Rhodococcus luteus and Rhodococcus erythropolis chronic endophthalmitis after lens implantation

Rhodococcus erythropolis septic arthritis

A woman in her 50s presented with a 4-day history of left knee pain, erythema, swelling as well as malaise and rigours 1 month after undergoing a left knee meniscectomy. She was diagnosed with left native knee septic arthritis and underwent arthroscopic irrigation and debridement of the knee; cultures from synovial tissue grew Rhodococcus erythropolis. Rhodococcus spp are soil-dwelling and livestock-dwelling bacteria which occasionally cause disease in immunocompromised hosts. Infection in immunocompetent hosts is rare, and septic arthritis secondary to Rhodococcus erythropolis has not been reported previously.

Specific preadaptations of Rhodococcus equi cooperate with its Virulence-associated protein A during macrophage infection

Gram-positive Rhodococcus equi (Prescotella equi) is a lung pathogen of foals and immunocompromised humans. Intra-macrophage multiplication requires production of the bacterial Virulence-associated protein A (VapA) which is released into the phagosome lumen. VapA pH-neutralizes intracellular compartments allowing R. equi to multiply in an atypical macrophage phagolysosome. Here, we show that VapA does not support intra-macrophage growth of several other bacterial species demonstrating that only few bacteria have the specific preadaptations needed to profit from VapA. We show that the closest relative of R. equi, environmental Rhodococcus defluvii (Prescotella defluvii), does not multiply in macrophages at 37°C even when VapA is present because of its thermosensitivity but it does so once the infection temperature is lowered providing rare experimental evidence for 'thermal restriction'. Using growth experiments with isolated macrophage lysosomes and modified infection schemes we provide evidence that R. equi resists the attack by phagolysosome contents at low pH for several hours. During this time, R. equi produces and secretes VapA which enables it to grow at the expense of lysosome constituents. We present arguments that, under natural infection conditions, R. equi is VapA-less during the initial encounter with the host. This has important implications for vaccine development.

Alterations in the conjunctival surface bacterial microbiome in bacterial keratitis patients

Microbial keratitis is an infectious disease of the eye, in which the cornea is inflamed. Under severe conditions, keratitis can lead to significant loss of vision and enucleation of the eye. Ocular trauma is the major risk factor causing keratitis and microorganisms viz., bacteria, fungi, viruses are the causative agents. The current study characterized the conjunctival bacterial microbiomes of healthy individuals and individuals with bacterial keratitis (BK) and assessed whether ocular microbiome dysbiosis is prevalent in BK patients. Ocular bacterial microbiomes were generated from the conjunctival swabs of healthy controls (HC-SW) and conjunctival swabs (BK-SW) and corneal scrapings (BK-CR) of BK patients using V3-V4 amplicon sequencing and data analysed using QIIME and R software. The Alpha diversity indices, diversity and abundance of different phyla and genera, heat map analysis, NMDS plots and inferred functional pathway analysis clearly discriminated the bacterial microbiomes of conjunctival swabs of healthy controls from that of BK patients. Preponderance of negative interactions in the hub genera were observed in BK-CR and BK-SW compared to HC-SW. In addition, a consistent increase in the abundance of pathogenic bacteria, as inferred from published literature, was observed in the conjunctiva of BK patients compared to HC and this may be related to causing or exacerbating ocular surface inflammation. This is the first study demonstrating dysbiosis in the ocular bacterial microbiome of conjunctiva of bacterial keratitis patients compared to the eye of healthy controls. The bacterial microbiome associated with the corneal scrapings of keratitis individuals is also described for the first time.

