Infection of a ventriculoatrial shunt with phenotypically variable Staphylococcus epidermidis masquerading as polymicrobial bacteremia due to various coagulase-negative Staphylococci and Kocuria varians

Kocuria Species Infections in Humans-A Narrative Review

Kocuria species are catalase-positive and coagulase-negative Gram-positive coccoid bacteria that belong to the family Micrococcaceae, order Actinomycetales, and class Actinobacteria. Even though they may be relatively rare, they have been increasingly reported as the causes of human infections lately. The present study aims to review all published cases of Kocuria spp. infections in humans reporting data on epidemiology, microbiology, antimicrobial susceptibility, antimicrobial treatment, and mortality. A narrative review was performed based on a search of Pubmed and Scopus databases in the literature. In total, 73 studies provided data on 102 patients with Kocuria spp. infections. The mean age of patients was 47 years, and 68.3% were male. The most common types of infection were bacteremia (36.3%), skin and soft tissue infection (18.6%), endophthalmitis (15.7%), infective endocarditis (13.7%), and peritonitis (11.8%), most commonly peritoneal-dialysis-associated. The most frequently isolated species was K. kristinae (46.1%), and antimicrobial resistance was lower for vancomycin (7%) and tetracyclines (6.7%). Vancomycin (47%), cephalosporins (39.6%), and quinolones (36.6%) were the most commonly used antimicrobials. The empirical antimicrobial treatment of Kocuria spp. infections should include vancomycin as long as antimicrobial susceptibility results are pending. The infection outcome mainly depends on the type of infection and is higher for infective endocarditis. Endophthalmitis is associated with increased rates of low visual acuity after treatment.

Multiple rare organisms causing ventriculoperitoneal shunt infection and brain abscess

Ventriculoperitoneal shunts (VPS) are inserted to treat issues with CSF flow dynamics, such as obstructions causing CSF build up which raises the intracranial pressure. A major complication of this procedure is VPS infections. Vast majority of VPS infections are monomicrobial and may occur in the first two years of insertion due to contiguous or hematogenous spread. Here, we report a rare case of polymicrobial VPS infection with 5 pathogens. One of these organisms (Citrobacter werkmanii) has been reported as a cause of meningitis for the first time in this report. The other organism (Enterococcus casseliflavus) has been reported as a cause only one other time. Hence, we recommend considering these newly emerging organisms when dealing with meningitis.

Kocuria Endophthalmitis: Clinical Spectrum and Long-term Outcomes

PURPOSE

To expand the knowledge regarding the clinical presentation of Kocuria endophthalmitis.

METHODS

We included six cases of Kocuria endophthalmitis between January 2018 and December 2020. From all cases, we collected general demographic data, relevant medical, ophthalmological history, microbiological and antibiotic sensitivity results. All cases had a minimum follow-up of 9 months. All cases were treated with intravitreal moxifloxacin and dexamethasone and pars plana vitrectomy. Undiluted vitreous, corneal, conjunctival, and aqueous samples were cultured and analyzed with the Vitek 2 system.

RESULTS

The prevalence of Kocuria endophthalmitis was 6%. (95%CI: 2.26%-12.73%). The mean age at diagnosis was 60.5 ± 15.5 years. All patients had poor visual acuity, severe pain, and severe conjunctival hyperemia at diagnosis. Only one case had a significant improvement in visual acuity at the end of the follow-up.

CONCLUSION

Kocuria spp are an emerging cause of endophthalmitis and should be considered as part of the differential diagnosis.

Clinical Features and Outcomes of Kocuria Keratitis and Comparison With Coagulase-Negative Staphylococci Keratitis

PURPOSE

To describe the clinical features and outcomes of Kocuria keratitis and to compare the same with those of Coagulase-negative Staphylococcal (CoNS) keratitis.

METHODS

Medical records of cases with microbiologically proven Kocuria keratitis, seen from January 2011 to December 2017 were reviewed. The data related to predisposing factors, clinical characteristics, antibiotic susceptibility, and the treatment and their outcomes were collected. These parameters were also compared with those of consecutive patients with CoNS keratitis.

