Molecular Epidemiology of Antibiotic-Resistant Gram-Negative Bacilli in a Neonatal Intensive Care Unit During a Nonoutbreak Period

• Published in: Pediatrics (Evanston) 2001-11, Vol.108 (5), p.1143-1148
• Main Authors: Toltzis, Philip, Dul, Michael J, Hoyen, Claudia, Salvator, Ann, Walsh, Michele, Zetts, Laura, Toltzis, Hasida
• Format: Article
• Language: English
• Subjects: Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Anti-Bacterial Agents - pharmacology; Antibiotics; Babies; Biological and medical sciences; Carrier state (Communicable diseases); Ceftazidime - pharmacology; Critical care; DNA, Bacterial - analysis; Drug resistance in microorganisms; Drug Resistance, Microbial - genetics; Electrophoresis, Gel, Pulsed-Field; Emergency and intensive care: neonates and children. Prematurity. Sudden death; Enterobacteriaceae - drug effects; Enterobacteriaceae - genetics; Epidemiology; Gentamicins - pharmacology; Gram-negative bacteria; Gram-Negative Bacteria - drug effects; Gram-Negative Bacteria - genetics; Health aspects; Humans; Infants (Newborn); Intensive care medicine; Intensive Care Units, Neonatal; Medical sciences; Microbial drug resistance; Molecular Epidemiology; Neonatal care; Newborn infants; Organisms; Pediatrics; Penicillanic Acid - analogs & derivatives; Penicillanic Acid - pharmacology; Piperacillin - pharmacology; Prospective Studies; Tazobactam
• ISSN: 0031-4005; 1098-4275
• DOI: 10.1542/peds.108.5.1143

Gram-negative organisms that are resistant to parenteral antibiotics are a growing threat to hospitalized patients. This study was conducted to define the epidemiologic characteristics of these organisms during a nonoutbreak period in a neonatal intensive care unit (NICU). Nasopharyngeal and rectal swab specimens were obtained 3 times a week from every infant in a tertiary care NICU during a 12-month period. Specimens were processed to identify aerobic Gram-negative species resistant to gentamicin, piperacillin-tazobactam, or ceftazidime. Selected clinical parameters were tested for their association with colonization with a resistant organism. Restriction endonuclease digests of genomic DNA were derived from isolates of the most frequently occurring species. The fragments were analyzed by pulsed-field gel electrophoresis (PFGE) to determine the genetic relatedness of the various isolates and thereby determine the length of colonization, the frequency of horizontal transmission, and the size and duration of clusters. A total of 101 infants (8.6%) of 1180 admissions were colonized with at least 1 antibiotic-resistant bacillus before NICU discharge. Multiple parameters indicating a prolonged, complicated NICU course were associated with resistant colonization, including gestational age, length of stay, and exposure to several classes of antibiotics. Colonization with resistant bacilli occurred as early as the first NICU day, but acquisition continued throughout the infants' stay. A total of 436 isolates were analyzed by PFGE. On the basis of this molecular analysis, it was determined that duration of colonization was usually very short; the median for all species tested was