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PubMed1984

Frequency of isolation of enterotoxigenic staphylococci from milk of nursing mothers in Kaduna, Nigeria.

Milk samples from 251 nursing mothers were screened for enterotoxigenic staphylococci. The incidence of staphylococci in milk samples was 71.3%. Two hundred and sixteen strains were isolated from 179 mothers. Eighty-six (39.8%) of the 216 strains were found to be toxigenic. Enterotoxin type A (SEA) predominated, with 41 strains (19.0%) elaborating it. Twenty-one strains (9.7%) produced enterotoxin B (SEB) while only eight (3.7%) produced enterotoxin C (SEC). Ten strains (4.6%) produced all three types. Enterotoxigenic strains usually produced coagulase, thermonuclease and alpha haemolysin. In this series breast-feeding alone was more common than combined breast and bottle feeding, especially among mothers less than 30 years old. The incidence of reported infantile diarrhoea decreased with increasing age of the mother. Of 16 babies with diarrhoea, 10 (62.5%) had mothers whose milk yielded staphylococci. Six of these were toxigenic. Although no direct relationship between enterotoxigenic staphylococci in the milk of nursing mothers and infantile diarrhoea could be demonstrated, these findings reveal a potential health risk to these infants.

Coagulase↗
PubMed1987

Emergence of coagulase negative staphylococci as major nosocomial bloodstream pathogens.

Over an eight year period, 1975 to 1982, 1,843 nosocomial bloodstream infections were identified by routine prospective surveillance at the University of Virginia Hospital (106/10,000 admissions). Despite a decline in overall bloodstream infection rates during the study period (P = .085), bloodstream infections due to gram positive organisms increased from 29 (1975-1978) to 43/10,000 (1979-1982), (P less than 0.001). Notably, rates for coagulase negative staphylococci increased from 5.2 (1975-1978) to 12.4/10,000 (1979-1982), (P less than 0.001). In 1982, coagulase negative staphylococci accounted for 17% of all bloodstream infections and were the most frequently isolated pathogens. Sixty-four percent of patients with coagulase negative staphylococci were in critical care units versus 41% with other bloodstream infections (P less than .05). The recognition of coagulase negative staphylococci as significant bloodstream pathogens markedly alters the clinician's approach to nosocomial septicemia.

Coagulase↗
PubMed2003

Effects of staphylococci on cytokine production from human keratinocytes.

BACKGROUND: Staphylococcus skin infection is characterized by the infiltration of numerous neutrophils within the epidermis; however, the precise mechanism of epidermal infiltration of neutrophils during skin infection with staphylococci is not well understood and the factors regulating the neutrophil recruitment are yet to be determined. OBJECTIVES: We investigated the effects of staphylococci on cytokine production from keratinocytes, specifically to elucidate the mechanisms of neutrophil infiltration within the epidermis in cutaneous microbial infection. METHODS: Cytokine production from human keratinocytes was examined after stimulation with heat-killed Staphylococcus aureus, S. epidermidis and S. intermedius. RESULTS: Interleukin (IL)-6 and IL-8 were detected in the culture supernatants by enzyme-linked immunosorbent assay but IL-1beta, monocyte chemotactic protein-1 and tumour necrosis factor-alpha were not. IL-6 and IL-8 mRNAs were also confirmed by reverse transcription-polymerase chain reaction in the keratinocytes stimulated with killed staphylococci for 1, 3, 6, 10 and 24 h. CONCLUSIONS: These results could explain the epidermal infiltration of neutrophils in cutaneous infection with staphylococci, suggesting that the analysis of cytokines might add valuable information for the pathogenesis of cutaneous infection with Staphylococcus species.

Cells, Cultured↗
PubMed2003

Staphylococcal accessory gene regulator (sar) as a signature gene to detect enterotoxigenic staphylococci.

