The EC-COMPASS: Long-term, multi-centre surveillance of Enterobacter cloacae complex - a clinical perspective

BACKGROUND

Enterobacter cloacae complex (ECCO) comprises closely related Enterobacterales, causing a variety of infections ranging from mild urinary tract infections to severe bloodstream infections. ECCO has emerged as a significant cause of healthcare-associated infections, particularly in neonatal and adult intensive care.

AIM

The Enterobacter Cloacae COMplex PASsive Surveillance (EC-COMPASS) aims to provide a detailed multi-centre overview of ECCO epidemiology and resistance patterns detected in routine microbiological diagnostics in four German tertiary-care hospitals.

METHODS

In a sentinel cluster of four German tertiary-care hospitals, all culture-positive ECCO results between 1st January 2020 and 31st December 2022, were analysed based on Hybase® laboratory data.

FINDINGS

Analysis of 31,193 ECCO datasets from 14,311 patients revealed a higher incidence in male patients (P<0.05), although no significant differences were observed in ECCO infection phenotypes. The most common sources of ECCO were swabs (42.7%), urine (17.5%), respiratory secretions (16.1%), blood cultures (8.9%) and tissue samples (5.6%). The annual bacteraemia rate remained steady at approximately 33 cases per hospital. Invasive ECCO infections were predominantly found in oncology and intensive care units. Incidences of nosocomial outbreaks were infrequent and limited in scope. Notably, resistance to carbapenems was consistently low.

CONCLUSION

EC-COMPASS offers a profound clinical perspective on ECCO infections in German tertiary-healthcare settings, highlighting elderly men in oncology and intensive care units as especially vulnerable to ECCO infections. Early detection strategies targeting at-risk patients could improve ECCO infection management.

Late-onset Enterobacter cloacae sepsis in very-low-birth-weight neonates: experience in a medical center

OBJECTIVE

The objective of this study was to review the early clinical profiles and outcomes of very-low-birth-weight (VLBW) neonates with late-onset sepsis caused by Enterobacter cloacae.

METHODS

We reviewed the medical records of VLBW neonates whose blood and/or cerebral spinal fluid yielded E. cloacae after 3 days of hospitalization in our neonatal intensive care unit.

RESULTS

From January 1997 to December 2006, a total of 29 episodes of E. cloacae infection occurred in 28 VLBW neonates. The onset of E. cloacae infection ranged from 4 to 70 days (27.4 +/- 9.6) days after birth. The most common symptoms and signs of sepsis were desaturation (58.6%), tachycardia (58.6%), apnea (55.2%), unstable body temperature (48.3%), and decreased activity (44.8%). The infected neonates had an average of four kinds of symptoms in each sepsis episode. The most common laboratory findings in VLBW neonates with E. cloacae sepsis were thrombocytopenia (65.5%), C-reactive protein > or = 1 mg/dL (55.2%), band-form neutrophils > or = 5% (41.4%), and leucopoenia (20.7%). Empirical intravenous antibiotic therapy comprising piperacillin (or piperacillin and tazobactam) and gentamicin (or amikacin) was successful in the early treatment of 24 episodes of E. cloacae sepsis in 25 patients. Three neonates (10.7%) died due to E. cloacae sepsis. Four neonates (14.3%) developed E. cloacae meningitis, and two of them developed brain abscesses.

CONCLUSIONS

E. cloacae infection in VLBW neonates usually presents with nonspecific symptoms and signs. Early recognition of sepsis and empirical combination of piperacillin (or piperacillin and tazobactam) and gentamicin (or amikacin) may be useful for treatment of sepsis caused by this highly virulent pathogen.

