Detection of critical antibiotic resistance genes through routine microbiome surveillance

Population-based public health data on antibiotic resistance gene carriage is poorly surveyed. Research of the human microbiome as an antibiotic resistance reservoir has primarily focused on gut associated microbial communities, but data have shown more widespread microbial colonization across organs than originally believed, with organs previously considered as sterile being colonized. Our study demonstrates the utility of postmortem microbiome sampling during routine autopsy as a method to survey antibiotic resistance carriage in a general population. Postmortem microbial sampling detected pathogens of public health concern including genes for multidrug efflux pumps, carbapenem, methicillin, vancomycin, and polymixin resistances. Results suggest that postmortem assessments of host-associated microbial communities are useful in acquiring community specific data while reducing selective-participant biases.

The challenge of converting Gram-positive-only compounds into broad-spectrum antibiotics

Multidrug resistant Gram-negative bacterial infections are on the rise, and there is a lack of new classes of drugs to treat these pathogens. This drug shortage is largely due to the challenge of finding antibiotics that can permeate and persist inside Gram-negative species. Efforts to understand the molecular properties that enable certain compounds to accumulate in Gram-negative bacteria based on retrospective studies of known antibiotics have not been generally actionable in the development of new antibiotics. A recent assessment of the ability of >180 diverse small molecules to accumulate in Escherichia coli led to predictive guidelines for compound accumulation in E. coli. These "eNTRy rules" state that compounds are most likely to accumulate if they contain a nonsterically encumbered ionizable Nitrogen (primary amines are the best), have low Three-dimensionality (globularity ≤ 0.25), and are relatively Rigid (rotatable bonds ≤ 5). In this review, we look back through 50+ years of antibacterial research and 1000s of derivatives and assess this historical data set through the lens of these predictive guidelines. The results are consistent with the eNTRy rules, suggesting that the eNTRy rules may provide an actionable and general roadmap for the conversion of Gram-positive-only compounds into broad-spectrum antibiotics.

Comparison of Vancomycin and Cefuroxime for Infection Prophylaxis in Coronary Artery Bypass Surgery

OBJECTIVE: To investigate clinically significant differences between vancomycin and cefuroxime for perioperative infection prophylaxis in coronary artery bypass surgery.

DESIGN: A total of 884 patients were randomized prospectively to receive either cefuroxime (444) or van-comycin (440) and were assessed for infectious complications during hospitalization and 1 month postoperatively.

SETTING: A university hospital.

RESULTS: The overall immediate surgical-site infection rate was 3.2% in the cefuroxime group and 3.5% in the vancomycin group (difference, −0.3; 95% confidence interval, −2.6-2.1).

CONCLUSIONS: The data suggest that vancomycin has no clinically significant advantages over cephalosporin in terms of antimicrobial prophylaxis. We suggest that cefuroxime (or first-generation cephalosporins, which were not studied here) is a good choice for infection prophylaxis in connection with coronary artery bypass surgery in institutions without methicillin-resistantStaphylococcus aureusproblems. In addition to the increasing vancomycin-resistant enterococci problem, the easier administration and usually lower price of cefuroxime make it preferable to vancomycin.

Late-onset infection and the role of antibiotic prescribing policies

PURPOSE OF REVIEW

Late-onset infection is a significant cause of morbidity and mortality in low-birth-weight and premature infants. Empirical antibiotic treatment is used as infants can deteriorate rapidly without treatment. Current data on the epidemiology of late-onset infection, the types of antibiotics used, duration of antibiotic use, and antibiotic prescribing policies are reviewed.

RECENT FINDINGS

Epidemiological data on late-onset sepsis is dominated by information concerning developed countries; large prospective data collections have been set up in many such countries. Recent data indicate that late-onset sepsis occurs in one-fifth of very-low-birth-weight infants. There are increasing concerns regarding antibiotic resistance. Antibiotic regimens that do not include third-generation cephalosporins produce less resistance. Strategies of antibiotic rotation have not been documented as producing a marked effect on the development of resistant micro-organisms, but there is a lack of randomized trials. Recommendations for preventing the spread of vancomycin-resistant enterococci, produced by the Hospital Infection Control Practices Advisory Committee, have been shown to be effective in a number of situations. Recent reports have documented the success of multidisciplinary, systems-orientated approaches for reducing neonatal nosocomial infection.

SUMMARY

Antibiotic prescribing policies have an important role to play in the treatment of late-onset neonatal infection. There is enough evidence to state that narrow-spectrum antibiotics should be used wherever possible and that potent broad-spectrum antibiotics should be kept in reserve. Ongoing prospective surveillance of infection rates, micro-organisms, resistance and antibiotic use is essential.

