Catheter-associated Nocardia higoensis bacteremia in a child with acute lymphocytic leukemia

Molecular identification of Nocardia species causing endophthalmitis using multilocus sequence analysis (MLSA): a 10-year perspective

Introduction. Nocardia spp. can cause several ocular infections, such as keratitis, endophthalmitis and scleral abscesses. Molecular identification of Nocardia spp. by 16S rDNA sequencing is the gold standard method at present for species identification, but closely related species can only be identified by multilocus sequence analysis (MLSA) of housekeeping genes.Aim. The major objective was to profile Nocardia species, antibiotic susceptibility patterns and clinical outcomes in endophthalmitis patients.Methodology. Between January 2009 and December 2018, endophthalmitis patients who were diagnosed with Nocardia infection based on microscopic and culture characteristics were selected. Antibacterial susceptibility tests were performed and Nocardia speciation was performed using MLSA and phylogenetic tree analysis of the 16 s rRNA gene and the gyrB, hsp65 and secA1 genes.Results. A total of 43 culture-proven patients were identified during the study period. All isolates were 100 % sensitive to amikacin and 98 % resistant to ceftazidime. Fluoroquinolone sensitivity was observed in the range of 58 to 72 %. Year-wise analysis of antibiotic resistance patterns revealed there was a significant increase in resistance to fluoroquinolones. Twenty-two isolates were stored and six different species were identified. Nocardia farcinica (n=10) was found to be the most predominant, followed by Nocardia cyriacigeorgica (n=4), Nocardia otitidiscaviarum (n=3), Nocardia amikacinitolerans (n=2), Nocardia puris (n=2) and Nocardia higoensis (n=1).Conclusions. N. farcinica is the major pathogen, and this is the first report to identify N. otitidiscaviarum, N. amikacinitolerans and N. higoensis as causing endophthalmitis. Overall, visual outcomes were mostly poor even after aggressive management.

Nocardia bacteremia: A single-center retrospective review and a systematic review of the literature

OBJECTIVES

Nocardia bacteremia is a rare but severe disease associated with high mortality. This systematic review is the largest and most comprehensive review performed over the past 20 years.

METHODS

A single-center retrospective review of Nocardia bacteremia was performed using hospital microbiology records from January 1, 2010 to December 31, 2017. A systematic literature review was also performed to identify cases of Nocardia bacteremia described in the NCBI PubMed database in English between January 1, 1999 and December 31, 2018.

RESULTS

Four new cases of Nocardia bacteremia are described. The systematic review identified 134 cases with sufficient information available for analysis. Of the total 138 cases, the median age was 58 years (interquartile range (IQR) 44-69 years) and 70% were male. Eighty-one percent were immunocompromised (corticosteroid use (49%), hematological malignancy (20%), solid organ transplant (20%), solid organ malignancy (19%), and hematopoietic stem cell transplantation (15%)) and 29% had endovascular devices. Pulmonary infection was the most common concurrent site of clinical disease (67%). The median incubation time to the detection of Nocardia bacteremia was 4 days (IQR 3-6 days). Blood cultures were the only positive microbiological specimen in 38% of cases. The median total duration of treatment was 75 days (IQR 25-182 days). Thirty-day all-cause mortality was 28% and overall all-cause mortality was 40%.

CONCLUSIONS

Nocardia bacteremia is most frequently identified in immunocompromised patients and those with intravascular devices. Although rare, it represents a serious infection with high associated overall mortality.

Lack of Additional Diagnostic Yield of 16s rRNA Gene PCR for Prosthetic Joint Infections

INTRODUCTION

Medical management of prosthetic joint infections (PJIs) relies on the identification of causative organisms through traditional culture-based approaches to guide therapy. However, diagnosis of many PJIs remains challenging, with many clinically apparent infections remaining culture-negative. Molecular diagnostics have the potential to increase diagnostic yield, particularly among culture-negative PJIs.

METHODS

Bone, tissue, or synovial fluid from patients with clinically identified PJIs were collected for inclusion in this study. Samples were assessed with traditional cultures and classified as culture-positive or -negative after 48 h. Samples subsequently underwent a Staphylococcus aureus-/Kingella kingae-specific PCR followed by a 16s rRNA gene PCR.

RESULTS

A total of 77 unique patients with clinically identified PJIs contributed a total of 89 samples for inclusion in the study. There were 54 culture-negative and 35 culture-positive samples evaluated. The sensitivity and specificity of S. aureus PCR in culture-positive samples was 57.1% (95% CI, 34.1%-78.1%) and 92.9% (95% CI, 66.1%-98.9%), respectively. Among culture-positive samples, 16s rRNA gene PCR correctly identified 3 of 21 (14.3%) samples with S. aureus and 2 of 5 (40%) samples with Streptococcus spp. All molecular tests were negative in those with clinically identified, culture-negative PJI.

CONCLUSIONS

Our study suggests that these diagnostic tools have a limited role in PJI diagnosis.

Nocardiosis from 1888 to 2017

The genus Nocardia is an aerobic bacterium, Gram-positive and catalase positive that is in Nocardiaceae family. This bacterium first described by Edmond Nocard in 1888 and is not in human commensal bacteria. To date, nocardiosis incidence is increasing due to increase population growth rate, increase in patients with immune disorder diseases and immunocompromised patients. We surveyed taxonomic position, isolation methods, phenotypic and molecular identification at the genus and species levels, antibiogram, treatment and epidemiology in the world from 1888 to 2017.

