Subclinical Mastitis and Antimicrobial Susceptibility of Staphylococcus caprae and Staphylococcus epidermidis Isolated from Two Italian Goat Herds

Upregulation of ica Operon Governs Biofilm Formation by a Coagulase-Negative Staphylococcus caprae

Staphylococcus caprae is a Gram-positive, coagulase-negative staphylococci (CoNS), which appears as commensal in the skin, as well as a prevalent mastitis pathogen of goats. Occasionally, it is also associated with infections in humans. Biofilm formation has been identified as a putative virulence factor in S. caprae. Biofilms are multicellular communities protected by a self-produced extracellular matrix (ECM), which facilitates the resistance of bacterial cells to antimicrobial treatments. The ECM is constructed by exopolysaccharides, including the major exopolysaccharide-polysaccharide intercellular adhesion (PIA), regulated by the ica operon in Staphylococcus species. The aim of this study was to characterize the expression of the ica operon in relation to biofilm formation in S. caprae. Results showed that within a few hours of growth, S. caprae could adhere to polystyrene surfaces, start to accumulate, and form biofilm. Peak biofilm biomass and maturation were reached after 48 h, followed by a reduction in biomass after 72 h. Confocal laser scanning microscopy showed the expression of matrix-associated proteins and polysaccharides at various time points. The expression dynamics of the ica operon were investigated using real-time reverse transcriptase PCR (RT)-qPCR, which showed elevated expression during the early stages of biofilm formation and subsequent downregulation throughout the biofilm aging process. In conclusion, our results show that the ica operon is essential in regulating biofilm formation in S. caprae, similar to other Staphylococcus species. Furthermore, the robustness of the observed biofilm phenotype could account for the successful intramammary colonization and may explain disease persistence caused by this pathogenic bacterium.

Antimicrobial and Methicillin Resistance Pattern of Potential Mastitis-Inducing Staphylococcus aureus and Coagulase-Negative Staphylococci Isolates from the Mammary Secretion of Dairy Goats

Staphylococcus spp. is an important mastitis-inducing zoonotic pathogen in goats and is associated with antimicrobial resistance (AMR). The objectives of this study were to determine the prevalence and composition of staphylococci in individual mammary secretion (MS) samples of clinically healthy goats and to evaluate the phenotypic AMR pattern and the presence of methicillin resistance in the Staphylococcus spp. strains. Staphylococcus spp. isolates (n = 101) from the MS samples (n = 220) were identified to species level using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The antimicrobial susceptibility testing included a disk diffusion assay and the determination of the minimum inhibitory concentrations (MIC) of resistant strains (n = 46). Presumptive methicillin-resistant strains (n = 9) were assessed for the presence of mecA, mecC and SCCmec/orfx genes. Staphylococcus spp. isolates were recovered from 45.9% of the MS samples, of which, 72.3% was identified as coagulase-negative staphylococci (CoNS), with the remaining being Staphylococcus aureus. CoNS and S. aureus were most commonly resistant to ampicillin (56.2% and 57.1%, respectively), penicillin (26.0% and 39.3%, respectively), amoxicillin (26 % and 25 %, respectively) and cephalexin (12.3% and 25%, respectively) in the disk diffusion method. CoNS exhibited a broader AMR pattern and a higher percentage of resistant strains than S. aureus in the disk diffusion and MIC methods. Of the nine oxacillin- and cefoxitin-resistant strains, three S. aureus and five CoNS strains carried the mecA gene and, thus, were identified as methicillin-resistant. The mecC gene was not found in any of the studied strains. The presence of AMR and methicillin resistance in caprine S. aureus and CoNS poses a concern for animal and public health.

Multilocus sequence analysis reveals genetic diversity in Staphylococcus aureus isolate of goat with mastitis persistent after treatment with enrofloxacin

Staphylococcus aureus is one of the main bacterial agents responsible for cases of mastitis in ruminants, playing an important role in the persistence and chronicity of diseases treated with antimicrobials. Using the multilocus sequence typing technique, network approaches and study of the population diversity of microorganisms, we performed analyzes of S. aureus (ES-GPM) isolated from goats with persistent mastitis (GPM). The most strains of ES-GPM were categorically different phylogenetically from the others and could be divided into two lineages: one with a majority belonging to ES-GPM and the other to varied strains. These two lineages were separated by 27 nuclear polymorphisms. The 43 strains comprised 22 clonal complexes (CCs), of which the ES-GPM strains were present in CC133, CC5 and a new complex formed by the sequence type 4966. The genetic diversity of some alleles showed be greater diversity and polymorphism than others, such as of the aroE and yqiL genes less than glpF gene. In addition, the sequences ES-GPM to the arc gene and glpF alleles showed the greatest number of mutations for ES-GPM in relation to non-ES-GPM. Therefore, this study identified genetic polymorphisms characteristic of S. aureus isolated from milk of goats diagnosed with persistent mastitis after the failed treatment with the antibiotic enrofloxacin. This study may help in the future to identify and discriminate this agent in cases of mastitis, and with that, the most appropriate antibiotic treatment can be performed in advance of the appearance of persistent mastitis caused by the agent, reducing the chances of premature culling and animal suffering.

Epidemiology and antibiogram of common mastitis-causing bacteria in Beetal goats

Background and Aim:

Mastitis has been identified as the most prevalent and economically imperative disease among dairy animals. Thus, understanding its common bacterial pathogens and risk factors is necessary to improve udder health at herd, region, or country level. However, scientific research on caprine mastitis, especially on Beetal breed, has remained to be insufficient in Pakistan. Therefore, this study aimed to evaluate the epidemiology and antibiogram assay of common mastitis-causing bacterial agents, that is, Staphylococcus, Streptococcus, and Escherichia coli, in dairy goats.

Materials and Methods:

In total, 500 Beetal goats, irrespective of age and those that were not treated with any kind of antimicrobial agents during the past 120 h, were screened using California Mastitis Test in Pattoki, Kasur District, whereas epidemiological factors were recorded. The milk samples of mastitic goats were then collected and processed using standard methods. Each sample was primarily cultured on nutrient agar. Using a specific medium, each bacterial colony was separated using several streak methods. Six antibiotic disks belonging to different antibiotic groups were used for antibiogram profiling of bacterial isolates. Chi-square test was used to assess the association of baseline characteristics and mastitis occurrence. Meanwhile, multivariable logistic regression (p<0.001) was utilized to determine the risk factors associated with positive and negative dichotomous outcome of mastitis.

