Risk of resistance related to antibiotic use before admission in patients with community-acquired bacteraemia

From Pathophysiological Hypotheses to Case-Control Study Design: Resistance from Antibiotic Exposure in Community-Onset Infections

Antimicrobial resistance is a global public health concern, at least partly due to the misuse of antibiotics. The increasing prevalence of antibiotic-resistant infections in the community has shifted at-risk populations into the general population. Numerous case-control studies attempt to better understand the link between antibiotic use and antibiotic-resistant community-onset infections. We review the designs of such studies, focusing on community-onset bloodstream and urinary tract infections. We highlight their methodological heterogeneity in the key points related to the antibiotic exposure, the population and design. We show the impact of this heterogeneity on study results, through the example of extended-spectrum β-lactamases producing Enterobacteriaceae. Finally, we emphasize the need for the greater standardization of such studies and discuss how the definition of a pathophysiological hypothesis specific to the bacteria-resistance pair studied is an important prerequisite to clarify the design of future studies.

Healthcare-associated infections over an eight year period in a large university hospital in Sicily (Italy, 2011-2018)

Background

Up to 7% of hospitalised patients acquire at least one healthcare-associated infection (HAI). The aim of the present study was to quantify the burden of HAIs in an Italian hospital, identifying involved risk factors.

Methods

Prevalence point study carried out from 2011 to 2018. For each recruited patient, a data entry form was compiled including information on demographics, hospital admission, risk factors, antimicrobial treatment, and infection if present.

Results

A total of 2844 patients were included and 218 (7.03%) reported an infection. HAI prevalence rates showed a significant increase (average annual per cent change (AAPC) +33.9%; p=0.018) from 2011 to 2014 whereas from 2014 to 2018 a gradual decline was observed (AAPC -6.15%; p=0.35). Urinary tract infection was the most common HAI (25.2%) and a total of 166 (76.1%) pathogens were isolated from 218 infections. Enterococcus and Klebsiella species were the most prevalent pathogens, causing 15.1% and 14.5% of HAIs, respectively. A significant higher risk of HAIs was found in patients exposed to central catheter (adjusted odds ratio (adj-OR)=5.40), peripheral catheter (adj-OR=1.89), urinary catheter (adj-OR=1.46), National Healthcare Safety Network surgical intervention (adj-OR=1.48), ultimately fatal disease (adj-OR=2.19) or rapidly fatal disease (adj-OR=2.09) and in patients with longer hospital stay (adj-OR=1.01).

Conclusion

Intervention programmes based on guidelines dissemination and personnel training can contribute to reduce the impact of HAI. Moreover, McCabe score can be a very powerful and efficient predictor of risk for HAI. Finally, an unexpected very high burden of disease due to Enterobacteriaceae and Gram positive cocci that could be related to the frequent use of carbapenems and third generation cephalosporins in this hospital was found.

Healthcare-Associated Clostridium difficile Infections are Sustained by Disease from the Community

Clostridium difficile infections (CDIs) are some of the most common hospital-associated infections worldwide. Approximately 5% of the general population is colonised with the pathogen, but most are protected from disease by normal intestinal flora or immune responses to toxins. We developed a stochastic compartmental model of CDI in hospitals that captures the condition of the host's gut flora and the role of adaptive immune responses. A novel, derivative-based method for sensitivity analysis of individual-level outcomes was developed and applied to the model. The model reproduced the observed incidence and recurrence rates for hospitals with high and moderate incidence of hospital-acquired CDI. In both scenarios, the reproduction number for within-hospital transmission was less than 1 (0.67 and 0.44, respectively), but the proportion colonised with C. difficile at discharge (7.3 and 6.1%, respectively) exceeded the proportion colonised at admission (5%). The transmission and prevalence of CDI were most sensitive to the average length of stay and the transmission rate of the pathogen. Recurrent infections were most strongly affected by the treatment success rate and the immune profile of patients. Transmission within hospitals is substantial and leads to a net export of colonised individuals to the broader community. However, within-hospital transmission alone is insufficient to sustain endemic conditions in hospitals without the constant importation of colonised individuals. Improved hygiene practices to reduce transmission from symptomatic and asymptomatic individuals and reduced length of stay are most likely to reduce within-hospital transmission and infections; however, these interventions are likely to have a smaller effect on the probability of recurrence. Immunising inpatients against the toxins produced by C. difficile will reduce the incidence of CDI but may increase transmission.

