontal gene transfer (HGT). This makes bacteria a highly successful life form when it comes to survival. Unfortunately, this genetic plasticity may result in emergence and dissemination of antimicrobial resistance and virulence genes, and even the creation of multiresistant "superbugs" which may pose serious threats to public health. As bacteria commonly reside in biofilms, there has been an increased interest in studying these phenomena within biofilms in recent years. This review summarizes the present knowledge within this important area of research. Studies on bacterial evolution in biofilms have shown that mature biofilms develop into diverse communities over time. There is growing evidence that the biofilm lifestyle may be more mutagenic than planktonic growth. Furthermore, all three main mechanisms for HGT have been observed in biofilms. This has been shown to occur both within and between bacterial species, and higher transfer rates in biofilms than in planktonic cultures were detected. Of special concern are the observations that mutants with increased antibiotic resistance occur at higher frequency in biofilms than in planktonic cultures even in the absence of antibiotic exposure. Likewise, efficient dissemination of antimicrobial resistance genes, as well as virulence genes, has been observed within the biofilm environment. This new knowledge emphasizes the importance of biofilm awareness and control.

Culture if spikes? Indications and yield of blood cultures in hospitalized medical patients

Although optimal utilization of blood cultures has been studied in populations, including emergency room and intensive care patients, less is known about the use of blood cultures in populations consisting exclusively of patients on a medical service. To identify the physician-selected indication and yield of blood cultures ordered after hospitalization to an acute medical service and to identify populations in which blood cultures may not be necessary. A prospective cohort study was performed at a single Veterans Affairs Medical Center from October 1, 2014 through April 15, 2015. Participants included all hospitalized patients on a medical service for whom a blood culture was ordered. The main outcomes were the rate of true positive blood cultures and the predictors of true positive cultures. The true positive rate was 3.6% per order. The most common physician-selected indications were fever and leukocytosis, neither of which alone was highly predictive of true positive blood cultures. The only indication significantly associated with a true positive blood culture was "follow-up previous positive" (likelihood ratio [LR]+ 3.4, 95% confidence interval [CI]: 1.8-6.5). The only clinical predictors were a working diagnosis of bacteremia/endocarditis (LR+ 3.7, 95% CI: 2.5-5.7) and absence of antibiotic exposure within 72 hours of the culture (LR+ 2.4, 95% CI: 1.2-4.9). The rate of true positive blood cultures among patients on a medical service was lower than previously studied. Using objective and easily obtainable clinical characteristics, including antibiotic exposure and working diagnosis, may improve the likelihood of true positive blood cultures. Journal of Hospital Medicine 2016;11:336-340. © 2016 Society of Hospital Medicine.

Management and Outcomes of Patients With Failed Fecal Microbiota Transplantation for Recurrent Clostridium difficile Infection

Introduction: Fecal Microbiota Transplantation (FMT) is a safe and effective treatment for recurrent Clostridium difficile infection (rCDI) with success rates >85%. Data on management and clinical sequelae of patients who have rCDI after FMT are scarce. In this study, we report our single-center tertiary care experience on post-FMT treatment and outcomes of patients with failed FMT. Methods: All patients who underwent FMT for rCDI from August 2012 to April 2015 were included. Donor and recipient screening was performed using standard protocols and rCDI treatment was stopped 24 hours before FMT. Patients were followed using standardized questionnaires and instructed to call with recurrent diarrhea. FMT failure was defined as recurrent diarrhea with a positive C. difficile stool test. Clinical data including demographics, comorbid conditions, donor information, FMT route, post-FMT systemic antibiotic exposure and post-FMT CDI management were collected and analyzed. Results: After a median follow-up of 61.4 weeks (range 4-147 weeks), of the 238 rCDI patients who underwent FMT; 25 (10.5%; median age 63.5 years [range 18.2-89]; 56% female) had subsequent rCDI. Amongst these 25 patients, 8 (33%) had underlying IBD, 1 had chronic liver disease and 2 were hospitalized with severe-complicated CDI. Standard unrelated donors were used in 21 (84%) patients and colonoscopy was the most common instillation route (88%). Among FMT failures, post-FMT; 4 patients (16%) had minimal symptom improvement after FMT and were early failures. The median time to rCDI after FMT was 19.5 weeks (range 1.4-152 weeks) with 90% patients recurring within 68 weeks. Patients with rCDI after FMT, commonly were exposed to systemic antibiotics (15/25; 60%) leading to FMT failure and 33% had underlying IBD which appeared to be a risk factor in the absence of antibiotic exposure. Of the patients with rCDI after FMT, 4% were treated with metronidazole, 80% were treated with vancomycin and 16% with fidaxomicin. Overall, 5 patients (20%) who had further recurrences were successfully managed with repeat FMT. One patient elected comfort care and died in hospice, one died of non-rCDI related causes, one underwent colectomy for severe-complicated rCDI and one is on chronic low dose vancomycin therapy. Conclusion: CDI recurred in 10% patients after FMT and most common reasons include repeat antibiotic exposure and underlying IBD. Patients with FMT failure can be managed with repeat antibiotics or repeat FMT.

