Fluoroquinolone Nonsusceptibility Research Articles

Estimating the subnational prevalence of antimicrobial resistant Salmonella enterica serovars Typhi and Paratyphi A infections in 75 endemic countries, 1990-2019: a modelling study.

Enteric fever, a systemic infection caused by Salmonella enterica serovars Typhi and Paratyphi A, remains a major cause of morbidity and mortality in low-income and middle-income countries. Enteric fever is preventable through the provision of clean water and adequate sanitation and can be successfully treated with antibiotics. However, high levels of antimicrobial resistance (AMR) compromise the effectiveness of treatment. We provide estimates of the prevalence of AMR S Typhi and S Paratyphi A in 75 endemic countries, including 30 locations without data. We used a Bayesian spatiotemporal modelling framework to estimate the percentage of multidrug resistance (MDR), fluoroquinolone non-susceptibility (FQNS), and third-generation cephalosporin resistance in S Typhi and S Paratyphi A infections for 1403 administrative level one districts in 75 endemic countries from 1990 to 2019. We incorporated data from a comprehensive systematic review, public health surveillance networks, and large multicountry studies on enteric fever. Estimates of the prevalence of AMR and the number of AMR infections (based on enteric fever incidence estimates by the Global Burden of Diseases study) were produced at the country, super-region, and total endemic area level for each year of the study. We collated data from 601 sources, comprising 184 225 isolates of S Typhi and S Paratyphi A, covering 45 countries over 30 years. We identified a decline of MDR S Typhi in south Asia and southeast Asia, whereas in sub-Saharan Africa, the overall prevalence increased from 6·0% (95% uncertainty interval 4·3-8·0) in 1990 to 72·7% (67·7-77·3) in 2019. Starting from low levels in 1990, the prevalence of FQNS S Typhi increased rapidly, reaching 95·2% (91·4-97·7) in south Asia in 2019. This corresponded to 2·5 million (1·5-3·8) MDR S Typhi infections and 7·4 million (4·7-11·3) FQNS S Typhi infections in endemic countries in 2019. The prevalence of third-generation cephalosporin-resistant S Typhi remained low across the whole endemic area over the study period, except for Pakistan where prevalence of third-generation cephalosporin resistance in S Typhi reached 61·0% (58·0-63·8) in 2019. For S Paratyphi A, we estimated low prevalence of MDR and third-generation cephalosporin resistance in all endemic countries, but a drastic increase of FQNS, which reached 95·0% (93·7-96·1; 3·5 million [2·2-5·6] infections) in 2019. This study provides a comprehensive and detailed analysis of the prevalence of MDR, FQNS, and third-generation cephalosporin resistance in S Typhi and S Paratyphi A infections in endemic countries, spanning the last 30 years. Our analysis highlights the increasing levels of AMR in this preventable infection and serves as a resource to guide urgently needed public health interventions, such as improvements in water, sanitation, and hygiene and typhoid fever vaccination campaigns. Fleming Fund, UK Department of Health and Social Care; Wellcome Trust; and Bill and Melinda Gates Foundation.

Risk Factors for Recurrence of Community-Onset Urinary Tract Infections Caused by Extended-Spectrum Cephalosporin-Resistant Enterobacterales.

Extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) are an increasingly important cause of community-onset urinary tract infections (UTIs), including recurrent infections. We evaluated risk factors for recurrence among patients with community-onset ESCrE UTI. This retrospective cohort study included adults with community-onset ESCrE UTI in the Duke University Health System from April 2018 through December 2021. ESCrE UTI recurrence by the same species was assessed 14-180 days (ie, 6 months) after completion of antibiotic treatment. We evaluated the relationships between candidate risk factors and time to recurrence using Cox proportional hazards regression models. Among 1347 patients with community-onset ESCrE UTI, 202 (15.0%) experienced recurrent infection during the 6-month follow-up period. Independent risk factors for recurrence included neurogenic bladder (adjusted hazard ratio [aHR], 1.8 [95% confidence interval {CI}, 1.2-2.6]; P = .005), prior history of UTI (aHR, 2.4 [95% CI, 1.7-3.3]; P < .001), and fluoroquinolone nonsusceptibility of the index UTI (aHR, 1.5 [95% CI, 1.1-2.1]; P = .02). Klebsiella pneumoniae infection was associated with recurrence in univariate analysis (HR, 1.6 [95% CI, 1.1-2.1]; P = .007) but not multivariate analysis (aHR, 1.4 [95% CI, 1.0-1.9]; P = .06). Inappropriate initial or definitive antibiotic therapy was not predictive of ESCrE UTI recurrence. Recurrence of community-onset ESCrE UTI was common and associated with several patient and pathogen-level risk factors. Future studies should evaluate microbial risk factors for recurrence and improve the management of ESCrE UTI.

