Outbreak of cephalosporin resistant Enterobacter cloacae infection in a neonatal intensive care unit

Practice Summary of Antimicrobial Therapy for Commonly Encountered Conditions in the Neonatal Intensive Care Unit: A Canadian Perspective

Neonates are highly susceptible to infections owing to their immature cellular and humoral immune functions, as well the need for invasive devices. There is a wide practice variation in the choice and duration of antimicrobial treatment, even for relatively common conditions in the NICU, attributed to the lack of evidence-based guidelines. Early decisive treatment with broad-spectrum antimicrobials is the preferred clinical choice for treating sick infants with possible bacterial infection. Prolonged antimicrobial exposure among infants without clear indications has been associated with adverse neonatal outcomes and increased drug resistance. Herein, we review and summarize the best practices from the existing literature regarding antimicrobial use in commonly encountered conditions in neonates.

Spectrum of uropathogens and their susceptibility to antimicrobials in pregnant women: a retrospective analysis of 5-year hospital data

OBJECTIVE

Urinary tract infections (UTI) are common during pregnancy. Identification of antimicrobial susceptibility patterns of microorganisms in pregnant women is important to select the most appropriate antimicrobial. We assessed common uropathogens in pregnant women with UTI and antimicrobial susceptibility, to guide empirical antibiotic selection.

METHODS

In this retrospective study, we analyzed mid-stream urine culture and antibiotic susceptibility data from pregnant women who attended Jordan University Hospital during 2014 to 2018. Data were collected from patients' charts and urine cultures, and sensitivity results were extracted from the laboratory electronic system. We calculated descriptive statistics and determined correlations among pathogens and antibiotics.

RESULTS

We examined 612 positive urine cultures from 559 pregnant women, including 163 (29.2%) inpatients. Escherichia coli (29.4%) was the most frequently identified microorganism, followed by coagulase-negative staphylococci (CoNS) (21.6%). All bacterial isolates were sensitive to aztreonam, chloramphenicol, fosfomycin, ofloxacin, pefloxacin, piperacillin, and colistin sulfate; 87.5% were sensitive to amikacin. Only 15.79%, 18.93%, and 17.91% were sensitive to oxacillin, nalidixic acid, and erythromycin, respectively.

CONCLUSION

E. coli and CoNS were the most commonly identified microorganisms in this study. We found increased antibiotic resistance in Enterobacter species. The chosen antimicrobial therapy in pregnancy should be determined by sensitivity/resistance and fetomaternal safety.

Outbreak of Extended-Spectrum Beta-Lactamase Producing Enterobacter cloacae with High MICs of Quaternary Ammonium Compounds in a Hematology Ward Associated with Contaminated Sinks

Objective: To investigate an outbreak of extended-spectrum beta-lactamase (ESBL) producing Enterobacter cloacae that occurred in the Hematology ward (24-bed unit) of the François Mitterrand University Hospital (Dijon, France) between January 2011 and December 2013. The outbreak involved 43 patients (10 infected and 33 colonized).

Design: We performed environmental analysis to detect multiresistant E. cloacae for comparison with clinical isolates (genotyping by pulsed-field gel electrophoresis and MLST as well as ESBL-typing) and determined the MICs of the quaternary ammonium compounds (QACs) alkyldimethylbenzylammonium chloride (ADBAC) and didecyldimethylammonium chloride (DDAC). A bleach-based cleaning-disinfection program was implemented in December 2012 after mechanical removal of the biofilm in all sinks.

Results: We have detected 17 ESBL-producing E. cloacae in patients sink drains, shower drains and medical sink drains. Sequencing of the bla genes performed on 60 strains recovered from patients and environment (n = 43 clinical and n = 17 environmental) revealed that bla_CTX−M15 was predominant (37 isolates) followed by bla_CTX−M9 plus bla_SHV−12 (20 isolates). We observed a great diversity among the isolates: 14 pulsotypes (11 STs) in clinical isolates and 9 pulsotypes (7 STs) in environmental isolates. Six pulsotypes were identical between clinical and environmental isolates. MICs of the quaternary ammonium compounds widely used for disinfection were very high in clinical and environmental isolates. Immediately after the implementation of the disinfection program we noticed a substantial fall in cases number. Our findings demonstrate the role of drains as important reservoir of ESBL-producing E. cloacae and highlight the necessity to settle drains accessible to achieve correct cleaning as well as to use disinfectant with proved activity against nosocomial pathogens.

Use of ward closure to control outbreaks among hospitalized patients in acute care settings: a systematic review

BACKGROUND

Though often used to control outbreaks, the efficacy of ward closure is unclear. This systematic review sought to identify studies defining and describing ward closure in outbreak control and to determine impact of ward closure as an intervention on outbreak containment.

METHODS

We searched these databases with no language restrictions: MEDLINE, 1946 to 7 July 2014; EMBASE, 1974 to 7 July 2014; CINAHL, 1937 to 8 July 2014; and Cochrane Database of Systematic Reviews, 2005 to May 2014. We also searched the following: IndMED; LILACS; reference lists from retrieved articles; conference proceedings; and websites of the CDCP, the ICID, and the WHO. We included studies of patients hospitalized in acute care facilities; used ward closure as a control measure; used other control measures; and discussed control of the outbreak(s) under investigation. A component approach was used to assess study quality.

RESULTS

We included 97 English and non-English observational studies. None included a controlled comparison between ward closure and other interventions. We found that ward closure was often used as part of a bundle of interventions but could not determine its direct impact separate from all the other interventions whether used in parallel or in sequence with other interventions. We also found no universal definition of ward closure which was widely accepted.

CONCLUSIONS

With no published controlled studies identified, ward closure for control of outbreaks remains an intervention that is not evidence based and healthcare personnel will need to continue to balance the competing risks associated with its use, taking into consideration the nature of the outbreak, the type of pathogen and its virulence, mode of transmission, and the setting in which it occurs. Our review has identified a major research gap in this area.