Changes to Its Peptidoglycan-Remodeling Enzyme Repertoire Modulate β-Lactam Resistance in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections and is resistant to many antibiotics. Among its primary mechanisms of resistance is expression of a chromosomally encoded AmpC β-lactamase that inactivates β-lactams. The mechanisms leading to AmpC expression in P. aeruginosa remain incompletely understood but are intricately linked to cell wall metabolism. To better understand the roles of peptidoglycan-active enzymes in AmpC expression-and consequent β-lactam resistance-a phenotypic screen of P. aeruginosa mutants lacking such enzymes was performed. Mutants lacking one of four lytic transglycosylases (LTs) or the nonessential penicillin-binding protein PBP4 (dacB) had altered β-lactam resistance. mltF and slt mutants with reduced β-lactam resistance were designated WIMPs (wall-impaired mutant phenotypes), while highly resistant dacB, sltB1, and mltB mutants were designated HARMs (high-level AmpC resistant mutants). Double mutants lacking dacB and sltB1 had extreme piperacillin resistance (>256 μg/ml) compared to either of the single knockouts (64 μg/ml for a dacB mutant and 12 μg/ml for an sltB1 mutant). Inactivation of ampC reverted these mutants to wild-type susceptibility, confirming that AmpC expression underlies resistance. dacB mutants had constitutively elevated AmpC expression, but the LT mutants had wild-type levels of AmpC in the absence of antibiotic exposure. These data suggest that there are at least two different pathways leading to AmpC expression in P. aeruginosa and that their simultaneous activation leads to extreme β-lactam resistance.

Acquired Antibiotic Resistance: Are We Born with It?

The rapid emergence of antibiotic resistance (AR) is a major public health concern. Recent findings on the prevalence of food-borne antibiotic-resistant (ART) commensal bacteria in ready-to-consume food products suggested that daily food consumption likely serves as a major avenue for dissemination of ART bacteria from the food chain to human hosts. To properly assess the impact of various factors, including the food chain, on AR development in hosts, it is important to determine the baseline of ART bacteria in the human gastrointestinal (GI) tract. We thus examined the gut microbiota of 16 infant subjects, from the newborn stage to 1 year of age, who fed on breast milk and/or infant formula during the early stages of development and had no prior exposure to antibiotics. Predominant bacterial populations resistant to several antibiotics and multiple resistance genes were found in the infant GI tracts within the first week of age. Several ART population transitions were also observed in the absence of antibiotic exposure and dietary changes. Representative AR gene pools including tet(M), ermB, sul2, and bla(TEM) were detected in infant subjects. Enterococcus spp., Staphylococcus spp., Klebsiella spp., Streptococcus spp., and Escherichia coli/Shigella spp. were among the identified AR gene carriers. ART bacteria were not detected in the infant formula and infant foods examined, but small numbers of skin-associated ART bacteria were found in certain breast milk samples. The data suggest that the early development of AR in the human gut microbiota is independent of infants' exposure to antibiotics but is likely impacted by exposure to maternal and environmental microbes during and after delivery and that the ART population is significantly amplified within the host even in the absence of antibiotic selective pressure.

