Coagulase-negative Species Research Articles

A Brazilian lineage of Staphylococcus lugdunensis presenting rough colony morphology may adhere to and invade lung epithelial cells

Staphylococcus lugdunensis is an unusually virulent coagulase-negative species, which causes serious infection similar to S. aureus. We evaluated the expression of virulence factors such as S. lugdunensis synergistic haemolysin (SLUSH), fibrinogen-binding protein (Fbl), biofilm production and biofilm-production-related genes in 23 S. lugdunensis clinical isolates and one type strain that had been previously characterized for their genotypes. In addition, the biofilm composition and the ability of isolates to adhere to and invade human epithelial lung cells were also investigated. The PCR method used detected the presence of slush and intercellular adhesin (ica) virulence genes in all isolates. All isolates produced the Fbl protein and, with the exception of the type strain, all isolates produced the SLUSH haemolysin. Fourteen (60.9 %) isolates produced biofilms. The detachment assay, using sodium metaperiodate or proteolytic enzymes to analyse the biofilm composition, showed protein-mediated biofilms in two representative isolates, one for each colony type (rough and smooth). All strongly biofilm-producing isolates, including three with rough colony morphology, had the same prevalent PFGE pattern. However, among the representative strains tested, only the S. lugdunensis isolate that formed rough colonies was able to adhere to and invade A549 cell monolayers in the same quantities as those observed with S. aureus isolates (P = 1.000). No significant adhesion or invasion was observed for the other isolates in comparison with the S. aureus isolate, independent of biofilm production or clonality. Our results could explain the incredible ability of this pathogen to cause infections that are as aggressive as S. aureus. In addition, the ability of S. lugdunensis to adhere to and invade eukaryotic cells was also noticed for isolates with rough colony morphology, reinforcing the increased virulence in this species.

Rising prevalence of antimicrobial resistance in urinary tract infections during pregnancy: necessity for exploring newer treatment options.

Background:Urinary tract infections (UTI) are one of the most common medical complications of pregnancy. The emergence of drug resistance and particularly the Extended-spectrum beta-lactamase production by Escherichia coli and methicillin resistance in Staphylococci, limits the choice of antimicrobials.Materials and Methods:Patients in different stages of pregnancy with or without symptoms of urinary tract infection attending the antenatal clinic of obstetrics and gynaecology were screened for significant bacteriuria, by standard loop method on 5% sheep blood agar and teepol lactose agar. Isolates were identified by using standard biochemical tests and antimicrobial susceptibility testing was done using Kirby Bauer disc diffusion method.Results:A total of 4290 (51.2%) urine samples from pregnant females showed growth on culture. Prevalence of asymptomatic bacteriuria 3210 (74.8%) was higher than symptomatic UTI 1080 (25.2%). Escherichia coli was the most common pathogen accounting for 1800 (41.9%) of the urinary isolates. Among the gram-positive cocci, coagulase negative species of Staphylococci 270 (6.4%) were the most common pathogen. Significantly high resistance was shown by the gram negative bacilli as well as gram positive cocci to the β-lactam group of antimicrobials, flouroquinolones and aminoglycosides. Most alarming was the presence of ESBL in 846 (47%) isolates of Escherichia coli and 344 (36.9%) isolates of Klebsiella pneumoniae, along with the presence of methicillin resistance in 41% of Staphylococcus species and high-level aminoglycoside resistance in 45(30%) isolates of Enterococcus species. Glycopeptides and carbepenems were the only group of drugs to which all the strains of gram positive cocci and gram negative bacilli were uniformly sensitive, respectively.Conclusions:Regular screening should be done for the presence of symptomatic or asymptomatic bacteriuria in pregnancy and specific guidelines should be issued for testing antimicrobial susceptibility with safe drugs in pregnant women so that these can be used for the treatment. For empirical treatment cefoperazone-sulbactum can be recommended, which is a safe drug, covering both gram positive and gram negative organisms and with a good sensitivity.