Results:

The results revealed that the overall prevalence of goat mastitis was 309 (61.8%), in which 260 (52%) and 49 (9.8%) cases were positive for subclinical mastitis (SCM) and clinical mastitis (CM), respectively. Streptococcus and E. coli were found to be the predominant isolates causing SCM and CM, respectively (p<0.001). It was observed that amoxicillin+clavulanic acid was highly sensitive to isolates of Staphylococcus and Streptococcus and ceftiofur sodium to isolates of Streptococcus and E. coli., while enrofloxacin was found to be sensitive to isolates of Streptococcus and E. coli. Risk factors such as herd structure, deworming, vaccination, presence of ticks, use of teat dip and mineral supplements, feeding type, age, parity, housing, blood in the milk, milk leakage, milk taste, and milk yield were found to have the strongest association with mastitis occurrence, while ease of milking has moderate association.

Conclusion:

In the area examined, cases of SCM were found to be higher compared with that of CM, and ceftiofur sodium has been identified as the preferred treatment in both clinical and subclinical forms of caprine mastitis in Beetal goats. Risk factors for mastitis that was identified in this study can form the basis for the creation of an udder health control program specific for dairy goats. We hope our findings could raise awareness of the risk factors and treatment approaches for common mastitis-causing bacterial agents.

A rare lumbar pyogenic spondylodiscitis caused by staphylococcus caprae with initial misdiagnosis: case report and literature review

Background

Staphylococcus caprae (Sc) is an uncommon causative organism for human. Lumbar pyogenic spondylodiscitis (LPS) of Sc is extremely rare and only a few cases have been reported. As far as we know, there is no specific literature on the diagnosis and treatment for LPS of Sc with L5 nerve root irritation.

Case presentation

A 65-year-old male patient complained of chronic low back pain for 10 years, acute worsening with radiating pain to left lower extremity over a month. Physical examination revealed tenderness point on his low back, 3/5 dorsiflexor strength in his left 1st toe and decreased sensation of pin prick over the left lateral shank and medial dorsal foot. The individual was initially misdiagnosed with lumbar disc herniation (LDH) without further examination in outpatient, which was then found to be LPS of Sc with L5 nerve root irritation after admission to our hospital. Magnetic resonance images (MRI) of lumbar spine exhibited inflammation signal at L4-L5 level of the vertebral body and disc with hypointense on T1-weighted images (T1-WI) and hyperintense on T2-weighted images (T2-WI). The causative organism was confirmed by the culture of irrigation fluid obtained from L5 vertebrae by needle puncture. After systemic conservative treatment including using sensitive antimicrobial agents and immobilization, the rare infection was finally cured. The patient also showed a satisfactory recovery during the 36-month follow-up period.

Conclusions

Confirming the diagnosis and identifying the causative organism as soon as possible is the key point for the treatment of LPS. LPS of Sc causing nerve root irritation is rare but curable with early diagnosis and proper therapy. The culture of irrigation fluid obtained from vertebrae by needle puncture may be an effective and sensitive attempt for potential infection of spine to identify the causative organism at early stage of the disease.

Coagulase-positive methicillin-resistant Staphylococcus aureus circulating in clinical mastitic goats in Bangladesh

BACKGROUND AND AIM

Staphylococcus aureus is argued as one of the principal organisms responsible for mammary gland infection in lactating goats, causing both clinical and subclinical mastitis. Being highly zoonotic potential, pathogen emergence of methicillin-resistant S. aureus (MRSA) has a significant clinical impact on treatment and management of clinical mastitis. We conducted a cross-sectional study to investigate the prevalence of coagulase-positive S. aureus (CoPS), antimicrobial resistance profile of Staphylococcus spp., prevalence of MRSA, and association between different clinical parameters with CoPS.

MATERIALS AND METHODS

A total of 67 clinical mastitic goats were sampled based on clinical examination and California mastitis test. Standard bacteriological methods were performed to isolate and identify Staphylococcus spp. CoPS were confirmed by nuc gene using polymerase chain reaction (PCR). All staphylococcal isolates were further examined for antimicrobial susceptibility testing by disk diffusion method. MRSA was confirmed based on mecA gene-based PCR.

RESULTS

Here, 49 (73.13%; 95% confidence interval [CI], 61.41-82.35) samples were positive for Staphylococcus spp., of which 17 (34.69%; 95% CI, 22.88-48.73) isolates were CoPS and rest of the isolates (32; 65.30%; 95% CI, 51.27-77.12) were identified as coagulase-negative Staphylococcus spp. (coagulase-negative staphylococci [CNS]). Both, CoPS and CNS isolates displayed the highest resistance against tetracycline (76.47% and 75%, respectively) and oxacillin (70.58% and 68.75%, respectively). Notably, all staphylococcal isolates were multidrug-resistant (showed resistance to ≥3 classes of antimicrobials). mecA gene was found in 6 (8.96%; 95% CI, 3.84-18.52) CoPS isolates indicating MRSA strains. Among different clinical parameters, presence of high body temperature (p<0.05), firm udder consistency (p<0.01), bloodstained milk (p<0.00), and pus in milk (p<0.00) were significantly associated with the presence of CoPS in mastitic caprine milk.

CONCLUSION

To the best of our knowledge, this is the first report of MRSA isolated from clinical caprine mastitis cases in Bangladesh. The findings of this study would help in cautious selection as well as administration of antimicrobials for therapeutic management of mastitic goats.

Study on prevalence and bacterial etiology of mastitis, and effects of subclinical mastitis and stage of lactation on SCC in dairy goats in Egypt

In Egypt, inadequate information on prevalence and epidemiology of caprine mastitis is available. This study was designed to investigate prevalence and etiological agents of caprine mastitis and assess the efficacy of somatic cell count (SCC) as marker of subclinical mastitis (SCM) in dairy goats. This study was carried out on 249 randomly selected lactating goats in different lactation stages and examined clinically. Of these animals, 477 milk samples were aseptically collected and screened for bacterial carriage. SCC was assessed in 234 apparently normal milk samples, and SCC ≥ 10⁶ cells/ml was indicator for SCM. Prevalence of clinical mastitis (CM) was 33.73% and 16.87% at animal and udder-half levels, respectively. SCM was 52.56% in the apparently healthy halves. Culture results proved single infection in 49.69% of samples, mixed infection in 23.9% of samples, and 26.41% of samples were negative. Coagulase negative staphylococci (CNS) were the most predominant bacteria (58.75%), then Staphylococcus aureus (S. aureus) (24.375%), and Streptococci (1.875%) were the least. No significant difference was recorded between mean of SCC in bacteriologically positive and negative samples, neither in those with SCC ≤ 10⁶ nor with SCC ≥ 10⁶ cells/ml both in middle and late lactation stages. Besides, the percentage of animals harboring SCC ≥ 10⁶ cells/ml and negative for bacteriology in late lactation stage was 3 times (28.57%) more than in midlactation (9.3%). We can assume that SCC is not proper indicator for intra-mammary inflammation (IMI) in goats, and bacteriological examination remains more efficient, despites being time consuming and expensive.

