Infection control measures to limit antimicrobial resistance

Putative new combination vaccine candidates identified by reverse vaccinology and genomic approaches to control enteric pathogens

OBJECTIVES

The pathogenic microorganisms that cause intestinal diseases can significantly jeopardize people's health. Currently, there are no authorized treatments or vaccinations available to combat the germs responsible for intestinal disease.

METHODS

Using immunoinformatics, we developed a potent multi-epitope Combination (combo) vaccine versus Salmonella and enterohemorrhagic E. coli. The B and T cell epitopes were identified by performing a conservancy assessment, population coverage analysis, physicochemical attributes assessment, and secondary and tertiary structure assessment of the chosen antigenic polypeptide. The selection process for vaccine development included using several bioinformatics tools and approaches to finally choose two linear B-cell epitopes, five CTL epitopes, and two HTL epitopes.

RESULTS

The vaccine had strong immunogenicity, cytokine production, immunological properties, non-toxicity, non-allergenicity, stability, and potential efficacy against infections. Disulfide bonding, codon modification, and computational cloning were also used to enhance the stability and efficacy of expression in the host E. coli. The vaccine's structure has a strong affinity for the TLR4 ligand and is very durable, as shown by molecular docking and molecular modeling. The results of the immunological simulation demonstrated that both B and T cells had a heightened response to the vaccination component.

CONCLUSIONS

The comprehensive in silico analysis reveals that the proposed vaccine will likely elicit a robust immune response against pathogenic bacteria that cause intestinal diseases. Therefore, it is a promising option for further experimental testing.

Infection control in the intensive care unit

Nosocomial infections are common in many hospital departments, but particularly so on the intensive care unit, where they affect some 20 to 30% of patients. While early diagnosis and appropriate treatment are, of course, important, perhaps the greatest challenge is in the application of techniques to limit the development of such infections. This review will briefly discuss some of the background pathophysiology and epidemiology of nosocomial infection, and then focus on general and infection-specific preventative strategies individually and as part of broader infection-control programs with infection surveillance.

Antimicrobial use, incidence, etiology and resistance patterns in bacteria causing ventilator-associated pneumonia in a clinical-surgical intensive care unit

INTRODUCTION

Antimicrobial resistance is an increasing threat in hospitalized patients, and inappropriate empirical antimicrobial therapy is known to adversely affect outcomes in ventilator-associated pneumonia (VAP). The aim of this study was to evaluate antimicrobial usage, incidence, etiology, and antimicrobial resistance trends for prominent nosocomial pathogens causing ventilator-associated pneumonia in a clinical-surgical intensive care unit (ICU).

METHODS

Gram-negative bacilli and Staphylococcus aureus causing VAP, as well as their antimicrobial resistance patterns and data on consumption (defined daily dose [DDD] per 1,000 patient days) of glycopeptides, extended-spectrum cephalosporins, and carbapenems in the unit were evaluated in two different periods (A and B).

RESULTS

Antimicrobial use was high, mainly of broad-spectrum cephalosporins, with a significant increase in the consumption of glycopeptides (p < 0.0001) and carbapenems (p < 0.007) in period B. For Acinetobacter baumannii and members of the Enterobacteriaceae family, 5.27- and 3.06-fold increases in VAPs, respectively, were noted, and a significant increase in resistance rates was found for imipenem-resistant A. baumannii (p = 0.003) and third-generation cephalosporins-resistant Enterobacteriaceae (p = 0.01) isolates in this same period.

CONCLUSIONS

Our results suggest that there is a link between antibiotics usage at institutional levels and resistant bacteria. The use of carbapenems was related to the high rate of resistance in A. baumannii and therefore a high consumption of imipenem/meropenem could play a major role in selective pressure exerted by antibiotics in A. baumannii strains.

Antibiotic consumption and healthcare-associated infections caused by multidrug-resistant gram-negative bacilli at a large medical center in Taiwan from 2002 to 2009: implicating the importance of antibiotic stewardship

Background

Better depicting the relationship between antibiotic consumption and evolutionary healthcare-associated infections (HAIs) caused by multidrug-resistant Gram-negative bacilli (MDR-GNB) may help highlight the importance of antibiotic stewardship.

