Characterization of coagulase-negative staphylococci and macrococci isolated from cheese in Germany

Abstract

Cheese, especially ripened varieties, harbor a very complex and heterogeneous microbiota. In addition to the desired microorganisms (starter cultures) added during cheese production, potentially harmful bacteria may also enter the production chain. Regarding the latter, the focus of this study was on coagulase-negative staphylococci (CNS) and Macrococcus caseolyticus. Both are known to harbor a variety of genes coding for antibiotic resistance, including mecA, mecB, mecC, and mecD. Coagulase-negative staphylococci or macrococci carrying such genes or other virulence factors should not be present in cheese. Cheese samples (101 in total) were collected from retail sources. Coagulase-negative staphylococci and M. caseolyticus were isolated utilizing selective agars, and species were identified by phenotypical tests and partial sequencing of the sodA gene. The results allowed identification of 53 CNS strains and 19 M. caseolyticus strains. Among the CNS, 11 isolates of Staphylococcus saprophyticus and one Staphylococcus epidermidis isolate were obtained. Both species are potential human pathogens and may thus adversely affect the safety of these food products. Screening for antimicrobial resistance was performed by application of disc diffusion tests, a gradient strip-test, and 14 different PCR tests. Evidence for methicillin resistance (by either positive disc diffusion assay for cefoxitin or by mec PCR) was found in CNS isolates and M. caseolyticus (9 isolates each). Regarding other virulence factors, no genetic determinants for coagulase or the most common staphylococcal enterotoxins sea, seb, sec, sed, and see were detected in any of the CNS or M. caseolyticus isolates by PCR testing. In conclusion, the presence of facultatively pathogenic CNS and carriers of genes for antibiotic resistance in both groups of microorganisms, especially mec genes, and the respective food safety issues need further evaluation and surveillance.

Antimicrobial resistance and virulence profiles of staphylococci isolated from clinical bovine mastitis

“…However, the toxin-encoding genes were not observed in any of the CNS isolates in our study. Our results were similar to those presented by other authors that all CNS species were negative for the toxin genes, even though a wide range of genes were tested ( Nemati et al, 2008 ; Klempt et al, 2022 ). This may be attributed to the fact that the low prevalence of toxin-producing CNS isolates in the studied area, or the presence of other toxin genes which were not tested ( Xu et al, 2015 ).…”

Recent Records on Bacterial Opportunistic Infections via the Dietary Route

“…Coagulase-negative staphylococci (CNS) are frequently found in raw fermented meats and cheeses since they are natural colonizers of skin and mucosae in animals and humans [ 76 , 77 , 78 ]. Among these, Staphylococcus epidermidis and, in a minority of cases, S. capitis , S. haemolyticus , S. hominis , and S. warneri were responsible for 90% of the cases of late onset sepsis (LOS) in neonatal intensive care units (NICUs) [ 79 ].…”

“…Among these, Staphylococcus epidermidis and, in a minority of cases, S. capitis , S. haemolyticus , S. hominis , and S. warneri were responsible for 90% of the cases of late onset sepsis (LOS) in neonatal intensive care units (NICUs) [ 79 ]. LOS is defined as a bloodstream infection occurring between 3 and 28 days of life and is caused by bacteria transmitted horizontally in the hospital or community environment [ 78 ]. CNS are the most common organisms in mucocutaneous sites and the nasopharynx in the first week of life and the infection risk factors are extreme prematurity and parenteral nutrition with intravascular catheters.…”

Assessment of sodium chloride tolerance and antibiotic resistance of Citrobacter braakii EC-PS1 and Macrococcus caseolyticus Li-PT1 isolated from artisanal cheeses

“…M. caseolyticus from cheese samples showed resistance to cefoxitin, penicillin G, harbouring also methicillin resistance genes . Results suggest that this is a food safety concern because of the broad-host dissemination of the mecD gene (Klempt et al ., 2022) . In milk samples originating from cows with subclinical mastitis, it was detected M. caseolyticus bacteria showing antibiotic resistance towards ampicillin, cefoxitin, erythromycin, oxacillin, and penicillin (de Oliveira et al, 2022) .…”

“…In Brazilian cheese samples, they identified bacteria showing resistance to clinically relevant antimicrobials such as penicillin, cefoxitin, oxacillin, clindamycin, erythromycin, tetracycline, tobramycin, gentamicin, ciprofloxacin, chloramphenicol, and also community-acquired methicillin-resistant Staphylococcus aureus (Aguiar et al ., 2022) . Methicillin resistance was found in coagulase-negative staphylococci isolates and in Macrococcus caseolyticus (Klempt et al ., 2022) . M. caseolyticus with casein-hydrolysing capacity was found in the bacterial community of cow's milk in artisanal cheeses from north-western Argentina (Suárez et al, 2020) .…”