Changes In Resistance Rate Research Articles

Modelling the implementation of narrow versus broader spectrum antibiotics in the empiric treatment of E. coli bacteraemia

The implementation of new antimicrobial resistance stewardship programs is crucial in optimizing antibiotic use. However, prescription choices can be difficult during empiric therapy; clinicians must balance the survival benefits of broader spectrum antibiotics with associated increases in resistance. The aim of this study was to evaluate the overall feasibility of switching to narrow spectrum antibiotics during the empiric treatment of E. coli bacteraemia by quantifying changes in resistance rates, antibiotic usage, and mortality using a deterministic state-transition model. Three unique model scenarios (A, B, and C), each representing a progressively broader spectrum empiric treatment regimen, were used to compare outcomes at 5 years. We show that the empiric use of the narrowest spectrum (first-line) antibiotics can lead to reductions in resistance to second-line antibiotics and the use of third-line antibiotics, but they also lead to increases in resistance to first-line therapy and higher mortality. Crucially, we find that shortening the duration of empiric and overall treatment, as well as reducing the baseline mortality rate, are important for increasing the feasibility of switching to narrow spectrum antibiotics in the empiric treatment of E. coli bacteraemia. We provide a flexible model design to investigate optimal treatment approaches for other bacterial infections.

COVID-19 restrictions limited interactions of people and resulted in lowered E. coli antimicrobial resistance rates.

Antibiotic resistance is rising globally and is a major One Health problem. How much person-to-person transmission or 'contagion' contributes to the spread of resistant strains compared with antibiotic usage remains unclear. As part of its COVID-19 response, Australia introduced strict people movement restrictions in early 2020. Along with internal lockdown measures, movement of people into Australia from overseas was severely restricted. These circumstances provided a unique opportunity to examine the association of people movements with changes in resistance rates. Monthly resistance data on over 646 000 Escherichia coli urine isolates from 2016 till 2023 were modelled for statistical changes in resistance trends during pre-lockdown, lockdown and post-lockdown periods. Data were available for three clinical contexts (community, hospital and aged-care facilities). Data were also available for antibiotic usage volumes and movements of people into Australia. In 2020, arrivals into Australia decreased by >95%. Antibiotic community use fell by >20%. There were sharp falls in trend rates of resistance for all antibiotics examined after restrictions were instituted. This fall in trend rates of resistance persisted during restrictions. Notably, trend rates of resistance fell in all three clinical contexts. After removal of restrictions, an upsurge in trend rates of resistance was seen for nearly all antibiotics but with no matching upsurge in antibiotic use. Restricting the movement of people appeared to have a dramatic effect on resistance rates in E. coli. The resulting reduced person-to-person interactions seems more closely associated with changes in antibiotic resistance than antibiotic usage patterns.

Antibiotic Resistance Changes in Gram-Positive Bacteria from Urine Cultures: Development Analysis in a Health Area of South-East Spain.

This study analyzed the epidemiology and antibiotic susceptibility profile of significant bacteriuria and assessed the impact of adopting EUCAST criteria on antibiotic resistances. A systematic review was performed on publications in English or Spanish between 1 January 2010 and 30 June 2021 on the susceptibility of Gram-positive bacteria isolated in urinary samples in Europe. A retrospective descriptive study was also conducted on the results of 21,838 urine cultures with presumptive urinary tract infection (UTI) obtained during the past five years by the Department of Microbiology of the Virgen de las Nieves University Hospital (Granada, Spain). The activity of various antibiotics was determined, differentiated among various populations, and interpretations compared according to the application of EUCAST or CLSI criteria. Among 21,838 cases of significant bacteriuria, 27.69% were by Gram-positive bacteria, which were Enterococcus faecalis in 19.04% and Enterococcus faecium in 3.92%. The susceptibility profile remained stable for most antibiotics except for levofloxacin for E. faecalis and Staphylococcus aureus and nitrofurantoin for E. faecium. The resistance of Enterococcus spp. and Staphylococcus spp. to glycopeptides was exceptionally low in our setting. No significant difference in the prevalence of methicillin-resistant Staphylococcus aureus was observed between hospital (26.67%) and community (28.85%) samples. Resistances in our local setting remain stable and appear to be lower than reported in other studies. The adoption of EUCAST vs. CLSI criteria did not produce a general change in resistance rates. Findings suggest the need to revise certain empirical criteria, such as aminoglycoside synergy for Enterococcus and for community-origin S. aureus.

