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PubMed2006

Comparison of two commercial methods with PCR restriction fragment length polymorphism of the tuf gene in the identification of coagulase-negative staphylococci.

AIMS: Two commercial methods for the identification of coagulase-negative staphylococci (CNS) were compared with the restriction fragment length polymorphism (RFLP) of the amplified tuf gene, which served as the reference method. METHODS AND RESULTS: One hundred and forty-five CNS were evaluated using the API 32 Staph ID and the Crystal GP/ID BBL systems. The PCR-RFLP of the tuf gene served as the reference method. The APIStaph and the GP/ID BBL had an overall rate of agreement with the molecular method of 58.6% and 46.2% respectively, with the inability of the GP/ID BBL to characterize 11.7% of the isolates. The APIStaph showed higher sensitivity and better agreement than the GP/ID BBL with the PCR-RFLP, except for Staphylococcus hominis and Staphylococcus capitis. CONCLUSIONS: Neither of the commercial systems was as reliable as the PCR-RFLP method for identifying isolates of CNS. Overall the APIStaph had better agreement with the PCR-RFLP than the GP/ID system. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicate that the PCR-RFLP method is more reliable than the two commercial systems tested, suggesting that it is more reliable for routinely identifying CNS.

Bacterial Typing Techniques↗

PubMed1986

In vitro susceptibilities of four species of coagulase-negative staphylococci.

The in vitro susceptibilities of 260 strains of coagulase-negative staphylococci to penicillin G, oxacillin, nafcillin, methicillin, cephalothin, and seven non-beta-lactam antimicrobial agents were determined and compared with the susceptibilities of 54 strains of Staphylococcus aureus with known patterns of susceptibility. Penicillin G susceptibility for S. aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus hominis was readily determined by using beta-lactamase tests with induced cells and with a standardized microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to the coagulase-negative species. Percentages of organisms susceptible were as follows: S. epidermidis, 7%; S. haemolyticus, 5%; and S. hominis, 47%. Oxacillin susceptibility for these four species was readily determined by using a modification of the microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to S. haemolyticus and S. hominis, but alternate criteria were necessary for S. epidermidis. Percentages of organisms susceptible were as follows: S. epidermidis, 29%; S. haemolyticus, 36%; and S. hominis, 97%. Staphylococcus saprophyticus differed from the other staphylococcal species; all strains were beta-lactamase negative and were penicillin susceptible but had higher penicillin G MICs than did susceptible strains of the other species. There was total cross resistance among the penicillinase-resistant penicillins and cephalothin for the coagulase-negative staphylococci as well as for S. aureus; oxacillin MICs were more reliable than MICs of the other drugs or a standardized disk diffusion test for distinguishing resistant from susceptible strains. Vancomycin, rifampin, and ciprofloxacin were consistently active against all staphylococci. Erythromycin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole were more active against oxacillin-susceptible staphylococci than against oxacillin-resistant staphylococci.

Anti-Bacterial Agents↗

PubMed1987

In vitro antistaphylococcal activity of pefloxacin alone and in combination with other antistaphylococcal drugs.

MICs of pefloxacin and nine antistaphylococcal drugs were determined for 200 isolates of Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, and Staphylococcus saprophyticus. All the strains were susceptible to pefloxacin, vancomycin, and rifampin. Oxacillin-resistant strains were uniformly resistant to cephalothin and were more likely to be resistant to gentamicin, erythromycin, clindamycin, doxycycline, and trimethoprim-sulfamethoxazole than were oxacillin-susceptible strains. Time-kill studies with 23 strains of S. aureus, S. epidermidis, and S. haemolyticus indicated that the relative order of bactericidal activities was gentamicin greater than or equal to pefloxacin greater than oxacillin greater than vancomycin greater than rifampin. Pefloxacin combined with oxacillin or vancomycin killed staphylococci more rapidly than oxacillin or vancomycin alone but less rapidly than pefloxacin alone. Gentamicin combined with oxacillin, vancomycin, or pefloxacin resulted in the most rapid killing of gentamicin-susceptible strains. Rifampin combined with oxacillin, vancomycin, or pefloxacin reduced the bactericidal activities of those drugs, but rifampin resistance was not observed as it was with rifampin alone. Pefloxacin is a potentially useful antistaphylococcal agent.

Anti-Bacterial Agents↗

PubMed1984

Comparison of various methods for differentiation of staphylococci and micrococci.

