Cytotoxic activity of coagulase-negative staphylococci in bovine mastitis

Genomic features and pathophysiological impact of a multidrug-resistant Staphylococcus warneri variant in murine mastitis

Non-aureus staphylococci (NAS) represent a major etiological agent in dairy animal mastitis, yet their role and impact remain insufficiently studied. This study aimed to elucidate the genomic characteristics of a newly identified multidrug-resistant NAS strain, specifically Staphylococcus warneri G1M1F, isolated from murine feces in an experimental mastitis model. Surprisingly, NAS species accounted for 54.35 % of murine mastitis cases, with S. warneri being the most prevalent at 40.0 %. S. warneri G1M1F exhibited resistance to 10 major antibiotics. Whole-genome sequencing established a genetic connection between G1M1F and S. warneri strains isolated previously from various sources including mastitis milk in dairy animals, human feces and blood across diverse geographical regions. Genomic analysis of S. warneri G1M1F unveiled 34 antimicrobial resistance genes (ARGs), 30 virulence factor genes (VFGs), and 278 metabolic features. A significant portion of identified ARGs (64 %) conferred resistance through antibiotic efflux pumps, while VFGs primarily related to bacterial adherence and biofilm formation. Inoculation with G1M1F in mice resulted in pronounced inflammatory lesions in mammary and colon tissues, indicating pathogenic potential. Our findings highlight distinctive genomic traits in S. warneri G1M1F, signifying the emergence of a novel multidrug-resistant NAS variant. These insights contribute to understanding NAS-related mastitis pathophysiology and inform strategies for effective treatment in dairy animals.

Advances in Diagnostic Approaches and Therapeutic Management in Bovine Mastitis

Mastitis causes huge economic losses to dairy farmers worldwide, which largely negatively affects the quality and quantity of milk. Mastitis decreases overall milk production, degrades milk quality, increases milk losses because of milk being discarded, and increases overall production costs due to higher treatment and labour costs and premature culling. This review article discusses mastitis with respect to its clinical epidemiology, the pathogens involved, economic losses, and basic and advanced diagnostic tools that have been used in recent times to diagnose mastitis effectively. There is an increasing focus on the application of novel therapeutic approaches as an alternative to conventional antibiotic therapy because of the decreasing effectiveness of antibiotics, emergence of antibiotic-resistant bacteria, issue of antibiotic residues in the food chain, food safety issues, and environmental impacts. This article also discussed nanoparticles'/chitosan's roles in antibiotic-resistant strains and ethno-veterinary practices for mastitis treatment in dairy cattle.

Biofilm production by Staphylococcus spp. isolated from bovine mastitis in dairy herds in state of Acre, Brazil and its implications

ABSTRACT This study aimed to identify the Staphylococcus species responsible for bovine mastitis in dairy herds in northern Brazil, to investigate the capacity of biofilm production, and to analyze the association of biofilm production with multiresistance and intensity of California Mastitis Tests (CMT) reactions that can make treatment more difficult and cause misdiagnoses, respectively. Milk samples were collected from 23 dairy farms located in five municipalities in the state of Acre. A total of 339 crossbred cows were tested by CMT, with 109 animals (229 udder ceilings) reacting to the test. After bacterial isolation in blood agar, the catalase-positive and gram-positive cocci were submitted for identification by MALDI-TOF MS. Of 103 strains identified as staphylococci, Staphylococcus chromogenes (58.3%) and Staphylococcus aureus (19.4%) were the most prevalent species. Biofilm production was quantitatively evaluated using a microplate adherence test. Among the Staphylococcus strains, 71.8% were biofilm producers. Most strains of S. chromogenes (68.3%) had the capacity to produce biofilms, ranging from weak (43.3%), moderate (13.3%), and strong (11.7%) producers. Among S. aureus strains, 50% were non-biofilm producers, and none were strong producers. Our data showed an association between biofilm production capacity and multidrug resistance. In addition, there was a reduction in the response to the CMT test, which can mask the diagnosis.

