First report of neonatal bacteraemia caused by bla_NDM-1Raoultella ornithinolytica

Abstract

Raoultella ornitholytica, an environmental organism, has only recently been reported as a cause of infections in humans, and is associated mainly with bacteraemia in elderly patients. Carbapenem resistance is unusual in Raoultella spp. We describe the first paediatric case of bla_NDM-1 Raoultella ornitholytica bacteraemia in a preterm neonate that developed three days after hospitalisation. This case report discusses a rare organism that had an unexpected susceptibility profile and caused bacteraemia in a neonate. Treatment options are explored.

Keywords:

• bacteraemia
• bla_NDM-1
• carbapenemase
• neonate
• Raoultella ornithinolytica

Introduction

Raoultella spp are usually found in aquatic environments, were originally categorised within the genus Klebsiella and, following DNA-DNA hydridisation studies and sequence analysis of the 16S rRNA gene, K. planticola and K. ornitholytica were moved into a separate genus, Raoultella.¹ R. planticola comprised about 9% of Klebsiella spp isolated from rectal and oropharyngeal swabs in a neonatal ward.² R. ornitholytica is an unusual human pathogen that is mainly associated with bacteraemia in adults and is a rare cause of infections in neonates.^3–8

We describe the first neonate with bacteraemia caused by bla_NDM-1 Raoultella ornitholytica, which has only recently been detected in pus from adults.^9,10 To date, carbapenem resistance has not been reported in paediatric isolates of R. ornitholytica.

Case report

A preterm baby born at 33 weeks via a Caesarean section was admitted three days after birth to the neonatal unit at a tertiary hospital in Durban, South Africa, for ventilation due to hyaline membrane disease. His birth weight was 1.78 kg and the Apgar scores were 7 and 8 after one and five minutes, respectively. He received penicillin and gentamicin for three days at a local hospital and, on arrival at the unit, piperacillin/tazobactam plus amikacin was commenced. The septic markers on admission were as follows: white cell count 4.82 x 10⁹ cells/L; neutrophil count 3.66 x 10⁹ cells/L; C-reactive protein 28 mg/L; and procalcitonin 9.92 µg/L. The blood culture taken on admission flagged positive on the Bactec automated blood culture system (bioMérieux SA, France). After overnight incubation, mucoid lactose-fermenting colonies resembling Klebsiella spp were isolated. These were identified as Raoultella ornitholytica using matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (bioMérieux SA, France). The Vitek 2 AST N255 card (bioMérieux SA, France) was used for susceptibility testing of the isolate that demonstrated resistance to all beta-lactams and aminoglycosides tested (Table 1). The isolate was susceptible to ciprofloxacin, colistin and tigecycline. Ciprofloxacin was commenced two days later when the susceptibility results were available. DNA was extracted from the phenotypically carbapenem-resistant isolate using a crude extraction method and screened for bla_NDM-1, bla_KPC, bla_OXA-48 and its variants, bla_GES, bla_IMP and bla_VIM, using multiplex real-time polymerase chain reaction (PCR) (LightCycler 480 II (Roche Applied Science, USA), LightCycler 480 Probes master kit (Roche Diagnostics, USA) and the individual LightMix modular kits (Roche Diagnostics, USA)) were used as per manufacturer’s instructions. The PCR confirmed the presence of bla_NDM-1. The patient was extubated eight days after admission and transferred back to the base hospital on ciprofloxacin. The significance of this isolate was unclear and we were unable to find a focus for the organism. It is possible that this may have been a contaminant, but as the patient was clinically septic at the time of the culture, the organism was thought to be significant and treatment was commenced. There was no epidemiological link to other patients with infections caused by organisms harbouring bla_NDM-1.