RESULTS

Medical records of 23 patients (n = 23 eyes) with Kocuria keratitis were reviewed, and after exclusion of 6 mixed infections, 17 cases with only Kocuria infection were analysed. The median visual acuity at presentation was finger counting 0.5 m [LogMAR 2.00 (1.70-2.70)]. The ulcer was characterized by a central infiltrate (88.2%) involving the anterior stroma (58.8%) with an associated hypopyon (29.4%). Kocuria rosea was the most common species (47.8%). Ninety percent of the isolates identified were susceptible to vancomycin and ofloxacin. In 12 cases (70.6%), the ulcer resolved with the use of topical antibiotics alone in 52 (29-79) days, whereas 3 eyes were subjected to therapeutic penetrating keratoplasty. On comparing the 44 cases of CoNS keratitis, the demographics and the visual acuity at presentation were comparable. Both groups had a similar in presentation response with medical therapy (P, 0.48) and those requiring surgical intervention (P, 0.76).

CONCLUSION

Kocuria is a rare but potential cause of keratitis manifesting in the presence of a compromised ocular surface. Similar to CoNS, it has good clinical response with medical management.

Infective endocarditis as a complication of longstanding ventriculoatrial (VA) shunt: the importance of suspicion and early investigation in patients with VA shunt and pyrexia of unknown origin

Ventriculoatrial (VA) shunts are a method of cerebrospinal fluid diversion, which nowadays are infrequently seen in medical practice. Infective endocarditis (IE) can occur as rare complications of VA shunts, through the introduction of a foreign body close to the tricuspid valve. We report a case of infective endocarditis, that is, in a patient with VA shunt for congenital hydrocephalus. We present the case to highlight the importance of early investigation for IE in patients with fever of unknown origin and shunt in situ, as rapid deterioration can occur and be fatal. We also discuss past experience reported in the literature on the role of cardiothoracic intervention. Prompt diagnosis and early cardiothoracic referral for surgery are crucial, there may only be a narrow window of opportunity for intervention before patients develop fulminant sepsis.

Vegetation of Ventriculoatrial Shunt Managed via Multidisciplinary Surgical Approach

INTRODUCTION

The popularity of the ventriculoatrial shunt as a means for cerebrospinal fluid diversion was temporally limited, overcome by the success of the peritoneum as a site for distal drainage. Nevertheless, it remains an important tool for patients for whom ventriculoperitoneal shunting is not an option.

CLINICAL PRESENTATION

We present the case of a 9-year-old girl with a ventriculoatrial shunt, who had undergone multiple revisions. Ultimately, she suffered a wound dehiscence, resulting in infectious seeding of the bloodstream and formation of a thrombus, presumed granuloma, at the tip of the distal catheter in the right atrium. She underwent successful removal of the lesion via an open approach by our cardiothoracic colleagues.

DISCUSSION

Previous authors have noted a high number of mortalities as a result of these lesions. A collaborative approach resulted in a successful outcome for our patient. Although limited in utility today, the ventriculoatrial shunt remains a common procedure for neurosurgeons today.

CONCLUSION

Recognizing the potential for atrial thrombus formation and using a team approach can help avoid a poor outcome.

Transesophageal Echocardiography-Guided Ventriculoatrial Shunt Insertion

BACKGROUND

Determining an optimal location within the right atrium (RA) for placement of the distal ventriculoatrial (VA) shunt catheter offer several operative challenges that place patients at risk for perioperative complications and downstream VA shunt failure. Utilizing transesophageal echocardiography (TEE) guidance to place distal VA shunt catheters may help to circumvent these risks.

OBJECTIVE

To review our current practice of VA shunt insertion using TEE guidance.

METHODS

A retrospective review of all consecutive patients who underwent VA shunt procedures between December 19, 2016 and January 22, 2019, during which time intraoperative TEE was used for shunt placement was performed. Data on the time required for shunt placement and total procedure time, baseline echocardiography findings, and short- and long-term complications of shunt placement were assessed.

