|Year : 2016 | Volume
| Issue : 2 | Page : 131-133
Nosocomial bloodstream infection caused by Pseudomonas alcaligenes in a preterm neonate from Mérida, Venezuela
Ana Flores-Carrero1, Alberto Paniz-Mondolfi2, María Araque3
1 Institute of Welfare and Social Assistance Ministry of Education (IPASME); Electron Microscopy Center, University of Los Andes, Merida, Venezuela
2 Department of Laboratory Medicine, Yale School of Medicine/Yale-New Haven Hospital, New Haven, Connecticut, USA
3 Department of Microbiology and Parasitology, Laboratory Molecular Microbiology, Faculty of Pharmacy and Bioanalysis, University of Los Andes, Merida 5101, Venezuela
|Date of Web Publication||8-Apr-2016|
Laboratorio de Microbiología Molecular, Facultad de Farmacia y Bioanálisis, Universidad de Los Andes, Mérida 5101
Source of Support: None, Conflict of Interest: None
Pseudomonas alcaligenes is a nonfermenting Gram-negative bacillus and an unusual human pathogen belonging to the family Pseudomonadaceae. We describe the first case of a P. alcaligenes bloodstream infection in a premature neonate born at 33 weeks of gestation, who presented severe respiratory distress and was admitted to the Neonatal Intensive Care Unit at The Andes University Hospital in Mιrida, Venezuela. The strain was identified as P. alcaligenes by the matrix-assisted laser desorption ionization-time of flight mass spectrometry and 16S rRNA gene analysis. Antimicrobial susceptibility testing was carried out by E-test and broth microdilution methods. The isolate was resistant to ί-lactam/ί-lactamase inhibitor combinations, aztreonam, extended-spectrum cephalosporins, and gentamicin, but remained susceptible to carbapenems, fluoroquinolones, tobramycin, amikacin, minocycline, trimethoprim/sulfamethoxazole, and colistin. The neonate was successfully treated with meropenem. This case highlights the importance of P. alcaligenes as an emerging nosocomial neonatal pathogen.
Keywords: 16S rRNA analysis, bloodstream infection, neonate, matrix-assisted laser desorption ionization-time of flight MS, Pseudomonas alcaligenes
|How to cite this article:|
Flores-Carrero A, Paniz-Mondolfi A, Araque M. Nosocomial bloodstream infection caused by Pseudomonas alcaligenes in a preterm neonate from Mérida, Venezuela. J Clin Neonatol 2016;5:131-3
|How to cite this URL:|
Flores-Carrero A, Paniz-Mondolfi A, Araque M. Nosocomial bloodstream infection caused by Pseudomonas alcaligenes in a preterm neonate from Mérida, Venezuela. J Clin Neonatol [serial online] 2016 [cited 2019 Dec 5];5:131-3. Available from: http://www.jcnonweb.com/text.asp?2016/5/2/131/179932
| Introduction|| |
Pseudomonas alcaligenes is an ubiquitous environmental bacterium and a rare opportunistic human pathogen. To date, little is known about its clinical significance, mainly due to difficulties in identifying and distinguishing this bacterium from other closely related Pseudomonas species in clinical settings.  According to phylogenetic affiliations of the pseudomonads and 16S rRNA gene sequence analysis, P. alcaligenes was placed in the Pseudomonas aeruginosa group.  Here, we describe the first case of a P. alcaligenes nosocomial bloodstream infection, a very uncommon neonatal pathogen, in a preterm neonate.
| Case Report|| |
A 36-year-old multigravida was admitted to the hospital because of the sudden onset of premature rupture of membranes at 33 weeks of gestation. The male neonate was born by spontaneous vaginal delivery and weighed 1760 g at birth. He presented severe respiratory distress, with Apgar scores of 6 and 8 at 1 min and 5 min, respectively, and was admitted to the Neonatal Intensive Care Unit (NICU) at The Andes University Hospital in Mérida, Venezuela on June 2014 with poor respiratory effort, requiring immediate intubation, and mechanical ventilatory support. The baby was closely monitored and kept in an incubator with proper intravenous fluids and parenteral nutrition. Empirical therapy with intravenous ampicillin and gentamicin was started. Peripheral blood and tracheal secretion aspirate cultures drawn at admission returned negative. However, after 3 days on assisted ventilation, the patient's clinical condition worsened.
Laboratory results revealed anemia (9.9g/dl) and thrombocytopenia (70.000 mm 3 ). Screening for sepsis was positive, with a total leukocyte count of 8500 mm 3 , a C-reactive protein of 74.7 mg/dl, and procalcitonin of 10.4 mg/dl. Blood, cerebrospinal fluid, urine, and feces samples were collected for cultures. All cultures were negative except for the blood cultures, which after 2 days grew P. alcaligenes.