Increased moxifloxacin utilization associated with an unrestricted addition to a drug reimbursement formulary: A population-based analysis

OBJECTIVES

To determine whether utilization of moxifloxacin, a broad-spectrum fluoroquinolone antibiotic, has changed since its addition to the British Columbia provincial formulary in 2009 and to determine whether utilization was guideline concordant.

METHODS

BC PharmaNet prescriptions for moxifloxacin from 2001 to 2010 were anonymously linked to associated Medical Services Plan fee-for-service practitioner claims for indication-specific analysis. Prescribing trends for adults ≥18 years of age were described using defined daily dose (DDD) per 1000 person-years. Monthly utilization rates were fit to a linear regression model that controlled for seasonal variation to examine the effect of the formulary addition.

RESULTS

Utilization rose more than sevenfold throughout the study period, from 21.3 DDD per 1000 person-years in 2001 to 163.3 DDD per 1000 person-years in 2010. Although the formulary addition was not associated with an immediate increase in utilization (7.5% [95% CI -4.4% to 20.9%]; P=0.226), it was associated with an overall increase in utilization of 2.1% (95% CI 1.3% to 3.0%; P<0.001) for every month after 2009. Overall, only 29% of moxifloxacin prescriptions could be linked to a diagnostic code that was considered to be guideline concordant. In more than one-half of moxifloxacin prescriptions, the patient had not used another antibiotic in the previous 90 days. Among moxifloxacin prescriptions in which another antibiotic had been used in the previous 90 days, 41.5% were prescriptions for an alternative fluoroquinolone.

CONCLUSIONS

The formulary addition was associated with a sustained increase in moxifloxacin utilization over time. Moxifloxacin is often prescribed to patients for indications that are not guideline concordant or to patients who have not previously received first-line antibiotics.

Existing data sources for clinical epidemiology: The North Denmark Bacteremia Research Database

Bacteremia is associated with high morbidity and mortality. Improving prevention and treatment requires better knowledge of the disease and its prognosis. However, in order to study the entire spectrum of bacteremia patients, we need valid sources of information, prospective data collection, and complete follow-up. In North Denmark Region, all patients diagnosed with bacteremia have been registered in a population-based database since 1981. The information has been recorded prospectively since 1992 and the main variables are: the patient’s unique civil registration number, date of sampling the first positive blood culture, date of admission, clinical department, date of notification of growth, place of acquisition, focus of infection, microbiological species, antibiogram, and empirical antimicrobial treatment. During the time from 1981 to 2008, information on 22,556 cases of bacteremia has been recorded. The civil registration number makes it possible to link the database to other medical databases and thereby build large cohorts with detailed longitudinal data that include hospital histories since 1977, comorbidity data, and complete follow-up of survival. The database is suited for epidemiological research and, presently, approximately 60 studies have been published. Other Danish departments of clinical microbiology have recently started to record the same information and a population base of 2.3 million will be available for future studies.

Estimating household and community transmission of ocular Chlamydia trachomatis

Introduction

Community-wide administration of antibiotics is one arm of a four-pronged strategy in the global initiative to eliminate blindness due to trachoma. The potential impact of more efficient, targeted treatment of infected households depends on the relative contribution of community and household transmission of infection, which have not previously been estimated.

Methods

A mathematical model of the household transmission of ocular Chlamydia trachomatis was fit to detailed demographic and prevalence data from four endemic populations in The Gambia and Tanzania. Maximum likelihood estimates of the household and community transmission coefficients were obtained.

Results

The estimated household transmission coefficient exceeded both the community transmission coefficient and the rate of clearance of infection by individuals in three of the four populations, allowing persistent transmission of infection within households. In all populations, individuals in larger households contributed more to the incidence of infection than those in smaller households.

Discussion

Transmission of ocular C. trachomatis infection within households is typically very efficient. Failure to treat all infected members of a household during mass administration of antibiotics is likely to result in rapid re-infection of that household, followed by more gradual spread across the community. The feasibility and effectiveness of household targeted strategies should be explored.