Isolation ofStaphylococcus simulansfrom Dermatitis in a Captive African Pygmy Hedgehog

Staphylococcus simulans, a coagulase-negative staphylococcal species, can cause several diseases in humans and animals. This report describes a case of dermatosis characterized by broad, well-circumscribed hyperkeratosis and alopecia on the back of a household pygmy hedgehog (Erinaceous albiventris). Quills and exudates were studied by microscopy. The microscopic examination of the exudates collected from the lesion revealed several leukocytes and numerous gram-positive cocci. An aerobic bacterial culture revealed overgrowth of the same gram-positive bacteria. The bacterium was identified as S. simulans by polymerase chain reaction amplification and direct sequencing targeted to the 16S ribosomal RNA gene. This report is the first to show that S. simulans could be related to the dermatitis of hedgehogs.

Evaluation of resistance of commonly used antibiotics on clinical case of staphylococcus capitis from Assir region, Saudi Arabia

Staphylococcus capitis is a coagulase-negative species (CoNS) of Staphylococcus. It causes antimicrobial resistance for nosocomial infections as well as for community-acquired infections. This case report involves a 51-year-old, married Saudi patient. He got admitted to the male medical ward of Aseer Central Hospital, with severe chest infection. Clinical examination, X-ray, and laboratory investigations were performed which involved bactech, culture media, antibiotic sensitivity test using disk diffusion [minimum inhibitory concentration (MIC)] and molecular [polymerase chain reaction (PCR)] for detection of CoNS of Staphylococcus species and detection of the mecA gene. Laboratory data were recorded in special formats and analyzed by statistical computer program (SPSS). Results showed the resistance of isolated S. capitis to many commonly used antibiotics.

Coagulase-negative staphylococcus--oftentimes a virulent masquerader

To the Editor, Septic arthritis caused by Staphylococcus lugdunensis, a coagulase-negative species, is a rare entity. As of 2008, there were only 58 confirmed cases [1] of bone and joint infections caused by this particular staphylococcal species, potentially due to the fact that many microbiology labs identify but do not speciate coagulase-negative staphylococcus [2]. Despite the presence of confirmed cases of bone and joint infections due to S. lugdunensis in the literature, we believe that this is the first case of septic arthritis caused by this organism in ESRD patients with long-term indwelling venous catheters. We present our observations below. A 60-year-old African American male with ESRD and an indwelling venous catheter for access presented to his primary care physician with a 2-week history of pain, swelling and warmth in his right knee. He reported a low-grade fever of 100°F. He was initially treated with prednisone by his primary care physician, and due to unresolving symptoms, he underwent an arthrocentesis which showed 46 333 cells per cubic millimeter, no visible crystals, and cultures that grew a coagulase-negative staphylococcal species, later identified as S. lugdunensis. As such, the patient was admitted. Blood cultures drawn from the indwelling venous catheter grew identical organisms, and antibiotics were started empirically in the form of vancomycin. Orthopedic consultation was obtained, and the patient underwent arthroscopic irrigation and debridement of the right knee, during which frank pus was noted within the right knee. Knowing that S. lugdunensis is a virulent pathogen, we performed an echocardiogram showing vegetation in the mitral valve leaflet which indicated a subacute versus an old, healed vegetation [3]. In our patient with septic arthritis, the source for S. lugdunensis was most likely the indwelling venous catheter as it grew the identical organism. What is striking about this organism is that in contrast to other coagulase-negative species, S. lugdunensis has been associated with aggressive infections likely due to the fact that it shares many of its virulence factors with Staphylococcus aureus such as proteases, lipases and hemolysins [1,4]. A learning point from this case is to ask microbiology labs to speciate out coagulase-negative staphylococci in the appropriate clinical scenario. The likelihood of S. lugdunensis isolated from a clinical culture specimen being a pathogen versus a contaminant varies anywhere from 91% to 30% according to published data [5]. Missing S. lugdunensis could be catastrophic for the patient, as the bacteria can cause acute endocarditis, septic arthritis and vertebral discitis, especially since the bacteria is usually pan-sensitive to antibiotics. As microbiology labs speciate more coagulase-negative staphylococci, we are likely to identify S. lugdunensis more frequently in clinical infection.