Rhodococcus bacteremia in cancer patients is mostly catheter related and associated with biofilm formation

Rhodococcus is an emerging cause of opportunistic infection in immunocompromised patients, most commonly causing cavitary pneumonia. It has rarely been reported as a cause of isolated bacteremia. However, the relationship between bacteremia and central venous catheter is unknown. Between 2002 and 2010, the characteristics and outcomes of seventeen cancer patients with Rhodococcus bacteremia and indwelling central venous catheters were evaluated. Rhodococcus bacteremias were for the most part (94%) central line-associated bloodstream infection (CLABSI). Most of the bacteremia isolates were Rhodococcus equi (82%). Rhodococcus isolates formed heavy microbial biofilm on the surface of polyurethane catheters, which was reduced completely or partially by antimicrobial lock solution. All CLABSI patients had successful response to catheter removal and antimicrobial therapy. Rhodococcus species should be added to the list of biofilm forming organisms in immunocompromised hosts and most of the Rhodococcus bacteremias in cancer patients are central line associated.

Rhodococcus erythropolis septicaemia in a patient with acute lymphocytic leukaemia

Rhodococcus erythropolis rarely causes infection in humans. We report the second case of R. erythropolis septicaemia in a 7-year-old child. However, to our knowledge it is the first case in a patient with acute lymphocytic leukaemia who had been undergoing chemotherapy. The identification was performed using 16S rRNA gene sequencing. Even though R. erythropolis is rarely associated with human infections, it should be considered as a potential causative agent of bacteraemia, rather than overlooked as a contaminant.

Recurrent Rhodococcus gordoniae eyelid infection after combined septoplasty and blepharoplasty

Rhodococcus species are rare human pathogens. Most cases of human infection have involved Rhodococcus equi, a natural zoonotic pathogen causing pneumonia in young foals. The human population at risk mainly includes immunocompromised patients. Infection of immunocompetent hosts has been rare, with less than 30 reported cases in the literature. The authors report a first case of recurrent Rhodococcus gordoniae granulomatous lower eyelid infection that occurred after an immunocompetent 44-year-old woman underwent a combined intranasal and lower blepharoplasty procedure. A literature search revealed only 10 reported cases of non-R. equi rhodococcal infections, most involving traumatic inoculation; 5 of these cases involved the eye and ocular adnexa. To the author's knowledge, this is the first case report of a non-R. equi rhodococcal infection of the eyelids. Identification of Rhodococcus by most laboratories is difficult, and in this case, 2 of 3 cultures were misidentified prior to definitive testing at a specialized laboratory. Multidrug resistance is also a concern, and the treatment course could be long and difficult.

Case report: Rhodococcus erythropolis osteomyelitis in the toe

The Rhodococcus species rarely cause musculoskeletal infections, with only two cases reported in the literature. We report the case of a 53-year-old woman who had an infection develop after first metatarsophalangeal joint fusion. A year after surgery, she continued to have pain and swelling with nonunion. She underwent revision of the arthrodesis and tissue samples from surgery revealed Rhodococcus erythropolis. The patient's symptoms improved with oral antibiotics. One year after the revision surgery, the fusion had united. We believe this is the first report of a case of a musculoskeletal infection caused by Rhodococcus erythropolis.

First case of bloodstream infection caused by Rhodococcus erythropolis

We describe the first case of bloodstream infection caused by Rhodococcus erythropolis. The identification was performed using 16S rRNA sequencing. This case illustrates that non-equi Rhodococcus infections may be underdiagnosed due to difficulties in identification in the routine clinical microbiology laboratory.

Molecular identification of environmental bacteria in indoor air in the domestic home: description of a new species of Exiguobacterium

