Environmental Streptococci Research Articles

Effect of alley-floor scraping frequency on Escherichia coli, Klebsiella species, environmental Streptococcus species, and coliform counts

ABSTRACT The objective of this study, conducted at the University of Kentucky Cold-stream Dairy, was to determine whether increased alley-floor scraping frequency decreased environmental mastitis-causing pathogen counts. Sixteen Holstein cows were monitored during two 3-wk treatments: removing manure from the alley floors once (1 ×) or twice daily (2 ×) by a skid steer equipped with a tire scraper. Bedding, milk, and teat-end swab samples were collected twice weekly to observe changes in streptococci, Klebsiella spp., coliform, and Escherichia coli counts and SCS. Increasing alley-floor scraping frequency to 2 × decreased all bedding pathogen counts (P = 0.01); teat-end coliform, E. coli, and streptococci counts (P

Some Bacteriological and Immunological Studies on Camel's Milk

The aim of the present study was to investigate the correlation between the isolated bacteria from camel's milk with special milk constituents that have immunogenic and therapeutic importance to human consumers. Milk samples were obtained from 90 she-camels from 3 Egyptian governorates. The result showed that coagulase negative staphylococci (CNS) were the most frequently isolated bacteria either as a single isolate (20%) or as mixed infections (27.8%). Staphylococcus aureus (S. aureus) was isolated either as single (3.33%) and mixed infection (27.8%). E. coli, Yersinia enterocolotica (Y. enterocolotica), Proteus vulgaris and environmental streptococci were also isolated in single and/or mixed forms. Total protein, albumin and globulin levels were not significantly affected by different isolates. Nitric oxide (NO) and lysozyme were significantly stimulated by presence of S. aureus, CNS and E.coli. Insulin level was significantly reduced by S. aureus and CNS. Superoxide dismutase (SOD) was not significantly affected, while glutathione peroxidase (GPx) level was significantly stimulated by S. aureus and CNS contamination. Control camel whey samples without phytohemagglutinin (PHA) had the higher stimulant effect on lymphocytes proliferation as compared with control samples with PHA. Conclusively, the isolated bacteria not only constitute health hazards for consumers but also they made changes in the bioactive ingredients of camel milk that may deteriorate the therapeutic and immunogenic benefits of camel milk. So, there is a great need for strict hygienic measures during the production and handling of camel milk.

Short communication: Genotypic and phenotypic identification of environmental streptococci and association of Lactococcus lactis ssp. lactis with intramammary infections among different dairy farms

Lactococcus species are counted among a large and closely related group of environmental streptococci and streptococci-like bacteria that include bovine mastitis pathogenic Streptococcus, Enterococcus, and Aerococcus species. Phenotypic and biochemical identification methods can be inaccurate and unreliable for species within this group, particularly for Lactococcus spp. As a result, the incidence of Lactococcus spp. on the farm may have been historically underreported and consequently little is known about the clinical importance of this genus as a mastitis pathogen. We used molecular genetic identification methods to accurately differentiate 60 environmental streptococci and streptococci-like bacteria isolated from cows with high somatic cell count and chronic intramammary infection (IMI; >2 somatic cell scores above 4) among 5 geographically distinct farms in New York and Minnesota that exhibited an observed increase in IMI. These isolates were phenotypically identified as Streptococcus uberis and Streptococcus spp. Genetic methods identified 42 isolates (70%) as Lactococcus lactis ssp. lactis, including all 10 isolates originally phenotypically identified as Streptococcus uberis. Antibiotic inhibition testing of all Lc. lactis ssp. lactis showed that 7 isolates were resistant to tetracycline. In the present study, a predominance of Lc. lactis ssp. lactis was identified in association with chronic, clinical bovine IMI among all 5 farms and characterized antimicrobial resistance for treatment therapies. Routine use by mastitis testing labs of molecular identification methods for environmental streptococci and streptococci-like bacteria can further define the role and prevalence of Lc. lactis ssp. lactis in association with bovine IMI and may lead to more targeted therapies.

