Different Species Of Coagulase-negative Staphylococci Research Articles

Characterization of Chlorhexidine Resistance Among Clinical Isolates of Coagulase-Negative Staphylococcus Species in a Tertiary Care Center, Chennai.

Background Coagulase-negativeStaphylococci(CoNS) are potential pathogens and are often associated with healthcare-associated infections (HAIs). Chlorhexidine (CHX) is the most widely used antiseptic to reduce colonization and infection by allStaphylococci, including CoNS. Resistance to CHXamong CoNS has been observed over the past few years, consequent to its widespread use. Phenotypic tolerance or reduced susceptibility to CHX is conferred by plasmid-mediatedqacgroup of genes, mainlyqacA/Bandsmr, which cause activation of efflux pumps over the bacterial cell wall. This study aims to characterize the phenotypic and genotypic resistance exhibited by CoNS species against CHX. Methods After ethical approval, 148 consecutive, non-repetitive isolates of clinically significant CoNS species of hospitalized patients, isolated from blood samples and exudative specimens, were included in the study. Speciation was performed by conventional biochemical identification and automated methods. Antimicrobial susceptibility testing was performed by disc diffusion technique and for vancomycin by minimum inhibitory concentration (MIC) determination, as per Clinical Laboratory Standards Institute (CLSI) M-100 2023 guidelines. Methicillin resistance was detected using a cefoxitin disc. MIC for CHX was performed by agar dilution method; reduced susceptibility was considered when MIC to CHX ≥4 µg/mL. The simplex polymerase chain reaction (PCR) was carried out with suitable controls to detectqacA/Bandsmr. Statistical analysis was conducted to determine the association ofqacA/Bandsmrgenes with MIC of CHXin the study isolates. Results Fifteen different species of CoNS were obtained from clinical samples. A high percentage of resistance was observed against various classes of antibiotics. Methicillin resistance was observed in 69.6% (103/148) of isolates. Of 148 CoNS, 52.7% (78/148) of isolates exhibited reduced susceptibility to CHX with an MIC ≥4 µg/mL. These isolates exhibited a higher percentage of methicillin resistance (75.6%, 59/78). By PCR, 34.5% (51/148) of isolates carried either or both genes. GeneqacA/Bwas solely detected in 27.02% (40/148) of isolates, of which 14 were CHX-tolerant and the remaining 26 were CHX-susceptible. Genesmrwas solely detected in 4.1% (6/148) of isolates comprising three isolates each in CHX-tolerant and susceptible categories.There were 3.4% (5/148) of isolates that harbored bothgenes, of which only one isolate was CHX-susceptible, while the other four were CHX-tolerant. A proportion of isolates that were phenotypically tolerant to CHX did not carry either or both genes. A significant statistical association was found between reduced susceptibility to CHX and the presence of antiseptic resistance genesin the study isolates (p-value=0.033942). Conclusion To our knowledge, this is the first study from South India to investigate CHX resistance among CoNS using phenotypic and genotypic methods. The rise of antiseptic resistance among CoNS is an emerging threat to current infection control practices. The presence ofqacA/Bandsmrgenes, especially in CHX susceptible isolates, is concerning since these resistance genes are located on transferable plasmids, and the isolates can develop resistance eventually upon exposure to CHX.

A Microbiological Study on Clinical Isolates of Coagulase-Negative Staphylococci (CoNS) from Sulaimaniyah Hospitals