A modified oxidase test (Remel, Lenexa, Kans.) and susceptibility to furazolidone and lysostaphin (Remel) were evaluated in conjunction with the Staph-Ident strip (Analytab Products, Plainview, N.Y.) to accurately differentiate between staphylococci and micrococci. A total of 414 clinical isolates of catalase-positive, gram-positive cocci were each tested with the Staph-Ident strip and by glucose fermentation, acid production from glycerol, susceptibility to furazolidone and lysostaphin, and the oxidase test. Based on the reference methods of glucose fermentation and acid production from glycerol, 396 (95.6%) of the organisms were classified as Staphylococcus species and 18 (4.4%) were classified as Micrococcus species. Of the staphylococci, 99% were oxidase negative and susceptible to furazolidone; 82% were susceptible to lysostaphin. All of the micrococci were oxidase-positive and resistant to furazolidone and lysostaphin. Of the staphylococci, 99% were identified to species by the Staph-Ident strip. However, six (33%) of the micrococci were incorrectly identified as Staphylococcus species (three each of Staphylococcus hominis and Staphylococcus saprophyticus). Because of the demonstrated sensitivity and specificity of the oxidase and furazolidone susceptibility tests, it is suggested that either of these methods be used in the clinical laboratory to accurately differentiate between staphylococci and micrococci. It is also suggested that when working with the Staph-Ident strip, additional testing such as furazolidone susceptibility or oxidase activity should be performed to provide increased accuracy in the differentiation and characterization of members of the family Micrococcaceae.

Bacteriological Techniques↗

PubMed1987

Synergistic hemolysis associated with coagulase-negative staphylococci isolated from bovine mammary glands.

A total of 353 coagulase-negative staphylococcus (CNS) isolates from infected bovine mammary glands were tested for cytolysin production by using the synergistic hemolysin assay (SHA). Overall, 34.6% of CNS isolates were SHA positive. Human-associated, coagulase-negative staphylococcal species contained the greatest number of SHA-positive strains. Milk leukocyte levels expressed as somatic cell counts (SCC) were elevated with SHA-positive Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus warneri strains. Elevated SCC levels were associated with strains of Staphylococcus hyicus and Staphylococcus chromogenes. However, no difference in SCC levels was observed between SHA-positive and SHA-negative strains. Results indicated that the SHA was a sensitive test for the detection of cytolysin-producing CNS.

Animals↗

PubMed2000

Glyceraldehyde-3-phosphate dehydrogenase-encoding gene as a useful taxonomic tool for Staphylococcus spp.

The gap gene of Staphylococcus aureus, encoding glyceraldehyde-3-phosphate dehydrogenase, was used as a target to amplify a 933-bp DNA fragment by PCR with a pair of primers 26 and 25 nucleotides in length. PCR products, detected by agarose gel electrophoresis, were also amplified from 12 Staphylococcus spp. analyzed previously. Hybridization with an internal 279-bp DNA fragment probe was positive in all PCR-positive samples. No PCR products were amplified when other gram-positive and gram-negative bacterial genera were analyzed using the same pair of primers. AluI digestion of PCR-generated products gave 12 different restriction fragment length polymorphism (RFLP) patterns, one for each species analyzed. However, we could detect two intraspecies RFLP patterns in Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus simulans which were different from the other species. An identical RFLP pattern was observed for 112 S. aureus isolates from humans, cows, and sheep. The sensitivity of the PCR assays was very high, with a detection limit for S. aureus cells of 20 CFU when cells were suspended in saline. PCR amplification of the gap gene has the potential for rapid identification of at least 12 species belonging to the genus Staphylococcus, as it is highly specific.

Glyceraldehyde-3-Phosphate Dehydrogenases↗

PubMed2005

Widespread distribution of disinfectant resistance genes among staphylococci of bovine and caprine origin in Norway.