Vancomycin-resistant enterococci: a road map on how to prevent the emergence and transmission of antimicrobial resistance

Nosocomial acquisition of microorganisms resistant to multiple antibiotics represents a threat to patient safety. Here we review the mechanisms that have allowed highly resistant strains belonging to the Enterococcus genus to proliferate within our health-care institutions. These mechanisms indicate that decreasing the prevalence of resistant organisms requires active surveillance, adherence to vigorous isolation, hand hygiene and environmental decontamination measures, and effective antibiotic stewardship. We suggest how to tailor such a complex, multidisciplinary program to the needs of a particular health-care setting so as to maximize cost-effectiveness.

Effect of gastrointestinal bleeding and oral medications on acquisition of vancomycin-resistant Enterococcus faecium in hospitalized patients

There has been minimal investigation of medications that affect gastrointestinal function as potential risk factors for the acquisition of vancomycin-resistant enterococci (VRE). We performed a retrospective case-control study, with control subjects matched to case patients by time and location of hospitalization. Strict exclusion criteria were applied to ensure that only case patients with a known time of acquisition of VRE were included. Control patients were patients with > or =1 culture negative for VRE. The risk factors identified were use of vancomycin (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.7-6.0; P=.0003), presence of central venous lines (OR, 2.2; 95% CI, 1.04-4.6; P=.04), and use of antacids (OR, 2.9; 95% CI, 1.5-5.6; P=.002). Two protective factors included gastrointestinal bleeding (OR, 0.26; 95% CI, 0.08-0.79; P=.02) and use of Vicodin (Knoll Labs; hydrocodone and acetaminophen; OR, 0.93; 95% CI, 0.90-0.97; P=.0003). Changes in gastrointestinal function, whether due to bleeding or to the effects of oral medications, may affect whether patients become colonized with VRE.

Home hygiene practices and infectious disease symptoms among household members

Public health programs are generally targeted to communitywide, population-based prevention strategies, with little attention focused on the home environment as one potential source of transmission of infectious diseases. The purpose of this correlational prevalence survey was to describe the relationship between home hygiene practices and prevalence of infectious disease symptoms among household members. Three hundred and ninety-eight households with 1,662 members in an inner-city population (96.4% Hispanic) were surveyed to examine hygiene practices and determine the presence of transmission of infection, defined as the presence of the same symptom(s) in two or more household members for which at least one individual sought medical attention and received treatment. At least one individual in 78.6% of households reported symptoms of infection in the previous 30 days, and 37.9% of households met the definition of disease transmission. In univariate analyses, five factors were significantly associated with risk of household transmission, but in the logistic regression model, only use of communal laundry (p = 0.009) and lack of bleach use (p = 0.04) were significantly predictive of increased risk of transmission. This is the first comprehensive survey of home hygiene practices and the first study to identify a potential link between laundry and risk of disease transmission in homes. This potential link warrants further study in clinical trials.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Efficacy of hand disinfectants against vancomycin-resistant enterococci in vitro

Vancomycin-resistant enterococci (VRE) may be spread within a hospital via the contaminated hands of the healthcare worker. Effective hand disinfectants are necessary to break chains of transmission. We determined the bactericidal activity of 1-propanol, chlorhexidine digluconate (0.5 and 4%). Sterillium (45% 2-propanol, 30% 1-propanol and 0.2% mecetronium etilsulphate), Skinsept F (70% 2-propanol, 0.5% chlorhexidine digluconate and 0.45% hydrogen peroxide) and Hibisol (70% 2-propanol and 0.5% chlorhexidine gluconate) against 11 clonally distinct enterococcal isolates in a quantitative suspension test. Four isolates were vancomycin susceptible, four were vanA and the remainder vanB positive. Eight isolates were identified as Enterococcus faecium, two as Enterococcus faecalis and one as Enterococcus gallinarum. The investigator was blinded to the species and the genotype. Four parallel experiments were carried out for each isolate, each preparation, each dilution and each reaction time. 1-Propanol (60%), Sterillium, Skinsept F and Hibisol were all highly bactericidal after 15 and 30 s against VRE and vancomycin-susceptible enterococci (VSE) with reduction factors (RF) > 6.4, even in dilution of 50% (v/v). No significant difference was observed between vanA isolates, vanB isolates and VSE. Chlorhexidine digluconate (0.5% and 4%) was found to be less bactericidal after 30, 60 and 300 sec (RF < or = 2.5). The vanB genotype isolates were found to be significantly more susceptible to chlorhexidine (0.5%) than the vanA isolates (60 sec; one-way ANOVA model; P = 0.05). After 300 sec the vanB genotype isolates were found to be significantly more susceptible to chlorhexidine (0.5%) than the other two genotype isolates (P = 0.016). The vanA isolates were found to be significantly more susceptible to chlorhexidine (4%) than the vanB isolates (300 s; P = 0.024). E. faecium was found to be less susceptible to chlorhexidine than E. faecalis at all concentrations and reaction times, but significant differences between RF were only observed at 60 sec for both chlorhexidine concentrations (P < 0.05; t-test for independent samples). Propanol is much more effective against enterococci than chlorhexidine and combination of the two may be useful in providing an immediate and long lasting effect.