Chronic lower extremity wound infection due to Kerstersia gyiorum in a patient with Buerger's disease: a case report

Background

Kerstersia gyiorum is an extremely rare pathogen of human infection. It can cause chronic infection in patients with underlying conditions. It can easily be misdiagnosed if proper diagnostic methods are not used.

Case presentation

A 47-year-old male patient with a history of Buerger’s Disease for 28 years presented to our hospital with an infected chronic wound on foot. The wound was debrided, and the specimen was sent to Microbiology laboratory. Gram staining of the specimen showed abundant polymorphonuclear leukocytes and gram-negative bacilli. Four types of colonies were isolated on blood agar. These were identified as Kerstersia gyiorum, Proteus vulgaris, Enterobacter cloacae, Morganella morganii by Maldi Biotyper (Bruker Daltonics, Germany). The identification of K. gyiorum was confirmed by 16S ribosomal RNA gene sequencing. The patient was successfully recovered with antimicrobial therapy, surgical debridement, and skin grafting.

Conclusions

This is the first case of wound infection due to K. gyiorum in a patient with Buerger’s Disease. We made a brief review of K. gyiorum cases up to date. Also, this case is presented to draw attention to the use of new and advanced methods like MALDI-TOF MS and 16S rRNA gene sequencing for identification of rarely isolated species from clinical specimens of patients with chronic infections and with chronic underlying conditions.

Kerstersia gyiorum Isolated from a Bronchoalveolar Lavage in a Patient with a Chronic Tracheostomy

The use of the matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) generates rapid microbial identification. We are presenting a case of a 63-year-old woman with a medical history of chronic tracheostomy admitted for hypotension and fevers to illustrate the clinical implication of MALDI-TOF MS on bacterial identification. Kerstersia gyiorum was identified from the bronchoalveolar lavage isolate. Kerstersia gyiorum has been isolated from human sputum samples, and may be a previously unrecognized colonizer of the upper respiratory tract. Thus, patients with long-term tracheotomies or who are chronically aspirating may be at risk of lower respiratory infection with this organism. Increased use of MALDI-TOF MS in the clinical setting may increase reporting of this atypical isolate.

Two cases of Kerstersia gyiorum isolated from sites of chronic infection

Kerstersia gyiorum is infrequently associated with human infection. We report the isolation of Kerstersia gyiorum from two patients: the first, a patient with chronic ear infections, and the second, a patient with a chronic leg wound. Both isolates were resistant to ciprofloxacin, which has not been previously reported.

Optimizing identification of clinically relevant Gram-positive organisms by use of the Bruker Biotyper matrix-assisted laser desorption ionization-time of flight mass spectrometry system

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) can be used as a method for the rapid identification of microorganisms. This study evaluated the Bruker Biotyper (MALDI-TOF MS) system for the identification of clinically relevant Gram-positive organisms. We tested 239 aerobic Gram-positive organisms isolated from clinical specimens. We evaluated 4 direct-smear methods, including "heavy" (H) and "light" (L) smears, with and without a 1-μl direct formic acid (FA) overlay. The quality measure assigned to a MALDI-TOF MS identification is a numerical value or "score." We found that a heavy smear with a formic acid overlay (H+FA) produced optimal MALDI-TOF MS identification scores and the highest percentage of correctly identified organisms. Using a score of ≥2.0, we identified 183 of the 239 isolates (76.6%) to the genus level, and of the 181 isolates resolved to the species level, 141 isolates (77.9%) were correctly identified. To maximize the number of correct identifications while minimizing misidentifications, the data were analyzed using a score of ≥1.7 for genus- and species-level identification. Using this score, 220 of the 239 isolates (92.1%) were identified to the genus level, and of the 181 isolates resolved to the species level, 167 isolates (92.2%) could be assigned an accurate species identification. We also evaluated a subset of isolates for preanalytic factors that might influence MALDI-TOF MS identification. Frequent subcultures increased the number of unidentified isolates. Incubation temperatures and subcultures of the media did not alter the rate of identification. These data define the ideal bacterial preparation, identification score, and medium conditions for optimal identification of Gram-positive bacteria by use of MALDI-TOF MS.

Optimization of routine identification of clinically relevant Gram-negative bacteria by use of matrix-assisted laser desorption ionization-time of flight mass spectrometry and the Bruker Biotyper

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) might complement and one day replace phenotypic identification of bacteria in the clinical microbiology laboratory, but there is no consensus standard regarding the requirements for its validation prior to clinical use in the United States. The objective of this study was to assess the preanalytical variables influencing Gram-negative identification by use of the Bruker Biotyper MALDI-TOF MS system, including density of organism spotting on a stainless steel target plate and the direct overlay of organisms with formic acid. A heavy smear with formic acid overlay was either superior or equivalent to alternative smear conditions. Microbiological preanalytical variables were also assayed, such as culture medium, growth temperature, and use of serial subculture. Postanalytical analysis included the application of modified species-level identification acceptance criteria. Biotyper identifications were compared with those using traditional phenotypic methods, and discrepancies were resolved with 16S rRNA gene sequencing. Compared to the recommended score cutoffs of the manufacturer, the application of optimized Biotyper score cutoffs for species-level identification increased the rate of identification by 6.75% for the enteric Gram-negative bacteria and 4.25% for the nonfermenting Gram-negative bacteria. Various incubation temperatures, growth medium types, and repeat subcultures did not result in misidentification. We conclude that the Bruker MALDI Biotyper is a robust system for the identification of Gram-negative organisms in the clinical laboratory and that meaningful performance improvements can be made by implementing simple pre- and postanalytical techniques.