Mammary candidiasis: A medical condition without scientific evidence?

Many physicians, midwives and lactation consultants still believe that yeasts (particularly Candida spp.) play an important role as an agent of nipple and breast pain despite the absolute absence of scientific proofs to establish such association. In this context, the objective of this study was to investigate the microorganisms involved in sore nipples and/or painful "shooting" breastfeeding by using a variety of microscopy techniques, as well as culture-dependent and-independent identification methods. Initially, 60 women (30 diagnosed as suffering "mammary candidiasis" and 30 with no painful breastfeeding) were recruited to elucidate the role of their pumps on the milk microbial profiles. After realizing the bias introduced by using such devices, manual expression was selected as the collection method for the microbiological analysis of milk samples provided by 529 women with symptoms compatible with "mammary candidiasis". Nipple swabs and nipple biopsy samples were also collected from the participating women. Results showed that the role played by yeasts in breast and nipple pain is, if any, marginal. In contrast, our results strongly support that coagulase-negative staphylococci and streptococci (mainly from the mitis and salivarius groups) are the agents responsible for such cases. As a consequence, and following the recommendations of the US Library of Medicine for the nomenclature of infectious diseases, the term "mammary candidiasis" or "nipple thrush" should be avoided when referring to such condition and replaced by "subacute mastitis".

Effects of lactic acid bacteria silage inoculation on methane emission and productivity of Holstein Friesian dairy cattle

Inoculants of lactic acid bacteria (LAB) are used to improve silage quality and prevent spoilage via increased production of lactic acid and other organic acids and a rapid decline in silage pH. The addition of LAB inoculants to silage has been associated with increases in silage digestibility, dry matter intake (DMI), and milk yield. Given the potential change in silage and rumen fermentation conditions accompanying these silage additives, the aim of this study was to investigate the effect of LAB silage inoculants on DMI, digestibility, milk yield, milk composition, and methane (CH4) production from dairy cows in vivo. Eight mid-lactation Holstein-Friesian dairy cows were grouped into 2 blocks of 4 cows (multiparous and primiparous) and used in a 4×4 double Latin square design with 21-d periods. Methane emissions were measured by indirect calorimetry. Treatments were grass silage (mainly ryegrass) with no inoculant (GS), with a long-term inoculant (applied at harvest; GS+L), with a short-term inoculant (applied 16h before feeding; GS+S), or with both long and short-term inoculants (GS+L+S). All diets consisted of grass silage and concentrate (75:25 on a dry matter basis). The long-term inoculant consisted of a 10:20:70 mixture of Lactobacillus plantarum, Lactococcus lactis, and Lactobacillus buchneri, and the short-term inoculant was a preparation of Lc. lactis. Dry matter intake was not affected by long-term or short-term silage inoculation, nor was dietary neutral detergent fiber or fat digestibility, or N or energy balance. Milk composition (except milk urea) and fat and protein-corrected milk yield were not affected by long- or short-term silage inoculation, nor was milk microbial count. However, milk yield tended to be greater with long-term silage inoculation. Methane expressed in units of grams per day, grams per kilogram of DMI, grams per kilogram of milk, or grams per kilogram of fat and protein-corrected milk yield was not affected by long- or short-term silage inoculation. However, CH4 expressed in units of kilojoules per kilogram of metabolic body weight per day tended to be greater with long-term silage inoculation. Results of this study indicate minimal responses in animal performance to both long- and short-term inoculation of grass silage with LAB. Strain and dose differences as well as different basal silages and ensiling conditions are likely responsible for the lack of significant effects observed here, although positive effects have been observed in other studies.