The purpose of this study was to identify and isolate different coagulase.negative staphylococci (CoNS) species associated with clinical samples with their virulence factors. For this purpose, 355 clinical samples were taken from various Hospitals in Sulaimaniyah city. Different species of CoNS were identified by using (blood, MacConkey, Mannitol salt) agars, biochemical tests, and VITEK® 2 compact system. The phenotypic characterization of hemolysin was based on the hemolysis pattern of CoNS on sheep blood agar. Moreover, the biofilm detection in CoNS was performed by using a microtiter plate (MTP). The various biofilm and virulence genes were detected using specific primers to detect mecA, hla, hlb, hld, hlg and the icaAD, fnbA, and bap genes, respectively. The number of MR-CoNS and MS-CoNS were 31 (96.8%) and 1 (3.1%), respectively, out of 32 isolates. The availability of the mecA gene, responsible for the resistance of CoNS to methicillin, was found in (100%) of CoNS species related to clinical samples. Interestingly, the hemolysin genes were detected on the plasmids instead of the chromosomal DNA, and these results indicated that the CoNS could be the primary cause of nosocomial infection.

Comparison of Methods for Detecting Methicillin-Resistant Coagulase-Negative Staphylococci in Device-Associated Infections

Background: Coagulase-negative Staphylococci (CoNS) is one of the major causes of infections in hospitals. Methicillin resistance has greatly increased in different CoNS species in previous years. Here, we evaluated the performance of four phenotypic tests for detecting mecA-mediated methicillin resistance rate in CoNS isolated from different device-associated infections in Tanta University Hospitals, Egypt. Methodology: One hundred and fifteen CoNS isolates were examined for mecA-mediated methicillin resistance using polymerase chain reaction (PCR) as the standard gold test. Susceptibility to methicillin was investigated using VITEK 2 assay, oxacillin broth microdilution, and cefoxitin disc diffusion tests. Results: Of all isolates, 98.3% were mecA-positive. The sensitivities of the different methods examined were as follows: 100% for the VITEK cefoxitin test, 97.4% for the VITEK oxacillin test, 93.8% for the oxacillin broth microdilution, and 82.3% for the cefoxitin disc diffusion test. The test specificity could not be accurately determined because of the small number of mecA-negative isolates (n = 2). Conclusion: The rate of methicillin resistance reached 98.3% among CoNS isolates. Our results demonstrate that the VITEK 2 assay is rapid and has high sensitivity compared to other phenotypic methods for detecting methicillin resistance among different species of CoNS. Therefore, we recommend the dual measurement of both cefoxitin and oxacillin susceptibilities using the VITEK 2 assay for best results.

Characteristics of resistance and virulence factors in different species of coagulase-negative staphylococci isolated from milk of healthy sheep and animals with subclinical mastitis

Coagulase-negative staphylococci (CNS) are among the main responsible agents for mastitis in sheep. Cure rates can be reduced due to several causes, such as those related to virulence factors presented by microorganisms. This study aims at characterizing the virulence and resistance factors to antimicrobial agents in different CNS species isolated from sheep milk. After collecting milk samples, the samples were analyzed and the CNS species were identified. After identification, the susceptibility-sensitivity profile was examined using the disk diffusion technique for 10 antimicrobial agents. The DNA was extracted to detect the presence of the mecA gene, biofilm (icaADBC, bap, and bhp) and toxin genes (sea, seb, sec, sed, tst, and luk-PV) by PCR. Samples carrying toxin genes had their expression assessed using the reverse-transcription PCR technique. The biofilm production was assessed using the adherence method on a polystyrene plate. One hundred twelve CNS samples were isolated, 53 (47.3%) from animals with subclinical mastitis and 59 (52.7%) from healthy animals. Drugs tested have shown to be efficient for most CNS samples. The largest resistance percentage of CNS was found for the penicillin (17.0%) and tetracycline (10.7%) and 4 samples carried the mecA gene. As for the biofilm genes, the icaADBC operon was found in 10 (8.9%) samples, the bap gene was found in 16 (14.3%), and the bhp gene was found in 3 (2.7%). In addition, 69 (61.6%) samples produced biofilm. The survey of toxin genes has shown that 70 (62.5%) samples showed some toxin-encoding gene. However, none of the samples has expressed any of the genes from those toxins studied.