Lectura interpretada del antibiograma de cocos gram positivos

Resistance to methicillin in Staphylococcus is related to the expression of the mecA gene, and involves resistance to all beta-lactams, with the exception of the new cephalosporins, ceftobiprole and ceftaroline. Breakpoints for interpretation of this mechanism differ in S. aureus and in coagulase-negative species. For macrolides-lincosamides-streptogramins B, (MLS(B)) the most frequent mechanism among resistant strains is expression of methylases (erm genes). Topoisomerase changes caused by point mutations and expression of the efflux pump NorA determine resistance to quinolones, but there are great differences in the activity of different compounds, which makes interpretative reading difficult. Strains of S. aureus with intermediate susceptibility to glycopeptides (GISA strains) have been described, as well as highly-vancomycin-resistant isolates (vanA isolates). In Spain, there is a high percentage of S. pneumoniae strains intermediate or resistant to penicillin, and a low percentage of strains intermediate or resistant to third generation cephalosporins, due to mutations in genes encoding penicillin-binding proteins. The most frequent phenotype of resistance to MLS(B) in this species is caused by methylase production. Resistance to quinolones is still uncommon, and is mainly related to mutations in parC/parE (low level) and in gyrA. It is important to detect low level resistance due to its clinical implications. No strains of S. pyogenes resistant to penicillin have yet been described. In Spain the most common phenotype of resistance to macrolides in S. pyogenes is determined by efflux pumps (mef genes), affecting 14- and 15-membered macrolides. E. faecalis is usually susceptible to ampicillin, in contrast to E. faecium. Enterococci show intrinsic low-level resistance to aminoglycosides, but still remain susceptible to the combination of these antimicrobials and cell-wall active agents. Strains expressing different aminoglycoside-modifying enzymes (high-level resistance) became resistant to the combination. Glycopeptide-resistant strains of enterococci are uncommon in Spain, but nosocomial outbreaks due to vanA enterococci and case reports due to vanB2 enterococci have been recently reported.

Fbl gene as a species‐specific target for Staphylococcus lugdunensis identification

Staphylococcus lugdunensis is an unusually virulent coagulase-negative species, associated with severe infections. The present report describes the development of a single-step, species-specific PCR protocol for S. lugdunensis identification. fbl gene, encoding a fibrinogen-binding adhesin, was exploited and assessed as a suitable nucleic acid target. The gene was detected in all 17 S. lugdunensis isolates examined, while no amplification product was obtained from 98 isolates representing 11 staphylococcal and 17 nonstaphylococcal species. Forty-seven percent of the S. lugdunensis strains produced a positive slide coagulase reaction, which is consistent with varying levels of Fbl protein expression within the species.

Recurrent Staphylococcus lugdunensis Infective Endocarditis and Review of the Literature

Abstract Coagulase-negative staphylococcal species are generally considered commensal inhabitants of the skin. Often regarded as avirulent organisms, certain species such as Staphylococcus lugdunensis have been identified as the cause of severe human infections including infective endocarditis. We report on a case of a native valve, S. lugdunensis infective endocarditis relapse after initial conservative medical therapy. A literature review of the outcomes of treatment was also performed. Analyzing definitive medical versus medical-surgical treatment of native valve infective endocarditis, an odds ratio of mortality of 3.1875 (95% confidence interval [CI], 1.1855-8.5705; P < 0.03) was obtained and was significant based on 2-tailed Fisher exact probability test. This analysis reveals an increase risk of mortality with medical therapy alone versus medical-surgical therapy for native valve infective endocarditis. Our case and review of the literature emphasize the growing evidence that early medical treatment and surgical evaluation and removal of infected foreign hardware is required to prevent significant morbidity and mortality.