Distribution and antifungal resistance rate of yeast isolated from various samples

Objective: Yeast causes hospital-acquired infections at increasing rates, which can cause serious mortality, especially in patients with a suppressed immune system. This study aimed to determine the species distribution and antifungal resistance rates of yeast isolated in a hospital. Material and Methods: Isolated yeasts from clinical specimens of patients who received inpatient treatment in different clinics in our hospital between 1 December 2019 and 30 September 2020 were examined. In all of these isolates, species identification was made with an automated system in addition to classical methods. Additionally, the antifungal susceptibility of yeast against amphotericin B, flucytosine, Fluconazole, micafungin, caspofungin, and Voriconazole was investigated using an automated system. Results: In the study, yeasts isolated from 183 clinical samples, including 64 vagen, 62 blood, 28 urine, 12 wounds, eight tracheal aspirates, five peritoneal fluids, three catheters and one cerebrospinal fluid (CSF) samples were included. Of these isolates, 93 were Candida albicans (50,82%), 40 were Candida parapsilosis (21,86%), 17 were Candida tropicalis (9,29%), eight were Candida glabrata (4,37%), eight were Stephanoascus ciferrii (4,37%), five were Candida lusitaniae (2,19%), four were Candida famata (2,19%), four were Cryptococcus laurentii (2,19%) and four were Candida krusei ( 2,19%). Antifungal susceptibility testing was performed in 103 of the isolates. The highest resistance was found against Fluconazole, with 16.8%, and the lowest resistance was against flucytosine, with 2.2%. Antifungal resistance rates of Fluconazole, Voriconazole, amphotericin B, flucytosine, caspofungin and micafungin were found as 16.8%, 8.2%, 6.1%, 2.2%, 2.9% and 6.8% respectively. Conclusion: Due to the increasing frequency of fungal infections due to long-term hospitalization, it has been concluded that identifying the causative species and reporting the antifungal susceptibility status is important in monitoring the change in resistance rates and guiding the treatment.

National Surveillance of Tetracycline, Erythromycin, and Clindamycin Resistance in Invasive Streptococcus pyogenes: A Retrospective Study of the Situation in Spain, 2007-2020.

This work reports on antimicrobial resistance data for invasive Streptococcus pyogenes in Spain, collected by the 'Surveillance Program for Invasive Group A Streptococcus', in 2007-2020. emm typing was determined by sequencing. Susceptibility to penicillin, tetracycline, erythromycin, and clindamycin was determined via the E-test. tetM, tetO, msrD, mefA, ermB, ermTR, and ermT were sought by PCR. Macrolide-resistant phenotypes (M, cMLSB, and iMLSB) were detected using the erythromycin-clindamycin double-disk test. Resistant clones were identified via their emm type, multilocus sequence type (ST), resistance genotype, and macrolide resistance phenotype. Penicillin susceptibility was universal. Tetracycline resistance was recorded for 237/1983 isolates (12.0%) (152 carried only tetM, 48 carried only tetO, and 33 carried both). Erythromycin resistance was detected in 172/1983 isolates (8.7%); ermB was present in 83, mefA in 58, msrD in 51, ermTR in 46, and ermT in 36. Clindamycin resistance (methylase-mediated) was present in 78/1983 isolates (3.9%). Eight main resistant clones were identified: two that were tetracycline-resistant only (emm22/ST46/tetM and emm77/ST63/tetO), three that were erythromycin-resistant only (emm4/ST39/mefA-msrD/M, emm12/ST36/mefA-msrD/M, and emm28/ST52/ermB/cMLSB), and three that were tetracycline-erythromycin co-resistant (emm11/ST403/tetM-ermB/cMLSB, emm77/ST63/tetO-ermTR/iMLSB, and emm77/ST63/tetM-tetO-ermTR/iMLSB). Tetracycline, erythromycin, and clindamycin resistance rates declined between 2007 and 2020. Temporal variations in the proportion of resistant clones determined the change in resistance rates.

Prescription Patterns and Antibiotic Resistance Rates of Respiratory Tract Infections in a Saudi Tertiary Medical Centre

