Newborns colonized in Borgo Trento, confirmation: it is still Citrobacter koseri

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It came from the Microbiology laboratory of the Fondazione Policlinico Gemelli IRCSS the anticipation of the genomic investigation on the microorganism responsible for colonization in neonatal intensive care (Tin) at the Women’s and Children’s Hospital in Borgo Trento. It is confirmed that it is Citrobacter koseri, as was already said last May 5, «a bacterium that is brother but not twin of the one that caused the epidemic in 2020. The investigation has in fact confirmed that they are very similar but not the same” says the press release fromIntegrated University Hospital of Verona.

Last May 5th the alarm was immediately raised when it was colonization of three newborns was detectedview what happened four years ago with Citrobacter koseri, when four children were killed by the bacterium and around ninety were infected, some with serious consequences. It has been ever since access to the NICU for pregnant women with possible premature birth has therefore been suspendedas Citrobacter koseri is particularly dangerous for premature newbornswho often require hospitalization in neonatal intensive care.

The Citrobacter case in Verona, among other things, will also be discussed in the tonight’s episode of Iene on Italia 1.

«As is known and as described in the scientific literature, this bacterium is ubiquitous in the sense that it is found everywhere and proliferates in the human and animal intestine. The colonization at the beginning of May is therefore due to a microorganism that may have arrived in the hospital through multiple routes since it is circulating everywhere. Its spread occurs only by contact and not by air, and it is a germ with low environmental resistance (it dies immediately on surfaces) and is sensitive to normal disinfectants” recalls the Hospital Company.

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After the 2020 cases, «the surveillance of strict internal protocols has always looked for the bacterium and for four years it was never found in the environment. Not even from early May to today, when after the identification of the bacterium in the surveillance swabs of the three premature babies without infection, extraordinary surveillance measures were triggered” continues the Aoui statement. «There is no trace of Citrobacter koseri in drinking water, neither from taps nor in waste siphons. There is no trace on the surfaces (sinks, cots, thermocots, electro-medical devices, etc.), and the samples have always been negative even on the air (in the remote hypothesis of vaporization)”.

Doctor Luca Brizzidirector of Hygiene and Risk Prevention, explains: «Total elimination of the Citrobacter koseri risk is in fact impossible to be pursued precisely because it is a ubiquitous microorganism. It is everywhere in people and in the world. The real obligation for a public health facility is to have one such detailed research and surveillance organization as to intervene promptly. And this is what happened at the beginning of May, when the company system produced an immediate response to the anomalous Microbiology data. We already had in place all the necessary measures to interrupt the chain of transmission, a level of surveillance that is not standard but which exists here and which we have further increased.”

The Professor Massimo Franchi, director of the Maternal and Child Department, adds: «It is good to remember that we are talking about the colonization of three newborns, who never got sick because the infection never developed. We cannot say that the bacterium is the same as in 2020 because it is very similar but not the same, so much so that in recent years it has never been found in any environmental matrix or in any patient.”

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Swabs on patients. Swabs on patients entering the NICU are usually performed to identify the bacteria that colonize premature newborns and do not only include Citrobacter koseri, but also other bacteria, for example Staphylococcus aureus, Klebsiella pneumoniae, or Pseudomonas aeruginosa, which can cause very serious and sometimes lethal infections.

«After the first ones three premature babies positive for intestinal swabs, all the newborns present in Tin tested negative and no other hospitalized patients were infected. All other swabs, which are carried out in other areas of the body, have always tested negative in all hospitalized patients. Swabs on pregnant women are by law on a voluntary basis and for this reason it is difficult to identify the source of the infection, since this bacterium is normally present in the human body in a harmless form but can be dangerous in fragile subjects such as premature babies” continues the press release from ‘Aoui.

The measures implemented. “There has been no case of transmission to other newborns because the company protocols envisaged in the case of anomalous swab results were immediately implemented” says the hospital. And on the other hand they were hospitalizations of pregnant women below the 33rd week of gestation were immediately suspendedsince premature births require hospitalization in the ICU in most cases.

These are the main measures: organizational activation (Hospital Infections Group and Hospital Infections Commission), activation of immediate extraordinary isolation, cleaning and disinfection procedures with higher concentrations of chlorine, reinforcement of vigilance with direct daily observation actions, in particular for: adherence to hand hygiene procedures, increase in the frequency of swabs in newborns, repetition of environmental sampling on different matrices (distributed water, formula milk), surfaces (heating cradles, medical devices and electro-medical equipment), sink drainage systems, also in light of the information collected with the epidemiological investigation and relating to the process of taking care of individual newborns (from the delivery room to intensive care).