Methodology/Principal Findings

The correlations between antibiotic consumption and MDR-GNB HAIs at a 2,700-bed primary care and tertiary referral center in Taiwan between 2002 and 2009 were assessed. MDR-GNB HAI referred to a HAI caused by MDR-Enterobacteriaceae, MDR-Pseudomonas aeruginosa or MDR-Acinetobacter spp. Consumptions of individual antibiotics and MDR-GNB HAI series were first evaluated for trend over time. When a trend was significant, the presence or absence of associations between the selected clinically meaningful antibiotic resistance and antibiotic consumption was further explored using cross-correlation analyses. Significant major findings included (i) increased consumptions of extended-spectrum cephalosporins, carbapenems, aminopenicillins/β-lactamase inhibitors, piperacillin/tazobactam, and fluoroquinolones, (ii) decreased consumptions of non-extended-spectrum cephalosporins, natural penicillins, aminopenicillins, ureidopenicillin and aminoglycosides, and (iii) decreasing trend in the incidence of the overall HAIs, stable trends in GNB HAIs and MDR-GNB HAIs throughout the study period, and increasing trend in HAIs caused by carbapenem-resistant (CR) Acinetobacter spp. since 2006. HAIs due to CR-Acinetobacter spp. was found to positively correlate with the consumptions of carbapenems, extended-spectrum cephalosporins, aminopenicillins/β-lactamase inhibitors, piperacillin/tazobactam and fluoroquinolones, and negatively correlate with the consumptions of non-extended-spectrum cephalosporins, penicillins and aminoglycosides. No significant association was found between the increased use of piperacilllin/tazobactam and increasing HAIs due to CR-Acinetobacter spp.

Conclusions

The trend in overall HAIs decreased and trends in GNB HAIs and MDR-GNB HAIs remained stable over time suggesting that the infection control practice was effective during the study period, and the escalating HAIs due to CR- Acinetobacter spp. were driven by consumptions of broad-spectrum antibiotics other than piperacillin/tazobactam. Our data underscore the importance of antibiotic stewardship in the improvement of the trend of HAIs caused by Acinetobacter spp.

Changing trends in antimicrobial resistance of major bacterial pathogens, 1985-2005: a study from a medical center in northern Taiwan

BACKGROUND

Antimicrobial resistance is a major health problem worldwide. We evaluated the antimicrobial resistance trends of 16 major bacterial pathogens at a tertiary medical center in northern Taiwan.

METHODS

We conducted a retrospective review of annual summary documents for antimicrobial susceptibility of clinically isolated gram-positive and gram-negative bacteria from 1985 to 2005. The numbers of isolates and susceptibilities were calculated for three 7-year periods: first period, 1985-1991; second period, 1992-1998; and the third period, 1999-2005.

RESULTS

During the 21-year period, 219,715 bacterial pathogens were identified. A significant increase in incidence over time was found for methicillin-resistant Staphylococcus aureus, methicillin-resistant S epidermidis, penicillin-nonsusceptible Streptococcus pneumoniae, erythromycin-resistant S pneumoniae, vancomycin-resistant enterococci, cefotaxime/ceftriaxone-resistant Escherichia coli and Klebsiella pneumoniae, and imipenem-resistant Acinetobacter baumannii. Additionally, a significant increase in ciprofloxacin resistance rates over time from 1996 to 2005 was noted for E coli, Enterobacter cloacae, and A baumannii (through 1997 to 2005). However, a significant decrease in erythromycin resistance rate with time from 1999 to 2005 was found for Groups A and B streptococci, non-A, B, D streptococci, and S pneumoniae.

CONCLUSION

Resistance to antimicrobial agents increased rapidly in the past two decades in Taiwan and has become very common in major bacterial pathogens. Continuous enforcement of policies to limit use of antimicrobial agents and active surveillance of antimicrobial resistance through a nationwide system are both warranted.

Diagnosis and management of infectious complications in critically ill patients with cancer

Cancer and its treatments lead to profound suppression of innate and acquired immune function. In this population, bacterial infections are common and may rapidly lead to overwhelming sepsis and death. Furthermore, infections caused by viral and fungal pathogens should be considered in patients who have specific immune defects. As cancer therapies have become more aggressive the risk for infection has increased and many patients require intensive care support. Despite improvements in long-term survival, infections remain a common complication of cancer therapy and accounts for the majority of chemotherapy-associated deaths. By understanding the host defense impairments and likely pathogens clinicians will be better able to guide diagnosis and management of this unique population.

Implementation of antibiotic rotation protocol improves antibiotic susceptibility profile in a surgical intensive care unit

BACKGROUND

Antibiotic rotation has been proposed as a way to potentially reduce the development of antimicrobial resistant bacteria in intensive care units. We assessed the effect of an antibiotic rotation protocol on the antibiotic susceptibility profiles of three clinically relevant gram-negative microorganisms within our surgical intensive care unit (SICU).