AIMS: To evaluate the use of a staphylococcal accessory gene regulator (sar) as a means of detecting enterotoxigenic staphylococci. METHODS AND RESULTS: SarA gene-specific primers were designed and applied in PCR, which resulted in the detection of 49 sar-positive isolates from a total of 67 natural food isolates of staphylococci. Colony hybridization using PCR-generated Digoxigenin (DIG)-labelled sarA probe tested in spiked samples of khoa (a traditional heat-concentrated milk product) comprising a mixed microflora ensured the specificity of the probe. Validation experiments with the commercial samples of khoa also demonstrated the specificity of the probe. PCR characterization for enterotoxins A-D revealed the presence of at least one of the toxin-encoding genes in all the sarA-positive isolates tested. CONCLUSION: The study indicated that sarA gene could be an ideal marker gene either in colony hybridization or in PCR, for an effective detection of potentially enterotoxigenic strains of staphylococci in a food system. SIGNIFICANCE AND IMPACT OF THE STUDY: As an alternative to targeting the individual toxin genes, a regulatory gene responsible for controlling the synthesis of various virulence factors may be a suitable target gene for screening potentially toxigenic staphylococci in food system using nucleic acid-based methods.

Animals↗
PubMed2000

In vitro activity of quinupristin/dalfopristin in comparison with five antibiotics against worldwide clinical isolates of staphylococci.

OBJECTIVE: To evaluate the in vitro activity of quinupristin/dalfopristin (Q/D), a streptogramin combination, in comparison with five antibiotics against worldwide clinical isolates of staphylococci. METHODS: A multicenter in vitro study was performed using the E test during a period of 3 months (April to June) in 1997 on fresh, clinically significant, non repetitive strains of staphylococci from patients hospitalized in 23 different hospitals in 18 countries tested. RESULTS: A total of 2132 staphylococcal isolates including methicillin resistant (MR), methicillin susceptible (MS) S. aureus (1003 MS, 462 MR), S. epidermidis (169 MS, 251 MR), S. haemolyticus (28 MS, 46 MR), S. hominis (28 MS, 16 MR), and coagulase negative staphylococci (86 MS, 43 MR) were analyzed. Q/D was highly active against all species tested. MIC90 (mg/L) ranged from 0.5 to 2 depending on the species. Strains had MIC < or = 1 mg/L in 97.6%. For S. aureus, S. epidermidis, S. hominis and other coagulase-negative staphylococci no differences in MIC90 were observed for MS or MR. One dilution difference was observed for S. haemolyticus, which overall was the less susceptible species. Erythromycin resistance was observed among 57- 87% of MR-strains and was lower among MS-strains (18-56%). Erythromycin resistance had no or little influence on MIC of Q/D. In comparison to vancomycin, Q/D was two to four times more active. CONCLUSIONS: The streptogramin combination Q/D showed an excellent in vitro activity against all staphylococcal species tested regardless of the resistance pattern to other drug classes, particularly resistance to methicillin. Q/D was two to four times more active than vancomycin and MIC values varied from 0.5-2 according to the species. The synergy of Q/D was well conserved in macrolide-resistant strains.

Drug Resistance, Microbial↗
PubMed2000

In vitro activity of evernimicin and selected antibiotics against methicillin-resistant staphylococci: a 24-country study.

OBJECTIVE: To collect and analyze data on susceptibility of methicillin-resistant staphylococci to evernimicin and other antimicrobial agents. METHODS: Recent clinical isolates of methicillin-resistant staphylococci from 33 laboratories in North America, Europe and South Africa were investigated. RESULTS: Of the antimicrobial agents tested, evernimicin had the lowest MIC90s for methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci (0.75 and 1.0 mg/L, respectively). Resistance to ciprofloxacin and erythromycin was widespread, with higher levels of resistance in North America than in other regions. CONCLUSIONS: Susceptibility surveys help to determine the antimicrobial activity of new agents. Ciprofloxacin- and erythromycin-resistant staphylococci were prevalent throughout all regions.

Aminoglycosides↗
PubMed1999

Rapid detection of methicillin-resistant staphylococci by multiplex PCR.