Probiotics for human lactational mastitis

The use of culture-dependent and -independent techniques to study the human milk microbiota and microbiome has revealed a complex ecosystem with a much greater diversity than previously anticipated. The potential role of the milk microbiome appears to have implications not only for short- and long-term infant health but also for mammary health. In fact, mammary disbiosis, which may be triggered by a variety of host, microbial and medical factors, often leads to acute, subacute or subclinical mastitis, a condition that represents the first medical cause for undesired weaning. Multiresistance to antibiotics, together with formation of biofilms and mechanisms for evasion of the host immune response, is a common feature among the bacterial agents involved. This explains why this condition uses to be elusive to antibiotic therapy and why the development of new strategies for mastitis management based on probiotics is particularly appealing. In fact, selected lactobacilli strains isolated from breast milk have already shown a high efficacy for treatment.

Invited review: effect, persistence, and virulence of coagulase-negative Staphylococcus species associated with ruminant udder health

The aim of this review is to assess the effect of coagulase-negative staphylococci (CNS) species on udder health and milk yield in ruminants, and to evaluate the capacity of CNS to cause persistent intramammary infections (IMI). Furthermore, the literature on factors suspected of playing a role in the pathogenicity of IMI-associated CNS, such as biofilm formation and the presence of various putative virulence genes, is discussed. The focus is on the 5 CNS species that have been most frequently identified as causing bovine IMI using reliable molecular identification methods (Staphylococcus chromogenes, Staphylococcus simulans, Staphylococcus haemolyticus, Staphylococcus xylosus, and Staphylococcus epidermidis). Although the effect on somatic cell count and milk production is accepted to be generally limited or nonexistent for CNS as a group, indications are that the typical effects differ between CNS species and perhaps even strains. It has also become clear that many CNS species can cause persistent IMI, contrary to what has long been believed. However, this trait appears to be quite complicated, being partly strain dependent and partly dependent on the host's immunity. Consistent definitions of persistence and more uniform methods for testing this phenomenon will benefit future research. The factors explaining the anticipated differences in pathogenic behavior appear to be more difficult to evaluate. Biofilm formation and the presence of various staphylococcal virulence factors do not seem to (directly) influence the effect of CNS on IMI but the available information is indirect or insufficient to draw consistent conclusions. Future studies on the effect, persistence, and virulence of the different CNS species associated with IMI would benefit from using larger and perhaps even shared strain collections and from adjusting study designs to a common framework, as the large variation currently existing therein is a major problem. Also within-species variation should be investigated.

Association of coagulase-negative staphylococcal species, mammary quarter milk somatic cell count, and persistence of intramammary infection in dairy cattle

This study was conducted to evaluate the association between subclinical intramammary infection (IMI) with coagulase-negative staphylococci (CNS), mammary quarter milk somatic cell count (SCC), and persistence of IMI in dairy cattle. Convenience samples of CNS isolates harvested from milk samples of subclinically infected mammary quarters collected between 4 and 2wk before drying-off, between 2wk before drying-off and the day of drying-off, within 24h after calving, between 1 and 2wk after calving, and during lactation were evaluated. Isolates were obtained from the Canadian Bovine Mastitis Research Network culture bank and were identified to the species level using rpoB gene sequencing. Cow and quarter-level data were obtained from the Canadian Bovine Mastitis Research Network database and used for statistical analyses. In addition, for mammary quarters that had more than one isolation of the same CNS species at different time points, the isolates were evaluated using pulsed-field gel electrophoresis to identify persistent IMI. Milk SCC was compared between mammary quarters infected with different CNS species and to a cohort of uninfected mammary quarters. A total of 877 isolates from 643 mammary quarters of 555 cows on 89 Canadian dairy farms were identified to the species level. Twenty different species were identified, with Staphylococcus chromogenes being the most common species identified (48% of isolates), followed by Staphylococcus simulans (19%) and Staphylococcus xylosus (10%). Of the 20 species identified, only 9 species were found in persistently infected quarters. Milk SCC was significantly higher in the CNS-infected mammary quarters than in the uninfected control quarters for 8 of the 20 species studied. Also, mean SCC differed significantly between mammary quarters infected with different CNS species. Within a given species, a high degree of variability was noted in milk SCC. These data corroborate recent data from Europe with regard to the predominance of certain species of CNS (e.g., Staph. chromogenes). In addition, some species of CNS appear to have a greater effect on milk SCC. Finally, some CNS species are associated with persistent IMI suggesting that some species (e.g., Staph. chromogenes and Staph. simulans) are better host-adapted, whereas others may have an environmental reservoir.