Characterization of clinical mastitis occurring in cows on 50 large dairy herds in Wisconsin

In recent years, the US dairy industry has experienced significant demographic changes, with an increase in the number of large herds. The objectives of the present study were to characterize clinical mastitis occurring in cows on large dairy herds in Wisconsin. Participating herds (n=50) were required to have a minimum of 200 lactating animals, participate in monthly DHI testing (including monthly individual cow somatic cell count), use computerized herd records, use a milking routine that included fore-stripping quarters for detection of mastitis, and use antimicrobials to treat affected cows. After study personnel visited the farm, each herd was instructed to enroll the next 17 cows that experienced clinical mastitis, regardless of severity. At detection of clinical mastitis and 14 to 21d after treatment ended, duplicate quarter milk samples were collected from all affected quarters and used for microbiological analysis. Treatments of affected cows were performed according to existing individual farm protocols. Cow level follow-up data was collected for 90d after enrollment. Microbiological diagnoses at enrollment included gram-negative (35.6%), no growth (27.3%), gram-positive (27.5%), and other (9.6%). Of the 741 cases, the most prevalent pathogens were Escherichia coli (22.5%), followed by environmental streptococci (12.8%), Klebsiella spp. (6.9%), and coagulase-negative staphylococci (6.1%). Bacteriological cure was 75.0% for cases caused by gram-negative pathogens (n=136), 50.8% for cases caused by gram-positive pathogens (n=128), 47.5% for cases caused by other pathogens (n=40), and 73.2% for cases which did not result in microbial growth (n=123). Of the 583 cases with severity recorded, the distribution of mild, moderate, and severe symptoms was 47.8, 36.9, and 15.3%, respectively. The majority of cases presenting with severe symptoms were caused by gram-negative pathogens. Treatment cure was greater for gram-negative pathogens and cases for which no pathogens were recovered as compared with cases caused by other etiologies. Cows experiencing severe cases were more likely to receive multiple antimicrobial treatments.

Antibiotic treatments for bovine mastitis

Mastitis is the most common disease of dairy cattle, and control of this disease is responsible for the majority of antimicrobials administered to adult dairy cows. Mastitis is detected subsequent to initiation of the immune response based on recognition of inflammation. Thus, most cases present with mild or moderate symptoms, and many cases are culture-negative. Most mastitis is treated by milking technicians without diagnosis of the etiology or review of the medical history of the cow. Obtaining a microbiological diagnosis is essential because some cases may spontaneously cure or respond to short-duration therapy, some cases may require longerduration therapy, some cases are culture-negative, and some cases are caused by pathogens for which there are no effective approved antimicrobials. Practitioners have an opportunity to reduce antimicrobial usage and improve mastitis treatment protocols by targeting treatments based on etiology and cow characteristics. Veterinarians should monitor selected outcomes after treatment and design treatment protocols based on etiological agents specific to individual cases or farms. Milking personnel should be trained to detect abnormal milk and aseptically collect milk samples, but treatment protocols should be performed by animal health managers based on etiology and review of the animal health history. The ability to achieve bacteriological cure is strongly associated with etiology and history of previous cases occurring in the affected cow. The need for antimicrobial therapy and the duration of treatment depend primarily on characteristics of the agent and the ability of the cow to initiate a strong immune response. Bacteria that have the ability to invade secretory tissue, such as Staphylococcus aureus, many environmental streptococci, and many strains of Klebsiella spp typically respond better to extended-duration therapy. In contrast, pathogens that infect superficial mucosal surfaces, such as coagulase-negative staph, Streptococcus agalactiae, and most strains of Escherichia coli) are typically cured with short-duration therapy. Producers should be trained to review the somatic cell count history of the cow and use that data to direct treatment decisions. Cows with a longer duration of subclinical infection prior to the clinical case are more likely to require antimicrobial therapy. The decision to administer antimicrobials should be based on determination of etiology by use of rapid-culture systems used either on-farm or in veterinary clinics. Many mild and moderate clinical cases that are culture-negative and detected in otherwise healthy cows can be successfully managed using a strategy of watchful waiting. Cows that are chronically affected and have frequent recurrences should not be repeatedly dosed with antimicrobials, but should either be culled or have the affected glands therapeutically dried off.