Antimicrobial susceptibility of Staphylococci isolated from naturally occurring canine external ocular diseases

The purpose of this study was to describe the species distribution and antimicrobial susceptibility patterns of Staphylococci isolated from naturally occurring canine ocular diseases. SAMPLES AND PROCEDURES: Samples obtained from 68 dogs with signs of external eye disease were processed for isolation of bacteria of the genus Staphylococcus sp. Isolates were identified by biochemical reactions and tested for susceptibility to 11 antimicrobials of six classes. Forty (58.8%) samples yielded Staphylococcus sp. in pure culture. Coagulase-positive Staphylococci were most common and Staphylococcus intermedius was the most frequent (45%) species, followed by S. aureus (22.5%) and the coagulase-negative species S. epidermidis (20%), and S. simulans (12.5%). Resistance to at least one drug was observed in 92.5% of the isolates, and multidrug resistance was a common finding (72.5%). The most effective drugs against Staphylococcus strains isolated from extra-ocular canine ocular diseases were ceftiofur and cefalexin. This study highlights the presence of Staphylococcus sp. genus in naturally occurring extra-ocular canine ocular disease and the emergence of resistant strains to common antimicrobial drugs. It also emphasizes the need for bacterial culture with species identification and susceptibility testing in order to choose the appropriate antimicrobial therapy.

Muscle-flap salvage of prosthetic dural repair

A critical element in the prevention of wound and cerebrospinal fluid (CSF) infections after craniotomies is the prevention of postprocedural CSF leaks. The salvage of infected prosthetic dural material in this milieu is not adequately addressed in the literature and is the subject of this study. We performed a 7-year retrospective review of the Yale-New Haven Hospital patient records to identify successful salvage strategies in patients with relentless CSF leaks. Twenty data points were collected, including original diagnosis, nature of the procedure, presence of dural graft, definitive treatment of the leak, culture results and pre- and postoperative antibiotics. Thirteen patients experienced post-craniotomy CSF leaks that required surgical intervention. The most common cause of the original craniotomy (54% of patients) was an oncological aetiology, followed by ruptured aneurysms or haemorrhage in 31% of the patients. Of the 13 patients experiencing CSF leaks, 76% involved the posterior skull base, and therefore a trapezius muscle flap was used in 38% of the cases. The Bovine pericardial graft (10 our of 13), a nonautologous graft, was left intact, and CSF drainage procedures were employed in most patients Growth of gram-positive organisms on cultures was found in 76% of the cases. The most frequent offenders were Staphylococcus aureus (five of the 13), coagulase-negative staphylococcal species (two out of 13), and methicillin-resistant S. aureus (two out of 13). Vancomycin was administered in all cases preoperatively. All 13 patients who underwent open surgery for CSF leak had complete resolution of the leak without need for additional reconstructive surgical intervention. Comprehensive method of treating CSF leaks in conjunction with the salvage of bovine pericardial dural grafts may be a viable clinical option.

Ventriculitis due to Staphylococcus lugdunensis: two case reports

IntroductionStaphylococcus lugdunensis is an unusually virulent coagulase-negative staphylococcus that has rarely been implicated in central nervous system infections.Case presentationTwo children hospitalized in the Neurosurgery Unit developed ventriculitis caused by methicillin-resistant Staphylococcus lugdunensis following placement of external ventriculostomy drains. The causative organisms were identified by molecular studies. The patients recovered without significant sequelae after high doses of intrathecal vancomycin.ConclusionDistinguishing Staphylococcus lugdunensis from other coagulase-negative staphylococcus species is crucial because it carries a substantial risk for severe central nervous system infections displayed by patients with implanted cerebrospinal fluid devices. Clinicians should not underestimate the importance of the isolation of this species from cerebrospinal fluid specimens.