Virulence factors and ability of staphylococci from bovine milk and the cowshed environment to biofilm formation

The aim of this study was to examine virulence factors and the ability of S. aureus and CNS species isolated from milk of cows with mastitis to form biofilm, and to compare them with virulence factors of staphylococci from milk of cows without mastitis and cowshed environment. Most of S. aureus strains from cows with mastitis showed haemolytic activity (93.9%), among them 72.7% and 21.2% produced alpha- and beta-haemolysin, respectively. S. aureus from cows with mastitis symptoms produced proteases (above 48%) and esterase (42.4%). The highly significant relationship between the number of S. xylosus strains producing haemolysins (62%) and the origin of these strains from milk of cows with mastitis was observed. The ability to produce proteases was significantly associated with S. sciuri from milk of cows with mastitis. The ability of biofilm formation by staphylococcal strains from milk of cows with mastitis was greater than in strains from milk of cows without mastitis and the difference was significant (p < or = 0.05). The highest percentage of strains from milk of cows with mastitis were weak biofilm formers (48.6%), while 40% and 11.4% of strains were moderate and strong biofilm producers, respectively. S. xylosus showed the highest ability to form biofilm, while the lowest ability to form biofilm was observed in S. aureus and S. epidermidis. In conclusion, production of exotoxins and enzymes, and ability of biofilm formation shown by many CNS isolated from milk of cows with mastitis symptoms indicates that these features are important in pathogenesis of this disease.

The human milk microbiota: origin and potential roles in health and disease

Human milk has been traditionally considered sterile; however, recent studies have shown that it represents a continuous supply of commensal, mutualistic and/or potentially probiotic bacteria to the infant gut. Culture-dependent and -independent techniques have revealed the dominance of staphylococci, streptococci, lactic acid bacteria and bifidobacteria in this biological fluid, and their role on the colonization of the infant gut. These bacteria could protect the infant against infections and contribute to the maturation of the immune system, among other functions. Different studies suggest that some bacteria present in the maternal gut could reach the mammary gland during late pregnancy and lactation through a mechanism involving gut monocytes. Thus, modulation of maternal gut microbiota during pregnancy and lactation could have a direct effect on infant health. On the other hand, mammary dysbiosis may lead to mastitis, a condition that represents the first medical cause for undesired weaning. Selected strains isolated from breast milk can be good candidates for use as probiotics. In this review, their potential uses for the treatment of mastitis and to inhibit mother-to-infant transfer of HIV are discussed.

Some coagulase-negative Staphylococcus species affect udder health more than others

A longitudinal study in 3 dairy herds was conducted to profile the distribution of coagulase-negative Staphylococcus (CNS) species causing bovine intramammary infection (IMI) using molecular identification and to gain more insight in the pathogenic potential of CNS as a group and of the most prevalent species causing IMI. Monthly milk samples from 25 cows in each herd as well as samples from clinical mastitis were collected over a 13-mo period. Coagulase-negative staphylococci were identified to the species level using transfer-RNA intergenic spacer PCR. The distribution of CNS causing IMI was highly herd-dependent, but overall, Staphylococcus chromogenes, Staphylococcus xylosus, Staphylococcus cohnii, and Staphylococcus simulans were the most prevalent. No CNS species were found to cause clinical mastitis. The effect of the most prevalent species on the quarter milk somatic cell count (SCC) was analyzed using a linear mixed model, showing that Staph. chromogenes, Staph. simulans, and Staph. xylosus induced an increase in the SCC that is comparable with that of Staphylococcus aureus. Almost all CNS species were able to cause persistent IMI, with Staph. chromogenes causing the most persistent infections. In conclusion, accurate species identification cannot be ignored when studying the effect of CNS on udder health, as the effect on SCC differs between species and species distribution is herd-specific. Staphylococcus chromogenes, Staph. simulans, and Staph. xylosus seem to be the more important species and deserve special attention in further studies. Reasons for herd dependency and possible cow- and quarter-level risk factors should be examined in detail for the different species, eventually leading to cost-benefit analyses for management changes and, if needed, treatment recommendations.