Antibiotics and Antifungals in Neonatal Intensive Care Units: A Review

The incidence of infections is higher in the neonatal period than at any time of life. The basic treatment of infants with infection has not changed substantially over the last years. Antibiotics (with or without supportive care) are one of the most valuable resources in managing sick newborn babies. Early-onset (ascending or transplacental) or late-onset (hospital acquired) infections present different chronology, epidemiology, physiology and outcome. Some classes of antibiotics are frequently used in the neonatal period: penicillins, cephalosporins, aminoglycosides, glycopeptides, monobactams, carbapenems. Other classes of antibiotics (chloramphenicol, cotrimoxazole, macrolides, clindamycin, rifampicin and metronidazole) are rarely used. Due to emergence of resistant bacterial strains in Neonatal Intensive Care Units (NICU), other classes of antibiotics such as quinolones and linezolid will probably increase their therapeutic role in the future. Although new formulations have been developed for treatment of fungal infections in infants, amphotericin B remains first-line treatment for systemic Candida infection. Prophylactic antibiotic therapy is almost always undesirable. Challenges from pathogens and antibiotic resistance in the NICU may warrant modification of traditional antibiotic regimens. Knowledge of local flora and practical application of different antibiotic characteristics are key to an effective and safe utilization of antibiotics and antifungals in critical newborns admitted to the NICU, and especially in very low birth weight infants.

Clinical analysis of Enterobacter bacteremia in pediatric patients: a 10-year study

BACKGROUND

Enterobacter species has emerged as an important pathogen of nosocomial bacteremia. The purpose of this study is to review the clinical characteristics of bacteremia in pediatric patients.

MATERIALS AND METHODS

We reviewed retrospectively the medical records of patients (under the age of 18 years) having Enterobacter bacteremia who were treated at Taipei the Veterans General Hospital from January 2001 to June 2011.

RESULTS

In total, 853 positive blood cultures were obtained from 620 patients during the study period. Among them, 96 episodes of Enterobacter bacteremia were found in 83 patients, accounting for 11.3% of all bacteremia. Eighty-two cases (98.8%) were nosocomial infections. Most of the cases were neonates (62 cases, 74.7%) and premature infants (51 cases, 61.5%). The common sources of bacteremia were the respiratory tract (53.0%), followed by intravascular catheter (10.8%), multiple sources (10.8%), and the gastrointestinal tract (8.4%). The overall case fatality rate was 18.1%, with the highest rate being reported among premature infants. The factors responsible for the deaths were leukocytosis and a higher median number of underlying diseases.

CONCLUSION

Based on the findings of the present study, it can be concluded that Enterobacter species are probably an important pathogen of nosocomial bacteremia in premature neonates. The number of underlying diseases should be considered a major factor influencing the prognosis.

Subtractive hybridization yields a silver resistance determinant unique to nosocomial pathogens in the Enterobacter cloacae complex

The heterogeneity and the increasing clinical importance of the Enterobacter cloacae complex have often been discussed. However, little is known about molecular factors causing pathogenicity within this nomenspecies. Here, we analyzed the genetic differences between an avirulent plant isolate and a pathogenic strain causing an outbreak with septicemia in three patients. We identified an IncHI-2 plasmid as a major difference between these two strains. Besides resistance to several antibiotics, this plasmid encoded a silver resistance determinant. We further showed that this sil determinant was present not only in the analyzed outbreak strain but also in the vast majority of clinical isolates of the E. cloacae complex, predominantly in (sub)species that frequently cause nosocomial infections. The identified sil determinant was highly conserved within the E. cloacae complex and mediated resistance to up to 600 μM silver nitrate. As silver is often used as a disinfectant and treatment for burn wounds, we present here an important fitness factor within the clinically most prevalent subspecies of the E. cloacae complex. This provides a possible explanation for their unequal involvement in nosocomial and especially burn wound infections.

High load of multi-drug resistant nosocomial neonatal pathogens carried by cockroaches in a neonatal intensive care unit at Tikur Anbessa specialized hospital, Addis Ababa, Ethiopia

BACKGROUND

Cockroaches have been described as potential vectors for various pathogens for decades; although studies from neonatal intensive care units are scarce. This study assessed the vector potential of cockroaches (identified as Blatella germanica) in a neonatal intensive care unit setup in Tikur Anbessa Hospital, Addis Ababa, Ethiopia.

METHODS

A total of 400 Blatella germanica roaches were aseptically collected for five consecutive months. Standard laboratory procedures were used to process the samples.

RESULTS

From the external and gut homogenates, Klebsiella oxytoca, Klebsiella pneumoniae, Citrobacter spp. Enterobacter cloacae, Citrobacter diversus, Pseudomonas aeruginosa, Providencia rettgeri, Klebsiella ozaenae, Enterobacter aeruginosa, Salmonella C1, Non Group A streptococcus, Staphylococcus aureus, Escherichia coli, Acinetobacter spp. and Shigella flexneri were isolated. Multi-drug resistance was seen in all organisms. Resistance to up to all the 12 antimicrobials tested was observed in different pathogens.

CONCLUSION

Cockroaches could play a vector role for nosocomial infections in a neonatal intensive care unit and environmental control measures of these vectors is required to reduce the risk of infection. A high level of drug resistance pattern of the isolated pathogens was demonstrated.

Antibiotic therapy in neonatal and pediatric septic shock

Severe sepsis accounts for nearly 4,500 deaths (mortality rate 10%), and is responsible for nearly $2 billion annual healthcare expenditure in the United States. Early and speedy treatment of critically ill septic patients can halt or reduce the likelihood of physiologic progression to multi-system organ failure. A cornerstone of this therapeutic strategy is antibiotic administration. In this review, we discuss the empirical treatment strategies for the treatment of early and late neonatal sepsis, along with pediatric sepsis. Furthermore, we discuss the rationale that underlies the adoption of such treatment strategies. The present article also discusses the emergence of multi-drug organisms as the causative agents for sepsis, i.e. methicillin-resistant Staphylococcus aureus (MRSA), resistant enterococci and Klebsiella pneumoniae carbapenemases (KPC).