Exploring the metabolic heterogeneity of coagulase-negative staphylococci to improve the quality and safety of fermented meats: a review

The production of fermented meats, such as fermented sausage, relies on the metabolic activities of lactic acid bacteria and catalase-positive cocci, in particular the group of coagulase-negative staphylococci (CNS). Conventional use of CNS as meat starter cultures usually leads to an appropriate cured colour development based on their nitrate reductase activity, whereas their catalase activity reduces oxidative damage. In addition, CNS metabolism contributes to flavour, although the precise effects are difficult to estimate. There are reasons to believe that these basic technological features of CNS can be further enlarged by exploring their full metabolic potential. Non-negligible differences in metabolism among and within different species of CNS indicate that a rational selection of strains may lead to the development of novel starter cultures with enhanced functionality. Firstly, the use of CNS strains with a superior ability to use alternative energy sources, such as nucleosides or arginine, may improve culture competitiveness and survival. Secondly, cured colour generation could be optimised to lower the amounts of curing salts needed, either by selecting for efficient nitrate-reducing CNS strains or by exploring the potential alternative based on nitric oxide synthase activity. Thirdly, CNS with specific aroma-producing abilities may help to accentuate specific flavours, whereby the selection of wild-type strains from artisan-type fermented sausages seems attractive in the framework of innovation-through-tradition. Finally, bacteriocin-producing CNS strains may offer solutions for bioprotection towards meat pathogens such as Clostridium botulinum and Staphylococcus aureus. Overall, making use of the metabolic inter- and intraspecies heterogeneity of CNS is promising for the elaboration of healthier, tastier, and safer fermented meats. Yet, the proposed strategies are sometimes still overly theoretical and speculative, requiring further proof-of-principle.

Relevance of biofilm formation and virulence of different species of coagulase-negative staphylococci to public health.

The ability of biofilm formation seems to play an essential role in the virulence of coagulase-negative staphylococci (CNS). The present work aimed to: (a) evaluate the biofilm-forming ability of different strains of CNS field isolates; (b) evaluate their virulence potential through the assessment of the Madin-Darby canine kidney (MDCK) cytotoxicity assay; (c) determine the frequency of biofilm-associated genes among these CNS isolates. Biofilm markers associated with biofilm formation and MDCK cells cytotoxicity were compared to find possible associations with pathogenicity. CNS isolates (n = 94) belonging to 11 different species were tested for slime production using the tube test (TA) and the Congo red agar plate test (CRA), while the presence of icaA and icaD genes were evaluated by d-PCR. Two points were addressed for the first time: (1) the specific relationship between slime phenotype and icaD gene expression; (2) the specific relationship between slime phenotype, icaAD genes, and MDCK cytotoxicity. The proportion of biofilm-positive/icaD-positive versus biofilm-positive/icaD-negative strains was 9:0 and 9:0 (81.8%) by the TA and CRA, which clearly indicates that icaD was a more reliable gene to be accounted for in the biofilm formation. MDCK recorded a higher proportion than that recorded by the CRA and TA results (MDCK-positive/icaD-positive versus MDCK-positive/icaD-negative 10:0, 90.9%). Evaluation of the ica operon, CRA plate test, TA, and MDCK can contribute to the high clinical impact in the management of antibiotic therapy, in infections associated with devices in veterinary medicine, the dairy industry, and food processing.

Staphylococcal species associated with bovine mastitis in the North West of Iran: Emerging of coagulase-negative staphylococci