A multiplex PCR was developed to detect the coagulase gene (coa; pathognomic of Staphylococcus aureus) and the mecA gene (characteristically encoding for methicillin resistance in staphylococci) in a single, rapid test. Suitable primers for the gene targets and an internal, amplification control were incorporated into a multiplex PCR assay, which was then optimized on a capillary air thermal cycler to improve the turnaround time of the test to approximately 1.5 hours. The assay was evaluated with 111 fresh clinical isolates of staphylococci. The multiplex PCR correctly distinguished between isolates of S. aureus, which were sensitive to methicillin (MSSA) and those resistant to it (MRSA). It also correctly differentiated between similar isolates of coagulase negative staphylococci (MSSE and MRSE respectively). It was concluded that this multiplex PCR was a rapid and reliable method for the detection of methicillin-resistant staphylococci.

Coagulase↗
PubMed1998

Poor value of surveillance cultures for prediction of septicaemia caused by coagulase-negative staphylococci in patients undergoing haemodialysis with central venous catheters.

Surveillance cultures for the demonstration of coagulase-negative staphylococci in patients on catheter haemodialysis were performed in an attempt to predict dialysis catheter-related septicaemia. In all, 43 patients with 67 haemodialysis catheters were followed for a 1-y period. Once a week, swab specimens were obtained from the skin at the insertion site and the hub, and blood cultures were obtained from the catheter. Among coagulase-negative staphylococci, S. epidermidis was the most frequently (80%) isolated species, and two biotypes accounted for 55.7% of the 41 biotypes isolated. 11 septicaemia cases due to coagulase-negative staphylococci occurred, all caused by S. epidermidis, and the incidence of S. epidermidis septicaemia was 21% among patients and 16% among catheter periods. S. epidermidis septicaemia occurred in 17%, 31% and 33% of all catheter periods in which S. epidermidis was cultured from the skin, hub and catheter blood, respectively. In two-thirds of all catheter periods, S. epidermidis was cultured from catheter blood despite lack of clinical signs of septicaemia. In conclusion, cultures from the skin, hub or catheter blood are not useful for prediction of dialysis catheter-related septicaemia due to coagulase-negative staphylococci. When septicaemia is suspected, peripheral blood cultures are mandatory to reach a correct diagnosis and aetiology.

Adult↗
PubMed1956

Studies on bacteriemia. I. Mechanisms relating to the persistence of bacteriemia in rabbits following the intravenous injection of staphylococci.

During the course of studies on the characteristics of experimental bacteriemia, staphylococci were swiftly cleared from the blood stream of rabbits during the initial 10 to 15 minutes following intravenous injection of microorganisms. A subsequent abrupt decline in the rate of clearance ensued, resulting in a low grade bacteriemia which was demonstrable for many hours. The experiments reported have indicated that this strain of staphylococcus is rapidly phagocyted within the vascular system of rabbits, and that viable staphylococci circulate within the cytoplasm of polymorphonuclear leukocytes. The removal mechanisms contained within the liver and spleen appear to preferentially trap circulating extracellular staphylococci. When most of the circulating staphylococci are contained within leukocytes, splanchnic removal declines or virtually ceases. These observations suggest that viable, intracellular microorganisms are responsible for the persistence of staphylococcal bacteriemia in rabbits following the phase of rapid removal from the blood stream.

Animals↗
PubMed1960

The phagocytosis and inactivation of staphylococci by macrophages of normal rabbits.

The phagocytosis and survival of staphylococci in the presence of rabbit macrophages has been studied quantitatively. The method permitted an independent measurement to be made of intracellular and extracellular bacteria during the course of phagocytosis. It was found that S. aureus was relatively resistant to phagocytosis. In the presence of specific immune serum, however, it was ingested at a rate comparable with that of S. albus in normal serum; under these conditions more than 90 per cent of bacteria of either strain were inactivated within 60 minutes. Since immune serum did not alter the susceptibility of S. aureus to inactivation within macrophages, it is concluded that S. aureus and S. albus are similar in respect to their ability to survive within macrophages. The inactivation of staphylococci occurred more slowly, and a greater percentage survived incubation for 180 minutes, in macrophages than in polymorphonuclear leucocytes. Moreover, they retained their morphology for many hours within the former cell, but disappeared rapidly from the cytoplasm of granulocytes. It is suggested that the antibacterial mechanisms of the two cell types are fundamentally different. When studied over a prolonged period the staphylococci which survived early inactivation within macrophages were observed to die slowly over many hours. When they were recovered from cells and exposed to fresh macrophages, however, they were ingested and inactivated as readily as bacteria of the original population. It is suggested, therefore, that the prolonged survival in vitro of some staphylococci is due to variation in the efficiency of the antibacterial mechanism of exudative mononuclear phagocytes.