Table 1: Antibiogram of Raoultella ornithinolytica

Antimicrobial agent	MIC (μg/ml)
Ampicillin	≥32
Amoxicillin/clavulanic acid	≥32
Piperacillin/tazobactam	≥128
Cefuroxime	≥64
Cefoxitin	≥64
Cefotaxime	≥64
Ceftazidime	≥64
Imipenem	≥16
Meropenem	≥16
Amikacin	≥64
Gentamicin	≥16
Ciprofloxacin	1
Tigecycline	2
Colistin	≤0.5
Trimethoprim/sulfamethoxazole	≥320

Discussion

R. ornitholytica has only recently been described as a human pathogen with most infections occurring in adults.^3–5,9,10 The most common infection caused by R. ornitholytica is bacteraemia. A review of cases of bacteraemia found that most patients were elderly or had biliary tract disease.^3–5 Apart from bacteraemia, R. ornitholytica has also caused urinary tract, skin and soft tissue infections, as well as pyrexia of unknown origin and enteric disease.^8–14

Three cases of R. ornitholytica infections in children, two of which occurred in neonates, have been published.^6–8 Mau et al. reported that a neonate who presented with heterotaxy and asplenia had R. ornitholytica isolated from blood culture. The patient was commenced on meropenem and amikacin, and subsequently improved.⁶ The second neonate was a preterm baby who developed severe sepsis and purpura fulminans. R. ornitholytica was isolated from a blood culture and despite being treated with meropenem, the patient demised.⁷ Sener et al. described a 16 month old patient with fever of unknown origin in whom R. ornitholytica was isolated from broncho-alveolar lavage fluid. The child recovered after treatment with aminopenicillin plus clavulanate.⁸ In all these cases, skin manifestations were present which were described as skin flushing and urticarial plaques, which are thought to be due to histamine release. These findings were absent in our patient. Furthermore, all these isolates were susceptible to carbapenems while our isolate was resistant.

Raoultella spp are often susceptible to most beta-lactam agents, however isolates that produce extended-spectrum beta-lactamases and carbapenemases have emerged.^9,10,14–17 In 2009, Castenheira et al. first described two cases of R. planticola and one case of R. ornitholytica containing bla_KPC-2 and bla_KPC-3 from a surveillance study conducted in USA.¹⁴ Khajuria et al. reported a case of R. ornitholytica which carried bla_NDM-1 gene that caused a surgical site infection.⁹ The patient recovered after treatment with tigecycline. Recently, Zhou et al. conducted a retrospective analysis of carbapenem resistant Enterobacteriacae in China and detected bla_NDM-1 gene in R. ornitholytica isolated from an abscess.¹⁰ In both these cases of bla_NDM-1 R. ornitholytica, the organism was isolated 48-72 h after hospitalisation, which is in keeping with our case.

The optimal treatment of carbapenemase-producing Enterobacteriacae is unclear. Current recommendations include combination regimens that are either carbapenem-containing or carbapenem-sparing, based on carbapenem MICs.^18,19 Prolonged carbapenem infusion with aminoglycosides, tigecycline or quinolones is suggested for organisms that have carbapenem MICs ≤ 8 µg/ml. If carbapenem MICs are higher, then colistin should be combined with aminoglycosides, tigecycline or quinolones based on susceptibility. Combination therapy is advised because lower mortality rates were observed compared to colistin monotherapy in small retrospective studies.^18,19 It is postulated that colistin monotherapy results in selection for resistance and bacterial regrowth.^18,19

Identification of Raoultella spp may be problematic. They need to be differentiated from Klebsiella spp, especially K. oxytoca with which there is much similarity. Furthermore, differentiation of R. planticola from R. orthinolytica is often difficult in a routine microbiology laboratory. Conventional biochemical testing using API-20E strip (bioMérieux, France) and Vitek 2 (bioMérieux, France) has been used by authors previously.^6,9,13 Vitek 2 correctly identified four R. ornithinolytica isolates during an evaluation of the Gram-negative card.²⁰ Park et al. found that Vitek 2 also compared well with sequence-specific primer PCR, while API-20E needed additional confirmatory testing.²¹ Walckenaer et al. described amplification of the bla gene as a reliable tool for identification of Raoultella spp.²² Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry has been shown to differentiate R. ornithinolytica/planticola and K. oxytoca,²³ which we also used to identify the isolate. A possible limitation of our report is that we did not use 16S rRNA sequencing, which is not widely available at our institution, to confirm the identification of the isolate.

We describe the first case of bla_NDM-1 Raoultella ornitholytica in a neonate. This case highlights both an unusual organism causing neonatal bacteraemia, and an unexpected susceptibility profile of the isolate.

Notes

Presented at 6th FIDSSA congress, Drakensberg, South Africa, 5–8 November 2015.