Evaluation of the API® 20 Strep system for identification of Lactococcus lactis subspecies lactis isolated from bovine milk samples

Environmental streptococci and streptococci-like bacteria, including Lactococcus lactis ssp lactis, account for approximately 40% of clinical mastitis cases in cows. Recently, Lactococcus lactis ssp lactis was associated with intramammary infections on several New York farms. Although Lactococcus lactis ssp lactis has been isolated from the bovine udder, its importance as a mastitis pathogen is unclear because of misidentification by use of traditional bacterial identification techniques. Molecular identification has improved correct identification of bacterial pathogens, but it is expensive for the clinical practitioner. In this study, the sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and kappa (k) of the API 20 Strep system for identification of Lactococcus lactis ssp lactis were assessed by the use of molecular identification results as the standard.

Host adapted intramammary infections in pregnant heifers which were co-housed and reared on fresh milk as calves

BackgroundHeifers can calve down with intramammary infections (IMI) and udder damage. This will have a negative impact on their longevity, future milk yield and financial return. Co-housed pre-weaned calves that are fed fresh milk have the opportunity to suckle each other’s teats and may infect udders of fellow heifer calves with pathogens present in milk. The prevalence of IMI in pregnant heifers in South Africa (SA) which were co-housed and reared on fresh milk as calves, is not known. Quarter secretion samples from both pregnant heifers (n = 2065) and dry cows (n = 5365) were collected for microbiological analysis from eight SA dairy herds. All heifers tested in this study were co-housed pre-weaning and were fed fresh milk as calves.ResultsThe prevalence of coagulase negative staphylococci, Staphylococcus aureus, Streptococcus agalactiae, environmental streptococci, coliforms and samples with no bacterial growth in heifers was 26%, 0.9%, 0.08%, 1.4%, 0.4% and 66%, respectively. The overall prevalence ratio between heifers and cows for Staphylococcus aureus IMI was 0.76 (95% CI: 0.59, 0.98). Four of the individual herds had prevalence ratios of less than one (p < 0.05), one herd had a prevalence ratio of 3.15 (95% CI: 1.52, 6.32), and the remaining 3 herds had a prevalence ratio not significantly different from 1.0. Marginally significant differences were found between Staphylococcus aureus IMI in pregnant heifers compared to cows in their second and later lactations (p = 0.06, p = 0.05, respectively) but no significant differences between heifers and cows in their first lactation.ConclusionsThe presence of Streptococcus agalactiae IMI in heifers came as a surprise, especially as herd infection rates were low. The high prevalence ratio of Staphylococcus aureus between heifers and cows in one herd warrants further investigation due to the potential danger of udder damage in a young cow at the start of her productive life. The IMI in heifers with host adapted pathogens can also act as a source of new IMI for lactating dairy cows.

Increases of antibiotic resistance in excessive use of antibiotics in smallholder dairy farms in northern Thailand.

Antibiotic resistance patterns of bacterial isolates from both quarter teat-tip swabs and their quarter milk samples were evaluated in smallholder dairy farms in northern Thailand with excessive use of antibiotics (HIGH) compared with normal use (NORM). Results from teat-tip swab samples showed that the percentage of Bacillus spp. resistance to overall antibiotics was significantly lower in the NORM group than that of the HIGH group, whereas, the resistance percentage of coagulase-negative staphylococci in the NORM group was higher than that of the HIGH one. The overall mastitis-causing bacteria isolated from milk samples were environmental streptococci (13.8%), coagulase-negative staphylococci (9.9%), Staphylococcus aureus (5.4%), and Corynebacterium bovis (4.5%). Both staphylococci and streptococci had significantly higher percentages of resistance to cloxacillin and oxacillin in the HIGH group when compared to the NORM one. An occurrence of vancomycin-resistant bacteria was also observed in the HIGH group. In conclusion, the smallholder dairy farms with excessive use of antibiotics had a higher probability of antibiotic-resistant pattern than the farms with normal use.