Tracking Acquired Antibiotic Resistance in Commensal Bacteria of Galápagos Land Iguanas: No Man, No Resistance

BackgroundAntibiotic resistance, evolving and spreading among bacterial pathogens, poses a serious threat to human health. Antibiotic use for clinical, veterinary and agricultural practices provides the major selective pressure for emergence and persistence of acquired resistance determinants. However, resistance has also been found in the absence of antibiotic exposure, such as in bacteria from wildlife, raising a question about the mechanisms of emergence and persistence of resistant strains under similar conditions, and the implications for resistance control strategies. Since previous studies yielded some contrasting results, possibly due to differences in the ecological landscapes of the studied wildlife, we further investigated this issue in wildlife from a remote setting of the Galapagos archipelago.Methodology/Principal FindingsScreening for acquired antibiotic resistance was carried out in commensal enterobacteria from Conolophus pallidus, the terrestrial iguana of Isla Santa Fe, where: i) the abiotic conditions ensure to microbes good survival possibilities in the environment; ii) the animal density and their habits favour microbial circulation between individuals; and iii) there is no history of antibiotic exposure and the impact of humans and introduced animal species is minimal except for restricted areas. Results revealed that acquired antibiotic resistance traits were exceedingly rare among bacteria, occurring only as non-dominant strains from an area of minor human impact.Conclusions/SignificanceWhere both the exposure to antibiotics and the anthropic pressure are minimal, acquired antibiotic resistance traits are not normally found in bacteria from wildlife, even if the ecological landscape is highly favourable to bacterial circulation among animals. Monitoring antibiotic resistance in wildlife from remote areas could also be a useful tool to evaluate the impact of anthropic pressure.

Quantifying the Impact of Bacterial Fitness and Repeated Antimicrobial Exposure on the Emergence of Multidrug-Resistant Gram-Negative Bacilli

The emergence of multidrug resistance among gram-negative bacilli is complex. Nu- merous factors need to be considered, including the biological fitness cost of resistance, fitness- compensatory mutations and frequency and type of antibiotic exposure. A mathematical model evaluating these complex relationships was developed in an individual colonized with strains of pan-susceptible, single-, two- and multidrug-resistant (MDR) gram-negative bacilli (GN). The ef- fect of bacterial fitness, compensatory mutations and the frequency of three-antimicrobial regimen exposure to predominance of multidrug-resistant strains were quantified. The model predicts that initially, in the absence of antibiotic exposure, the biologically fitter pan-susceptible strain pre- dominates over the resistant strains. Over time, the fitness of the MDR strains increases faster with repeated antimicrobial exposure, through compensatory-fitness mutations. Increasing the frequency of exposure to the three-antimicrobial regimen or, increasing the initial fitness of the resistant strains, substantially decreases the time to MDR-GN predominance. The model implies that when MDR-GN strains evolve into strains that are fitter than susceptible strains, a reduction in antimicrobial exposure may not result in a decrease of MDR-GN, since the absence of selec- tive antimicrobial pressure would no longer favor susceptible strains. The model also implies that antimicrobial cycling may promote the emergence of MDR-GN.

Antibiotic Inducibility of the MexXY Multidrug Efflux System of Pseudomonas aeruginosa : Involvement of the Antibiotic-Inducible PA5471 Gene Product

The MexXY components of the MexXY-OprM multidrug efflux system of Pseudomonas aeruginosa are encoded by a MexZ repressor-regulated operon that is inducible by antibiotics that target the ribosome. Mutant strains disrupted in a gene, PA5471, were shown to be compromised for drug-inducible mexXY expression and, therefore, MexXY-OprM-mediated antimicrobial resistance. The PA5471 gene was inducible by the same ribosome-targeting agents that induce mexXY expression. Moreover, vector-driven expression of cloned PA5471 was sufficient to promote mexXY expression and MexXY-mediated resistance in the absence of antibiotic exposure, consistent with PA5471 directly or indirectly activating mexXY expression following its own upregulation in response to antibiotics. The requirement for PA5471 for mexXY expression and antimicrobial resistance was, however, obviated in mutants lacking the MexZ repressor of mexXY expression, suggesting that PA5471 directly or indirectly modulates MexZ activity in effecting mexXY expression. While the recruitment of PA5471 and MexXY in response to ribosome disruption by antimicrobials is consistent with their genes playing a role in protecting cells from the adverse consequences of disrupting the translation process, reminiscent of trans-translation, these genes appear to operate independently in their contribution to resistance: mutants defective in trans-translation showed a much more modest (twofold) decrease in resistance to ribosome-targeting agents than those lacking PA5471 or MexXY, and this decrease was observed whether functional PA5471/MexXY was present or not.