Choice of antibiotics in late neonatal sepsis in the extremely low birth weight infant

OBJECTIVE

To review the choice of antibiotics in treating suspected late neonatal sepsis in infants weighing 1000 g or less in a neonatal intensive care unit.

METHODS

Retrospective review of medical records.

RESULTS

Ninety-six infants weighing 1000 g or less were admitted to the neonatal intensive care unit during the study period. Sixty-two infants survived beyond four days of life and had at least one sepsis workup done to exclude late neonatal infection. Of the 62 study patients, 42 (68%) were started on ampicillin and netilmicin (A/N) and 20 (32%) were started on vancomycin and ceftizoxime (V/C) as the antibiotics of choice, pending culture results. Of the patients started on A/N, 17 of 42 had a positive blood culture compared with 11 of 20 on V/C (40% versus 55%, P=0.40). The mean (+/-SD) birth weight of infants started on A/N was 793+/-133 g compared with a mean of 728+/-153 g in the group that received V/C (P=0.09). Seven patients died in the A/N group compared with three in the V/C group (16.7% versus 15%, P=0.84). In addition to the sepsis episode studied, before they were discharged from hospital, 21 of 42 (50%) infants in the A/N group had further workups for suspected sepsis, compared with 16 of 20 (80%) (P=0.048) infants initially given V/C.

CONCLUSIONS

Ampicillin and netilmicin is a safe antibiotic combination for neonates suspected of late sepsis. This, in turn, may be important in reducing vancomycin overuse and the potential for bacterial resistance to this antimicrobial agent.

Clinical features of neonatal sepsis caused by resistant Gram-negative bacteria

BACKGROUND

Clinical features and outcomes of neonatal sepsis caused by resistant Gram-negative bacteria are not well described in Jordan. The aim of the present study was therefore to describe microbiology and clinical features, laboratory findings and outcomes of early- and late-onset Gram-negative neonatal sepsis.

METHODS

All patients with Gram-negative bacteremia between July 2003 and June 2005 were retrospectively included. Resistance profiles, clinical features and outcomes of early and late-onset neonatal sepsis were compared.

RESULTS

A total of 79 patients (after excluding all nine cases of Gram-positive bloodstream infection (BSI) were identified as having Gram-negative BSI (25 had early-onset and 54 had late-onset neonatal sepsis). Respiratory distress, metabolic acidosis and requirement of ventilation were found in 74.7%, 40.5%, and 58.2%, respectively. Hypotension was found in 22.9% of patients. Klebsiella pneumoniae was responsible for 43 cases (54.4.2%). Klebsiella pneumoniae resistance rates to ampicillin and ceftazidime were 100% and 50%, respectively. Mortality rate was 30.9%. Forty-eight percent of deaths occurred within 3 days of sepsis. Meningitis was diagnosed in five cases. Elevated C-reactive protein (CRP) and thrombocytopenia were seen in 28% and 24% of infants with early-onset sepsis, respectively, and in 79.6%, 59.3% of infants with late-onset sepsis respectively.

CONCLUSION

Both early- and late-onset neonatal sepsis are caused by highly resistant Gram-negative bacteria. Mortality of sepsis is high. Elevated CRP and thrombocytopenia is seen more commonly in late-onset neonatal sepsis.

Enteric gram-negative bacilli bloodstream infections: 17 years' experience in a neonatal intensive care unit

OBJECTIVE

To assess the occurrence of enteric gram-negative bacilli (EGNB) bloodstream infections (BSI) in a neonatal intensive care setting during a 17-year period in which a consistent antibiotic treatment program was in place. To document infections, outbreaks, or epidemics, emergence of antibiotic resistance, clinical correlates, and outcomes of the most prevalent EGNB (Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae).

METHODS

This study analyzed demographic, clinical, and bacteriologic information from 360 infants born 1986-2002 who developed 633 blood culture-proven BSI. A total of 121 EGNB were isolated (E coli, K pneumoniae, and E cloacae). Early-onset BSI were discovered within 48 hours from birth, and late-onset BSI were those that occurred thereafter. Suspected early-onset BSI were treated with ampicillin and gentamicin, suspected late-onset BSI with vancomycin and gentamicin. Antibiotics were changed on the basis of organism antimicrobial susceptibility.

RESULTS

Early-onset BSI were noted in 52 of 21,336 (244/100,000) live births (1986-1991), 40 of 20,402 (196/100,000) live births (1992-1997), and 25 of 17,926 (139/100,000) live births (1998-2002). Of these cases, 39 were caused by E coli and 4 by K pneumoniae. Antibiograms for E coli isolated during the last 5 years of the study showed an increase in antibiotic resistance that coincided with obstetric group B streptococcus antepartum antibiotic prophylaxis. Group B streptococcus declined from 41 to 4 cases from the first to the last period. Late-onset BSI increased from 111 to 230 cases from the first to the second 6-year study period and declined modestly (171 cases) during the last. Fifteen percent (78 cases) of late-onset BSI were caused by EGNB, 5% by other gram-negative bacilli, 67% primarily by coagulase-negative staphylococcus, and 13% by fungus. Nonspecific clinical and hematologic signs of late-onset BSI were similar across EGNB species, but necrotizing enterocolitis was often associated with E coli, whereas pneumonia and prolonged thrombocytopenia characterized K pneumoniae infections. No outbreaks or epidemics were observed, and strains of EGNB with evidence of extended spectrum beta-lactamase production were never isolated.

CONCLUSION

Antepartum antibiotic prophylaxis may have increased antibiotic resistance in E coli isolates from early-onset BSI but has dramatically decreased group B streptococcus infections. Late-onset BSI caused by EGNB increased, but without changes in antibiotic susceptibility. In spite of medical advances, E coli, K pneumoniae, and E cloacae remain responsible for significant morbidity and mortality, especially in very low birth weight infants.

