An outbreak of multiply resistant Pseudomonas aeruginosa in a neonatal unit: plasmid pattern analysis

[Pseudomonas aeruginosa infections in a neonatal care unit at Reunion Island]

OBJECTIVE

To investigate an outbreak of Pseudomonas aeruginosa (PA) hospital-acquired infections in neonates.

METHODS

Incidences were assessed retrospectively in the neonatal care units of the Groupe Hospitalier Sud-Réunion, from January 2003 to September 2005. Environmental survey, audit of health care workers and case-control study were performed to reinforce staff training and to determine risk factors.

RESULTS

Of 1432 neonates, 40 were infected (median gestational age: 29 weeks, median birth weight: 1195 g), accounting for an attack rate of 2.8%. Between January 2003 and January 2004, incidence rates were less than 2 infections per 1000 hospitalisation days. In the last trimester of year 2004, the incidence rose to 5.6 infections per 1000 hospitalisation days and PA was found in all ocular swabs, leading to diagnose an epidemic. However, it was only 3 months later, after 3 new deaths of very preterm neonates, that the implementation of control measures and an audit of health care practices focused on water utilisation ruled out the outbreak. The overall fatality rate was 25%, and of 71% in severe diseases (septicemia or pneumonia). The epidemic pattern argued for a common unique source. Two risk factors were identified by logistic regression: exposure to mechanical ventilation beyond 4 days (OR 3.3; CI 95%: 1.3-8.4) and very preterm birth (OR 2.7; CI 95%: 1.0-7.7).

CONCLUSION

Our findings highlight the need for a close collaboration between neonatologists and hygienists to improve health care practices and surveillance.

An outbreak of Pantoea spp. in a neonatal intensive care unit secondary to contaminated parenteral nutrition

Contaminated parenteral nutrition (PN) is an important source of infection in neonates. Many organisms have been reported to cause contamination that results in outbreaks in intensive care units. The objective of this study was to investigate an outbreak caused by Pantoea spp., which contaminates PN, in a neonatal intensive care unit (NICU). This was a descriptive study of an outbreak of sepsis in an NICU of a tertiary teaching hospital in Malaysia. Pantoea spp. infection was detected in eight patients over a three-day period from 24 to 27 January 2004 following the administration of PN. Seven of the eight patients died due to the infection. Extensive environmental samplings for culture were performed. PN solution from the NICU and the pharmacy were also cultured during the outbreak period. Pantoea spp. was isolated from blood cultures of all infected patients, and the unused PN from the pharmacy and the NICU. All the strains of Pantoea spp. had a similar antibiotic susceptibility pattern and biochemical reaction. From the results, we concluded that PN was the source of the outbreak and the contamination may have occurred during its preparation in the pharmacy. A thorough investigation has been carried out and, where possible, corrective measures have been taken to avoid similar outbreaks in the future.

Ciprofloxacin treatment in newborns with multi-drug-resistant nosocomial Pseudomonas infections

OBJECTIVES

To evaluate the efficacy and acute side effects of ciprofloxacin treatment in newborns who developed nosocomial Pseudomonas aeruginosa infection.

METHODS

Intravenous ciprofloxacin treatment was given to 30 newborns who developed nosocomial P. aeruginosa infection as proven by culture antibiogram results. Initial doses of 10 mg/kg/day were given and increased up to 40 mg/kg/day according to clinical response, laboratory and culture results. During therapy, complete white blood cell counts, urinalysis, liver and renal function tests were performed weekly. All patients were examined daily during treatment for possible symptoms of joint toxicity such as erythema and swelling. The patients were evaluated by general physical examination, with special attention to joints, 1 week after discharge.

RESULTS

Two of the patients (6.6%) died due to pseudomonas infection, but the bacteria were successfully eradicated in 28 patients (93.4%). Four patients died from other causes. No laboratory abnormality related to ciprofloxacin was observed during treatment. Swelling and hyperemia of the joints were not encountered during treatment and the 1-week period after discharge. Ciprofloxacin-resistant P. aeruginosa isolates were not grown during the study.

CONCLUSION

Ciprofloxacin treatment is effective in life-threatening multi-drug-resistant P. aeruginosa infections.