Animals↗
PubMed1952

The survival of staphylococci within human leukocytes.

In a study of the phagocytosis of staphylococci by human leukocytes it has been observed that strains of staphylococci producing human infection were phagocytized by human polymorphonuclear leukocytes in vitro under conditions in which virulent pneumococci, streptococci, or Klebsiella were rarely engulfed. In the presence of human leukocytes in plasma there was a rapid fall in the numbers of viable staphylococci of both pathogenic and non-pathogenic strains, the beginning of which was detectable in 10 to 15 minutes. The fall in culturable pathogenic microorganisms was considerably less marked, however, and a rapid resurgence of growth occurred in 4 to 8 hours, whereas the number of culturable non-pathogenic microorganisms remained low for 18 to 24 hours. These differences appear to be explained by the observation that a significant number of microorganisms of pathogenic strains were able to survive within human leukocytes. Such intracellular survival was found to be associated with evidence of destruction of the leukocytes. In contrast, non-pathogenic strains of staphylococci failed to survive within human polymorphonuclear leukocytes following ingestion.

Humans↗
PubMed1982

Gentamicin-resistant staphylococci as hospital flora: epidemiology and resistance plasmids.

In 1979, gentamicin-resistant (Gmr) Staphylococcus aureus was recovered from the clinical specimens of 22 epidemiologically unrelated hospitalized patients; 78% of the patients evaluated were also colonized with Gmr coagulase-negative staphylococci. Endonuclease fingerprinting was used to compare the Gmr plasmids within pairs of isolates of S. aureus and coagulase-negative staphylococci recovered from nine patients. Plasmids differed between pairs but were concordant within four pairs. Thus, in vivo interspecific plasmid transfer, although infrequent, may be important in the sporadic occurrence of Gmr S. aureus. To define the epidemiology of endemic Gmr coagulase-negative staphylococci, culture surveys were performed over two years. Gmr coagulase-negative staphylococci were acquired by 80% of the infants in a special-care nursery that previously had an outbreak of Gmr S. aureus. Among adult inpatients, a 48% colonization rate was related to prior exposure to antibiotics. In contrast, no colonization was found in outpatients or antepartum mothers.

Adult↗
PubMed1985

Human mononuclear cells exposed to staphylococci rapidly produce an inhibitor of neutrophil chemotaxis.

Serum-free cultures of human peripheral blood mononuclear cells from normal volunteers produce an inhibitor of neutrophil chemotaxis when exposed to heat-killed staphylococci. Human neutrophils were exposed to 100-fold dilutions of supernatants from 6-hr cultures, washed repeatedly, and assayed for chemotactic responsiveness with a radiolabel assay. Dilutions of supernatants from cell cultures exposed to staphylococci resulted in a mean chemotaxis of 856 +/- 83 cpm (n = 21), while that for medium-treated neutrophils was 1,354 +/- 100 cpm (n = 21, P less than .001), and supernatants from cultures without staphylococci produced chemotaxis of 1,107 +/- 132 cpm (n = 14, P greater than .05 vs. medium-treated). Fifty-three experiments on tissue from 26 donors showed that after 6 hr the mean inhibition (+/- SE) of chemotaxis at 1:100 dilution was 26.4% +/- 3.3% (P less than .001 vs. medium-treated). It was found that the peptidoglycan fraction of the staphylococci was sufficient to induce production of inhibitor by the cooperative action of T cells and monocytes. The inhibitor is a protein with a molecular mass of 30-45 kilodaltons. It is not toxic to the neutrophils and does not affect secretion, adhesion, phagocytosis, or the ability to kill Staphylococcus aureus. This potent inhibitor of neutrophil chemotaxis may play a role in the modulation of neutrophil function during bacterial infections.

