Direct ertapenem disk screening method for identification of KPC-producing Klebsiella pneumoniae and Escherichia coli in surveillance swab specimens

High frequency of carbapenem-resistant Enterobacteriaceae fecal carriage among ICU hospitalized patients from Southern Iran

Objectives

The worldwide emergence of carbapenem-resistant Enterobacteriaceae (CRE) has become a major therapeutic concern to medical institutions. To date, no study has determined the frequency and risk factors of inpatients with CRE fecal carriage in Southern Iran. We studied the features of carbapenemase-producing Enterobacteriaceae (CPE) collected from the central ICU of a university hospital.

Materials and Methods

Totally, 173 samples, including 124 stool samples from 46 ICU inpatients on admission and different follow-ups, 9 ICU staff, and 40 environmental samples were included. CRE was identified using microbiological methods. Antimicrobial susceptibility was investigated by using the disk diffusion method and E-test. Carbapenemase producers were detected using the mCIM method. Seven carbapenemase genes were characterized. The genetic relationship among 20 CPE was elucidated by PFGE.

Results

The overall fecal carriage rate was 28.2%, while CRE acquisition was 6.1%. CRE were classified as Klebsiella pneumoniae (71.4%), Escherichia coli (23.8%), and Enterobacter aerogenes (4.8%). From 21 CRE, 20 (95.2%) produced carbapenemases, of which 10, 15, 10, 25, 5, and 65% were blaKPC, blaSME, blaIMP, blaVIM, blaNDM and blaOXA-48-positive, respectively. Out of 20 CPE, 14 different PFGE patterns were observed, categorized into six clusters, suggestive of non-clonal spread. No difference between the examined risk factors with CRE carriage was shown.

Conclusion

The data indicate a high CRE fecal carriage rate among inpatients. Our findings implicate the widespread of OXA-48 carbapenemase together with heterogeneity among CRE with great concern for dissemination and therapeutic threat. Early diagnosis and monitoring of CRE among inpatients are urgent.

Clinical Epidemiology, Risk Factors, and Control Strategies of Klebsiella pneumoniae Infection

Klebsiella species cause infections at multiple sites, including lung, urinary tract, bloodstream, wound or surgical site, and brain. These infections are more likely to occur in people with preexisting health conditions. Klebsiella pneumoniae (K. pneumoniae) has emerged as a major pathogen of international concern due to the increasing incidences of hypervirulent and carbapenem-resistant strains. It is imperative to understand risk factors, prevention strategies, and therapeutic avenues to treat multidrug-resistant Klebsiella infections. Here, we highlight the epidemiology, risk factors, and control strategies against K. pneumoniae infections to highlight the grave risk posed by this pathogen and currently available options to treat Klebsiella-associated diseases.

Rapid identification from rectal swabs of the clinically most relevant carbapenemase genes from gram-negative bacteria using the BD MAX Check-Points CPO Assay

We conducted an international multicentre evaluation to assess the clinical performance characteristics of the new multiplex PCR-based BD MAX Check-Points CPO assay to detect the 5 major carbapenemase families: KPC, VIM/IMP (tested simultaneously), NDM and OXA-48 compared to a reference method consisting of 2 culture methods (to improve recovery of CPO isolates from the rectal swabs), followed by carbapenem susceptibility testing and sequencing of target carbapenemase genes. Tests were performed from rectal swab specimens in ESwab collection and transport devices. Positive percent agreement (PPA) for BD MAX Check-Points CPO for KPC and OXA-48 were 88.2% (95% CI:72.6-96.7) and 96.2% (95% CI:80.4-99.9), respectively. Negative percent agreement was ≥99% for each gene. Insufficient samples (≤10) were positive for VIM/IMP or NDM tests to calculate meaningful PPA values. The BD MAX Check-Points CPO assay represents an accurate tool for rapid recognition of patients with rectal colonization by the most commonly encountered CPOs.

Cohorting KPC+ Klebsiella pneumoniae (KPC-Kp)-positive patients: A genomic exposé of cross-colonization hazards in a long-term acute-care hospital (LTACH)

OBJECTIVE

Cohorting patients who are colonized or infected with multidrug-resistant organisms (MDROs) protects uncolonized patients from acquiring MDROs in healthcare settings. The potential for cross transmission within the cohort and the possibility of colonized patients acquiring secondary isolates with additional antibiotic resistance traits is often neglected. We searched for evidence of cross transmission of KPC+ Klebsiella pneumoniae (KPC-Kp) colonization among cohorted patients in a long-term acute-care hospital (LTACH), and we evaluated the impact of secondary acquisitions on resistance potential.

DESIGN

Genomic epidemiological investigation.

SETTING

A high-prevalence LTACH during a bundled intervention that included cohorting KPC-Kp-positive patients.

METHODS

Whole-genome sequencing (WGS) and location data were analyzed to identify potential cases of cross transmission between cohorted patients.

RESULTS

Secondary KPC-Kp isolates from 19 of 28 admission-positive patients were more closely related to another patient's isolate than to their own admission isolate. Of these 19 cases, 14 showed strong genomic evidence for cross transmission (<10 single nucleotide variants or SNVs), and most of these patients occupied shared cohort floors (12 patients) or rooms (4 patients) at the same time. Of the 14 patients with strong genomic evidence of acquisition, 12 acquired antibiotic resistance genes not found in their primary isolates.

CONCLUSIONS

Acquisition of secondary KPC-Kp isolates carrying distinct antibiotic resistance genes was detected in nearly half of cohorted patients. These results highlight the importance of healthcare provider adherence to infection prevention protocols within cohort locations, and they indicate the need for future studies to assess whether multiple-strain acquisition increases risk of adverse patient outcomes.

Evaluation of the Direct MacConkey Method for Identification of Carbapenem-Resistant Gram-Negative Organisms from Rectal Swabs: Reevaluating Zone Diameter Cutoffs

The optimal method to screen for gastrointestinal colonization with carbapenem-resistant organisms (CRO) has yet to be established. The direct MacConkey (direct MAC) plate method demonstrates high sensitivity for CRO detection, but established zone diameter (ZD) criteria for ertapenem (≤27 mm) and meropenem (≤32 mm) result in high rates of false positives upon confirmatory testing. To increase specificity, we screened for CRO in two high-risk wards using the direct MAC plate method, recorded ZDs for each sample, and generated receiver operating characteristic (ROC) curves to evaluate the optimal ZD cutoff criteria. Of 6,868 swabs obtained over an 18-month period, 4,766 (69%) had growth on MAC plates, and 2,500 (36%) met criteria for further evaluation based on previously established ZDs around the carbapenem disks. A total of 812 (12%) swabs were confirmed positive for at least one CRO and included 213 (3%) carbapenemase-producing organisms (CPO), resulting in a specificity of 78% for the direct MAC plate method. Reducing the ertapenem and meropenem ZDs to ≤25 mm improved specificity to 83%, decreasing the confirmatory testing workload by 32%. The sensitivities with the lower ZD criteria were 89% for CRO and 94% for CPO, respectively. The direct MAC plate method criteria for CRO testing can be modified to balance the sensitivity and specificity of CRO while reducing the burden on clinical microbiology laboratories. These modifications can be particularly helpful in regions with a low CRO prevalence.