Transmission of a multiresistant Pseudomonas aeruginosa strain at a German University Hospital

Over 15 months, 60 patients at a German University Hospital became infected or colonized by a multiresistant Pseudomonas aeruginosa strain, which was isolated from tracheal secretions, blood, urine, venous catheters, ascites and several wounds. Most patients had undergone invasive treatment (surgery, cancer therapy). The genetic relationship of the isolates was investigated by pulsed field gel electrophoresis. The isolates were resistant to beta-lactam antibiotics, including carbapenems and aztreonam, to aminoglycosides and quinolones. The only in vitro susceptibility was to polymyxin B. Extensive sampling was carried out to identify contaminated medical devices, surfaces or media (water, food). Samples were taken from doctors and nursing staff and various treatment procedures were observed for several weeks. The handling of respirators, resuscitation tubes, urine bottles, and bedpans resulted in the contamination of the patients' environment, although most devices were cleaned and disinfected with automatic washer/disinfectors. Several wash basins on the intensive care unit were contaminated, but none of the drinking water samples showed any growth of P. aeruginosa. We recommend the strict use of gloves and strict application of alcoholic hand disinfectants immediately after discarding the gloves. The chain of infection ceased after strict cohort isolation and the subsequent introduction of the specific hygiene regime.

Ventilator-associated pneumonia in very low-birth-weight infants at the time of nosocomial bloodstream infection and during airway colonization with Pseudomonas aeruginosa

PURPOSE

To study retrospectively the incidence of ventilator-associated pneumonia (VAP) at the time of Pseudomonas aeruginosa nosocomial bloodstream infection (BSI) and at the time of P aeruginosa airway colonization.

MATERIALS AND METHODS

Fifteen very low-birth-weight infants who had P aeruginosa BSI and 33 others who did not but who had P aeruginosa airway-colonization were studied. We correlated clinical data, blood cultures (BCs), and tracheal cultures (TCs) with radiologic findings from radio-graphs taken within 2 days before, the day of, and 1 day after BCs or TCs were first positive for P aeruginosa. Chest radiographs were graded by using semiquantitative scores for bronchopulmonary dysplasia and for pneumonia.

RESULTS

Mean birth weight, gestational age, and age when BC or TC became positive were similar for patients with BSI and colonization. At the time of BSI, 2 infants had airway colonization with P aeruginosa; the TCs of the remaining 13 grew P aeruginosa as a new pathogen. Thirteen of 15 patients with BSI, but none of 33 infants with colonization, died within 2 days of positive BC. VAP was diagnosed in 13 of 15 patients with BSI and in 3 of 33 infants with colonization.

CONCLUSION

Mechanically ventilated very low-birth-weight infants whose TCs yield P aeruginosa but whose BCs remain negative infrequently have VAP are presumed airway-colonized and are expected to survive. Conversely, VAP is likely to be found when BCs and TCs simultaneously grow P aeruginosa, and high mortality is anticipated.

An outbreak of influenza A in a neonatal intensive care unit

OBJECTIVES

Investigation of an outbreak of influenza A in a neonatal intensive care unit (NICU) with examination of risk factors for infection and outcomes.

DESIGN

Retrospective cohort study of infants admitted to the unit during the outbreak period. Prospective survey of NICU staff and mothers of infants in the cohort study.

SETTING

Level III nursery in a university-affiliated tertiary referral center.

RESULTS

Nineteen infants in the NICU were infected with influenza A There were six symptomatic cases and one death who had evidence of virus-associated hemophagocytic syndrome at autopsy. Amantadine prophylaxis was offered to the NICU staff, and amantadine therapy was given to five of the six symptomatic infants. Mechanical ventilation, gestational age, birth weight, Clinical Risk Index for Babies score, and twin pregnancy were associated with acquisition of influenza A on univariate analysis. Mechanical ventilation (odds ratio [OR], 6.2; P=.02) and twin pregnancy (OR, 7.0; P=.04) remained as significant risk factors for infection on multiple logistic regression analysis. Only 15% of respondents to the NICU staff survey were vaccinated against influenza. There was no association between a history of an influenza-like illness during pregnancy and acquisition of influenza A by infants of mothers who responded to the maternal survey (OR, 0.91; P=1.0).

CONCLUSIONS

Influenza A is an important pathogen in the neonatal population and is readily transmissible in the NICU setting.

Neonatal airway colonization with gram-negative bacilli: association with severity of bronchopulmonary dysplasia

BACKGROUND

Airway colonization with Gram-negative bacilli (GNB) and Gram-positive cocci (GPC) is common in mechanically ventilated neonates. Whether GNB are related to nosocomial bloodstream infection (BSI) and/or to the severity of bronchopulmonary dysplasia (BPD) is unknown.