Staphylococcus epidermidis strains isolated from breast milk of women suffering infectious mastitis: potential virulence traits and resistance to antibiotics

Background

Although Staphylococcus aureus is considered the main etiological agent of infectious mastitis, recent studies have suggested that coagulase-negative staphylococci (CNS) may also play an important role in such infections. The aims of this work were to isolate staphylococci from milk of women with lactational mastitis, to select and characterize the CNS isolates, and to compare such properties with those displayed by CNS strains isolated from milk of healthy women.

Results

The milk of 30 women was collected and bacterial growth was noted in 27 of them, of which Staphylococcus epidermidis was isolated from 26 patients and S. aureus from 8. Among the 270 staphylococcal isolates recovered from milk of women with mastitis, 200 were identified as Staphylococcus epidermidis by phenotypic assays, species-specific PCR and PCR sequencing. They were typified by pulsed field gel electrophoresis (PFGE) genotyping. The PFGE profiles of the S. epidermidis strains were compared with those of 105 isolates from milk of healthy women. A representative of the 76 different PFGE profiles was selected to study the incidence of virulence factors and antibiotic resistance. The number of strains that contained the biofilm-related icaD gene and that showed resistance to oxacillin, erythromycin, clindamycin and mupirocin was significantly higher among the strains isolated from mastitic milk.

Conclusion

S. epidermidis may be a frequent but largely underrated cause of infectious mastitis in lactating women. The resistance to diverse antibiotics and a higher ability to form biofilms found among the strains isolated from milk of women suffering mastitis may explain the chronic and/or recurrent nature of this infectious condition.

Effect of bovine lactoferrin on the internalization of coagulase-negative staphylococci into bovine mammary epithelial cells under in-vitro conditions

Coagulase-negative staphylococci (CNS) have emerged as bovine mastitis pathogens in many countries. CNS mastitis is generally mild but can persist in the udder for long periods. Pathogenesis of CNS intramammary infection is not well understood. In the present study, adhesion, invasion and intracellular replication of twenty-two CNS strains isolated from bovine mastitis and the effect of bovine lactoferrin (bLf) on the internalization were studied in vitro in a bovine mammary epithelial (BME) cell model. The CNS strains were of Staphylococcus chromogenes, Staph. simulans, Staph. epidermidis, Staph. haemolyticus and Staph. cohnii urealyticus; two strains of Staph. aureus were used as controls. Seven of the CNS strains originated from persistent and five from transient mastitis infections. The in-vitro susceptibility of the strains to bLf was also investigated. All CNS species examined had an adhesive ability equal to that of Staph. aureus, but internalization varied among staphylococcal strains. The antagonistic effect of bLf on the adhesion and invasion of CNS strains was weak, but bLf significantly decreased intracellular replication and replication rates of CNS. No correlation between the in-vitro susceptibility of the strain to bLf or internalization among clinical signs of mastitis was established. No difference between the persistent and transient CNS strains in adhesion, invasion or replication rate was recorded. This in-vitro BME cell model can be used to study the virulence potential of mastitis pathogens, although the severity and persistence of eventual infections shall be further investigated in vivo. The role of bLf in intramammary infection caused by CNS may be limited.

