Coagulase-negative staphylococci isolated from two cases of toxic shock syndrome lack superantigenic activity, but induce cytokine production

Toxic Shock Syndrome: A Literature Review

Toxic shock syndrome (TSS) is a rare, life-threatening, toxin-mediated infectious process linked, in the vast majority of cases, to toxin-producing strains of Staphylococcus aureus or Streptococcus pyogenes. The pathophysiology, epidemiology, clinical presentation, microbiological features, management and outcome of TSS are described in this review. Bacterial superantigenic exotoxins induces unconventional polyclonal lymphocyte activation, which leads to rapid shock, multiple organ failure syndrome, and death. The main described superantigenic exotoxins are toxic shock syndrome toxin-1 (TSST-1) and enterotoxins for Staphylococcus aureus and Streptococcal pyrogenic exotoxins (SpE) A, B, and C and streptococcal superantigen A (SsA) for Streptococcus pyogenes. Staphylococcal TSS can be menstrual or nonmenstrual. Streptococcal TSS is linked to a severe group A streptococcal infection and, most frequently, to a necrotizing soft tissue infection. Management of TSS is a medical emergency and relies on early detection, immediate resuscitation, source control and eradication of toxin production, bactericidal antibiotic treatment, and protein synthesis inhibiting antibiotic administration. The interest of polyclonal intravenous immunoglobulin G administration as an adjunctive treatment for TSS requires further evaluation. Scientific literature on TSS mainly consists of observational studies, clinical cases, and in vitro data; although more data on TSS are required, additional studies will be difficult to conduct due to the low incidence of the disease.

Characterization and pathogenicity of multidrug-resistant coagulase-negative Staphylococci isolates in chickens

The pathogenic potential of vancomycin and methicillin-resistant coagulase-negative Staphylococci (VMRCoNS) on Egyptian poultry farms has received little attention. Therefore, this study aims to study the prevalence of CoNS in imported poultry flocks and commercial poultry farms, evaluate the presence of virulence and antibiotic resistance genes (sea, seb, sec, sed, see, and mecA), and assess their pathogenicity in broiler chicks. Seven species were identified among 25 isolates, such as 8 S. gallinarum, 5 S. saprophyticus, 5 S. chromogens, 3 S. warneri, 2 S. hominis, 1 S. caprae, and 1 S. epidermidis. All isolates were resistant to clindamycin, doxycycline, vancomycin, methicillin, rifampicin, and penicillin. The mecA gene was confirmed in 14 isolates, while the sed gene was revealed in seven isolates. Commercial 1-day-old Ross broiler chicks were divided into eight groups of three replicates (10 birds/group): group Ӏ was negative control; groups (П, Ш, IV, V, VI, VII, and VIII) were subcutaneously inoculated with 108 CFUml-1 of S. hominis, S. caprae, S. epidermidis, S. gallinarum, S. chromogens, S. warneri, and S. saprophyticus, respectively. Groups VIII and V had mortality rates of 100% and 20%, respectively, with no evidence of mortalities in the other groups. The highest re-isolation of CoNS species was recorded in groups VII, VIII, and V. Postmortem and histopathological examination revealed the common presence of polyserositis in the internal organs, and hepatic and myocardial necrosis in groups IV, V, and VI. These findings revealed the pathogenic potential of CoNS, so special attention must be directed toward their public health impact.

Staphylococcus epidermidis induced toxic shock syndrome (TSS) secondary to influenza infection

BACKGROUND

To date, few cases of TSS caused by coagulase negative (CoN) staphylococci have been reported in the literature. Recent data show that CoN staphylococci are capable of secreting a number of enterotoxins and cytotoxins, normally produced by S. aureus. Herewith, we describe a case of TSS caused by Staphylococcus epidermidis with a favorable outcome.

CASE PRESENTATION

We report a case of a 46-year-old man who developed TSS from S. epidermidis. The patient was admitted for a 7-day history of general malaise and headache following a recent influenza infection and a 3-day history of vomiting, diarrhea, diffuse erythroderma, and fever. The main laboratory findings on admission were leukopenia (WBC 800/mm3), thrombocytopenia (Plt count 78.000/mm3), elevated urea, creatine levels and increased inflammatory markers (CRP 368 mg/ml). The patient had clinical and radiological evidence of pneumonia with chest computed tomography (CT) showing diffuse bilateral airspace opacifications with air bronchogram. On the second day, a methicillin resistant S. epidermidis (MRSE) strain was detected in both sets of blood cultures, but the organism was unavailable for toxin testing. All other cultures and diagnostic PCR tests were negative. His clinical signs and symptoms fulfilled at that stage four out of five clinical criteria of TSS with a fever of 39 °C, diffuse erythroderma, multisystem involvement and hypotension. On the same day the patient was admitted to the ICU due to acute respiratory failure. The initial treatment was meropenem, vancomycin, levofloxacin, clindamycin, IVIG and steroids. Finger desquamation appeared on the 9th day of hospitalization, fulfilling all five clinical criteria for TSS.

