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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Pediatr. | doi: 10.3389/fped.2018.00359

High-temperature short-time treatment of human milk for bacterial count reduction

 Daniel Klotz1*, Marie Schreiner1,  Valeria Falcone2,  Daniel Jonas3, Mirjam Kunze4, Andrea Weber5,  Hans Fuchs1 and  Roland Hentschel1
  • 1Department of Neonatology and Neonatal Intensive Care, Faculty of Medicine, University of Freiburg, Germany
  • 2Institut für Virologie, Universitätsklinikum Freiburg, Germany
  • 3Institut für Infektionsprävention und Krankenhaushygiene, Universitätsklinikum Freiburg, Germany
  • 4Klinik für Frauenheilkunde, Universitätsklinikum Freiburg, Germany
  • 5Institut für Medizinische Mikrobiologie und Hygiene, Uniklinik Freiburg, Germany

Background: Human milk (HM) for preterm infants will often be pasteurized for cytomegalovirus (CMV) inactivation and reduction of its bacterial count. High-temperature short-time (HTST) treatment compared to standard Holder pasteurization (HoP) reduces the impact of heat treatment on bioactive HM proteins while effectively inactivating CMV. No data are available for the efficacy of bacterial count reduction using HTST treatments that are available for clinical use.

Objective: To test the antiviral and antibacterial efficacy of HTST treatment protocols in HM using a modified HTST treatment device compared to standard HoP.

Methods: Holder pasteurized 95 mL HM samples were inoculated with Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853), Serratia marcescens (Smarc 00697), two different strains of Klebsiella pneumoniae (ATCC 700603 and Kpn 01605) or spiked with 2 x 105 50% tissue culture infective dose of CMV (AD169) and subsequently subjected to HoP (62.5°C/30 min) or HTST treatment (62°C/5s, 62°C/15s, 72°C/5s, 72°C/15s, 87°C/2s and 87°C/5s). Bacterial count was determined after treated HM was cultured for 24h. CMV infectivity was determined by the number of specific CMV immediate early antigen stained nuclei after inoculating human fibroblasts with appropriately prepared HM samples.

Results: Holder pasteurized samples revealed no growth after 24h incubation. Viable bacterial cultures were retrieved from all tested strains after HTST treatment with the default HTST protocol (62°C/5s) that is available for clinical use. Using other time-temperature combinations, growth rates of S. aureus, E. faecalis, P. aeruginosa, K. pneumoniae, K. pneumoniae and S. marcescens were depending on treatment time, treatment temperature, bacterial genera and strain. Only after treatment temperatures above 72°C no bacterial growth was observed. CMV was inactivated by any tested time-temperature combination.

Conclusions: HTST treatment inactivates CMV in 95 mL HM samples but is less effective than HoP in bacterial count reduction at a time-temperature combination of 61°C/5s. For a reliable bacterial count reduction HTST treatment at 87°C was required in this study.

Keywords: Cytomegalovirus, Holder pasteurisation, preterm infant, High-temperature short-time, Pasteurization, HTST treatment, Bacteria, human milk

Received: 31 Aug 2018; Accepted: 05 Nov 2018.

Edited by:

Guido E. Moro, Associazione Italiana delle Banche del Latte Umano Donato (AIBLUD), Italy

Reviewed by:

Joseph M. Bliss, Women & Infants Hospital of Rhode Island, United States
David Lembo, Università degli Studi di Torino, Italy  

Copyright: © 2018 Klotz, Schreiner, Falcone, Jonas, Kunze, Weber, Fuchs and Hentschel. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Daniel Klotz, Department of Neonatology and Neonatal Intensive Care, Faculty of Medicine, University of Freiburg, Freiburg, 79106, Germany,