The relationship between antecedent antibiotic use and resistance to extended-spectrum cephalosporins in group I beta-lactamase-producing organisms

Antibiotic Treatment of Infections Caused by AmpC-Producing Enterobacterales

AmpC enzymes are a class of beta-lactamases produced by Gram-negative bacteria, including several Enterobacterales. When produced in sufficient amounts, AmpCs can hydrolyze third-generation cephalosporins (3GCs) and piperacillin/tazobactam, causing resistance. In Enterobacterales, the AmpC gene can be chromosomal- or plasmid-encoded. Some species, particularly Enterobacter cloacae complex, Klebsiella aerogenes, and Citrobacter freundii, harbor an inducible chromosomal AmpC gene. The expression of this gene can be derepressed during treatment with a beta-lactam, leading to AmpC overproduction and the consequent emergence of resistance to 3GCs and piperacillin/tazobactam during treatment. Because of this phenomenon, the use of carbapenems or cefepime is considered a safer option when treating these pathogens. However, many areas of uncertainty persist, including the risk of derepression related to each beta-lactam; the role of piperacillin/tazobactam compared to cefepime; the best option for severe or difficult-to-treat cases, such as high-inoculum infections (e.g., ventilator-associated pneumonia and undrainable abscesses); the role of de-escalation once clinical stability is obtained; and the best treatment for species with a lower risk of derepression during treatment (e.g., Serratia marcescens and Morganella morganii). The aim of this review is to collate the most relevant information about the microbiological properties of and therapeutic approach to AmpC-producing Enterobacterales in order to inform daily clinical practice.

Clinical practice guideline for the prevention and management of peritoneal dialysis associated infections in children: 2024 update

Infection-related complications remain the most significant cause for morbidity and technique failure in infants, children and adolescents who receive maintenance peritoneal dialysis (PD). The 2024 update of the Clinical Practice Guideline for the Prevention and Management of Peritoneal Dialysis Associated Infection in Children builds upon previous such guidelines published in 2000 and 2012 and provides comprehensive treatment guidance as recommended by an international group of pediatric PD experts based upon a review of published literature and pediatric PD registry data. The workgroup prioritized updating key clinical issues contained in the 2012 guidelines, in addition to addressing additional questions developed using the PICO format. A variety of new guideline statements, highlighted by those pertaining to antibiotic therapy of peritonitis as a result of the evolution of antibiotic susceptibilities, antibiotic stewardship and clinical registry data, as well as new clinical benchmarks, are included. Recommendations for future research designed to fill important knowledge gaps are also provided.

Ceftolozane/Tazobactam for the Treatment of Complicated Infections in Hospital Settings-A French Real-world Study

Background

This study describes the conditions of use of ceftolozane/tazobactam (C/T) and associated outcomes in French hospital settings.

Methods

This was a prospective, multicenter, French observational study. Patients who received at least 1 dose of C/T were included and followed up as per routine clinical practice, until stop of C/T.

Results

A total of 260 patients were enrolled between October 2018 and December 2019 in 30 centers across France. Of these, 177 (68.0%) received C/T as per indication of usage following the results of the antibiogram (documented cases). Among documented patients, the mean age was 61.8 years, 73.4% were males, and 93.8% presented with multidrug-resistant (MDR) bacteria at inclusion. C/T was most frequently prescribed for pneumonia (48.6%), bacteremia (14.7%), complicated intra-abdominal infections (13.0%), or complicated urinary tract infections (9.6%). Pseudomonas aeruginosa was the species most frequently isolated with 212 strains from 155 patients, and 96.2% of these strains were susceptible to C/T. The median duration of C/T treatment was 16.1 days (1-115, n = 176). Complete or partial cure was achieved in 71.7% of patients, C/T was discontinued upon adaptation to microbiology results in 11.3% of patients for the following reasons: treatment failure in 2.8%, death in 4.0%, adverse events in 1.7%, and other in 8.5%.

Conclusions

This is the first prospective observational study of C/T utilization in a health care setting enrolling many patients in France. C/T demonstrated a high rate of clinical effectiveness in MDR infections, confirming it as an effective treatment option for complicated infections in a high-risk population.

Divergent genetic landscapes drive lower levels of AmpC induction and stable de-repression in Serratia marcescens compared to Enterobacter cloacae

The chromosomally encoded AmpC beta-lactamase is widely distributed throughout the Enterobacterales. When expressed at high levels through transient induction or stable de-repression, resistance to ceftriaxone, a commonly used antibiotic, can develop. Recent clinical guidance suggests, based on limited evidence, that resistance may be less likely to develop in Serratia marcescens compared to the better-studied Enterobacter cloacae and recommends that ceftriaxone may be used if the clinical isolate tests susceptible. We sought to generate additional data relevant to this recommendation. AmpC de-repression occurs predominantly because of mutation in the ampD peptidoglycan amidohydrolase. We find that, in contrast to E. cloacae, where deletion of ampD results in high-level ceftriaxone resistance (with ceftriaxone MIC = 96 µg/mL), in S. marcescens deletion of two amidohydrolases (ampD and amiD2) is necessary for AmpC de-repression, and the resulting ceftriaxone MIC is 1 µg/mL. Two mechanisms for this difference were identified. We find both a higher relative increase in ampC transcript level in E. cloacae ΔampD compared to S. marcescens ΔampDΔamiD2, as well as higher in vivo efficiency of ceftriaxone hydrolysis by the E. cloacae AmpC enzyme compared to the S. marcescens AmpC enzyme. We also observed higher relative levels of transient AmpC induction in E. cloacae vs S. marcescens when exposed to ceftriaxone. In time-kill curves, this difference translates into the survival of E. cloacae but not S. marcescens at clinically relevant ceftriaxone concentrations. In summary, our findings can explain the decreased propensity for on-treatment ceftriaxone resistance development in S. marcescens, thereby supporting recently issued clinical guidance.

Clinical Outcomes of Third-Generation Cephalosporin Definitive Therapy for Bloodstream Infections Due to Enterobacterales with Potential AmpC Induction: A Single-Center Retrospective Study

The recommended therapy for severe infections caused by AmpC-inducible Enterobacterales (AmpC-E) typically involves cefepime or carbapenems. In an era of emerging resistance to these antimicrobials, we aim to assess the impact of third-generation cephalosporins (3GCs) vs. alternative antibiotics on clinical outcomes in bloodstream infections (BSIs) due to AmpC-E. We retrospectively included hospitalized adult patients with BSIs caused by 3GC-susceptible AmpC-E between 2012 and 2022, comparing the outcomes of 3GC and non-3GC definitive therapies. The primary outcome was overall treatment failure (OTF), encompassing 90-day all-cause mortality, 90-day reinfection, and 90-day readmission. Secondary outcomes comprised components of the OTF, in-hospital all-cause mortality, and length-of-stay. Within a total cohort of 353 patients, OTF occurred in 46.5% and 41.5% in the 3GC- and non-3GC-therapy groups, respectively (p = 0.36). The 3GC-therapy group exhibited a longer length-of-stay (38 vs. 21 days, p = 0.0003) and higher in-hospital mortality (23.3% vs. 13.4%, p = 0.019). However, the 90-day mortality, 90-day reinfection, and 90-day readmission were comparable between the therapy groups. Subgroup analyses involving high-risk AmpC-E and 3GC vs. standard-of-care yielded similar conclusions. Overall, our findings suggest that 3GC definitive therapy may not result in poorer clinical outcomes for the treatment of BSIs caused by AmpC-E.