Management and characteristics of recycled manure solids used for bedding in Midwest freestall dairy herds

Interest in using recycled manure solids (RMS) as a bedding material for dairy cows has grown in the US Midwest. Cost of common bedding materials has increased in recent years and availability has decreased. Information regarding the composition of RMS and its use as a bedding material for dairy cows in the Midwest is very limited. The objectives of this study were to characterize RMS as a bedding material, observe bedding management practices, document methods of obtaining RMS, and describe housing facilities. We visited 38 Midwest dairy operations bedding freestalls with RMS to collect data. Methods of obtaining RMS for bedding included separation of anaerobic digested manure, separation of raw manure, and separation of raw manure followed by mechanical drum-composting for 18 to 24h. Average bedding moisture of unused RMS was 72.4% with a pH of 9.16. Unused samples contained (on a dry basis) 1.4% N, 44.9% C, 32.7C:N ratio, 0.44% P, 0.70% K, 76.5% neutral detergent fiber, 9.4% ash, 4.4% nonfiber carbohydrates, and 1.1% fat. Moisture was lowest for drum-composted solids before and after use as freestall bedding. After use in the stalls, digested solids had lower neutral detergent fiber content (70.5%) than drum-composted (75.0%) and separated raw (73.1%) solids. Total N content was greater in digested solids (2.0%) than in separated raw (1.7%) solids. Total bacterial populations in unused bedding were greatest in separated raw manure solids but were similar between digested and drum-composted manure solids. Drum-composted manure solids had no coliform bacteria before use as freestall bedding. After use as bedding, digested manure solids had lower total bacteria counts compared with drum-composted and separated raw manure solids, which had similar counts. Used bedding samples of digested solids contained fewer environmental streptococci than drum-composted and separated raw solids and had reduced Bacillus counts compared with separated raw solids. Coliform counts were similar for all 3 bedding sources. Addition of a mechanical blower post-separation and use of a shelter for storage were associated with reduced fresh-bedding moisture but not associated with bacterial counts. This was the first survey of herds using RMS for bedding in the Midwest. We learned that RMS was being used successfully as a source of bedding for dairy cows. For most farms in the study, somatic cell count was comparable to the average in the region and not excessively high.

Relationship between in vitro antimicrobial sensitivity of bovine subclinical mastitis isolates and treatment outcome in lactating dairy cows

Summary The objective of the present study was to determine whether there was an association between the in vitro antimicrobial sensitivity test results of subclinical mastitis pathogens and bacteriological cure following intramammary treatment using a combination of nafcillin, penicillin, and streptomycin (NPS). Eighty-six intramammary pathogens from 43 cows were examined in this study. Most intramammary infections were due to coagulase-negative staphylococci, coliforms, and environmental streptococci. The antibiotic sensitivity to NPS was determined using the Kirby-Bauer disc diffusion method. Bacteriological cure rates for sensitive, intermediate, and resistant isolates in the standard treatment group (3 intramammary infusions of NPS once daily) were 84.4, 88.9, and 100%, respectively. These figures in the extended treatment group (6 intramammary infusions of NPS once daily) were 100% for the 3 categories. Bacteriological cure was not associated with the sensitivity test result. Based on this study, Kirby-Bauer sensitivity test results were not useful as predictors of the bacteriological outcome of subclinical mastitis treated with intramammary NPS.

Relationship between in vitro susceptibility of bovine subclinical mastitis isolates and bacteriological outcome of intramammary treatment with cefquinome

The objective of the present study was to determine whether there was an association between the in vitro antimicrobial susceptibility test results of subclinical mastitis pathogens and bacteriological outcomes of intramammary treatments using cefquinome. A total of 110 intramammary pathogens from 51 cows were assessed in this study. Most intramammary infections were due to coagulase-negative staphylococci, environmental streptococci, and coliforms. The antimicrobial susceptibility to cefquinome was determined using the Kirby-Bauer disc diffusion method. Bacteriological cure rates for the sensitive, intermediate, and resistant isolates in the standard treatment group (three intramammary infusions of 75 mg cefquinome at 16 h intervals) were 82.4%, 90%, and 87.5%, respectively. These figures in the extended treatment group (six intramammary infusions of 75 mg cefquinome at 16 h intervals) were 83.3%, 100%, and 100%, respectively. Treatment outcomes were not associated with the results of sensitivity tests in the standard group. However, in the extended group, the probability of a bacteriological cure was lower in quarters from which cefquinome-sensitive pathogens were isolated than the quarters from which intermediate or resistant pathogens were isolated. Based on this study, the Kirby-Bauer susceptibility test result is a poor predictor for the bacteriological cure of subclinical mastitis treated with intramammary cefquinome.