Detección automática de bacterias y hongos en sangre

La sepsis es una de las principales causas de mortalidad y morbilidad en los hospitales. La detección temprana de los patógenos mediante técnicas basadas en ácidos nucleicos puede facilitar el diagnóstico rápido de la bacteriemia y/o fungemia, la rápida adecuación del tratamiento antibiótico, reducir el uso de antibióticos innecesarios y disminuir la mortalidad. Se describen 2 técnicas disponibles comercialmente que ayudan, en un tiempo reducido, a identificar distintas bacterias y hongos productores de sepsis: LightCycler® SeptiFast Test Mgrade (Roche Diagnostic SL) y GenoType Blood Culture (Hain Lifescience). De estas 2 técnicas, mostramos los resultados de un estudio inicial propio con el LightCycler® SeptiFast Test Mgrade. El estudio se realizó con 50 muestras correspondientes a 28 pacientes (1-3 muestras por paciente) con síndrome séptico ingresados en la unidad de cuidados intensivos, comparando la nueva técnica con el hemocultivo convencional. La concordancia entre los resultados del hemocultivo y el SeptiFast fue buena, 79% en el primer ensayo, y 89% en el segundo, después de corregir defectos técnicos. Inicialmente se observó inhibición importante de los controles internos para los bacilos gramnegativos, por la presencia de heparina en la sangre empleada y un exceso de ácido desoxirribonucleico (ADN) debido al número de leucocitos. Con la finalidad de disminuir las inhibiciones, en otro estudio posterior se trabajó con 24 muestras a la mitad de volumen original, llevando el ácido nucleico extraído a dilución 1:4. Con estas modificaciones, se apreciaron reducciones importantes de las inhibiciones. En comparación con el hemocultivo, el SeptiFast diferencia mejor las contaminaciones por estafilococos coagulasa-negativa y especies de estreptococos.

Staphylococcus lugdunensis — Not the Average Coagulase-Negative Staphylococcus Species

Staphylococcus lugdunensis is an unusually virulent coagulase-negative staphylococcal species with unique clinical and microbiological properties. S. lugdunensis is a skin commensal, as well as a pathogen with a propensity to cause highly aggressive and destructive infections that clinically resemble those caused by Staphylococcus aureus, including native valve endocarditis. Aside from endocarditis, S. lugdunensis infections include skin and soft tissue infection and prosthetic joint infection. Some isolates produce a membrane-bound form of coagulase that may result in misidentification of S. lugdunensis as S. aureus in the clinical laboratory. Unlike other coagulase-negative staphylococci, S. lugdunensis is usually susceptible to most antimicrobial agents, lacks mecA, and shares CLSI antimicrobial susceptibility breakpoints for oxacillin with S. aureus. The virulence factors that contribute to the heightened pathogenicity of S. lugdunensis remain largely undetermined. Recent studies indicate that S. lugdunensis can bind to host tissues or prosthetic surfaces and form biofilms.

Staphylococci in primary skin and soft tissue infections in a Swedish county

Patients with skin and soft tissue infections (SSTI) are frequently encountered in primary health care. The majority are uncomplicated and treated empirically by surgical incision and drainage and/or antibiotics. This strategy may risk delaying the detection of methicillin-resistant Staphylococcus aureus (MRSA), which, although still rare in Sweden, is increasingly being found in patients with SSTI. To avoid 'late detection' of MRSA, primary health care physicians in Kronoberg county, Sweden, were asked to perform a culture as soon as the patient's first visit. Samples from 175 patients with primary SSTI confirmed that S. aureus is the dominant pathogen. Two cases of MRSA were detected. Furthermore, isolates of S. aureus producing the Panton-Valentine leukocidin (PVL) toxin were more common among isolates from SSTI than among S. aureus from secondary infections. Finally, we confirmed the importance of the coagulase-negative staphylococcal species S. lugdunensis as a pathogen as it was isolated as the only pathogen in 10% of the skin and soft tissue samples.

Intravenously administered pharmaceuticals impact biofilm formation and detachment of Staphylococcus lugdunensis and other staphylococci

Coagulase-negative staphylococci and Staphylococcus aureus are major causes of catheter-related infections because of their ability to form biofilms on indwelling polymeric devices. Staphylococcus lugdunensis is a particularly virulent coagulase-negative species responsible for several types of biofilm-related infections, but factors that influence biofilm formation by this species remain undetermined. Heparin and catecholamine inotropes are common intravenously administered drugs reported to stimulate biofilm formation of some staphylococci. This study assessed the effects of catecholamines and heparin on biofilm formation of a collection of S. lugdunensis isolates and other Staphylococcus species. Dopamine stimulated biofilm formation in two-thirds of S. lugdunensis isolates, whereas dobutamine prevented nearly all S. lugdunensis isolates from adhering to polystyrene. Heparin markedly reduced biofilm formation by 87% of S. lugdunensis isolates. Preformed biofilms of S. lugdunensis and other Staphylococcus species detached from polystyrene after exposure to heparin at concentrations used in catheter locks. Our data suggest that intravenous pharmaceuticals may influence staphylococcal biofilm formation on and detachment from intravascular catheters.