CTX-M ESBL-producing Enterobacteriaceae: estimated prevalence in adults in England in 2014

Background

ESBL-producing Enterobacteriaceae (ESBLPE) are increasing in prevalence worldwide and are more difficult to treat than non-ESBLPE. Their prevalence in the UK general population is unknown, as the only previous UK ESBLPE faecal colonization study involved patients with diarrhoea.

Objectives

To estimate the prevalence of CTX-M ESBLPE faecal colonization in the general adult population of England in 2014, and investigate risk factors.

Methods

A stratified random sample of 58 337 registered patients from 16 general practices within four areas of England were invited to participate by returning faeces specimens and self-completed questionnaires. Specimens were tested for ESBLPE and carbapenemase-producing Enterobacteriaceae (CPE).

Results

2430 individuals participated (4% of those invited). The estimated prevalence of colonization with CTX-M ESBLPE in England was 7.3% (95% CI 5.6%–9.4%) (Shropshire 774 participants, 4.9% colonization; Southampton City 740 participants, 9.2%; Newham 612 participants, 12.7%; Heart of Birmingham 234 individuals, 16.0%) and was particularly high in: those born in Afghanistan (10 participants, 60.0% colonization, 95% CI 29.7%–84.2%); those born on the Indian subcontinent (India, Pakistan, Bangladesh or Sri Lanka) (259 participants, 25.0% colonization, 95% CI 18.5%–32.9%); travellers to South Asia (India, Pakistan, Bangladesh, Sri Lanka or Nepal) in the last year (140 participants, 38.5% colonization, 95% CI 27.8%–50.5%); and healthcare domestics (8 participants, unweighted 37.5% colonization, 95% CI 8.5%–75.5%). Risk factors identified included: being born in the Indian subcontinent (aOR 5.4, 95% CI 3.0–9.7); travel to South Asia (aOR 2.9, 95% CI 1.8–4.8) or to Africa, China, South or Central America, South East or Pacific Asia or Afghanistan (aOR 2.6, 95% CI 1.7–4.1) in the last year; and working as a healthcare domestic (aOR 6.2, 95% CI 1.3–31). None of the 48 participants who took co-amoxiclav in the last year was colonized with CTX-M ESBLPE. bla_CTX-M-15 accounted for 66% of CTX-M ESBLPE positives. 0.1% (two participants) were colonized with CPE.

Conclusions

CTX-M ESBLPE are established in the general population in England and prevalence is particularly high in people from certain countries of birth or with recent travel. We recommend that these findings be taken into account in guidance on the empirical management of patients presenting with a likely Enterobacteriaceae infection.

Carbapenem-resistant Enterobacteriaceae: An emerging bacterial threat

The first reports of carbapenem resistance in Enterobacteriaceae isolates occurred in the early 1990s. Researchers published the first report of an isolate that produced Klebsiella pneumoniae carbapenemase in 2001. Since that time, carbapenemase-producing Enterobacteriaceae isolates have disseminated globally. Microbiology laboratories are integral to the control of carbapenem-resistant Enterobacteriaceae (CRE). Laboratories need to be able to identify CRE, identify possible therapeutic alternatives, and sometimes identify the type of mechanism responsible for the carbapenem-resistant phenotype. Knowledge of these tasks is essential for all clinical microbiology laboratorians.

Utility of CHROMagar mSuperCARBA for surveillance cultures of carbapenemase-producing Enterobacteriaceae

Culture of carbapenemase-producing Enterobacteriaceae (CPE) as part of active surveillance is one of the most useful strategies for successful infection control programmes. Our objective was to compare the recently introduced CHROMagar mSuperCARBA agar for CPE detection in surveillance cultures from perineal swabs with the US Centers for Disease Control and Prevention method. Our results showed that this agar is a useful and affordable alternative (sensitivity 93.05%, specificity 96.21%, diagnostic accuracy 95.2%) to detect CPE in hospital settings.

Active screening and interfacility communication of carbapenem-resistant Enterobacteriaceae (CRE) in a tertiary-care hospital

BACKGROUND

Hospitals may implement admission screening cultures and may review transfer documentation to identify patients colonized with carbapenem-resistant Enterobacteriaceae (CRE) to implement isolation precautions; however, outcomes and logistical considerations have not been well described.

METHODS

At an academic hospital in Chicago, we retrospectively studied the implementation and outcomes of CRE admission screening from 2013 to 2016 during 2 periods. During period 1, we implemented active CRE rectal culture screening for all adults patients admitted to intensive care units (ICUs) and for those transferred from outside facilities to general wards. During period 2, screening was restricted only to adults transferred from outside facilities. For a subset of transferred patients who were previously reported to the health department as CRE positive, we reviewed transfer paperwork for appropriate documentation of CRE.

RESULTS

Overall, 11,757 patients qualified for screening; rectal cultures were performed for 8,569 patients (73%). Rates of CRE screen positivity differed by period, previous facility type (if transferred), and current inpatient location. A higher combined CRE positivity rate was detected in the medical and surgical ICUs among period 2 patients (3.3%) versus all other ward-period comparisons (P<.001). Among 13 transferred patients previously known to be CRE colonized, appropriate CRE transfer documentation was available for only 4 patients (31%).

CONCLUSIONS

Active screening for CRE is feasible, and screening patients transferred from outside facilities to the medical or surgical ICU resulted in the highest screen positivity rate. Furthermore, CRE carriage was inconsistently documented in transfer paperwork, suggesting that admission screening or enhanced inter-facility communication are needed to improve the identification of CRE-colonized patients.

Rapid detection of blaKPC directly from surveillance rectal swabs by EasyQ KPC

The performance of EasyQ KPC assay was evaluated for the first time for bla_KPC detection directly from surveillance rectal swabs without broth enrichment. Using conventional polymerase chain reaction as gold standard method, EasyQ KPC and culture-based molecular tests demonstrated a sensitivity/specificity of 100%/87.3% and 83.3%/98.2%, respectively.

High Prevalence of Multidrug-Resistant Bacteria in Libyan War Casualties Admitted to a Tertiary Care Hospital, Germany

The ongoing Libyan conflict constantly causes victims among the military and civilian population. Cross-border transfer of patients represents a high risk of introducing multidrug-resistant organisms (MDROs), for example, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, and carbapenem-resistant gram-negative organisms (CROs), into the country of destination. This study assessed the MDRO status in Libyan war casualties (n = 67) admitted to Northwest Medical Centre in Frankfurt/Main, Germany, from August 2016 till January 2017. Identified multidrug-resistant nonfermenters and Enterobacteriaceae were subjected to molecular detection of β-lactamases and further mechanisms of resistance. All isolates were typed by enzymatic macrorestriction and subsequent pulsed-field gel electrophoresis. MDROs were found in 40 (60%) patients, including 25 (37%) positive for at least one CRO and 11 (16%) patients with MRSA. A total of 37 isolates of Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Enterobacter cloacae, and Serratia marcescens produced carbapenemases: NDM (n = 17), OXA-48 (n = 15), and OXA-23 (n = 9) in addition to other β-lactamases (with bla_{CTX-M-group-1} being most frequent) and plasmid-mediated quinolone resistance genes (qnrB, aac(6')Ib-cr). Bacterial strain typing revealed the presence of various clones. This high MDRO rate in Libyan war casualties demands awareness, appropriate screening, and containment measures for medical institutions involved in medical care to avoid patient-to-patient transmission.