Staphylococcal mastitis is a major and costly problem of dairy cattle all over the world. The objective of this study was to isolate and identify the main staphylococcal species causing bovine mastitis in 7 dairy herds located in 4 different areas of East and West Azerbaijan provinces, Iran. Of the 158 mastitic milk samples collected, 113 staphylococcal isolates were identified (71.5%) on the basis of cultural and biochemical features as well as by genus specific PCR. Then, species level identification of staphylococcal isolates was carried out using restriction fragment length polymorphism (RFLP) analysis of the gap gene (933bp). On the basis of polymerase chain reaction-RFLP, 10 different patterns were identified. Of 113 isolates, 5 (4.4%) were Staphylococcus aureus and 108 (95.6%) were coagulase-negative staphylococci (CoNS). Overall, nine different species of CoNS were identified as: 44 Staphylococcus haemolyticus (40.7%), 17 Staphylococcus chromogenes (15.7%), 11 Staphylococcus epidermidis, Staphylococcus warneri and Staphylococcus cohnii each (10.2%), 6 Staphylococcus simulans (5.5%), 4 Staphylococcus hominis (3.7%), 3 Staphylococcus capitis (2.7%) and 1 Staphylococcus xylosus (0.9%). S. haemolyticus, S. chromogenes and S. warneri were the only species identified from clinical mastitis. No significant difference in staphylococcal IMI was found among the studied herds and regions. This study demonstrated that CoNS, especially S. haemolyticus and S. chromogenes, were predominant and thus be considered as emerging pathogens causing mastitis in the North West of Iran. Our results also revealed that the gap PCR-RFLP was useful for identifying staphylococcal isolates derived from bovine mastitis at species level.

Enterotoxin genes in coagulase-negative and coagulase-positive staphylococci isolated from bovine milk

The objective of this study was to isolate and identify the main staphylococcal species causing bovine mastitis in 10 Brazilian dairy herds and study their capability to produce enterotoxins. Herds were selected based on size and use of milking technology, and farms were visited once during the study. All mammary glands of all lactating cows were screened using the California Mastitis Test (CMT) and a strip cup. A single aseptic milk sample (20mL) was collected from all CMT-positive quarters. Identification of Staphylococcus spp. was performed using conventional microbiology, and PCR was used to determine the presence of enterotoxin-encoding genes (sea, seb, sec, and sed). Of the 1,318 CMT-positive milk samples, Staphylococcus spp. were isolated from 263 (19.9%). Of these isolates, 135 (51%) were coagulase-positive staphylococci (CPS) and 128 (49%) were coagulase-negative staphylococci (CNS). Eighteen different species of CNS were isolated, among which S. warneri, S. epidermidis and S. hyicus were the most frequent. The distribution of Staphylococcus species was different among herds: S. epidermidis was found in 8 herds, S. warneri was found in 7 herds, and S. hyicus in 6 herds. Some of the CNS species (S. saprophyticus ssp. saprophyticus, S. auricularis, S. capitis, and S. chromogenes) were isolated in only one of the farms. Genes related to production of enterotoxins were found in 66% (n=85) of all CNS and in 35% of the CPS isolates. For both CNS and CPS isolates, the most frequently identified enterotoxin genes were sea, seb, and sec; the prevalence of sea differed between CPS (9.5%) and CNS (35.1%) isolates. Staphylococcus warneri isolates showed a greater percentage of sea than seb, sec, or sed, whereas S. hyicus isolates showed a greater percentage of sea than sec. Over 60% of CNS belonged to 3 major species, which carried 62.2 to 81.3% of the enterotoxin genes. The high prevalence highlights the potential for food poisoning caused by these species. For possible high-risk situations for food poisoning, such as milk produced with total bacterial counts greater than regulatory levels and stored under inappropriate temperatures, monitoring contamination with CNS could be important to protect human health. Because the prevalence of CNS intramammary infections in dairy herds is usually high, and these species can be found in great numbers in bulk milk, identification of risk factors for production of staphylococcal enterotoxins should be considered in future studies.