β-Lactam Resistance in ESKAPE Pathogens Mediated Through Modifications in Penicillin-Binding Proteins: An Overview

Bacteria acquire β-lactam resistance through a multitude of mechanisms among which production of β-lactamases (enzymes that hydrolyze β-lactams) is the most common, especially in Gram-negatives. Structural changes in the high-molecular-weight, essential penicillin-binding proteins (PBPs) are widespread in Gram-positives and increasingly reported in Gram-negatives. PBP-mediated resistance is largely achieved by accumulation of mutation(s) resulting in reduced binding affinities of β-lactams. Herein, we discuss PBP-mediated resistance among ESKAPE pathogens that cause diverse hospital- and community-acquired infections globally.

Emergence of plasmid-mediated colistin resistance mcr-3.5 gene in Citrobacter amalonaticus and Citrobacter sedlakii isolated from healthy individual in Thailand

Citrobacter spp. are Gram-negative bacteria commonly found in environments and intestinal tracts of humans and animals. They are generally susceptible to third-generation cephalosporins, carbapenems and colistin. However, several antibiotic resistant genes have been increasingly reported in Citrobacter spp., which leads to the postulation that Citrobacter spp. could potentially be a reservoir for spreading of antimicrobial resistant genes. In this study, we characterized two colistin-resistant Citrobacter spp. isolated from the feces of a healthy individual in Thailand. Based on MALDI-TOF and ribosomal multilocus sequence typing, both strains were identified as Citrobacter sedlakii and Citrobacter amalonaticus. Genomic analysis and S1-nuclease pulsed field gel electrophoresis/DNA hybridization revealed that Citrobacter sedlakii and Citrobacter amalonaticus harbored mcr-3.5 gene on pSY_CS01 and pSY_CA01 plasmids, respectively. Both plasmids belonged to IncFII(pCoo) replicon type, contained the same genetic context (Tn3-IS1-ΔTnAs2-mcr-3.5-dgkA-IS91) and exhibited high transferring frequencies ranging from 1.03×10-4 - 4.6×10-4 CFU/recipient cell Escherichia coli J53. Colistin-MICs of transconjugants increased ≥ 16-fold suggesting that mcr-3.5 on these plasmids can be expressed in other species. However, beside mcr, other major antimicrobial resistant determinants in multidrug resistant Enterobacterales were not found in these two isolates. These findings indicate that mcr gene continued to evolve in the absence of antibiotics selective pressure. Our results also support the hypothesis that Citrobacter could be a reservoir for spreading of antimicrobial resistant genes. To the best of our knowledge, this is the first report that discovered human-derived Citrobacter spp. that harbored mcr but no other major antimicrobial resistant determinants. Also, this is the first report that described the presence of mcr gene in C. sedlakii and mcr-3 in C. amalonaticus.

Clinical outcome of wild-type AmpC-producing Enterobacterales infection in critically ill patients treated with β-lactams: a prospective multicenter study

Background

β-lactams are the main antibiotics used against wild-type AmpC-producing Enterobacterales (wtAE). However, they may fail or select AmpC-overproducing mutants. Our aim was to assess factors associated with clinical failure of β-lactams in the treatment of wtAE infection.

Methods

From September 2017 to December 2020, we prospectively included all consecutive patients treated by definitive β-lactams therapy for wtAE infection in four university ICUs. Clinical failure was defined as inadequate response to antimicrobial therapy leading to death or to the switch for a broader-spectrum antibiotic.

Results

177 patients were included and 29.4% progressed to clinical failure. E. cloacae was the most prevalent species (42.4%) and ventilator-associated pneumonia (VAP) was the most frequent wtAE infection (69.5%). Cefepime and cefotaxime were used as definitive antibiotic treatment in 42.9% and 27.7% of patients, respectively. Occurrence of AmpC-overproduction was documented in 5.6% of patients and was associated with clinical failure (p = 0.004). In multivariate analysis, VAP (p < 0.001, OR 11.58 [95% CI 3.11–43.02] and K. aerogenes (p = 0.030, OR 3.76 [95% CI 1.13–12.46]) were independently associated with clinical failure. Conversely, cefotaxime as definitive treatment was found inversely associated with the risk of clinical failure (p = 0.022, OR 0.25 [95% CI 0.08–0.82]). After inverse probability weighting, cefotaxime showed a 20% risk reduction of clinical failure (95% CI  5–35%, p = 0.007) whatever the location of infection, the SOFA score on the day of wtAE infection, or the bacterial species.

Conclusions

Clinical failure in the treatment of wtAE infections is associated with the infection site and the causal microorganism. Additionally, cefotaxime use is probably protective against clinical failure in wtAE infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01079-5.

Bacterial susceptibility change post national shortage of first cephalosporin in Japan; a longitudinal retrospective database study using interrupted time series analysis

OBJECTIVES

The clinical evidence for the impact of narrow-spectrum antimicrobial shortages on bacterial susceptibility is limited. Our purposes were to determine the impacts of the disruption of most of the Cefazolin (CEZ) supply in Japan on the susceptibility of pathogens and to analyze how long these changes persisted after the shortage of CEZ.

METHODS

We performed an interrupted time series analysis using the Japanese Infectious Disease Nationwide database. We analyzed each pathogen before and after CEZ shortage in 52 university hospitals from 2018 to 2020. May to November 2019 was designated as the implementation term for CEZ shortage. The primary outcome was the susceptibility to CEZ and other antimicrobial agents. Among all pathogens isolated from facilities, we identified pathogens that were tested for susceptibility to CEZ.

RESULTS

Of the 26 pathogens identified, analysis was performed on a total of 36346 isolates of five pathogens (E.coli, K.pneumoniae, K.oxytoca, P.mirabillis, S.aureus). Among four gram negative pathogens with low susceptibility, there were no significant immediate changes after the CEZ shortage, however, the slope change significantly increased by 1.29-2.69% per month and continued to improve 1 year after the shortage. Regarding S. aureus, which was highly susceptible at the baseline, neither immediate change nor slope was significant.

CONCLUSIONS

This quasi-experimental analysis using nationwide large database revealed that restriction of use due to narrow antimicrobial shortages may lead to improved susceptibility over the subsequent year. The results suggest that temporary switching of antimicrobial agents on a national scale could be effective.

Infectious Diseases Society of America Guidance on the Treatment of AmpC β-lactamase-Producing Enterobacterales, Carbapenem-Resistant Acinetobacter baumannii, and Stenotrophomonas maltophilia Infections

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. A previous guidance document focused on infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa). Here, guidance is provided for treating AmpC β-lactamase-producing Enterobacterales (AmpC-E), carbapenem-resistant Acinetobacter baumannii (CRAB), and Stenotrophomonas maltophilia infections.

METHODS

A panel of six infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated questions about the treatment of AmpC-E, CRAB, and S. maltophilia infections. Answers are presented as suggestions and corresponding rationales. In contrast to guidance in the previous document, published data on optimal treatment of AmpC-E, CRAB, and S. maltophilia infections are limited. As such, guidance in this document is provided as "suggested approaches" based on clinical experience, expert opinion, and a review of the available literature. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment suggestions are provided, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Suggestions apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of September 17, 2021 and will be updated annually. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance-2.0/.