Objectives: Respiratory tract infections (RTIs) are a significant cause of hospitalization due to morbidity and mortality. The unwise use of antimicrobial agents in RTI management may contribute to the emergence of bacterial resistance. Therefore, we aimed to assess prescription patterns and antibiotic resistance among hospitalized patients with RTIs. Materials and Methods: This retrospective study included patients with any RTI who were hospitalized between 2016 and 2017. Antibiotics prescribed and changes in antibiotic resistance over time were evaluated. Results: The 405 included patients ranged in age from a few months old to over 65 years old. The most common clinical manifestations were fever (98% of patients) and sore throat (57.5%), followed by cough (46.7%) and dyspnea (27.2%). C-reactive protein was elevated in 43%. The most common diagnoses among all the patients were tonsillitis (43.2%), pharyngitis (36%), and pneumonia (23%). The most commonly isolated organisms were Haemophilus influenza (93.2%), Streptococcus pneumoniae (90.9%), Pseudomonas aeruginosa (84.1%), and Klebsiella pneumoniae (84.1%). Amoxicillin/clavulanate was mostly prescribed for upper RTIs, whereas levofloxacin was mostly prescribed for lower RTIs. Amoxicillin/clavulanate was the major antibiotic prescribed for pediatric patients, whereas geriatric patients (≥65 years) were mostly prescribed levofloxacin. No major changes in resistance rates were observed for amoxicillin/clavulanate, levofloxacin, or ciprofloxacin before (in 2015), during the study period (2016–2017), and after the study (2018). Conclusion: Amoxicillin/clavulanate and levofloxacin were the most commonly prescribed antibiotics, but resistance to these antibiotics did not increase over time. However, clinicians should make every attempt to collect cultures from patients with severe RTIs to rule out bacterial involvement.

Changes in antibiotic consumption, AMR and Clostridioides difficile infections in a large tertiary-care center following the implementation of institution-specific guidelines for antimicrobial therapy: A nine-year interrupted time series study.

BackgroundInstitution-specific guidelines (ISGs) within the framework of antimicrobial stewardship programs offer locally tailored decision support taking into account local pathogen and resistance epidemiology as well as national and international guidelines.ObjectivesTo assess the impact of ISGs for antimicrobial therapy on antibiotic consumption and subsequent changes in resistance rates and Clostridioides difficile infections (CDIs).MethodsThe study was conducted at the Leipzig University Hospital, a 1,451-bed tertiary-care medical center, and covered the years 2012 to 2020. Since 2014, ISGs were provided to optimize empirical therapies, appropriate diagnostics, and antimicrobial prophylaxis. We used interrupted time series analysis (ITSA) and simple linear regression to analyze changes in antimicrobial consumption, resistance and CDIs.ResultsOver the study period, 1,672,200 defined daily doses (DDD) of antibiotics were dispensed, and 85,645 bacterial isolates as well as 2,576 positive C. difficile cultures were collected. Total antimicrobial consumption decreased by 14% from 2012 to 2020, without clear impact of the deployment of ISGs. However, implementation of ISGs was associated with significant decreases in the use of substances that were rarely recommended (e.g., fluoroquinolones). Over the whole study period, we observed declining resistance rates to most antibiotic classes of up to 25% in Enterobacterales, staphylococci, and Pseudomonas aeruginosa. Switching from ceftriaxone to cefotaxime was associated with reduced resistance to third-generation cephalosporins. The number of CDI cases fell by 65%, from 501 in 2012 to 174 in 2020.ConclusionsWell-implemented ISGs can have a significant, immediate, and lasting impact on the prescription behavior. ISGs might thereby contribute to reduce resistance rates and CDI incidences in the hospital setting.

Changes of resistance rates in Pseudomonas aeruginosa strains are unrelated to antimicrobial consumption in ICU populations with invasive device-related infection

ObjectiveTo evaluate the relationship between antipseudomonal antibiotic consumption and each individual drug resistance rate in Pseudomonas aeruginosa strains causing ICU acquired invasive device-related infections (IDRI). DesignA post hoc analysis was made of the data collected prospectively from the ENVIN-HELICS registry. SettingIntensive Care Units participating in the ENVIN-UCI registry between the years 2007 and 2016 (3-month registry each year). PatientsPatients admitted for over 24h. Main variablesAnnual linear and nonlinear trends of resistance rates of P. aeruginosa strains identified in IDRI and days of treatment of each antipseudomonal antibiotic family per 1000 occupied ICU bed days (DOT) were calculated. ResultsA total of 15,095 episodes of IDRI were diagnosed in 11,652 patients (6.2% out of a total of 187,100). Pseudomonas aeruginosa was identified in 2095 (13.6%) of 15,432 pathogens causing IDRI. Resistance increased significantly over the study period for piperacillin-tazobactam (P<0.001), imipenem (P=0.016), meropenem (P=0.004), ceftazidime (P=0.005) and cefepime (P=0.015), while variations in resistance rates for amikacin, ciprofloxacin, levofloxacin and colistin proved nonsignificant. A significant DOT decrease was observed for aminoglycosides (P<0.001), cephalosporins (P<0.001), quinolones (P<0.001) and carbapenems (P<0.001). ConclusionsNo significant association was observed between consumption of each antipseudomonal antibiotic family and the respective resistance rates for P. aeruginosa strains identified in IDRI.

