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

Abstract

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.

Non-aureus Staphylococci and Bovine Udder Health: Current Understanding and Knowledge Gaps

“…Interestingly, S. chromogenes is most frequently isolated from milk and skin (69), but not from other environmental sources, suggesting that it is likely host-adapted (49,62,(70)(71)(72). Literature suggests that this species is largely isolated from samples of bovine origin, although it can be isolated from the milk of other dairy ruminants including goats and dairy buffalo (73). According to Taponen et al (54), 55% of S. chromogenes persisted throughout lactation, while Fry et al (45) showed persistence based on PFGE.…”

Virulence Factors in Staphylococcus Associated with Small Ruminant Mastitis: Biofilm Production and Antimicrobial Resistance Genes

“…In the CNS group, S. caprae was the most found species and was isolated only from goat's milk samples. It is a commensal organism that prevails in the skin of the goat udder [19] This species is most commonly found in cases of goat mastitis [37,[45][46][47], but it was also isolated from sheep [5,48], buffalo [17], and cow's milk [49].…”

Occurrence, antibiotic resistance and enteroxigenicity of Staphylococcus spp. in tonsils of slaughtered pigs in Greece

“…The isolates were further identified at the Staphylococcus spp. level by applying the matrix-assisted laser desorption ionization, timeof-flight mass spectrometry (MALDI-TOF MS) using a Microflex LT mass spectrometer (Bruker Daltonik GmbH, Bremen, Germany) as described by Gosselin et al (2018).…”