Trachoma is a major cause of blindness worldwide and results from ocular infection with the bacterium Chlamydia trachomatis. Mass distribution of antibiotics in communities is part of the strategy to eliminate blindness due to trachoma. Targeted treatment of infected households could be more efficient, but the success of such a strategy will depend on the extent of transmission of infection between members of the same household and between members of the community. In this work, we estimated the magnitude of household and community transmission in four populations, two from The Gambia and two from Tanzania. We found that, in general, transmission of the bacteria within households is very efficient. In three of the four populations, persistent infection within households was predicted by the high level of household transmission (a phenomenon observed in longitudinal studies of trachoma). In all of the studied populations, individuals who live in households with more individuals contribute more to the number of new infections in the community than those who live with fewer individuals. Further studies are required to identify and examine household-targeted approaches to treatment.

Failure of current antibiotic first-line regimens and mortality in hospitalized patients with spontaneous bacterial peritonitis

BACKGROUND

Increases in Gram-positive infections and infections with Enterobacteriaceae with antimicrobial resistance have been reported in patients with spontaneous bacterial peritonitis (SBP). This study was performed to investigate the rate of treatment failures of recommended empirical therapies and the impact on mortality.

PATIENTS AND METHODS

A prospectively collected database comprising 101 patients with SBP (70 nosocomial, 31 community acquired) treated at a university hospital between 2002 and 2006 in Munich, Germany, was analyzed.

RESULTS

17 patients initially received a broader than recommended antibiotic regimen. Most of these were treated in the intensive care unit because of severe sepsis/septic shock. Hospital mortality in this group was 82%. A modification of therapy was necessary in 24 of the 84 patients receiving one of the published first-line therapies (cefotaxime, ampicillin/clavulanate, or ciprofloxacin). Mortality was significantly higher in these patients than in those with no change in treatment (66.7% vs 30%, p = 0.002). In 29 patients with positive cultures, mortality was also higher in those with an ineffective first-line treatment (90% vs 45%, p = 0.032). In the multivariable analysis, a modification of antibiotic treatment was an independent risk factor for mortality (odds ratio 5.876, 95% confidence interval 1.826-18.910, p = 0.003). In 41 culture-positive cases, the most commonly cultured pathogens were Escherichia coli (n = 17) and Enterococcus faecium (n = 10). Of the encountered bacterial microorganisms, 14 (33.3%) were resistant to cefotaxime, 17 (38.6%) were resistant to amoxicillin/clavulanate, and 19 (45.2%) were resistant to ciprofloxacin. 29 (64.4%) of the isolates were resistant to one of the recommended firstline antibiotic regimens, and 11 (24.4%) of the isolates were resistant to all three.

CONCLUSION

Recommended empirical antibiotic regimens fail to achieve the desired effect in a substantial number of hospitalized patients with SBP. This has a negative impact on mortality.

[Prevalence and bacterial susceptibility of community acquired urinary tract infection in University Hospital of Brasília, 2001 to 2005]

Urinary tract infection is among the most common infectious diseases in clinical medicine, and knowledge of its epidemiology and the sensitivity profile of the etiological agents is mandatory. The aim of this study was to identify the most frequent etiological agents and the profile of sensitivity to antimicrobial agents of the bacteria isolated from urine cultures from outpatients at the University Hospital of Brasília between 2001 and 2005. From analyses at the hospitals microbiology laboratory, there were 2,433 positive urine cultures. Escherichia coli was the most commonly isolated bacteria (62.4%), followed by Klebsiella pneumoniae (6.8%) and Proteus mirabilis (4.7%). Escherichia coli showed the highest sensitivity to amikacin (98.6%), gentamicin (96.2%), nitrofurantoin (96.3%) and the quinolones ciprofloxacin (90.9%) and norfloxacin (89.8%), with low sensitivity to sulfamethoxazole-trimethoprim (50.6%). The others bacteria presented similar sensitivity profiles. In conclusion, Escherichia coli was the most commonly isolated bacteria, and it was highly sensitive to aminoglycosides, nitrofurantoin and quinolones.