Changes in Antimicrobial Resistance of Urinary Tract Infections in Adult Patients over a 5-Year Period

Objectives: We aimed to determine the most common bacteria that cause urinary tract infections (UTIs), the rate of antibiotic resistance of these uropathogens, and the changes in resistance rates over the years for adult patients diagnosed with UTIs. Methods: We retrospectively reviewed urine cultures and antibiotic susceptibility results of patients >17 years of age from our outpatient clinic between 2014 and 2018. The most common uropathogens and their antibiotic resistance rates were identified in different age groups (18–39, 40–59, and ≥60 years) and with respect to gender and date of admission. In addition, the change in antibiotic resistance of Escherichia coli between 2014 and 2018 was also examined. Results: A total of 9,556 positive urine cultures were included. The most common uropathogen was E. coli, and its prevalence was higher in females than males (70.6 vs. 53.4%, respectively). The majority of isolates were from patients ≥60 years of age. E. coli resistance was most pronounced for ampicillin (61.56%), followed by trimeth­oprim-sulfamethoxazole (49.80%), amoxicillin-clavulanic acid (34.69%), and cefazolin (30.72%). E. coli resistance to ampicillin, nitrofurantoin, cefepime, ciprofloxacin, fosfomycin, and amoxicillin-clavulanic acid increased significantly with time (all p = 0.001). For E. coli, resistance to ciprofloxacin, one of the most commonly used antibiotics for UTI, increased from 17 to 43% from 2014 to 2018. Conclusion: Most of the uropathogens displayed high resistance to ampicillin, tri­methoprim-sulfamethoxazole, and amoxicillin-clavulanic acid, and were susceptible to meropenem, ertapenem, and imipenem. Fosfomycin and cefepime were useful in the empirical treatment of community-acquired UTIs. A surprisingly high increase was observed in the resistance of E. coli to antimicrobial agents from 2014 to 2018.

Changes of resistance rates in Pseudomonas aeruginosa strains are unrelated to antimicrobial consumption in ICU populations with invasive device-related infection.

To evaluate the relationship between antipseudomonal antibiotic consumption and each individual drug resistance rate in Pseudomonas aeruginosa strains causing ICU acquired invasive device-related infections (IDRI). A post hoc analysis was made of the data collected prospectively from the ENVIN-HELICS registry. Intensive Care Units participating in the ENVIN-UCI registry between the years 2007 and 2016 (3-month registry each year). Patients admitted for over 24h. Annual linear and nonlinear trends of resistance rates of P. aeruginosa strains identified in IDRI and days of treatment of each antipseudomonal antibiotic family per 1000 occupied ICU bed days (DOT) were calculated. A total of 15,095 episodes of IDRI were diagnosed in 11,652 patients (6.2% out of a total of 187,100). Pseudomonas aeruginosa was identified in 2095 (13.6%) of 15,432 pathogens causing IDRI. Resistance increased significantly over the study period for piperacillin-tazobactam (P<0.001), imipenem (P=0.016), meropenem (P=0.004), ceftazidime (P=0.005) and cefepime (P=0.015), while variations in resistance rates for amikacin, ciprofloxacin, levofloxacin and colistin proved nonsignificant. A significant DOT decrease was observed for aminoglycosides (P<0.001), cephalosporins (P<0.001), quinolones (P<0.001) and carbapenems (P<0.001). No significant association was observed between consumption of each antipseudomonal antibiotic family and the respective resistance rates for P. aeruginosa strains identified in IDRI.

Antibiotic Resistance Among Pediatric-Sourced Ocular Pathogens: 8-Year Findings From the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) Surveillance Study.

The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) study is a nationwide longitudinal antibiotic resistance surveillance program specific to bacterial pathogens commonly encountered in ocular infections. We evaluated in vitro resistance rates and trends among isolates obtained from pediatric patients (≤17 years of age). Clinical centers across the United States were invited to submit ocular isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Haemophilus influenzae and Pseudomonas aeruginosa to a central laboratory. Minimum inhibitory concentrations for various antibiotic classes were determined by broth microdilution per Clinical and Laboratory Standards Institute guidelines and interpreted as susceptible, intermediate or resistant based on available breakpoints. Longitudinal trends were analyzed using a Cochran-Armitage test for linear trends in a proportion. Of 4829 isolates collected from January 2009 to December 2016, 995 isolates, sourced primarily from hospitals and referral centers, were obtained from pediatric patients (n = 286 H. influenzae, n = 284 S. aureus, n = 213 CoNS, n = 150 S. pneumoniae and n = 62 P. aeruginosa). With few exceptions, P. aeruginosa and H. influenzae were generally susceptible to the antibiotics tested. Of S. aureus and CoNS isolates, respectively, 56% and 72% were resistant to azithromycin and 24% and 47% were methicillin-resistant (MR); concurrent resistance to other drug classes and multidrug resistance (≥3 drug classes) were prevalent among MR staphylococci. Of S. pneumoniae isolates, 38% and 35% demonstrated resistance to azithromycin and penicillin, respectively. Besifloxacin had the lowest minimum inhibitory concentration against the Gram-positive isolates. These in vitro data suggest antibiotic resistance is common among staphylococcal and pneumococcal isolates collected from pediatric patients with ocular infections. Methicillin resistance was prevalent among staphylococci with many strains demonstrating multidrug resistance. These findings may not be representative of resistance trends in community-based practices.