RESULTS

A total of 33 patients underwent VA shunt procedures, with a median follow-up time of 250 (88-412) d. The only immediate complication related to shunt placement or TEE use was transient ectopy in 1 patient. The mean time for atrial catheter insertion was 12.6 ± 4.8 min. Right-heart catheters were inserted between the RA-superior vena cava junction and 22 mm within the RA in all but 3 procedures. A total of 7/33 patients (21%) underwent shunt revision. Indications for revisions included distal clots, proximal obstruction, positive blood culture, and shunt valve revision. No other complications of VA shunt insertion were reported.

CONCLUSION

VA shunt insertion using TEE allows for precise distal catheter placement. Early patient experience confirms this technique has a low complication rate.

Clinical presentations, management outcomes, and diagnostic dilemma in Kocuria endophthalmitis

AIM

To describe the clinical presentations and management outcomes of Kocuria endophthalmitis and discuss diagnostic dilemmas DESIGN: Retrospective interventional comparative case series INTERVENTION: Eight unilateral cases with culture-proven Kocuria endophthalmitis from January 2013 to December 2017 underwent vitrectomy/vitreous biopsy and intravitreal antibiotic with or without additional procedures. The undiluted vitreous was subjected to microbiologic evaluation.

MAIN OUTCOME MEASURES

The mean age at presentation, etiology, number of interventions, interval between inciting event and presentation, type of intravitreal antibiotic used, and anatomic and functional outcomes were reported. A favorable anatomic outcome was defined as preservation of the globe, absence of hypotony, attached retina, and absence of active inflammation at the last visit.

RESULTS

In the current series, there were five males and three females. The mean age at presentation was 31 ± 17.44 years (median 30 years). The inciting event was open globe injury in five cases and one case each following cataract surgery, microbial keratitis, and endogenous cause. Visual acuity was ≥ 20/400 in one case at presentation and ≥ 20/400 in three cases at the last visit. The species identified by Vitek 2, included Kocuria kristinae in three, K. rosea in four and K. varians in one. Follow-up period was 8.25 ± 8.24 months (median 6.5). Six cases (75%) had complete resolution of infection and inflammation at the last visit. Anatomic success was achieved in 75%.

CONCLUSIONS

Kocuria is a relatively rare cause of endophthalmitis often misdiagnosed as Staphylococcal endophthalmitis. Clinical presentation can be variable but favorable antibiotic susceptibility and appropriate timely management can result in acceptable visual and anatomic outcomes.

Small-colony variant of Staphylococcus lugdunensis in prosthetic joint infection

Prosthetic joint infection is usually caused by staphylococci. Among the coagulase-negative staphylococci, Staphylococcus lugdunensis is important because it behaves as a pathogen similar to S aureus. It also develops biofilms, and the biofilm phenotype can appear as small-colony variants. Although genetically indistinguishable, they differ in size and antibiotic susceptibility from the parent strain and are responsible for chronic persistent infection and failure of antibiotic treatment. They can also lead to misinterpretation of results. The patient reported here underwent total knee replacement and 2 years later presented with prosthetic joint infection. Tissue samples and prosthesis taken at revision grew S lugdunensis, the majority of which were small-colony variants. Recommendations are made for their detection and identification.

Utility of strain typing of Propionibacterium acnes in central nervous system and prosthetic joint infections to differentiate contamination from infection: a retrospective cohort

The study aimed to retrospectively assess if strain typing of Propionibacterium acnes could help to distinguish between infection and contamination in isolates recovered from the central nervous system (CNS) and prosthetic joints (PJs). This was a retrospective cohort of all Propionibacterium species isolates from the Barnes-Jewish Hospital (St Louis, MO, USA) clinical microbiology laboratory from 2011 to 2014. Available frozen isolates were recovered, and strain type (IA-1, IA-2, IB, II, III, or nontypeable class A or B) was determined via polymerase chain reaction (PCR)-based methods. For CNS isolates, P. acnes was considered pathogenic if treating physicians administered ≥7 days of directed antibiotic therapy against P. acnes. During the study period, Propionibacterium species was isolated from clinical cultures 411 times. 152 isolates were available for analysis. Of the 152 isolates, 140 were confirmed to be P. acnes, 61 of which were from the CNS (45 contaminants, 16 infections). Strain type IA-1 was more common (50.0%, 8 out of 16) among CNS infections than among contaminants (22.2%, 10 out of 45). For PJ isolates 61.3% (19 out of 31) met the criteria for infection. The predominant strain type for CNS infection was IA-1 and for PJ isolates, IB. Strain type IA-1 was isolated more often in patients with CNS infections, which may indicate a predilection of this strain type to cause CNS infection. Future research should prospectively evaluate strain typing as a means of assisting in the diagnosis of CNS infections and confirm our findings.