Comparison of outcomes in urinary tract infections caused by AmpC-harboring organisms treated with AmpC stable versus AmpC susceptible agents

There is minimal data on the optimal treatment of lower inoculum infections such as urinary tract infections (UTIs) caused by SPICE organisms which encode the betalactamase enzyme, AmpC. This single-center, retrospective review of adult hospitalized patients with UTIs caused by a SPICE organism compared outcomes amongst patients treated with drugs susceptible to AmpC hydrolysis versus drugs stable against AmpC. Of 156 patients, similar rates of clinical response, 30-day infection related readmission, 30-day infection recurrence, 30-day mortality rates, and median length of hospital stay were found between the two groups. Notably, 44% of patients with ceftriaxone resistance reported had recent β-lactam exposure versus only 11% of patients without ceftriaxone resistance (P = 0.002). Based on our data, there does not appear to be a difference in clinical response or any of the secondary outcomes in patients with UTIs treated with AmpC stable and AmpC susceptible agents.

Antimicrobial Use in COVID-19 Patients in the First Phase of the SARS-CoV-2 Pandemic: A Scoping Review

This scoping review provides new evidence on the prevalence and patterns of global antimicrobial use in the treatment of COVID-19 patients; identifies the most commonly used antibiotics and clinical scenarios associated with antibiotic prescribing in the first phase of the pandemic; and explores the impact of documented antibiotic prescribing on treatment outcomes in COVID-19 patients. The review complies with PRISMA guidelines for Scoping Reviews and the protocol is registered with the Open Science Framework. In the first six months of the pandemic, there was a similar mean antibiotic prescribing rate between patients with severe or critical illness (75.4%) and patients with mild or moderate illness (75.1%). The proportion of patients prescribed antibiotics without clinical justification was 51.5% vs. 41.9% for patients with mild or moderate illness and those with severe or critical illness. Comparison of patients who were provided antibiotics with a clinical justification with those who were given antibiotics without clinical justification showed lower mortality rates (9.5% vs. 13.1%), higher discharge rates (80.9% vs. 69.3%), and shorter length of hospital stay (9.3 days vs. 12.2 days). In the first 6 months of the pandemic, antibiotics were prescribed for COVID-19 patients regardless of severity of illness. A large proportion of antibiotic prescribing for mild and moderate COVID-19 patients did not have clinical evidence of a bacterial co-infection. Antibiotics may not be beneficial to COVID-19 patients without clinical evidence of a bacterial co-infection.

Real-world evaluation of ceftolozane/tazobactam therapy and clinical outcomes in France

OBJECTIVES

To describe the real-world clinical use of ceftolozane/tazobactam (C/T) and associated outcomes in France.

PATIENTS AND METHODS

Multicenter, prospective cohort study conducted in 22 hospitals. All adult patients who received at least one dose of C/T were asked to participate (2018-2019). Patients were treated according to standard hospital practice and followed up until C/T stop.

RESULTS

At the time of the analysis, 84 patients were evaluated. The median age was 64.8 years, and 67.9% (57/84) of patients were males. Fifty-seven patients (57/82, 69.5%) had one or more risk factors for multidrug-resistant (MDR) infections (missing MDR risk factor data for two patients). Most patients were critically ill and had several comorbidities. A majority (59/84, 70.2%) of patients had nosocomial infections. Half of all patients (n=42) had a diagnosis of pneumonia, of which 69% (29/42) were hospital acquired. Overall, 90.5% (76/84) of patients had MDR bacteria. Pseudomonas aeruginosa was the most frequently isolated bacterium (71/80, 88.8%), including 93% (80/86) of C/T-susceptible strains. C/T was prescribed as the first-line treatment to 29.8% (25/84) of patients. A concomitant antibiotic treatment was prescribed to 48.8% (41/84) of patients, of whom 65.9% (27/41) were prescribed concomitant antibiotics at the same time as C/T initiation. Empirical C/T prescription was microbiologically appropriate in 11/16 patients after susceptibility testing. Most patients (44/72, 61.1%) were cured and four (4/72, 5.6%) deaths were reported.

CONCLUSIONS

The results showed that C/T was most frequently prescribed for documented cases of P. aeruginosa infections. Most outcomes were positive, including among pneumonia patients.

A Primer on AmpC β-Lactamases: Necessary Knowledge for an Increasingly Multidrug-resistant World

Understanding the nuances of AmpC β-lactamase-mediated resistance can be challenging, even for the infectious diseases specialist. AmpC resistance can be classified into 3 categories: (1) inducible chromosomal resistance that emerges in the setting of a β-lactam compound, (2) stable derepression due to mutations in ampC regulatory genes, or (3) the presence of plasmid-mediated ampC genes. This review will mainly focus on inducible AmpC resistance in Enterobacteriaceae. Although several observational studies have explored optimal treatment for AmpC producers, few provide reliable insights into effective management approaches. Heterogeneity within the data and inherent selection bias make inferences on effective β-lactam choices problematic. Most experts agree it is prudent to avoid expanded-spectrum (ie, third-generation) cephalosporins for the treatment of organisms posing the greatest risk of ampC induction, which has best been described in the context of Enterobacter cloacae infections. The role of other broad-spectrum β-lactams and the likelihood of ampC induction by other Enterobacteriaceae are less clear. We will review the mechanisms of resistance and triggers resulting in AmpC expression, the species-specific epidemiology of AmpC production, approaches to the detection of AmpC production, and treatment options for AmpC-producing infections.

Treatment of Bacteremia Caused by Enterobacter spp.: Should the Potential for AmpC Induction Dictate Therapy? A Retrospective Study

Objective: Carbapenems are considered treatment of choice for bacteremia caused by potential AmpC-producing bacteria, including Enterobacter spp. We aimed to compare mortality following carbapenem vs. alternative antibiotics for the treatment of Enterobacter spp. bacteremia. Patients and Methods: We conducted a retrospective study in two centers in Israel. We included hospitalized patients with Enterobacter bacteremia treated with third-generation cephalosporins (3GC), piperacillin/tazobactam, quinolones, or carbapenem monotherapy as the main antibiotic in the first week of treatment, between 2010 and 2017. Cefepime was excluded due to nonavailability during study years. The primary outcome was 30-day all-cause mortality. Univariate and multivariate analyses were conducted, introducing the main antibiotic as an independent variable. Results: Two hundred seventy-seven consecutive patients were included in the analyses. Of these, 73 were treated with 3GC, 39 with piperacillin/tazobactam, 104 with quinolones, and 61 with carbapenems. All-cause 30-day mortality was 16% (45 patients). The type of antibiotics was not significantly associated with mortality on univariate or multivariate analyses. With carbapenems as reference, adjusted odds ratios (ORs) for mortality were 0.708, 95% confidence interval (CI) 0.231-2.176 with 3GC; OR 1.172, 95% CI 0.388-3.537 with piperacillin/tazobactam; and OR 0.586, 95% CI 0.229-1.4 with quinolones. The main antibiotic was not associated with repeated growth of Entrobacter spp. in blood cultures or other clinical specimens. Resistance development was observed with 3GC and piperacillin/tazobactam. Conclusions: Carbapenem treatment was not advantageous to alternative antibiotics, including 3GC, among patients with Enterobacter spp. bacteremia in an observational study.