We demonstrate here a widespread distribution of genes mediating efflux-based resistance to quaternary ammonium compounds (QACs) in staphylococci from unpasteurized milk from 127 dairy cattle herds and 70 dairy goat herds. QAC resistance genes were identified in 21% of the cattle herds (qacA/B, smr, qacG, and qacJ) and in 10% of the goat herds (qacA/B and smr). Further examination of 42 QAC-resistant bovine and caprine isolates revealed the following genes: qacA/B (12 isolates) was present in four different species of coagulase-negative staphylococci (CoNS), smr (27 isolates) was detected in eight different CoNS species and in Staphylococcus aureus on a previously reported plasmid (pNVH99), qacG (two isolates) was detected on two plasmids (pST94-like) in Staphylococcus cohnii and Staphylococcus warneri, and qacJ (two isolates) was found in Staphylococcus hominis and Staphylococcus delphini on a plasmid (pNVH01) previously found in equine staphylococci. Isolation of indistinguishable pulsed-field gel electrophoresis (PFGE) CoNS types from tank milk and mammary quarter milk samples in a dairy cattle herd suggested that these QAC-resistant staphylococci were of intramammary origin. Indistinguishable or closely related PFGE types of bovine QAC-resistant CoNS were observed in different herds. One particular bovine S. warneri PFGE type was isolated repeatedly from samples collected during a 30-month period in a herd, showing long-term persistence. In conclusion, it seems that the widespread distribution of staphylococci carrying QAC resistance genes in Norwegian dairy cattle and goat herds is the result of both the intra- and interspecies spread of QAC resistance plasmids and the clonal spread of QAC-resistant strains.

Animals↗

PubMed1998

[Bacterial strains isolated from neutropenic patients and their resistance to antibiotics].

BACKGROUND: Although Gram negative as well as Gram positive bacteria participate in febrile episodes of neutropenic patients, in particular recently the ratio of Gram positive bacteria is increasing. The objective of the present work was to investigate the incidence and antibiotic resistance of pathogenic bacterial agents in neutropenic patients. METHODS AND RESULTS: The presence of bacteria was investigated in 446 neutropenic patients hospitalized at the Haematological Clinic in 1995. Haemocultures (apparatus Bact/Alert 120, cultivation media Organon-Teknika) and urine were examined. The sensitivity for antibiotics was tested by the standard dilution micromethod. In blood most frequently Staphylococcus epidermidis was isolated (45.4%), coagulase-negative strains of Staphylococcus haemolyticus, Staphylococcus hominis and Staphylococcus saprophyticus (14.4%), Acinetobacter calcoaceticus-baumannii (complex 6.3%) and Pseudomonas aeruginosa (6.3%). In urine the following were detected: Staphylococcus epidermidis (36.5%), Enterococcus sp. (14.5%), Escherichia coli (13.1%), Enterococcus faecalis (11.6%) and Enterococcus solitarius (6.5%). In all strains resistance to antibiotics and chemotherapeutic drugs was assessed. CONCLUSIONS: Investigation of the frequency of different bacterial species, along with monitoring of the resistance is an essential prerequisite of initial antibiotic therapy of febrile episodes in neutropenic patients.

Bacteria↗

PubMed1998

An inexpensive and reliable method for routine identification of staphylococcal species.

The aim of this study was to develop a simple, reliable, and inexpensive in-house system for routine species identification of staphylococci in clinical practice. The system combines 15 key tests (including carbohydrate fermentation) performed in micro-well strips and antimicrobial disk diffusion susceptibility tests performed on standardised paper disk method antibiotic sensitivity medium agar. Twenty-eight staphylococcal reference strains belonging to 18 different species were correctly identified using this in-house system. A total of 291 clinical staphylococci isolates were evaluated with the in-house system and a conventional identification scheme. The in-house system identified 281 (96.6%) of these 291 isolates. Eleven different species were recognised. The five species most frequently identified were Staphylococcus epidermidis (48.6%), Staphylococcus aureus (27.8%), Staphylococcus haemolyticus (8.2%), Staphylococcus hominis (5.7%), and Staphylococcus warneri (5.3%). There was an agreement of 86.3% between the species identification obtained with the in-house system and the conventional identification scheme. All coagulase-negative isolates initially identified as species other than Staphylococcus epidermidis as well as indistinctly identified isolates were also evaluated with a commercial identification system. The agreement between species identification obtained with the in-house system and the commercial system for 101 identified isolates was 73%. Several isolates that were difficult to distinguish with the conventional scheme and/or the commercial system were identified with the aid of the antimicrobial susceptibility test included in the in-house system. The described test scheme should be of value for identification of clinically significant staphylococci species.

Agar↗

PubMed2006

DNA fingerprinting of a multi-resistant coagulase-negative staphylococci isolated from biomaterials in dialysis services.