Estimating the effect of vaccination on antimicrobial-resistant typhoid fever in 73 countries supported by Gavi: a mathematical modelling study

SummaryBackgroundMultidrug resistance and fluoroquinolone non-susceptibility (FQNS) are major concerns for the epidemiology and treatment of typhoid fever. The 2018 prequalification of the first typhoid conjugate vaccine (TCV) by WHO provides an opportunity to limit the transmission and burden of antimicrobial-resistant typhoid fever.MethodsWe combined output from mathematical models of typhoid transmission with estimates of antimicrobial resistance from meta-analyses to predict the burden of antimicrobial-resistant typhoid fever across 73 lower-income countries eligible for support from Gavi, the Vaccine Alliance. We considered FQNS and multidrug resistance separately. The effect of vaccination was predicted on the basis of forecasts of vaccine coverage. We explored how the potential effect of vaccination on the prevalence of antimicrobial resistance varied depending on key model parameters.FindingsThe introduction of routine immunisation with TCV at age 9 months with a catch-up campaign up to age 15 years was predicted to avert 46–74% of all typhoid fever cases in 73 countries eligible for Gavi support. Vaccination was predicted to reduce the relative prevalence of antimicrobial-resistant typhoid fever by 16% (95% prediction interval [PI] 0–49). TCV introduction with a catch-up campaign was predicted to avert 42·5 million (95% PI 24·8–62·8 million) cases and 506 000 (95% PI 187 000–1·9 million) deaths caused by FQNS typhoid fever, and 21·2 million (95% PI 16·4–26·5 million) cases and 342 000 (95% PI 135 000–1·5 million) deaths from multidrug-resistant typhoid fever over 10 years following introduction.InterpretationOur results indicate the benefits of prioritising TCV introduction for countries with a high avertable burden of antimicrobial-resistant typhoid fever.FundingThe Bill & Melinda Gates Foundation.

Estimating the Impact of Vaccination on Antimicrobial-Resistant Typhoid Fever in Gavi-73 Countries

Background: Multidrug resistance (MDR) and fluoroquinolone non-susceptibility (FQNS) are major concerns for the epidemiology and treatment of typhoid fever. The recent development and licensure of typhoid conjugate vaccines (TCVs) provide an opportunity to limit the transmission and burden of antimicrobial-resistant (AMR) typhoid fever. Methods: We combined output from mathematical models of typhoid transmission with estimates of antimicrobial resistance to predict the burden of AMR typhoid fever across Gavi-73 countries. We considered FQNS and MDR separately. The impact of vaccination was predicted based on forecasts of vaccine coverage. We explored how the potential impact of vaccination on the proportion of cases that were AMR varied depending on key model parameters. Findings: The introduction of routine immunization with TCV at 9 months of age with a catch-up campaign to 15 years of age was predicted to avert 46-74% of all typhoid fever cases in Gavi-73 countries. Vaccination was predicted to reduce the relative prevalence of AMR typhoid fever by 16% (95% prediction interval (PI): 0-49%). TCV introduction with a catch-up campaign was predicted to avert 42.5 million (95% PI: 24.8-62.8 million) cases and 506,000 (95% PI: 187,000-1.9 million) deaths due to FQNS typhoid fever and 21.2 million (95% PI: 16.4-26.5 million) cases and 342,000 (95% PI: 135,000-1.5 million) deaths from MDR typhoid fever over 10 years following introduction. Interpretation: Our results indicate the benefits of prioritizing TCV introduction for countries with a high avertable burden of FQNS and MDR typhoid fever. Funding: The Bill & Melinda Gates Foundation. Declaration of Interest: AJP chairs the UK Department of Health’s (DoH) Joint Committee on Vaccination and Immunisation (JCVI) and and is a member of the World Health Organization’s (WHO) Strategic Advisory Group of Experts. VEP has received reimbursement from Merck and Pfizer for travel expenses to Scientific Input Engagements unrelated to the subject of this manuscript and is a member of the World Health Organization’s (WHO) Immunization and Vaccine-related Implementation Research Advisory Committee. The views expressed in this manuscript are those of the authors and do not necessarily reflect the views of the JCVI, the DoH, or the WHO.