Enterobacter spp.: Update on Taxonomy, Clinical Aspects, and Emerging Antimicrobial Resistance

The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. First described in 1960, this group member has proven to be more complex as a result of the exponential evolution of phenotypic and genotypic methods. Today, 22 species belong to the Enterobacter genus. These species are described in the environment and have been reported as opportunistic pathogens in plants, animals, and humans. The pathogenicity/virulence of this bacterium remains rather unclear due to the limited amount of work performed to date in this field. In contrast, its resistance against antibacterial agents has been extensively studied. In the face of antibiotic treatment, it is able to manage different mechanisms of resistance via various local and global regulator genes and the modulation of the expression of different proteins, including enzymes (β-lactamases, etc.) or membrane transporters, such as porins and efflux pumps. During various hospital outbreaks, the Enterobacter aerogenes and E. cloacae complex exhibited a multidrug-resistant phenotype, which has stimulated questions about the role of cascade regulation in the emergence of these well-adapted clones.

Ceftriaxone use in a tertiary care hospital in Kilimanjaro, Tanzania: A need for a hospital antibiotic stewardship programme

Excessive use of antibiotics, especially watch group antibiotics such as ceftriaxone leads to emergence and spread of antimicrobial resistance (AMR). In low and middle-income countries (LMICs), antibiotics are overused but data on consumption is scarcely available. We aimed at determining the extent and predictors of ceftriaxone use in a tertiary care university teaching hospital in Kilimanjaro, Tanzania. A hospital-based cross-sectional study was conducted from August 2013 through August 2015. Patients admitted in the medical, surgical wards and their respective intensive care units, receiving antimicrobials and other medications for various ailments were enrolled. Socio-demographic and clinical data were recorded in a structured questionnaire from patients' files and logistic regression was performed to determine the predictors for ceftriaxone use. Out of the 630 patients included in this study, 322 (51.1%) patients were on ceftriaxone during their time of hospitalization. Twenty-two patients out of 320 (6.9%) had been on ceftriaxone treatment without evidence of infection. Ceftriaxone use for surgical prophylaxis was 44 (40.7%), of which 32 (72.7%) and 9 (20.5%) received ceftriaxone prophylaxis before and after surgery, respectively. Three (6.8%) received ceftriaxone prophylaxis during surgery. Predicting factors for that the health facility administered ceftriaxone were identified as history of any medication use before referral to hospital [OR = 3.4, 95% CI (1.0-11.4), p = 0.047], bacterial infection [OR = 18.0, 95% CI (1.4-225.7, p = 0.025)], surgical ward [OR = 2.9, 95% CI (0.9-9.4), p = 0.078] and medical wards [OR = 5.0, 95% CI (0.9-28.3), p = 0.070]. Overall, a high ceftriaxone use at KCMC hospital was observed. Antimicrobial stewardship programs are highly needed to monitor and regulate hospital antimicrobial consumption, which in turn could help in halting the rising crisis of antimicrobial resistance.

New insights into Citrobacter freundii sepsis in neonates

BACKGROUND

The aim of this study was to investigate the clinical features of neonatal sepsis caused by Citrobacter freundii as well as the current status and treatment strategy for multi-drug resistance of infection with this bacterium.

METHODS

Nine newborns were diagnosed with C. freundii sepsis between January 2014 and December 2017. We collated and analyzed a range of data for these nine patients, including general information, laboratory tests during infection, blood culture and treatment.

RESULTS

One of the patients died after only 7 h of infection. In the remaining eight cases, three patients developed meningitis, although none had brain abscess. A reduction of white blood cells (WBC) was detected <24 h after the start of infection, compared with at 48-72 h, when WBC count had increased and platelets progressively decreased. In all nine cases the infection was susceptible to tigecycline and was resistant to cephalosporins, carbapenems, and quinolones. In eight cases the infection was susceptible to co-trimoxazole and in the other case it was susceptible to amikacin. Of the eight patients who were cured, three received meropenem, two received ceftriaxone, one received amikacin, and two received tigecycline.

CONCLUSION

Reduction in WBC could take place in the early stages of C. freundii infection in newborns. The incidence of brain abscess was not high, but multi-drug resistance was common. Some non-sensitive drugs can also treat C. freundii sepsis effectively.

Comparison in outcome with tailored antibiotic prophylaxis postoperatively in pediatric intestinal transplant population

BIs are ubiquitous among the pediatric intestinal transplant patient population. Personalizing postoperative prophylaxis antibiotic regimens may improve outcomes in this population. A retrospective analysis of all pediatric patients who underwent intestinal transplantation was evaluated to compare standardized and tailored regimens of antibiotics provided as prophylaxis postoperatively. Patients in the standard group have both shorter time to and higher rate of BIs, which was statistically significant (P < 0.001). Of the children who developed a BI, there was no statistical difference in average times to the development of a second BI (293 vs 119 days, P = 0.211). The tailored group had prolonged times until the development of a MDRO (52.6 vs 63.9 days, P = 0.677). Although not statistically significant, the tailored group had a propensity to present with gram-negative pathogens after transplant as compared to the standard regimen group, which presented with gram-positive pathogens (P = 0.103). Children with a history of an MDRO held a 7.3 (P < 0.01) times more likelihood of death within a year of transplant. A tailored prophylactic antibiotic regimen in the post-transplant period appears to prolong the time to the first BI. Although the data do not show differences in mortality, further study may prove the impact of a tailored antibiotic regimen on morbidity and mortality rates.

Diagnostic Evasion of Highly-Resistant Microorganisms: A Critical Factor in Nosocomial Outbreaks

Highly resistant microorganisms (HRMOs) may evade screening strategies used in routine diagnostics. Bacteria that have evolved to evade diagnostic tests may have a selective advantage in the nosocomial environment. Evasion of resistance detection can result from the following mechanisms: low-level expression of resistance genes not resulting in detectable resistance, slow growing variants, mimicry of wild-type-resistance, and resistance mechanisms that are only detected if induced by antibiotic pressure. We reviewed reports on hospital outbreaks in the Netherlands over the past 5 years. Remarkably, many outbreaks including major nation-wide outbreaks were caused by microorganisms able to evade resistance detection by diagnostic screening tests. We describe various examples of diagnostic evasion by several HRMOs and discuss this in a broad and international perspective. The epidemiology of hospital-associated bacteria may strongly be affected by diagnostic screening strategies. This may result in an increasing reservoir of resistance genes in hospital populations that is unnoticed. The resistance elements may horizontally transfer to hosts with systems for high-level expression, resulting in a clinically significant resistance problem. We advise to communicate the identification of HRMOs that evade diagnostics within national and regional networks. Such signaling networks may prevent inter-hospital outbreaks, and allow collaborative development of adapted diagnostic tests.

Citrobacter freundii bacteremia: Risk factors of mortality and prevalence of resistance genes

BACKGROUND/PURPOSE

Multidrug-resistant strains of Citrobacter have emerged, which carry Amp-C β-lactamase (Amp-C), broad-spectrum β-lactamase, extended-spectrum β-lactamase (ESBL), and other resistance mechanisms. These strains are associated with a higher rate of in-hospital mortality. The object of this study is to determine the mortality risk factors, susceptibility pattern to antibiotics, and prevalence of resistance genes in patients with Citrobacter freundii bacteremia.

METHODS

From January 2009 to December 2014, blood isolates of C. freundii were collected in MacKay Memorial Hospital, Taipei, Taiwan. PCR technique and sequencing were performed for resistance genes. Pulsed-field gel electrophoresis (PFGE) was done using XbaI restriction enzyme. The clinical characteristics and risk factors for mortality are demonstrated.