Skin Microbiome Differences in Atopic Dermatitis and Healthy Controls in Egyptian Children and Adults, and Association with Serum Immunoglobulin E

Atopic dermatitis (AD) is a complex, multifactorial, chronic pruritic inflammatory skin disease. We report the first microbiome study and new insights on the relationship between skin microbiota variation and AD susceptibility in a population sample from Egypt. We characterized the skin microbiome in 75 patients with AD and 20 healthy controls using Illumina MiSeq sequencing of 16S rRNA gene. Overall, bacterial diversity of skin microbiome in patients with AD was less than those of the healthy subjects. Genus level analysis revealed significant abundance variations by age, disease severity, locality, or immune response. Among these genera, Streptococcus, Cutibacterium, and Corynebacterium appeared to be specific signatures for AD in children, adolescents, and adults, respectively, while Staphylococcus was noted as a potential biomarker candidate for AD. Additionally, functional potential of metagenomes shifted the overall metabolic pathways to participate in the exacerbation of disease. Total immunoglobulin E (IgE) levels were positively correlated with relative enrichment of certain Staphylococcus aureus subspecies. Finally, AD-related differences in skin bacterial diversity appeared to be in part linked to the serum IgE level. These new observations attest to the promise of microbiome science and metagenomic analysis in AD specifically, and clinical dermatology broadly.

Underrated Staphylococcus species and their role in antimicrobial resistance spreading

The increasing threat of antimicrobial resistance has shed light on the interconnection between humans, animals, the environment, and their roles in the exchange and spreading of resistance genes. In this review, we present evidences that show that Staphylococcus species, usually referred to as harmless or opportunistic pathogens, represent a threat to human and animal health for acting as reservoirs of antimicrobial resistance genes. The capacity of genetic exchange between isolates of different sources and species of the Staphylococcus genus is discussed with emphasis on mobile genetic elements, the contribution of biofilm formation, and evidences obtained either experimentally or through genome analyses. We also discuss the involvement of CRISPR-Cas systems in the limitation of horizontal gene transfer and its suitability as a molecular clock to describe the history of genetic exchange between staphylococci.

Association between species-specific staphylococcal intramammary infections and milk somatic cell score over time in dairy goats

Numerous factors affect milk somatic cell score (SCS) in dairy goats including physiologic factors such as stage of lactation, and pathological factors such as bacterial intramammary infection (IMI), e.g. staphylococcal IMI. The association between IMI and udder inflammation and especially differences in the inflammatory response between the different staphylococcal species are yet to be identified. The objectives of this study were to use data from a recently published longitudinal study that characterized IMI status over time to evaluate the species-specific effect of staphylococcal IMI on udder half-level milk SCS, and to evaluate the effect of time since IMI diagnosis on this relationship. Half-level milk samples for culture and determination of SCS were collected from 171 goats starting within 10 days in milk (DIM), and then at various intervals until ≥ 120 DIM. A mixed linear model was used to assess the effect of species-specific staphylococcal IMI on SCS, accounting for confounding by lentivirus infection, parity, DIM, and the contralateral half IMI status, and for repeated measurements within udder half and for clustering of halves within goat. A second model was used to evaluate the effect of time since first IMI diagnosis and its interaction with staphylococcal IMI status on the relationship between staphylococcal IMI status and SCS. Lentivirus seropositivity and contralateral half IMI status were associated with SCS. Staphylococcal IMI status was associated with SCS, with differences between species. Staphyloccocus caprae, Staphylococcus epidermidis, Staphylococcus simulans, and Staphylococcus xylosus were associated with higher SCS than a number of other species. Time since first diagnosis did not modify the relationship between IMI status and SCS.

Effects of indirect indicators of udder health on nutrient recovery and cheese yield traits in goat milk

In dairy goats, very little is known about the effect of the 2 most important indirect indicators of udder health [somatic cell count (SCC) and total bacterial count (TBC)] on milk composition and cheese yield, and no information is available regarding the effects of lactose levels, pH, and NaCl content on the recovery of nutrients in the curd, cheese yield traits, and daily cheese yields. Because large differences exist among dairy species, conclusions from the most studied species (i.e., bovine) cannot be drawn for all types of dairy-producing animals. The aims of this study were to quantify, using milk samples from 560 dairy goats, the contemporary effects of a pool of udder health indirect indicators (lactose level, pH, SCC, TBC, and NaCl content) on the recovery of nutrients in the curd (%REC), cheese yield (%CY), and daily cheese yields (dCY). Cheese-making traits were analyzed using a mixed model, with parity, days in milk (DIM), lactose level, pH, SCC, TBC, and NaCl content as fixed effects, and farm, breed, glass tube, and animal as random effects. Results indicated that high levels of milk lactose were associated with reduced total solids recovery in the curd and lower cheese yields, because of the lower milk fat and protein contents in samples rich in lactose. Higher pH correlated with higher recovery of nutrients in the curd and higher cheese yield traits. These results may be explained by the positive correlation between pH and milk fat, protein, and casein in goat milk. High SCC were associated with higher recovery of solids and energy in the curd but lower recovery of protein. The higher cheese yield obtained from milk with high SCC was due to both increased recovery of lactose in the curd and water retention. Bacterial count proved to be the least important factor affecting cheese-making traits, but it decreased daily cheese yields, suggesting that, even if below the legal limits, TBC should be considered in order to monitor flock management and avoid economic losses. The effect of NaCl content on milk composition was linked with lower recovery of all nutrients in the curd during cheese-making. In addition, high milk NaCl content led to reductions in fresh cheese yield and cheese solids. The indirect indicators of the present study significantly affected the cheese-making process. Such information should be considered, to adjust the milk-to-cheese economic value and the milk payment system.