Etiologic mastitis agents of high somatic cell count dairy herds in Tennessee

The objective of the study was to determine etiologic agent(s) of intramammary infections (IMI) in high somatic cell count (SCC) dairies in Tennessee. This was a prospective study utilizing 2,444 dairy cows from 20 high SCC dairy herds. Composite milk samples were aseptically collected from lactating cows in 20 dairy herds with a rolling herd average SCC &gt;400,000 cells/mL. Milk samples were cultured and mastitis pathogens identified following procedures recommended by the National Mastitis Council. The average herd percentage (average of the 20 herd averages) of culture-negative cows was 49%. The average herd percentages of positive-culture cows were 28% for coagulase-negative staphylococci (CNS), 15% for Staphylococcus aureus, 10% for environmental streptococci (ES), and ?2% for gram-negative organisms. Among cows with individual SCC &gt;1 million cells/mL, 30% of cultures yielded Staph. aureus, 23% CNS, 26% no growth, 26% ES, and 5% gram-negative organisms. Among cows with individual SCC &gt;400,000 cells/mL, cultures yielded 26% CNS, 30% no growth, 28% Staph. aureus, 21% ES, and 4% gram-negative organisms. Staph. aureus was the most common major pathogen, or equally common major pathogen, in 75% of high SCC herds. Environmental streptococci were the most common major pathogen, or equally common major pathogen, in 45% of high SCC herds. Staph. aureus is the major pathogen, followed by ES, among Tennessee dairy herds with high SCC. Coagulase-negative staphylococci are common, but their significance needs to be determined. Gram-negative organisms do not appear to be significant pathogens of Tennessee dairy herds with persistently high SCC.

Effect of heat treatment of bovine colostrum on bacterial counts, viscosity, and immunoglobulin G concentration

A study was conducted to identify the optimal temperature and time at which heat treatment of bovine colostrum would least change viscosity and IgG concentrations yet reduce bacterial count. First-milking colostrum with >50g of immunoglobulins/L (measured by colostrometer) was collected from 30 Holstein cows. Aliquots of colostrum were heated for 0, 30, 60, or 90min at 57, 60, or 63°C in a water bath. Samples were examined for viscosity, IgG1, and IgG2 concentrations, standard plate count, coagulase-negative staphylococci, environmental streptococci, coliform, gram-negative noncoliform, Streptococcus agalactiae, and Staphylococcus aureus counts. All heat treatments reduced counts of all bacteria groups measured compared with untreated colostrum samples. Heat treatment at ≥60°C denatured IgG1 compared with untreated colostrum; however, colostral IgG2 levels were not reduced when temperature was held at 60°C for <60min. Viscosity was not affected when temperature was held at 60°C for <60min. In this study, heat treatment of bovine colostrum at 60°C for 30 or 60min reduced bacterial count, slightly reduced IgG concentration, and did not affect viscosity.

Infectious aetiologies of mastitis on Korean dairy farms during 2008

The objective of this study was to determine the frequency of different mastitis pathogens in 1255 milk samples collected from 368 lactating cows on 24 dairy farms in Korea during 2008. The proportion of cows and quarter milk samples having SCC200,000 cells/ml, an indicator of udder infection, was 54.3% (200/368 cows) and 35.5% (446/1255 samples), respectively. Of the 446 milk samples subjected to bacteriological examination, 16.5% (74) showed no bacterial growth and 3.5% (16) were contaminated. In total, 356 of 1255 (28.3%) samples were bacteriologically positive, from which 415 bacteria were isolated. The most frequently isolated pathogen was coagulase-negative staphylococci (40.7%), followed by Gram-negative bacteria (19.5%) other than Escherichia coli, Staphylococcus aureus (12.2%), Streptococcus uberis (5.3%), Enterococcus spp. (4.8%), E. coli (4.5%), and environmental streptococci (3.1%) other than S. uberis. This study demonstrates that environmental pathogens were the vast majority of bacteria isolated from mastitic bovine milk samples in Korea.