Clinical features and outcome of community-onset bloodstream infections caused by extended-spectrum beta-lactamase-producing Escherichia coli

This study was conducted to evaluate the epidemiology and clinical features of bloodstream infections caused by extended-spectrum beta-lactamase-producing E. coli (ESBL-EC) in community-onset bacteremia. Of 929 episodes of community-onset E. coli bacteremia, 4.1% (38/929) had bacteremia with ESBL producers. Of these, 63.2% (24/38) were further classified as healthcare-associated infections. Although most patients had risk factors for infection due to ESBL producers, three patients with urinary tract infection, four patients with cholangitis, and one patient with a liver abscess had no identified predisposing risk factors. The 30-day mortality was 21.1% (8/38). ESBL-EC is a significant cause of bloodstream infection, even in patients with community-onset infection.

Prior antibiotics and risk of antibiotic-resistant community-acquired urinary tract infection: a case–control study

BACKGROUND

To assess the effect of previous antibiotic use on the risk of a resistant Escherichia coli urinary tract infection (UTI), we undertook a case-control study with prospective measurement of outcomes in 10 general practices in the UK.

METHODS

Urinary samples from all patients with symptoms suggestive of UTIs were sought, and those with a laboratory-proven E. coli infection were interviewed and their medical records examined. Case patients were those with ampicillin- or trimethoprim-resistant infections and control patients had infections that were susceptible to antibiotics, including ampicillin and trimethoprim.

RESULTS

Risk of ampicillin-resistant E. coli infection in 903 patients was associated with amoxicillin prescriptions of >or=7 days duration in the previous 1 month [odds ratio (OR)=3.91, 95% CI 1.64-9.34] and previous 2-3 months (2.29, 1.12-4.70) before illness onset. For prescriptions <7 days duration, there was no statistically significant association. Higher doses of amoxicillin were associated with lower risk of ampicillin resistance. For trimethoprim-resistant E. coli infections, the OR was 8.44 (3.12-22.86) for prescriptions of trimethoprim of >or=7 days in the previous month and 13.91 (3.32-58.31) for the previous 2-3 months. For trimethoprim prescriptions of <7 days, the OR was 4.03 (1.69-9.59) for the previous month but prescribing in earlier periods was not significantly associated with resistance.

CONCLUSIONS

Within the community setting, exposure to antibiotics is a strong risk factor for a resistant E. coli UTI. High-dose, shorter-duration antibiotic regimens may reduce the pressure on the emergence of antibiotic resistance.

How to fight antimicrobial resistance

Antimicrobial misuse results in the development of resistance and superbugs. Over recent decades, resistance has been increasing despite continuing efforts to control it, resulting in increased mortality and cost. Many authorities have proposed local, regional and national guidelines to fight against this phenomenon, and the usefulness of these programmes has been evaluated. Multifaceted intervention seems to be the most efficient method to control antimicrobial resistance. Monitoring of bacterial resistance and antibiotic use is essential, and the methodology has now been homogenized. The implementation of guidelines and infection control measures does not control antimicrobial resistance and needs to be reinforced by associated measures. Educational programmes and rotation policies have not been evaluated sufficiently in the literature. Combination antimicrobial therapy is inefficient in controlling antimicrobial resistance.

Emerging bacterial pathogens: a consensus of the scientific data and the risk for development of multiple organ dysfunction syndrome

