Pathogenicity and Antimicrobial Resistance in Coagulase-Negative Staphylococci

The coagulase-negative staphylococci (CoNS) group was considered saprophytic or rarely pathogenic for many years. Since the first case of septicemia caused by CoNS, there has been a progressive increase in the prevalence of healthcare-associated infections caused by CoNS. The CoNS group has emerged as one of the main causes of nosocomial infections related to vascular catheters and prostheses, especially among immunocompromised patients. This gradual increase in infections is due to the change in the relationship between patients and procedures since CoNS are closely related to devices implanted in the human body. CoNS are successful in colonizing the host because they have several virulence mechanisms, such as biofilm formation and production of enzymes and toxins, in addition to several mechanisms of resistance to antimicrobials. Despite their great clinical relevance, few studies have focused on CoNS’s pathogenicity and resistance to antimicrobials, which reveals the current need to better understand the factors by which this group became pathogenic to humans and other animals. This review aims to synthesize the aspects related to the pathogenicity and antimicrobial resistance in CoNS.

Two-stage revision arthroplasty for coagulase-negative staphylococcal periprosthetic joint infection of the hip and knee

BACKGROUND Periprosthetic joint infections(PJIs)are frequently caused by coagulase-negative Staphylococci(CoNS),which is known to be a hard-to-treat microorganism.Antibiotic resistance among causative pathogens of PJI is increasing.Two-stage revision is the favoured treatment for chronic CoNS infection of a hip or knee prosthesis.We hypothesised that the infection eradication rate of our treatment protocol for two-stage revision surgery for CoNS PJI of the hip and knee would be comparable to eradication rates described in the literature.AIM To evaluate the infection eradication rate of two-stage revision arthroplasty for PJI caused by CoNS.METHODS All patients treated with two-stage revision of a hip or knee prosthesis were retrospectively included.Patients with CoNS infection were included in the study,including polymicrobial cases.Primary outcome was infection eradication at final follow-up.RESULTS Forty-four patients were included in the study.Twenty-nine patients were treated for PJI of the hip and fifteen for PJI of the knee.At final follow-up after a mean of 37 mo,recurrent or persistent infection was present in eleven patients.CONCLUSION PJI with CoNS can be a difficult to treat infection due to increasing antibiotic resistance.Infection eradication rate of 70%-80%may be achieved.

Coagulase-negative Staphylococci in Conjunctivitis and Blepharitis

Coagulase-negative staphylococcus(C-NS)are regarded as normal flora of the lids and conjunctiva.The ability of these organisms to cause conjunctivitis and blepharitis can be overlooked or disregarded.To elucidate the role of individual C-NS species in these eye diseases we compared Staphylococcus sp.isolated from the conjunctiva and lids of 50 healthy volunteers with 248 strains of Staphylococcus isolated from patients with staphylococcal conjunctivitis or blepharitis.S.epidermidis was the most frequent species isolated from the conjunctiva and lids of both groups.S.aureus was isolated only from infected patients.No individual C-NS species was found to be significantly associated with eye disease,but the colony count of C-NS after isolation was a useful indicator of conjunctivitis and blepharitis.The ability of Staphylococcus to ferment mannitol or mannose was associated with isolates only from infected patients.

Evaluating the performance of the Alere PBP2a SA Culture Colony Test with the Vitek 2 Antimicrobial Susceptibility Test Card System as reference standard in coagulase-negative Staphylococcus species

Background The Alere PBP2a SA Culture Colony Test is an FDA-cleared in vitro immunochromatographic assay for rapid detection of penicillin-binding protein2a(PBP2a)in Staphylococcus aureus.Methods We investigated the performance of the PBP2a SA Culture Colony Test with 78 coagulase-negative Staphylococcus(CoNS)isolates from different body sites,with the Vitek 2 Antimicrobial Susceptibility Test(AST)as a reference standard.Results The CoNS species were 62 S.epidermidis;6 S.lugdenensis;3 S.hominis;2 S.capitis;2 S.haemolyticus;and 1 each of S.simulans,S.auricularis,and S.warneri.Of the 78 CoNS isolates,68 showed concordance in the PBP2a IC assay and Vitek 2 AST.Discordance was seen for 10 S.epidermidis isolates,which showed negative in the PBP2a assay,despite oxacillin-resistance detection using the Vitek 2 AST(66.7%sensitivity and 100%specificity).All non-S.epidermidis CoNS were identified with 100%concordance using the PBP2a IC assay and Vitek 2 AST.Conclusion We demonstrated that,while the PBP2a IC assay has low sensitivity in determining the susceptibility of S.epidermidis to oxacillin,it highly accurately predicted the susceptibility of non-S.epidermidis CoNS to oxacillin.The diagnostic accuracy for non-S.epidermidis CoNS needs further assessment with more isolates to confirm our findings.