Stethoscopes as vectors of multi-resistant coagulase negative staphylococci in a tertiary hospital

Background: Stethoscopes are an essential tool for physicians, but can be a source of hospital infections. Aims & Objective: The objective was to isolate staphylococci strains from the diaphragms and earpieces of the stethoscopes as well as to characterize their antibiotic resistance. Material and Methods: Forty five stethoscopes from different clinical doctors were sampled in a tertiary hospital. The swab method was used and the swabs were immediately inoculated on blood agar and manitol salt agar. The bacterial identification and the antibiotic resistance were performed according to the CLSI with automated commercial system. Results: Pathogenic or potential pathogenic Coagulase Negative Staphylococci (CoNS) were isolated on physician’s stethoscopes. CoNS were isolated in 87.6% of the stethoscopes. S.epidermidis was the predominant isolate species of CoNS (39.4%) followed by S.hominis (19.7%), S.auricularis (9.8%), S. haemolyticus (8.4%), S.warneri (7%), S. cohnii (5.6%), S. lugdunensis (4.2%), S. capitis (4.2%), S.hyicus (1.4%). The isolated CoNS have high resistance rate in penicillin (74.6%), antibiotic macrolidess (60.5%), clindamycin (39.4%), oxacillin (30.9%) and gentamycin (22.4%). The co-resistance of S.epidermidis for methicillin-gentamicin was 59.2%. Multi-resistant strains of CoNS were 16.9% and belong to the species of S.epidermidis, S.hominis and S.haemolyticus. Conclusion: The study demonstrates the contamination of the stethoscopes with different species of CoNS which showed high antibiotic resistance and possess the potential risk of causing hospital infections. As severe hospital infections, especially in population at risk caused by different species of CoNS, are increasing; their characterization at the species level as well as their resistance pattern in patients and medical devices is strongly suggested.

Diversity of staphylococcal cassette chromosome in coagulase-negative staphylococci from animal sources

To type the staphylococcal cassette chromosome (SCC) in coagulase-negative staphylococci (CoNS) from animal sources. A total of 92 CoNS isolates recovered from farm animals was analysed. The top three staphylococcal species were Staphylococcus lentus (34), S. sciuri (31), and S. xylosus (13). The presence of the cassette chromosome recombinase (ccr) genes ccrA1, ccrB1, ccrA2, ccrB2, ccrA3, ccrB3 and ccrC, the mec regulatory genes mecI and mecR1, and Tn554 was used to differentiate the SCC. A total of 60 of the 92 isolates were methicillin resistant. Among the 60 methicillin-resistant Staphylococcus spp. isolates, SCCmec (mecA-carrying SCC) types I, III, IV and V were identified in 24 isolates based on the combinations of the ccr genes and the mec regulatory genes, with type III being predominant. The single S. epidermidis carried SCCmec type IV. SCC type III was also identified in two of 32 methicillin-susceptible isolates. Identical SCCmec types were present in different species of CoNS. Pulsed-field gel electrophoresis (PFGE) generated 64 patterns out of 81 PFGE typeable isolates. Indistinguishable clones were detected in animals from different farms. Heterogeneous SCC existed in CoNS of diverse genetic background. Both clonal transmission of methicillin-resistant CoNS and horizontal transfer of SCCmec occurred in the animal production environment. This study adds to our knowledge of SCCmec type and the diversity of SCC in CoNS.

The quest for the perfect test: Phenotypic versus genotypic identification of coagulase-negative staphylococci associated with bovine mastitis

Coagulase-negative staphylococci (CNS) are a frequent cause of bovine intramammary infection and the objective of this paper is to discuss the utility of phenotypic identification systems used for species identification of CNS relative to use of genotypic identification. Mastitis control programs have been developed for major mastitis pathogens but few are specifically targeted for control of CNS. Few documented differences in treatment outcomes of mastitis caused by different species of CNS have been published, and at least one study has reported no differences in bacterial cures of mastitis caused by CNS based on genotypic identification. A number of commercial identification kits for species identification of CNS have been evaluated by mastitis researchers. Most phenotypic systems are considered to accurately identify >80% of staphylococci but have not been designed to detect all taxa that have been associated with bovine mastitis. Typical results were observed in the evaluation of agreement between 2 systems used for identification of staphylococci ( n = 54) isolated from cases of mastitis. Satisfactory agreement (Kappa > 0.87) was achieved for API Staph but low agreement at the species level was seen for the BBL Crystal Gram-Positive system (Kappa = 0.25). Results of this small study are typical of similar studies and confirm that differences occur among phenotypic identification systems. In spite of the limited precision of some phenotypic identification systems, their consistent use with an adequate number of isolates in the diagnostic algorithm is probably sufficient for most mastitis control programs, which are currently not based on species level identification. However, genotypic identification will be useful for advancing knowledge of the role of CNS in bovine mastitis.