BACKGROUND: Coagulase-negative staphylococci (CoNS) have emerged as an important opportunistic pathogen isolated in hospital. Several species of CoNS have been implicated in human infections and disease especially in patients with poor health status. METHODS: A total of 71 clinical strains of CoNS were isolated from dialysis fluid and needles in a dialysis unit and characterized. Susceptibility to antibiotics, biofilm production and molecular typing by pulsed-field gel electrophoresis (PFGE) were achieved. RESULTS: The main isolated CoNS strains were Staphylococcus epidermidis (45%), Staphylococcus hominis (14%) and Staphylococcus haemolyticus (12.7%). The susceptibility profile of all strains revealed high resistance level to penicillin and oxacillin. PCR detection of oxacillin resistance gene (mecA gene) revealed a higher percentage of positive strains than the classic test (ATB Staph). Slime production test was positive in 60.6% of CoNS strains. PFGE analysis showed the presence of 69 restriction profiles clustered in 56 patterns. CONCLUSIONS: Profiles of all isolates were generally heterogeneous, suggesting independent circulation with some evidence of cross-transmission.

Biocompatible Materials↗

PubMed2006

Study of the efficacy of Coated VICRYL Plus Antibacterial suture (coated Polyglactin 910 suture with Triclosan) in two animal models of general surgery.

OBJECTIVES: To evaluate the efficacy in vitro and in vivo of a new antibacterial suture (PGAB) compared with a traditional braided suture (PG). Our primary goals were to study microbiological effectiveness and impact on wound healing of PGAB vs PG. Secondary goal was to analyze influence on inflammatory response. METHODS: In vitro study: clinical samples of Staphylococcus epidermidis, Staphylococcus aureus, S. hominis, Staphylococcus haemolyticus, Staphylococcus auricularis, Enterococcus faecalis, Corynebacterium spp. and Escherichia coli were studied. We also implanted a flat mesh in 10 minipigs, four incisions each (two PG and two PGAB) two contaminated with S. epidermidis and two not contaminated. Finally, we performed four colic anastomosis in each of 10 minipigs, two contaminated with E. coli and two not contaminated (two PG and two PGAB). We studied the inflammatory and wound healing processes in both models. RESULTS: We observed a bactericidal efficacy of PGAB against grampositive, and bacteriostatic effect against E. coli. Mesh study: recovered CFU were lower in the group PGAB vs PG. In the group PGAB, inflammatory mediators' concentrations were lower. In the group PGAB, concentrations of wound healing mediators were normal. Colic anastomosis: recovered CFU were lower in the group PGAB vs the group PG. In the group PGAB we observed a reduction of inflammatory mediators. In the group PGAB we observed normalized concentrations of wound healing mediators. CONCLUSIONS: This study demonstrates microbiological efficacy of PGAB, that normalizes wound healing process, and an anti-inflammatory effect.

Anastomosis, Surgical↗

PubMed1980

Classification and characteristics of coagulase-negative, methicillin-resistant staphylococci.

Sixty-five clinical isolates of coagulase-negative, methicillin-resistant staphylococci have been classified as Staphylococcus epidermidis (63.0%), "phosphatase-negative S. epidermidis" (12.3%), coagulase-negative Staphylococcus aureus (6.2%), Staphylococcus hemolyticus (6.2%), Staphylococcus hominis (3.1%), and Staphylococcus warneri (1.5%). Five of the organisms (7.7%) could not be classified with certainty as currently recognized species. Novobiocin resistance was encountered in eight of the strains, but these were not classified as the accepted novobiocin-resistant staphylococcal species. Some differences in antibiotic resistance patterns to those typical of methicillin-resistant S. aureus were noted in that, although 29 strains were resistant to methicillin, penicillin, sulfamethizole, streptomycin, and tetracycline, the remainder of the strains were sensitive to streptomycin or tetracycline or both. In a majority of the strains (42 of 65), methicillin susceptibility testing by the disk method at 30 or at 37 degrees C in the presence of NaCl did not appear to enhance resistance expression. Most of the strains produced beta-lactamase (EC 3.5.2.6), but none of the 21 strains tested produced enterotoxin B.

Anti-Bacterial Agents↗

PubMed1995

Four-year prospective study of STAPH-IDENT system and conventional method for reference identification of Staphylococcus, Stomatococcus, and Micrococcus spp..

