A simultaneous outbreak on a neonatal unit of two strains of multiply antibiotic resistant Klebsiella pneumoniae controllable only by ward closure

Hospital-Based Strategies for Combating Resistance

Selective pressures generated by the indiscriminate use of beta-lactam antibiotics have resulted in increased bacterial resistance across all beta-lactams classes. In particular, the use of third-generation cephalosporins has been associated with the emergence of extended-spectrum beta-lactamase-producing and AmpC beta-lactamase-producing Enterobacteriaceae and vancomycin-resistant enterococci. Conversely, beta-lactams (e.g., cefepime, piperacillin-tazobactam, and ampicillin-sulbactam) have not demonstrated such strong selective pressures. Chief among institutional strategies to control outbreaks of multidrug-resistant bacteria are infection-control measures and interventional programs designed to minimize the use of antimicrobial agents that are associated with strong relationships between use and resistance. Successful programs include antimicrobial stewardship programs (prospective audit and feedback), formulary interventions (therapeutic substitutions), formulary restrictions, and vigilant infection control. Fourth-generation cephalosporins, such as cefepime, have proven to be useful substitutes for third-generation cephalosporins, as a part of an overall strategy to minimize the selection and impact of antimicrobial-resistant organisms in hospital settings.

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.

Clinical features of nosocomial infections by extended-spectrum beta-lactamase-producing Enterobacteriaceae in neonatal intensive care units

AIM

To determine the risk factors for the acquisition of nosocomial extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae infection in infants hospitalized in neonatal intensive care units (NICUs) and to evaluate the therapeutic outcome of these infants.

METHODS

We retrospectively reviewed the medical records of infants with nosocomial ESBL-producing Enterobacteriaceae infection hospitalized in NICUs at Chang Gung Children's Hospital in 2001. The clinical features of these infants were compared with a cohort of non-ESBL-producing Enterobacteriaceae-infected infants during the same period. The therapeutic outcome of the infants in the ESBL group was analysed.

RESULTS

Seventy infants were included in this study. Thirty-one infants with 34 isolates were identified in the ESBL group and 39 infants with 42 isolates in the non-ESBL group. Of the parameters analysed, including gestational age, birthweight, length of hospital stay before onset, the number of antibiotics used, the duration of third-generation cephalosporin usage and the number of patients receiving a third-generation cephalosporin prior to the onset of infection, no significant difference was found between the two groups. The infection-contributed case fatality rate was 3.0% (1 of 33) in the ESBL group, not significantly different from that in the non-ESBL group (1 of 41, 2.4%). Of the 31 patients in the ESBL group, 18 were treated with a carbapenem as definitive therapy while 13 were treated with a non-carbapenem antibiotic regimen. No significant difference was noted in terms of mortality rate between the two subgroups.

CONCLUSION

The outcome of the infants hospitalized in the NICU with ESBL-producing enterobacterial infections was not indispensably grave, even when treated with a non-carbapenem antibiotic regimen. The risk factors for the acquisition of ESBL-producing enterobacterial infections in these infants were not identified in this series.

A simultaneous outbreak of Serratia marcescens and Klebsiella pneumoniae in a neonatal intensive care unit

We describe two concurrent outbreaks of Serratia marcescens and Klebsiella pneumoniae in a neonatal intensive care unit (NICU). Over a 16-month period, a total of 27 infants were either colonized (N=14) or infected (N=13). There were 15 cases of S. marcescens and 11 cases of K. pneumoniae. Both micro-organisms were involved in one fatal case. Seven preterm babies developed septicaemia, two had bacteraemia, three had respiratory infections and one had purulent conjunctivitis. The S. marcescens and K. pneumoniae isolates were investigated by three molecular methods: enterobacterial repetitive intergenic consensus polymerase chain reaction (PCR), arbitrary primed PCR with M13 primer, and random amplification of polymorphic DNA. Different patterns were found in the 16 S. marcescens epidemic isolates from 16 newborn infants. The major epidemic-involved genotype was linked to the first nine cases and this was subsequently replaced by different patterns. Eight different typing profiles were also determined for the 13 K. pneumoniae isolates from 12 newborn infants. Four K. pneumoniae bacteraemic strains proved to be identical. In conclusion, the typing results revealed that two different micro-organisms (S. marcescens and K. pneumoniae) were simultaneously involved in invasive nosocomial infections in preterm newborns. Two simultaneous clusters of cases were documented. Heterogeneous genotypes among both species were also demonstrated to be present in the NICU at the same time. A focal source for both micro-organisms was not identified but cross-transmission through handling was probably an important route in this outbreak. Strict adherence to handwashing policies, cohorting, isolation of colonized and infected patients, and rigorous environmental hygiene were crucial measures in the containment of the epidemic.