METHODS

Our SICU implemented an antibiotic rotation protocol in 2003. Four antibiotics (piperacillin/tazobactam, imipenem/cilastin, ceftazidime, and ciprofloxacin) were rotated as the primary antibiotic used to treat suspected gram-negative infections every month, with the four-drug cycle being repeated every 4 months. Antibiotic susceptibility data for three microorganisms (Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae) were collected for the year before (2002) and the year after (2004) the implementation of the rotation protocol. Changes in antimicrobial susceptibility rates were analyzed for the three microorganisms. As a comparison, a similar analysis was conducted for microorganisms isolated from our medical intensive care unit, where no antibiotic rotation protocol was implemented.

RESULTS

Implementation of an antibiotic rotation protocol in our SICU resulted in a significant increase in the percentage of P. aeruginosa isolates sensitive to ceftazidime (67% in 2002 vs. 92% in 2004, p = 0.002) and piperacillin/tazobactam (78% in 2002 vs. 92% in 2004, p = 0.043). Isolates from the medical intensive care unit did not demonstrate an increase in antimicrobial susceptibility. In fact, the susceptibility of E. coli to piperacillin/tazobactam decreased during this time period (p = 0.047).

CONCLUSIONS

Implementation of an antibiotic rotation protocol in our SICU resulted in overall improvement in the antibiotic susceptibility profile of gram-negative microorganisms relative to our medical intensive care unit, where such a protocol was not used.

Infectious Complications of Cancer Therapy

Advances in the management of cancer, particularly the development of new chemotherapeutic agents, have greatly improved the survival and outcome of patients with hematologic malignancies and solid tumors; overall 5-year survival rates in cancer patients have improved from 39% in the 1960s to 60% in the 1990s.1 However, infection, caused by both the underlying malignancy and cancer chemotherapy, particularly myelosuppressive chemotherapy, remains a persistent challenge.

Relationships between antimicrobial use and antimicrobial resistance in Gram-negative bacteria causing nosocomial infections from 1991-2003 at a university hospital in Taiwan

This study was conducted to evaluate the relationship between antimicrobial resistance and antimicrobial use in a university hospital in Taiwan. Disk susceptibility data of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus spp., Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia and other non-fermentative Gram-negative bacilli causing nosocomial infections were evaluated. Data on annual patient-days and annual consumption (defined daily dose (DDD) per 1000 patient-days) of extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime, flumoxef, cefepime and cefpirome), β-lactam–β-lactamase inhibitor combinations (ticarcillin/clavulanic acid and piperacillin/tazobactam), carbapenems (imipenem and meropenem), aminoglycosides (amikacin, gentamicin and tobramycin), fluoroquinolones (ciprofloxacin (oral and injectable) and oral levofloxacin and moxifloxacin) from 1991 to 2003 were analysed. Increasing trends of incidences of several of these bacteria causing all nosocomial infections or nosocomial bloodstream infections were noted from 1991 to 2003. The annual patient-days of the hospital significantly increased, from 360 210 in 1991 to 672 676 in 2002 (linear regression analysis, P < 0.05), but slightly decreased in 2003 (629 168) owing to the severe acute respiratory syndrome epidemic in Taiwan. The rise in cefotaxime-resistant or ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa was significantly correlated with increased consumption of extended-spectrum cephalosporins, β-lactam–β-lactamase inhibitor combinations, carbapenems, fluoroquinolones and aminoglycosides (for ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa only) in the hospital (Pearson's correlation coefficient, r > 0.72 (or <−0.72) and P-value < 0.05). Increased ciprofloxacin-resistant K. pneumoniae and meropenem-resistant Acinetobacter spp. was significantly associated with the increased usage of extended-spectrum cephalosporins but not with the other four classes of antibiotics. This 13-year study in a hospital demonstrated significant changes in antimicrobial use, which may have affected antimicrobial resistance in certain Gram-negative bacteria at the hospital.

Judicious Use of Antimicrobials in the Critical Care Setting

This article reviews the judicious use of antibiotics in an intensive care setting. Risk factors for both infection and antimicrobial resistance are discussed. Various methods hospitals can apply to promote the optimal use of antibiotics also are reviewed. These methods include empiric therapy, antibiotic cycling, treatment guidelines and protocols, and antibiotic susceptibility monitoring.