The quality of indoor air in terms of its bioaerosol composition with microorganisms is important due to its potential aetiological role in development of conditions such as Sick Building Syndrome. Hence, laboratory identification of bacteriological components in any bioaerosol from buildings may help elucidate the role of such organisms in disease states, particularly allergy-related conditions. A molecular method was developed employing universal or "broad-range" eubacterial PCR to help identify environmental culturable bacteria from domestic household air. In a "proof of concept" experiment, 16S rDNA PCR was performed on a collection of bacterial isolates originating from indoor air in the domestic home. 16S rDNA PCR was performed using a set of universal primers to successfully generate an amplicon of approximately 1400 bp, which was sequenced to obtain each isolate's identity. Sequence analysis was able to identify 12/13 of the isolates, whereby the majority were Gram-positive (12/13). Nine different genera were identified from the 13 isolates examined, of which, 12/13 were Gram-positive, with the exception being Moraxella osloensis, which was Gram-negative, as well as a novel species of Exiguobacterium. The closest phylogenetic neighbour of the wildtype isolate to a named species within this genus was E. aestuarii (1364/1384 bases; 98.4% homology), followed by E. marinum (97.5%) and with E. acetylicum being the most distantly related of all the described species. On account of this divergence within the 16S rDNA gene operon of the unknown Exiguobacterium isolate, we believe this isolate to represent a novel species of Exiguobacterium, which we have tentatively named Exiguobacterium belfastensis. Although from this study, these organisms are usually unlikely to be clinically significant to healthy individuals with a competent immune system, we recommend that molecular identification methods are used, if considered necessary, as an adjunct to first line phenotypic identification schemes, where a definitive identification is required. When the use of molecular identification methods is justified, employment of partial 16S rDNA PCR and sequencing provides a valuable and reliable method of identification of environmental bacteria in the home. This study demonstrates the usefulness of such methods and a full and comprehensive study is now required to examine the diversity of bacteria in indoor air in the home, with particular emphasis on the risk of such environmental organisms to immunosurpressed patients, such as those with haematological malignancies and who are neutropenic.

Rhodococcus ruber as a Cause of Keratitis

PURPOSE

To report a case of suppurative keratitis caused by Rhodococcus ruber in a healthy 31-year-old male patient.

METHODS

Ocular examination of the patient revealed a central corneal epithelial defect following trauma, with severe anterior chamber reaction hypopyon. Corneal scrapings were performed from the base of the ulcer and were subjected to routine microbiologic investigation including direct microscopic techniques (Gram stain and 10% KOH), and culture was done on blood agar and potato dextrose agar. Biochemical analysis and antibiotic sensitivity testing were done on the isolate, and additional confirmation was done by DNA sequencing.

RESULTS

The isolate was identified as Rhodococcus ruber, an uncommon cause of suppurative keratitis. The isolate was found to be sensitive to augmentin, erythromycin, co-trimoxazole, tobramycin, amikacin, ciprofloxacin, ofloxacin, and sulfamethoxazole.

CONCLUSION

We present a case of Rhodococcus ruber, which was successfully treated. Even if the clinical picture of ulcer is nonspecific, the need of a routine microbiologic examination and sequencing proves to be confirmatory in cases of suppurative keratitis, where the causative organisms are varied in nature.

Can whole genome analysis refine the taxonomy of the genus Rhodococcus?

The current systematics of the genus Rhodococcus is unclear, partly because many members were originally included before the application of a polyphasic taxonomic approach, central to which is the acquisition of 16S rRNA sequence data. This has resulted in the reclassification and description of many new species. Hence, the literature is replete with new species names that have not been brought together in an organized and easily interpreted form. This taxonomic confusion has been compounded by assigning many xenobiotic degrading isolates with phylogenetic positions but without formal taxonomic descriptions. In order to provide a framework for a taxonomic approach based on multiple genetic loci, a survey was undertaken of the known genome characteristics of members of the genus Rhodococcus including: (i) genetics of cell envelope biosynthesis; (ii) virulence genes; (iii) gene clusters involved in metabolic degradation and industrially relevant pathways; (iv) genetic analysis tools; (v) rapid identification of bacteria including rhodococci with specific gene RFLPs; (vi) genomic organization of rrn operons. Genes encoding virulence factors have been characterized for Rhodococcus equi and Rhodococcus fascians. Based on peptide signature comparisons deduced from gene sequences for cytochrome P-450, mono- and dioxygenases, alkane degradation, nitrile metabolism, proteasomes and desulfurization, phylogenetic relationships can be deduced for Rhodococcus erythropolis, Rhodococcus globerulus, Rhodococcus ruber and a number of undesignated Rhodococcus spp. that may distinguish the genus Rhodococcus into two further genera. The linear genome topologies that exist in some Rhodococcus species may alter a previously proposed model for the analysis of genomic fingerprinting techniques used in bacterial systematics.