Antimicrobial Resistance in Typhoidal Salmonella: Surveillance for Enteric Fever in Asia Project, 2016-2019.

BackgroundClinicians have limited therapeutic options for enteric as a result of increasing antimicrobial resistance, and therefore typhoid vaccination is recommended as a preventive measure. As a part of the Surveillance for Enteric Fever in Asia Project (SEAP), we investigated the extent measured the burden of antimicrobial resistance (AMR) among confirmed enteric fever cases in Bangladesh, Nepal, and Pakistan.MethodsFrom September 2016–September 2019, SEAP recruited study participants of all age groups from its outpatient, inpatient, hospital laboratory, laboratory network, and surgical sites who had a diagnosis of febrile illness that was either suspected or blood culture confirmed for enteric fever. Antimicrobial resistance of isolates was determined by disc diffusion using Clinical and Laboratory Standard Institute cut-off points. We reported the frequency of multidrug resistance (MDR)(resistance to ampicillin, cotrimoxazole, and chloramphenicol), extensive drug resistance (XDR) (MDR plus non-susceptible to fluoroquinolone and any 3rd generation cephalosporins), and fluoroquinolone (FQ) and azithromycin non-susceptibility.ResultsWe enrolled 8,705 blood culture confirmed enteric fever cases: 4,873 (56%) from Bangladesh, 1,602 (18%) from Nepal and 2,230 (26%) from Pakistan. Of these, 7,591 (87%) were Salmonella Typhi and 1114 (13%) were S. Paratyphi. MDR S. Typhi was identified in 17% (701/4065) of isolates in Bangladesh, and 1% (19/1342) in Nepal. In Pakistan, 16 % (331/2084) of S. Typhi isolates were MDR, and 64% (1319/2074) were XDR. FQ nonsusceptibility among S. Typhi isolates was 98% in Bangladesh, 87% in Nepal, and 95% in Pakistan. Azithromycin non-susceptibility was detected in 77 (2%) in Bangladesh, 9 (.67%) in Nepal and 9 (.59%) isolates in Pakistan. In Pakistan, three (2%) S. Paratyphi isolates were MDR; no MDR S. Paratyphi was reported from Bangladesh or Nepal.ConclusionsAlthough AMR against S. Paratyphi was low across the three countries, there was widespread drug resistance among S. Typhi, including FQ non-susceptibility and the emergence of XDR S. Typhi in Pakistan, limiting treatment options. As typhoid conjugate vaccine (TCV) is rolled out, surveillance should continue to monitor changes in AMR to inform policies and to monitor drug resistance in S. Paratyphi, for which there is no vaccine.

Antimicrobial Nonsusceptibility Among Invasive MRSA USA300 Strains by Healthcare Exposure, Three Sites, 2005–2016

