Detection of Resistant and Enterotoxigenic Strains of Staphylococcus warneri Isolated from Food of Animal Origin

Pathogenic potential of meat-borne coagulase negative staphylococci strains from slaughterhouse to fork

This study aimed to determine the prevalence of coagulase-negative staphylococci (CoNS) in meat processing lines for their pathogenic potential associated with biofilm formation, staphylococcal toxin genes, and antibiotic resistance in obtained isolates. Out of 270 samples, 56 isolates were identified as staphylococcal with their species level, and their antimicrobial resistance profiles were also determined with the BD Phoenix™ system. Among these, CoNS were found in 32 isolates, including S. epidermidis (22%), S. warneri (22%), S. cohnii (9%), S. schleiferi (9%), S. capitis (6%), S. haemolyticus (6%), S. lugdunensis (6%), S. chromogenes (6%), S. kloosii (3%), S. sciuri (3%), S. lentus (3%), and S. caprae (3%). Biofilm formation was observed in 78.1% of CoNS isolates, with 56% being strong biofilm producers; and the frequency of the icaA, fnbA, and fnbB genes were 43.7% and 34.3%, and 9.3% in isolates, respectively. Twenty-five (78.1%) of these strains were resistant to at least one antimicrobial agent, 20 (80%) of which exhibited multidrug resistance (MDR). Regarding genotypic analyses, 15.6%, 22.2%, 87.5%, and 9% of isolates, were positive for blaZ, ermC, tetK, and aacA-aphD, respectively. In 8 (25%) of all isolates had one or more staphylococcal toxin genes: the sed gene was the most frequent (12.5%), followed by eta (9.3%), tst-1 (6.25%), and sea (3.1%). In conclusion, this study highlights meat; and meat products might be reservoirs for the biofilm-producing MDR-CoNS, which harbored several toxin genes. Hence, it should not be ignored that CoNS may be related to foodborne outbreaks.

Deciphering the Genetic Architecture of Staphylococcus warneri Prophage vB_G30_01: A Comprehensive Molecular Analysis

The current knowledge of Staphylococcus warneri phages is limited, with few genomes sequenced and characterized. In this study, a prophage, vB_G30_01, isolated from Staphylococcus warneri G30 was characterized and evaluated for its lysogenic host range. The phage was studied using transmission electron microscopy and a host range. The phage genome was sequenced and characterized in depth, including phylogenetic and taxonomic analyses. The linear dsDNA genome of vB_G30_01 contains 67 predicted open reading frames (ORFs), classifying it within Bronfenbrennervirinae. With a total of 10 ORFs involved in DNA replication-related and transcriptional regulator functions, vB_G30_01 may play a role in the genetics and transcription of a host. Additionally, vB_G30_01 possesses a complete set of genes related to host lysogeny and lysis, implying that vB_G30_01 may influence the survival and adaptation of its host. Furthermore, a comparative genomic analysis reveals that vB_G30_01 shares high genomic similarity with other Staphylococcus phages and is relatively closely related to those of Exiguobacterium and Bacillus, which, in combination with the cross-infection assay, suggests possible cross-species infection capabilities. This study enhances the understanding of Staphylococcus warneri prophages, providing insights into phage-host interactions and potential horizontal gene transfer.

The Opportunistic Pathogen Staphylococcus warneri: Virulence and Antibiotic Resistance, Clinical Features, Association with Orthopedic Implants and Other Medical Devices, and a Glance at Industrial Applications

In recent decades, the risk of developing opportunistic infections has increased in parallel with the ever-increasing number of people suffering from chronic immunosuppressive diseases or undergoing prosthetic surgery. Staphylococcus warneri is a Gram-positive and coagulase-negative bacterium. Usually found as a component of the healthy human and animal microbiota of the skin and mucosae, it can take on the role of an opportunistic pathogen capable of causing a variety of infections, ranging from mild to life-threatening, not only in immunocompromised patients but even, although rarely, in healthy people. Here, in addition to a concise discussion of the identification and distinguishing features of S. warneri compared to other staphylococcal species, a systematic overview of the findings from case reports and clinical studies is provided. The paper highlights the virulence and antibiotic resistance profiles of S. warneri, the different clinical contexts in which it has proven to be a serious pathogen, emphasizing its ability to colonize artificial prosthetic materials and its tropism for musculoskeletal and cardiovascular tissues. Some original data on orthopedic implant infections by S. warneri complement the discussion. Finally, from a different perspective, the paper addresses the possibilities of industrial exploitation of this bacterium.

Integrating multi-wet laboratory diagnostics to study staphylococci in animals in Uganda

BACKGROUND

Several diagnostic environments in Uganda lack real-time, robust and high-throughput technologies for comprehensive typing of microbes, which is a setback to infectious disease surveillance. This study combined various wet laboratory diagnostics to understand the epidemiology of pathogenic staphylococci isolated from animals in Uganda and the implications for global health security priorities.

METHODS

A retrospective study was conducted employing records and pathogenic staphylococci (from animals) archived at the Central Diagnostic Laboratory (CDL), Makerere University, Uganda, between January 2012 and December 2019. The bacteria were speciated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and tested for virulence factors [beta lactamases, lecithinase, deoxyribonuclease (DNase), haemolysins] and resistance to ten antimicrobials of clinical and veterinary relevance. Tetracycline and methicillin resistance genes were also tested.