The strain (LMM-14249/2) was recovered in BacT/ALERT 3D 60 (BioMérieux, Marcy-l'Etoile, France) culture vials and subcultured on 5% of sheep blood agar (BBL, Becton Dickinson, Cockeysville, MD, USA), and MacConkey agar (BBL). Gram stains revealed the presence of Gram-negative aerobic rods. The isolate was at the time identified as Pseudomonas mendocina by VITEK 2 systems (BioMérieux) with an apparent "good" confidence score (90%). However, reidentification of the isolate by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (VITEK MS MALDI-TOF, BioMérieux) reported P. alcaligenes (99.9% score identifier). To clarify these discordant results and confirm to the identification of LMM-14249/2, we used 16S rRNA gene sequencing using the MicroSeq 500 16rDNA bacterial identification kit (Applied Biosystems, Carlsbad, CA, USA), which confirmed the identification of our strain as P. alcaligenes. The sequence obtained showed an identity of 99.19% with the strain of P. alcaligenes IAM12411 T deposited in the GenBank nucleotide database (accession no. D84006).
Susceptibility testing, carried out with E-test and broth microdilution method according to the Clinical and Laboratory Standards Institute guidelines,  revealed that LMM-14249/2 was resistant to ß-lactam/ß-lactamase inhibitor combinations, aztreonam, extended-spectrum cephalosporins, and gentamicin, but remained susceptible to carbapenems, fluoroquinolones, tobramycin, amikacin, minocycline, trimethoprim/sulfamethoxazole, and colistin [Table 1].
|Table 1: Antibiotic susceptibility patterns of Pseudomonas alcaligenes LMM-14249/2 isolated from preterm neonate from Mérida, Venezuela |
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| Discussion|| |
Nonfermenting Gram-negative bacilli (NFGNB) have emerged as an important health care-associated pathogens, which substantially contribute to increase the morbidity and mortality in critically ill neonates.  P. alcaligenes is an emergent little known NFGNB pathogen.  In the literature, only three reports describe this bacterium as a cause of nosocomial infection in adult patients. ,, This is the first report of bloodstream infection by P. alcaligenes in a preterm neonate.
Neonates admitted to NICU are highly prone to develop invasive infections, mostly due to the presence of several unavoidable risk factors.  In our case, besides preterm birth, the baby had other predisposing factors for the development of systemic infections, which included the long-term use of invasive interventions such as mechanical ventilation and intravascular catheterization, the failure of early enteral feeding with breast milk, a prolonged duration of parenteral nutrition and an underlying respiratory deficiency. Previous studies indicate that the survival rates of the neonate in NICUs have increased in recent years mainly due to technological advancements; however, prolonged hospital stay and invasive procedures have raised the risk of nosocomial infections, , a possible scenario that most likely could have played a role in this case.
One of the major difficulties in the management of neonatal sepsis is getting an accurate diagnosis. Blood culture remains as the definitive diagnostic tool for neonatal sepsis.  However, distinguishing among NFGNB using manual and automated commercial identification systems is often challenging.  In this study, the VITEK 2 system did not allow a reliable identification of P. alcaligenes due to the limited species diversity of the database for NFGNB. In contrast, the use of VITEK MS MALDI-TOF and/or 16S rRNA gene analysis to obtain an accurate identification of P. alcaligenes was adequate. Few data are currently available on the antimicrobial susceptibility of this bacterium. However, a recent study reported a subclass B3 metallo-β-lactamase in a P. alcaligenes isolated from bloodstream infection in an adult patient in Japan.  In our case, the strain was susceptible to several antimicrobial including carbapenems. The baby was successfully treated with meropenem. Follow-up blood cultures were requested, and results thereafter were negative.
P. alcaligenes is mainly isolated from environmental sources. , In this case, the source infection was not identified; we suspect that a nosocomial acquisition through indirect neonatal contact occurred, possibly by hand colonization of health-care personnel. Therefore, the importance of hand washing and compliance with guidelines for preventing nosocomial infections were reinforced at the time this case was studied. We stress the importance of infection control programs, based on active surveillance, and also of strict adherence to equipment decontamination, use of disposable gowns and gloves to prevent infections due to emerging pathogens as P. alcaligenes.
| Conclusion|| |
This case highlights the importance of P. alcaligenes as an emerging nosocomial neonatal pathogen. The use of new laboratory platforms such as the VITEK MS MALDI-TOF and/or 16S rRNA gene analysis significantly helped in reducing delays in species identification. Furthermore, the availability of rapid antimicrobial susceptibility results allowed early initiation of an appropriate therapy, thus diminishing the risk of mortality.
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Conflicts of interest
There are no conflicts of interest.
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