Theatre Shoes — A Link in the Common Pathway of Postoperative Wound Infection?

Operating department staff are usually required to wear dedicated theatre shoes whilst in the theatre area but there is little evidence to support the beneficial use of theatre shoes. We performed a study to assess the level of bacterial contamination of theatre shoes at the beginning and end of a working day, and compared the results with outdoor footwear. We found the presence of pathogenic bacterial species responsible for postoperative wound infection on all shoe groups, with outdoor shoes being the most heavily contaminated. Samples taken from theatre shoes at the end of duty were less contaminated than those taken at the beginning of the day with the greatest reduction being in the number of coagulase-negative staphylococcal species grown. Studies have demonstrated that floor bacteria may contribute up to 15% of airborne bacterial colony forming units in operating rooms. The pathogenic bacteria we isolated have also been demonstrated as contaminants in water droplets spilt onto sterile gloves after surgical scrubbing. Theatre shoes and floors present a potential source for postoperative infection. A combination of dedicated theatre shoe use and a good floor washing protocol controls the level of shoe contamination by coagulase-negative staphylococci in particular. This finding is significant given the importance of staphylococcal species in postoperative wound infection.

New recommendations in the treatment of Gram-positive bacteraemia in dialysis patients

There is a progressive increase in community and nosocomial infections caused by Gram-positive pathogens, which often result in bacteraemia resistant to antibiotics. Many Gram-positive bacteria, including coagulasenegative staphylococci, Staphylococcus aureus and enterococcus species, may colonize the skin, mucous membranes (particularly anterior nares) and lower bowel of most normal subjects. In general, these bacteria do not incur consequences to the host, as the intact cornified squamous epithelium can prevent their access to subcutaneous tissues and blood. Only when the skin or mucous membranes are disrupted, may staphylococci give rise to localized superficial abscesses. Cutaneous infections are often self-limited, because normal subjects can organize a primary defence based on neutrophils and opsonophagogytosis. Nevertheless, if bacteria invade the lymphatics and the blood, they can cause a number of life-threatening complications such as septic shock, endocarditis, pneumonia, osteomyelitis, etc. The leading pathogens are coagulase-negative staphylococci and S. aureus, followed by enterococcus species [1]. The coagulase-negative staphylococci such as Staphylococcus epidermidis have been considered as avirulent commensals in the past. However, in the last 30 years, they have been recognized to be one of the most frequent pathogens responsible for nosocomial infection, with a high rate of mortality. The development of bacteraemia is largely influenced by factors such as (i) the use of catheters that can disrupt the cutaneous barrier to Gram-positive pathogens; (ii) a heavy colonization at mucocutaneous sites, that is favoured by wounds, traumas, ulcers, etc; (iii) the virulence of the pathogen including its ability to produce enzymes

Staphylococcus pettenkoferi sp. nov., a novel coagulase-negative staphylococcal species isolated from human clinical specimens

