Multiply-resistant Klebsiella pneumoniae: failure of spread in community-based elderly care facilities

Extended-spectrum beta-lactamase--producing enterobacteriaceae in the intensive care unit: acquisition does not mean cross-transmission

Background

In intensive care unit (ICU), infection and colonization by resistant Gram-negative bacteria increase costs, length of stay and mortality. Extended-spectrum beta-lactamase − producing Enterobacteriaceae (ESBL-E) is a group of pathogens increasingly encountered in ICU setting. Conditions that promote ESBL-E acquisition are not completely understood. The increasing incidence of infections related to ESBL-E and the unsolved issues related to ESBL-E cross-transmission, prompted us to assess the rates of referred and acquired cases of ESBL-E in ICU and to assess patient-to-patient cross-transmission of ESBL-E using a multimodal microbiological analysis.

Methods

During a 5-month period, all patients admitted to a medical ICU were tested for ESBL-E carriage. A rectal swab was performed at admission and then twice a week until discharge or death. ESBL-E strains were analyzed according to antibiotic susceptibility pattern, rep-PCR (repetitive-element Polymerase chain reaction) chromosomal analysis, and plasmid PCR (Polymerase chain reaction) analysis of ESBL genes. Patient-to-patient transmission was deemed likely when 2 identical strains were found in 2 patients hospitalized simultaneously in the ICU.

Results

Among the 309 patients assessed for ESBL-E carriage on admission, 25 were found to carry ESBL-E (importation rate: 8 %). During follow-up, acquisition was observed among 19 of them (acquisition rate: 6.5 %). Using the multimodal microbiological approach, we found only one case of likely patient-to-patient ESBL-E transmission.

Conclusions

In unselected ICU patients, we found rather low rates of ESBL-E referred and acquired cases. Only 5 % of acquisitions appeared to be related to patient-to-patient transmission. These data highlight the importance of jointly analyzing phenotypic profile and molecular data to discriminate strains of ESBL-E.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1489-z) contains supplementary material, which is available to authorized users.

Controversies in guidelines for the control of multidrug-resistant Gram-negative bacteria in EU countries

The various guidelines that are available for multidrug-resistant Gram-negative bacteria are useful, and contain broad areas of agreement. However, there are also important areas of controversy between the guidelines in terms of the details of applying contact precautions, single-room isolation and active surveillance cultures, differences in the approach to environmental cleaning and disinfection, and whether or not to perform staff and patient cohorting, healthcare worker screening or patient decolonization. The evidence-base is extremely limited and further research is urgently required to inform an evidence-based approach to multidrug-resistant Gram-negative bacteria prevention and control.

What Infection Control Interventions Should Be Undertaken to Control Multidrug-Resistant Gram-Negative Bacteria?

Multidrug-resistant gram-negative bacteria are an emerging problem. The present article addresses 2 relevant questions: (1) should active surveillance be performed to identify patients colonized with multidrug-resistant gram-negative bacteria, and (2) should contact isolation precautions be taken with patients colonized or infected with multidrug-resistant gram-negative bacteria? Data and variables that are needed to scientifically answer these questions are reviewed, as are existing data on Pseudomonas aeruginosa, Enterobacteriaceae (Escherichia coli and Klebsiella species in particular), and Acinetobacter baumannii.

Extended-spectrum beta-lactamases: a clinical update

Extended-spectrum beta-lactamases (ESBLs) are a rapidly evolving group of beta-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these beta-lactamases. This extends the spectrum of beta-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

Antibiotic resistance rates and phenotypes among isolates of Enterobacteriaceae in French extra-hospital practice

