Epidemiology of Cronobacter spp. isolates from patients admitted to the Olomouc University Hospital (Czech Republic)

Summary

The data on the incidence of Cronobacter spp. was collated from hospital records for the seven-year period 2005–2011. The majority of Cronobacter spp. isolates (n = 91) were from throat swabs (61), followed by urine (5), tracheal aspirates (5), bronchoalveolar lavage (4), cannulae (4), and sputum (3) samples. This is the first study which profiles the carriage of Cronobacter spp. according to patient age, based on seven years of clinical data from 2005–2011. It reveals a high recovery (63.7% of strains, n = 91) of the organism from children, 1–14 years in age.

Keywords:
Cronobacter spp. – meningitis – nosocomial infection

INTRODUCTION

In recent years Cronobacter spp. has attracted considerable attention due to severe, though rare, neonatal infections [1–3]. Many of these cases have been attributed to contaminated reconstituted infant formula [4]. Subsequently, the FAO/WHO held three risk assessments (2004, 2006, 2008) to consider control measures for neonatal exposure to Cronobacter through formula ingestion. In addition, the FAO/WHO reported that the majority of Cronobacter spp. infections (ie. bacteraemia) were in the adult population [5]. This statement was based on data from the Health Protection Agency for England and Wales submitted to the FAO/WHO following their ‘call for data’ [5]. However no comparable surveillance data for the bacterium has been published. This communication is the first to report an age profile for Cronobacter spp.

METHODS

The University Hospital Olomouc (Czech Republic) receives 45,831 patients per year in average and 776,000 outpatients per year from a catchment population size of 1,000,000. Department of Microbiology conducts microbiological examination for University Hospital Olomouc. Biological samples for bacteriological monitoring, depending on the patient’s condition, are sent once or twice a week. Microbiological samples are processed by accredited methods CIA (Czech Accreditation Institute). The first sample, identified as Cronobacter was included.

The incidence of Cronobacter spp. isolation was collated from hospital records for the seven year period 2005–2011 (Table 1). The isolates had been identified using the BD Phoenix^TM automated microbiological system which uses 45 phenotypic characters to identify bacterial cultures. Substrates for biochemical tests: sorbitol, methyl-beta-glucoside and esculin were positive, while adonitol was negative. The above are main biochemical tests distinguishing E. sakazakii strain from E. cloacae strain [6]. Antibiotic sensitivity of the strains was determined according to minimal inhibitory concentrations (MIC). The antibiotics tested were for Gram-negative bacteria (ATB I and II line) as given by Trios (Czech Republic). The standard microdiluting method was used [7]; the susceptibility was assessed in Mueller-Hinton broth. To establish antibiotic sensitivity, a set for determining minimal inhibitory concentrations (MIC) by means of a standard micro method in a microtiter plate was used. The majority of Cronobacter isolates (n = 91) were from throat swabs (61), followed by urine (5), tracheal aspirates (5), bronchoalveolar lavage (4), cannulae (4), and sputum (3) samples, as shown in the Table 2. These samples had been taken for general screening purposes, and not specifically according to the patient clinical presentation. Nevertheless, isolates taken from immune-deficient paediatric patients, the isolation of any microorganism particularly from sputum, bronchoalveolar lavage and indwelling cannulae could be of high clinical significance. Such additional strains had been isolated from clinical investigations (see Tables 1 and 2).

RESULTS

In the seven year period there had been a total of 61 Cronobacter spp. isolations from the general screening of patients, and an additional 30 isolates from normally sterile sites such as blood, which had been sampled as part of a clinical investigation. The strains were identified as Cronobacter spp. at the 99% confidence level. All strains were sensitive to therapeutic antibiotics. There was considerable yearly variation (2–15/y) in the number of Cronobacter isolations from screened patiens (see Table 1). There were nearly an equal number of Cronobacter spp. isolates from patients on the general wards (49.5%), as there were from intensive care units (45.1%), the remainder were from outpatients (4.4%) and from pathological investigations (1.1%). As shown in Table 1, Cronobacter spp. was isolated from all age groups. The highest incidences was in the age groups < 1 year (8.7/1000 patients) and 1–4 years (8.2/1000 patients) (see Table 1), and the majority of the strains were isolated in the age group below 14 years of age (63.7%). This corresponds with the majority of isolates being from the Department of Pediatrics (57), followed by Department of Neonatology (6), Department of Internal Medicine (5) and Department of Respiratory Medicine (5). Most of the (44%) Cronobacter spp. strains were from patients with immunodeficiency (i.e. acute lymphoblastic leukaemia, acute myeloblastic leukaemia, lymphoid leukaemia).

DISCUSSION

Surprisingly despite the raised awareness of Cronobacter spp. since 2002, there is no comparable data on its carriage by different age groups. The only age profiled data, known to the authors, is for 819 Cronobacter spp. bacteraemia cases reported for England and Wales between 1992 and 2007, as given by FAO/WHO [5]. In their report, the majority (91%) of bacteraemia cases were patients >15 years in age. The wide age range for the recovery of Cronobacter spp. is not surprising given the numerous possible routes of exposure. Cronobacter spp. is present in water, soil, households, flies, fresh and processed foods [8–11]. The severity of Cronobacter spp. infections in premature neonates is probably due to their immune-compromised status, whereas older children and adults may carry the organism as part of their normal flora. Routes of infections (ie. bacteraemia) in non-infants are uncertain, but are probably following a lowering of their immune status, and puncture wounds. Although the bacterium is isolated from many foods, no foodborne infections have not been reported to date. The data compiled here demonstrates that further research is needed to clarify the asymptomatic carriage of Cronobacter spp. This is of particular concern, as it is plausible that inadequate hygienic practices in the preparation of infant feed may lead to infant infection. The recent recognition of Cronobacter infections in the healthcare setting has shown that C. malonaticus is more associated with adult infec­tions, as opposed to C. sakazakii which predominates infant infections [12]. Subsequently the strains collected over the 2005–2011 period from known age groups, are currently undergoing further microbiological analysis.

CONCLUSIONS

The majority of Cronobacter spp. isolates (n = 91) were from throat swabs (61), followed by urine (5), tracheal aspirates (5), bronchoalveolar lavage (4), cannulae (4), and sputum (3) samples. These had been taken for general screening purposes, and not specifically according to the patient clinical presentation. This is the first study which profiles the carriage of Cronobacter spp. according to patient age, based on seven years of clinical data from 2005–2011. It reveals a high recovery (63.7% strains, n = 91) of the organism from children, 1–14 years in age.

Acknowledgement: This project was supported by Research Support Foundation, Vaduz, grant project [801100021/39].

Do redakce došlo dne 29. 7. 2013.

Address for correspondence:

Stephen Forsythe

School of Science and Technology

Nottingham Trent University

Clifton Lane, Nottingham

NG11 8NS, UK

email: stephen.forsythe@ntu.ac.uk

Address for correspondence:

Ondřej Holý

Department of Preventive Medicine

Faculty of Medicine and Dentistry

Palacký University Olomouc

Olomouc

Czech Republic

email: holy.ondrej@seznam.cz