Screening for carbapenem-resistant Enterobacteriaceae: Who, When, and How?

The global spread of carbapenem-resistant Enterobacteriaceae (CRE) has been fostered by the lack of preemptive screening of patients in healthcare facilities that could prevent patient-to-patient transmission. Outbreaks of CRE infections have led some institutions to implement rigorous screening programs, although controlled comparative data are frequently lacking. Resource limitations and uncertainty regarding the optimal approach has kept many facilities from enacting more active routine surveillance policies that could reduce the prevalence of CRE. The ideal population to target for screening, the frequency of testing, and the preferred test method are components of surveillance programs that remain open to debate. This review discusses the rationale for different screening policies in use and the performance characteristics of laboratory methods available to detect CRE carriage.

Rapid Identification of Five Classes of Carbapenem Resistance Genes Directly from Rectal Swabs by Use of the Xpert Carba-R Assay

Carbapenemase-producing organisms (CPO) have been identified by global health leaders as an urgent threat. Detection of patients with gastrointestinal carriage of CPO is necessary to interrupt their spread within health care facilities. In this multisite study, we assessed the performance of the Xpert Carba-R test, a rapid real-time quantitative PCR (qPCR) assay that detects five families of carbapenemase genes (bla_IMP, bla_KPC, bla_NDM, bla_OXA-48, and bla_VIM) directly from rectal swab specimens. Using dual swabs, specimens from 755 patients were collected and tested prospectively. An additional 432 contrived specimens were prepared by seeding well-characterized carbapenem-susceptible and -nonsusceptible strains into a rectal swab matrix and inoculating them onto swabs prior to testing. Antimicrobial susceptibility testing, broth enriched culture, and DNA sequencing were performed by a central laboratory blind to the Xpert Carba-R results. The Xpert Carba-R assay demonstrated a positive percentage of agreement (PPA) between 60 and 100% for four targets (bla_KPC, bla_NDM, bla_VIM, and bla_OXA-48) and a negative percentage of agreement (NPA) ranging between 98.9 and 99.9% relative to the reference method (culture and sequencing of any carbapenem-nonsusceptible isolate). There were no prospective bla_IMP-positive samples. Contrived specimens demonstrated a PPA between 95 and 100% and an NPA of 100% for all targets. Testing of rectal swabs directly using the Xpert Carba-R assay is effective for rapid detection and identification of CPO from hospitalized patients.

Modifiable Risk Factors for the Spread of Klebsiella pneumoniae Carbapenemase-Producing Enterobacteriaceae Among Long-Term Acute-Care Hospital Patients

OBJECTIVE To identify modifiable risk factors for acquisition of Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae (KPC) colonization among long-term acute-care hospital (LTACH) patients. DESIGN Multicenter, matched case-control study. SETTING Four LTACHs in Chicago, Illinois. PARTICIPANTS Each case patient included in this study had a KPC-negative rectal surveillance culture on admission followed by a KPC-positive surveillance culture later in the hospital stay. Each matched control patient had a KPC-negative rectal surveillance culture on admission and no KPC isolated during the hospital stay. RESULTS From June 2012 to June 2013, 2,575 patients were admitted to 4 LTACHs; 217 of 2,144 KPC-negative patients (10.1%) acquired KPC. In total, 100 of these patients were selected at random and matched to 100 controls by LTACH facility, admission date, and censored length of stay. Acquisitions occurred a median of 16.5 days after admission. On multivariate analysis, we found that exposure to higher colonization pressure (OR, 1.02; 95% CI, 1.01-1.04; P=.002), exposure to a carbapenem (OR, 2.25; 95% CI, 1.06-4.77; P=.04), and higher Charlson comorbidity index (OR, 1.14; 95% CI, 1.01-1.29; P=.04) were independent risk factors for KPC acquisition; the odds of KPC acquisition increased by 2% for each 1% increase in colonization pressure. CONCLUSIONS Higher colonization pressure, exposure to carbapenems, and a higher Charlson comorbidity index independently increased the odds of KPC acquisition among LTACH patients. Reducing colonization pressure (through separation of KPC-positive patients from KPC-negative patients using strict cohorts or private rooms) and reducing carbapenem exposure may prevent KPC cross transmission in this high-risk patient population. Infect Control Hosp Epidemiol 2017;38:670-677.

Duration of Colonization With Klebsiella pneumoniae Carbapenemase-Producing Bacteria at Long-Term Acute Care Hospitals in Chicago, Illinois

Knowledge of the duration of colonization with KPC is essential for infection control measures. We found that only 17% of LTACH patients lost colonization within four weeks. Half of the KPC-positive patients were still carriers when readmitted after nine months.

Background. High prevalence of Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae has been reported in long-term acute care hospitals (LTACHs), in part because of frequent readmissions of colonized patients. Knowledge of the duration of colonization with KPC is essential to identify patients at risk of KPC colonization upon readmission and to make predictions on the effects of transmission control measures.

Methods. We analyzed data on surveillance isolates that were collected at 4 LTACHs in the Chicago region during a period of bundled interventions, to simultaneously estimate the duration of colonization during an LTACH admission and between LTACH (re)admissions. A maximum-likelihood method was used, taking interval-censoring into account.

Results. Eighty-three percent of patients remained colonized for at least 4 weeks, which was the median duration of LTACH stay. Between LTACH admissions, the median duration of colonization was 270 days (95% confidence interval, 91–∞).

Conclusions. Only 17% of LTACH patients lost colonization with KPC within 4 weeks. Approximately half of the KPC-positive patients were still carriers when readmitted after 9 months. Infection control practices should take prolonged carriage into account to limit transmission of KPCs in LTACHs.

Intestinal Carriage of Carbapenemase-Producing Organisms: Current Status of Surveillance Methods

Carbapenemases have become a significant mechanism for broad-spectrum β-lactam resistance in Enterobacteriaceae and other Gram-negative bacteria such as Pseudomonas and Acinetobacter spp. Intestinal carriage of carbapenemase-producing organisms (CPOs) is an important source of transmission. Isolation of carriers is one strategy that can be used to limit the spread of these bacteria. In this review, we critically examine the clinical performance, advantages, and disadvantages of methods available for the detection of intestinal carriage of CPOs. Culture-based methods (Centers for Disease Control and Prevention [CDC] protocols, chromogenic media, specialized agars, and double-disk synergy tests) for detecting carriage of CPOs are convenient due to their ready availability and low cost, but their limited sensitivity and long turnaround time may not always be optimal for infection control practices. Contemporary nucleic acid amplification techniques (NAATs) such as real-time PCR, hybridization assays, loop-mediated isothermal amplification (LAMP), or a combined culture and NAAT approach may provide fast results and/or added sensitivity and specificity compared with culture-based methods. Infection control practitioners and clinical microbiologists should be aware of the strengths and limitations of available methods to determine the most suitable approach for their medical facility to fit their infection control needs.