Detection of Integrons and Staphylococcal Cassette Chromosome mec Types in Clinical Methicillin-resistant Coagulase Negative Staphylococci Strains

Objectives

Integrons are thought to play an important role in the spread of antibiotic resistance. This study investigates class 1 and 2 integron-positive methicillin-resistant coagulase-negative staphylococci strains isolated in Iran and characterizes their patterns of antimicrobial resistance.

Methods

Hundred clinical isolates of coagulase-negative staphylococci were characterized for integron content and staphylococcal cassette chromosome mec (SCCmec) type.

Results

Sixteen isolates carried class 1 (intI1) integrons and four isolates carried class 2 (intI2) integrons. One resistance gene array was identified among the class 1 integrons (aadA1 cassette). The distribution of SCCmec types in 50 methicillin-resistant coagulase-negative staphylococci strains showed that SCCmec types III and V dominated among the tested strains.

Conclusion

This is the first report of methicillin-resistant coagulase-negative staphylococci strains that carry two mobile genetic elements, including class 1 and 2 integrons and SCCmec, in Iran.

Emerging Bacterial Infection: Identification and Clinical Significance of Kocuria Species

Recently there have been reports of gram-positive cocci which are morphologically similar to both Staphylococci and the Micrococci. These bacteria have been identified as Kocuria species with the help of automated identification system and other molecular methods including 16S rRNA (ribosomal ribonucleic acid) evaluation. Kocuria belongs to the family Micrococcaceae which also includes Staphylococcus species and Micrococcus species. Isolation and clinical significance of these bacteria from human specimens warrant great caution as it does not necessarily confirm infection due to their ubiquitous presence, and as a normal flora of skin and mucous membranes in human and animals. Most clinical microbiology laboratories ignore such bacteria as laboratory and specimen contaminants. With increasing reports of infections associated with these bacteria, it is now important for clinical microbiologists to identify and enumerate the virulence and antibiotic susceptibility patterns of such bacteria and assist clinicians in improving the patient care and management. We review the occurrence and clinical significance of Kocuria species.

Rare sequelae following ventriculoatrial shunt: Case report and review of literature

Ventriculoatrial shunt (VA) is one of the oldest solutions for hydrocephalus. However over subsequent years various complication of VA shunt such as obstructions, malposition, shunt infections, cardiac complications such as endocarditis, traumatic perforation, heart failure, tricuspid regurgitation, intraatrial thrombus, and pulmonary hypertension are reported. Hence, VA shunt procedure has fallen into disrepute. Still VA shunt may be a good option in selected patients with hostile peritoneum. Newer placement strategies and monitoring methods have been put forward to reduce complication following VA shunt. In this case report, we share a rare case of endocarditis with tricuspid regurgitation following a migrated retained calcified shunt tube in the right ventricle of heart 30 years after of VA shunt that was successfully managed.

Notable alkaline tolerance of Kocuria marina isolate from blood of a pediatric patient with continuous intravenous epoprostenol therapy