Background: Incidence of community-associated (CA) and healthcare-associated, community-onset (HACO) USA300 methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections has remained unchanged in recent years. Traditionally considered a CA strain, USA300 is increasingly associated with healthcare settings. We examined whether antimicrobial nonsusceptibility among USA300 strains could distinguish epidemiologic class (community vs hospital), and whether divergences in susceptibility were occurring over time. Methods: We used data on invasive MRSA infections from active, population, and laboratory-based surveillance during 2005–2016 from 11 counties in 3 states. Invasive cases were defined as MRSA isolation from a normally sterile site in a surveillance area resident. Cases were considered hospital-onset (HO) if the culture was obtained &gt;3 days after hospitalization and HACO if ≥1 of the following risk factors was present: hospitalization, surgery, dialysis, or residence in a long-term care facility in the past year; or central vascular catheter ≤2 days before culture. Otherwise, cases were considered CA. Sites submitted a convenience sample of clinical MRSA isolates for molecular typing and antimicrobial susceptibility testing. Molecular typing was performed by pulsed-field gel electrophoresis until 2008, when typing was inferred using a validated algorithm based on molecular characteristics. Reference broth microdilution was performed for 8 antimicrobials and interpreted based on CLSI interpretive criteria. We compared USA300 nonsusceptibility for HO and CA isolates. For antimicrobials with &gt;5% nonsusceptibility and for which HO isolates had greater nonsusceptibility than CA isolates, we compared nonsusceptibility for HACO and CA and analyzed annual trends in nonsusceptibility within each epidemiologic class (ie, CA, HACO, and HO) using linear regression. Results: Of 17,947 MRSA cases during 2005–2016, isolates were available for 6,685 (37%), and 2,120 were USA300 (34% CA, 52% HACO, 14% HO). HO isolates had more nonsusceptibility than CA isolates to gentamicin (2.2% vs 0.6%; P = .03), levofloxacin (47.8% vs 39.7%; P = .02), rifampin (3.7 vs 1.1%; P = .01), and trimethoprim-sulfamethoxazole (3.4% vs 0.6%; P = .04). HACO isolates also had more nonsusceptibility than CA isolates to levofloxacin (50.9% vs 39.7%; P &lt; .01). Levofloxacin nonsusceptibility increased during 2005–2016 for HACO and CA isolates (P &lt; .01), but not among HO isolates (P = .36) (Fig. 1). Conclusions: Overall, nonsusceptibility across drugs cannot distinguish USA300 isolates causing HO versus CA disease. Although HO isolates had higher levofloxacin nonsusceptibility than CA and HACO isolates early on, USA300 MRSA HACO isolates now have levofloxacin nonsusceptibility most similar to that of HO isolates. Further study could help to explore whether increases in fluoroquinolone nonsusceptibility among CA and HACO cases may be contributing to the persistence of USA300 strains.Disclosures: NoneFunding: None

Clinical and Genetic Characteristics of Extended-Spectrum Beta-Lactamase–Producing Enterobacteriaceae Among Canadian Children

Background: Infections with extended-spectrum β-lactamase–producing Enterobacteriaceae (ESBL-E) in nonoutbreak settings have not demonstrated the presence of dominant strains. Our objective was to determine the incidence, clinical characteristics, and genetic characteristics of ESBL-E infections among a group of Canadian children. Methods: From 2012 through 2017, patients aged ≤18 years with first-episode ESBL-E infections who presented at a pediatric center were reviewed. All clinical isolates were phenotypically identified in the laboratory as ESBL-producers. Demographic and clinical data were collected, including comorbid conditions, presence of devices, and previous antibacterial exposure. Community-associated infection was defined as a positive culture from a sterile site within the first 48 hours of hospital admission and no healthcare exposure during the preceding year. Isolates were sent to the Public Health Ontario Laboratory for whole-genome sequencing. Multilocus sequence typing was used to determine clonal relationship. Results: During the study period, 102 patients were identified with first-episode ESBL-E infection, and the proportion of ESBL-E isolates among all clinical isolates of E. coli and Klebsiella spp increased from 0.6% to 2.6% between 2012 and 2017, respectively (P = .001). The median age was 1 year (interquartile range, 0.8–5 years). Women comprised 66% of cases. No comorbid conditions were noted among 58 patients (57%), and 24% had previous antibiotic exposure, most frequently a cephalosporin (16%). ESBL-E was most frequently isolated in the urine (91%) and least frequently in the blood (2.2%) and was predominantly Escherichia coli (90%). Infection was most frequently diagnosed in the outpatient setting (61%); there were 11 healthcare-associated infections. Whole-genome sequencing of ESBL-E isolates revealed predominance of blaCTX-M-15 (63 isolates, 62%) and blaCTX-M-27 (16%) genes, and sequence type (ST) 131 (41%). Mutations conferring fluoroquinolone nonsusceptibility were noted among 62 isolates (61%), most frequently associated with ST131 (38 of 62 isolates, 61%) and among all 5 isolates with ST1193, an emerging multidrug-resistant E. coli clone. In addition, 15 patients had recurrence of ESBL-E infection at median of 113 days (IQR, 26–208); blaCTX-M-27 was found in 33% of recurrent infections compared to 12% of primary infections (P = 0.045). Conclusions: This study is the first in Canada to provide whole-genome sequencing data regarding ESBL-E in a pediatric population. The gene blaCTX-M-15 and ST131 clone were predominant. More than 60% of infections were community associated and demonstrated cross resistance to fluoroquinolones. With 76% of infections in antibiotic-naïve children, ESBL-E is a public health concern, and a One Health approach is critical to understanding the epidemiology and curbing the spread of multidrug-resistant Enterobacteriaceae.Funding: NoneDisclosures: None

Typhoid Fever in the US Pediatric Population, 1999-2015: Opportunities for Improvement.