Performance of four different agar plate methods for rectal swabs, synergy disk tests and metallo-β-lactamase Etest for clinical isolates in detecting carbapenemase-producing Klebsiella pneumoniae

The aims of the study were to compare four different agar plate methods in the identification of carbapenemase-producing Klebsiella pneumoniae (CP-Kp) from rectal samples and to assess the role of phenotypic methodologies in the identification of carbapenemase type from clinical K. pneumoniae isolates. Two chromogenic agars (Brilliance CRE and CHROMagar KPC) were compared to MacConkey agar plates with ertapenem (ERT) or imipenem (IMP) disks for the identification of CP-Kp from 912 rectal swabs. CP-Kp was detected in 329 samples by either agar methodology (299 K. pneumoniae carbapenemase positive, 27 Verona integron-encoded metallo-β-lactamase positive and 3 K. pneumoniae carbapenemase and Verona integron-encodedmetallo-β-lactamase positive). Sensitivity of Brilliance CRE, CHROMagar KPC and MacConkey agar plus IMP or ERT disk (inhibition zone <25 mm) was 96.8, 99.2, 67.2 and 81.8 %, while specificity was 90.9, 78.2, 98.1 and 97.9 %, respectively. Synergy meropenem-disk tests with EDTA or phenylboronic acid were used in order to detect the carbapenemase type as compared to PCR results (blaVIM, blaKPC and blaNDM) from 2515 isolates with reduced susceptibility to any of the Etest-examined carbapenems (ERT, IMP or meropenem). Metallo-β-lactamase MP/MPI Etest was applied in 616 isolates. Sensitivity was 98.4, 90.9 and 82.2 % for phenylboronic acid synergy test, EDTA synergy test and metallo-β-lactamase Etest, respectively, while their specificity was high (>97.5 %). Phenotypic methodologies can provide reliable results for the identification of carbapenemase production among K. pneumoniae isolates. Chromogenic agars can be applied in high-risk patients as part of surveillance and infection control programs.

Multisite Evaluation of Cepheid Xpert Carba-R Assay for Detection of Carbapenemase-Producing Organisms in Rectal Swabs

Rapid identification of patients who are colonized with carbapenemase-producing organisms (CPO) is included in multiple national guidelines for containment of these organisms. In a multisite study, we evaluated the performance of the Cepheid Xpert Carba-R assay, a qualitative diagnostic test that was designed for the rapid detection and differentiation of the bla_KPC, bla_NDM, bla_VIM, bla_OXA-48, and bla_IMP-1 genes from rectal swab specimens. A double rectal swab set was collected from 383 patients admitted at four institutions (2 in the United States, 1 in the United Kingdom, 1 in Spain). One swab was used for reference culture (MacConkey broth containing 1 mg/liter of meropenem and subcultured to a MacConkey agar plate with a 10-μg meropenem disk) and for sequencing of DNA obtained from carbapenem-nonsusceptible isolates for carbapenemase identification. The other swab was used for the Xpert Carba-R assay. In addition to the clinical rectal swabs, 250 contrived specimens (108 well-characterized CPO and 142 negative controls spiked onto negative rectal swabs) were tested. Overall, 149/633 (23.5%) samples were positive by the Xpert Carba-R assay. In 6 samples, multiple targets were detected (4 VIM/OXA-48, 1 IMP-1/NDM, and 1 NDM/KPC). The Xpert Carba-R assay detected 155 targets (26 IMP-1, 30 VIM, 27 NDM, 33 KPC, 39 OXA-48) within a time range of 32 to 48 min. The sensitivity, specificity, and positive and negative predictive values of the Xpert Carba-R assay compared to those of the reference culture and sequencing results were 96.6% (95% confidence interval [CI], 92.2% to 98.9%), 98.6% (95% CI, 97.1% to 99.4%), 95.3%, and 99.0%, respectively. The Cepheid Xpert Carba-R assay is an accurate and rapid test to identify rectal colonization with CPO, which can guide infection control programs to limit the spread of these organisms.

Mechanisms of ertapenem resistance in Enterobacteriaceae isolates in a tertiary university hospital

The aim of this study was to investigate the molecular mechanisms of ertapenem resistance among Enterobacteriaceae isolates in a clinical microbiology laboratory at a tertiary university hospital. A total of 40 clinical isolates including 20 resistant and 20 intermediate isolates were collected from August 2012 to July 2013. Ertapenem susceptibility was confirmed by the broth microdilution method. PCR and sequencing analysis of carbapenemase, AmpC β-lactamase, and extended-spectrum β-lactamase (ESBL) genes were performed. Outer membrane proteins (OMPs) were examined by urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Molecular epidemiology studies were performed by pulsed-field gel electrophoresis (PFGE). AmpC β-lactamases and ESBLs were found in 32 (80.0%) and 20 (50.0%) of the 40 isolates with ertapenem non-susceptibility, respectively. Distributions of β-lactamase genes differed among the species. One Citrobacter freundii isolate among the 40 isolates with ertapenem non-susceptibility carrying the blaIMP-1 associated class 1 integron was detected. SDS-PAGE of OMPs showed altered or greatly diminished expression of porins in all isolates of Klebsiella pneumoniae (n=5) and Enterobacter cloacae (n=11) with ertapenem resistance. Porin alterations were less common among the isolates with intermediate susceptibility (4/19). Integration of the results of molecular analysis of β-lactamases and OMP analysis revealed that most of the isolates with ertapenem resistance exhibited β-lactamase activity and porin alteration. PFGE revealed that most isolates were epidemiologically unrelated. Ertapenem resistance in clinical Enterobacteriaceae isolates was associated with β-lactamase activity and porin alteration. Even though carbapenemase-producing Enterobacteriaceae are still rare, continuous monitoring and infection control for carbapenem-resistant Enterobacteriaceae are necessary.

Evaluation of Multiple Methods for Detection of Gastrointestinal Colonization of Carbapenem-Resistant Organisms from Rectal Swabs

Rectal swabs from high-risk patients were screened for carbapenem-resistant organisms (CROs) using several methods. The direct MacConkey plate method was the most sensitive for CROs (95%), while chromID CARBA and the Check-Direct CPE screen assay were the most sensitive for the detection of carbapenemase-producing organisms (CPOs) (100%; all blaKPC). All methods had a specificity of >90% for CROs, and for CPOs, the specificity ranged from 85 to 98%. Broth enrichment methods performed poorly compared to direct inoculation methods, negating the need for the broth enrichment step.

