Amikacin, gentamicin and tobramycin resistant Pseudomonas aeruginosa in a leukaemic ward. Epidemiology and genetic studies

Sources of sporadic Pseudomonas aeruginosa colonizations/infections in surgical ICUs: Association with contaminated sink trap

BACKGROUND

Many studies have reported the hospital outbreaks of Pseudomonas aeruginosa due to cross-contamination between patients and water fittings, but the importance of water fittings as sources of sporadic P. aeruginosa colonizations/infections remains ambiguous.

AIM

To investigate the sources of sporadic P. aeruginosa colonizations/infections in a clinical intensive surveillance, and further analysis the potential of sink trap for P. aeruginosa transmission in intensive care units (ICUs).

METHODS

Patients monitoring and targeted environmental screening for P. aeruginosa was performed prospectively over a 27-week period, in absence of recognized outbreak, in two surgical intensive care units (SICUs). All isolates were genotyped by Pulsed field gel electrophoresis analysis.

FINDINGS

18.9% (46/244) of water fitting samples harbored P. aeruginosa, and active screening samples from 9.2% (55/595) of hospitalized patients carried with P. aeruginosa. According to genotype results, approximately 50% of P. areuginosa colonizations/infections of patients were of exogenous origin. 64.7% (11/17) of exogenous sourced cases were associated with contaminated sink traps. There was a significant correlation between the incidence of exogenous colonization/infection and the prevalence of P. areuginosa in water fitting in SICU-2 (rs = 0.972; p = 0.014). Furthermore, P. areuginosa from sink trap possessed a higher level of resistance to multi-antibiotics as opposed to cross-transmission from other patients.

CONCLUSION

Water fitting especially sink trap act as an important role in sporadic P. aeruginosa transmission in SICU patients. This report highlights the necessity of identification of potential environmental reservoirs, such as sinks, for control of infections of environmentally hardy multi-resistant P. areuginosa.

Multidrug-resistant Pseudomonas aeruginosa outbreaks in two hospitals: association with contaminated hospital waste-water systems

BACKGROUND

Multidrug-resistant Pseudomonas aeruginosa (MDR-P) expressing VIM-metallo-beta-lactamase is an emerging infection control problem. The source of many such infections is unclear, though there are reports of hospital outbreaks of P. aeruginosa related to environmental contamination, including tap water.

AIM

We describe two outbreaks of MDR-P, sensitive only to colistin, in order to highlight the potential for hospital waste-water systems to harbour this organism.

METHODS

The outbreaks were investigated by a combination of descriptive epidemiology, inspection and microbiological sampling of the environment, and molecular strain typing.

FINDINGS

The outbreaks occurred in two English hospitals; each involved a distinct genotype of MDR-P. One outbreak was hospital-wide, involving 85 patients, and the other was limited to four cases in one specialized medical unit. Extensive environmental sampling in each outbreak yielded MDR-P only from the waste-water systems. Inspection of the environment and estates records revealed many factors that may have contributed to contamination of clinical areas, including faulty sink, shower and toilet design, clean items stored near sluices, and frequent blockages and leaks from waste pipes. Blockages were due to paper towels, patient wipes, or improper use of bedpan macerators. Control measures included replacing sinks and toilets with easier-to-clean models less prone to splashback, educating staff to reduce blockages and inappropriate storage, reviewing cleaning protocols, and reducing shower flow rates to reduce flooding. These measures were followed by significant reductions in cases.

CONCLUSION

The outbreaks highlight the potential of hospital waste systems to act as a reservoir of MDR-P and other nosocomial pathogens.

Surveillance of hospital-acquired infection in the Republic of Ireland: past, present and future

There is increasing interest in the surveillance of hospital-acquired infection (HAI) in the Republic of Ireland due to a greater awareness of the consequences of antibiotic resistance, and consumer pressure in the form of public expectations of the quality of health care. To date there have been no nationwide prospective surveillance projects but surveillance has taken place in the form of participation in international and national studies, and the description of local outbreaks. Infection control teams and others have participated in projects such as a European study of HAI in intensive care units conducted in 1992, the second national prevalence study conducted in the UK in 1993 and two surveys of methicillin-resistant Staphylococcus aureus (MRSA) carried out in 1995 and 1999, the latter involving colleagues in Northern Ireland. There have been a number of local surveys of antibiotic-resistant bacteria including the molecular characterization of MRSA in Dublin hospitals, vancomycin-resistant enterococci, and Gram-negative bacteria such as Enterobacter spp. and Serratia spp. affecting compromised patients such as bone marrow transplant recipients. In the future, it is hoped to standardize case definitions, automate data entry, increase collaboration with surveillance initiatives in Northern Ireland and link in with European networks such as EARSS and HELICS. Apart from the need to improve the quality of health care in Irish hospitals, approximate costings suggest that there are potential savings of 7.5 pounds sterling -15 pounds sterling m to be made following a reduction of HAI rates of 15%.