READ ALSO: Newborns colonized in Borgo Trento, confirmation: it is still Citrobacter koseri

Data on neonatal intensive care. «Research for Citrobacter koseri has been carried out for 4 years in a radical way in the departments of the Women’s and Children’s Hospital, with organizational protocols that minimize the risk of infections of neonatal pathologies. The data from the national network in which the Borgo Trento Tin is also included confirm the effectiveness of the measures. The latest available data for 2022 shows that compared to 13.2% of infections in Italy, in Verona the risk stands at 3.2%” declare the Aoui.

New actions taken. «Even if all the water samples are negative, AOUI has opted for the implementation of cutting-edge preventive measures to reduce hospital infections, with the elimination of sinks near the beds in the Neonatal Intensive Care Unit. However, we would like to remind you that, prudentially, for years all newborns have been washed only with sterile water. Furthermore, since yesterday the information desk for women giving birth and their families has been in operation to obtain clinical and scientific information on the possibility of giving birth in Borgo Trento, above all to clarify the difference between colonization and infection” says the Aoui.

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Below is some information relating to Citrobacter from the Istituto Superiore di Sanità website.

To the genre Citrobacter belong to bacteria that can be found everywhere in the environment (ubiquitous), including water, and in foods. They are also a normal component of the intestinal bacterial flora. They can cause infections in vulnerable people (opportunistic pathogens) such as newborns (particularly premature ones), the elderly and immunocompromised individuals. In these subjects they can cause infections of the urinary tract, respiratory tract, wounds, bones (osteomyelitis), peritoneum, endocardium, meningitis and sepsis. The three main species that cause serious infections in humans are C. freundii, C. koseri And C. braakii.

Most of these infections are acquired in hospital (nosocomial infections), however, given the spread of the bacterium, one can also become infected outside the hospital. The most frequent modes of transmission are: through ingestion of contaminated food, from mother to child during childbirth, direct person-to-person contact, contact with contaminated surfaces or objects.

In hospital settings, transmission can also occur via:

  • contact with healthcare professionalsespecially through the hands if not properly washed and disinfected
  • indirect contact via objects or contaminated surfaces (both diagnostic tools and common objects and surfaces)


The disorders caused by infections from Citrobacter are closely linked to the affected organ:

  • redness, swelling, localized pain and pusin skin infections and in deep infections such as osteomyelitis
  • high fever, difficulty breathing, cough, sputum, weakness (asthenia) and deterioration of general conditionsin pneumonia
  • difficulty urinating, frequent urge to urinate (pollakiuria), urgency to urinate, pain when urinating (stranguria), pain in the pelvic and lower back region, blood in the urine (haematuria), purulent urine, feverin urinary infections
  • fever above 38°C, feeling of general malaise, muscle pain, chills and confusionin sepsis
  • lowering of blood pressure, in case of worsening of sepsis and septic shock
  • neonatal meningitis caused by C. koseria particularly severe form, generally associated with necrotizing encephalitis and brain abscesses


When an infection is suspected Citrobacter it is essential to ascertain (diagnose) the presence of bacteria in the body through different analyzes depending on the site of the infection:

Subsequent biochemical and molecular tests confirm the diagnosis and allow identification of the serogroup, a classification criterion which is based on the different proteins (O antigen) on the surface of the bacteria, and is useful for having a more precise diagnosis and for studying hospital epidemics.


For the treatment of infections Citrobacter the most appropriate antibiotic or combination of antibiotics is chosen based on the result of the susceptibility test. It is important to perform the antibiogram because the Citrobacter it is resistant to penicillins and various combinations of β-lactam antibiotics. Furthermore, there are bacterial strains resistant to multiple classes of antibiotics (multi-resistant), for which the only effective antibiotic is currently colistin. Colistin must be prescribed by the doctor who checks the general state of the patient and the possible onset of toxic effects during treatment.


Bacteria like that Citrobacter they cause serious infections and, sometimes, epidemics in hospital settings. In order to prevent and control the transmission of infections within hospitals, the following are important:

  • infection surveillance and the rapid identification and control of epidemics
  • infection prevention associated with specific procedures, reducing the execution of unnecessary ones and choosing safer medical devices
  • correct use of antibiotics and disinfectants
  • cleaning and disinfection of the environments
  • frequent and correct hand washing (read the hoax)

Correct hand washing is a very effective practice for preventing infections from Citrobacter and in general, and can be practiced by everyone both in hospital and outside, at home and at work.

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