Antibiotic irrigation of the capsular bag to resolve low-grade endophthalmitis

Chronic, low-grade endophthalmitis after cataract surgery with intraocular lens (IOL) implantation is often unresponsive to antibiotic therapy, probably because of low drug penetration into the capsular bag. To increase the drug concentration at the infection site, we irrigated the capsular bag with antibiotics. Within 6 weeks, endophthalmitis resolved in three consecutive patients with positive aqueous cultures. Visual acuity improved from finger counting or less to 20/40 or better in all cases. No recurrence was seen in the 12 to 19 month follow-up. Antibiotic irrigation of the capsular bag can resolve chronic, low-grade endophthalmitis in culture-positive patients unresponsive to the same drugs administered by other routes, including conventional intraocular injection. With this approach there is minimal surgical trauma and the IOL is retained.

Intraocular lens removal from eyes with chronic low-grade endophthalmitis

Intraocular lenses (IOLs) were removed from 11 eyes with chronic low-grade endophthalmitis after cataract extraction to restore useful vision and prevent recurrence. One anterior chamber lens, one iris-supported lens, and nine posterior chamber lenses were removed. In the eyes with posterior chamber lenses, the posterior capsule was intact; total (n = 7) or partial (n = 2) capsulectomy was performed in these eyes. Aqueous humor specimens obtained at surgery were positive for bacteria in five eyes, but scanning electron microscopy showed bacteria on all removed IOLs and capsular bags. Final best corrected visual acuity was 20/40 or better in seven eyes. Reduced visual acuity, between 20/50 and 20/400 in three eyes and counting fingers in one eye, was related to retinal detachment (n = 2) and age-related macular degeneration (n = 2). Transient hyphema was seen in one eye. With a mean follow-up of 21 months (range 10 to 31 months), no recurrence of inflammation was observed. The results show that negative cultures do not preclude a bacterial cause for infection and that primary IOL removal with partial or total capsulectomy provides a surgical approach to the treatment of chronic low-grade endophthalmitis not responsive to medical therapy.

Endophthalmitis caused by the coagulase-negative staphylococci. 1. Disease spectrum and outcome

PURPOSE

The coagulase-negative staphylococci are the most common causes of postoperative endophthalmitis. This study investigates the variability in the disease spectrum and visual outcome of coagulase-negative staphylococcal endophthalmitis in a large, single-center series.

METHODS

Ninety consecutive cases of coagulase-negative staphylococcal endophthalmitis were investigated retrospectively from two time periods, 1978 to 1982 and 1985 to 1987, separated by a transitional period in cataract surgery technique. Using a detailed protocol, inpatient, outpatient, and microbiologic records were analyzed. Six-month visual acuity results were obtained.

RESULTS

Diagnosis frequently was delayed, often suspected only after hypopyon development. Thirty-seven percent of patients presented more than 1 week after the inoculating event, and 13% presented after more than 1 month. Variable asymptomatic intervals and gradually worsening inflammatory prodromes are noted. Painless endophthalmitis occurred in 16%. Non-epidermidis infections comprised 28%. With vitrectomy/intraocular antibiotic management, 38% and 68% achieved visual acuities of 20/50 and 20/400, respectively. Overall, 10% of patients developed late retinal detachments. This occurred in only 4% of patients, with endophthalmitis occurring after cataract surgery.

CONCLUSION

Ophthalmologists should become familiar with the emerging concepts of delayed-onset, chronic, and often painless endophthalmitis in which the coagulase-negative staphylococci play a prominent role.