Eradication of a resistant Pseudomonas aeruginosa strain after a cluster of infections in a hematology/oncology unit

OBJECTIVES

This report chronicles an outbreak of a multiply resistant strain of Pseudomonas aeruginosa and the measures required to contain this outbreak.

METHODS

Laboratory-based ward-liaison surveillance allowed the detection of a multiply resistant strain of P. aeruginosa infecting patients in our hematology/oncology unit. Sampling of the immediate environment was carried out. Pulsed field gel electrophoresis was used to compare the patients' organisms with those found in the environment. Extensive dismantling of the drainage system, repeated cleaning and disinfection, and a review of the departmental antibiotic policy were some of the infection control measures instigated.

RESULTS

During a period of 11 months, three patients in the hematology department and two patients in the oncology department were infected with multiply resistant P. aeruginosa. There were two cases of pneumonia, one of which was fatal, and two cases of neutropenic septicaemia. Pulsed field gel electrophoresis performed on the isolates showed that the isolates from geographically separate areas could be divided into two strains that were closely related but distinct. Two genotypically identical strains were also isolated from the plumbing systems in the areas of each ward where patients had been treated.

CONCLUSIONS

The potential for serious nosocomial infections with P. aeruginosa is well recognized. Eradication of the organism from the environment may require the co-ordinated efforts of clinicians, nurses, pharmacy and hospital engineers, working in collaboration with the hospital infection control team. To date, the same strains have not been isolated despite repeated surveillance over the past 18 months and therefore these measures have, in our opinion, successfully removed the potential for nosocomial infection with this resistant organism in our hospital.

Enterobacter cloacae in a haematology/oncology ward--first impressions

The observation that Enterobacter cloacae has emerged as a cause of infection in a haematology/oncology ward prompted a prospective study over an eight-month period. Sensitivity to antibiotics, plasmid screening and typing methods were used to describe the epidemiology of the organism which was isolated from 22 patients. There was evidence of a limited amount of cross infection. No common sources were found. A large number of distinct strains were identified. E. cloacae infection was associated with prolonged profound leucopenia and broad-spectrum antibiotic therapy.

Prevalence and profiles of plasmids in Pseudomonas aeruginosa

The value of plasmid profile determination as an epidemiological tool in Pseudomonas aeruginosa infections was investigated by determining the prevalence of plasmids in 450 Pseudomonas aeruginosa strains and comparing the technique with other epidemiological tools. Since only 13.9% of these strains harbored plasmids and the majority of these plasmids were antibiotic resistant, the technique appeared to be less appropriate as an epidemiological tool in this organism than other techniques. Comparison of results obtained from plasmid profile determinations with those from antibiotyping, serotyping and pyocin typing in 50 non-epidemic strains showed the technique gave highly reproducible results and was sensitive; its ability to discriminate could be improved by additionally performing conjugation assays and hydrolysis of plasmidic DNA with restriction enzymes. It is concluded that plasmid profiles provide important epidemiological information on Pseudomonas aeruginosa infections when performed in conjunction with either serotyping or, more importantly, pyocin typing.

Outbreak of colonization of neonates with Enterobacter sakazakii

An outbreak of colonization of 11 neonates with Enterobacter sakazakii occurred in a neonatal intensive care unit from the 10 September to 17 October 1984. During this period Ent. sakazakii was isolated from throat and rectal swabs and tracheal aspirates, but not from blood, of the neonates. The duration of colonization ranged from 2 to 8 weeks. The isolates were resistant to amikacin and to tobramycin, but sensitive to gentamicin. Four of the 11 colonized neonates had clinical signs of severe sepsis and one of meningitis and four died in spite of intensive chemotherapy. The source and the mode of spread of Ent. sakazakii remained unknown as it was not found on the hands of staff or in the inanimate environment of the unit. Ent. sakazakii may be implicated in severe infections in neonates and should be included when screening clinical specimens.