Clinical Blood Culture Research Articles

Enhancement of the effects of anti-staphylococcal antibiotics by aminoglycosides.

The in vitro activity of seven anti-staphylococcal antibiotics alone and in combination with four aminoglycoside antibiotics against 35 clinical isolates of Staphylococcus aureus from blood cultures of patients with endocarditis or septicemia was studied. The combination of nafcillin-gentamicin or nafcillin-tobramycin when compared with nafcillin alone killed significantly more S. aureus at 6 h for 33 of 35 isolates. A significant decrease in viable colony-forming units at 24 and 48 h was demonstrated for a smaller number of isolates. Using the agar dilution antibiotic susceptibility test, significant enhancement of activity was demonstrated against almost all isolates when cephalothin, cefazolin, or clindamycin was combined with gentamicin, tobramycin, or kanamycin. The combination of nafcillin or vancomycin with gentamicin, tobramycin, or kanamycin also showed enhanced activity against the majority of isolates. Oxacillin or methicillin when combined with the aminoglycosides showed enhancement of activity against the least number of isolates. Streptomycin was the least effective of the four aminoglycoside antibiotics studied.

Evaluation of Four Blood Culture Systems Using Parallel Culture Methods

Commercially prepared Vacutainer thioglycolate broth with SPS (TBSPS), the B-D Vacutainer culture tube with SPS (VCT), the Pfizer E-Vac hypertonic brucella broth with SPS (BBSPS), and our own Trypticase-soy hypertonic broth with SPS (TSBH) were studied by parallel culture methods for their ability to allow the survival of a wide spectrum of organisms, their ability to allow recovery of organisms, and the time required to obtain a recovery from clinical blood cultures. Organisms considered to be clinically significant were recovered from 176 blood cultures. The TSBH system produced all 176 recoveries, the BBSPS system allowed for 170 recoveries, the TBSPS recovered 131, and the VCT accounted for 106 recoveries. The time required to recover any given organism from both the BBSPS and the TSBH systems did not exceed 48 h, whereas 86 of the 131 recoveries from the TBSPS system required more than 72 h and 74 of the 106 VCT recoveries also required more than 72 h. A wide spectrum of organisms were recovered from both the BBSPS and the TSBH systems. The TBSPS system failed to allow the recovery of many streptococci and Pseudomonas spp. and the VCT system failed to recover many organisms.

Comparison of Macroscopic, Microscopic, and Radiometric Examinations of Clinical Blood Cultures in Hypertonic Media

Clinical blood cultures were collected in the Bactec 8A flask (Johnston Laboratories, Cockeysville, Md.) and examined macrosopically, microscopically, and radiometrically in an effort to determine which approach produced the fastest detection time. Of 360 blood cultures found to contain organisms by subculture, 334 were first detected by Bactec, 98 by macroscopic examination, and 68 by microscopic examination. Examination times were at 4, 8, 16, 24, 36, and 48 h after collection of the specimen. Sixteen hours after specimen collection, microscopic examination had detected 31 positive cultures, macroscopic examination had detected two positive cultures, and Bactec had detected 160 positive cultures. By the end of the first 24 h of incubation, Bactec had detected 313 (93%) of those cultures eventually found to be positive. Although Bactec produced the fastest detection time in an overwhelming majority of the cultures, it failed to detect three of three Candida spp. cultures, three of five Bacteroides spp. cultures, and six of 32 Enterococcus spp. cultures during the first 48 h of incubation.

Clinical evaluation of sodium amylosulfate in human blood cultures.

Sodium amylosulfate was shown to be a useful anticoagulant additive for increased isolation of bacteria from clinical blood cultures.

Clinical Evaluation of Sodium Amylosulfate in Human Blood Cultures

Sodium amylosulfate was shown to be a useful anticoagulant additive for increased isolation of bacteria from clinical blood cultures.

In vitro studies on the isolation of genital mycoplasmas from blood.

A method is described for the isolation of genital mycoplasmas from clinical blood cultures.

In Vitro Studies on the Isolation of Genital Mycoplasmas from Blood

A method is described for the isolation of genital mycoplasmas from clinical blood cultures.

New medium for blood cultures.