Hand hygiene: a frequently missed lifesaving opportunity during patient care

Health care-associated infections constitute one of the greatest challenges of modern medicine. Despite compelling evidence that proper hand washing can reduce the transmission of pathogens to patients and the spread of antimicrobial resistance, the adherence of health care workers to recommended hand-hygiene practices has remained unacceptably low. One of the key elements in improving hand-hygiene practice is the use of an alcohol-based hand rub instead of washing with soap and water. An alcohol-based hand rub requires less time, is microbiologically more effective, and is less irritating to skin than traditional hand washing with soap and water. Therefore, alcohol-based hand rubs should replace hand washing as the standard for hand hygiene in health care settings in all situations in which the hands are not visibly soiled. It is also important to change gloves between each patient contact and to use hand-hygiene procedures after glove removal. Reducing health care-associated infections requires that health care workers take responsibility for ensuring that hand hygiene becomes an everyday part of patient care.

Multiresistant coagulase-negative staphylococci disseminate frequently between intubated patients in a multidisciplinary intensive care unit

Introduction

The intensive care unit is burdened with a high frequency of nosocomial infections often caused by multiresistant nosocomial pathogens. Coagulase-negative staphylococci (CoNS) are reported to be the third causative agent of nosocomial infections and the most frequent cause of nosocomial bloodstream infections. CoNS are a part of the normal microflora of skin but can also colonize the nasal mucosa, the lower airways and invasive devices. The main aim of the present study was to investigate colonization and the rate of cross-transmissions of CoNS between intubated patients in a multidisciplinary intensive care unit.

Materials and methods

Twenty consecutive patients, ventilated for at least 3 days, were included. Samples were collected from the upper and lower airways. All samples were cultured quantitatively and CoNS were identified by morphology and biochemical tests. A total of 199 CoNS isolates from 17 patients were genetically fingerprinted by pulsed-field gel electrophoresis in order to identify clones and to monitor dissemination within and between patients.

Results

An unexpected high number of transmission events were detected. Five genotypes were each isolated from two or more patients, and 14/20 patients were involved in at least one and up to eight probable transmission events.

Conclusions

A frequent transmission of CoNS was found between patients in the intensive care unit. Although transmission of bacteria does not necessarily lead to infection, it is nevertheless an indication that infection control measures can be improved.

Bioavailability of gatifloxacin by gastric tube administration with and without concomitant enteral feeding in critically ill patients

OBJECTIVE

Sequential intravenous-to-oral antimicrobial therapy with highly bioavailable antiinfective agents such as the fluoroquinolones may improve patient safety and decrease cost of infection management. However, physiologic changes associated with critical illness may alter drug absorption, distribution, and clearance, and concomitant enteral feeding may decrease fluoroquinolone bioavailability. We evaluated the effect of critical illness and concomitant gastric tube feeding on gatifloxacin bioavailability.

DESIGN

Prospective, randomized, single-dose, two-way crossover, pharmacokinetic study. SETTINGA tertiary, level-one, trauma center.

PATIENTS

Sixteen critically ill patients (baseline Acute Physiology and Chronic Health Evaluation II score >or=16) tolerating enteral nutrition administered by gastric tube (NG) for >or=12 hrs were randomized to receive gatifloxacin concurrently with continuous tube feeding or with interrupted tube feeds. Patients with renal insufficiency or those receiving concomitant fluoroquinolone therapy or postpyloric feeding were excluded. Patients received gatifloxacin 400 mg either by the intravenous or NG route followed by the alternative dosage form after a 72-hr washout period.

MEASUREMENTS AND MAIN RESULTS

Serial serum gatifloxacin concentrations (from 5 mins to 24 hrs) were analyzed using a validated high-performance liquid chromatography method. Bioavailability was determined as the ratio of NG/intravenous area under the concentration-time curve (AUC infinity ) measured by the trapezoidal method. Although there was no difference in the bioavailability between NG (AUC infinity : 38.0 [range 20.1 to 48.5] microg x h/mL) and intravenous (AUC infinity : 39.5 [range 24.1 to 63.1] microg x h/mL, p =.60) gatifloxacin (bioavailability: 98.5% [range 61.1% to 119.7%]), a wide variability was observed in three of eight patients (>30% reduction in bioavailability). Concomitant gastric tube feeding did not affect gatifloxacin bioavailability (interrupted tube feeds: 98.5% [range 61.1% to 119.7%]; continuous tube feeding: 109.0% [range 86.2% to 142.1%]; p =.42). Neither a period nor differential carryover effect was observed.