The Changing Profile of Helicobacter pylori Antibiotic Resistance in Singapore: A 15-Year Study.

Antibiotic resistance is an important cause of H. pylori treatment failure. This study aimed to examine the change in H. pylori antibiotic resistance profile in Singapore over the course of 15 years. The study period was from 2000 to 2014. Gastric mucosal biopsies obtained from H. pylori-positive patients were cultured. Antibiotic susceptibility to metronidazole, clarithromycin, levofloxacin, tetracycline, and amoxicillin was tested. The change in resistance rates over time was analyzed. A total of 708 H. pylori isolates were cultured. There was a significant increase in resistance rates for metronidazole (2000-2002: 24.8%; 2012-2014: 48.2%; p < .001), clarithromycin (2000-2002: 7.9%; 2012-2014: 17.1%; p = .022), and levofloxacin (2000-2002: 5%; 2012-2014: 14.7%; p = .007). The resistance rates for tetracycline (2000-2002: 5%; 2012-2014: 7.6%) and amoxicillin (2000-2002: 3%; 2012-2014: 4.4%) remained stable. Increase in dual (2000-2002: 6.9%; 2012-2014: 9.4%; p = .479) and triple antibiotic resistance rates (2000-2002: 0; 2012-2014: 7.6%; p < .001) were observed. Overall, the most common dual and triple resistance patterns were metronidazole/clarithromycin (4.4%) and metronidazole/clarithromycin/levofloxacin (1.8%), respectively. Over 15 years, H. pylori resistance rates to metronidazole, clarithromycin and levofloxacin had increased. There was increased resistance to multiple antibiotics.