Management of an outbreak of Enterobacter cloacae in a neonatal unit using simple preventive measures

Enterobacter cloacae is becoming an increasingly important nosocomial pathogen. Outbreaks of E. cloacae in intensive care units and burns units have been described frequently. In December 1999, a neonate with line sepsis was transferred from a university hospital to the neonatal unit of the Diakonessen Hospital. Blood culture yielded E. cloacae. An outbreak of E. cloacae was occurring in the university hospital at that time. In February 2000, a second neonate in our hospital developed line sepsis caused by E. cloacae. Direct measures taken included cohorting of infected children, disinfection of incubators, thermometers and wards, and screening patients. Of nine neonates, seven were colonized with E. cloacae. Despite these measures, the outbreak continued. Forty-one patients were screened; 15 were colonized. Environmental searches yielded E. cloacae in a sink and on two thermometers. Sixteen isolates were typed by arbitrarily primed PCR using four primers. All the patient isolates and the two isolates from thermometers were identical. The strain isolated from the sink was unrelated. Amplified fragment length polymorphism typing showed that the outbreak clone was identical to that in the university hospital. After the introduction of disposable thermometer covers, E. cloacae colonization slowly decreased.

Infection control in the ICU

Nosocomial infections (NIs) now concern 5 to 15% of hospitalized patients and can lead to complications in 25 to 33% of those patients admitted to ICUs. The most common causes are pneumonia related to mechanical ventilation, intra-abdominal infections following trauma or surgery, and bacteremia derived from intravascular devices. This overview is targeted at ICU physicians to convince them that the principles of infection control in the ICU are based on simple concepts and that the application of preventive strategies should not be viewed as an administrative or constraining control of their activity but, rather, as basic measures that are easy to implement at the bedside. A detailed knowledge of the epidemiology, based on adequate surveillance methodologies, is necessary to understand the pathophysiology and the rationale of preventive strategies that have been demonstrated to be effective. The principles of general preventive measures such as the implementation of standard and isolation precautions, and the control of antibiotic use are reviewed. Specific practical measures, targeted at the practical prevention and control of ventilator-associated pneumonia, sinusitis, and bloodstream, urinary tract, and surgical site infections are detailed. Recent data strongly confirm that these strategies may only be effective over prolonged periods if they can be integrated into the behavior of all staff members who are involved in patient care. Accordingly, infection control measures are to be viewed as a priority and have to be integrated fully into the continuous process of improvement of the quality of care.

A heterogeneous outbreak of Enterobacter cloacae and Serratia marcescens infections in a surgical intensive care unit

OBJECTIVE

To investigate an outbreak of invasive disease due to Enterobacter cloacae and Serratia marcescens in a surgical intensive care unit (ICU).

DESIGN

Pulsed-field gel electrophoresis (PFGE) analysis of restriction fragments was used to characterize the outbreak isolate genotypes. A retrospective cohort study of surgical ICU patients was conducted to identify risk factors associated with invasive disease. Unit staffing data were analyzed to compare staffing levels during the outbreak to those prior to and following the outbreak.

SETTING

An urban hospital in San Francisco, California.

PATIENTS

During the outbreak period, December 1997 through January 1998, there were 52 patients with a minimum ICU stay of > or = 72 hours. Of these, 10 patients fit our case definition of recovery of E. cloacae or S. marcescens from a sterile site.

RESULTS

PFGE analysis revealed a highly heterogeneous population of isolates. Bivariate analysis of patient-related risk factors revealed duration of central lines, respiratory colonization, being a burn patient, and the use of gentamicin or nafcillin to be significantly associated with invasive disease. Both respiratory colonization and duration of central lines remained statistically significant in a multivariate analysis. Staffing data suggested a temporal correlation between understaffing and the outbreak period.

CONCLUSIONS

Molecular epidemiological techniques provided a rapid means of ruling out a point source or significant cross-contamination as modes of transmission. In this setting, patient-related risk factors, such as respiratory colonization and duration of central lines, may provide a focus for heightened surveillance, infection control measures, and empirical therapy during outbreaks caused by common nosocomial pathogens. In addition, understaffing of nurses may have played a role in this outbreak, highlighting the importance of monitoring staffing levels.