RESULTS

The prevalent diseases were mastitis in cattle and skin infections in dogs. Of the 111 staphylococci tested by MALDI-TOF MS, 79 (71.2%) were Staphylococcus aureus, 27 (24.3%) were Staphylococcus pseudintermedius and 5 (4.5%) were Staphylococcus schleiferi. All these strains expressed haemolysins. The prevalence of strains with lecithinase, penicillinase, cephalosporinase and DNase was 35.9% (14/39), 89.7% (35/39), 0.0% (0/39) and 87.2% (34/39), respectively. Staphylococci were primarily resistant to early penicillins (over 80%), tetracycline (57.7%), and chloramphenicol (46.2%). Minimal resistance was noted with cloxacillin (0.0%), ciprofloxacin (9.6%), and cefoxitin (3.8%). The prevalence of multidrug resistance (MDR) was 78.8% for general staphylococci, 82.2% for S. aureus, 73.1% for S. pseudintermedius, and 60.0% for S. schleiferi. Multidrug resistant staphylococci were significantly more prevalent in the cattle isolates than in the dog isolates (P < 0.05). The prevalence of methicillin-resistant staphylococci (MRS) tested by resistance to cefoxitin and mecA carriage was 3.8%. These four strains were all isolated from dog skin infections. The tetK gene was the most predominant (35.4%), followed by tetM (25.0%).

CONCLUSION

In resource-constrained settings, the approach of integrated diagnostics promises sustainable disease surveillance and the addressing of current capacity gaps. The emergence of MRS (zoonotic bacteria) in companion animals creates a likelihood of reduced treatment options for related human infections, a threat to global health.

Molecular characteristics and antibiotic resistance of Staphylococcus aureus and Staphylococcus haemolyticus isolated from bovine mastitis

Staphylococci are classified as one of the pathogens causing bovine mastitis that can pose not only an economic loss to the dairy farms, but a serious public-health threat based on their zoonotic potential. We focused to monitor phenotypes of the isolated strains of Staphylococcus aureus (S. aureus) and Staphylococcus haemolyticus (S. haemolyticus) from milk of cows with clinical mastitis, including antibiotic resistance, biofilm forming ability and the presence of biofilm- and toxin- related genes. From a total of 191 milk samples were identified as S. aureus - 12% (22 isolates) and S. haemolyticus - 6% (12 isolates). Automatic interpreted reading of the antibiogram evaluated potentially 12 isolates as methicillin-resistant S. aureus and methicillin-resistant coagulase-negative Staphylococci. Genotypically, the isolates were positive for blaZ and negative for mecA and mecC. Others important mechanisms were inducible macrolide-lincosamide-streptogramin B (iMLSB) resistance with presence of msrA, ermC, vgaA. The most detected biofilm-associated and toxins genes were clfA, sdrD, sdrE, fnbpB, bbp, isdA, isdB, hla and see. S. aureus isolates were subjected to spa typing. It turned out that despite the strains coming from different farms, they were either resistant or sensitive to antibiotic, were all of the same spa-type t 10035. Our findings revealed the presence iMLSB, which, to our best knowledge, were described in Slovakian bovine staphylococci rarely. The majority of isolates were multidrug-resistant and carried multiple virulence genes, posing a potential public-health risk.

Tigecycline Resistance-Associated Mutations in the MepA Efflux Pump in Staphylococcus aureus

Tigecycline is an important antibacterial drug for treating infection by clinical multidrug-resistant bacteria, and tigecycline-resistant Staphylococcus aureus (TRSA) has been increasingly reported in recent years. Notably, only rpsJ and mepA are associated with the tigecycline resistance of S. aureus. The mepA gene encodes MepA efflux pumps, and the overexpression of mepA has been confirmed to be directly related to tigecycline resistance. Although the mutations of MepA widely occur, the associations between TRSA and mutations of MepA are still unclear. In this study, we explored mutations in the mepA genes from various sources. Then, tigecycline resistance-associated mutations T29I, E287G, and T29I+E287G in MepA were identified, and their effects were evaluated through mutant deletion and complementation, tigecycline accumulation assay, and molecular docking experiments. Results showed that the MICs of tigecycline, gentamicin, and amikacin increased in special complementary transformants and recovered after the addition of the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The tigecycline accumulation assay of the mepA-deleted mutant strain and its complementary transformants showed that T29I, E287G, and T29I+E287G mutations promoted tigecycline efflux, and molecular docking showed that mutations T29I, E287G, and T29I+E287G decreased the binding energy and contributed to ligand binding. Moreover, we inferred the evolutionary trajectory of S. aureus under the selective pressure of tigecycline in vitro. Overall, our study indicated that mutations in MepA play important roles in tigecycline resistance in S. aureus. IMPORTANCE Previous analysis has shown that overexpression of MepA is an exact mechanism involved in tigecycline resistance apart from the rpsJ mutation and is usually dependent on the mutant mepR. However, no research has evaluated the effects of diverse mutations discovered in TRSA in MepA. This study demonstrates that the mutations in MepA confer resistance to tigecycline without overexpression and provides genotypic references for identifying TRSA. Although tigecycline resistance-associated mutations in MepA identified in this study have not been observed in clinical isolates, the mechanism should be explored given that S. aureus strains are prevalent in the environment. Measures should be implemented to contain TRSA within the time window before tigecycline resistance-associated mutations in MepA are prevalent.