A 4-year prospective study compared the accuracy of the STAPH-IDENT system (bioMérieux Vitek, Inc., Hazelwood, Mo.) with that of the reference procedure of the Centers for Disease Control and Prevention for the identification of Staphylococcus species, Stomatococcus mucilaginosus, and Micrococcus species. The study compared the results from 1,106 cultures (500 eye cultures, 217 strains submitted for reference identification, and 389 known stock strains) representing 21 species of the family Micrococcaceae. The overall agreement of genus and species identifications was 81.1%. The percent agreement for the five most common clinical isolates was as follows: Staphylococcus epidermidis, 97.1% (517 isolates); Staphylococcus hominis, 82.5% (57 isolates); Staphylococcus aureus, 77.2% (162 isolates); Staphylococcus haemolyticus, 75.8% (61 isolates); and Staphylococcus warneri, 64.1% (39 isolates). The lowest percent agreement was with Staphylococcus cohnii (11.1%; (9 isolates). Of the 217 isolates sent to the Centers for Disease Control and Prevention for identification, 60.4% (131) were correctly identified by the STAPH-IDENT system. Of these, S. epidermidis accounted for 23.9%, S. aureus accounted for 15.6%, S. warneri accounted for 6.9%, Staphylococcus lugdunensis accounted for 6.5%, S. haemolyticus accounted for 5.5%, and S. hominis accounted for 4.1%. The STAPH-IDENT system did not perform adequately when dealing with commonly encountered organisms and is unsuitable for identifying uncommon isolates.

Bacterial Typing Techniques↗

PubMed1994

Distribution of coagulase-negative staphylococci, including the newly described species Staphylococcus schleiferi, in nosocomial and community acquired urinary tract infections.

Four hundred and four coagulase-negative staphylococci were isolated from 4905 urine specimens obtained from 4192 inpatients and outpatients. The distribution of the strains was as follows: 193 Staphylococcus epidermidis (47.8%), 171 Staphylococcus saprophyticus (42.3%), 29 Staphylococcus haemolyticus (7.2%), 5 Staphylococcus warneri (1.2%), 3 Staphylococcus schleiferi (0.7%), 2 Staphylococcus hominis (0.5%) and 1 Staphylococcus simulans (0.2%). All three Staphylococcus schleiferi strains were isolated from inpatients: a 64-year-old female, a 68-year-old male and a 3-month-old male with colony counts of 468,000 cfu/ml, 324,000 cfu/ml and 764,000 cfu/ml respectively. These findings show that among coagulase-negative staphylococci, Staphylococcus schleiferi, a newly described species of coagulase-negative staphylococci not previously reported as a uropathogen, may also cause hospital acquired urinary tract infection.

Aged↗

PubMed1983

Characterization of coagulase-negative staphylococci from urinary tract specimens.

Species of coagulase-negative staphylococci isolated from urine specimens submitted from both inpatients and outpatients to the clinical microbiology laboratory of a teaching hospital were identified with a biotyping system, with species then correlated by clinical features and antimicrobial susceptibility. Of 145 isolates, 102 (70%) were Staphylococcus epidermidis, 24 (17%) were Staphylococcus saprophyticus, 7 (4.7%) were Staphylococcus haemolyticus, 4 (2.8%) were Staphylococcus hominis, 3 (2.1%) were Staphylococcus simulans, and 5 (3.4%) were other species. Features characterizing persons with bacteriuria with S. saprophyticus compared with bacteriuria with any other species included female sex (95% versus 52%), young age (median age, 22 years versus 61 years), ambulatory status (hospital outpatients, 86% versus 23%), and absence of indwelling catheters (4.5% versus 49%). All other coagulase-negative staphylococci were isolated in a setting suggesting nosocomial acquisition, were more frequently resistant to common antimicrobial agents (42% multiply resistant versus 4.2% of S. saprophyticus), and were not distinguished by clinical features. Novobiocin susceptibility, with a sensitivity of 100% and specificity of 96%, provided a simple and reliable test for differentiation of S. saprophyticus from other coagulase-negative staphylococci and should be routinely used for urinary tract specimens in the clinical laboratory.

Anti-Bacterial Agents↗

PubMed2004

icaA is not a useful diagnostic marker for prosthetic joint infection.