Comparison of a commercialized phenotyping system, antimicrobial susceptibility testing, and tuf gene sequence-based genotyping for species-level identification of coagulase-negative staphylococci isolated from cases of bovine mastitis

In order to evaluate the usefulness of some phenotypic and genotypic methods for species identification of coagulase-negative staphylococci (CNS), isolates were obtained from bovine cases of clinical and sub-clinical mastitis from different geographical areas in Sweden. By using the Staph-Zym™ test, antimicrobial susceptibility testing, and sequencing of part of the CNS tuf gene and, when needed, part of the 16S rRNA gene we characterized 82 clinical isolates and 24 reference strains of 18 different species of staphylococci. The genotypic methods identified nine different species of CNS among the 82 milk isolates. A comparison with results obtained by tuf gene sequencing showed that Staph-Zym™ correctly identified CNS reference strains to species level more often than bovine milk CNS isolates (83% and 61%, respectively). In addition, tests supplementary to the Staph-Zym™ were frequently needed in both groups of isolates (50% of reference strains and 33% of milk isolates) to obtain an identification of the strain. It is notable that Staph-Zym™ judged two isolates as CNS, although they belonged to other species, could not give a species name in 11% of the bovine CNS isolates, and gave 28% of the isolates an incorrect species name. The present study indicates that the studied phenotypic methods are unreliable for identification of CNS from bovine intra-mammary infections.

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.

Widespread Distribution of Disinfectant Resistance Genes among Staphylococci of Bovine and Caprine Origin in Norway

We demonstrate here a widespread distribution of genes mediating efflux-based resistance to quaternary ammonium compounds (QACs) in staphylococci from unpasteurized milk from 127 dairy cattle herds and 70 dairy goat herds. QAC resistance genes were identified in 21% of the cattle herds (qacA/B, smr, qacG, and qacJ) and in 10% of the goat herds (qacA/B and smr). Further examination of 42 QAC-resistant bovine and caprine isolates revealed the following genes: qacA/B (12 isolates) was present in four different species of coagulase-negative staphylococci (CoNS), smr (27 isolates) was detected in eight different CoNS species and in Staphylococcus aureus on a previously reported plasmid (pNVH99), qacG (two isolates) was detected on two plasmids (pST94-like) in Staphylococcus cohnii and Staphylococcus warneri, and qacJ (two isolates) was found in Staphylococcus hominis and Staphylococcus delphini on a plasmid (pNVH01) previously found in equine staphylococci. Isolation of indistinguishable pulsed-field gel electrophoresis (PFGE) CoNS types from tank milk and mammary quarter milk samples in a dairy cattle herd suggested that these QAC-resistant staphylococci were of intramammary origin. Indistinguishable or closely related PFGE types of bovine QAC-resistant CoNS were observed in different herds. One particular bovine S. warneri PFGE type was isolated repeatedly from samples collected during a 30-month period in a herd, showing long-term persistence. In conclusion, it seems that the widespread distribution of staphylococci carrying QAC resistance genes in Norwegian dairy cattle and goat herds is the result of both the intra- and interspecies spread of QAC resistance plasmids and the clonal spread of QAC-resistant strains.

A particle agglutination assay for rapid identification of heparin binding to coagulase-negative staphylococci.