Changes in antibiotic resistance of the most common Gram-negative bacteria isolated in intensive care units

We studied the changes in antibiotic resistance of the most common Gram-negative bacteria isolated in the intensive care units at our hospital in 2000 and 2002. Bacterial identification was performed by use of the VITEK 60 analyser, and antibiotic susceptibilities were tested by the VITEK 60 analyser and the disk diffusion agar method. The bacteria isolated most frequently were Pseudomonas aeruginosa (132 strains in 2000 and 106 in 2002), Acinetobacter calcoaceticus (98 and 109 strains, respectively) and Klebsiella pneumoniae (53 and 83 strains, respectively). Acinetobacters presented the highest percentage resistance, with significant increases in resistance to imipenem (15% in 2000 and 67% in 2002) and piperacillin/tazobactam (41% and 72%, respectively). P. aeruginosa presented a significant increase in resistance to all antibiotics, except ceftazidime. A large increase was observed in the resistance of K. pneumoniae to amikacin (from 10% to 50%), ceftazidime (from 80% to 90%) and tobramycin (from 80% to 90%). No imipenem-resistant strains of K. pneumoniae were found.

Genetic Relatedness among Extended-Spectrum β-Lactamase-ProducingKlebsiella pneumoniaeOutbreak Isolates Associated with Colonization and Invasive Disease in a Neonatal Intensive Care Unit

Pulsed-field gel electrophoresis typing of 60 extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBLKp) isolates obtained in a neonatal intensive care unit during an outbreak indicated the dissemination of two major bacterial genotypes associated with colonization and invasive disease: one composed by aminoglycoside-resistant isolates and the other by aminoglycoside-susceptible isolates. A urease-negative phenotype was observed among aminoglycoside-resistant ESBLKp. Six pairs of isolates from gastrointestinal (GI) colonization and isolates from invasive disease that occurred 3-23 days later were shown to belong to the same genotype, reinforcing a direct association between colonization and subsequent disease. These data indicate that screening for ESBLKp GI colonization in an outbreak setting may be useful to detect neonates at a higher risk of invasive disease.

Risk factors for colonization and infection in a hospital outbreak caused by a strain of Klebsiella pneumoniae with reduced susceptibility to expanded-spectrum cephalosporins

Between February 2001 and January 2002, an increase in the number of Klebsiella pneumoniae isolates with reduced susceptibility to expanded-spectrum cephalosporins (RSKp) was detected in the neonatal unit of the Juan Canalejo Hospital, and 21 patients were either colonized or infected by the bacterial isolates. The current "gold standard" method for typing K. pneumoniae isolates is pulsed-field gel electrophoresis. However, this technique is expensive and time-consuming. In a search for faster and accurate alternatives to this method, we investigated PCR-based fingerprinting techniques (enterobacterial repetitive intergenic consensus sequence PCR [ERIC-PCR], repetitive extragenic palindromic sequence-based PCR [REP-PCR], and RAPD [randomly amplified polymorphic DNA]) for their ability to characterize K. pneumoniae isolates. The causal agent of the nosocomial outbreak was characterized by these techniques and was found to be a single epidemic strain (RSKp). A multiple regression logistic model was developed to identify potential independent factors associated with colonization and/or infection by RSKp. Logistic regression analysis was applied to all significant variables (P < 0.05) in the univariate analysis, and it was revealed that intubation (odds ratio [OR], 27.0; 95% confidence interval [95%CI], 5.39 to 135.14) and prematurity (OR, 4.4; 95%CI, 0.89 to 21.89) were such independent factors. Moreover, oxime cephalosporins did not appear to be statistically significant. Overall, the results showed that PCR-based techniques are expeditious and useful methods for typing K. pneumoniae isolates. Of the techniques studied, ERIC-PCR showed the highest discriminatory index (D = 0.828), followed by RAPD (D = 0.826) and REP-PCR (D = 0.773)

Antibiotic-resistant infections in the critically ill adult

Intensive care units (ICUs) frequently are the epicenter of nosocomial infections with antibiotic-resistant bacteria. Optimization of antibiotic therapy for seriously ill patients with bacterial infections appears to have a strong influence on outcome. Laboratories can aid in provision of appropriate antibiotic therapy by providing clinicians with "antibiograms" to aid empiric antibiotic choice and by providing minimal inhibitory concentrations of key antibiotics so that antibiotic dosing is optimized to key pharmacodynamic targets. Laboratories also play a crucial role in the prevention of antibiotic resistance in the ICU. Molecular epidemiologic evidence of an oligoclonal outbreak of infections orients prevention measures toward investigation of common environmental sources of infection and prevention of patient-to-patient transmission. In contrast, evidence of polyclonality shifts prevention of antibiotic resistance to antibiotic management strategies.