Screening of nursing home residents for colonization with carbapenem-resistant Enterobacteriaceae admitted to acute care hospitals: Incidence and risk factors

BACKGROUND

There are increasing reports of multidrug-resistant gram-negative bacilli in nursing homes and acute care hospitals.

METHODS

We performed a point prevalence survey to detect fecal carriage of gram-negative bacteria carrying carbapenem resistance genes or which were otherwise resistant to carbapenem antibiotics among 500 consecutive admissions from local nursing homes to 2 hospitals in Providence, Rhode Island. We performed a case-control study to identify risk factors associated with carriage of carbapenem-resistant Enterobacteriaceae (CRE).

RESULTS

There were 404 patients with 500 hospital admissions during which they had rectal swab samples cultured. Fecal carriage of any carbapenem-resistant or carbapenemase- producing gram-negative bacteria was found in 23 (4.6%) of the 500 hospital admissions, including 7 CRE (1.4%), 2 (0.4%) of which were Klebsiella pneumoniae carbapenemase (ie, blaKPC) producing (CPE) Citrobacter freundii, 1 of which was carbapenem susceptible by standard testing methods. Use of a gastrostomy tube was associated with CRE carriage (P = .04). We demonstrated fecal carriage of carbapenem-resistant or carbapenemase-producing gram-negative bacteria in 4.6% of nursing home patients admitted to 2 acute care hospitals, but only 0.4% of such admissions were patients with fecal carriage of CPE. Use of gastrostomy tubes was associated with fecal carriage of gram-negative bacteria with detectable carbapenem resistance.

CONCLUSION

CRE fecal carriage is uncommon in our hospital admissions from nursing homes.

Modeling spread of KPC-producing bacteria in long-term acute care hospitals in the Chicago region, USA

OBJECTIVE

Prevalence of bla KPC-encoding Enterobacteriaceae (KPC) in Chicago long-term acute care hospitals (LTACHs) rose rapidly after the first recognition in 2007. We studied the epidemiology and transmission capacity of KPC in LTACHs and the effect of patient cohorting.

METHODS

Data were available from 4 Chicago LTACHs from June 2012 to June 2013 during a period of bundled interventions. These consisted of screening for KPC rectal carriage, daily chlorhexidine bathing, medical staff education, and 3 cohort strategies: a pure cohort (all KPC-positive patients on 1 floor), single rooms for KPC-positive patients, and a mixed cohort (all KPC-positive patients on 1 floor, supplemented with KPC-negative patients). A data-augmented Markov chain Monte Carlo (MCMC) method was used to model the transmission process.

RESULTS

Average prevalence of KPC colonization was 29.3%. On admission, 18% of patients were colonized; the sensitivity of the screening process was 81%. The per admission reproduction number was 0.40. The number of acquisitions per 1,000 patient days was lowest in LTACHs with a pure cohort ward or single rooms for colonized patients compared with mixed-cohort wards, but 95% credible intervals overlapped.

CONCLUSIONS

Prevalence of KPC in LTACHs is high, primarily due to high admission prevalence and the resultant impact of high colonization pressure on cross transmission. In this setting, with an intervention in place, patient-to-patient transmission is insufficient to maintain endemicity. Inclusion of a pure cohort or single rooms for KPC-positive patients in an intervention bundle seemed to limit transmission compared to use of a mixed cohort.

Evaluation of phenotypic tests to detect carbapenem-resistant Enterobacteriaceae in colonized patients hospitalized in intensive care units

In this study, we aimed to evaluate the performance of different phenotypic tests to detect carbapenem-resistant Enterobacteriaceae.

Three different phenotypic methods were evaluated: (1) combined-disk test of meropenem plus phenylboronic acid or EDTA reading after 24 h and 48 h; (2) selective/chromogenic read after 24 h and after 48 h; and (3) overnight selective enrichment broth containing 10 μg ertapenem disk followed by culture on MacConkey agar. A positive result in at least one of the methods was submitted to PCR for bla_NDM-1, bla_OXA-48, bla_KPC, bla_SPM-1, bla_IMP, and bla_GES detection.

Carbapenem-resistant Enterobacteriaceae was detected in 31 (30.4%) of 102 rectal swabs evaluated. All isolates showed to be KPC-2-producing organisms. Results showed excellent agreement among the evaluated tests (positive and negative) (kappa = 0.88).

It is important to state that combined-disk test with phenylboronic acid is not suitable for bacterial identification/isolation. Conversely, selective/chromogenic agar after 48h of incubation showed to be a useful tool, with the advantage of presumptive bacterial identification.

Carbapenemase-producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE) were almost nonexistent up to the 1990s, but are today encountered routinely in hospitals and other healthcare facilities in many countries including the United States. KPC-producing Klebsiella pneumoniae was the first to emerge and spread globally and is endemic in the United States, Israel, Greece, and Italy. Recently, NDM-producing Enterobacteriaceae and OXA-48-producing K. pneumoniae appear to be disseminating from South Asia and Northern Africa, respectively. They are almost always resistant to all β-lactams including carbapenems and many other classes. Mortality from invasive CPE infections reaches up to 40%. To obtain the maximal benefit from the limited options available, dosing of antimicrobial agents should be optimized based on pharmacokinetic data, especially for colistin and carbapenems. In addition, multiple observational studies have associated combination antimicrobial therapy with lower mortality compared with monotherapy for these infections. The outcomes appear to be especially favorable when patients are treated with a carbapenem and a second agent such as colistin, tigecycline, and gentamicin, but the best approach is yet to be defined.

Prevention of colonization and infection by Klebsiella pneumoniae carbapenemase-producing enterobacteriaceae in long-term acute-care hospitals

BACKGROUND

Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae (hereafter "KPC") are an increasing threat to healthcare institutions. Long-term acute-care hospitals (LTACHs) have especially high prevalence of KPC.

METHODS

Using a stepped-wedge design, we tested whether a bundled intervention (screening patients for KPC rectal colonization upon admission and every other week; contact isolation and geographic separation of KPC-positive patients in ward cohorts or single rooms; bathing all patients daily with chlorhexidine gluconate; and healthcare-worker education and adherence monitoring) would reduce colonization and infection due to KPC in 4 LTACHs with high endemic KPC prevalence. The study was conducted between 1 February 2010 and 30 June 2013; 3894 patients were enrolled during the preintervention period (lasting from 16 to 29 months), and 2951 patients were enrolled during the intervention period (lasting from 12 to 19 months).

RESULTS

KPC colonization prevalence was stable during preintervention (average, 45.8%; 95% confidence interval [CI], 42.1%-49.5%), declined early during intervention, then reached a plateau (34.3%; 95% CI, 32.4%-36.2%; P<.001 for exponential decline). During intervention, KPC admission prevalence remained high (average, 20.6%, 95% CI, 19.1%-22.3%). The incidence rate of KPC colonization fell during intervention, from 4 to 2 acquisitions per 100 patient-weeks (P=.004 for linear decline). Compared to preintervention, average rates of clinical outcomes declined during intervention: KPC in any clinical culture (3.7 to 2.5/1000 patient-days; P=.001), KPC bacteremia (0.9 to 0.4/1000 patient-days; P=.008), all-cause bacteremia (11.2 to 7.6/1000 patient-days; P=.006) and blood culture contamination (4.9 to 2.3/1000 patient-days; P=.03).