Typhoid fever in the United States is acquired primarily through international travel by unvaccinated travelers. There is currently no typhoid vaccine licensed in the United States for use in children <2 years. We reviewed Salmonella enterica serotype Typhi infections reported to the Centers for Disease Control and Prevention (CDC) and antimicrobial-resistance data on Typhi isolates in CDC's National Antimicrobial Resistance Monitoring System from 1999 through 2015. 5131 cases of typhoid fever were diagnosed and 5004 Typhi isolates tested for antimicrobial susceptibility. Among 1992 pediatric typhoid fever patients, 1616 (81%) had traveled internationally within 30 days of illness onset, 1544 (81%) of 1906 were hospitalized (median duration, 6 days; range, 0-50), and none died. Forty percent (799) were <6 years old; 12% were <2 years old. Based on age and travel destination, 1435 (83%) of 1722 pediatric patients were vaccine-eligible; only 68 (5%) of 1361 were known to be vaccinated. Of 2003 isolates tested for antimicrobial susceptibility, 1216 (61%) were fluoroquinolone-nonsusceptible, of which 272 (22%) were also resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole (multidrug-resistant [MDR]). All were susceptible to ceftriaxone and azithromycin. MDR and fluoroquinolone-nonsusceptible isolates were more common in children than adults (16% vs 9%, P < .001, and 61% vs 54%, P < .001, respectively). Fluoroquinolone nonsusceptibility was more common among travel-associated than domestically acquired cases (70% vs 17%, P < .001). Approximately 95% of currently vaccine-eligible pediatric travelers were unvaccinated, and antimicrobial-resistant infections were common. New public health strategies are needed to improve coverage with currently licensed vaccines. Introduction of an effective pretravel typhoid vaccine for children <2 years could reduce disease burden and prevent drug-resistant infections.

Drug-resistant enteric fever worldwide, 1990 to 2018: a systematic review and meta-analysis

BackgroundAntimicrobial resistance (AMR) is an increasing threat to global health. There are > 14 million cases of enteric fever every year and > 135,000 deaths. The disease is primarily controlled by antimicrobial treatment, but this is becoming increasingly difficult due to AMR. Our objectives were to assess the prevalence and geographic distribution of AMR in Salmonella enterica serovars Typhi and Paratyphi A infections globally, to evaluate the extent of the problem, and to facilitate the creation of geospatial maps of AMR prevalence to help targeted public health intervention.MethodsWe performed a systematic review of the literature by searching seven databases for studies published between 1990 and 2018. We recategorised isolates to allow the analysis of fluoroquinolone resistance trends over the study period. The prevalence of multidrug resistance (MDR) and fluoroquinolone non-susceptibility (FQNS) in individual studies was illustrated by forest plots, and a random effects meta-analysis was performed, stratified by Global Burden of Disease (GBD) region and 5-year time period. Heterogeneity was assessed using the I2 statistics. We present a descriptive analysis of ceftriaxone and azithromycin resistance.FindingsWe identified 4557 articles, of which 384, comprising 124,347 isolates (94,616 S. Typhi and 29,731 S. Paratyphi A) met the pre-specified inclusion criteria. The majority (276/384; 72%) of studies were from South Asia; 40 (10%) articles were identified from Sub-Saharan Africa. With the exception of MDR S. Typhi in South Asia, which declined between 1990 and 2018, and MDR S. Paratyphi A, which remained at low levels, resistance trends worsened for all antimicrobials in all regions. We identified several data gaps in Africa and the Middle East. Incomplete reporting of antimicrobial susceptibility testing (AST) and lack of quality assurance were identified.InterpretationDrug-resistant enteric fever is widespread in low- and middle-income countries, and the situation is worsening. It is essential that public health and clinical measures, which include improvements in water quality and sanitation, the deployment of S. Typhi vaccination, and an informed choice of treatment are implemented. However, there is no licenced vaccine for S. Paratyphi A. The standardised reporting of AST data and rollout of external quality control assessment are urgently needed to facilitate evidence-based policy and practice.Trial registrationPROSPERO CRD42018029432.

Prediction of Fluoroquinolone Susceptibility Directly from Whole-Genome Sequence Data by Using Liquid Chromatography-Tandem Mass Spectrometry To Identify Mutant Genotypes.