Antibiotic-resistant gram-negative bacteria in hospitalized children

Antibiotic-resistant Gram-negative bacilli are a prominent and growing problem among hospitalized children. Epidemics caused by these organisms have been implicated in many outbreaks in children's hospitals, primarily in neonatal intensive care units. These epidemics are characterized by efficient patient-to-patient transmission of the outbreak clone via the hands of caregivers and through exposure of contaminated inanimate sources. The epidemiology of these resistant organisms in pediatric hospitals during endemic periods is more complex. The isolates cultured from hospitalized individuals in the absence of an outbreak usually are unique to each individual and are derived from the patient's endogenous flora or other disparate sources. As in adults, chronic care facilities for children represent significant reservoirs of antibiotic-resistant bacilli that are circulated back into the acute care hospital environment when the child becomes ill.

Outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a neonatal intensive care unit linked to artificial nails

BACKGROUND

From April to June 2001, an outbreak of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae infections was investigated in our neonatal intensive care unit.

METHODS

Cultures of the gastrointestinal tracts of patients, the hands of healthcare workers (HCWs), and the environment were performed to detect potential reservoirs for ESBL-producing K. pneumoniae. Strains of K. pneumoniae were typed by pulsed-field gel electrophoresis using XbaI. A case-control study was performed to determine risk factors for acquisition of the outbreak clone (clone A); cases were infants infected or colonized with clone A and controls (3 per case) were infants with negative surveillance cultures.

RESULTS

During the study period, 19 case-infants, of whom 13 were detected by surveillance cultures, harbored clone A. The overall attack rate for the outbreak strain was 45%; 9 of 19 infants presented with invasive disease (n = 6) or developed invasive disease (n = 3) after colonization was detected. Clone A was found on the hands of 2 HCWs, 1 of whom wore artificial nails, and on the designated stethoscope of a case-infant. Multiple logistic regression analysis revealed that length of stay per day (odds ratio [OR], 1.05; 95% confidence interval [CI95], 1.02 to 1.09) and exposure to the HCW wearing artificial fingernails (OR, 7.87; CI95, 1.75 to 35.36) were associated with infection or colonization with clone A.

CONCLUSION

Short, well-groomed, natural nails should be mandatory for HCWs with direct patient contact

Descriptive and molecular epidemiology of Gram-negative bacilli infections in the neonatal intensive care unit

PURPOSE OF REVIEW

The critically ill neonate is particularly prone to life threatening bacterial infections compared with other patient populations. Current patterns of neonatal sepsis caused by Gram-negative bacilli are reviewed to enable the clinician to better anticipate and effectively respond to neonatal infection by these serious pathogens.

RECENT FINDINGS

With increasing use of intrapartum antibiotics for prophylaxis against early-onset group B streptococcal infection, there is growing concern that the incidence of neonatal sepsis by Gram-negative pathogens may rise. Although several surveys indicate no such increase to date, studies in selected neonatal intensive care unit populations have suggested a recent elevation in newborn infection caused by Escherichia coli and other bacillary pathogens. Most recent investigations reveal growing antibiotic resistance in those Gram-negative bacilli causing neonatal infection. Modern molecular genotyping methods have been applied to Gram-negative bacilli in the neonatal intensive care unit in order to understand their epidemiology in greater detail. In most instances these techniques have been used to identify the sources and prevalence of an outbreak strain, and to devise rational interventions to control the epidemic. Studies utilizing molecular genotyping during non-outbreak periods indicate that Gram-negative bacilli, even those expressing antibiotic resistance, may be acquired very early in the intensive care unit course, and that different clones are introduced and lost in the infants' indigenous flora throughout their stay. These studies further indicate that cross-transmission of bacillary pathogens occurs regularly even in the absence of a recognized epidemic.

SUMMARY

Gram-negative bacilli are prominent causes of infection in the neonatal intensive care unit. Their incidence, antibiotic susceptibility pattern, and modes of acquisition continue to evolve in the modern intensive care unit setting.