Control of transmission of vancomycin-resistant Enterococcus faecium in a long-term-care facility

OBJECTIVES

To describe the investigation and control of transmission of vancomycin-resistant enterococci (VRE) in a residential long-term-care (LTC) setting. OUTBREAK INVESTIGATION: A strain of vancomycin-resistant Enterococcus faecium not previously isolated in Ontario colonized five residents of a 254-bed LTC facility in Toronto. The index case was identified when VRE was isolated from a urine culture taken after admission to a local hospital. Screening of rectal swabs from all 235 residents identified four others who were colonized with the same strain of E faecium.

CONTROL MEASURES

Colonized residents were cohorted. VRE precautions were established as follows: gown and gloves for resident contact, restriction of contact between colonized and noncolonized residents, no sharing of personal equipment, and daily double-cleaning of residents' rooms and wheelchairs.

OUTCOME

Two colonized residents died of causes unrelated to VRE. Although bacitracin therapy (75,000 units four times a day x 14 days) failed to eradicate carriage in two of three surviving residents, both cleared their carriage within 7 weeks. Repeat rectal swabs from 224 residents (91%) 2 months after isolation precautions were discontinued and from 125 residents (51%) 9 months later identified no new cases. Total cost of investigation and control was $12,061 (Canadian).

CONCLUSION

VRE may be transmitted in LTC facilities, and colonized LTC residents could become important VRE reservoirs. Control of VRE transmission in LTC facilities can be achieved even with limited resources.

Transmission of vancomycin-resistant enterococcus among family members: a case study

Enterococci are persistent organisms naturally occurring in the digestive tract, able to persist on environmental surfaces for days or weeks, surviving heat and desiccation. They are the second most common bacterial cause of nosocomial infection. Recent strains of enterococci resistant to vancomycin pose a serious health hazard to hospitalized, institutionalized, and immunocompromised patients. This article presents a case study of community-acquired vancomycin-resistant enterococcus in an otherwise healthy child and suggests strategies for management and containment in the community.

Clinical and epidemiological significance of enterococci intrinsically resistant to vancomycin (possessing the vanC genotype)

Constitutive low-level vancomycin resistance is found intrinsically in certain enterococcal species and is encoded by vanC ligase genes. These intrinsically vancomycin-resistant enterococci (VRE) will be referred to as VANC VRE. A prospective study to determine the clinical and epidemiologic significance of VANC VRE was conducted. VANC VRE were recovered from the stools of 34 of 601 (5.7%) patients, a rate similar to that obtained for the stools of 100 outpatients in the community (5%). VANC VRE were also isolated from the nonstool specimens of 9 of 538 patients (1.7%), including two patients with bacteremia. No VRE of the vanA or vanB genotypes were detected in nonstool specimens. Eighty-two hospital contacts of the first 23 patients found to be colonized or infected with VANC VRE were screened, and 6 contacts were found to be gastrointestinal carriers of VANC VRE. However, typing of isolates from these 6 contacts by pulsed-field gel electrophoresis with SmaI showed the isolates to be unique and different from those recovered from the index patients. In fact, all VANC VRE isolates from different patients in this study were unique. A case-control study with patients who were negative when screened for VANC VRE as controls failed to identify any risk factor associated with colonization or infection with this organism. VANC VRE were infrequently recovered from clinical specimens but were occasionally found as part of the normal stool flora. Since no transmission between patients was documented, additional isolation procedures may not be necessary for patients colonized or infected with VANC VRE.

Pseudo-outbreak of Enterococcus durans infections and colonization associated with introduction of an automated identification system software update

Enterococci are an important cause of hospital-acquired infections. Since 1989, there has been an increase in the number of nosocomial enterococcal infections caused by strains resistant to vancomycin in the United States. Although many enterococcal species can colonize humans, only Enterococcus faecalis, E. faecium, E. raffinosus, and E. casseliflavus have been implicated in clusters of infection. In January 1996, the Centers for Disease Control and Prevention received a report of an outbreak of vancomycin-resistant enterococci in which 31 of 84 (36.9%) isolates were identified as E. durans. Twenty-nine isolates identified as E. durans were identified to the species level after the introduction of an automated identification system software update (Vitek gram-positive identification card, version R09.1) for the identification of species of gram-positive organisms. When seven isolates initially reported as E. durans were identified to the species level by alternate methods, they were found to be E. faecium. Subsequently, isolates identified as E. durans by the automated system were reidentified by using a rapid streptococcus test, and no further enterococcal isolate has been confirmed as E. durans. Automated microbial analysis is a potential source of error that is not easily recognized. When laboratory findings are discordant with expected clinical or epidemiologic patterns, confirmatory testing by alternate methods should be performed.