METHODS

We prospectively examine this relationship using a cohort design. Data from 260 < or = 1250-g birth weight inborn infants (1991 to 1995) intubated > or = 2 weeks included 917 serial tracheal cultures and 583 blood cultures. The severity of BPD was assessed by duration of mechanical ventilation, oxygen dependency at 36 weeks of postconceptional age and the use of home oxygen supplementation.

RESULTS

After 2 weeks of ventilation, 80% of the infants were colonized with GPC (Staphylococus epidermidis and Staphylococcus haemolyticus in 90% of the cases). Superimposed on 36% of these infants was GNB airway colonization with Klebsiella pneumoniae (25%), Enterobacter cloacae (25%), Escherichia coli (25%), Pseudomonas aeruginosa (10%), Serratia marcescen (10%), Acinetobacter baumannii and Haemophilus influenzae (5%). Comparison between 174 GPC- and 86 GNB-colonized infants showed that demographics, birth weight, gestational age, perinatal risk factors and mortality were similar. Fifteen percent of GNB-colonized infants developed BSI caused by GNB and 14% developed BSI caused by GPC. No significant temporal relationship between airway colonization and BSI was noted. GNB infants were ventilated longer and required oxygen at 36 weeks of postconceptional age and home oxygen supplementation twice as often as infants colonized only with GPC. GNB colonization was a predictor of severe BPD after controlling for ventilation. Ureaplasma colonization occurred in 28% of GNB-colonized and 33% of noncolonized infants and was not a predictor of BPD severity.

CONCLUSION

GNB airway colonization creates a moderate risk for BSI. Antibiotic treatment does not regularly eradicate GNB. GNB airway colonization is associated with severe BPD, but further studies will be necessary before therapeutic efforts to eradicate GNB from the airways should be undertaken.

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.

Lack of association between clinical and environmental isolates of Pseudomonas aeruginosa in hospital wards

Seventy-three environmental and clinical isolates of Pseudomonas aeruginosa recovered from a single hospital over a 6-month period were compared for epidemiological type characteristics. Environmental isolates were obtained from sinks, taps and water, in rooms where patients were treated. The strains represented only six O-antigenic types and 8.2% of them were not typable. Serotype 011 was most frequent in the environment, whereas serotypes 06, 012 and 02,5 predominated among clinical isolates. More than 60% of all isolates belonged to four pyocin types (1, 10, 33 and 45), and approximately 80% were phage typable. Environmental isolates were more sensitive to antibiotics than clinical isolates. There was little correspondence between the types of strains of P. aeruginosa isolated from patients and those isolated from the environment. However, isolates of identical type were frequently recovered from different patients within the same clinic and were found to be related in time and location. We conclude that the environment was not an important source of P. aeruginosa infection and that transfer of organisms was mainly from patient-to-patient.

Diversity of resistance phenotypes and plasmid analysis in multi-resistant 0:12 Pseudomonas aeruginosa

Antibiotic resistance phenotypes, plasmid content and ability of conjugal transfer of antibiotic resistance genes of 35 multi-resistant Pseudomonas aeruginosa strains were examined. The strains were isolated in 12 Greek hospitals and the majority of them (80%) belonged to serotype 0:12. The isolates were distributed to a variety of different antibiotic resistance phenotypes. Plasmid analysis showed that 10 isolates harboured plasmids ranging in size from 20 to 100 Mda. Among these strains, four carried plasmids of 100 Mda, two strains had 60 Mda plasmid each while in three strains the plasmids detected were 65, 25 and 20 Mda, respectively. One strain harboured two plasmids of 100 and 60 Mda. All strains containing plasmids belonged to 0:12 serotype, except the one harbouring the 25 Mda plasmid, which belonged to serotype 0:6. Using a P. aeruginosa recipient resistant to rifampicin and ciprofloxacin, conjugal transfer was achieved in two occasions. These plasmids, 100 Mda in size, encoded high-level resistance to both gentamicin and tobramycin whereas resistance to other drugs was not transferable. Interestingly, all 100 Mda plasmids, including the self-transferable ones, were found to share a certain degree of homology as judged by restriction analysis. It is suggested that both resistance phenotypes and analysis of plasmid content might be useful in subdividing 0:12 multi-resistant P. aeruginosa.