RESULTS

The 36 blood isolates of C. freundii belonged to 32 different PFGE pulsotypes, and 15 isolates (41.7%) were polymicrobial. The most common source of infection was intra-abdominal origin (61.1%), followed by unknown sources (22.2%), the urinary tract (8.3%), intravascular catheter (5.6%), and soft tissue (2.8%). High degree of antibiotic resistance was noted for cefazolin (100%), cefoxitin (97.2%), and cefuroxime (66.7%). The bla_TEM-1 resistance gene was present in 16.7% isolates. 72.2% isolates carried bla_AmpC and 5.6% isolates carried ESBL genes (bla_SHV-12 or bla_CTX-M-15). Multivariate analysis indicated that the independent risk factor for 28-day mortality was carrying the bla_TEM-1 resistance gene.

CONCLUSION

For patients with C. freundii bacteremia, carrying the bla_TEM-1 resistance gene was an independent risk factor for 28-day mortality. Carbapenems, fourth-generation cephalosporins, amikacin, and quinolones are still reliable agents for drug-resistant strains.

Prevalence of AmpC- and Extended-Spectrum β-Lactamase-Harbouring Enterobacteriaceae in Faecal Flora of a Healthy Domestic Canine Population

In order to estimate the prevalence of AmpC- and ESBL β-lactamase-producing Enterobacteriaceae in the faecal flora of a healthy domestic canine population, faecal samples were obtained from healthy dogs receiving routine parasitology screening at the Ohio State University Veterinary Medical Center, between January 2013 and April 2013. Samples were screened for the presence of AmpC and ESBL β-lactamase phenotypes, and the clinically important genotypes, bla_CMY and bla_CTX-M , were confirmed via conventional PCR. Minimum inhibitory concentrations were determined for isolates and plasmids were characterized. Two hundred and twelve canine faecal samples were screened, of which 30 harboured isolates carrying the AmpC bla_CMY , representing 14.2% of the population (95% CI: 9.4-18.9%). Nine samples harboured isolates that carried the ESBL bla_CTX-M , representing 4.2% of the population (95% CI: 1.5-7.0%). Isolates containing bla_CMY harboured multiple plasmid replicon types, while isolates containing bla_CTX-M harboured few plasmid replicon types. Our results suggest that domestic dogs may serve as a reservoir for extended-spectrum cephalosporin resistance genes for other domestic animal populations as well as for their human companions. This represents a potential veterinary and public health risk that warrants further investigation and continued surveillance to ascertain the nature and extent of the risk. The high level of diversity of plasmid content among isolates harbouring bla_CMY suggests broader dissemination relative to bla_CTX-M isolates.

Using a simple point-prevalence survey to define appropriate antibiotic prescribing in hospitalised children across the UK

BACKGROUND

The National Health Service England, Commissioning for Quality and Innovation for Antimicrobial Resistance (CQUIN AMR) aims to reduce the total antibiotic consumption and the use of certain broad-spectrum antibiotics in secondary care. However, robust baseline antibiotic use data are lacking for hospitalised children. In this study, we aim to describe, compare and explain the prescription patterns of antibiotics within and between paediatric units in the UK and to provide a baseline for antibiotic prescribing for future improvement using CQUIN AMR guidance.

METHODS

We conducted a cross-sectional study using a point prevalence survey (PPS) in 61 paediatric units across the UK. The standardised study protocol from the Antibiotic Resistance and Prescribing in European Children (ARPEC) project was used. All inpatients under 18 years of age present in the participating hospital on the day of the study were included except neonates.

RESULTS

A total of 1247 (40.9%) of 3047 children hospitalised on the day of the PPS were on antibiotics. The proportion of children receiving antibiotics showed a wide variation between both district general and tertiary hospitals, with 36.4% ( 95% CI 33.4% to 39.4%) and 43.0% (95% CI 40.9% to 45.1%) of children prescribed antibiotics, respectively. About a quarter of children on antibiotic therapy received either a medical or surgical prophylaxis with parenteral administration being the main prescribed route for antibiotics (>60% of the prescriptions for both types of hospitals). General paediatrics units were surprisingly high prescribers of critical broad-spectrum antibiotics, that is, carbapenems and piperacillin-tazobactam.

CONCLUSIONS

We provide a robust baseline for antibiotic prescribing in hospitalised children in relation to current national stewardship efforts in the UK. Repeated PPS with further linkage to resistance data needs to be part of the antibiotic stewardship strategy to tackle the issue of suboptimal antibiotic use in hospitalised children.

Forecasting carbapenem resistance from antimicrobial consumption surveillance: Lessons learnt from an OXA-48-producing Klebsiella pneumoniae outbreak in a West London renal unit

This study aimed to forecast the incidence rate of carbapenem resistance and to assess the impact of an antimicrobial stewardship intervention using routine antimicrobial consumption surveillance data. Following an outbreak of OXA-48-producing Klebsiella pneumoniae (January 2008-April 2010) in a renal cohort in London, a forecasting ARIMA model was derived using meropenem consumption data [defined daily dose per 100 occupied bed-days (DDD/100OBD)] from 2005-2014 as a predictor of the incidence rate of OXA-48-producing organisms (number of new cases/year/100,000OBD). Interrupted times series assessed the impact of meropenem consumption restriction as part of the outbreak control. Meropenem consumption at lag -1 year (the preceding year), highly correlated with the incidence of OXA-48-producing organisms (r=0.71; P=0.005), was included as a predictor within the forecasting model. The number of cases/100,000OBD for 2014-2015 was estimated to be 4.96 (95% CI 2.53-7.39). Analysis of meropenem consumption pre- and post-intervention demonstrated an increase of 7.12 DDD/100OBD/year (95% CI 2.97-11.27; P<0.001) in the 4 years preceding the intervention, but a decrease thereafter. The change in slope was -9.11 DDD/100OBD/year (95% CI -13.82 to -4.39). Analysis of alternative antimicrobials showed a significant increase in amikacin consumption post-intervention from 0.54 to 3.41 DDD/100OBD/year (slope +0.72, 95% CI 0.29-1.15; P=0.01). Total antimicrobials significantly decreased from 176.21 to 126.24 DDD/100OBD/year (P=0.05). Surveillance of routinely collected antimicrobial consumption data may provide a key warning indicator to anticipate increased incidence of carbapenem-resistant organisms. Further validation using real-time data is needed.

SeverePseudomonas aeruginosainfections

Pseudomonas aeruginosa infections are a frequent cause of morbidity and mortality in hospitalized patients. Treatment of these infections is complicated by the intrinsic and acquired resistance of this bacterium to many commonly used antimicrobial agents. In this article, Drs Hauser and Sriram argue that careful consideration of the mechanisms by which P. aeruginosa resists the activity of antimicrobial agents is essential for optimal treatment decisions. Although many aspects of treatment of severe P. aeruginosa infections remain controversial, the authors suggest specific treatment options for patients both before and after susceptibilities are known.

Emergence of Resistance inPseudomonas aeruginosaandAcinetobacterSpecies After the Use of Antimicrobials for Burned Patients

Objectives:

To evaluate the emergence of resistance ofPseudomonas aeruginosaandAcinetobacterspecies to imipenem, ciprofloxacin, or both after the use of these drugs and to compare resistant with susceptible isolates by molecular typing.

Design:

Cohort study.

Setting:

Burn intensive care unit (ICU) with 4 beds in a tertiary-care university hospital.

Methods:

During 16 months, surveillance cultures were performed for all patients admitted to the ICU. Demographic information was obtained for each patient. Molecular typing was done by pulsed-field gel electrophoresis using restriction enzymes for 71 isolates ofP. aeruginosaandAcinetobacterspecies.