This study was the first to describe the hitherto deficiently evaluated alkaline tolerance of Kocuria marina isolate from a pediatric patient with continuous intravenous epoprostenol dosing therapy. Our isolate from blood of a 7-year-old Japanese boy was finally identified as K. marina by the morphological, cultural, and biochemical properties together with the comparative sequence analyses of the 16S rRNA genes. The K. marina isolate, the causative agent of catheter-related blood-stream infection, was not only revealed to be salt tolerant (NaCl 15%), but also demonstrated to be stably survived with no apparent decrease of cell counts for long periods (120 h) in an alkaline environment (pH 8, 9, 10, and 11) at 35 °C. Its remarkable tolerance to the stresses of high alkalinity compared with a clinical Staphylococcus aureus strain should provide consistent interpretation that the environment of high alkalinity (pH 10.2-10.8) measures should be insufficient to inactivate almost all the causative agents including K. marina strains in the solution of epoprostenol (pH 10.4) (Flolan(®), GlaxoSmithKline, Ltd., Tokyo, Japan.). To the best of our knowledge, the first description of the property of being tolerant to high alkalinity that the K. marina isolate exhibited was noteworthy and a useful piece of information. In conclusion, we believe that the present study should be a notification regarding the potential risk of catheter-related blood-stream infections due to K. marina, suggestive of an alkalophile, especially in patients receiving continuous intravenous epoprostenol dosing therapy.

Rapid and simple detection of methicillin-resistance Staphylococcus aureus by orfX loop-mediated isothermal amplification assay

Background

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most prevalent pathogens responsible for nosocomial infections throughout the world. As clinical MRSA diagnosis is concerned, current diagnostic methodologies are restricted by significant drawbacks and novel methods are required for MRSA detection. This study aimed at developing a simple loop-mediated isothermal amplification (LAMP) assay targeting on orfX for the rapid detection of methicillin-resistance Staphylococcus aureus (MRSA).

Results

The protocol was designed by targeting orfX, a highly conserved open reading frame in S. aureus. One hundred and sixteen reference strains, including 52 Gram-positive and 64 Gram-negative isolates, were included for evaluation and optimization of the orfX-LAMP assay. This assay had been further performed on 667 Staphylococcus (566 MRSA, 25 MSSA, 53 MRCNS and 23 MSCNS) strains and were comparatively validated by PCR assay using primers F3 and B3, with rapid template DNA processing, simple equipments (water bath) and direct result determination (both naked eye and under UV light) applied. The indispensability of each primer had been confirmed, and the optimal amplification was obtained under 65°C for 45 min. The 25 μl reactant was found to be the most cost-efficient volume, and the detection limit was determined to be 10 DNA copies and 10 CFU/reaction. High specificity was observed when orfX-LAMP assay was subjected to 116 reference strains. For application, 557 (98.4%, 557/566) and 519 (91.7%, 519/566) tested strains had been detected positive by LAMP and PCR assays. The detection rate, positive predictive value (PPV) and negative predictive value (NPV) of orfX-LAMP were 98.4%, 100% and 92.7% respectively.

Conclusions

The established orfX-LAMP assay had been demonstrated to be a valid and rapid detection method on MRSA.

The expanding spectrum of human infections caused by Kocuria species: a case report and literature review

Although not previously known to cause human infections, Kocuria species have now emerged as human pathogens, mostly in compromised hosts with severe underlying disease. Recently, there has been an increasing incidence of different types of Kocuria infections reported, most likely due to the adoption of better identification methods. Here, we report a case of peritonitis caused by Kocuria rosea in a diabetic nephropathy patient who was on continuous ambulatory peritoneal dialysis. Sepsis and peritonitis caused by K. rosea in our case yielded two identical Kocuria isolates from the peritoneal dialysate fluid within a period of three days. The infection was subsequently resolved by antibiotic treatment and catheter removal. In addition to reporting this case, we herein review the literature concerning the emergence of Kocuria as a significant human pathogen. The majority of cases were device-related, acquired in the hospital or endogenous, and different Kocuria species appear to share a common etiology of peritonitis. The overall disease burden associated with Kocuria appears to be high, and the treatment guidelines for diseases associated with Kocuria have not yet been clearly defined.

Reasons, procedures, and outcomes in ventriculoatrial shunts: A single-center experience

Background:

Ventricular shunts are used to drain cerebrospinal fluid into extra-cranial spaces. Ventriculoatrial (VA) shunts are provided to transfer cerebrospinal fluid from the cerebral ventricle into the right atrium of the heart. A single center experience of indications, procedure, and clinical outcomes in VA shunt was presented in current study.

Methods:

VA shunts were applied in 10 patients who had repeated previous shunt dysfunction or infection. The reasons, clinical findings, replacement methods, and postoperative clinical follow-ups and outcomes were recorded retrospectively.