Studies of selective decontamination

On the basis of a systematic review and meta-analysis, Nick Daneman and colleagues, concluded that there was no evidence for increased colonisation or infection with antimicrobial-resistant bacteria in patients receiving selective digestive decontamination (SDD) or selective oropharyngeal decontamination (SOD). The investigators recommend future studies focus on long-term effects of these interventions on antibiotic resistance with a non-crossover cluster-randomised study design. Importantly, the only evidence of better survival with SDD or SOD comes from studies in intensive-care units (ICUs) where—among isolates causing ICU-acquired bacteraemia—less than 1% were resistant to meticillin for Staphylococcus aureus or vancomycin for enterococci, and less than 5% of Escherichia coli and Klebsiella spp were producing extended-spectrum β lactamases.2de Jonge E Schultz MJ Spanjaard L et al.Effects of selective decontamination of digestive tract on mortality and acquisition of resistant bacteria in intensive care: a randomised controlled trial.Lancet. 2003; 362: 1011-1016Summary Full Text Full Text PDF PubMed Scopus (491) Google Scholar, 3de Smet AM Kluytmans JA Cooper BS et al.Decontamination of the digestive tract and oropharynx in ICU patients.N Engl J Med. 2009; 360: 20-31Crossref PubMed Scopus (594) Google Scholar, 4Krueger WA Lenhart FP Neeser G et al.Influence of combined intravenous and topical antibiotic prophylaxis on the incidence of infections, organ dysfunctions, and mortality in critically ill surgical patients: a prospective, stratified, randomized, double-blind, placebo-controlled clinical trial.Am J Respir Crit Care Med. 2002; 166: 1029-1037Crossref PubMed Scopus (229) Google Scholar Whether these findings can be extrapolated to settings with higher levels of antimicrobial resistance is unknown. Unless future studies are (again) done in settings with low levels of antibiotic resistance, clinically significant benefits in unambiguous outcomes for patients, preferably survival, should be the primary focus. Therefore, such studies should include standard-of-care treatment (no SDD or SOD), and investigators should consider chlorhexidine oropharyngeal decontamination as a comparator because this intervention has also been association with prevention of ventilator-associated pneumonia,5Koeman M van der Ven AJ Hak E et al.Oral decontamination with chlorhexidine reduces the incidence of ventilator-associated pneumonia.Am J Respir Crit Care Med. 2006; 173: 1348-1355Crossref PubMed Scopus (308) Google Scholar but has never been compared with SDD or SOD. We fully agree that randomly assigning units instead of patients is the most appropriate design in view of the unit-wide ecological effect pursued. However, the inherent absence of individual randomisation in a cluster randomised study increases the risk of bias caused by systematic differences in baseline characteristics of patients between intervention groups, especially when the intervention is known at time of enrolment, as will be the case when trying to modify the unit-wide ecology. Adjustment for covariates is then needed, which reduces the precision of the effect estimate. Moreover, ICUs might differ in characteristics that are difficult to quantify, but could substantially change study outcomes, such as hand hygiene and antibiotic use. A crossover design would minimise effects of such variables. Therefore, we recommend a cluster-randomised crossover study comparing SDD, SOD, and chlorhexidine to standard care in contemporary settings of antimicrobial resistance. This approach will examine the effectiveness of decontamination strategies on patients' outcomes, before we focus on the long-term consequences of SDD and SOD on antibiotic resistance in such settings. BHJW is supported by funding from the European Community's Seventh Framework Programme ( FP7/2007-2013 ) under grant agreement 282512. MJMB is supported by The Netherlands Organization of Scientific Research ( NWO-VICI 918.76.611 ). Effect of selective decontamination on antimicrobial resistance in intensive care units: a systematic review and meta-analysisWe detected no relation between the use of SDD or SOD and the development of antimicrobial-resistance in pathogens in patients in the ICU, suggesting that the perceived risk of long-term harm related to selective decontamination cannot be justified by available data. However, our study indicates that the effect of decontamination on ICU-level antimicrobial resistance rates is understudied. We recommend that future research includes a non-crossover, cluster randomised controlled trial to assess long-term ICU-level changes in resistance rates. Full-Text PDF Studies of selective decontamination – Authors' replyJames Hurley and Bastiaan Wittekamp and colleagues discuss some of the fascinating and controversial aspects of selective digestive decontamination (SDD) and sound the call for further research to clarify its benefits and risks in intensive care units (ICUs). We agree with Hurley that the greatest limitation of previous research is that it has largely involved patient-level randomisation in single ICUs. We share his concern that this could lead to cross-transmission of antimicrobial-resistant pathogens from intervention to control patients, and mask signals of increased antibiotic resistance. Full-Text PDF

Trends in Aminoglycoside Use and Gentamicin-Resistant Gram-Negative Clinical Isolates in US Academic Medical Centers: Implications for Antimicrobial Stewardship

To measure trends in aminoglycoside antibiotic use and gentamicin-resistant clinical isolates across a network of hospitals and compare network-level relationships with those of individual hospitals. Longitudinal observational investigation. US academic medical centers. Adult inpatients. Adult aminoglycoside use was measured from 2002 or 2003 through 2009 in 29 hospitals. Hospital-wide antibiograms assessed gentamicin resistance by proportions and incidence rates for Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. Mixed-effects analysis of variance was used to assess the significance of changes in aminoglycoside use and changes in resistance rates and proportions. Generalized estimating equations were used to assess the relationship between aminoglycoside use and resistance. Mean aminoglycoside use declined by 41%, reflecting reduced gentamicin (P < .0001) and tobramycin (P < .005) use; amikacin use did not change. The rate and proportion of gentamicin-resistant P. aeruginosa decreased by 48% (P < .0001) and 31% (P < .0001), respectively. The rate and proportion of gentamicin-resistant E. coli increased by 166% and 124%, respectively (P < .0001), and they were related to increasing quinolone resistance in E. coli. Resistance among K. pneumoniae and A. baumannii did not change. Relationships between aminoglycoside use and resistance at the network level were highly variable at the individual hospital level. Mean aminoglycoside use declined in this network of US hospitals and was associated with significant and opposite changes in rates of resistance for some organisms and no change for others. At the individual hospital level, antibiograms appear to be an unreliable reflection of antibiotic use, at least for aminoglycosides.

