TABLE 6.
Sensitivity and Specificity with 95% lower and upper for various bacterial species and groups indicated in composite samples at somatic cell counts threshold levels of 150 000 cells/mL and 200 000 cells/mL.
| Bacteria isolated | Sensitivity at 150 000 cells/mL threshold (95% LCI and UCI) | Specificity at 150 000 cells/mL threshold (95% LCI and UCI) | Sensitivity at 200 000 cells/mL threshold (95% LCI and UCI) | Specificity at 200 000 cells/mL threshold (95% LCI and UCI) |
|---|---|---|---|---|
| Staphylococcus aureus (STA) | 0.80 (0.78, 0.82) | 0.52 (0.51, 0.53) | 0.74 (0.73, 0.77) | 0.52 (0.52, 0.53) |
| Staphylococcus aureus (STH) | 0.89 (0.86, 0.92) | 0.53 (0.52, 0.53) | 0.86 (0.83, 0.89) | 0.525 (0.52, 0.53) |
| Streptococcus agalactiae | 0.89 (0.87, 0.92) | 0.52 (0.52, 0.53) | 0.86 (0.83, 0.89) | 0.525 (0.52, 0.53) |
| Streptococcus uberis | 0.82 (0.80, 0.84) | 0.52 (0.51, 0.53) | 0.77 (0.75, 0.79) | 0.523 (0.52, 0.53) |
| Streptococcus dysgalactiae | 0.91 (0.87, 0.94) | 0.53 (0.52, 0.53) | 0.87 (0.84, 0.90) | 0.53 (0.52, 0.54) |
| Major Gram-positive Pathogens | 0.84 (0.81, 0.88) | 0.50 (0.49, 0.51) | 0.78 (0.77, 0.83) | 0.50 (0.50, 0.51) |
| Major Gram-negative pathogensa | 0.96 (0.90, 1.03) | 0.53 (0.52, 0.54) | 0.96 (0.89, 1.02) | 0.53 (0.52. 0.54) |
| Staphylococcus pseudintermedius | 0.56 (0.52, 0.60) | 0.53 (0.52, 0.54) | 0.47 (0.44, 0.51) | 0.53 (0.52, 0.54) |
| Coagulase-negative staphylococci | 0.59 (0.58, 0.61) | 0.50 (0.49, 0.51) | 0.51 (0.50, 0.52) | 0.54 (0.53, 0.55) |
| Enterococcus faecalis | 0.82 (0.78, 0.85) | 0.53 (0.52, 0.54) | 0.76 (0.73, 0.80) | 0.53 (0.52, 0.54) |
| Other Gram-negative bacteriab | 0.83(0.77, 0.89) | 0.53 (0.52, 0.54) | 0.84 (0.78, 0.89) | 0.53 (0.52, 0.54) |
| Streptococcus pyogenes | 0.81 (0.67, 0.98) | 0.53 (0.52, 0.54) | 0.76 (0.62, 0,93) | 0.53 (0.52, 0.54) |
| Enterococcus canis | 0.74 (0.61, 0.88) | 0.53 (0.52, 0.54) | 0.65 (0.53, 0.78) | 0.53 (0.52, 0.54) |
| Trueperella pyogenes | 0.87 (0.73, 1,03) | 0.53 (0.52, 0.54) | 0.82 (0.68, 0.97) | 0.53 (0.52, 0.54) |
| Micrococcus spp. | 0.59 (0.54, 0.64) | 0.53 (0.52, 0.54) | 0.51 (0.46, 0.55) | 0.53 (0.51, 0.54) |
| Other minor pathogens combinedc | 0.65 (0.61, 0.70) | 0.53 (0.52, 0.54) | 0.58 (0.54, 0.62) | 0.53 (0.52, 0.54) |
| Minor pathogens | 0.60 (0.59, 0.62) | 0.49 (0.48, 0.50) | 0.52 (0.51, 0.53) | 0.54 (0.53, 0.55) |
| All bacteria isolated | 0.65 (0.64, 0.67) | 0.67 (0.66, 0.68) | 0.58 (0.57,0.59) | 0.73 (0.72, 0.75) |
Source: Milk laboratory, Faculty of Veterinary Science, University of Pretoria
a
, Major Gram-negative pathogens: Escherichia coli, Klebsiella pneumonia and Serratia spp.;
b
, other Gram-negative bacteria: all Gram-negative isolated excluding Escherichia coli, Klebsiella pneumonia and Serratia spp.;
c
, other minor pathogens combined: Streptococcus pyogenes, Enterococcus canis, Trueperella pyogenes and Micrococcus spp.