Results:

There were seven female (70%) and three (30%) male patients; their ages ranged from 5 to 13 years (mean ± SD; 8.5 ± 2.6 years). Shunt re-placement reasons were as follows: Shunt occlusion in five patients, intraperitoneal infection in four patients and a distal catheter was kinked and knotted in one patient. Postoperative early complications were seen in one patient as early catheter thrombosis and catheter revision were applied. Late complications were seen in two patients as follows: Catheter infection and infective endocarditis occurred in one patient and pulmonary thrombus occurred in one other patient. There was not any catheter-related mortality observed at the one year follow-up period.

Conclusion:

VA shunts may be an option for cerebrospinal fluid drainage at necessary conditions. However, sterilization and general training on asepsy and antisepsy are the most important determinants affecting the clinical outcome due to the cardio systemic relationship.

Development of PCR primers and a DNA macroarray for the simultaneous detection of major Staphylococcus species using groESL gene

Staphylococcus spp., including S. aureus, S. intermedius, S. hyicus, S. epidermidis, S. saprophyticus, S. haemolyticus, S. xylosus, and S. carnosus, are major bacterial species associated with food poisoning, and human and veterinary clinics. Traditional methods for the identification of these staphylococci are time-consuming, laborious, or inaccurate. Therefore, rapid and accurate diagnostic methods are needed. In this study, we designed the DNA probes and polymerase chain reaction (PCR) primers for the detection of the aforementioned Staphylococcus species. These primers were proved to be specific for the detection of their corresponding target strains. Furthermore, by using a consensus primer pair, we were able to co-amplify the intergenic region of groES-groEL for these staphylococci. Followed by a chromogenic macroarray system with the specific probes on the plastic chips, these staphylococci in milk products or clinical samples could be simultaneously detected. When the system was used for the inspection of milk or urine samples containing N × 10⁰ target cells per milliliter of the sample, all these staphylococcal species could be identified after an 8-h pre-enrichment step. This system also allowed the adequate diagnosis of bacteremia, since N × 10⁰ target cells per milliliter of the blood samples could be detected after a 12-h pre-enrichment. Compared to the multiplex PCR method, this approach has the additional advantage that it allowed the discrimination of more bacterial strains-even some bacterial strains that may generate PCR products with the same molecular sizes.

Class 1 integron in staphylococci

As a major concern in public health, methicillin-resistant staphylococci (MRS) still remains one of the most prevalent pathogens that cause nosocomial infections throughout the world and has been recently labeled as a "super bug" in antibiotic resistance. Thus, surveillance and investigation on antibiotic resistance mechanisms involved in clinical MRS strains may raise urgent necessity and utmost significance. As a novel antibiotic resistance mechanism, class 1 integron has been identified as a primary source of antimicrobial resistance genes in Gram-negative organisms. However, most available studies on integrons had been limited within Gram-negative microbes, little is known for clinical Gram-positive bacteria. Based on series studies of systematic integrons investigation in hundreds of staphylococci strains during 2001-2006, this review concentrated on the latest development of class 1 integron in MRS isolates, including summary of prevalence and occurrence of class 1 integron, analysis of correlation between integron and antibiotic resistance, further demonstration of the role integrons play as antibiotic determinants, as well as origin and evolution of integron-associated gene cassettes during this study period.

Drug sensitivity and clinical impact of members of the genus Kocuria

Organisms in the genus Kocuria are Gram-positive, coagulase-negative, coccoid actinobacteria belonging to the family Micrococcaceae, suborder Micrococcineae, order Actinomycetales. Sporadic reports in the literature have dealt with infections by Kocuria species, mostly in compromised hosts with serious underlying conditions. Nonetheless, the number of infectious processes caused by such bacteria may be higher than currently believed, given that misidentification by phenotypic assays has presumably affected estimates of the prevalence over the years. As a further cause for concern, guidelines for therapy of illnesses involving Kocuria species are lacking, mostly due to the absence of established criteria for evaluating Kocuria replication or growth inhibition in the presence of antibiotics. Therefore, breakpoints for staphylococci have been widely used throughout the literature to try to understand this pathogen's behaviour under drug exposure; unfortunately, this has sometimes created confusion, thus higlighting the urgent need for specific interpretive criteria, along with a deeper investigation into the resistance determinants within this genus. We therefore review the published data on cultural, genotypic and clinical aspects of the genus Kocuria, aiming to shed some light on these emerging nosocomial pathogens.