Antimicrobial Resistance and Distribution of Staphylococcus spp. Pulsotypes Isolated from Goat and Sheep Bulk Tank Milk in Southern Spain

Bulk tank milk from 58 dairy goat and sheep flocks located in southern Spain was examined to determine the prevalence and distribution of Staphylococci. A total of 45 isolates were obtained and characterized to determine the species, antimicrobial resistance profile, and genetic similitude by pulse-field gel electrophoresis (PFGE) using SmaI. Staphylococcus aureus isolates were confirmed by polymerase chain reaction (PCR) analysis of nuc, and resistance to methicillin was determined by PCR analysis of mecA. A total of 10 different staphylococcal species were identified, 22.2% and 77.8% of which were coagulase positive and negative, respectively. Twenty-two (48.89%) isolates were resistant to at least one antimicrobial agent. Higher antimicrobial resistance values were obtained against tetracycline (28.9%) and penicillin (22.2%). Two isolates (S. aureus and Staphylococcus lentus) were resistant to cefoxitin; however, none of the 45 isolates harbored mecA. Thirty pulsotypes were detected by PFGE. Interestingly, some isolates of S. aureus, S. lentus, Staphylococcus simulans, and Staphylococcus caprae showed high genetic similarity (>80%). These data suggest that genetically similar staphylococcal isolates circulate among goat and sheep dairy herds, and their different resistance patterns could be influenced by the management systems used.

Persistence of coagulase negative staphylococcal intramammary infections in dairy goats

The objectives of the research described here were to describe the persistence of intramammary infections (IMI) caused by coagulase negative staphylococci (CNS) in goats using strain-typing, and to evaluate the relationship between species-specific CNS IMI and somatic cell score (SCS) at the udder-half level. Udder-half milk samples were collected from all 909 lactating goats (1817 halves; 1 blind half) in a single herd. Milk samples were cultured on Columbia blood agar, and 220 goats with at least one half yielding a single colony type CNS were enrolled for two additional half-level samplings at approximately 1-month intervals. Isolates were identified to the species level by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry or PCR amplification and partial sequencing of tuf or rpoB. An IMI was defined as persistent when ≥1 follow-up sample yielded the same species and strain as on Day 0 based on pulsed-field gel electrophoresis. A generalised mixed linear model was used to evaluate the odds of persistence as a function of CNS species. A mixed linear model was used to evaluate the relationship between IMI status on a given day and SCS. Among 192 IMI, 69.8% were persistent based on species and strain-type. Staphylococcus simulans IMI had higher odds of persistence than Staphylococcus arlettae IMI. In primiparous goats, Staphylococcus epidermidis IMI was associated with higher SCS than S. arlettae, Staphylococcus xylosus and 'other CNS' IMI. The differences detected in the present study between CNS species, with regard to persistence of IMI and association with SCS, highlight the need to study CNS at the species and strain level to understand the pathogenicity and epidemiology of CNS in goats.

Staphylococcal intramammary infection dynamics and the relationship with milk quality parameters in dairy goats over the dry period

The objectives of this study were (1) to report the rates of new intramammary infection (IMI) and spontaneous IMI cure over the dry period in 3 dairy goat herds; (2) to evaluate the factors predicting infection dynamics over the dry period; and (3) to define milk quality parameter thresholds that predict infection dynamics over the dry period. Two consecutive udder-half milk samples were collected 10 to 14 d apart before dry-off from 288 goats in 3 herds, and 2 consecutive udder-half samples were collected 7 to 14 d apart in the following lactation, with the first sample being collected ≤10 d in milk, from 200 of the same goats. In 2 of the herds, udder-half milk samples were also collected at the same time points (n = 312 halves; 157 goats) for measurement of milk quality parameters. Standard aerobic culture of milk samples was performed for the detection of mastitis pathogens. To rule out the presence of Mycoplasma spp. IMI, milk samples were also cultured on modified Hayflick medium. Non-Mycoplasma isolates were speciated using MALDI-TOF mass spectrometry. Staphylococcal isolates, when not identified by MALDI-TOF, were speciated using partial gene sequence analysis of rpoB or tuf. When >1 sample from an udder half yielded the same species, available isolates from the first and last positive samples for that species were strain-typed using pulsed-field gel electrophoresis. Incidence of new IMI and cure rate were computed. Generalized linear mixed regression models were built to evaluate the associations between new IMI and pre-dry somatic cell score (SCS), between IMI persistence and half-level SCS, and between IMI persistence and pre-dry IMI species. Thresholds for pre-dry SCS and lactose concentration were computed to predict IMI persistence. Overall, 12.6% (48/380) of halves had a persistent IMI. Cumulative incidence of new IMI over the dry period was 13.2%, and cure rate was 52.0%. Pre-dry SCS was not associated with odds of new IMI or IMI persistence. Pre-dry IMI species was not associated with odds of persistence. Lactose concentration was not associated with odds of persistence. Regardless of culture data, the optimal pre-dry SCS threshold to detect IMI that would persist into the next lactation was 8.7, with sensitivity and specificity of 50 and 73.8%, respectively. Further studies on the effect of control measures on species-specific incidence and cure rates during the dry period are warranted.

Use of MALDI-TOF to characterize staphylococcal intramammary infections in dairy goats

The most common pathogens causing intramammary infections (IMI) in dairy goats are staphylococci. Gene sequencing has been the reference method for identification of staphylococcal species, but MALDI-TOF mass spectrometry could represent a rapid and cost-effective alternative method. The objectives were to evaluate the typeability and accuracy of partial gene sequencing and MALDI-TOF for identifying staphylococci isolated from caprine milk samples, and to evaluate the relationship between staphylococcal species IMI, milk somatic cell score (SCS), and milk yield (MY). A composite (goat-level) milk sample was collected from all 940 lactating goats in a single herd. Dairy Herd Information Association test-day data for parity, days in milk, SCS, and MY were retrieved from Dairy Herd Information Association records. Milk samples were cultured on Columbia blood agar, and isolates from samples that yielded a single colony type of a presumptively identified Staphylococcus spp. were identified by PCR amplification and partial sequencing of rpoB, tuf, or 16S-rRNA, and MALDI-TOF. Mixed linear models were used to evaluate the relationship between staphylococcal IMI, SCS, and MY. The goat-level prevalence of staphylococcal IMI based on isolation of a single colony type was 24.4% (213/874). Seventeen goats had a contaminated sample. Among the remaining goats (n = 857), the most common species causing single colony-type IMI were Staphylococcus simulans (7.9%), Staphylococcus xylosus (3.5%), Staphylococcus caprae (3.6%), Staphylococcus chromogenes (2.9%), and Staphylococcus epidermidis (2.2%). The typeability of staphylococcal isolates with partial housekeeping gene sequence analysis (rpoB, complemented by tuf and 16S as needed) was 97.7%. The typeability and accuracy of MALDI-TOF were 84 and 100%, respectively. Overall, only Staphylococcus chromogenes IMI was associated with a higher SCS than goats with no growth. After adjusting for parity and stage of lactation, staphylococcal IMI status was not significantly associated with MY. For the staphylococci isolated from goats in this herd, MALDI-TOF proved an accurate method of speciation with a relatively high typeability. An association between staphylococcal IMI, SCS, and MY was not defined using goat-level data with the exception of S. chromogenes IMI, which was associated with a higher SCS than goats with no growth.