A seven-year survey of Klebsiella pneumoniae producing TEM-24 extended-spectrum beta-lactamase in Nice University Hospital (1994-2000)

The aim of this study was to investigate TEM-24-producing isolates of Klebsiella pneumoniae, and their clonal dissemination in Nice University Hospital. During the 1994-2000 period, a total of 263 non-repetitive isolates of ESBL-producing K. pneumoniae were collected. Most of these isolates were highly resistant in vitro to ceftazidime, cefotaxime and aztreonam, but susceptible to cefoxitin and imipenem. Resistance profile analysis revealed seven predominant antibiotypes (P1 to P7). Isoelectric focusing evidenced beta-lactamase activity, with a chromosomal penicillinase (pl 7.7), and one or two additional enzymes with pls ranging from 5.4 to 8.2 identified as presumed TEM-1 pl 5.4, TEM-3 pl 6.3, TEM-24 pl 6.5, SHV-3 pl 7.0, SHV-4 pl 7.8, SHV-5 pl 8.2, or other unidentified beta-lactamases. Among these K. pneumoniae, 130 isolates produced TEM-24, and 115 of them were highly resistant in vitro to quinolones (antibiotype P1). This phenotype was responsible for an outbreak in a medical intensive care unit from March to September 2000. Four isolates submitted were genetical sequenced, and shared 99.9% homology with tem-24 (GenBank no. X 65253). Pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus polymerase chain reaction (PCR) (ERIC2-PCR) applied to 28 non-epidemic and six epidemic isolates yielded concordant results. Molecular typing revealed the persistence and dissemination of a single clone of TEM-24 producing K. pneumoniae in Nice Hospital during the seven-year study period.

Extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae: considerations for diagnosis, prevention and drug treatment

Extended spectrum beta-lactamase (ESBL)-producing organisms pose unique challenges to clinical microbiologists, clinicians, infection control professionals and antibacterial-discovery scientists. ESBLs are enzymes capable of hydrolysing penicillins, broad-spectrum cephalosporins and monobactams, and are generally derived from TEM and SHV-type enzymes. ESBLs are often located on plasmids that are transferable from strain to strain and between bacterial species. Although the prevalence of ESBLs is not known, it is clearly increasing, and in many parts of the world 10-40% of strains of Escherichia coli and Klebsiella pneumoniae express ESBLs. ESBL-producing Enterobacteriaceae have been responsible for numerous outbreaks of infection throughout the world and pose challenging infection control issues. Clinical outcomes data indicate that ESBLs are clinically significant and, when detected, indicate the need for the use of appropriate antibacterial agents. Unfortunately, the laboratory detection of ESBLs can be complex and, at times, misleading. Antibacterial choice is often complicated by multi-resistance. Many ESBL-producing organisms also express AmpC beta-lactamases and may be co-transferred with plasmids mediating aminoglycoside resistance. In addition, there is an increasing association between ESBL production and fluoroquinolone resistance. Although in in vitro tests ESBLs are inhibited by beta-lactamase inhibitors such as clavulanic acid, the activity of beta-lactam/beta-lactamase inhibitor combination agents is influenced by the bacterial inoculum, dose administration regimen and specific type of ESBL present. Currently, carbapenems are regarded as the drugs of choice for treatment of infections caused by ESBL-producing organisms. Unfortunately, use of carbapenems has been associated with the emergence of carbapenem-resistant bacterial species such as Stenotrophomonas sp. or Pseudomonas sp.

Hospital-acquired infections in the neonatal intensive care unit--Klebsiella pneumoniae

Klebsiella pneumoniae is medically the most important organism of the Klebsiella species. It is responsible for a significant proportion of hospital-acquired infections including septicemias, urinary tract infections, pneumonia, and soft tissue infections especially in the immunocompromised hosts such as the neonate. The hands of healthcare workers and the gastrointestinal tract of hospitalized infants serve as reservoirs for the transmission of the organism and are responsible for multiple hospital outbreaks. In recent years, there has been an increase in the incidence of outbreaks caused by multidrug resistance K. pneumoniae organisms or the extended spectrum beta-lactamase (ESBL)-producing K. pneumoniae. The problems associated with extended spectrum beta-lactamase-producing organisms include difficulties in accurate antimicrobial susceptibility testing, limited treatment options and increased morbidity and perhaps mortality. Hence, prevention through implementation of strict infection control guidelines, effective hand washing and judicious use of antimicrobials such as third generation cephalosporins is important to effectively reduce the morbidity associated with this infection.