Nosocomial colonization due to imipenem-resistant Pseudomonas aeruginosa epidemiologically linked to breast milk feeding in a neonatal intensive care unit.
OBJECTIVE
We describe a one-year investigation of colonization by imipenemresistant, metallo-beta-lactamase (MBL) producing Pseudomonas aeruginosa in a neonatal intensive care unit (NICU) of the University Hospital of Palermo, Italy.


METHODS
A prospective epidemiological investigation was conducted in the period 2003 January to 2004 January. Rectal swabs were collected twice a week from all neonates throughout their NICU stay. MBL production by imipenem-resistant strains of P aeruginosa was detected by phenotypic and molecular methods. Pulsed field gel electrophoresis (PFGE) was carried out on all isolates of P aeruginosa. The association between risk factors and colonization by imipenem-resistant, imipenem-susceptible P aeruginosa isolates and other multidrug-resistant Gram negative (MDRGN) organisms was analyzed for variables present at admission and during the NICU stay. Data analysis was carried out by the Cox proportional hazards regression model.


RESULTS
Twentytwo of 210 neonates were colonized with imipenem-resistant, MBL-producing P aeruginosa isolates and 14 by imipenem-susceptible P aeruginosa isolates. A single pulsotype, named A, was shared by all imipenem-resistant isolates. Colonization by P aeruginosa of pulsotype A was positively correlated with breast milk feeding and administration of ampicillin-sulbactam, and inversely correlated with exclusive feeding by formula. In the Cox proportional hazards regression model, birthweight of more than 2500 g and breast milk feeding were independently associated with an increased risk of colonization by MBL producing P aeruginosa.


CONCLUSIONS
The results strongly support an association between colonization by a well-defined imipenem-resistant, MBL producing P aeruginosa strain and breast milk feeding. Such a study may highlight the need for implementation of strategies to prevent expressed breast milk from becoming a vehicle of health care-associated infections.
Mammina
Caterina
C
Dipartimento di Scienze per Promozione della Salute G. D'Alessandro, Universita degli Studi, Palermo, Italy. diptigmi@unipa.it
Di Carlo
Paola
P
Cipolla
Domenico
D
Casuccio
Alessandra
A
Tantillo
Matilde
M
Plano
Maria Rosa Anna
MR
Mazzola
Angela
A
Corsello
Giovanni
G
D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001942:Breast Feeding / Q000009:adverse effects*; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006801:Humans; D015378:Imipenem / Q000627:therapeutic use*; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D008297:Male; D008826:Microbial Sensitivity Tests; D008895:Milk, Human / Q000382:microbiology*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011552:Pseudomonas Infections / Q000453:epidemiology / Q000635:transmission; D011550:Pseudomonas aeruginosa / Q000378:metabolism; D012307:Risk Factors; D015996:Survival Rate
D000900:Anti-Bacterial Agents; D015378:Imipenem