Bacterial Diversity in Feline Conjunctiva Based on 16S rRNA Gene Sequence Analysis: A Pilot Study

Changes in the microbial populations in the conjunctival sacs of animals have traditionally been evaluated using conventional microbiology techniques. The goal of this study was to examine the suitability of a methodology which may reveal a previously unknown microbiome inhabiting feline conjunctival membranes. In the present study, we determined the microbial diversity in feline conjunctivas based on 16S rRNA gene sequence analysis. Five taxa not described earlier in veterinary ophthalmology (i.e., Staphylococcus caprae, Staphylococcus succinus, Propionibacterium acnes, Psychrobacter faecalis, and Bacillus subtilis) were identified in feline conjunctivas with a high similarity (99-100%). The study demonstrates that the feline conjunctival sacs are inhabited by much more rich and diverse microbial communities than previously thought using culture-based methods. From the clinical perspective, this could suggest that other laboratory procedures (e.g., extended incubation time in the case of Actinobacteria, formerly order Actinomycetales) or a new tool like culture-independent approaches (next-generation DNA sequencing) should be taken into account.

Impact of intramammary tilmicosin infusion as a dry cow therapy

Three hundred subclinically infected quarters of 259 Holstein cows infected with gram-positive bacteria were selected via quota sampling based on the California Mastitis Test (CMT) result and were divided randomly and equally into treatment and test groups. Quarters of test group (n = 150 in 128 cows) were treated with an intramammary infusion of tilmicosin, and quarters of the control group (n = 150 in 131 cows) were treated with cloxacillin as a traditional intramammary infusion of dry cow (DC) ointment. Cows with more than one infected quarter were randomly assigned to the same group, and adjacent quarters were treated the same. The milk samples of all quarters were obtained, and bacterial cultures and somatic cell count (SCC) were tested before dry cow therapy (DCT) (50 ± 15 days before parturition), and finally on day 2 of the next lactation. Results have shown that total bacteriological cure rates on day 2 of the next lactation were 45% and 78%, (p = .01), new infection rates were 43.3% and 56.6%, and SCC was (6.732 × 10⁵  ± 3.124 × 10⁵ ) and (5.025 × 10⁵  ± 2.935 × 10⁵ ), (p > .05) in test and control groups, respectively. Tilmicosin had less effect on reducing IMI due to Corynebacterium bovis, and had no effect on Streptococcus agalactiae, but had a potent effect against Staphylococcus aureus. It was concluded that tilmicosin alone should not be infused as an alternative to conventional dry cow therapy. However, it had a significant effect against S. aureus, and the potential of tilmicosin to treat S. aureus IMI should be confirmed in further studies.

Microbiological analysis and sensitivity profile of Staphylococcus spp. in subclinical mastitis of dairy goats

Subclinical mastitis in goats causes economic losses and risks to public health. Given the need for research that shows the most isolated staphylococci species and sensibility tests comparing the resistance between coagulase-negative (CNS) and positive Staphylococcus (CPS) goats with subclinical mastitis, the aim of this study was to identify the microorganisms isolated from milk samples of goats with subclinical mastitis, as well as define the staphylococci species and determine the sensitivity profile of Staphylococcus spp. to antimicrobials. To collect samples, tests were performed for mug of black background and California mastitis test (CMT), collecting milk from CMT positive animals. A total of 226 samples from seven herds of dairy goats was collected and forwarded to the laboratory, where they were seeded for the isolation of the microorganism and implementing the antibiotic sensibility test. Of these, 122 samples had bacterial growth and the most isolated staphylococci species were: S. epidermidis (24.55%), S. lugdunensis (15.40%) and S. intermedius (13.64%). Samples showed increased resistance to antimicrobials: penicillin (81.8%), oxacillin (60.0%) and ampicillin (55.5%). Greater sensitivity to: enrofloxacin (99.1%), erythromycin (98.2%), gentamicin (98.2%) and vancomycin (98.2%) were observed. The S. epidermidis showed higher antimicrobial resistance to amoxicillin and penicillin than S. lugdunensis and S. intermedius. Similar resistance in vitro between CNS and CPS was observed to most antimicrobials. It is important to control the overuse of antibiotics to prevent the emergence of resistant strains.

Characterization of Staphylococcus caprae Clinical Isolates Involved in Human Bone and Joint Infections, Compared with Goat Mastitis Isolates

Staphylococcus caprae is an emerging microorganism in human bone and joint infections (BJI). The aim of this study is to describe the features of S. caprae isolates involved in BJI (H for human) compared with those of isolates recovered in goat mastitis (A for animal). Fourteen isolates of each origin were included. Identifications were performed using a Vitek 2 GP ID card, tuf gene sequencing, and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) Vitek MS. Molecular typing was carried out using pulsed-field gel electrophoresis (PFGE) and DiversiLab technology. The crystal violet method was used to determine biofilm-forming ability. Virulence factors were searched by PCR. Vitek MS technology provides an accurate identification for the two types of isolates compared to that of gold-standard sequencing (sensitivity, 96.4%), whereas the Vitek 2 GP ID card was more effective for H isolates. Molecular typing methods revealed two distinct lineages corresponding to the origin despite few overlaps: H and A. In our experimental conditions, no significant difference was observed in biofilm production ability between H and A isolates. Nine isolates (5 H isolates and 4 A isolates) behaved as weak producers while one A isolate was a strong producer. Concerning virulence factors, the autolysin atlC and the serine aspartate adhesin (sdrZ) genes were detected in 24 isolates (86%), whereas the lipase gene was always detected, except in one H isolate (96%). The ica operon was present in 23 isolates (82%). Fibrinogen-binding (fbe) or collagen-binding (cna) genes were not detected by using primers designed for Staphylococcus aureus or Staphylococcus epidermidis, even in low stringency conditions. Although S. caprae probably remains underestimated in human infections, further studies are needed to better understand the evolution and the adaptation of this species to its host.