All great truths are iconoclastic: selective decontamination of the digestive tract moves from heresy to level 1 truth

OBJECTIVE

The objective was to compare evidence of the effectiveness, costs and safety of the traditional parenteral antibiotic-only approach against that gathered from 53 randomised trials involving more than 8,500 patients and six meta-analyses on selective decontamination of the digestive tract (SDD) to control infection on the intensive care unit (ICU). PHILOSOPHY: Traditionalists believe that all infections are due to breaches of hygiene except those established in the first 2 days, and that all micro-organisms can cause death. In contrast, newer insights show that transmission via the hands of carers are responsible only for infections occurring after one week, and that only a limited range of 15 potential pathogens contribute to mortality. INTERVENTIONS TO PREVENT ICU INFECTION: The traditional approach is based on hand disinfection aiming at the prevention of transmission of all micro-organisms, to control all infections that occur after 2 days on the ICU. The second feature is the restrictive use of systemic antibiotics, only in cases of microbiologically proven infection. In contrast, SDD aims to control the three types of infection: primary, secondary endogenous and exogenous due to 15 potential pathogens. The classical SDD tetralogy comprises four components: (i) a parenteral antibiotic, cefotaxime, administered for three days to prevent primary endogenous infections typically occurring "early"; (ii) the oropharyngeal and enteral antimicrobials, polymyxin E, tobramycin and amphotericin B administered in throat and gut throughout the treatment on the ICU to prevent secondary endogenous infections tending to develop "late"; (iii) a high standard of hygiene to control transmission of potential pathogens; and (iv) surveillance samples of throat and rectum to monitor the efficacy of the treatment.

ENDPOINTS

(i) Infectious morbidity; (ii) mortality; (iii) antimicrobial resistance; and (iv) costs.

RESULTS

Properly designed trials on hand disinfection have never demonstrated a reduction in either pneumonia and septicaemia, or mortality. Two randomised trials using restrictive antibiotic policies failed to show a survival benefit at 28 days. In both trials the proportion of resistant isolates obtained from the lower ways was >60% despite significantly less use of antibiotics in the test group. A formal cost effectiveness analysis of the traditional antibiotic policies has not been performed. On the other hand, two meta-analyses have shown that SDD reduces the odds ratio for lower airway infections to 0.35 (0.29-0.41) and mortality to 0.80 (0.69-0.93), with a 6% overall mortality reduction from 30% to 24%. No increase in the rate of super infections due to resistant bacteria could be demonstrated over a period of 20 years of clinical research. Four randomised trials found the cost per survivor to be substantially lower in patients receiving SDD than for those traditionally managed.

CONCLUSIONS

The traditionalists still rely on level 5 evidence, i.e. expert opinion, with a grade E recommendation, whilst the proponents of SDD are able to cite level 1 evidence allowing a grade A recommendation in their attempts to control infection on the ICU. The main reason for SDD not being widely used is the primacy of opinion over evidence.

Antimicrobial control programs

The use of broad spectrum antimicrobials, the emergence of multiresistant organisms, and the hospital drug costs associated with antimicrobials have all driven the need for institutions to develop strategies to control the use of antimicrobials. Formulary restrictions, prior approval mechanisms, treatment guidelines, order forms, stop orders, antimicrobial management teams, computer-assisted decision support tools, antimicrobial rotation, and combinations of these practices have all been evaluated as methods to encourage the appropriate use of these agents. While many programs have been successful in reducing antimicrobial costs without compromising patient care, limited data are available on the impact of these programs on the development of multiresistant organisms, particularly in neonatal intensive care units. The optimal means for controlling the emergence of resistance have yet to be determined, but ongoing surveillance of antimicrobial utilization and susceptibility patterns are necessary to identify opportunities for interventions, maximize patient care, and potentially minimize the development of resistance.

Reduction in colonization and nosocomial infection by multiresistant bacteria in a neonatal unit after institution of educational measures and restriction in the use of cephalosporins

INTRODUCTION

Previous administration of third-generation cephalosporins predisposes to colonization and infections by multiresistant Enterobacter sp. The emergence of multiresistant bacteria infections in a neonatal unit during 1995, especially Enterobacter cloacae, stimulated this study.

OBJECTIVE

To evaluate the efficacy of measures to control colonization and nosocomial infection by multiresistant bacteria in a neonatal unit.

SETTING

A tertiary care university hospital.

PATIENTS AND METHODS

This study was conducted from October 1995 through December 1999 in 4 phases: a cross-sectional study, a longitudinal study with intervention measures, monthly cross-sectional studies, and determination of nosocomial infections caused by multiresistant bacteria (oxacillin-resistant Staphylococcus aureus and gram-negative bacteria resistant to either aminoglycosides or third-generation cephalosporins). Specimens for surveillance culture were obtained through umbilical and rectal swabs, and tracheal aspirates from intubated babies. The intervention measures were as follows: (1) appropriated training of the whole health care team, emphasizing measures to reduce cross-colonization, and the importance of rational usage of antibiotics and (2) suppression of usage of third-generation cephalosporins. Risk factors were analyzed through univariate and multivariate logistic regression.

RESULTS

In the first phase, 32% (10/31) of the patients were colonized by multiresistant bacteria (29% by multiresistant E cloacae ). In the second phase, 342 patients were evaluated; 33% of them were colonized by E cloacae, and a multiresistant strain was isolated in 10.8% (37/342) of the babies. A logistic regression model indicated parenteral nutrition and antibiotic usage as risk factors for colonization by multiresistant E cloacae. In the third phase, for 6 months, only 2 patients were colonized by multiresistant E cloacae. In the fourth phase, the analysis of bacterial resistance profile indicated a reduction of nosocomial infections due to multiresistant bacteria from 18 cases in 1995 to 2 cases per year until 1999.

CONCLUSION

These results have shown that the measures adopted were effective.