Antibiotic resistance among members of the family Enterobacteriaceae was prospectively surveyed by eight French private laboratories over a 5-month period in 1999. A total of 2,599 consecutive and nonduplicate strains were collected, mainly (60.9%) from patients in the community. Most strains (82.9%) derived from urine. Escherichia coli was the predominant (73.9%) organism isolated. The overall rates of antibiotic resistance were as follows: amoxicillin, 53.4%; amoxicillin-clavulanic acid, 27.3%; ticarcillin, 44.2%; piperacillin-tazobactam, 3.2%; cephalothin, 29.2%; cefuroxime, 14.7%; cefoxitin, 11.5%; ceftazidime, 3.6%; cefotaxime, 2.8%; cefepime, 0.3%; imipenem, 0.1%; gentamicin (G), 3.8%; tobramycin (T), 5.0%; netilmicin (Nt), 3.7%; amikacin (A), 0.7%; nalidixic acid, 14.3%; ofloxacin, 10.4%; cotrimoxazole, 21.1%; nitrofurantoin, 12.7%; fosfomycin, 5.2%; tetracycline, 50.1%; and colistin, 12.5%. Beta-lactam resistance phenotypes essentially comprised penicillinase production (33.9%), overexpression of chromosomal cephalosporinase (4.6%), and synthesis of inhibitor-resistant TEM/OXA enzymes (1.5%) or extended-spectrum beta-lactamases (1.5%). Aminoglycoside resistance phenotypes consisted of GTNt (93 strains), TNtA (68 strains), GTNtA (14 strains), T (4 strains), GT (3 strains), G (1 strain), and reduced uptake/permeability (3 strains). Most of the nalidixic acid-resistant strains were resistant to ofloxacin (72.8%). Antibiotic resistance rates and phenotypes varied widely according to the bacterial group and the source of the strains. Significantly higher rates were observed in private healthcare centers than in the community, due to a higher proportion of both resistant species and resistant strains. However, multidrug-resistant isolates, including five extended-spectrum beta-lactamase-producing strains, were also recovered from the community.

Comparison of screening methods for TEM- and SHV-derived extended-spectrum beta-lactamase detection

OBJECTIVE

To compare common extended-spectrum beta-lactamase (ESBL) screening methods and beta-lactams for their ability to detect TEM- and SHV-related ESBL enzymes.

METHODS

This study compared disk diffusion testing by NCCLS methodology, the Jarlier double disk test, a disk-on-disk test, a modified three-dimensional test and the E test method for their sensitivity and specificity in detecting TEM- and SHV-related ESBL producers. Three negative and 22 positive controls were studied. These were two Klebsiella pneumoniae and 23 Escherichia coli transconjugants. Seventeen beta-lactam antibiotics were tested: cefamandole, cefotetan, cefoxitin, cefuroxime, cefixime, cefoperazone, cefotaxime, cefpodoxime, cefsulodin, ceftazidime, ceftibuten, ceftizoxime, ceftriaxone, moxalactam, cefepime, cefpirome and aztreonam.

RESULTS

NCCLS disk diffusion was 14% sensitive with ceftriaxone, 36% with cefotaxime, 64% with aztreonam, 68% with cefpodoxime, and 73% with ceftazidime. Cefoperazone, cefamandole, cefpodoxime and cefpirome showed 91% sensitivity using the Jarlier test. Using the disk-on-disk test, cefsulodin showed 95% sensitivity, and cefoperazone, cefepime and cefamandole showed 91% sensitivity. With the modified three-dimensional test, cefoperazone, cefpodoxime and cefpirome showed 91% sensitivity.

CONCLUSIONS

For practical reasons, we would recommend use of either the Jarlier test or the commercial cephalosporin disks containing clavulanic acid to screen for ESBL producers. Cefoperazone, cefamandole, cefpodoxime and cefpirome showed good sensitivity across the methods tested.

Long-term care facilities as sources of antibiotic-resistant nosocomial pathogens

Long-term care facilities house individuals that have usually been transferred from acute-care institutions. For this reason, carriage of methicillin-resistant Staphylococcus aureus (MRSA), resistant Gram-negative bacilli and vancomycin-resistant enterococci (VRE) is relatively frequent. As these patients are readmitted to acute-care institutions, they reintroduce these organisms into those settings. It is notable that studies of these resistant organisms in long-term care facilities demonstrate little transfer between patients. Transmission of these bacteria and the development of infection in nursing homes are both uncommon events. Resources are best devoted to infection-control basics than to isolation of patients colonized or infected with these organisms.

Molecular epidemiology of an outbreak due to IRT-2 beta-lactamase-producing strains of Klebsiella pneumoniae in a geriatric department

In February 1998, 195 patients in the geriatric department of a French hospital were screened for the presence of co-amoxiclav-resistant Klebsiella pneumoniae. Eleven co-amoxiclav-resistant isolates obtained all produced an identical IRT-2 beta-lactamase. These K. pneumoniae isolates were clonally related and harboured a c. 55 kb non-conjugative plasmid encoding a non-class-1 integron-located blaIRT-2 gene. This study underlines that geriatric departments may be a reservoir for antibiotic-resistant strains and that IRT beta-lactamase-producing strains may be nosocomial pathogens.