Virulence factors genes of Staphylococcus spp. isolated from caprine subclinical mastitis

The aim of this study was to investigate genes involved in adhesion expression, biofilm formation, and enterotoxin production in isolates of Staphylococcus spp. from goats with subclinical mastitis and associate these results with the staphylococcal species. One hundred and twenty-four isolates were identified and polymerase chain reaction (PCR) was performed to detect the following genes: cna, ebpS, eno, fib, fnbA, fnbB, bap, sea, seb, sec, sed and see. The most commonly Staphylococcus species included S. epidermidis, S. lugdunensis, S. chromogenes, S. capitis ss capitis and S. intermedius. With the exception of fnbB, the genes were detected in different frequencies of occurrence in 86.3% of the Staphylococcus spp. isolates. Eno (73.2%) and bap (94.8%) were more frequently detected in coagulase-negative staphylococci (CNS); ebpS (76%), fib (90.9%) and fnbA (87%) were the most frequent genes in coagulase-positive staphylococci (CPS). Regarding enterotoxins, genes sed (28.2%) and see (24.2%) had a higher frequency of occurrence; sec gene was more frequently detected in CPS (58.8%). There was no association between the presence of the genes and the Staphylococcus species. Different virulence factors genes can be detected in caprine subclinical mastitis caused by CNS and CPS. The knowledge of the occurrence of these virulence factors is important for the development of effective control and prevention measures of subclinical mastitis caused by CNS and CPS in goats.

Dynamics of bacterial communities during the ripening process of different Croatian cheese types derived from raw ewe's milk cheeses

Microbial communities play an important role in cheese ripening and determine the flavor and taste of different cheese types to a large extent. However, under adverse conditions human pathogens may colonize cheese samples during ripening and may thus cause severe outbreaks of diarrhoea and other diseases. Therefore in the present study we investigated the bacterial community structure of three raw ewe's milk cheese types, which are produced without the application of starter cultures during ripening from two production sites based on fingerprinting in combination with next generation sequencing of 16S rRNA gene amplicons. Overall a surprisingly high diversity was found in the analyzed samples and overall up to 213 OTU97 could be assigned. 20 of the major OTUs were present in all samples and include mostly lactic acid bacteria (LAB), mainly Lactococcus, and Enterococcus species. Abundance and diversity of these genera differed to a large extent between the 3 investigated cheese types and in response to the ripening process. Also a large number of non LAB genera could be identified based on phylogenetic alignments including mainly Enterobacteriaceae and Staphylococcacae. Some species belonging to these two families could be clearly assigned to species which are known as potential human pathogens like Staphylococcus saprophyticus or Salmonella spp. However, during cheese ripening their abundance was reduced. The bacterial genera, namely Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, Brevibacterium, Corynebacterium, Clostridium, Staphylococcus, Thermoanerobacterium, E. coli, Hafnia, Pseudomonas, Janthinobacterium, Petrotoga, Kosmotoga, Megasphaera, Macrococcus, Mannheimia, Aerococcus, Vagococcus, Weissella and Pediococcus were identified at a relative low level and only in selected samples. Overall the microbial composition of the used milk and the management of the production units determined the bacterial community composition for all cheese types to a large extend, also at the late time points of cheese ripening.

Differences between coagulase-negative Staphylococcus species in persistence and in effect on somatic cell count and milk yield in dairy goats

Coagulase-negative staphylococci (CNS) are the most commonly isolated bacteria from goat milk. The goal of this study was to explore and describe differences between CNS species in persistence of intramammary infection (IMI) and in effect on somatic cell count (SCC) and milk yield (MY). Milk samples were collected from 530 does from 5 Dutch dairy goat herds on 3 occasions during 1 lactation. Coagulase-negative staphylococci species were identified at the species level by transfer RNA-intergenic spacer PCR (tDNA-PCR) followed by capillary electrophoresis. The most prevalent CNS species were Staphylococcus caprae, Staphylococcus epidermidis, Staphylococcus simulans, and Staphylococcus xylosus, but large differences were seen in species distribution between herds. Staphylococcus caprae and Staph. xylosus appeared to be more persistent than other species, but confidence intervals were overlapping. The effect of IMI caused by the 4 most prevalent CNS species on SCC and on MY was determined with linear regression models, and Staph. aureus and Corynebacterium bovis were included in the analyses as reference organisms. Most species were associated with a significantly higher SCC than noninfected udder halves, but the effect of CNS species on SCC was much smaller than the effect of Staph. aureus on SCC. We found a significant positive association between infection with Staph. caprae and MY. Intramammary infection caused by Staph. xylosus, on the other hand, had a negative association with milk yield, comparable to the effect of Staph. aureus, but these effects were not significantly different from zero. Intramammary infections with CNS species have a high prevalence in goats and are persistent, but have a limited effect on SCC compared with IMI with Staph. aureus. The effect of CNS species on MY differed between species, but differences were nonsignificant because limited numbers per species were available for analysis. Therefore, CNS species appear to behave as minor pathogens in goats, but larger studies are needed to give better estimates for the effect on MY.

Short communication: Identification of coagulase-negative staphylococcus species from goat milk with the API Staph identification test and with transfer RNA-intergenic spacer PCR combined with capillary electrophoresis

Coagulase-negative staphylococci (CNS) are the most commonly isolated bacteria from goat milk, but they have often been identified with phenotypic methods, which may have resulted in misclassification. The aims of this paper were to assess the amount of misclassification of a phenotypic test for identifying CNS species from goat milk compared with transfer RNA intergenic spacer PCR (tDNA-PCR) followed by capillary electrophoresis, and to apply the tDNA-PCR technique on different capillary electrophoresis equipment. Milk samples were collected from 416 does in 5 Californian dairy goat herds on 3 occasions during lactation. In total, 219 CNS isolates were identified at the species level with tDNA-PCR and subjected to the API 20 Staph identification test kit (API Staph; bioMérieux, Durham, NC). If the same species was isolated multiple times from the same udder gland, only the first isolate was used for further analyses, resulting in 115 unique CNS isolates. According to the tDNA-PCR test, the most prevalent CNS species were Staphylococcus epidermidis, Staphylococcus caprae, and Staphylococcus simulans. Typeability with API staph was low (72%). Although the API Staph test was capable of identifying the majority of Staph. epidermidis and Staph. caprae isolates, sensitivity for identification of Staph. simulans was low. The true positive fraction was high for the 3 most prevalent species. It was concluded that the overall performance of API Staph in differentiating CNS species from goat milk was moderate to low, mainly because of the low typeability, and that genotypic methods such as tDNA-PCR are preferred.