The bacteriocin nisin, an effective agent for the treatment of staphylococcal mastitis during lactation

Eight women with clinical signs of staphylococcal mastitis were randomly divided in 2 groups. A solution of the bacteriocin nisin (6 microg/mL) was applied to the nipple and mammary areola of those assigned to the nisin group for 2 weeks, and a similar preparation devoid of nisin was applied to the control group. On day 0, staphylococcal counts in breast milk of the nisin and control groups were similar (5.04+/-0.19 and 4.88+/-0.21 log10 CFU/mL, respectively). However, on day 14, the mean in the nisin group (3.22+/-0.43 log10 CFU/mL) was statistically lower than that of the control group (5.01+/-0.21 log10 CFU/mL). No clinical signs of mastitis were observed among the women of the nisin group on day 14, whereas they persisted throughout the study in the women of the control group. In conclusion, nisin seems to be an efficient alternative to antibiotics for the treatment of staphylococcal mastitis.

Oral administration of Lactobacillus strains isolated from breast milk as an alternative for the treatment of infectious mastitis during lactation

In this study, 20 women with staphylococcal mastitis were randomly divided in two groups. Those in the probiotic group daily ingested 10 log(10) CFU of Lactobacillus salivarius CECT5713 and the same quantity of Lactobacillus gasseri CECT5714 for 4 weeks, while those in the control one only ingested the excipient. Both lactobacillus strains were originally isolated from breast milk. On day 0, the mean staphylococcal counts in the probiotic and control groups were similar (4.74 and 4.81 log(10) CFU/ml, respectively), but lactobacilli could not be detected. On day 30, the mean staphylococcal count in the probiotic group (2.96 log(10) CFU/ml) was lower than that of the control group (4.79 log(10) CFU/ml). L. salivarius CECT5713 and L. gasseri CECT5714 were isolated from the milk samples of 6 of the 10 women of the probiotic group. At day 14, no clinical signs of mastitis were observed in the women assigned to the probiotic group, but mastitis persisted throughout the study period in the control group women. In conclusion, L. salivarius CECT5713 and L. gasseri CECT5714 appear to be an efficient alternative for the treatment of lactational infectious mastitis during lactation.

PCR-DGGE assessment of the bacterial diversity of breast milk in women with lactational infectious mastitis

Background

Infectious mastitis is a common condition during lactation and in fact, represents one of the main causes leading to a precocious weaning. The number of studies dealing with lactational mastitis is low and, up to now, the etiological diagnosis is frequently made on the basis of unspecific clinical signs. The aim of this study was to investigate the microbial diversity of breast milk in 20 women with lactational mastitis employing culture-dependent and culture-independent (PCR-DGGE) approaches.

Methods

Breast milk samples were cultured in different media to investigate the presence of bacteria and/or yeasts, and a total of 149 representative isolates were identified to the species level by 16S rRNA gene PCR sequencing. The microorganisms recovered were compared with those found by PCR-DGGE analysis. To identify the DGGE profiles two reference markers of different microbial species were constructed. Sequence analysis of unknown bands was also performed.

Results

Staphylococci were the dominant bacterial group and Staphylococcus epidermidis was the dominant species. In a lower number of samples, other bacteria (mainly streptococci and a few gram-negative species) were also identified. Globally, PCR-DGGE results showed a good correlation with those obtained by culture-based methods. However, although DNA bands corresponding to different lactic acid bacteria were detected, such bacteria could not be isolated from the milk samples.

Conclusion

Staphylococci seem to be the main etiological agents of human lactational mastitis. The combined use of culture and molecular techniques allowed a better characterization of the bacterial diversity in milk from women suffering from infectious mastitis. Our results suggest that this condition could be the result of a disbiotic process where some of the bacterial species usually present in human milk outgrow (staphylococci) while others disappear (lactobacilli or lactococci).