Antimicrobial Resistance in Isolates from Humans and Food Animals

Antibiotic use is the primary force driving the increase in resistance. To assess changes in resistance rates over time, investigators conducted a retrospective study of Escherichia coli isolates recovered from human and animal specimens submitted between 1950 and 2002 to the E. coli Reference Center and the CDC from public health and veterinary diagnostic laboratories in multiple states. …

Analysis of resistance, cross-resistance and antimicrobial combinations for Pseudomonas aeruginosa isolates from 1997 to 2009

Pseudomonas aeruginosa is a nosocomial and community-acquired pathogen associated with considerable patient morbidity and mortality. Multidrug resistance in P. aeruginosa is a concern owing to the limited therapeutic options available to treat infections due to this organism. In this study, rates of antimicrobial resistance of P. aeruginosa isolates collected by The Surveillance Network Database–USA (Eurofins Medinet, Chantilly, VA) from 1997 to 2009 were examined. The patient population and specimens were stratified according to patient setting and age as well as specimen source. Multidrug resistance was defined as resistance to three or more of the following antimicrobial agents: aztreonam; cefepime; ciprofloxacin; imipenem; gentamicin; and piperacillin/tazobactam (TZP). A total of 924740 P. aeruginosa isolates were examined in this study. Changes in resistance rates to individual antimicrobial agents were <5% for all agents except ciprofloxacin. There was a statistically significant decreasing rate of multidrug-resistant P. aeruginosa to four, five and six antimicrobial agents. For isolates resistant to imipenem, aztreonam and gentamicin, ciprofloxacin had the highest cross-resistance rates. The greatest coverage against P. aeruginosa was by the combination of TZP plus amikacin (94%) followed by aztreonam plus amikacin (90%). Pseudomonas aeruginosa resistance rates remained steady or minimally declined to all antimicrobials from 1997 to 2009. Amongst the β-lactams, TZP has the greatest activity against P. aeruginosa.

Impact of a clonal outbreak of extended-spectrum -lactamase-producing Klebsiella pneumoniae in the development and evolution of bloodstream infections by K. pneumoniae and Escherichia coli: an 11 year experience in Oxfordshire, UK

The objectives of this study were: (i) to describe an outbreak of multidrug-resistant Klebsiella pneumoniae in our population; (ii) to identify the potential source of this outbreak by examining antibiotic resistance trends in urocultures; (iii) to evaluate the contribution of this outbreak to resistance patterns over time in the two commonest Gram-negative blood culture isolates, namely K. pneumoniae and Escherichia coli; and (iv) to assess risk factors for multidrug resistance and the impact of this resistance on mortality and length of stay. We searched Microbiology and Patient Administration Service databases retrospectively and describe resistance trends in E. coli and K. pneumoniae bloodstream infections (BSIs) in Oxfordshire, UK, over an 11 year period. An outbreak of a multidrug-resistant, CTX-M-15 extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae clone was identified and shown by multilocus sequence typing to belong to a novel sequence type designated ST490. This was associated with a sporadic change in resistance rates in K. pneumoniae BSIs with rates of multidrug resistance (defined as resistance to three or more antibiotic classes) reaching 40%. A case-control study showed prior antibiotic exposure as a risk factor for infection with this organism. During the same time period, rates of ESBL-producing Klebsiella spp. isolated from urocultures increased from 0.5% to almost 6%. By contrast, the rate of multidrug resistance in E. coli rose more steadily from 0% in 2000 to 10% in 2010. Changes in resistance rates may be associated with outbreaks of resistant clones in K. pneumoniae. Changing resistance patterns may affect important health economic issues such as length of stay.

Summary trends for the Meropenem Yearly Susceptibility Test Information Collection Program: a 10-year experience in the United States (1999–2008)

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program was a global, longitudinal antimicrobial resistance surveillance network of more than 100 medical centers worldwide monitoring the susceptibility of meropenem and selected other broad-spectrum comparator agents. In 1999, and from 2000 through 2008, a total of 10 or 15 United States (USA) medical centers each forwarded 200 nonduplicate clinical isolates from serious infections to a central processing laboratory. Over the 10-year period of this surveillance program, the activity of meropenem and an average of 11 other antimicrobial agents were assessed against a total of 27 289 bacterial isolates using Clinical and Laboratory Standards Institute reference methods. Meropenem consistently demonstrated low resistance rates against Enterobacteriaceae species isolates through 2008 and did not exhibit a widespread change in resistance rates over the monitored interval. In fact, the incidence of emerging carbapenemase-producing (KPC-type) Klebsiella spp. showed a decline in 2008 compared to the steeply increasing rates observed from 2004 to 2007. Moreover, the KPC serine carbapenemases have spread to other Enterobacteriaceae species monitored by the MYSTIC Program. Greatest increases in antimicrobial resistance rates were observed for the fluoroquinolones (ciprofloxacin, levofloxacin) among all species monitored by the MYSTIC Program. Current susceptibility rates for meropenem when tested against prevalent pathogens were Pseudomonas aeruginosa (439 strains, 85.4% susceptible), Enterobacteriaceae (1537 strains, 97.3% susceptible), methicillin-susceptible staphylococci (460 strains, 100.0% susceptible), Streptococcus pneumoniae (125 strains, 80.2% at meningitis susceptibility breakpoints), other streptococci (159 strains, 90.0–100.0% susceptible), and Acinetobacter spp. (127 strains, 45.7% susceptible), the widest spectrum among β-lactams tested in 2008 and throughout the last decade. Continued local surveillance of broad-spectrum agents following the completion of the MYSTIC Program (USA) appears critical to detect emerging resistances among pathogens causing the most serious infections requiring carbapenem agents.