Five coagulase-negative, novobiocin-susceptible staphylococcal strains were isolated from human blood cultures in different German and Belgian medical facilities. A novel species, 'Staphylococcus pettenkoferi' was proposed recently to accommodate two of these strains (B3117(T) and A6664), although the name was not validly published. All five strains belonged to the genus Staphylococcus because they were non-motile, Gram-positive, catalase-positive cocci with peptidoglycan type (A3 alpha type L-lys-gly(2-4)-L-Ser-Gly), menaquinone pattern (MK-7, MK-6 and MK-8) and major cellular fatty acids (ai-C(15 : 0), ai-C(17 : 0) and i-C(15 : 0)) that corresponded to those of staphylococci. Phenotypically, the isolates most closely resembled Staphylococcus capitis subsp. capitis and Staphylococcus auricularis, but they could be distinguished from these species by physiological tests and chemotaxonomic investigations. The results of DNA-DNA hybridization, chemotaxonomic investigations and 16S rRNA gene and RNA polymerase B gene (rpoB) sequence analysis enabled strains B3117(T), K6999, 229 and 230 to be differentiated genotypically and phenotypically from known Staphylococcus species, indicating that these isolates are representatives of a novel species. The name Staphylococcus pettenkoferi sp. nov. is proposed for this novel species, with strain B3117(T) (=CIP 107711(T)=CCUG 51270(T)) as the type strain. Due to differences in the results of physiological and chemotaxonomic investigations and DNA-DNA hybridization data, strain A6664 was not included in the description of the novel species.

In Vitro Effects of Antimicrobial Agents on Planktonic and Biofilm Forms of Staphylococcus lugdunensis Clinical Isolates

Staphylococcus lugdunensis is an atypically virulent coagulase-negative staphylococcal species associated with acute and destructive infections that often resemble Staphylococcus aureus infections. Several types of infection caused by S. lugdunensis (e.g., native valve endocarditis, prosthetic joint infection, and intravascular catheter infection) are associated with biofilm formation, which may lead to an inability to eradicate the infection due to the intrinsic nature of biofilms to resist high levels of antibiotics. In this study, planktonic MICs and MBCs and biofilm bactericidal concentrations of 10 antistaphylococcal antimicrobial agents were measured for 15 S. lugdunensis isolates collected from patients with endocarditis, medical device infections, or skin and soft tissue infections. Planktonic isolates were susceptible to all agents studied, but biofilms were resistant to high concentrations of most of the drugs. However, moxifloxacin was able to kill 73% of isolates growing in biofilms at </=0.5 mug/ml. Relative to the effect on cell density, subinhibitory concentrations of nafcillin substantially stimulated biofilm formation of most isolates, whereas tetracycline and linezolid significantly decreased biofilm formation in 93 and 80% of isolates, respectively. An unexpected outcome of MBC testing was the observation that vancomycin was not bactericidal against 93% of S. lugdunensis isolates, suggesting widespread vancomycin tolerance in this species. These data provide insights into the response of S. lugdunensis isolates when challenged with various levels of antimicrobial agents in clinical use.

Clinical characteristics and persistence of bovine mastitis caused by different species of coagulase-negative staphylococci identified with API or AFLP

The coagulase-negative staphylococcal species causing mastitis in lactating cattle were identified and possible differences in the clinical characteristics or persistence of mastitis caused by different CNS were evaluated. The effect of antimicrobial treatment was also assessed. In addition, AFLP-typing of CNS was compared with the phenotypic identification. A total of 133 clinical or subclinical quarter cases of intramammary infection caused by CNS from the practice area of the Ambulatory Clinic of the University of Helsinki were studied. Bacteriological diagnosis was based on biochemical (API) testing. Staphylococcus simulans (43.6%) followed by S. chromogenes (23.3%) were the most common CNS species isolated from the milk samples. Ninety-nine isolates were genotyped using AFLP-analysis. Only 75.0% of S. chromogenes and S. simulans isolates identified with API test were clustered with the type strains of these species. Approximately half of the mastitis cases were clinical, and in the majority clinical signs were mild. The severity and persistence of intramammary infection were unaffected by CNS species. Fifty-nine percent of the quarter cases were treated with antimicrobials, and the rest were left without treatment. Mastitis due to β-lactamase-negative CNS was treated with penicillin G and that due to β-lactamase-positive CNS with cloxacillin. Nineteen percent of the isolates were β-lactamase-positive. The bacterial cure rate for quarters treated with antimicrobials was high, 85.9%, as opposed to only 45.5% for untreated quarters. Bacterial cure rates for the most common CNS species or AFLP clusters were not statistically different. Further studies on identification of CNS species are needed.