Environmental mastitis in intensive high‐producing dairy herds in New South Wales

To determine the prevalence of mastitis pathogens in high-producing intensive dairy herds in New South Wales. Field survey. Milk samples from the mastitis-affected quarter were collected from cows on five high-producing dairy farms in NSW. The 820 samples were cultured using standard microbiological culture techniques. Bacteria or fungi were isolated from 83.3% of samples (683/820). More than two colony types were isolated from 16.7% of samples (137/820), two types from 6.6% (54/820), and one type from 52.3% (429/820). No bacteria were isolated from 24.4% (200/820) of the primary cultures, but enrichment cultures of these samples yielded single colony type bacterial isolates from 36.5% (73/200) of samples. Environmental pathogens, including coliforms, environmental Streptococcus and Staphylococcus spp., made up 91% (555/610) of isolates and accounted for 33.6% (205/610), 41.6% (254/610) and 15.7% (96/610), respectively, of isolates. Escherichia coli accounted for 76.1% (156/205) of the coliform isolates, Streptococcus uberis and Streptococcus dysgalactiae accounted for 32.3% (82/254) and 28.0% (71/254), respectively, of the environmental streptococcal isolates. Contagious pathogens were uncommon, comprising only 2.5% (15/610) of the total isolates. The incidence and causes of mastitis are largely influenced by farm management. The relatively high prevalence of coliform mastitis in the intensive high-producing herds in this survey contrasts with the low incidence reported in surveys of pasture-based herds in Victoria. If the Australian dairy industry continues its current trend of intensification, coliform intra-mammary infections may emerge as an increasingly important cause of mastitis.

Effects of Prepartum Intramammary Antibiotic Therapy on Udder Health, Milk Production, and Reproductive Performance in Dairy Heifers

Preparturient heifers (n = 561) from 9 herds in 6 US states and 1 Canadian province were enrolled in a study to test the hypothesis that prepartum intramammary therapy would cure existing intramammary infections (IMI) and lead to increased milk production, reduced linear somatic cell count (LSCC), and improved reproductive performance. Mammary secretions were collected 10 to 21 d before expected calving from each quarter. Heifers were then assigned by identification number to receive intramammary therapy consisting of infusion of one tube per mammary quarter of a lactating cow commercial antibiotic preparation containing cephapirin or to a nontreated control group. Overall, 34.1% of mammary quarters were infected with a mastitis pathogen before parturition and 63.4% of heifers had at least one mammary quarter infected. The coagulase-negative staphylococci (CNS) caused the majority (74.8%) of prepartum IMI. Coagulase-positive staphylococci, environmental streptococci, and coliforms accounted for 24.5% of prepartum infections. Treatment had a significant effect on the cure rate of infected mammary quarters. Mammary quarters that were infected prepartum and treated with antibiotics had a 59.5% efficacy of cure rate and the percentage reduction in heifers with IMI was 51.9. Control quarters had a spontaneous cure rate of 31.7%. Treatment did not significantly affect milk production or LSCC in the first 200 d of lactation; however, there was a significant treatment by herd interaction for milk production. Quarters cured of either CNS or major pathogens had a lower LSCC in the first 200 d of lactation. No significant effect on services per conception or days open between treatment and control groups was observed. This trial demonstrated that prepartum intramammary antibiotic therapy did reduce the number of heifer IMI postpartum. Milk production, LSCC, and reproductive performance during the first 200 d of the first lactation were not significantly affected by treatment. Given these results, use of prepartum intramammary antibiotic therapy in heifers as a universal strategy to increase milk production in first-lactation dairy cows may not be warranted.

Microorganisms associated with sub-Clinical mastitis and their impact on milk production in camels (Camelus Dromedarius) in semi-arid lands of Northern Kenya

Camels are adapted to the arid and semi arid lands (ASAL), but their full milking potential is affected by udder infection especially sub-clinical mastitis. The purpose of this study was to identify the most common pathogens responsible for sub-clinical mastitis in camels kept under ranch conditions in Northern Kenya. A total of 435 camel milk samples were collected over a period of 11 months and examined for mastitis causing microorganisms. Mastitis causing bacteria were isolated from 66.7% of the samples. The most prevalent groups were group D streptococci (30%), coagulase negative staphylococcus (CNS) (20.1%), Staphylococcus aureus (16%), Streptococcus dysgalactiae (3.6%) and Streptococcus agalactiae (1.5%). Other isolates were Coliforms and Micrococci. Streptococcus dysgalactiae and Streptococcus agalactiae had a greater association with sub-clinical mastitis than the other pathogens. Streptococcus agalactiae and Staphylococcus aureus were ranked as infectious pathogens while group D streptococci, Streptococcus dysgalactiae, CNS, Coliforms and Micrococci were ranked as environmental pathogens. The mean milk yield from quarters infected with infectious streptococcal pathogens was 1.58L per milking, which was lower than that from quarters infected with environmental streptococci (2.63L). Sub-clinical mastitis in camels has adverse implications and needs to be addressed in order to maximize camel production in the ASAL. Keywords: camels, sub-clinical mastitis, milk yield, ASAL, microorganismsInternational Journal of Agriculture and Rural Development, Vol. 6 2005: 182-187