CONCLUSIONS

To our knowledge, this is the first adult case with TSS induced by CoNS (MRSE) secondary to an influenza type B infection, who had favorable progression and outcome. Further research is warranted to determine how TSS is induced by the CoNS infections.

Toxic shock syndrome with a cytokine storm caused by Staphylococcus simulans: a case report

Background

Exotoxins secreted from Staphylococcus aureus or Streptococcus pyogenes act as superantigens that induce systemic release of inflammatory cytokines and are a common cause of toxic shock syndrome (TSS). However, little is known about TSS caused by coagulase-negative staphylococci (CoNS) and the underlying mechanisms. Here, we present a rare case of TSS caused by Staphylococcus simulans (S. simulans).

Case presentation

We report the case of a 75-year-old woman who developed pneumococcal pneumonia and bacteremia from S. simulans following an influenza infection. The patient met the clinical criteria for probable TSS, and her symptoms included fever of 39.5 °C, diffuse macular erythroderma, conjunctival congestion, vomiting, diarrhea, liver dysfunction, and disorientation. Therefore, the following treatment was initiated for bacterial pneumonia complicating influenza A with suspected TSS: meropenem (1 g every 8 h), vancomycin (1 g every 12 h), and clindamycin (600 mg every 8 h). Blood cultures taken on the day after admission were positive for CoNS, whereas sputum and pharyngeal cultures grew Streptococcus pneumoniae (Geckler group 4) and methicillin-sensitive S. aureus, respectively. However, exotoxins thought to cause TSS, such as TSS toxin-1 and various enterotoxins, were not detected. The patient’s therapy was switched to cefazolin (2 g every 8 h) and clindamycin (600 mg every 8 h) for 14 days based on microbiologic test results. She developed desquamation of the fingers on hospital day 8 and was diagnosed with TSS. Conventional exotoxins, such as TSST-1, and S. aureus enterotoxins were not detected in culture samples. The serum levels of inflammatory cytokines, such as neopterin and IL-6, were high. CD8+ T cells were activated in peripheral blood. Vβ2+ population activation, which is characteristic for TSST-1, was not observed in the Vβ usage of CD8+ T cells in T cell receptor Vβ repertoire distribution analysis.

Conclusions

We present a case of S. simulans-induced TSS. Taken together, we speculate that no specific exotoxins are involved in the induction of TSS in this patient. A likely mechanism is uncontrolled cytokine release (i.e., cytokine storm) induced by non-specific immune reactions against CoNS proliferation.

Inoculation Pneumonia Caused by Coagulase Negative Staphylococcus

Rationale

Although frequently retrieved in tracheal secretions of critically ill patients on mechanical ventilation, the existence of pneumonia caused by coagulase-negative staphylococci (CoNS) remains controversial.

Objective

To assess whether Staphylococcus haemolyticus (S. haemolyticus) inoculated in mice’s trachea can infect normal lung parenchyma, increasing concentrations of S. haemolyticus were intratracheally administered in 221 immunocompetent mice.

Methods

Each animal received intratracheally phosphate-buffered saline (PBS) (n = 43) or live (n = 141) or inactivated (n = 37) S. haemolyticus at increasing load: 1.0 × 10⁶, 1.0 × 10⁷, and 1.0 × 10⁸ colony forming units (CFU). Forty-three animals were sacrificed at 12 h and 178 were sacrificed at 36 h; 64 served for post-mortem lung histology, 157 served for pre-mortem bronchoalveolar lavage (BAL) analysis, and 42 served for post-mortem quantitative bacteriology of lung tissue. The distribution of biofilm-associated genes was investigated in the S. haemolyticus strain used in our in vivo experiment as well as among 19 other clinical S. haemolyticus strains collected from hospitals or nursing houses.

Measurements and Main Results

Intratracheal inoculation of 1.0 × 10⁸ CFU live S. haemolyticus caused macroscopic and histological confluent pneumonia with significant increase in BAL white cell count, tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein (MIP)-2. At 12 h, high concentrations of S. haemolyticus were identified in BAL. At 36 h, lung injury and BAL inflammation were less severe than at 12 h and moderate concentrations of species belonging to the oropharyngeal flora were identified in lung tissue. The inoculation of 1.0 × 10⁶ and 1.0 × 10⁷ CFU live S. haemolyticus caused histologic interstitial pneumonia and moderate BAL inflammation. Similar results were observed after inoculation of inactivated S. haemolyticus. Moreover, biofilm formation was a common phenotype in S. haemolyticus isolates. The low prevalence of the ica operon in our clinical S. haemolyticus strain collection indicated icaA and icaD independent-biofilm formation.