Increase of Enterobacter in neonatal sepsis: a twenty-two-year study

BACKGROUND

Data on the incidence of Enterobacter infections in neonates over prolonged periods of time are scant. We determined the epidemiology of Enterobacter sepsis and/or meningitis and the trends of infection in a neonatal unit.

METHODS

Retrospective review of sepsis and/or meningitis in inborn neonates admitted to Son Dureta University Hospital during a 22-year period. Molecular study by ribotyping of the Enterobacter strains isolated from 1995 to 1997.

RESULTS

There were 513 cases of culture-proved sepsis and/or meningitis in neonates. In late onset infections Klebsiella pneumoniae and Staphylococcus epidermidis were the most frequent isolates in the period 1977 through 1991. Enterobacter was the most common isolate in the period 1992 through 1998. During this latter period Candida infections also increased, and the resistance rate of Enterobacter to cefotaxime was higher (59.2%). Decrease in early onset infections and increase in late onsets (4.6/1,000 live births) were observed in the second period. From 1977 to 1998, 45 episodes of sepsis and/or meningitis by Enterobacter species were identified in 44 patients (8.7% of all neonatal bacteremias). Three patients with Enterobacter bacteremia died (6.6%, 0.03/1,000 live births). During 1995 through 1997 5 different clones causing sepsis were identified and 3 were predominant. In 1997 there was an outbreak of Enterobacter disease. After cleaning, cohort nursing and hygiene reinforcement, Enterobacter was not isolated in the next 2 years. No change in the antibiotic policy was made.

CONCLUSIONS

We observed a resurgence of Enterobacter infections in our neonatal intensive care unit. The sudden disappearance of this microorganism after reinforcement of hygienic measures, without withdrawing cefotaxime, confirms the importance of patient-to-patient transmission of this nosocomial infection. Further studies are needed to establish the role of antibiotics in the emergence of microorganisms in neonatal intensive care units.

Selective decontamination of the digestive tract: a life saver

Selective decontamination of the digestive tract (SDD), a strategy designed to prevent or minimize the impact of infection by potentially pathogenic micro-organisms in critically ill patients requiring long-term mechanical ventilation, comprises four component protocols, aiming to control the three types of infection occurring in such cases: (i) a parenteral antibiotic, cefotaxime, administered for a few days to prevent primary endogenous infections typically occurring 'early'; (ii) the topical antimicrobials polymyxin E, tobramycin and amphotericin B employed throughout the stay in the intensive care unit to prevent secondary endogenous infections tending to develop 'late'; (iii) a high standard of hygiene to prevent exogenous infections that may occur throughout the stay in the intensive care unit; (iv) surveillance samples of throat and rectum to distinguish between these three types of infection, to monitor the compliance and the efficacy of the treatment, and to detect the emergence of resistance at an early stage. A recent, rigorous, meta-analysis examining 33 randomized SDD trials involving 5727 patients demonstrated a significant reduction in overall mortality (20%) and in the incidence of respiratory tract infections (65%); conclusive evidence that SDD saves the lives of critically ill patients and confirmation that SDD is now an evidence based medicine manoeuvre. This same meta-analysis found no instance of the emergence of resistance or of associated superinfections and/or outbreaks in any of the 33 studies during a period extending upwards of 10 years. By the criterion of cost-per-survivor, four recent randomized trials showed that patient survival is improved more cheaply by employing SDD than by the traditional approaches.

Enterobacter cloacae sepsis outbreak in a newborn unit caused by contaminated total parenteral nutrition solution

OBJECTIVE

The study aimed to investigate an outbreak caused by Enterobacter cloacae in a neonate intensive care unit.

DESIGN

A descriptive study of an outbreak of sepsis in high-risk neonates was used.

SETTING

The study was set in a tertiary care university teaching hospital.

PATIENTS

The patients were 11 neonates infected with Enterobacter cloacae whose symptoms and signs of sepsis developed during a 16-hour period. All but one neonate received parenteral nutrition. Isolates from blood cultures, in-use parenteral nutrition solutions, and control aliquots of parenteral nutrition solution were typed by pulsed-field gel electrophoresis.

RESULTS

Enterobacter cloacae was found in the refrigerated aliquots of parenteral nutrition solution, in blood cultures from infected newborns, and from in-use parenteral nutrition solutions. All these strains of Enterobacter cloacae had the same antibiotic susceptibility pattern and the same genomic DNA profile. The strain isolated from the one patient who did not receive parenteral nutrition presented a different susceptibility profile and genotype.

CONCLUSION

The source of the nosocomial sepsis was the parenteral nutrition solution in 10 neonates. This contamination apparently occurred during preparation of the parenteral solution.

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.

Antibiotics in neonatal infections: a review

The bacteria most commonly responsible for early-onset (materno-fetal) infections in neonates are group B streptococci, enterococci, Enterobacteriaceae and Listeria monocytogenes. Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, are the main pathogens in late-onset (nosocomial) infections, especially in high-risk patients such as those with very low birthweight, umbilical or central venous catheters or undergoing prolonged ventilation. The primary objective of the paediatrician is to identity all potential cases of bacterial disease quickly and begin antibacterial treatment immediately after the appropriate cultures have been obtained. Combination therapy is recommended for initial empirical treatment in the neonate. In early-onset infections, an effective first-line empirical therapy is ampicillin plus an aminoglycoside (duration of treatment 10 days). An alternative is ampicillin plus a third-generation cephalosporin such as cefotaxime, a combination particularly useful in neonatal meningitis (mean duration of treatment 14 to 21 days), in patients at risk of nephrotoxicity and/or when therapeutic monitoring of aminoglycosides is not possible. Another potential substitute for the aminoglycoside is aztreonam. Triple combination therapy (such as amoxicillin plus cefotaxime and an aminoglycoside) could also be used for the first 2 to 3 days of life, followed by dual therapy after the microbiological results. In late-onset infections the combination oxacillin plus an aminoglycoside is widely recommended. However, vancomycin plus ceftazidime (+/- an aminoglycoside for the first 2 to 3 days) may be a better choice. Teicoplanin may be a substitute for vancomycin. However, the initial approach should always be modified by knowledge of the local bacterial epidemiology. After the microbiological results, treatment should be switched to narrower spectrum agents if a specific organism has been identified, and should be discontinued if cultures are negative and the neonate is in good clinical condition. Penicillins and third-generation cephalosporins are generally well tolerated in neonates. There is controversy regarding whether therapeutic drug monitoring of aminoglycosides will decrease toxicity (particularly renal damage) in neonates, and on the efficacy and safety of a single daily dose versus multiple daily doses of these drugs. Toxic effects caused by vancomycin are uncommon, but debate still exists over the need for therapeutic drug monitoring of this agent. When antibacterials are used in neonates, accurate determination of dosage is required, particularly for compounds with a low therapeutic index and in patients with renal failure. Very low birthweight infants are also particularly prone to antibacterial-induced toxicity.