Relationship between antimicrobial susceptibility of clinical mastitis pathogens and treatment outcome in cows

To determine whether there was any association between results of in vitro antimicrobial susceptibility testing of pathogens isolated from cows with mild or moderate clinical mastitis and outcome of treatment. Observational study. 133 cows with mild or moderate mastitis in a single quarter. Cows were treated by means of intramammary infusion of pirlimycin (50 mg) in the affected quarter once daily for 2 days; additional intramammary treatments with the same product were administered if the milk continued to appear abnormal. Duration of treatment and days until clinical cure were recorded. Bacterial isolates were tested for antimicrobial susceptibility by means of a broth micro-dilution technique. Environmental streptococci, coliforms, and coagulase-negative Staphylococcus spp were the most commonly isolated pathogens. Duration of treatment and days until clinical cure were not significantly different for cows from which pathogens that were susceptible or resistant to pirlimycin were isolated. Bacteriologic cure rates 14 and 21 days after treatment were not significantly different for cows with mastitis caused by susceptible or resistant bacteria. Similar results were found when data only from cows with mastitis caused by gram-positive isolates were analyzed. In the present study, differences in clinical outcome for cows with mild or moderate mastitis that could be attributed to differences in results of in vitro susceptibility testing were not identified. The use of in vitro susceptibility testing to guide intramammary mastitis treatment cannot be recommended on the basis of results of this study.

Macrolide and lincosamide resistance genes of environmental streptococci from bovine milk

Environmental streptococcus isolates from bovine milk were identified to the species and strain level and screened for resistance to macrolide and lincosamide antibiotics by phenotypic and genotypic methods. Isolates were tested for resistance to erythromycin and pirlimycin by broth microdilution assays. Presence of ribosomal methylase genes (ermA, ermB, ermC) and efflux pump genes (mefA/E, msrA/C) was detected by polymerase chain reaction (PCR). Resistance to pirlimycin (minimum inhibitory concentration (MIC) = 8microg/ml) was detected in 6 of 13 Enterococcus isolates that were identified as E. faecium by API20Strep typing. msrC was detected in 10 enterococcal isolates but the detection of msrC was not associated with phenotypic resistance. msrC negative isolates were reclassified as Enterococcus mundtii based on sequencing of housekeeping genes. Resistance to erythromycin and pirlimycin (MIC > 16microg/ml) was detected in 4 of 4 Streptococcus dysgalactiae and 12 of 20 Streptococcus uberis isolates and was encoded by ermB. All Streptococcus isolates tested negative for ermA, ermC, mefA/E and msrA/C. Among ermB positive streptococci, three alleles were identified based on a 527 bp gene fragment. Each allele was detected in at least two herds. The same alleles have also been detected in other bacterial species from bovine and non-bovine hosts and farm soil, suggesting a theoretical potential for horizontal transfer of macrolide resistance genes on dairy farms.

Assessment of the benefits of Orbeseal®, when used in combination with dry cow antibiotic therapy in three commercial dairy herds

An internal teat sealant containing bismuth subnitrate was used in combination with dry cow antibiotic therapy in a cow-level prospective case-control field trial in three herds with different dry cow management practices. Treated quarters (antibiotic+sealant) had a 59% lower odds of developing a new dry period infection at 1-3 days-in-milk (DIM) than control (antibiotic only) quarters (P&lt;0.001). Herd-level variation in new intramammary infection (IMI) and mastitis treatment rates during the first 100 DIM were observed. Greatest benefits from internal teat sealant use were documented in herds with the highest rates of new IMI during the dry period, and for environmental streptococci. Economic benefit accrued from differences in the timing of treatment for mastitis was estimated to be $5.38 per cow in the herd.