CONCLUSIONS

A bundled intervention was associated with clinically important and statistically significant reductions in KPC colonization, KPC infection, all-cause bacteremia, and blood culture contamination in a high-risk LTACH population.

Evaluation of five chromogenic agar media and the Rosco Rapid Carb screen kit for detection and confirmation of carbapenemase production in Gram-negative bacilli

An efficient workflow to screen for and confirm the presence of carbapenemase-producing Gram-negative bacilli was developed by evaluating five chromogenic screening agar media and two confirmatory assays, the Rapid Carb screen test (Rosco Diagnostica A/S, Taastrup, Denmark) and the modified Hodge test. A panel of 150 isolates was used, including 49 carbapenemase-producing isolates representing a variety of β-lactamase enzyme classes. An evaluation of analytical performance, assay cost, and turnaround time indicated that the preferred workflow (screening test followed by confirmatory testing) was the chromID Carba agar medium (bioMérieux, Marcy l'Étoile, France), followed by the Rapid Carb screen test, yielding a combined sensitivity of 89.8% and a specificity of 100%. As an optional component of the workflow, a determination of carbapenemase gene class via molecular means could be performed subsequent to confirmatory testing.

Fecal carriage of carbapenem-resistant Enterobacteriaceae in a Chinese university hospital

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) is widespread in China. To date, no study available has specifically determined the prevalence and risk factors of inpatients with CRE intestinal colonization in this region.

METHODS

Stool samples were screened for the presence of CRE in a Chinese university hospital. A case-control study was performed to identify risk factors associated with CRE fecal colonization. Case patients were those who had CRE colonization. Control subjects had no microbiologic evidence of CRE colonization. Clinical data were obtained from the medical record.

RESULTS

The prevalence of CRE was 6.6% (20/303 patients), of which 8 had carbapenemase-producing isolates. KPC-2, IMP-4, and NDM-1 were detected from these isolates. Hospital readmissions (odds ratio [OR], 58.067; 95% confidence interval [95% CI]: 5.517-611.134; P = .001), sickbed changes (OR, 45.904; 95% CI: 8.484-248.376; P < .001), invasive procedures (OR, 8.322; 95% CI: 1.996-34.690; P = .004), and vancomycin (OR, 11.552; 95% CI: 1.155-115.574; P = .037) were independently associated with CRE colonization.

CONCLUSION

This study demonstrated that asymptomatic intestinal carriage of CRE was relatively common in one region of China. Our study suggested that the implementation of effective infection control measures is urgently required to control the transmission of CRE in health care facilities in this country.

Comparison of the CHROMagar™ KPC, Remel Spectra™ CRE, and a direct ertapenem disk method for the detection of KPC-producing Enterobacteriaceae from perirectal swabs

In a comparison of 3 agar plate methods, we found that a novel chromogenic medium, Remel Spectra™ CRE, had the best overall sensitivity (97.8%) when compared to the CHROMagar™ KPC (76.6%) and a direct ertapenem disk method (83.0%) for the detection of blaKPC-positive Enterobacteriaceae from perirectal swabs.

Resistance to third-generation cephalosporins in human non-typhoidal Salmonella enterica isolates from England and Wales, 2010-12

OBJECTIVES

To identify the mechanism(s) underlying cefotaxime resistance in 118 of 21,641 (0.55%) non-typhoidal Salmonella enterica isolates collected from humans throughout England and Wales from January 2010 to September 2012.

METHODS

Non-duplicate isolates (n = 118) resistant to cefotaxime (MICs >1 mg/L) were screened by PCR for genes encoding CTX-M extended-spectrum β-lactamases (ESBLs) and associated ISEcp1-like elements, and for genes encoding acquired AmpC, SHV, TEM, VEB, PER and GES β-lactamases. Sequencing was used to identify specific alleles in selected isolates. Carbapenem resistance was sought by ertapenem disc screening.

RESULTS

Seventy-nine isolates (0.37% of all referred S. enterica) produced ESBLs, 37 isolates (0.17%) produced CMY-type AmpC enzymes, and 1 isolate had both enzyme types; the mechanism of cefotaxime resistance in 3 isolates could not be identified. Group 1 CTX-M genes were identified in 57 isolates belonging to 22 serotypes, with CTX-M-1 (n = 11), -15 (n = 9) and -55/57 (n = 8) the most prevalent alleles among the 29 (51%) investigated. CTX-M-2 (n = 5), -14 (n = 5), -8 (n = 1) and -65 (n = 1) were also identified. TEM-52 was identified in two isolates and SHV-12 in seven isolates. There was no evidence of carbapenem resistance. ESBL and AmpC genes were detected in both domestically acquired and travel-associated salmonellae. Eighty-nine isolates (75%) were multidrug resistant (resistant to at least three antimicrobial classes) and 42 (36%) had decreased susceptibility to ciprofloxacin (MICs 0.25-1 mg/L), with a further 13 (11%) isolates resistant (MICs >1 mg/L).

CONCLUSIONS

The prevalence of CTX-M and acquired AmpC genes in human non-typhoidal S. enterica from England and Wales is still low, but has increased from 0.03% in 2001-03 to 0.49% in 2010-12. Resistance to third-generation cephalosporins requires monitoring as it may reduce therapeutic options.

Detection of colonization by carbapenemase-producing Gram-negative Bacilli in patients by use of the Xpert MDRO assay

Detecting colonization of patients with carbapenemase-producing bacteria can be difficult. This study compared the sensitivity and specificity of a PCR-based method (Xpert MDRO) for detecting blaKPC, blaNDM, and blaVIM carbapenem resistance genes using GeneXpert cartridges to the results of culture with and without a broth enrichment step on 328 rectal, perirectal, and stool samples. The culture method included direct inoculation of a MacConkey agar plate on which a 10-μg meropenem disk was placed and plating on MacConkey agar after overnight enrichment of the sample in MacConkey broth containing 1 μg/ml of meropenem. Forty-three (13.1%) samples were positive by PCR for blaKPC and 11 (3.4%) were positive for blaVIM; none were positive for blaNDM. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the PCR assay for blaKPC were 100%, 99.0%, 93.0%, and 100%, respectively, compared to broth enrichment culture and sequencing of target genes. The sensitivity, specificity, PPV, and NPV of the assay for blaVIM were 100%, 99.4%, 81.8%, and 100%, respectively. Since none of the clinical samples contained organisms with blaNDM, 66 contrived stool samples were prepared at various dilutions using three Klebsiella pneumoniae isolates containing blaNDM. The PCR assay showed 100% positivity at dilutions from 300 to 1,800 CFU/ml and 93.3% at 150 CFU/ml. The Xpert MDRO PCR assay required 2 min of hands-on time and 47 min to complete. Rapid identification of patients colonized with carbapenemase-producing organisms using multiplex PCR may help hospitals to improve infection control activities.