Results:

Thirty-four patients were admitted and 22 were colonized by susceptibleP. aeruginosaorAcinetobacterspecies before they used the antimicrobials. Nine (41%) of these patients had a resistant isolate after antimicrobial use: 5 had used imipenem alone, 1 had used ciprofloxacin, and 3 had used both drugs. The interval between isolation of the susceptible and resistant isolates ranged from 4 to 25 days, but was 10 or more days for 6 patients. Molecular typing revealed that susceptible and resistant isolates from each patient were different and that although there were no predominant clones among susceptible isolates, there was a predominant clone among resistant isolatesof P. aeruginosaandof Acinetobacter.

Conclusions:

Resistance was not due to the acquisition of resistance mechanisms by a previously susceptible strain, but rather to cross-transmission. Although various measures involving antimicrobial use have received great attention, it would seem that practices to prevent cross-transmission are more important in controlling resistance.

Strategies for the empirical management of infection in cancer patients with emphasis on the emergence of resistant gram-negative bacteria

Combinations of antibiotics (namely penicillins and aminoglycosides) have been advocated in the 1970s for the empirical therapy of FN in cancer patients in order to take advantage of the possible synergism between these agents and to extend the potential antimicrobial spectrum of empirical therapy. Later, with the development of potent broad spectrum antibiotics, the need for combinations became less obvious as monotherapy with these new agents appeared as effective and less toxic than previously used combinations. However, today we are facing a major challenge through the emergence of multi-resistant microrganisms. With such bacteria, we might be coming back to the pre-antibiotic era when no active agents were available. This situation is due, in part, by the excessive use of antibiotics, namely as a prophylaxis for infection, and is complicated by the fact that very few new effective antibiotics are being developed by the pharmaceutical industry. Under these circumstances, it is likely that we will have to resort to "old timers" such as the polymyxins. It is also possible that combination therapy will come back in favor to take advantage of the synergism and extend the spectrum of coverage, just as it has been the case for the management of resistant tuberculosis. At the same time, the development of multidisciplinary antimicrobial stewardship is mandatory for efficient infection control and minimizing emergence of antimicrobial resistance.

A clinical trial comparing physician prompting with an unprompted automated electronic checklist to reduce empirical antibiotic utilization

OBJECTIVES

To determine whether face-to-face prompting of critical care physicians reduces empirical antibiotic utilization compared to an unprompted electronic checklist embedded within the electronic health record.

DESIGN

Random allocation design.

SETTING

Medical ICU with high-intensity intensivist coverage at a tertiary care urban medical center.

PATIENTS

Two hundred ninety-six critically ill patients treated with at least 1 day of empirical antibiotics.

INTERVENTIONS

For one medical ICU team, face-to-face prompting of critical care physicians if they did not address empirical antibiotic utilization during a patient's daily rounds. On a separate medical ICU team, attendings and fellows were trained once to complete an electronic health record-embedded checklist daily for each patient, including a question asking whether listed empirical antibiotics could be discontinued.

MEASUREMENTS AND MAIN RESULTS

Prompting led to a more than four-fold increase in discontinuing or narrowing of empirical antibiotics compared to use of the electronic checklist. Prompted group patients had a lower proportion of patient-days on which empirical antibiotics were administered compared to electronic checklist group patients (63.1% vs 70.0%, p = 0.002). Mean proportion of antibiotic-days on which empirical antibiotics were used was also lower in the prompted group, although not statistically significant (0.78 [0.27] vs 0.83 [0.27], p = 0.093). Each additional day of empirical antibiotics predicted higher risk-adjusted mortality (odds ratio, 1.14; 95% CI, 1.05-1.23). Risk-adjusted ICU length of stay and hospital mortality were not significantly different between the two groups.

CONCLUSIONS

Face-to-face prompting was superior to an unprompted electronic health record-based checklist at reducing empirical antibiotic utilization. Sustained culture change may have contributed to the electronic checklist having similar empirical antibiotic utilization to a prompted group in the same medical ICU 2 years prior. Future studies should investigate the integration of an automated prompting mechanism with a more generalizable electronic health record-based checklist.

Behavior change strategies to influence antimicrobial prescribing in acute care: a systematic review

BACKGROUND

Antimicrobial use in acute care is widely reported to be suboptimal. Inappropriate use of antimicrobials is a major contributing factor to the emergence of multidrug resistance and health care-associated infection. Addressing prescribing behavior is a key component of antimicrobial stewardship.

METHODS

We performed a novel systematic review of both qualitative and quantitative literature on antimicrobial prescribing behavior in acute care. We assessed the extent to which behavioral sciences and social marketing were used and whether this could be related to the effectiveness of reported outcomes. MEDLINE, Excerpta Medica Database (EMBASE), Applied Social Sciences Index and Abstracts (ASSIA), Business Source Complete, The Cochrane Library, PsychInfo, Database of Abstracts of Reviews of Effectiveness (DARE) and Health Management Information Consortium (HMIC) were searched for studies undertaken during the period January 1999-April 2011 and published in English.

RESULTS

Five qualitative and 5 quantitative studies met the quality criteria. Qualitative studies highlight the predominant influence of social norms, attitudes, and beliefs on antimicrobial prescribing behavior. Quantitative studies reporting interventions to optimize antimicrobial prescribing behavior do not use theoretical science or primary research to inform the design and choice of the interventions deployed.

CONCLUSIONS

Despite qualitative evidence demonstrating the impact of behavioral determinants and social norms on prescribing, these influences are not given due consideration in the design and evaluation of interventions. To ensure a better understanding of prescribing behaviors and to improve the quality of interventions and research in this area, the incorporation and application of behavioral sciences supported by appropriate multidisciplinary collaboration is recommended.

Klebsiella and extended spectrum beta-lactamases

During the past 14 years a rapid, world-wide increase in prevalence of Klebsiella pneumoniae resistant to late generation cephalosporins has occurred. A growing number of newly identified plasmid encoded beta-lactam hydrolyzing enzymes has broadened the spectrum of primitive beta-lactamases allowing inactivation of a wide variety of beta-lactam agents. The extrachromosomal genes which code for these enzymes often exist with genes expressing resistance to several other classes of antibacterial agents, potentially arming Klebsiella pneumoniae with resistance to all therapeutically available antibiotics. More focused surveillance studies and individualized strategies within institutions are necessary to reduce this insidious trend.