CONCLUSIONS

Although concomitant tube feeding did not affect gatifloxacin bioavailability, critical illness resulted in significant variability that may complicate the role of gatifloxacin in sequential intravenous-to-oral therapy. More research is needed to identify those patients in whom gatifloxacin bioavailability is reduced and for whom an empirical increase in gatifloxacin dose should be considered.

Effect of education and performance feedback on handwashing: the benefit of administrative support in Argentinean hospitals

BACKGROUND

Patients admitted to hospitals are at risk of acquiring nosocomial infections. Many peer-reviewed studies show that handwashing (HW) significantly reduces hospital infections and mortality. Our objective was to evaluate the effects of HW by health care workers (HCW) before contact with patients in 3 Argentinean hospitals. We performed an observational study of HCW to measure the effect of 2 interventions: education alone and education plus performance feedback.

METHODS

A total of 3 hospitals were studied for adherence to a HW protocol. The observed HCW included physicians, nursing personnel, and ancillary staff. After initial observations to establish baseline rates of HW (phase 1), we evaluated the effect of education alone (phase 2), followed by education plus performance feedback (phase 3). We also evaluated the relationship between the administrative support and HW adherence.

RESULTS

We observed 15,531 patient contacts in 3 hospitals. The baseline rate of HW before contact with patients was 17%. With education, HW before contact with the patients increased to 44% (relative risk 2.65; 95% confidence interval 2.33-3.02; P <.001). Using education and performance feedback HW further increased to 58% (relative risk 1.86; 95% confidence interval 1.38-2.51; P <.001). In the private hospitals where administrative support for the HW program was significantly greater, HW compliance was significantly higher (logistic regression analysis: odds ratio 5.57; 95% confidence interval 5.25-6.31; P <.001).

CONCLUSIONS

In this study, HW policies and education of HCW significantly improved HCW adherence to the HW protocol, however, when performance feedback was incorporated, the HW compliance increased to a greater degree. We identified that administrative support provides a positive influence in efforts to improve HW adherence.

Moving from recommendation to implementation and audit: part 2. Review of interventions and audit

There are multiple interventions available that may help to control the development and spread of resistance to antimicrobial agents in bacteria implicated in community-acquired respiratory tract infections. Unfortunately, very few studies have assessed the effectiveness of these interventions using objective end-points, such as reduction in resistance rates and improvement in clinical outcomes. Most interventions are centered on reducing inappropriate or unnecessary use of antibiotics; others focus on reducing disease burden and bacterial colonization. With regard to antibiotic use, efforts should be concentrated at both the prescriber and consumer levels. Interventions that target prescribers include: provision of educational materials; strategies and tools to improve diagnosis; implementation of practice guidelines; personalized interactive sessions with feedback on the practice profile; and use of delayed prescription and alternative prescribing strategies. Optimal results are usually obtained when these interventions are combined with consumer education. Regulatory interventions (e.g. licensing regulations and controlled access to drugs), restrictions in the use of agents for growth promotion in animals, and use of nonantimicrobial therapies (e.g. probiotics) may help further to reduce inappropriate antibiotic use and thereby decrease the selective pressure for development of resistance. Infection-control strategies, public health measures, vaccination programs, and new antibiotics all have a role in minimizing the spread of resistant organisms. Ideally, resistance-control programs should include predefined criteria for success and integral audit processes based on objective end-points (antibiotic use, resistance trends, and health outcomes). Standardization of data collection is imperative so that the relative merits of various interventions can be compared. Effective implementation and audit of interventions is often difficult in developing countries owing to poor health-care infrastructures, lack of resources, poor education/training, and minimal regulatory controls on the supply and quality of antimicrobials. Substantial support from governments and health-care organizations across the globe is required to initiate and sustain effective intervention programs to control antimicrobial resistance.

Nosocomial and ventilator-associated pneumonias: developing country perspective

Nosocomial pneumonias are recognized as an important cause of morbidity and mortality in industrialized nations. Emerging data show that they play a similar role in the developing world. A host of extrinsic and intrinsic factors predispose individuals to the development of pneumonias, and a modification of some of these factors provides a low cost solution to prevention of pneumonias. The ideal modality for microbiologic diagnosis of pneumonia remains to be determined. Recent data suggest that there is no difference in outcome when noninvasive techniques are compared with invasive techniques. Antimicrobial resistance is a rapidly increasing problem globally, and combating this with appropriate antibiotic policies, close surveillance, and physician education is essential.