Conclusion

In immunocompetent spontaneously breathing mice, inoculation of S. haemolyticus causes concentration-dependent lung infection that spontaneously recovers over time. icaA and icaD independent biofilm formation is a common phenotype in S. haemolyticus isolates.

Coagulase-negative staphylococci

The definition of the heterogeneous group of coagulase-negative staphylococci (CoNS) is still based on diagnostic procedures that fulfill the clinical need to differentiate between Staphylococcus aureus and those staphylococci classified historically as being less or nonpathogenic. Due to patient- and procedure-related changes, CoNS now represent one of the major nosocomial pathogens, with S. epidermidis and S. haemolyticus being the most significant species. They account substantially for foreign body-related infections and infections in preterm newborns. While S. saprophyticus has been associated with acute urethritis, S. lugdunensis has a unique status, in some aspects resembling S. aureus in causing infectious endocarditis. In addition to CoNS found as food-associated saprophytes, many other CoNS species colonize the skin and mucous membranes of humans and animals and are less frequently involved in clinically manifested infections. This blurred gradation in terms of pathogenicity is reflected by species- and strain-specific virulence factors and the development of different host-defending strategies. Clearly, CoNS possess fewer virulence properties than S. aureus, with a respectively different disease spectrum. In this regard, host susceptibility is much more important. Therapeutically, CoNS are challenging due to the large proportion of methicillin-resistant strains and increasing numbers of isolates with less susceptibility to glycopeptides.

[Toxic shock syndrome: experience in a pediatric intensive care unit]

OBJECTIVES

To review patients with toxic shock syndrome (TSS) in a pediatric intensive care unit.

METHODS

We performed a retrospective study of patients with TSS admitted to the intensive care unit in the previous 15 years. The patients included were those that met the clinical and microbiological criteria for TSS proposed by the Centers for Disease Control and Prevention.

RESULTS

There were nine patients (four boys). The mean age was 7 years. The most frequent findings were fever (100 %), hypotension (100 %), erythroderma (100 %), multisystem organ failure [coagulopathy (100 %), lethargy (89 %), hypertransaminasemia (89 %), increased creatine phosphokinase levels (78 %), renal failure (66 %)] and cutaneous desquamation (100 %). Laboratory studies showed changes in the leukocyte count and C-reactive protein value in all patients. The etiology was as follows: Staphylococcus was detected in six patients (S. epidermidis in three and S. aureus in three) and Streptococcus was detected in two patients (S. pyogenes in one and S. pneumoniae in one); no microorganisms were detected in only one patient. The origin of the infection was identified in seven patients (cutaneous in six patients and tonsillar in one). All patients received life support and antibiotic treatment. Six patients received corticosteroid treatment and one received intravenous immunoglobulins. Patients with TSS secondary to Streptococcus showed the greatest severity, exhibiting renal failure and requiring greater respiratory and circulatory support. All patients recovered well from the infection, without serious long-term sequelae. CONCLUSION. TSS should be included in the differential diagnosis of patients with fever, exanthema and shock, since early diagnosis has been shown to improve outcomes. S. pneumoniae should be included among the microorganisms that cause TSS. Treatment is based on life support measures and antibiotic therapy.

Neonatal immune responses to coagulase-negative staphylococci

PURPOSE OF REVIEW

Coagulase-negative staphylococci have emerged as the most common nosocomial pathogen in neonatal intensive care units worldwide. Our understanding of the interactions between coagulase-negative staphylococci and the immune system is incomplete, especially in the newborn. This review summarizes current knowledge on the human immune response to coagulase-negative staphylococci, with particular emphasis on the neonatal innate immune system.

RECENT FINDINGS

There are very limited data on innate immune responses to coagulase-negative staphylococci in neonates. Levels of serum proteins, including transplacental anti-coagulase-negative staphylococci immunoglobulin and complement, correlate with gestational age, and this relative deficiency in preterm infants contributes to their suboptimal opsonization and impaired bacterial killing of coagulase-negative staphylococci. In adults, coagulase-negative staphylococci elicit significant cytokine responses in vitro, which are probably partly mediated by Toll-like receptors, including Toll-like receptor type 2, but these pathways have not been characterized in the high-risk neonatal population.

SUMMARY

The susceptibility of human preterm neonates to coagulase-negative staphylococci relates partly to the immaturity of the neonatal immune response. Strategies to reduce the burden of coagulase-negative staphylococci infections require a thorough understanding of host-pathogen interactions, particularly the engagement of coagulase-negative staphylococci by the neonatal innate immune system.