Bloodstream infections in a neonatal intensive-care unit: 12 years' experience with an antibiotic control program

OBJECTIVE

To assess the prevalence of gram-positive coccal (GPC), gram-negative bacillary (GNB), and fungal blood-stream infections (BSIs) during a 12-year period in which a consistent antibiotic treatment protocol was in place; to evaluate the efficacy of these antibiotic policies in relation to treatment, to the emergence of bacterial or fungal resistance, and to the occurrence of infection outbreaks or epidemics.

STUDY DESIGN

Case series.

METHODS

Demographic, clinical, and bacteriological information from 363 infants born during 1986 through 1991 and 1992 through 1997 who developed 433 blood-culture-proven BSIs was analyzed. Early-onset BSIs were defined as those infections discovered within 48 hours of birth, and late-onset BSIs as those that occurred thereafter. Suspected early-onset BSIs were treated with ampicillin and gentamicin, and suspected late-onset BSIs with vancomycin and gentamicin. Antibiotics were changed on the basis of organism antimicrobial susceptibility.

RESULTS

Early-onset BSIs were noted in 52 of 21,336 live births and 40 of 20,402 live births during 1986 through 1991 and 1992 through 1997, respectively. GPC (83% due to group B streptococcus [GBS]) accounted for approximately one half of early-onset BSI cases and GNB (68% Enterobacteriaceae) for the remainder. Early-onset GBS declined from 24 to 11 cases (P=.04) and late-onset BSI increased from 111 to 230 cases (P<.01) from the first to the last study period. Sixty-eight percent of late-onset BSIs were due to GPC (primarily coagulase-negative Staphylococcus), 18% to GNB, and 14% to fungus. Over the study period, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa isolated from the newborn intensivecare unit (unlike those strains from other hospital units) remained fully susceptible to ceftazidime and gentamicin. Although the hospitalwide prevalence of methicillin-resistant Staphylococcus aureus increased, all 17 newborn BSI cases were due to methicillin-sensitive strains. Prevalence of methicillin-resistant coagulase-negative Staphylococcus increased, although all strains remained vancomycin-susceptible, as did the 16 Enterococcus faecalis isolates. All fungi recovered (from 48 patients) were susceptible to amphotericin.

CONCLUSION

We observed a decrease in the prevalence of early-onset BSIs due to GBS and an increase in late-onset BSIs due to GPC, GNB, and fungi. The combination of ampicillin and gentamicin for suspected early-onset BSIs and vancomycin and gentamicin for late-onset BSIs has been successful for treatment of individual patients without the occurrence of infection outbreaks or the emergence of resistance. Controlled antibiotic programs and periodic evaluations based on individual unit and not on hospitalwide antibiograms are advisable.

Use of real time pulsed field gel electrophoresis to guide interventions during a nursery outbreak of Serratia marcescens infection

BACKGROUND

Pulsed field gel electrophoresis (PFGE) is a commercially available technique that can establish clonal relationships among many common hospital-derived organisms with a high degree of accuracy and can yield results in a sufficiently short time to guide interventions during an outbreak investigation.

METHODS

The CHEF Genomic Bacterial DNA Plug Kit (Bio-Rad) was applied to an unfolding nursery outbreak of Serratia marcescens infections according to the manufacturer's guidelines. Bacterial genomic DNA was digested with XbaI or SpeI and separated on 1% agarose gels, and the isolates were grouped by restriction endonuclease patterns according to established standards.

RESULTS

S. marcescens was isolated from nine patients in an intensive care nursery during an 8-week period. Initial PFGE analysis performed after identification of the first eight patients, when closure of the nursery was imminent, revealed that the epidemic was caused by two groups of four isolates each. In both instances the group was geographically contained, and the nursery remained open. A second PFGE analysis indicated that a ninth S. marcescens isolate, recovered in Week 8, was genetically unrelated to the other two. Surveillance during an additional 6 weeks revealed no new cases, and the epidemic was declared over. No cases of invasive S. marcescens infection were identified during the subsequent 10 months.

CONCLUSION

Real-time PFGE determined that an apparent nursery outbreak of S. marcescens infection was, in fact, caused by three genetically distinct strains. This information allowed the nursery to remain open after other appropriate infection control measures had been imposed.

Outbreak of extended spectrum beta lactamase producing Klebsiella pneumoniae in a neonatal unit

An outbreak of extended spectrum beta lactamase producing Klebsiella pneumoniae (ESBLKp) in a neonatal unit was controlled using simple measures. Normally, the control of such infections can be time consuming and expensive. Seven cases of septicaemia resulted in two deaths. ESBLKp isolates were subtyped by pulsed field gel electrophoresis, and four of the five isolates typed were identical. Control of the outbreak was achieved by altered empiric antibiotic treatment for late onset sepsis and prevention of cross infection by strict attention to hand washing. Widespread colonisation of babies in the unit was presumed, so initial surveillance cultures were not performed. No further episodes of sepsis occurred.