A new medium suitable for blood cultures is described. It contains dextrose, cysteine, iron, and magnesium, in a tris(hydroxymethyl)aminomethane buffer, and a mixture of peptones derived from animal tissues, casein, and yeast. In comparison with Trypticase Soy Broth, the growth rate constants of Staphylococcus aureus, Streptococcus (Viridans group), enterococcus, and Escherichia coli were higher in this medium, and growth appeared earlier in a significant number of clinical blood cultures.

New Medium for Blood Cultures

A new medium suitable for blood cultures is described. It contains dextrose, cysteine, iron, and magnesium, in a tris(hydroxymethyl)aminomethane buffer, and a mixture of peptones derived from animal tissues, casein, and yeast. In comparison with Trypticase Soy Broth, the growth rate constants of Staphylococcus aureus, Streptococcus (Viridans group), enterococcus, and Escherichia coli were higher in this medium, and growth appeared earlier in a significant number of clinical blood cultures.

Endocarditis Due to Serratia Marcescens

THREE cases of bacterial endocarditis produced by Serratia marcescens have been reported.1 2 3 This paper describes an additional case. Case Report M.R., a 59-year-old woman, was transferred to the New York Hospital because of bacteremia of 1 month's duration. Two months before transfer, many teeth had been extracted. One month later she was admitted to another hospital because of fever (temperature of 104°F.) and shaking chills. S. marcescens was isolated from 4 blood cultures, and she was treated with penicillin, streptomycin and chloramphenicol. During 1 month of therapy there was no clinical response and blood cultures remained positive for S. marcescens . . .

Escherichia coli endocarditis; report of a case presenting a difficult problem in chemotherapy.

WELL-AUTHENTICATED instances of endocarditis due to Escherichia coli are uncommon, only 14 such cases having been reported. 1 All these cases have met the logical criteria suggested by Harries and Burtenshaw 1e and by Hoffman and associates, 1i namely: (1) positive blood cultures obtained during the life of a patient with a compatible clinical picture and (2) demonstration of the organism in the cardiac valves at necropsy. Two additional patients with this condition have been reported on, both of whom recovered after streptomycin therapy. 2 For these patients the diagnosis was made on the basis of clinical evidence plus positive blood cultures. Recoveries following other types of antibiotic therapy have not been recorded. It seems reasonable that, with newer antibiotic agents, more successful results will be reported in the future. In these circumstances, cases satisfying the first criterion would have to be accepted as proved. Microscopic examination of the heart valves in successfully treated

The significance of positive blood culturesin newborn infants

I T IS not uncommon nursery experience to observe certain newborn infants who regularly lose weight beyond the usual expected time and who exhibit a lack of interest in nursing regardless of type of feeding. More often than not careful examination reveals no very convincing reason for the anorexia, listlessness, and accompanying weight loss. If allowed to go unchecked, loss of weight may be very considerable, and energetic and supportive t reatment becomes imperative. The writers observed a suggested relationship between this clinical picture and blood cultures which were quite regularly positive for hemolytic staphylococci. In August, 1946, a study was begun for the purpose of clarifying this clinical impression. This report is concerned with 323 blood culture samples taken from 240 infants, some of whom presented with surprising' regularity the above clinical picture. In others the nursery course was uneventful. The number of blood cultures and the number of infants included in this study would seem to be significant. In a partial review of the literature we find scant reference to bacteremia in the newborn infant. Older references to sepsis of the newborn infant are in most instances confusing and lacking in adequate blood studies. Usually these older reports described a severe type of illness, with death the usual rule, characterized by fever, severe gastrointestinal disturbance, jaundice, hemorrhage, and serious lesions noted at autopsy in the various body systems. The most informative study and the one most regularly referred to is that of Dunham. 1 She reported the findings in thirty-nine eases of septicemia of the newborn infant collected from the records of the New Haven Hospital and occurring over a period of five years. In thirty-four of her eases the diagnosis was made from blood cultures taken before death. She fur ther recorded the findings in 115 blood cultures taken at random from forty-nine apparently healthy newborn infants. Staphylococcus albus was recovered in thirty-five instances from these apparently well infants. Dunham concluded tha t Staph. albus, since it could regularly be cultured from the skin of newborn infants, should not be considered as a cause of illness but rather as a skin contaminant when present in blood cultures in the neonatM period. This conclusion has been generally accepted as a fact'. The data recorded in this study suggest that hemolytic Staph. albus is capable of invading, the blood stream of newborn infants with surprising regularity, and, if present in sufficient nmnbers, may cause regular and marked weight loss and at times serious signs of illness.