Bovine mastitis and its association with selected risk factors in smallholder dairy farms in and around Bahir Dar, Ethiopia

Three hundred fifty one (195 local zebu and 156 Holstein x local zebu crosses) lactating cows of smallholder farms in Bahir Dar 'milk shed' were examined from September 2003 to March 2004 to determine mastitis prevalence, isolate pathogens and identify the role of some potential risk factors. Clinical prevalence was determined through examination of abnormalities of milk, udder or cow. California mastitis test (CMT) was used for determination of subclinical mastitis prevalence. Clinical prevalence at cow level was 3.9% in crossbreds and none in local zebu breeds. Subclinical mastitis at cow level based on CMT was high (34.4%) in crossbreds compared to indigenous zebu (17.9%) (p < 0.05). Quarter subclinical prevalence based on CMT was 17.9% and 4.9% in crossbreds and local zebu, respectively. The pathogens isolated from mastitic milk (CMT positive milk) were coagulase negative staphylococci (CNS), S. aureus, Str. agalactiae, Str. dysgalactiae, Str. uberis, Micrococcus species, C. bovis, A. pyogens, B. cereus, and S. intermedius. Among these, the most frequent isolates were CNS (50%), S. aureus (19%), Str. agalactiae (8%) and Str. dysgalactiae (7%). Among potential risk factors considered, stage of lactation, parity and breed were found to affect the occurrence of mastitis significantly (p < 0.05).

Bovine Intramammary Infections Caused by Coagulase-Negative Staphylococci May Persist Throughout Lactation According to Amplified Fragment Length Polymorphism-Based Analysis

Persistence of coagulase-negative staphylococci (CNS) in intramammary infections during lactation was studied in a research dairy herd of University of Helsinki. Milk samples from 328 udder quarters of 82 dairy cows (30 primiparous, 52 multiparous) were collected 2 wk before calving, at calving, and every 4 wk thereafter until the end of lactation or until the cow left the herd. The CNS isolated from the milk samples were analyzed with the API Staph ID 32 (bioMérieux, Marcy l'Etoile, France) test (API) and genotyped using amplified fragment length polymorphism (AFLP) analysis. The AFLP patterns were used for similarity analysis between CNS isolates and for species identification. For the latter, AFLP patterns of CNS isolates and staphylococcal type strains were used as operational taxonomic units in numerical analysis. In addition, the somatic cell count (SCC) of the milk samples was measured during lactation. A CNS infection was considered persistent when isolates originating from the same quarter had identical AFLP patterns on at least 3 consecutive samplings. In total, 63 CNS infections were detected during lactation in 30 and 33 quarters in the first and later lactations, respectively. Twenty-nine of these infections persisted and 34 were transient. Most of the persistent infections lasted until the end of lactation. In 57 quarters, CNS infection was detected before calving, at calving, or both, but only half of these quarters were infected by CNS during subsequent lactation. The geometric mean of SCC in quarters during persistent CNS infection was 657,600 cells/mL, and the mean of SCC in quarters with transient CNS infection was 619,100 cells/mL. The median of SCC in quarters during persistent CNS infection was 355,400 cells/mL, and the median of SCC in quarters with transient CNS infection was 133,500 cells/mL. According to both the API test and AFLP results, Staphylococcus chromogenes and Staphylococcus simulans were the CNS species isolated most often. Identification results for API and AFLP corresponded in 71.9% of the isolates.

Predictors of development of anastomotic femoral pseudoaneurysms after aortobifemoral reconstruction for abdominal aortic aneurysm

BACKGROUND

The pathogenesis of anastomotic femoral pseudoaneurysms (AFPs) is still unclear. We have performed this long-term retrospective study of patients who underwent aortobifemoral reconstruction for abdominal aortic aneurysm (AAA) in order to better establish the long-term rate of AFP and to identify the predictors of its late occurrence.

METHODS

The long-term outcome of 178 patients who underwent and survived aortobifemoral reconstruction for infrarenal AAA was reviewed.