Enterobacter cloacae outbreak in the NICU related to disinfected thermometers

In the first week ot December 1997, an increasing incidence of neonates colonized with multi-drug resistant Enterobacter cloacae (MR-E. cloacae) was observed in the neonatal Intensive care unit of our 950-bed university hospital. Initially, re-enforcement of infection control practices including hand disinfection and cohort isolation seemed to be sufficient to control the outbreak. Nevertheless, an increasing number of newly admitted patients was paralleled by another rise in the incidence of colonized neonates. Since E. cloacae was initially found in urine specimens of the patients, surveillance and environmental cultures were aimed at procedures and instruments that might colonize the gastro-intestinal and/or urinary tract. E, cloacae was isolated from a single cap of an electronic digital thermometer. Despite banning of this possible source, newly admitted neonates still became colonized. The unit was closed for further admissions and a second round of extensive screening was started; this time including all available thermometers and continuous rectal temperature probes. Ready-to-use 'disinfected thermometers and probes were found to be colonized with MR-E. cloacae. Observation of disinfection procedures and a laboratory investigation revealed that 'rushed disinfection with alcohol 80% led to a 1 in 10 chance of thermometers still being contaminated. Furthermore, alcoholic hand rub used for convenience disinfection failed to disinfect thermometers in 40% and 20% of the cases when done in a 'rushed' or 'careful' fashion, respectively. Adequate disinfection of the thermometers led to the control of the outbreak, with no new occurrence of MR-E. cloacae in the following months.

An antibiotic policy to prevent emergence of resistant bacilli

BACKGROUND

Fear of infection in neonatal intensive care units (NICUs) often leads to early use of empiric broad-spectrum antibiotics, a strategy that selects for resistant bacteria. We investigated whether the emergence of resistant strains could be halted by modifying the empiric antibiotic regimens to remove the selective pressure that favours resistant bacteria.

METHODS

Two identical NICUs were assigned to different empiric antibiotic regimens. On unit A, penicillin G and tobramycin were used for early-onset septicaemia, flucloxacillin and tobramycin were used for late-onset septicaemia, and no broad-spectrum beta-lactam antibiotics, such as amoxicillin and cefotaxime were used. In unit B, intravenous amoxicillin with cefotaxime was the empiric therapy. After 6 months of the study the units exchanged regimens. Rectal and respiratory cultures were taken on a weekly basis.

FINDINGS

There were 436 admissions, divided equally between the two regimens (218 in each). Three neonates treated with the penicillin-tobramycin regimen became colonised with bacilli resistant to the empirical therapy used versus 41 neonates on the amoxicillin-cefotaxime regimen (p<.0001). The relative risk for colonisation with strains resistant to the empirical therapy per 1000 patient days at risk was 18 times higher for the amoxicillin-cefotaxime regimen compared with the penicillin-tobramycin regimen (95% CI 5.6-58.0). Enterobacter cloacae was the predominant bacillus in neonates on the amoxicillin-cefotaxime regimen, whereas Escherichia coli predominated in neonates on the penicillin-tobramycin regimen. These colonisation patterns were also seen when the units exchanged regimens.

INTERPRETATION

Policies regarding the empiric use of antibiotics do matter in the control of antimicrobial resistance. A regimen avoiding amoxicillin and cefotaxime restricts the resistance problem.

Outbreak of Enterobacter cloacae related to understaffing, overcrowding, and poor hygiene practices

OBJECTIVE

To determine the cause and mode of transmission of a cluster of infections due to Enterobacter cloacae.

DESIGN AND SETTING

Retrospective cohort study in a neonatal intensive-care unit (NICU) from December 1996 to January 1997; environmental and laboratory investigations.

SUBJECTS

60 infants hospitalized in the NICU during the outbreak period.

MAIN OUTCOME MEASURES

Odds ratios (OR) linking E. cloacae colonization or infection and various exposures. All available E. cloacae isolates were typed and characterized by contour-clamped homogenous electric-field electrophoresis to confirm possible cross-transmission.

