Beta-lactam antibiotic resistance in aerobic commensal faecal flora in newborns

Beta-lactam Antibiotic Resistance in Aerobic Commensal Faecal Flora in Newborns Dr. Murat Duman Over the past two decades, gram negative bacteria producing extended spectrum beta-lactamases (ESBL) which coded by plasmid and responsible from the resistance against oxyimino beta-lactams (cefotaxime.ceftazidime) and monobactams (aztreonam) have become prominent pathogens of the nosocomial infections in neonatal intensive care unit (NICU). Persistence of intestinal colonization with resistant strains after leaving the hospital leads to both rapid dissemination of these bacteria in the population and significant problems in the treatment of new infections caused by the transmission of the resistance determinants to other pathogen bacteria. This study was designed prospectively to determine the colonization of beta lactam antibiotic resistant bacteria in commensal faecal flora of newborns and the risk factors leading to this colonization. One hundred and eighteen newborns including study group (NICU)(n=38), neonatal ward group (n=36) and control group (n=44) were enrolled in the study. Three or four stool samples were obtained fifteen days apart from each infant. Colonization with ampicilline resistant commensal faecal flora microorganisms was determined in 276 (75.2%) of total 367 stool samples. Klebsiella spp. and E. coli were identified in 59% and 41% of the samples respectively. The highest rate of ampicilline resistant bacteria colonization was determined in neonatal ward group (p=0.004). ESBL producing microorganisms were identified in 124 (33.7%) of 367 stool samples. Fifty one (45.1%) and 73 (44.8%) of ampicilline resistant E. coli and Klebsiella spp. isolates were determined to produce ESBL respectively. There was no difference with respect to colonization with ESBL producing microorganisms between the three groups (p=0.056). ESBL production rate in commensal bacteria was higher significantly in the samples obtained during hospitalization period with respect to the samples obtained after discharge in all three groups (study group: 53.2%-22.0%, p=0.002; neonatal ward group: 69.0%-26.2%, p=0.000; control group: 84.2% - 48.1% p=0.004). ESBLproduction rate were 61/95 (64.2%) and 63/181 (34.8%) in the bacteriae isolated from the samples obtained in and out of the hospital respectively and the difference was statistically significant (p=0.0001). When the risk factors related to colonization with ESBL producing microorganisms in stool samples were evaluated through the whole study period: very low birth weight (<1500 g) (RR=22.02, p=0.021), vaginal delivery (RR=3.52, p=0.017), antibiotic usage in the patient (RR=14.05, p=0.035), maternal antibiotic usage (RR=3.81, p=0.038), male sex (RR=2.61, p=0.031) and premature rupture of membrane (RR=7.41, p=0.031) were determined as risk factors, while feeding with nasogastric tube (RR=0.05, p=0.021) was identified as preventive factors. When the risk factors related to colonization with ESBL producing bacteria in stool samples after discharge from the hospital were evaluated, only not feeding with breast milk was determined as a risk factor (RR=7.6, p=0.028). Twelve patients in NİCU were diagnosed to have sepsis and in and blood cultures were positive in five of these cases. In two patients in whom K. pneumoniae were recovered from the blood cultures, colonization of intestinal flora with ESBL producing K. pneumoniae having similar resistance pattern was also determined. In the remaining patients with positive blood cultures, Alpha hemolytic streptococci (n=2) and Streptococcus pneumoniae (n=1) were isolated. ESBL producing K. pneumoniae and E. coli colonization were determined in intestinal flora of four and three of the remaining patients with negative blood cultures respectively. The most important approach to decrease mortality and morbidity due to infection caused by resistant microorganisms colonized in normal flora of the infant is to provide colonization of the newborn with normal non-pathogenic bacteria. This, in turn could be achieved by feeding with fresh breast milk from their mothers, application of infection control measures efficiently and limitation of antibiotic usage only on strict clinical indications. In addition, definition of colonization with resistant microorganisms and epidemiological characteristics of the infections will play an important role in the development of strategies to control these infections. Key words: Commensal faecal flora, colonization, newborn, beta-lactam antibiotic resistance, ESBL.