Kocuria varians infection associated with brain abscess: a case report

Background

Kocuria, established by Stackebrandt et al., previously was classified into Micrococcus. Only two species, K. rosea and K. kristinae are reported to be associated as pathogenic and found with catheter-related bacteremia and acute cholecystitis.

Case presentation

We herein report the first case of brain abscess caused by Kocuria varians, a gram-positive microorganism, in a 52-year-old man. Hematogenous spread is the probable pathogenesis.

Conclusions

This report presents a case of Kocuria varians brain abscess successfully treated with surgical excision combined with antimicrobial therapy. In addition, Vitek 2 system has been used to identify and differentiate between coagulase-negative staphylococcus.

Use of colony morphology to characterize carriage profiles of coagulase negative staphylococci

The absence of a reliable method to distinguish among coagulase negative staphylococcal strains in mixed culture hinders elucidation of colonization traits and precise tracking of colonization. This study examined whether colonial morphology could be used to correctly identify coagulase negative staphylococcal strains in mixed cultures. Staphylococci were isolated from nasal and hand cultures of ten subjects at 0 and 3 months. Samples were initially screened for the predominant coagulase negative staphylococcal strain by colonial morphology. The strains were subsequently identified by phenotypic and biochemical testing. Pulsed field gel electrophoresis demonstrated that the morphologic criteria correctly grouped the strains in 91.1% (41/45) of samples. This study suggests that colonial morphology is a reliable method for the initial characterization of coagulase negative staphylococcal strains. This approach has potential value for epidemiological studies that involve establishing links between commensal flora and their potential role as pathogens in subsequent clinical infections.

Characterization of coagulase-negative staphylococci isolated from patients with infected hip prostheses: use of phenotypic and genotypic analyses, including tests for the presence of the ica operon

The aim of this study was to investigate phenotypic and/or genotypic heterogeneity in coagulase-negative staphylococci (CoNS) obtained from multiple tissue samples taken perioperatively during exchange surgery from each of 19 patients with clinically and/or microbiologically proven hip prosthesis infections. CoNS are important pathogens in prosthetic hip joint infections. Several virulence factors have been suggested for CoNS, such as phenotypic variation, yet the pathogenic processes that are involved remain unclear. The PhenePlate system (PhPlate AB, Stockholm Sweden) was used for phenotyping and pulsed-field gel electrophoresis for genotyping of polymorphisms in isolates of CoNS. Furthermore, polymerase chain reaction was used to determine the presence of the icaADB gene complex in the isolates. Some patients were infected with CoNS and other species, some were infected with multiple CoNS species, although infections with Staphylococcus epidermidis alone were most common, and some were infected with different S. epidermidis clones. Phenotypic variation was found among isolates both from the same tissue sample and from different samples from the same patient, and in some cases such variation represented the presence of different clones. One-third of the patients infected with S. epidermidis carried the icaADB genes. CoNS isolates showing phenotypic and/or genotypic heterogeneity were identified in tissue samples from half of the patients. The presence of the intercellular adhesion (ica) operon does not seem to be a prerequisite for establishing infection with CoNS.

Erroneous reporting of coagulase-negative Staphylococci as Kocuria spp. by the Vitek 2 system

Misidentification of coagulase-negative staphylococci (CoNS) may delay appropriate treatment. We investigated 20 clinical isolates identified as Kocuria spp. by the Vitek 2 system. All were identified as CoNS by 16S rRNA gene sequencing (18 Staphylococcus epidermidis, 1 Staphylococcus haemolyticus). Four Kocuria isolates were shown to be identical to CoNS from the same patient by pulsed-field gel electrophoresis. Isolates identified by Vitek 2 as Kocuria most likely represent misidentified CoNS, and if clinically indicated, should be investigated further by genomic methods.