RESULTS

Of eight case-patients, two had bacteremia; one, pneumonia; one, soft-tissue infection; and four, respiratory colonization. Infants weighing <2,000 g and born before week 33 of gestation were more likely to become cases (P<.001). Multivariate analysis indicated that the use of multidose vials was independently associated with E. cloacae carriage (OR, 16.3; 95% confidence interval [CI95], 1.8-infinity; P=.011). Molecular studies demonstrated three epidemic clones. Cross-transmission was facilitated by understaffing and overcrowding (up to 25 neonates in a unit designed for 15), with an increased risk of E. cloacae carriage during the outbreak compared to periods without understaffing and overcrowding (relative risk, 5.97; CI95 2.2-16.4). Concurrent observation of healthcare worker (HCW) handwashing practices indicated poor compliance. The outbreak was terminated after decrease of work load, increase of hand antisepsis, and reinforcement of single-dose medication.

CONCLUSIONS

Several factors caused and aggravated this outbreak: (1) introduction of E. cloacae into the NICU, likely by two previously colonized infants; (2) further transmission by HCWs' hands, facilitated by substantial overcrowding and understaffing in the unit; (3) possible contamination of multidose vials with E. cloacae. Overcrowding and understaffing in periods of increased work load may result in outbreaks of nosocomial infections and should be avoided.

Colonization with broad-spectrum cephalosporin-resistant gram-negative bacilli in intensive care units during a nonoutbreak period: prevalence, risk factors, and rate of infection

OBJECTIVE

To define the epidemiology of broad-spectrum cephalosporin-resistant gram-negative bacilli in intensive care units (ICUs) during a nonoutbreak period, including the prevalence, the risk factors for colonization, the frequency of acquisition, and the rate of infection.

DESIGN

Prospective cohort study.

SETTING

Tertiary care hospital.

PATIENTS

Consecutive patients admitted to two surgical ICUs.

MAIN OUTCOME MEASUREMENTS

Serial patient surveillance cultures screened for ceftazidime (CAZ) resistance, antibiotic and hospital exposure, and infections.

RESULTS

Of the 333 patients enrolled, 60 (18%) were colonized with CAZ-resistant gram-negative bacilli (CAZ-RGN) at admission. Clinical cultures detected CAZ-RGN in only 5% (3/60) of these patients. By using logistic regression, CAZ-RGN colonization was associated with duration of exposure to cefazolin (odds ratio, 10.3; p < or = .006) and to broad-spectrum cephalosporins/penicillins (odds ratio, 2; p < or = .03), Acute Physiology and Chronic Health Evaluation III score (odds ratio, 1.2; p < or = .008), and previous hospitalization (odds ratio, 3.1; p < or = .006). Of the 100 patients who remained in the surgical ICU for > or = 3 days, 26% acquired a CAZ-RGN. Of the 14 infections caused by CAZ-RGN, 11 (79%) were attributable to the same species present in surveillance cultures at admission to the surgical ICU.

CONCLUSIONS

Colonization with CAZ-RGN was common and was usually not recognized by clinical cultures. Most patients colonized or infected with CAZ-RGN had positive surveillance cultures at the time of admission to the surgical ICU, suggesting that acquisition frequently occurred in other wards and institutions. Patients exposed to first-generation cephalosporins, as well as broad-spectrum cephalosporins/penicillins, were at high risk of colonization with CAZ-RGN. Empirical treatment of nosocomial gram-negative infections with broad-spectrum cephalosporins, especially in the critically ill patient, should be reconsidered.

Repetitive sequence-based PCR versus pulsed-field gel electrophoresis for typing of Enterococcus faecalis at the subspecies level

Repetitive sequence-based PCR was compared to pulsed-field gel electrophoresis (PFGE) for the ability to discriminate Enterococcus faecalis isolates at the subspecies level. The BOXA2R primer, derived from repetitive sequences in Streptococcus pneumoniae, was applied to 41 isolates of E. faecalis collected from various sources. The REP1R-Dt and REP2-Dt primers, derived from the gram-negative repetitive extragenic palindromic element, were also applied to 18 selected isolates. Of the 41 isolates examined, 7 were beta-lactamase producing and 8 were vancomycin resistant. By PFGE, 17 isolates had distinct patterns; the other 24 were classified into eight different clonal groups. By PCR using the BOXA2R primer, 16 isolates generated distinct patterns; the other 25 were classified into nine different clonal groups. There were only minor differences in the PCR results obtained by using the BOXA2R primer and the REP1R-Dt and REP2-Dt primers. Two isolates among vancomycin-resistant enterococci from the greater Houston, Tex., area were related by PFGE, distinct by PCR with the BOXA2R primer, and related by PCR with the REP1R-Dt and REP2-Dt primers. Clonal relationships among the remaining 39 isolates were similar by both PFGE and PCR. PCR reliably discriminated all epidemiologically unrelated isolates. Although PCR is less time consuming than PFGE, PCR results were more difficult to interpret than PFGE results, perhaps because fewer bands were generated by PCR than by PFGE and some PCR products were inconsistently seen.