Fluoroquinolone resistance in Gram-negative bacteria is multifactorial, involving target site mutations, reductions in fluoroquinolone entry due to reduced porin production, increased fluoroquinolone efflux, enzymes that modify fluoroquinolones, and Qnr, a DNA mimic that protects the drug target from fluoroquinolone binding. Here we report a comprehensive analysis, using transformation and in vitro mutant selection, of the relative importance of each of these mechanisms for fluoroquinolone nonsusceptibility using Klebsiella pneumoniae as a model system. Our improved biological understanding was then used to generate 47 rules that can predict fluoroquinolone susceptibility in K. pneumoniae clinical isolates. Key to the success of this predictive process was the use of liquid chromatography-tandem mass spectrometry to measure the abundance of proteins in extracts of cultured bacteria, identifying which sequence variants seen in the whole-genome sequence data were functionally important in the context of fluoroquinolone susceptibility.

Clinically Important Resistance among Salmonella enterica Serotype Typhi Isolates—United States, 2003–2015

Background Salmonella Typhi (Typhi) causes typhoid fever, accounting for an estimated 5,700 illnesses and 623 hospitalizations per year in the United States. Most infections are acquired during travel to regions outside the United States where typhoid fever is prevalent and antimicrobial resistance is a problem. Fluoroquinolones (e.g., ciprofloxacin) are considered the treatment of choice for susceptible Typhi infections due to their superior ability to concentrate intracellularly and in bile, however, nonsusceptibility has been associated with treatment failure or delayed response. Azithromycin and ceftriaxone are treatment options. We describe antimicrobial susceptibility among Typhi isolates in the United States and the implications for management.MethodsThe National Antimicrobial Resistance Monitoring System at CDC conducts susceptibility testing on all Typhi isolates submitted by public health laboratories. We used broth microdilution to determine minimum inhibitory concentrations (MICs) to agents representing 9 antimicrobial classes and categorized isolates according to criteria from the Clinical and Laboratory Standards Institute. We defined ciprofloxacin nonsusceptibility as MIC ≥0.12 μg/mL, ciprofloxacin resistance as MIC ≥1, azithromycin resistance as MIC ≥32, and ceftriaxone resistance as MIC ≥4.ResultsFrom 2003–2015, isolates were tested from 4,550 patients; 2,760 (61%) were ciprofloxacin nonsusceptible, 4% were ciprofloxacin resistant. One isolate was azithromycin resistant and none were ceftriaxone resistant. Ciprofloxacin nonsusceptibility increased from 39% in 2003 to 66% in 2015; resistance increased from 0.3% to 8%. Median age of patients was 23 years (range 1–99 years), 53% were male, most were from the Northeast (33%) or the West (29%), and 74% had an isolate from blood.ConclusionTwo thirds of Typhi isolates exhibited ciprofloxacin nonsusceptibility, which has increased over the last decade, and full resistance is increasing. Clinicians should be aware of high rates of fluoroquinolone nonsusceptibility when selecting empiric therapy and should tailor antimicrobial treatment to susceptibility results when feasible. Azithromycin and ceftriaxone remain important treatment options.Disclosures All authors: No reported disclosures.

Effect of prior receipt of antibiotics on the pathogen distribution and antibiotic resistance profile of key Gram-negative pathogens among patients with hospital-onset urinary tract infections

BackgroundThis retrospective cohort study characterized the impact of prior antibiotic exposure on distribution and nonsusceptibility profiles of Gram-negative pathogens causing hospital-onset urinary tract infections (UTI).MethodsHospital patients with positive urine culture for Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and other Enterobacteriaceae ≥3 days after hospital admission were included. Assessment outcomes included the distribution of bacteria in urine cultures, antibiotic susceptibility patterns, and the effect of prior antibiotic exposure, defined as 0, 1, or ≥2 prior antibiotics, on the distribution and antibiotic susceptibility profiles of the Gram-negative organisms.ResultsThe most commonly isolated pathogens from 5574 unique UTI episodes (2027 with and 3547 without prior antibiotic exposure) were E. coli (49.5%), K. pneumoniae (17.1%), and P. aeruginosa (8.2%). P. aeruginosa was significantly more commonly isolated in patients with ≥2 prior antibiotic exposures (12.6%) compared with no exposure (8.2%; p = 0.036) or 1 prior exposure (7.9%; p = 0.025). Two or more prior antibiotic exposures were associated with slightly higher incidences of fluoroquinolone nonsusceptibility, multidrug resistance, and extended-spectrum β-lactamase phenotype compared with 0 or 1 exposure, suggesting an increased risk for resistant Gram-negative pathogens among hospital patients with urinary tract infections occurring ≥3 days after admission.ConclusionsClinicians should critically assess prior antibiotic exposure when selecting empirical therapy for patients with hospital-onset urinary tract infections caused by Gram-negative pathogens.