Cell Movement↗
PubMed1987

Colonization of skin and development of peritonitis due to coagulase-negative staphylococci in patients undergoing peritoneal dialysis.

Coagulase-negative staphylococci, part of the normal skin flora, frequently colonize bioprosthetic devices and are the most common cause of peritonitis in patients undergoing peritoneal dialysis. Using the API STAPH-IDENT system (Analytab Products, Plainview, New York) and plasmid pattern analysis, we investigated the importance of chronic carriage of coagulase-negative staphylococci in the development of peritonitis due to these organisms. During a nine-month period, 182 surveillance cultures of pericatheter skin and anterior nares from 30 patients yielded 102 strains of coagulase-negative staphylococci. Twelve of these patients had 20 episodes of peritonitis due to these organisms. Staphylococcus epidermidis accounted for 75% of surveillance and 79% of peritonitis-associated strains. By plasmid pattern analysis of 47 surveillance and 16 peritonitis-associated strains, only three patients carried identical coagulase-negative staphylococci on two or more occasions, and only three patients developed peritonitis due to organisms cultured previously from body surface sites.

Coagulase↗
PubMed1993

Distribution of genes encoding erythromycin ribosomal methylases and an erythromycin efflux pump in epidemiologically distinct groups of staphylococci.

Erythromycin-resistant staphylococci can be divided into two phenotypic classes based on their pattern of cross-resistance to other macrolides, lincosamides and type B streptogramins. Strains inducibly or constitutively resistant to all MLS antibiotics possess erythromycin ribosomal methylase (erm) genes, whereas strains inducibly resistant to only 14 and 15-membered ring macrolides and type B streptogramins harbour msrA, which encodes an ATP-dependent efflux pump. Dot-blot hybridization was used to study the distribution of ermA, ermB, ermC and msrA in five epidemiologically distinct groups of staphylococci. The most widely-distributed resistance determinant was ermC, which was detected in 112 (50.6%) of 221 isolates, alone in 106 isolates and in combination with a second erythromycin resistance determinant in six strains. MsrA was detected in 73 (33%) of isolates, alone in 65 and in combination with a methylase gene in eight strains. This determinant was responsible for erythromycin resistance in over one-third (36.4%) of clinical isolates of coagulase-negative staphylococci. ErmA and ermB were present in only a minority of isolates (5.9 and 7.2% of strains, respectively). The resistance determinants present in ten strains did not hybridize to any of the four probes although, in all cases, their resistance phenotype was consistent with the possession of a methylase gene. Interestingly, ermB was found exclusively in animal isolates of Staphylococcus intermedius, Staphylococcus xylosus and Staphylococcus hyicus, but not in coagulase-negative staphylococci of human origin. This determinant has previously only been found in a small number of epidemiologically related strains of Staphylococcus aureus.

Animals↗
PubMed2003

Multicentre surveillance of antimicrobial resistance in enterococci and staphylococci from Colombian hospitals, 2001-2002.