Emergence of antibiotic resistance during therapy for infections caused by Enterobacteriaceae producing AmpC beta-lactamase: implications for antibiotic use

Enterobacter spp., Serratia marcescens, Citrobacter freundii, and Morganella morganii are characterized by chromosomally encoded AmpC beta-lactamases and possess the ability to develop resistance upon exposure to broad-spectrum cephalosporins. To determine the incidences of the emergence of resistance during antimicrobial therapy for infections caused by these organisms and the effect of the emergence of resistance on patient outcomes, all patients who were admitted to the Asan Medical Center (Seoul, Republic of Korea) from January 2005 to June 2006 and whose clinical specimens yielded Enterobacter spp., S. marcescens, C. freundii, or M. morganii were monitored prospectively. The main end point was the emergence of resistance during antimicrobial therapy. A total of 732 patients with infections were included for analysis. The overall incidence of the emergence of antimicrobial resistance during antimicrobial therapy was 1.9% (14/732). Resistance to broad-spectrum cephalosporins, cefepime, extended-spectrum penicillin, carbapenem, fluoroquinolones, and aminoglycosides emerged during treatment in 5.0% (11/218), 0% (0/20), 2.0% (2/100), 0% (0/226), 0% (0/153), and 1.1% (1/89) of patients, respectively. The emergence of resistance to broad-spectrum cephalosporins occurred more often in Enterobacter spp. (8.3%, 10/121) than in C. freundii (2.6%, 1/39), S. marcescens (0%, 0/37), or M. morganii (0%, 0/21). Biliary tract infection associated with malignant bile duct invasion was significantly associated with the emergence of resistance to broad-spectrum cephalosporins (P = 0.024 at a significance level of 0.042, by use of the Bonferroni correction). Only 1 of the 14 patients whose isolates developed resistance during antimicrobial therapy died. The emergence of resistance was more frequently associated with broad-spectrum cephalosporins than with the other antimicrobial agents tested, especially in Enterobacter spp. However, the emergence of resistance was associated with a low risk of mortality.

Predictors of In-Hospital Mortality for Bloodstream Infections Caused byEnterobacterSpecies orCitrobacter freundii

STUDY OBJECTIVE

To identify predictors of in-hospital mortality among patients with bacteremia caused by Enterobacter cloacae, Enterobacter aerogenes, or Citrobacter freundii.

DESIGN

Retrospective cohort study.

SETTING

1300-bed tertiary academic medical center.

PATIENTS

One hundred twenty-four patients who had bloodstream infections caused by E. cloacae (3), E. aerogenes (71), or C. freundii (50) between 1998 and 2004.

MEASUREMENTS AND MAIN RESULTS

Data from patients with bloodstream infections caused by Enterobacter sp or C. freundii were retrospectively segregated according to hospital survival (98 survivors, 26 nonsurvivors). Multiple patient characteristics and processes of care were evaluated to identify factors contributing to in-hospital mortality. Multiple logistic regression was performed based on univariate comparisons to determine independent risk factors for in-hospital mortality. Among the 124 cases of bacteremia, the crude in-hospital mortality rate was 21% (26 cases). Univariate analysis revealed that survivors were more likely to receive an aminoglycoside as part of their empiric antimicrobial regimen (40% [39/98]) compared with nonsurvivors (19% [5/26], p=0.05). Other factors related to antimicrobial therapy including choice and number of agents used did not differ between survivors and nonsurvivors (p>0.05). Vasopressor use (31% [30/98] vs 62% [16/26]), care in an intensive care unit (19% [19/98] vs 54% [14/26]), and acute renal failure (13% [13/98] vs 31% [8/26]) occurred more frequently in nonsurvivors (p<0.05). Multiple logistic regression identified resistance to second- or third-generation cephalosporins (adjusted odds ratio [OR] 5.16, 95% confidence interval [CI] 2.66-10.0, p=0.013), trimethoprim-sulfamethoxazole resistance (adjusted OR 5.44, 95% CI 2.53-11.7, p=0.027), and mechanical ventilation (adjusted OR 12.2, 95% CI 5.99-24.5, p<0.001) as independent determinants of mortality.

CONCLUSION

Among patients with Enterobacter sp or C. freundii bloodstream infections, those with trimethoprim-sulfamethoxazole-resistant or second or third-generation cephalosporin-resistant strains or those who required mechanical ventilation had an increased risk of mortality.

Comparative effects of single-dose ceftriaxone versus three oral antibiotic regimens on stool colonization by resistant bacilli in children

OBJECTIVE

The use of short-term intramuscular ceftriaxone for pediatric ambulatory conditions raises concerns regarding the promotion of resistance among colonizing enteric bacteria. This study was designed to assess the prevalence of stool colonization with resistant Gram-negative bacilli after single-dose ceftriaxone treatment compared with other regimens for acute otitis media.

METHODS

Children age 3 months to 7 years and diagnosed with acute otitis media were randomized to receive treatment with single-dose ceftriaxone or with oral cefprozil, amoxicillin or azithromycin. Stool samples were obtained at enrollment and then 3-5 days, 10-14 days, and 28-30 days after therapy was initiated and screened for the presence of facultative Gram-negative bacilli resistant to ceftriaxone, cefprozil, amoxicillin, piperacillin, piperacillin-tazobactam and tobramycin. Mean prevalence of colonization by resistant organisms for each treatment group was compared at each time point.

RESULTS

One thousand nine subjects were enrolled. The prevalence of colonization by a Gram-negative bacillus resistant to at least 1 of the screening antibiotics decreased after receipt of ceftriaxone but returned close to values measured at study entry by 30 days. A qualitatively similar pattern was noted for the 3 other regimens, but a quantitatively greater decrease in the prevalence of colonization by a resistant bacterium was noted at the 3- to 5-day and 10- to 14-day visits among azithromycin recipients (P < 0.001). Colonization by a Gram-negative bacillus resistant specifically to ceftriaxone was unusual at each study visit, regardless of treatment assignment.

CONCLUSIONS

A single intramuscular dose of ceftriaxone had a similar effect on the prevalence of antibiotic-resistant Gram-negative facultative bacilli in the stool of healthy children when compared with commonly used oral agents.

Post-operative infection by pathogenic micro-organisms in the oral cavity of patients with prostatic carcinoma

The aim of this study was to analyse the change in the oral cavity microflora of 14 patients who had undergone a radical prostatectomy for prostatic carcinoma. The detection of micro-organisms in the oral cavity was compared before and after the surgical procedure. Post-operative infection, defined as those patients who had increased Candida species counts and/or pathogenic bacteria only at the post-operative examination, was observed in 10 patients. Six patients showed increased Candida species counts at the post-operative examination compared with the pre-operative examination. In five patients, pathogenic bacterial species were detected at the post-operative examination but not at the pre-operative examination. One patient had detectable pathogenic bacterial species only at the post-operative examination along with increased Candida species counts. Our findings suggest that pre-operative oral hygiene to remove bacterial and Candida species from patients who are scheduled for surgical procedures is important for satisfactory clinical outcomes.

Limiting the emergence of extended-spectrum Beta-lactamase-producing enterobacteriaceae: influence of patient population characteristics on the response to antimicrobial formulary interventions

BACKGROUND

Effective methods to control the emergence of extended-spectrum beta -lactamase-producing Escherichia coli and Klebsiella species (ESBL-EK) remain unclear. Variations in the patient populations at different hospitals may influence the effect of antimicrobial formulary interventions.

METHODS

To examine variations across hospitals in the response to antimicrobial interventions (ie, restriction of ceftazidime and ceftriaxone) designed to curb the spread of ESBL-EK, we conducted a 5-year quasi-experimental study. This study was conducted at 2 hospitals within the same health system: Hospital A is a 625-bed academic medical center, and Hospital B is a 344-bed urban community hospital. All adult patients with a healthcare-acquired clinical culture of ESBL-EK from July 1, 1997 through December 31, 2002 were included.

RESULTS

After the interventions, the use of ceftriaxone decreased by 86% at Hospital A and by 95% at Hospital B, whereas the use of ceftazidime decreased by 95% at Hospital A and by 97% at Hospital B. The prevalence of ESBL-EK at Hospital A decreased by 45% (P < .001), compared with a 22% decrease at Hospital B (P = .36). The following variables were significantly more common among ESBL-EK-infected patients at Hospital B: residence in a long-term care facility (adjusted odds ratio, 3.77 [95% confidence interval, 1.70-8.37]), advanced age (adjusted odds ratio, 1.04 [95% confidence interval, 1.01-1.06]), and presence of a decubitus ulcer (adjusted odds ratio, 4.13 [95% confidence interval, 1.97-8.65]).