Mastitis therapy and antimicrobial susceptibility: a multispecies review with a focus on antibiotic treatment of mastitis in dairy cattle

Mastitis occurs in numerous species. Antimicrobial agents are used for treatment of infectious mastitis in dairy cattle, other livestock, companion animals, and humans. Mastitis is an economically important disease of dairy cattle and most mastitis research has focused on epidemiology and control of bovine mastitis. Antibiotic treatment of clinical and subclinical mastitis in dairy cattle is an established component of mastitis control programs. Research on the treatment of clinical and subclinical mastitis in other dairy species such as sheep and goats has been less frequent, although the general principles of mastitis therapy in small ruminants are similar to those of dairy cattle. Research on treatment of clinical mastitis in humans is limited and as for other species empirical treatment of mastitis appears to be common. While antimicrobial susceptibility testing is recommended to direct treatment decisions in many clinical settings, the use of susceptibility testing for antibiotic selection for mastitis treatments of dairy cattle has been challenged in a number of publications. The principle objective of this review is to summarize the literature evaluating the question, "Does antimicrobial susceptibility predict treatment outcome for intramammary infections caused by common bacterial pathogens?" This review also addresses current issues related to antimicrobial use and treatment decisions for mastitis in dairy cattle. Information on treatment of mastitis in other species, including humans, is included although research appears to be limited. Issues related to study design, gaps in current knowledge and opportunities for future research are identified for bovine mastitis therapy.

Prevalence of septic arthritis after anterior cruciate ligament reconstruction among professional athletes

BACKGROUND

Septic arthritis of the knee after anterior cruciate ligament (ACL) reconstruction is a rare complication. Its prevalence and characteristics have never been reported among professional athletes.

PURPOSE

To report the prevalence and the characteristics of septic arthritis after ACL reconstruction in professional athletes and a general population of patients.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

A retrospective analysis of a consecutive series of 1957 patients who underwent an ACL reconstruction between 2003 and 2008 was performed; 88 patients were professional athletes. The patient demographics, the prevalence of infection, the involved organism, and the method of treatment were reviewed. Three potential risk factors for infection-level of sporting participation, indoor/outdoor sports, and the presence or not of a combined lateral tenodesis-were assessed using univariate and multivariate logistic regression analysis.

RESULTS

The prevalence of septic arthritis was 0.37% in the nonprofessional group and 5.7% in the professional athlete population. Being a professional athlete (odds ratio [OR], 16.0; 95% confidence interval [CI], 3.9-59.8; P = .0001) or having a combined lateral tenodesis (OR, 4.8; 95% CI, 1.04-18.04; P = .02) was found to be significantly correlated with septic arthritis after ACL reconstruction. A significant correlation exists between being a professional athlete and having a combined lateral tenodesis (χ(2) = 16.7; P = 4 × 10(-5)), suggesting a potential confounding role is played by one of these variables. All the cases of infection in the professional athletes occurred in those who participated in outdoor sports, although this was not found to be statistically significant (P = .17).

CONCLUSION

Participation in professional sports and having a combined lateral tenodesis are risk factors for the development of infection after ACL reconstruction. We hypothesize that professional athletes may be part of a specific group of patients at higher risk of infection after ACL reconstruction.

Diagnosis and treatment of subclinical mastitis in early lactation in dairy goats

The objectives of the study were to define the sensitivity and specificity of the California Mastitis Test (CMT) in determining the presence of intramammary infection in postpartum dairy goats and to determine whether antibiotic therapy increased bacteriological cure rate and lowered somatic cell count (SCC) compared with untreated controls. A CMT was performed and milk samples were collected for bacteriology from 211 glands of 106 does between 0 and 10 d after kidding. From a population of 3,239 glands from goats in 4 commercial herds, goats with one or both glands with a CMT score of >1 and from which bacteria were isolated were either assigned to be treated with 3 intramammary infusions at 12-h intervals of 75 mg of sodium ampicillin and 250 mg of sodium cloxacillin (n=57 glands) or left as untreated controls (n=49 glands). Milk samples were collected again 14 ± 3 and 21 ± 3 d later for bacteriology and SCC determination. Composite milk yield, goat SCC, length of lactation, and survival data were collected. A partial budget was constructed to assess the cost effectiveness of treatment. At a cut point of greater than trace, the sensitivity, specificity, and positive and negative predictive values of the CMT were 0.74, 0.74, 0.42, and 0.92, respectively. Treatment increased the bacteriological cure rate compared with no treatment [30/57 (53%) vs. 6/49 (12%)], but there was a pathogen by treatment interaction whereby treatment increased cure proportion in glands infected with minor, but not major, pathogens. Treatment reduced the foremilk gland-level SCC [1,595 (95% CI=1,106-2,300) vs. 3,028 (95% CI=2,091-4,385) geometric mean (× 1,000) cells/mL] but not the SCC at goat level [1,596 (95% CI=1,219-2,090) vs. 1,488 (95% CI=1,132-1,955) geometric mean (× 1,000) cells/mL] compared with no treatment. Milk yield, risk of removal from the herd, and length of lactation were not altered by treatment. Treatment resulted in a loss of NZ$20.39/doe. It was concluded that use of the CMT as a screening test resulted in a higher likelihood of finding a gland that would be infected than selecting a gland at random. Treatment increased bacteriological cure rate and reduced SCC at gland level compared with no treatment. However, at goat level, milk yield, SCC, and survival were not altered, resulting in no economic benefit of treatment.