Molecular Detection of Resistance and Virulence Genes in Coagulase Negative Staphylococci Isolated from Blood Cultures at the University Teaching Hospital of Bouake

Introduction: Coagulase-negative staphylococci (CoNS) are currently recognized as genuine pathogens. However, little is known about the resistance and virulence genes that explain their pathogenicity in hospitals in Cte d'Ivoire. The aim of this study was to contribute to the genotypic identification of resistance and virulence genes in CoNS isolated from blood cultures at the University Teaching Hospital (CHU) of Bouak, in order to improve patient management. Material and Methods: This was a descriptive study conducted from September to December 2023. The CoNS isolates studied came from the collection of strains isolated from blood cultures of febrile patients hospitalized or attending consultations at the CHU of Bouak. The strains were analyzed using conventional simplex PCR. Results: Of the 45 isolates analyzed, 46.7% carried both the aacA-aphD and tetK genes and 40% carried the mecA gene. With regard to virulence genes, only the LukS-PV gene was observed in S. epidermidis and S. haemolyticus isolates. Conclusion: The high prevalence of CoNS isolates carrying the mecA gene and the presence of virulence genes observed in this study give cause for concern in hospitals. It is important to develop comprehensive surveillance strategies against nosocomial and multi-resistant infections at the CHU of Bouak.

鸡舍空气中葡萄球菌的分离鉴定及耐药性分析

凝固酶阴性葡萄球菌是广泛存在于自然界中的一种革兰氏阳性条件致病菌,畜禽养殖舍是其病原体传播的一个重要传染源,但其在家禽舍气溶胶中的流行情况和特征并不明确。通过对从家禽养殖舍生物气溶胶采集而来的细菌进一步分离鉴定,共获得了102株凝固酶阴性葡萄球菌(coagulase-negative staphylococci,CoNS),其中松鼠葡萄球菌(41.18%)是最主要的菌种,此外还包括马胃葡萄球菌(21.57%)、腐生葡萄球菌(18.63%)、溶血葡萄球菌(10.78%)、木糖葡萄球菌(5.88%)等。耐药性分析结果显示,分离的葡萄球菌对青霉素、氨苄西林、环丙沙星、氯霉素、红霉素、四环素、克林霉素和苯唑西林均呈现高耐药率。PCR检测结果显示,有36.3%的菌株携带有耐药基因mecA,且均对苯唑西林耐药,而mecA是耐甲氧西林金黄色葡萄球菌(MRSA)的标志耐药基因。

Comparison of aerobic conjunctival bacterial flora in pregnant, reproductive-aged and postmenopausal women

AIM: To evaluate the effect of hormonal status on aerobic conjunctival flora in women. METHODS: One hundred fifty-eight women [reproductive-aged (n=55), pregnant (n=51), and postmenopausal (n=52)] who admitted to outpatient clinic of Obstetrics and Gynecology Department of Denizli State Hospital were enrolled. Age, body-mass index (BMI), obstetric history, cigarette smoking, drug usage, presence of systemic disease, and intraocular pressure (IOP) were recorded for each patient. The samples were taken from the lower fornix with two culture swabs and directly incubated in culture containing 5% sheep blood, eosin-methylene blue and chocolate agar. The other swab specimen was Gram stained. All growths and microscopic results were analyzed. RESULTS: The coagulase-negative Staphylococcus was the predominant organism isolated in the conjunctival samples in both three groups. The aerobic microorganism growth rate for all isolated aerobic organisms revealed no significant change in the three groups (P>0.05). The conjunctival culture positivity rates were similar in the three groups (49% in reproductive-aged, 57% in pregnant and 58% in postmenopausal women) (P>0.05). Age, IOP, BMI, gravidity, parity, cigarette smoking, drug usage, and presence of systemic diseases did not have an effect on culture positivity in three groups. CONCLUSION: Results of this study showed that conjunctival aerobic flora and bacterial colonization did not differ between reproductive-aged, pregnant and postmenopausal women.

Clinical Impact of Bacteremia Due to <i>Staphylococcus saprophyticus</i>

Objective: This was a retrospective study to evaluate the clinical impact of bacteremia due to Staphylococcus saprophyticus and identify which factors influence it. Methods: We reviewed all patients with bacteremia due to S. saprophyticus over the last 12 years. This study was performed at Jichi Medical University Hospital in Japan, a key hospital in the northern Kanto area including Tochigi, Gunma, Ibagagi, and northern Saitama prefectures. We retrospectively reviewed the blood culture results and medical records of all patients with a history of visits or hospitalizations between April 2008 and September 2020. Results: During the study period, 4 blood culture specimens were considered to have S. saprophyticus bacteremia. Two of these were from subjects > 60 years old who had severe infection. A third case, 27 years old, was thought to have a catheter-related bloodstream infection;however, the only symptom was fever, which was not serious. The fourth case, a previously unreported pediatric patient, had non-severe fever. The mean time for a diagnosis of bacteremia by blood culture testing was 42 hours, whereas contamination appeared in cultures after another 50 hours. Conclusion: The pathogenicity of S. saprophyticus might be lower in the blood than in the urine due to its physiological function and activity. In older adults with underlying diseases, the severity of bacteremia was more pronounced, whereas in a young adult and a child, the disease was relatively mild. Age and underlying disease might be useful factors to consider when diagnosing bacteremia due to S. saprophyticus.