Invasive isolates of staphylococci and enterococci were collected from 15 tertiary care centres in five Colombian cities from 2001 to 2002. A total of 597 isolates were available for analysis. Identification was confirmed by both automated methods and multiplex PCR assays in a central laboratory. Staphylococcus aureus and coagulase-negative staphylococci (CoNS) corresponded to 49.6% and 29.6% of isolates, respectively, and 20.8% were identified as enterococci. MICs of ampicillin, ciprofloxacin, chloramphenicol, erythromycin, gentamicin, linezolid, oxacillin, rifampicin, teicoplanin, tetracycline, trimethoprim/sulfamethoxazole (SXT) and vancomycin were determined using an agar dilution method as appropriate. Screening for vancomycin-resistant S. aureus was also carried out on brain-heart infusion agar plates supplemented with vancomycin. The presence of mecA and van genes was investigated in methicillin-resistant staphylococci and glycopeptide-resistant enterococci (GRE), respectively. All staphylococci were susceptible to vancomycin, teicoplanin and linezolid. No VISA isolates were found. In S. aureus and CoNS, the lowest rates of resistance were found for SXT (7.4%) and chloramphenicol (10.7%), respectively. Resistance to oxacillin in S. aureus and CoNS was 52% and 73%, respectively. The mecA gene was detected in 97.5% of methicillin-resistant S. aureus isolates. In enterococci, resistance to glycopeptides was 9.7%: vanA (58.3%) and vanB (41.7%) genes were found. Pulsed-field gel electrophoresis indicated that the GRE isolates were closely related. Rates of resistance to ampicillin, ciprofloxacin, chloramphenicol, rifampicin and high levels of gentamicin and streptomycin were 9.7%, 27.4%, 8.9%, 43%, 17% and 28.2%, respectively. All enterococci were susceptible to linezolid.

Anti-Bacterial Agents↗
PubMed2004

Activity of dalbavancin against staphylococci and streptococci, assessed by BSAC and NCCLS agar dilution methods.

BACKGROUND: Dalbavancin is a long-half-life (9-12 days) glycopeptide, now in Phase 3 development. Its pharmacokinetics may facilitate home intravenous therapy, early discharge and long prophylaxis. METHODS: Dalbavancin and comparators were tested in vitro against staphylococci and streptococci to determine (i) activity and (ii) the comparability of agar dilution MICs by the BSAC and the NCCLS methods. The test panels comprised 92-93 isolates each of Staphylococcus aureus, coagulase-negative staphylococci (CoNS) and 'viridans' streptococci, chosen for epidemiological diversity and to over-represent strains resistant to conventional agents, including teicoplanin. RESULTS: Dalbavancin MICs by the BSAC and NCCLS methods generally were identical, or else those by the BSAC method were two-fold lower. In both cases the MIC distributions of dalbavancin within species groups were unimodal, with peaks at 0.25, 0.12/0.25 and 0.12 mg/L for S. aureus, CoNS and viridans streptococci, respectively. MIC differences between the BSAC and NCCLS methods were similarly small for other glycopeptides and, generally, non-glycopeptides. Dalbavancin MICs were mostly two- to 16-fold below those of vancomycin and dalbavancin-like vancomycin-remained highly active against teicoplanin-non-susceptible staphylococci. CONCLUSIONS: Dalbavancin has good activity versus streptococci and staphylococci, including teicoplanin-resistant strains. MICs by BSAC and NCCLS agar dilution methods were comparable to each other; slightly lower MIC values, nevertheless, have been recorded by broth microdilution.

Anti-Bacterial Agents↗
PubMed1999

Oral carriage of staphylococci in patients with rheumatoid arthritis.

OBJECTIVE: To determine the prevalence of oral staphylococcal carriage in patients with rheumatoid arthritis compared with healthy controls. METHODS: Fifty healthy adults, 25 healthy elderly volunteers and 25 patients with rheumatoid arthritis were studied. An oral rinse, tongue swab and nasal swab were collected for culture on blood agar and a range of selective agars. Isolates of staphylococci were identified and antibiotic sensitivity profiles determined by standard methods. RESULTS: Staphylococci were isolated from the mouths of 94% of the healthy adults, 24% of whom carried Staphylococcus aureus. All the healthy elderly carried oral staphylococci and 36% were colonized with S. aureus. Staphylococci were isolated from 96% of the rheumatoid arthritis patients and this group had the highest carriage rate of S. aureus (56%), significantly higher than the healthy adults (P < 0.05). In all three groups, Staphylococcus epidermidis was isolated from the mouths of > 80%. No methicillin-resistant strains of S. aureus were isolated. CONCLUSION: Oral carriage of S. aureus appears to be common in patients with rheumatoid arthritis and studies of the mouth as a source of infection in septic arthritis would be merited.

Adolescent↗