A collection of 99 staphylococcal isolates associated with prosthetic joint infection and 23 coagulase-negative staphylococci isolated from noninfected arthroplasty-associated specimens were screened in order to determine whether the presence of icaA could be used to distinguish between pathogens and nonpathogens. All Staphylococcus aureus prosthetic joint infection isolates (n = 55) were icaA positive. A total of 46% (20 out of 44) of coagulase-negative staphylococcal prosthetic joint infection isolates were icaA positive, and 30% (7 out of 23) of arthroplasty-associated non-prosthetic joint infection-associated coagulase-negative staphylococcal isolates were icaA positive (P = 0.23). Certain coagulase-negative Staphylococcus species appeared more likely to be isolated as either arthroplasty-associated non-prosthetic joint infection-associated isolates (e.g., Staphylococcus warneri and Staphylococcus hominis) or pathogens (e.g., Staphylococcus lugdunensis). The presence of icaA in a coagulase-negative staphylococcal isolate associated with an arthroplasty is not a useful diagnostic indicator of pathogenicity.

Arthroplasty↗

PubMed1979

[Staphylococcus aureus variety hominis in a cattle herd].

A site-linked hominis variety of Staphylococcus aureus was isolated from a cattle herd. The find coincided with accumulated occurrence of clinical mastitis in cows and the affliction of one milker with a nose furuncle. The origin of the strain was not elucidated. The same strain had been isolated throughout three years of observation from clinical and subclinical mastitis as well as from chronic udder affection of cows, but no extraordinary accumulation of clinically manifest mastitis had been observed. The hominis site variety was quite rare among Staphylococcus aureus strains isolated from other cow herds. Enterotoxin formation was recorded from strains of the hominis site variety and from strains which could not be coordinated with any other of the known site varieties and fell under crystal-violet Type A. No enterotoxin formation was recordable from the strains of the bovis variety. The same applied to the group of staphylococci of crystal-violet Type C which could not be coordinated either with any known site variety and which is assumed to have originated from the hominis site variety. The above findings do not support any conclusion as to whether the cows had been infected by the milker or vice versa.

Animals↗

PubMed1995

Antistaphylococcal activity of cefdinir, a new oral third-generation cephalosporin, alone and in combination with other antibiotics, at supra- and sub-MIC levels.

Cefdinir is one of the few oral third generation cephalosporins that shows useful activity against nosocomial Gram-positive pathogens. For this reason the anti-staphylococcal potency of the new drug, alone or in combination with other drugs was further characterized. Against penicillin-resistant, oxacillin-susceptible Staphylococcus isolates, cefdinir demonstrated useful in-vitro activity. MIC90 values (in mg/L) were 0.25 for Staphylococcus aureus (30 strains), 0.06 for Staphylococcus epidermidis (24), 0.125 for Staphylococcus hominis (10), 0.5 for both Staphylococcus xylosus (15) and Staphylococcus capitis (11) and 4 for Staphylococcus saprophyticus (10), while Staphylococcus haemolyticus (12) was less susceptible with a MIC90 value of 32. Cefdinir activity was not adversely affected by several variables such as pH, inoculum size or the presence of serum or urine. The new cephem induced a PAE on all isolates studied: with S. aureus the extent of regrowth suppression ranged from 0.8 to 1 h, and with the other species from 0.5 (S. epidermidis) to 4.1 h (S. haemolyticus). Development of resistant strains was rare. At the highest level used (10 x MIC) mutants arose with a frequency of 6 x 10(-8) with S. haemolyticus and 2 x 10(-9) with S. epidermidis. The absence of a paradoxical effect of increasing concentrations of cefdinir on its bactericidal activity was confirmed up to a value of 500-fold the MICs. When cefdinir activity was assessed in association with ciprofloxacin, netilmicin, clarithromycin, fosfomycin, rifampicin, teicoplanin and vancomycin using the chequerboard and time-kill techniques, indifference predominated with all strains and in all combinations. Synergism was detected only in 11 out of a total of 175 tests performed by the chequerboard method. Using the time-kill technique cefdinir reacted synergically in 25 of 126 tests. Antagonism was never observed. S. aureus exposed to sub-inhibitory concentrations of cefdinir failed to grow on mannitol-salt agar and to produce haemolysins, but retained coagulase activity. Penicillinase production was also lost in about 17% of the survivors. Hydrophobicity changes were detected in all species tested with the exception of S. saprophyticus.

Anti-Bacterial Agents↗