Molecular epidemiology of acquisition of ceftazidime-resistant gram-negative bacilli in a nonoutbreak setting

We prospectively studied the acquisition of ceftazidime-resistant gram-negative bacilli (CAZ-RGN) in two surgical intensive care units (SICU) during a nonoutbreak period. Surveillance cultures were obtained from patients at the time of admission and serially thereafter. CAZ-RGN isolates were typed by pulsed-field gel electrophoresis (PFGE). Three hundred and forty-three patients were enrolled from whom 1,621 baseline and follow-up cultures were obtained. The most common species isolated from patients were Pseudomonas aeruginosa (22), Enterobacter cloacae (21), Acinetobacter spp. (13), Enterobacter aerogenes (11), Citrobacter spp. (10), Pseudomonas spp. (non P. aeruginosa) (9), and Stenotrophomonas spp. (7). For each species, PFGE strain types were highly diverse; no single type was recovered from more than four patients. Twenty-eight patients acquired a CAZ-RGN during the SICU stay; in six (21%), emergence of resistance from a previously susceptible strain was documented on the basis of matching serial strain types. Transmission of CAZ-RGN between patients occurred but was infrequent, as judged by analyzing strain types of epidemiologically linked patients. In conclusion, colonization with CAZ-RGN in SICU was associated with diverse species and strains, as determined by molecular typing. Emergence of resistance from previously susceptible strains appeared to be more important than horizontal transmission in acquisition of CAZ-RGN in a nonoutbreak period.

Use of interrepeat PCR fingerprinting to investigate an Acinetobacter baumannii outbreak in an intensive care unit

An epidemiological investigation of an outbreak of Acinetobacter baumannii among patients on 2 closely related intensive care units (ICU) was performed by molecular typing with interrepeat polymerase chain reaction (interrepeat PCR). 31 A. baumannii isolates obtained from 15 ICU patients were characterized. All patients were infected or colonized with A. baumannii. After identification of the outbreak, 6 environmental isolates were collected from tap-water, sinks and cleaning detergents. PCR fingerprinting identified 3 genotypes among the outbreak-related strains. One predominant genotype was demonstrated in 14/15 patients and this genotype was also found among all environmental isolates. The cluster of A. baumannii represented an outbreak of 1 genotype, suggesting cross-contamination. The finding of the identical genotype among all environmental strains indicated a common environmental source causing the outbreak. The outbreak was controlled after reimplementation of an effective disinfection of workplace surfaces. This survey proved interrepeat PCR to be a rapid and reliable method to differentiate A. baumannii strains, thereby allowing epidemiological surveillance of large amounts of strains and early interventions to control outbreaks.

Epidemiological survey of an outbreak of multiresistant Serratia marcescens by PCR-fingerprinting

During an outbreak of Serratia marcescens from May to November 1993 43 strains obtained from 27 ICU patients infected or colonized with multiresistant S. marcescens were genotypically characterized with random amplified polymerase chain reaction (RAPD-PCR)-fingerprinting. In addition, 43 epidemiologically unrelated control isolates were selected. PCR-fingerprinting identified ten different genotypes of S. marcescens among the outbreak related strains. One predominant genotype was demonstrated in 21/43 isolates of 11/27 patients. A cluster of this genotype was found in seven/eight patients on the cardiosurgical ICU. The epidemiologically unrelated strains all showed different genotypes as compared to the predominant type. This survey proved RAPD-PCR to be a highly discriminatory and reproducible method for epidemiological studies of S. marcescens strains in nosocomial outbreaks.