RESULTS

During a median follow-up of 5.2 years, 28 AFPs developed in 19 patients. Six AFPs were recurrent. The mean linearized rate of AFPs was 1.88% per year. At 15 years, the survival-freedom rate from AFPs was 60%, and from repair of AFPs it was 62%. The survival-freedom rate from AFP was significantly poorer in patients with chronic obstructive pulmonary disease (P = 0.017; at 10 years: 64.3% versus 92.3%), hyperlipidemia (P = 0.0056; at 10 years: 59.2% versus 87.5%), current smoking (P <0.0001; at 10 years: 65.8% versus 94.5%), and postoperative inguinal wound infection (P <0.0001; at 10 years: 42.8% versus 86.8%). Multivariate analysis showed that chronic obstructive pulmonary disease (relative risk [RR]: 3.05, 95% confidence interval [CI]: 1.04 to 8.95), current smoking (RR: 5.38, 95% CI: 1.62 to 17.90), and postoperative inguinal wound infection (RR: 9.04, 95% CI: 2.76 to 29.96) were significantly associated with the development of AFPs. The linearized rate of AFPs was significantly higher only among current smokers (P <0.0001, 4.4% versus 0.8% per year) and among those who had inguinal wound infection (P = 0.001, 9.2% versus 1.5% per year).

CONCLUSIONS

Current smoking and inguinal wound infection may contribute to the development of AFP after aortobifemoral reconstruction for AAA, likely by affecting reparative connective tissue mechanisms at the anastomotic site.

Concentrations and specific antibodies to staphylococcal enterotoxin-C and toxic shock syndrome toxin-1 in bovine mammary gland secretions, and inflammatory response to the intramammary inoculation of these toxins

To investigate the pathological role of staphylococcal enterotoxins (SEs) and toxic shock syndrome toxin-1 (TSST-1) in bovine mastitis, the production of SEs and TSST-1 was investigated in staphylococci isolated from 120 mammary gland secretions (MGS, 51 from no clinical sign-mammary glands and 69 from staphylococcal mastitic-mammary glands) collected from dairy farms where staphylococcal mastitis frequently occurred in Miyagi and Yamagata prefectures from 1997 to 1998. Concentrations of these toxins and specific antibody titers in each MGS were also measured. Furthermore, SEC and TSST-1 were inoculated into lactating mammary glands and inflammatory responses were analyzed. A high percentage of staphylococci including Staphylococcus aureus and coagulase-negative staphylococci isolated from both no clinical sign- and mastitic-MGS produced both SEC and/or TSST-1. The concentration of SEC increased with the severity of the mastitis, and was significantly higher (P<0.05) in acute mastitic-than in no clinical signs-MGS. Titers of specific antibodies to TSST-1 in MGS were significantly higher (P<0.05) than those to SEC, regardless of whether or not the cows were lactating or mastitic. Specific antibodies purified from MGS neutralized each toxin in vitro. A significant increase (P < 0.05) in somatic cell counts was induced by the intramammary inoculation of SEC but not TSST-1. These findings indicated that SEC rather than TSST-1 plays an important role in the pathology of staphylococcal bovine mastitis. The inflammatory activity of TSST-1 was probably neutralized by specific antibodies in MGS.

Possible virulence factors of Staphylococcus sciuri

Staphylococcus sciuri is an opportunistic pathogen of controversial clinical significance. The factors that contribute to colonization and/or infection caused by this bacterium have not been studied intensively so far. The present research was carried out in order to study the presence of potential virulence factors in 121 human and animal isolates of this bacterium. Isolates were examined for biofilm formation, hemagglutination, presence of clumping factor, production of spreading factors and exotoxins, cytotoxicity and capacity to stimulate nitric oxide production. The results showed that S. sciuri is highly capable of biofilm production, that it displays strong proteolytic and DNase activities, produces hemolysins and stimulates nitric oxide production by rat macrophages. Although the present study showed existence of a wide spectrum of possible virulence determinants of S. sciuri, their exact contribution to virulence of this bacterium in vivo remains to be determined.