CONCLUSIONS

The effect of antimicrobial formulary interventions intended to curb emergence of ESBL-EK may differ substantially across institutions, perhaps as a result of differences in patient populations. Variability in the epidemiological profiles of ESBL-EK isolates at different hospitals must be considered when designing interventions to respond to these pathogens.

Beta-lactam antibiotic resistance in aerobic commensal fecal flora of newborns

BACKGROUND

The purpose of the present paper was to prospectively determine the rate of beta-lactam antibiotic resistance in commensal fecal flora of newborns and the risk factors leading to this colonization.

METHODS

One hundred and eighteen newborns in the neonatal intensive care unit (NICU) group (n = 38), the neonatal ward group (n = 36), and the control group (n = 44) were enrolled. Three or four stool samples were obtained from each infant, 15 days apart. Bacterial growth in Eozin Methylene Blue (EMB) agar + 10 microg ampicillin/mL was considered to be ampicillin-resistant bacteria, and antibiotic susceptibility and extended spectrum beta-lactamases (ESBL) production was investigated in those bacteria.

RESULTS

Colonization with ampicillin-resistant commensal fecal flora microorganisms was determined in 75.2% of 367 stool samples. Klebsiella spp. and Escherichia coli were identified in 59% and 41% of the samples, respectively. The lowest rate of ampicillin-resistant bacterial colonization was determined in the NICU group. Microorganisms producing ESBL were identified in 33.7% of 367 stool samples. Fifty-one and 73 of ampicillin-resistant E. coli and Klebsiella spp. isolates were determined to produce ESBL, respectively. There was no difference with respect to colonization with ESBL-producing microorganisms between the three groups. When risk factors related to colonization with ESBL-producing microorganisms in stool samples were evaluated through the whole study period, very low birthweight, vaginal delivery, infant antibiotic usage, maternal antibiotic usage, male sex and premature rupture of membranes were determined as risk factors, while feeding with nasogastric tube was identified as a protective factor. When the risk factors related to colonization with ESBL-producing bacteria in stool samples after discharge from the hospital were evaluated, failure to feed breast milk was determined as the only risk factor.

CONCLUSIONS

To decrease mortality and morbidity due to infection caused by resistant microorganisms colonized in the intestine flora of the infant, protection of normal non-pathogenic bacterial colonization is important. This can be provided by feeding neonates with breast milk, application of infection control measures efficiently, and limitation of antibiotic usage only to strict clinical indications.

Recurrent Klebsiella pneumoniae mycotic aneurysm in a diabetic patient and emergence of an extended-spectrum beta-lactamase (CTX-M-24)-containing Klebsiella pneumoniae strain after prolonged treatment with first-generation cephalosporins for mycotic aneurysm

A 68-year-old diabetic woman suffered from mycotic aneurysm due to Klebsiella pneumoniae over her abdominal aorta; she received surgical intervention, followed by treatment with first-generation cephalosporins for 6 months. She was hospitalized again 11 months later because of another episode of mycotic aneurysm caused by K. pneumoniae on her thoracic aorta. Fingerprinting generated by pulsed-field gel electrophoresis and infrequent-restriction-site polymerase indicated K. pneumoniae isolates of the identical clonal strain were responsible for these two mycotic-aneurysm episodes. Unfortunately, nosocomial pneumonia developed at the second hospitalization; blood and purposefully sampled feces specimen cultures both grew CTX-M-24-producing K. pneumoniae, which were of the same strain and genetically nonrelated to the K. pneumoniae strain causing mycotic aneurysms earlier. This is the first report on infection due to CTX-M-24-producing K. pneumoniae. It is unclear whether the prolonged use of first-generation cephalosporins in this case selected a strain of enteric organism possessing the ESBL in question, which was capable of passing this ESBL plasmid to the K. pneumoniae strain causing the nosocomial infection. This report suggests that further observation is needed before one can draw a conclusion on the possibility of the selection of ESBL enteric organism by extensive exposure to first-generation cephalosporins.

Resistance to antimicrobial agents: an update

Decades of overuse and misuse of antibiotics have turned the resistance problem into a crisis. Preventive and corrective measures are urgently needed. This article presents a broad overview of the status of antimicrobial resistance. Resistance in key bacterial pathogens such as enterococci, staphylococci, pneumococci, and gram-negative bacilli; resistance to fluoroquinolones, third-generation cephalosporins, and the carbapenems; and mechanisms of resistance are discussed. The article also reviews the adverse impact of resistance on outcomes for patients with nosocomial infections. Finally, a brief overview of how the medical community can face its moment of truth is presented.

Risk factors for multidrug-resistant Pseudomonas aeruginosa nosocomial infection

A case-control study was conducted in a university hospital to determine the risk factors for nosocomial infection with multidrug-resistant Pseudomonas aeruginosa (MDR-PA) among all hospitalized patients and among those with a nosocomial infection due to P. aeruginosa. Eighty patients infected with MDR-PA, 75 infected with a non-MDR phenotype and 240 random controls were included in the 12-month study. Among all hospitalized patients, age, severity index, having a bedridden condition, transfer from other units, nasogastric feeding, urinary catheterization and exposure to beta-lactams (OR=2.5) or fluoroquinolones (OR=4.1) in the seven days before infection were linked to nosocomial infection due to MDR-PA. Among patients infected by P. aeruginosa, exposure to fluoroquinolones (OR=4.7) or surgery (OR=0.5) were linked to the isolation of MDR-PA. This study showed that, in addition to urinary catheterization, nasogastric feeding is an important risk factor in MDR-PA infection. Indeed, an imbalance in gut flora, modifications to the mucous membranes due to the use of nasogastric feeding and the selection pressures exerted by antibiotics were implicated in the occurrence of this infection.

Epidemiological risk factors for isolation of ceftriaxone-resistant versus -susceptible citrobacter freundii in hospitalized patients

Antimicrobial resistance is an emerging problem among nosocomial bacteria. Risk factors for the recovery of ceftriaxone-resistant (CRCF) or -susceptible (CSCF) Citrobacter freundii in clinical cultures from hospitalized patients were determined by using a case-case-control study design. CRCF was isolated from 43 patients (case group 1) and CSCF was isolated from 87 patients (case group 2) over a 3-year period. Risk factors for CRCF were exposure to imipenem (odds ratio [OR], 7.5; 95% confidence interval [CI], 1.2 to 45.4), broad-spectrum cephalosporins (OR, 6.9; 95% CI, 1.8 to 26.7), vancomycin (OR, 3.0; 95% CI, 1.2 to 7.4), or piperacillin-tazobactam (OR, 2.6; 95% CI, 1.1 to 6.2), as well as hospital length of stay >or=1 week (OR, 3.6; 95% CI, 1.3 to 10.2) and intensive care unit (ICU) stay (OR, 2.6; 95% CI, 1.1 to 6.2). Risk factors for CSCF were peripheral vascular disease (OR, 23.2; 95% CI, 4.3 to 124.6), AIDS (OR, 9.5; 95% CI, 1.6 to 55.5), cerebrovascular disease (OR, 4.2; 95% CI, 1.6 to 10.8), and ICU stay (OR, 3.1; 95% CI, 1.8 to 5.4).