The heparin-binding properties of six different species of coagulase-negative staphylococci were examined by a particle agglutination assay. Heparin (mol. wt 4000-6000), mildly treated with sodium periodate, was covalently coupled to amino-modified latex beads (0.72 micron diameter). The particle agglutination assay was validated by comparing results with the adhesion (percentage binding of adherent cells) of coagulase-negative staphylococcal strains to heparinised microtitration plates. Of 38 different coagulase-negative staphylococcal strains tested, 30 showed agglutination reactivity with heparin-coated latex beads. Strains of different coagulase-negative staphylococcal species agglutinated heparin-coated latex beads to various extents (e.g., cells of Staphylococcus haemolyticus strains reacted more strongly than cells of S. epidermidis strains). The agglutination reaction was significantly inhibited by fucoidan, suramin, lambda-carrageenan and other sulphated compounds, but not by non-sulphated carbohydrate polymers such as hyaluronic acid. Agglutination of staphylococcal cells with heparin-coated latex beads was completely blocked by a cell-surface extract. These results suggest that structures responsible for heparin binding are exposed on the cell surface.

Contaminated rabbit patellar tendon grafts. In vivo analysis of disinfecting methods.

In Part 1 of our study, 40 central-third bone-patellar tendon-bone grafts were harvested from 20 adult California White rabbits under strict sterile conditions. Ten grafts were placed directly into a thioglycolate broth, incubated, and subcultured; no growth was noted in any specimen. The next 6 grafts were contaminated 20 seconds each with 2 different species of coagulase-negative staphylococci. Organisms were grown with cultures obtained from an operating room floor during anterior cruciate ligament reconstruction. Marked growth of both species was noted in all 6 grafts within 24 hours. A subsequent 3 series of 8 grafts each were harvested sterilely, contaminated as described above, and soaked in 1 of 3 solutions 30 minutes before culture. Both 10% povidone-iodine and a triple-antibiotic solution (gentamicin, clindamycin, polymyxin) were 100% ineffective as both organisms grew; 4% chlorhexidine gluconate effectively decontaminated 8 grafts in all cases. Part 2 involved contamination of harvested grafts with 5 common, virulent organisms: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterococcus faecalis. Elimination of all except Klebsiella pneumoniae was successful with 4% chlorhexidine gluconate alone for 8 grafts. Using a triple-antibiotic solution after chlorhexidine gluconate in 6 grafts eliminated this organism also.

Risk of Bacteremia Induced by Transesophageal Echocardiography: Analysis of 100 Consecutive Procedures

The incidence of bacteremia induced by transesophageal echocardiography (TEE) and, consequently, the need for an antibiotic prophylaxis before TEE is still controversial. Therefore, we studied the incidence of bacteremia associated with TEE prospectively in 100 consecutive patients without clinical or laboratory signs of bacterial infection. Blood samples were drawn immediately before and at 0, 5, and 15 minutes after TEE. In addition, swabs were taken from the pharyngeal region before TEE and from the distal part of the TEE-probe before and after TEE. All blood cultures taken before TEE remained sterile. After TEE, three positive blood cultures were found in two patients: the first patient had two different species of coagulase-negative staphylococci in cultures taken at 0 minutes (Staphylococcus capitis) and 15 minutes (Staphylococcus cohnii) after TEE, whereas the sample taken after 5 minutes remained sterile. In the second patient, Propionibacterium species appeared after 7 days of processing in a culture taken immediately after TEE, but not in the samples taken after 5 and 15 minutes. None of the three microorganisms found in the blood were simultaneously isolated in pharyngeal specimens or TEE-probe specimens of the same patient. Thus positive blood cultures in both patients were considered contaminated. This study demonstrates that TEE, when performed by an experienced investigator, is not associated with an increased risk of bacteremia. Accordingly, it is justified to perform TEE examinations (also in high-risk patients) without antibiotic prophylaxis.

Prevalence of different species of coagulase-negative staphylococci on teats and in milk samples from dairy cows.

Prevalence of different species of coagulase-negative staphylococci on teats and in milk samples from dairy cows.