Antibiotic restriction does not alter endemic colonization with resistant gram-negative rods in a pediatric intensive care unit

OBJECTIVE

To test whether a ceftazidime restriction policy in a pediatric intensive care unit (ICU) could decrease the endemic rate of colonization with ceftazidime-resistant gram-negative bacilli.

DESIGN

Prospective, pre- vs. postintervention study.

SETTING

University hospital pediatric ICU.

PATIENTS

Consecutive children admitted to the pediatric ICU over a 19-mo period.

INTERVENTIONS

After an observation period in which antibiotic use was not controlled, ceftazidime was prohibited unless the patient's microbiological results indicated that the drug was necessary for cure. Aminoglycoside use was not regulated. The size of the endemic reservoir of ceftazidime- and tobramycin-resistant organisms was determined by daily nasopharyngeal and rectal swab specimens obtained on all admissions to the ICU.

MEASUREMENTS AND MAIN RESULTS

Despite a 96% reduction in ceftazidime use, the incidence density (number of isolates/100 patient-days) of ceftazidime-resistant organisms increased through the course of the study, from 1.57 to 2.16. The incidence density of tobramycin-resistant organisms was unchanged. Ceftazidime restriction resulted in a small but nonsignificant decrease in the proportion of ceftazidime-resistant organisms acquired late (beyond 72 hrs) in the patients' ICU course (56.5% vs. 45.9%). However, there was a more substantial decrease in the proportion of ceftazidime-resistant organisms derived from species known to harbor derepressible amp C beta-lactamases (68.2% vs. 45.9%, p < .05).

CONCLUSIONS

These data indicate that antibiotic restriction policies in an ICU fail to diminish the size of the endemic reservoir of antibiotic-resistant gram-negative rods, and suggest that such policies in the absence of broader efforts to limit antibiotic use will have little impact.

Gram-negative bacilli isolated from patients in intensive care unit: prevalence and antibiotic susceptibility

The surveillance of 100 gram-negative bacilli that were recovered from patients in the intensive care unit (ICU) at King Abdulaziz University Hospital (KAUH), Jeddah, Saudi Arabia showed that Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Enterobacter species, in this order, were the most frequently isolated organisms. The most common sites were respiratory tract (34%), wounds (24%), urinary tract (18%), and blood (11%). The resistance patterns towards different antimicrobial agents were determined by the minimal inhibitory concentration (MIC) using the E test. Imipenem, ciprofloxacin and amikacin were the most active agents against the isolates. Of the gram-negative isolates, 31% were resistant to at least two of the four major antibiotic groups (e.g. aminoglycosides, fluoroquinolones, third generation cephalosporins, and carbapenems), and 6% to three of the groups. Twenty-nine percent of the gram-negative bacilli were resistant to ceftazidime. Ceftazidime-resistant bacteria were frequently resistant to monobactams, piperacillin/tazobactam and gentamicin.

Enterobacter spp.: pathogens poised to flourish at the turn of the century

Knowledge of the genus Enterobacter and its role in human disease has expanded exponentially in recent years. The incidence of infection in the hospital and the community has increased. New clinical syndromes have been recognized. Enterobacter spp. have also been implicated as causes of other syndromes that traditionally have been associated almost exclusively with more easily treatable pathogens, such as group A streptococci and staphylococci. Rapid emergence of multiple-drug resistance has been documented in individual patients during therapy and in populations and environments with strong selective pressure from antimicrobial agents, especially the cephalosporins. Therapeutic options for patients infected with multiply resistant strains have become severely limited. Carbapenems or, alternatively, fluoroquinolones are the most predictively active options, although resistance to both classes has been observed on rare occasions. Enterobacter spp. appear well adapted for survival and even proliferation as the turn of the century approaches.

Risk-stratified nosocomial infection surveillance in a neonatal intensive care unit: report on 24 months of surveillance

OBJECTIVE

To document the nosocomial infection rate in a single neonatal intensive care unit (NICU) in terms of patient workload and device utilization.

METHODOLOGY

Nosocomial infections have been identified and documented by the methodology described by the National Nosocomial Infection Surveillance System (NNIS), Centres for Disease Control, Atlanta. In addition, antibiotic usage has been surveyed in the NICU and standardized measures of patient exposure to antibiotics stratified by birthweight and gestational age have been described.

RESULTS

Overall nosocomial infection rates compared favourably with the published NNIS figures at 6.2 infections per 100 admissions or 4.8 per 1000 patient days. Infection rates were significantly higher in lower birthweight groups. Device-related infection rates in each birthweight cohort were also very close to published figures and varied less with birthweight group. Antibiotic exposure averaged 12% of total admission days, less than previously published data.

CONCLUSIONS

The NNIS system is applicable to Australian NICU and provides an effective tool for monitoring infection episodes.

Epidemiological typing of isolates from an outbreak of infection with multidrug-resistant Enterobacter cloacae by repetitive extragenic palindromic unit b1-primed PCR and pulsed-field gel electrophoresis

An outbreak of multidrug-resistant Enterobacter cloacae infection lasted for 4 months in a neonatal intensive care unit (NICU). Forty-six isolates from the NICU and 20 epidemiologically unrelated strains were characterized by pulsed-field gel electrophoresis (PFGE) and repetitive extragenic palindromic unit b1-primed PCR (REPUb1-PCR) typing. The PFGE patterns after XbaI restriction of the bacterial DNA were analyzed by computer software (Gelcompar) using the UPGMA (unweighted pair group method with arithmetic averages) clustering method and the Dice coefficient. The 46 isolates from the NICU were classified by PFGE typing into five clusters: A (further classified into 7 subtypes, A1 to A7), B, C, D, and E. This outbreak was attributed to multiple genetically related strains of cluster A which had a similarity of 85.8% +/- 4.6%. The minor band differences among strains of cluster A were probably due to minor genetic mutations. The type A1 and A3 strains were isolated from the clinical specimens of patients and hands of nurses. It was probable that these outbreak strains were transmitted among patients via the hands of personnel. REPUb1-PCR typing of the 46 isolates also demonstrated five types, in agreement with results obtained by the PFGE technique, but could not detect the minor mutations among the cluster A strains. Twenty epidemiologically unrelated strains were well distinguished by both PFGE and REPUb1-PCR typing. We conclude that PFGE is a highly discriminatory but time-consuming method for epidemiological typing of E. cloacae and that REPUb1-PCR is a more rapid method with good reproducibility and discriminatory power comparable to that of PFGE.