Antibiotic resistance in the hospital setting is continuing to increase, particularly in intensive care units (ICUs) and other areas of the hospital such as oncology units, where the use of empiric broad-spectrum antibiotics is common. The problem of antibiotic resistance is also compounded in the immunocompromised patient. Multi-drug resistance is common among both Gram-positive and -negative bacteria, and becoming more prevalent among fungi (yeast). Two major antibiotic-resistant pathogens include extended-spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-KP) and vancomycin-resistant enterococci (VRE). When infections occur with ESBL-KP, a carbapenem antibiotic is usually the drug of choice. When infection occurs with VRE, specific therapy is bacteriostatic, and the clinician may have to rely on empirically selected antibiotics or combinations of antibiotics to achieve a positive outcome. Two newly-approved agents, linezolid and quinupristin/dalfopristin can be used to treat infections caused by resistant gram-positive cocci, but the latter is approved for use against VR-E. faecium. Risk factors for the development of ESBL-KP include the use of extended-spectrum cephalosporins such as ceftazidime. Risk factors for the development of VRE include inappropriate use of vancomycin, extended-spectrum cephalosporins, and antianaerobic drug therapy such as clindamycin. Several institutions have documented a reduction in one or both of these resistant pathogens following a decrease in the use of extended-spectrum cephalosporins combined with the increased use of extended-spectrum penicillins/beta-lactamase inhibitor combinations, such as piperacillin/tazobactam, for the empiric therapy of infections. For VRE, a reduction in the inappropriate use of vancomycin is also an important interventional strategy along with improved infection control practice.

Use of antibiotics and risk of breast cancer: a population-based case-control study

We examined the use of antibiotics among 2728 women with a first diagnosis of breast cancer during 1994–2003, and 27 280 population controls in North Jutland County, Denmark, based on hospital discharge diagnoses, prescription use from 1989 to 2002, and population registry data. We found no increased relative risk of breast cancer associated with use compared with nonuse. The odds ratio for breast cancer associated with more than 10 prescriptions for antibiotics was 1.00 (95% CI 0.86 –1.15). Relative risks were similar for different classes of antibiotics. A subanalysis based on cases and controls younger than 70 years of age, with data on first birth and number of children, showed similar risk estimates even after adjustment for age at first birth and parity. In our study, use of antibiotics was not associated with an increased risk of breast cancer.

Impact of azithromycin administration for trachoma control on the carriage of antibiotic-resistant Streptococcus pneumoniae

Community distribution of azithromycin has an important role to play in trachoma control. Previous studies have suggested that this may increase the prevalence of macrolide-resistant Streptococcus pneumoniae. S. pneumoniae was isolated from children under 7 years of age in Rombo District, northern Tanzania, before and 2 and 6 months after community-wide administration of azithromycin. Overall carriage rates were 11, 12, and 7%, respectively. Only one macrolide-resistant isolate carrying the mef gene was obtained 6 months after azithromycin administration. This contrasted with cotrimoxazole and penicillin resistance, both of which were common (cotrimoxazole resistance, 42, 43, and 47%, and penicillin resistance, 21, 17, and 16% at baseline, 2 months, and 6 months, respectively). There was a significant association between cotrimoxazole and penicillin resistance (P < 0.0001, Fisher's exact). These data suggest that in communities where macrolide resistance is rare, azithromycin distribution for trachoma control is unlikely to increase the prevalence of resistant organisms.

Source of infection and other factors associated with case fatality in community-acquired bacteremia—a Danish population-based cohort study from 1992 to 1997

OBJECTIVE

To examine the association between the source of infection, other factors and the 30-day case-fatality rate (CFR) in patients with community-acquired bacteremia.

METHODS

We included in the study 1844 patients older than 15 years (median age 72 years) with a first episode of community-acquired bacteremia in the period 1992-97 from a population-based bacteremia database. Information on co-morbidity, antibiotic prescriptions and date of death was obtained from health registries through linkage with the patient's personal identification number. The outcome measure was the overall CFR.

RESULTS

The mean CFR was 18% (20% in 1992-95, 15% in 1996-97). The commonest sources of infection were the urinary tract (29%) and the respiratory tract (20%); patients with an undetermined source accounted for 21% in 1992-95 and 13% in 1996-97. The most frequent bacteria were Escherichia coli (33%) and Streptococcus pneumoniae (22%). Thirty-two per cent of patients did not receive appropriate empirical antibiotic therapy. The following factors were associated with CFR: source of infection other than the urinary tract, first four years of the study, age >/=75 years, and presence of co-morbidity. An undetermined source showed the strongest association with CFR during the period 1996-97.

CONCLUSIONS

As an undetermined source of infection was strongly associated with CFR, physicians should be aware of the significance of identifying and eliminating a source of infection, and more efforts should be directed at timely and appropriate empirical antibiotic therapy.