Rapid and direct real-time detection of blaKPC and blaNDM from surveillance samples

We assessed the performance of a duplex real-time PCR assay for bla(KPC) and bla(NDM) performed directly (D-PCR) on perianal and perirectal swabs and stool. Spiked specimens and 126 clinical surveillance swabs (comprising a sensitivity panel of 46 perirectal double swabs previously determined to be culture positive for bla(KPC)-PCR-positive Enterobacteriaceae and a specificity panel of 80 perianal swabs from patients at risk of carbapenemase-producing Enterobacteriaceae [CPE] colonization) were studied. For the surveillance swabs, D-PCR was compared to PCR after broth enrichment (BE-PCR) and two culture-based methods: the HardyCHROM ESBL agar (HC-A) and the CDC screening (CDC-A) methods. PCR was performed on morphologically distinct colonies that were isolated by culture. All of the initial PCR testing was done without extraction using a simple lysis procedure. The analytical sensitivities of D-PCR for bla(KPC) were 9 CFU/μl (for swabs) and 90 CFU/μl (for stool), and for bla(NDM), it was 1.9 CFU/μl (for both swabs and stool). In the clinical sensitivity panel, D-PCR and BE-PCR were initially positive for bla(KPC) in 41/46 (89.1%) and 43/46 (93.5%) swabs, respectively. The swabs that were initially negative by D-PCR (n = 5) and BE-PCR (n = 3) were visibly stool soiled; all swabs were bla(KPC) positive upon repeat testing after lysate extraction. The CDC-A and HC-A yielded bla(KPC)-positive Enterobacteriaceae from 36/46 (78.3%) and 35/46 (76.1%) swabs, respectively (sensitivities of D-PCR/BE-PCR postextraction of soiled specimens versus HC-A, P = 0.0009, and versus CDC-A, P = 0.0016). All swabs in the specificity panel were negative for CPE by all four methods. D-PCR allows for the timely detection of bla(KPC) and bla(NDM) carriage with excellent sensitivity when specimens visibly soiled with stool undergo preparatory extraction.

The importance of long-term acute care hospitals in the regional epidemiology of Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae

BACKGROUND

In the United States, Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae are increasingly detected in clinical infections; however, the colonization burden of these organisms among short-stay and long-term acute care hospitals is unknown.

METHODS

Short-stay acute care hospitals with adult intensive care units (ICUs) in the city of Chicago were recruited for 2 cross-sectional single-day point prevalence surveys (survey 1, July 2010-January 2011; survey 2, January-July 2011). In addition, all long-term acute care hospitals (LTACHs) in the Chicago region (Cook County) were recruited for a single-day point prevalence survey during January-May 2011. Swab specimens were collected from rectal, inguinal, or urine sites and tested for Enterobacteriaceae carrying blaKPC.

RESULTS

We surveyed 24 of 25 eligible short-stay acute care hospitals and 7 of 7 eligible LTACHs. Among LTACHs, 30.4% (119 of 391) of patients were colonized with KPC-producing Enterobacteriaceae, compared to 3.3% (30 of 910) of short-stay hospital ICU patients (prevalence ratio, 9.2; 95% confidence interval, 6.3-13.5). All surveyed LTACHs had patients harboring KPC (prevalence range, 10%-54%), versus 15 of 24 short-stay hospitals (prevalence range, 0%-29%). Several patient-level covariates present at the time of survey-LTACH facility type, mechanical ventilation, and length of stay-were independent risk factors for KPC-producing Enterobacteriaceae colonization.

CONCLUSIONS

We identified high colonization prevalence of KPC-producing Enterobacteriaceae among patients in LTACHs. Patients with chronic medical care needs in long-term care facilities may play an important role in the spread of these extremely drug-resistant pathogens.

A combined disk test for direct differentiation of carbapenemase-producing enterobacteriaceae in surveillance rectal swabs

Carbapenemase-producing Enterobacteriaceae (CPE) are rapidly spreading worldwide. Early detection of fecal CPE carriers is essential for effective infection control. Here, we evaluated the performance of a meropenem combined disk test (CDT) for rapidly differentiating CPE isolates directly from rectal swabs. The screening method was applied for 189 rectal swabs from hospitalized patients at high risk for CPE carriage. Swabs were suspended in 1 ml saline and cultured for confluent growth onto a MacConkey agar plate with a meropenem (MER) disk alone, a MER disk plus phenyl boronic acid (PBA), a MER disk plus EDTA, and a MER disk plus PBA and EDTA. An inhibition zone of ≤ 25 mm around the MER disk alone indicated carriage of carbapenem-resistant organisms. Furthermore, ≥ 5-mm differences in the inhibition zone between MER disks without and with the inhibitors (PBA, EDTA, or both) were considered positive results for detecting Klebsiella pneumoniae carbapenemase (KPC), metallo-β-lactamase (MBL), or both carbapenemases, respectively. For comparison, rectal suspensions were tested using MacConkey plates with ertapenem (MacERT) disks and PCR (PCR-S) for carbapenemase genes. Of the 189 samples, 97 were genotypically confirmed as CPE positive by one of the three protocols tested. The CDT, MacERT disks, and PCR-S assays exhibited sensitivities of 94.8%, 96.9%, and 94.8% and specificities of 100%, 98.9%, and 100%, respectively, for detecting CPE-positive swabs. Moreover, the CDT correctly differentiated the production of KPC, MBL, or both carbapenemases in 78 of the 97 (80.4%) CPE-positive rectal swabs. Our results demonstrate that the CDT may provide a simple and inexpensive method for detecting and differentiating the carbapenemase type within a single day without requiring further testing and additional delay, supporting the timely implementation of infection control measures.

Carbapenemase-producing Enterobacteriaceae: now that the storm is finally here, how will timely detection help us fight back?

Acquired carbapenemases of the Ambler Classes A, B and D have gradually disseminated over the past decade among isolates of the Enterobacteriaceae family. Located on highly mobile genetic elements, these enzymes have established their presence in successful bacterial clones, signaling the prelude to a novel endemic era in the hospital setting. In such a context, prompt detection of carbapenemase-producing microorganisms seems warranted, not only for the selection of an appropriate antibiotic regimen, but also for organizing and implementing effective surveillance and infection control measures. However, issues regarding detection, confirmatory testing and characterization persist. Determination of carbapenemase production via susceptibility pattern interpretation may not always be feasible, confirmatory testing remains debatable and precise characterization is a challenge for the clinical laboratory. We aim to review the current situation from a laboratory point of view, highlighting the tools that have been proposed in an effort to help outline reliable screening and detection procedures, with inhibitor-based phenotypic testing as the cornerstone of these strategies, and discuss the necessity for implementing identification of possible producers in the everyday workflow.