Regional variations in fluoroquinolone non-susceptibility among Escherichia coli bloodstream infections within the Veterans Healthcare Administration.

ObjectivesWe sought to define regional variations in fluoroquinolone non-susceptibility (FQ-NS) among bloodstream isolates of Escherichia coli across the Veterans Health Administration (VHA) in the United States.MethodsWe analyzed a retrospective cohort of patients managed at 136 VHA hospitals who had a blood culture positive for E.coli between 2003 and 2013. Hospitals were classified based on US Census Divisions, and regional variations in FQ-NS were analyzed.ResultsTwenty-four thousand five hundred twenty-three unique E.coli bloodstream infections (BSIs) were identified between 2003 and 2013. 53.9 % of these were community-acquired, 30.7 % were healthcare-associated, and 15.4 % were hospital-onset BSIs. The proportion of E.coli BSIs with FQ-NS significantly varied across US Census Divisions (p < 0.001). During 2003–2013, the proportion of E.coli BSIs with FQ-NS was highest in the West South-Central Division (32.7 %) and lowest in the Mountain Division (20.0 %). Multivariable analysis showed that there were universal secular trends towards higher FQ-NS rates (p < 0.001) with significant variability of slopes across US Census Divisions (p < 0.001).ConclusionThere has been a universal increase in FQ-NS among E.coli BSIs within VHA, but the rate of increase has significantly varied across Census Divisions. The reasons for this variability are unclear. These findings reinforce the importance of using local data to develop and update local antibiograms and antibiotic-prescribing guidelines.

High prevalence of fluoroquinolone-nonsusceptible Streptococcus pyogenes emm12 in Taiwan

Fluoroquinolone-nonsusceptible Streptococcus pyogenes has rapidly emerged in several countries. The aim of this study was to survey the epidemiology and molecular characteristics of fluoroquinolone-nonsusceptible S. pyogenes in Taiwan. A total of 350 consecutive S. pyogenes isolates were collected between January 2005 and December 2012, including 152 (43.4%) invasive and 198 (56.6%) noninvasive isolates. Thirty-nine isolates (11.1%) of S. pyogenes were nonsusceptible to fluoroquinolones, including one emm1/ST28, 4 emm4/ST39, 33 emm12/ST36, and 1 emm87/ST62. Of all the isolates, emm12 (50%) demonstrated the highest prevalence of fluoroquinolone nonsusceptibility. Alterations of Ser79Phe and Ala12Val in ParC were the most frequently mutations in fluoroquinolone-nonsusceptible S. pyogenes isolates. There were no amino acid substitutions in GyrB, and 1 emm87 isolate exhibited 3 nonsynonymous mutations in ParE. Our study reveals the emergence of fluoroquinolone-nonsusceptible S. pyogenes emm12/ST36 in Taiwan. Regular surveillance of fluoroquinolone susceptibility in S. pyogenes is suggested.

High frequency of fluoroquinolone- and macrolide-resistant streptococci among clinically isolated group B streptococci with reduced penicillin susceptibility

Recently several clinical isolates of Streptococcus agalactiae [also known as group B Streptococcus (GBS)] that have acquired reduced penicillin susceptibility (PRGBS) by amino acid substitutions in the penicillin-binding protein 2X have emerged. The frequency of fluoroquinolone (FQ)- and macrolide-resistant streptococci among PRGBS is not yet known. Fifty-seven GBS [19 PRGBS and 38 penicillin-susceptible GBS (PSGBS)], isolated from different medical institutions in Japan, were studied. For GBS, the MICs of penicillin G, levofloxacin and erythromycin were determined using the agar dilution method. Nineteen PRGBS were previously confirmed as genetically diverse streptococci by PFGE. Further, the mechanisms underlying penicillin, FQ and macrolide non-susceptibility/resistance were analysed. The frequency of non-susceptibility to FQs among PSGBS was 18.4% (7/38), whereas that among PRGBS was 100% (19/19). The frequency of resistance to erythromycin among PSGBS was 7.9% (3/38), while that among PRGBS was 47.4% (9/19). Statistical significance was determined using Fisher's exact test between reduced penicillin susceptibility and FQ non-susceptibility (P ≤ 0.0001) and macrolide resistance (P=0.0012). The resistance/non-susceptibility mechanisms among PRGBS were diverse, suggesting that the PRGBS examined were not clonal. PRGBS isolates tend to show resistance to FQs and/or macrolides. Because the drug choice for treating these multidrug-resistant GBS is more limited than that for usual GBS, these strains may present future public health challenges.