Antibiotic-resistant gram-negative bacteria in the critical care setting

Gram-negative bacilli that are resistant to commonly used antibiotics are a growing problem in seriously ill, hospitalized patients. Numerous outbreaks involving these organisms have been reported in intensive care nurseries and among critically ill adults. In endemic situations, the major reservoir for these pathogens is the patient; occasionally, transmission from patient to patient occurs through the hands of caregivers. Although the degree of antibiotic use probably plays some role in the emergence of antibiotic-resistant gram-negative bacilli, this relationship has not been uniformly demonstrated, and other factors intrinsic to the organisms themselves and to the critically ill patient may play an important role.

An outbreak of Enterobacter cloacae associated with contamination of a blood gas machine

Over a 3-month period, five cases of Enterobacter cloacae bacteraemia occurred on our neonatal unit. In at least three of these, isolation of the organism coincided with clinical deterioration and evidence of sepsis. In one case, the same strain was isolated from an abscess on the neonate's forearm. The isolates had identical sensitivity patterns being resistant to all beta-lactams tested except imipenem. The extended time course of the infections made cross-infection an unlikely explanation. Moreover, close questioning of the staff and observation of their practices with regard to blood culture collection, failed to reveal any likely mechanism for pseudobacteraemia. On extensive investigation of the environment to try to identify a potential source of the organism, a strain of Enterobacter cloacae, was isolated from the probe of the blood gas machine and the probe cover. No other environmental samples were found to harbour the organism. Subsequent typing procedures showed the blood gas isolate to be indistinguishable from the clinical isolates. Five neonates were successfully treated with imipenem and gentamicin. The exact mechanism whereby these bacteraemias occurred remains obscure. In one case, the baby had positive blood cultures within 2 h of being on the unit and contamination of the blood culture bottle by the doctor taking the culture was suspected. Most of the episodes, however, appeared clinically to be genuine septicaemias. When vigorous infection control procedures were instituted to prevent staff acquisition of the organism from the machine, cases on the unit ceased.

Transient in vivo selection of a constitutively cephalosporin resistant Enterobacter cloacae causing ventriculitis

A case of neonatal ventriculitis complicating a ventriculoperitoneal shunt and caused by one strain of Enterobacter cloacae (as shown on pulsed field gel electrophoresis) is presented. Daily ventricular fluid cultures from day 1 to 9 revealed inducible cephalosporin resistance in all isolates except on days 3, 4 and 5 of therapy when isolates were constitutively resistant. This emergence of resistance due to constitutive Bush class 1 beta-lactamase production is an excellent example of the rapid emergence of a predominant strain of bacteria depending on antibiotic selection pressures in vivo. The transient nature of the predominant resistant phenotype may have been due to missing a dose of cefotaxime on day 5 or in vivo factors allowing persistence of sensitive organisms in antibiotic protected sites. Caution is advised in the use of cephalosporins alone for serious Enterobacter species infections. Repeat culture and sensitivity should be done in severe infections that are slow to respond to cephalosporin therapy.

Enterobacter cloacae in a neonatal intensive care unit: account of an outbreak and its relationship to use of third generation cephalosporins

After uneventful use of cefotaxime and ceftazidime as first line therapy for three years in our neonatal intensive care unit we isolated cephalosporin-resistant Enterobacter cloacae (CREC) strains which caused clusters of cases or colonization and/or serious neonatal infection. By using two or more typing methods, at least five different strains with similar patterns of antimicrobial sensitivities were identified. The results of a case-control study did not support the notion that the use of third generation cephalosporins was associated with colonization and infection by CREC. The outbreak was brought under control by interrupting the transmission of the epidemic strain D, by measures such as cohort nursing, diligent handwashing before and after procedures, and thorough environmental cleaning as well as by decontamination with glutaraldehyde after dismantling of the blood gas analyser believed to have acted as a persistent reservoir. Our experience highlights the danger of inadequate supervision and maintenance of equipment used for near-patient testing and the need to monitor such equipment not only in terms of its calibration and analytical performance but also microbiologically.

Arbitrarily primed PCR, ribotyping, and plasmid pattern analysis applied to investigation of a nosocomial outbreak due to Enterobacter cloacae in a neonatal intensive care unit

In December 1992, Enterobacter cloacae was isolated from the oropharynx and respiratory tract of six ventilated neonates hospitalized in the intensive care unit (ICU) of our hospital. To establish the spread of the outbreak, 41 strains of E. cloacae were analyzed for genotypic markers by three methods: plasmid profile analysis, ribotyping with EcoRI or PvuII endonuclease, and arbitrarily primed (AP) PCR. The tested strains included 12 isolates from the 6 epidemic cases, 4 isolates from the respiratory tract of 4 children hospitalized in other wards during the same period, 13 isolates from 12 children hospitalized in pediatric units before or after the outbreak, and 12 epidemiologically unrelated isolates. Ribotyping and AP PCR demonstrated that each of the last 12 strains exhibited distinct genomic patterns, as did each of the strains isolated from neonates hospitalized before or after the epidemic peak. Conversely, two clones of strains were found among the isolates recovered in December, with concordant results being obtained by the three typing methods: the first clone included seven strains from five ventilated children in the ICU and two children from another ward; another clone was shared by one neonate in the ICU and an infant from another ward. These results indicate that ribotyping and AP PCR-the latter applied, to our knowledge, for the first time to the genotypic analysis of E. cloacae--represent very discriminatory tools for the investigation of nosocomial outbreaks caused by this species.