Relationship between haemolytic and sphingomyelinase activities in a partially purified beta-like toxin from Staphylococcus schleiferi

beta-Toxins of staphylococcal species possess dual activity in that they can both lyse erythrocytes (by 'hot-cold' lysis) and catalyse hydrolysis of membrane-associated sphingomyelin. However, the precise relationship between these two activities has not been extensively studied. We have partially purified a beta-like toxin from culture supernatants of Staphylococcus schleiferi N860375 which exhibits both 'hot-cold' lysis of erythrocytes and neutral sphingomyelinase activities. This toxin has a strong preference for sheep erythrocytes, the membranes of which are rich in sphingomyelin. Kinetic analysis suggests that haemolysis and sphingomyelinase activities are very closely associated obeying identical Michaelis-Menten kinetics. However, pre-treatment with antibodies to Staphylococcus aureus beta-toxin, Ca(2+), dithiothreitol and phenylmethylsulfonyl fluoride appear to inhibit sphingomyelinase activity significantly more strongly than haemolysis while Mg(2+) activates sphingomyelinase activity more strongly than haemolysis. We attribute these effects to differences in binding properties in the two assays. Micropurification by both sphingosylphosphocholine-agarose affinity chromatography and preparative electrophoresis revealed that the 34-kDa toxin associates non-covalently with individual proteins.

Involvement of enterotoxins G and I in staphylococcal toxic shock syndrome and staphylococcal scarlet fever

We investigated the involvement of the recently described staphylococcal enterotoxins G and I in toxic shock syndrome. We reexamined Staphylococcus aureus strains isolated from patients with menstrual and nonmenstrual toxic shock syndrome (nine cases) or staphylococcal scarlet fever (three cases). These strains were selected because they produced none of the toxins known to be involved in these syndromes (toxic shock syndrome toxin 1 and enterotoxins A, B, C, and D), enterotoxin E or H, or exfoliative toxin A or B, despite the fact that superantigenic toxins were detected in a CD69-specific flow cytometry assay measuring T-cell activation. Sets of primers specific to the enterotoxin G and I genes (seg and sei, respectively) were designed and used for PCR amplification. All of the strains were positive for seg and sei. Sequence analysis confirmed that the PCR products, corresponded to the target genes. We suggest that staphylococcal enterotoxins G and I may be capable of causing human staphylococcal toxic shock syndrome and staphylococcal scarlet fever.

An inflammatory polypeptide complex from Staphylococcus epidermidis: isolation and characterization

Staphylococcus epidermidis releases factors that activate the HIV-1 long terminal repeat, induce cytokine release, and activate nuclear factor B in cells of macrophage lineage. The active material had a mass of 34,500 daltons, was inactivated by proteases and partitioned into the phenol layer on hot aqueous phenol extraction, and thus was termed phenol-soluble modulin (PSM). High performance liquid chromatography (HPLC) of crude PSM yielded two peaks of activity designated PSM peak 1 and peak 2. MALDI-TOF (matrix-assisted laser desorption ionization-time of flight) mass spectroscopy indicated the presence of two components in peak 1, which were designated PSM and PSM. Peak 2 contained a single component, designated PSM. Separation of PSM and PSM in peak 1 could be achieved by a second HPLC procedure. The structure of each component was determined by amino acid sequence analysis and identification and sequencing of their genes. PSM, PSM, and PSM were 22-, 44-, and 25-amino acid, respectively, strongly hydrophobic polypeptides. PSM was identified as Staphylococcus epidermidis delta toxin, whereas PSM and PSM exhibited more distant homology to previously described staphylococcal toxins. They appeared to exist as a complex or aggregate with activity greater than the component parts. The properties of the S. epidermidis PSMs suggest that they may contribute to the systemic manifestations of Gram-positive sepsis.

Detection of staphylococcal superantigenic toxins by a CD69-specific cytofluorimetric assay measuring T-cell activation

The presence of staphylococcal superantigenic toxins in the supernatants of liquid cultures was detected by an easy and rapid method assessing the activation of T lymphocytes by cytofluorimetric measurement of CD69 expression. Staphylococcus aureus cells were grown in Eagle's minimum essential medium supplemented with 5% heat-inactivated fetal calf serum. Supernatant fluids from all S. aureus strains producing superantigen-related toxins, including enterotoxins A to E, toxic shock syndrome toxin, and exfoliative toxins A and B, induced CD69 expression in a significantly higher number of T cells than a cutoff of 2%. This CD69 assay might be used for initial detection of superantigens from S. aureus strains isolated in the context of staphylococcal toxemia or related chronic human diseases such as atopic dermatitis or Kawasaki syndrome.