Trends in Antimicrobial Resistance of Neisseria gonorrhoeae Isolated From Korean Patients From 2000 to 2006

The recent emergence and spread of antimicrobial-resistant Neisseria gonorrhoeae has compromised treatment and control of gonorrhea. We determined recent trends in antimicrobial susceptibility of the isolates, analyzed recent use of antigonococcal agents, and investigated the relationship between fluoroquinolone nonsusceptibility and amino acid substitutions within the fluoroquinolone resistance-determining regions in Korea. The antimicrobial susceptibilities of 977 isolates of N. gonorrhoeae collected from 2000 to 2006 in Korea were determined with penicillin, ceftriaxone, spectinomycin, tetracycline, and ciprofloxacin disks. Some of the randomly selected isolates were tested by the Clinical and Laboratory Standards Institute agar dilution method, to determine subtle changes in susceptibility to the above antibiotics and cefixime. β-lactamase was detected using a cefinase disk. All of the isolates exhibited plasmid- or chromosomally mediated resistance to penicillin; however, the proportions of penicillinase-producing N. gonorrhoeae decreased rapidly from 64% in 2000 to 21% in 2006. All isolates were susceptible to third-generation cephalosporins, except for 1 isolate that was not susceptible to cefixime. The proportion of ciprofloxacin-resistant isolates increased from 26% in 2000 to 83% in 2006. Of 7 substitution types, 5 (Ser-91-Phe in Gyrase A (GyrA), Ser-87-Arg in ParC subunit of topoisomerase IV (ParC); Ser-91-Phe and Asp-95-Ala in GyrA, and Ser-87-Asn in ParC; Ser-91-Phe and Asp-95-Gly in GyrA, and Asp-86-Asn in ParC; Ser-91-Tyr in GyrA; Ser-91-Phe in GyrA, and Asp-86-Asn in ParC) were new ones not identified in our 2004 study. All isolates were susceptible to spectinomycin. About half of the patients in our current study (52.6%-58.1%, depending on the year) received spectinomycin treatment. Majorities were resistant to tetracycline, and the rate of highly tetracycline-resistant N. gonorrhoeae increased from 3% in 2000 to 9% in 2006. The incidence of penicillinase-producing N. gonorrhoeae declined significantly, but none of the isolates were susceptible to penicillin G. All isolates were susceptible to spectinomycin, in contrast majority were resistant to tetracycline. Inappropriate use of fluoroquinolone was frequent. The minimum inhibitory concentrations of ceftriaxone were within the susceptible range for all isolates, but those of cefixime were slightly higher, and it was 0.5 μg/mL (nonsusceptible) for 1 isolate.

Fluoroquinolone-Resistant Pneumococci: Maybe Resistance Isn't Futile?

By 2000, the emergence of fluoroquinolone-resistant pneumococci in North America seemed imminent. The prevalence of fluoroquinolone nonsusceptibility, although <1% worldwide, was high in many countries, including Spain (7%), Hong Kong (14.3%), South Korea (2.9%), Sri Lanka (9.5%), The Philippines (9.1%), and South Korea (6.5%) [1-5]. In Canada, Chen et al. [6] found that the overall prevalence of ciprofloxacin-resistant pneumococci (MIC, -4 ALg/mL) had increased from 0% in 1993 to 1.7% in 1997-1998 (P = .01). In adults, the prevalence increased from 1.5% to 2.9%. Linares et al. [7] reported an increase in the prevalence of ciprofloxacin-resistant pneumococci from 0.9% in 1991-1992 to 3% in 1997-1998 in Spain. In Hong Kong, Ho et al. [8] documented an increase in the prevalence of levofloxacin-nonsusceptible isolates (MIC, :4 tcg/mL) from 5.5% in 1998 to 13.3% in 2000.