[Bacteremia due to Escherichia coli: epidemiological analysis and sensitivity to antibiotics in a county hospital]

BACKGROUND AND OBJECTIVE

There are few studies analyzing the epidemiological characteristics of Escherichia coli bacteremia including the susceptibility to antibiotics and outcome.

PATIENTS AND METHOD

E. coli bacteremia episodes were recorded from January 1989 to December 1998. Clinical variables, setting acquisition, source of bacteremia, outcome and susceptibility to antibiotics were included. The study was prospective and comparative. Descriptive and univariate analysis were performed.

RESULTS

330 episodes of E. coli bacteremia were recorded: 117 in women. The most frequent source was the urinary tract (68%), followed by an abdominal and biliary focus. E. coli bacteremia appeared mostly in groups II and III of McCabe & Jackson. In 46 cases (14%), E. coli bacteremia was nosocomial. Crude and related mortality was 6.6 and 4.2%, respectively. A significant increase in the resistance to ciprofloxacin was observed.

CONCLUSIONS

The epidemiological characteristics of E. coli bacteremia have not changed, yet the mortality was lower in our series. Preventive measures in the hospital and a rational use of antibiotics, principally quinolones, are necessary.

Impact of trimethoprim-sulfamethoxazole prophylaxis on etiology and susceptibilities of pathogens causing human immunodeficiency virus-associated bacteremia

The impact of chronic prophylactic administration of trimethoprim-sulfamethoxazole (SXT) on the ecology and the antimicrobial susceptibilities of bloodstream pathogens in human immunodeficiency virus (HIV)-infected patients was studied using a retrospective chart review. Eighty-nine patients with advanced HIV infection developed 124 episodes of bacteremia with 156 pathogenic isolates. Staphylococcus aureus and Enterobacteriaceae tended to be less common among patients receiving SXT. Isolates from patients receiving SXT were likelier (75%) to be resistant to 20 microg of SXT/ml than those from patients not receiving SXT (33%) (P < 0.001).

Association between antibiotic resistance and community prescribing: a critical review of bias and confounding in published studies

The reported association between antibiotic prescribing and resistance may be subject to bias or confounding. Bias describes any effect at any stage of investigation or inference tending to produce results that depart systematically from the true value. A confounding variable is one that is associated independently with both exposure and outcome. Confounding variables may create an apparent association or mask a real association. Pharmacoepidemiology is the study of the use and the effects of drugs in large numbers of people. We have used standard pharmacoepidemiological methods to investigate sources of bias and confounding in the association between prescribing and resistance. We conclude that the association is statistically valid and that the consistency of evidence supports a cause-effect relationship. Nonetheless, several important sources of bias and confounding must be taken into account in future studies that analyze the impact of prescribing policies on resistance.

Bacteraemia caused by hospital-type micro-organisms during hospital stay

A sharp transition between community-type and hospital-type pathogens at the second or third day of hospital stay is often assumed. This study aimed to test whether such a threshold phenomenon exists for bloodstream infections and to examine the relationship between the proportion of infections caused by hospital-type pathogens and length of stay in the hospital. Blood stream infections were studied in a referral and a university hospital in west Denmark, and a university hospital in central Israel during three study periods (1994-1996, 1992-1995, 1989-1995 in the three hospitals respectively). No threshold effect at 2-3 days stay in the hospital could be demonstrated. However the percentage of Pseudomonas aeruginosa bloodstream infections increased constantly in the three hospitals from 1%, 1% and 7% during the first 2 days to 7%, 4%, and 14% during the third week of hospital stay (P<0.01 for all three comparisons-chi(2)for linear trends). For Candida sp. the increase was from 0%, 2%, 1% during the first 2 days to 3%, 4%, and 9% during the third week, P<0.05. Methicillin-resistant Staphylococcus aureus in Israel increased from 26% of the total number of S. aureus during the first 2 days to 69% during the third week, P<0.0001. For penicillin-resistant S. aureus in Denmark, the percentages were 84% and 100%, P<0.05.The percentage of infections caused by hospital-type pathogens increased almost linearly during the first 3 weeks of hospital stay, with no threshold effect. This trend should be taken into account when prescribing empirical therapy for nosocomial infections.