Perfil microbiológico, celular e fatores de risco associados à mastite subclínica em cabras no semiárido da Paraíba

Foi realizado um estudo da mastite subclínica em nove rebanhos de cabras leiteiras no semiárido paraibano com o objetivo de determinar a ocorrência da infecção, avaliar o perfil microbiológico e celular do leite, testar a sensibilidade dos microorganismos isolados frente a antimicrobianos além de identificar os fatores de risco. Foram utilizadas 131 cabras leiteiras das quais foram colhidas 261 amostras de leite para exame microbiológico e 131 para contagem de células somáticas (CCS). Na ocasião das colheitas foi realizado o California Mastitis Test (CMT) e aplicado um questionário epidemiológico por propriedade. Houve crescimento bacteriano em 30 amostras (11,49%) com 25 (83,33%) dos isolados identificados como Staphylococcus coagulase negativa e cinco (16,66%) Staphylococcus aureus. A média de CCS foi de 1,39x10(6) células/ml. O CMT apresentou baixa sensibilidade (46,7%) e baixa especificidade (60,6%) quando comparado ao exame microbiológico. A gentamicina e a associação da neomicina, bacitracina e tetraciclina foram os antimicrobianos contra os quais os microrganismos isolados apresentaram 100% de sensibilidade. Penicilina e ampicilina foram os de maiores índices de resistência (66,67% e 63,89%, respectivamente). A caprinocultura não ser a atividade principal da propriedade e o não isolamento de animais doentes, foram identificados como fatores de risco para a mastite subclínica caprina nas propriedades estudadas. Programas de controle e profilaxia da mastite devem ser implementados enfocando as medidas de higiene na ordenha e correção dos fatores de risco identificados nesse estudo.

Antibiotic Resistance in Staphylococcus aureus and Coagulase Negative Staphylococci Isolated from Goats with Subclinical Mastitis

Antimicrobial resistance patterns and gene coding for methicillin resistance (mecA) were determined in 25 S. aureus and 75 Coagulase Negative Staphylococci (CNS) strains isolates from half-udder milk samples collected from goats with subclinical mastitis. Fourteen (56.0%) S. aureus and thirty-one (41.3%) CNS isolates were resistant to one or more antimicrobial agents. S. aureus showed the highest resistance rate against kanamycin (28.0%), oxytetracycline (16.0%), and ampicillin (12.0%). The CNS tested were more frequently resistant to ampicillin (36.0%) and kanamycin (6.7%). Multiple antimicrobial resistance was observed in eight isolates, and one Staphylococcus epidermidis was found to be resistant to six antibiotics. The mecA gene was not found in any of the tested isolates. Single resistance against β-lactamics or aminoglicosides is the most common trait observed while multiresistance is less frequent.

[Not Available]

As a coagulase negative Staphylococcus species, S. caprae is not considered as a clinically-significant member, unlike S. epidermidis. In this report, we describe a case of sepsis resulting from S. caprae infection. This relatively young woman was in generally good health and contracted S. caprae most probably during her treatment of an acute pulmonary embolism. The purpose of this report is to raise awareness of this otherwise innocuous staphylococcal species in clinical settings.

Stability of microbial communities in goat milk during a lactation year: Molecular approaches

The microbial communities in milks from one herd were evaluated during 1-year of lactation, using molecular methods to evaluate their stability and the effect of breeding conditions on their composition. The diversity of microbial communities was measured using two approaches: molecular identification by 16S and 18S rDNA sequencing of isolates from counting media (two milks), and direct identification using 16S rDNA from clone libraries (six milks). The stability of these communities was evaluated by counting on selective media and by Single Strand Conformation Polymorphism (SSCP) analysis of variable region V3 of the 16S rRNA gene and variable region V4 of the 18S rRNA gene. One hundred and eighteen milk samples taken throughout the year were analyzed. Wide diversity among bacteria and yeasts in the milk was revealed. In addition to species commonly encountered in milk, such as Lactococcus lactis, Lactococcus garvieae, Enterococcus faecalis, Lactobacillus casei, Leuconostoc mesenteroides, Staphylococcus epidermidis, Staphylococcus simulans, Staphylococcus caprae, Staphylococcus equorum, Micrococcus sp., Kocuria sp., Pantoea agglomerans and Pseudomonas putida, sequences were affiliated to other species only described in cheeses, such as Corynebacterium variabile, Arthrobacter sp., Brachybacterium paraconglomeratum, Clostridium sp. and Rothia sp. Several halophilic species atypical in milk were found, belonging to Jeotgalicoccus psychrophilus, Salinicoccus sp., Dietza maris, Exiguobacterium, Ornithinicoccus sp. and Hahella chejuensis. The yeast community was composed of Debaryomyces hansenii, Kluyveromyces lactis, Trichosporon beigelii, Rhodotorula glutinis, Rhodotorula minuta, Candida pararugosa, Candida intermedia, Candida inconspicua, Cryptococcus curvatus and Cryptococcus magnus. The analyses of microbial counts and microbial SSCP profiles both distinguished four groups of milks corresponding to four periods defined by season and feeding regime. The microbial community was stable within each period. Milks from winter were characterized by Lactococcus and Pseudomonas, those from summer by P. agglomerans and Klebsiella and those from autumn by Chryseobacterium indologenes, Acinetobacter baumanii, Staphylococcus, Corynebacteria and yeasts. However, the composition of the community can vary according to factors other than feeding. This study opens new investigation fields in the field of raw milk microbial ecology.

Characterization of Staphylococcus aureus Isolated from Chronically Infected Dairy Goats

A herd of 88 Alpine goats in Northern Italy was monitored for a complete lactation. Milk samples were taken from each udder half during 8 monthly visits. Goats (n = 28) with > or =2 consecutive positive tests for Staphylococcus aureus in the same udder half were identified as chronically infected, and all of those had > or =4 positive tests of the 8 samples. Goats with no infections in either udder half during any visit were considered healthy (n = 26). Linear mixed models were used to examine the relationship between chronic infection by S. aureus and SCC and production traits. The bacteria isolated from one sample from each infected goat were genotyped on the basis of polymorphism in several genes and evaluated for the presence of genes encoding for enterotoxins. The bacteria isolated from each animal were also subject to a test for beta-lactamase production and to minimum inhibitory concentration tests for 11 antimicrobial agents. As expected, SCC (log2) was significantly higher in infected goats than in healthy goats (7.55 vs. 5.50). Also, mean log SCC from infected udder halves (8.02) was greater than that in uninfected udder halves from the same goats (6.44). No significant differences were observed in milk yield or for fat and protein percentages between infected and healthy goats. No genetic variability was observed among the bacteria isolated, suggesting that all were from the same strain, although isolates did vary in susceptibility to various antimicrobial agents. All S. aureus isolates were negative for the beta-lactamase production test. The most effective drugs when tested in vitro were benzylpenicillin, amoxicillin plus clavulanic acid, cloxacillin, and cephalosporins.