Macrolide susceptibility in Streptococcus pyogenes: monitoring of isolates collected from throat swabs for the period november 2003 to september 2006

Background: Streptococcus pyogenes can cause acute suppurative infections (tonsillitis and pharyngitis) and serious complications like rheumatic fever or acute post-streptococcal glomerulonephritis. Antibiotic treatment of streptococcal infections is recommended and penicillin is the therapy of choice, moreover, macrolides represent an important alternative particularly for patients with ß-lactam-associated allergies. However, increasing resistance of S. pyogenes to macrolides has been observed in some European countries (especially in Spain and Italy) in the last decade.This study was conducted to update our knowledge on this evolution. Materials and methods: A total of 128 clinical strains of S. pyogenes isolated from 933 throat swabs collected in the Clinical Microbiological Laboratory of Ovada (ASL 22) between November 2003 and September 2006 were tested for their susceptibility to erythromycin, clindamycin and rokitamycin. The phenotype of macrolide resistance was determined by the triple-disc diffusion test method (Giovanetti et al, 1999). Results: S. pyogenes strains isolated between November 2003 and December 2005 showed a percentage of macrolide-resistance of 15%; more precisely 9% with phenotype M and 6% with phenotype iMLS. Only 3 of the 28 isolates (10.7%) collected between January-September 2006 were macrolide-resistant (phenotype M).All 128 isolates were fully susceptible to rokitamycin. Conclusion: Macrolide resistance rates determined in the present study were relatively low in comparison to the values registered in our country in the last decade. Efflux of the drug (phenotype M) is the predominating mechanism. This type of resistance does not affect the activity of macrolides 16-membered (e.g. rokitamicin).However, changes of resistance rates and their prevailing mechanisms can occur rapidly. For safe empirical prescription of macrolides, further surveillance studies that include the identification of resistance mechanisms are required to follow current trends.

Changes in Resistance Rates of Common Gram-negative Bacilli in Panyu Area :Characteristics and Analysis

目的 分析本地区2003年1月～2006年6月期间最常见革兰氏阴性茵(大肠埃希茵、肺炎克雷伯菌、铜绿假单胞菌和鲍曼不动杆菌)耐药性的变化,为指导临床合理使用抗菌素提供可靠依据.方法 应用回顾性调查分析方法对我院该期间临床标本分离的大肠埃希菌、肺炎克雷伯菌、铜绿假单胞菌和鲍曼不动杆菌的药敏试验进行对比统计分析.结果 近4年来,该4种细菌对常用抗菌药物的耐药率总体呈上升趋势.大肠埃希茵对头孢呋辛、头孢他啶、头孢噻肟、头孢吡肟耐药率变化显著,对大肠埃希茵保持较强抗茵活性而耐药率＜30%的抗菌药物有阿莫西林-克拉维酸、哌拉西林-三唑巴坦、亚胺培南、美诺培南、阿米卡星;肺炎克雷伯茵对哌拉西林、替卡西林-克拉维酸、头孢他啶、头孢噻肟、头孢呋辛、环丙沙星耐药率变化显著,对肺炎克雷伯菌保持较强抗菌活性而耐药率＜30%的抗菌药物有阿莫西林-克拉维酸、哌拉西林-三唑巴坦、亚胺培南、美诺培南、阿米卡星、奈替米星、妥布霉素;铜绿假单胞菌对妥布霉素、阿米卡星、庆大霉素、环丙沙星耐药率变化显著,对铜绿假单胞菌保持较强抗菌活性而耐药率＜30%的抗菌药物有替卡西林-克拉维酸、哌拉西林-三唑巴坦、头孢他啶、亚胺培南、美诺培南、阿米卡星、庆大霉素、妥布霉素、环丙沙星、多粘菌素E;对鲍曼不动杆菌保持较强抗茵活性而耐药率＜30%的抗茵药物有哌拉西林-三唑巴坦、头孢他啶、亚胺培南、美诺培南、阿米卡星.结论 本地区大肠埃希菌、肺炎克雷伯茵、铜绿假单胞菌和鲍曼不动杆菌对常用抗菌药物耐药率高,多重耐药现象严重,根据药敏结果选择抗菌药物,可有效控制和减缓细茵耐药性的增长。