Evaluation of the NucliSENS EasyQ KPC assay for detection of Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae

The NucliSENS EasyQ KPC assay (bioMérieux SA, Marcy l'Etoile, France) was compared with a routinely used phenotypic method for detection of Enterobacteriaceae producing Klebsiella pneumoniae carbapenemase (KPC)-type carbapenemases, using 806 stool samples and rectal swabs. Compared with the phenotypic method, the EasyQ KPC assay had a sensitivity and specificity of 93.3% and 99.0%, respectively, in this setting, with diverse KPC producers not limited to ST258 Klebsiella pneumoniae.

[Multiresistant gram-negative bacteria. A bacterial challenge of the twenty-first century]

The incidence of human-pathogenic microorganisms with resistance or even complete insensitivity to broad-spectrum antibiotics is increasing. This poses a serious challenge to infection control in hospitals and to hygiene strategies in clinical areas with critically ill patients, particularly intensive care or transplant units. These microorganisms create problems that are seemingly impossible to solve at present. The management of gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) has been facilitated by evidence-based recommendations resulting in a measurable decrease in the incidence of infection and, where treatment is concerned, in a selection of reliably effective drugs for clinicians. However, in the more frequent cases of multiresistant gram-negative (MRGN) pathogens, the only option is the use of poorly defined regimens with older drugs, which carry the risk of serious side effects and organ toxicities. This article presents a comparative analysis of hospital hygiene management for MRSA and MRGN pathogens, pointing out both similarities and features which are unique to MRGN pathogens.

Anatomic sites of patient colonization and environmental contamination with Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae at long-term acute care hospitals

OBJECTIVE

To determine anatomic sites of colonization in patients and to assess environmental contamination with Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae.

DESIGN, SETTING, AND PATIENTS

We conducted a cross-sectional microbiologic survey of 33 patients and their environments at 6 long-term acute care hospitals (LTACHs) in metropolitan Chicago. Swab samples of anatomic sites and inanimate surfaces in patients' rooms and common areas were cultured. bla(KPC) was verified by polymerase chain reaction. Patient charts were reviewed for covariates known to be associated with colonization and environmental contamination.

RESULTS

Mean age was 66 years. Median length of stay prior to surveillance was 50 days. Thirty (91%) patients were mechanically ventilated, 32 (97%) were bedbound, and 27 (82%) had fecal incontinence. Of the 24 patients with KPC-producing Enterobacteriaceae recovered from 1 or more anatomic sites, 23 (96%) had KPC-producing Enterobacteriaceae detected at 1 or more skin sites. Skin colonization was more common in patients with positive rectal/stool swab cultures or positive clinical cultures ([Formula: see text]). Rectal/stool swab was the single most sensitive specimen for detecting KPC-producing Enterobacteriaceae colonization (sensitivity, 88%; 95% confidence interval [CI], 68%-97%); addition of inguinal skin swab culture resulted in detection of all colonized patients (sensitivity, 100%; 95% CI, 86%-100%). Only 2 (0.5%) of 371 environmental specimens grew KPC-producing Enterobacteriaceae.

CONCLUSIONS

Culture of more than 1 anatomic site was required to detect all KPC-producing Enterobacteriaceae-colonized patients. Skin colonization was common, but environmental contamination was rare. These results can guide development of multimodal interventions for control of KPC-producing Enterobacteriaceae in LTACHs.

Carbapenem disks on MacConkey agar in screening methods for detection of carbapenem-resistant Gram-negative rods in stools

Direct plating of simulated stool specimens on MacConkey agar (MCA) with 10-μg ertapenem, meropenem, and imipenem disks allowed the establishment of optimal zone diameters for the screening of carbapenem-resistant Gram-negative rods (CRGNR) of ≤ 24 mm (ertapenem), ≤ 34 mm (meropenem), and ≤ 32 mm (imipenem).

Transfer from high-acuity long-term care facilities is associated with carriage of Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae: a multihospital study

OBJECTIVE

To determine whether transfer from a long-term care facility (LTCF) is a risk factor for colonization with Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae upon acute care hospital admission.

DESIGN

Microbiologic survey and nested case-control study.

SETTING

Four hospitals in a metropolitan area (Chicago) with an early KPC epidemic.

PATIENTS

Hospitalized adults.

METHODS

Patients transferred from LTCFs were matched 1∶1 to patients admitted from the community by age (± 10 years), admitting clinical service, and admission date (± 2 weeks). Rectal swab specimens were collected within 3 days after admission and tested for KPC-producing Enterobacteriaceae. Demographic and clinical information was extracted from medical records.

RESULTS

One hundred eighty patients from LTCFs were matched to 180 community patients. KPC-producing Enterobacteriaceae colonization was detected in 15 (8.3%) of the LTCF patients and 0 (0%) of the community patients ([Formula: see text]). Prevalence of carriage differed by LTCF subtype: 2 of 135 (1.5%) patients from skilled nursing facilities without ventilator care (SNFs) were colonized upon admission, compared to 9 of 33 (27.3%) patients from skilled nursing facilities with ventilator care (VSNFs) and 4 of 12 (33.3%) patients from long-term acute care hospitals (LTACHs; [Formula: see text]). In a multivariable logistic regression model adjusted for a propensity score that predicted LTCF subtype, patients admitted from VSNFs or LTACHs had 7.0-fold greater odds of colonization (ie, odds ratio; 95% confidence interval, 1.3-42; [Formula: see text]) with KPC-producing Enterobacteriaceae than patients from an SNF.

CONCLUSIONS

Patients admitted to acute care hospitals from high-acuity LTCFs (ie, VSNFs and LTACHs) were more likely to be colonized with KPC-producing Enterobacteriaceae than were patients admitted from the community. Identification of healthcare facilities with a high prevalence of colonized patients presents an opportunity for focused interventions that may aid regional control efforts.

Direct detection and genotyping of Klebsiella pneumoniae carbapenemases from urine by use of a new DNA microarray test

Klebsiella pneumoniae carbapenemases (KPCs) are considered a serious threat to antibiotic therapy, as they confer resistance to carbapenems, which are used to treat extended-spectrum beta-lactamase (ESBL)-producing bacteria. Here, we describe the development and evaluation of a DNA microarray for the detection and genotyping of KPC genes (bla(KPC)) within a 5-h period. To test the whole assay procedure (DNA extraction plus a DNA microarray assay) directly from clinical specimens, we compared two commercial DNA extraction kits (the QIAprep Spin miniprep kit [Qiagen] and the urine bacterial DNA isolation kit [Norgen]) for the direct DNA extraction from urine samples (dilution series spiked in human urine). Reliable single nucleotide polymorphism (SNP) typing was demonstrated using 1 × 10(5) CFU/ml urine for Escherichia coli (Qiagen and Norgen) and 80 CFU/ml urine, on average, for K. pneumoniae (Norgen). This study presents, for the first time, the combination of a new KPC microarray with commercial sample preparation for detecting and genotyping microbial pathogens directly from clinical specimens; this paves the way toward tests providing epidemiological and diagnostic data, enabling better antimicrobial stewardship.