The effect of penicillin on bacterial interference in vivo

The study was designed to analyse the effect of penicillin on interference between alfa-streptococci and group A streptococci in vivo. Tissue cages were implanted subcutaneously in 9 rabbits and inoculated with 10(5) cfu of alfa- and beta-streptococci together as well as separately. Both streptococci were recovered 96 h after the inoculation in the untreated rabbits. Alfa-streptococci inhibiting the growth of beta-streptococci in vitro retained this capacity under the experimental in vivo conditions. Higher penicillin concentration did not increase the killing rate of beta-streptococci grown separately while a faster killing was observed with low penicillin levels in the presence of inhibiting alfa-streptococci, indicating synergistic effect.     

Factors causing the clumping reaction of streptococcal strains with human plasma.

Fresh isolates of 204 strains of Streptococcus haemolyticus, 75 strains of viridans group Streptococcus, and 45 strains of Streptococcus pneumoniae were studied for their clumping reactions with human plasma. The plasma and serum factors that clumped the streptococcal strains were compared with those that clumped a Staphylococcus aureus strain. One hundred eleven strains of S. haemolyticus, 10 strains of viridans group Streptococcus, and none of the strains of S. pneumoniae tested were clumped by human plasma. However, clumping activity was remarkably unstable after subculturing on plates containing Todd-Hewitt blood agar. The strain with the highest level of activity was clumped by fibrinogen and normal human serum. Results of tests of the clumping reactions of staphylococci and streptococci with human serum indicated that the serum factors responsible for those reactions may be identical.     

A novel mechanism of resistance to penicillin-gentamicin synergism in Streptococcus faecalis

A patient with enterococcal endocarditis, who relapsed after repeated courses of apparently adequate treatment with ampicillin plus gentamicin, was subsequently cured with ampicillin-tobramycin therapy. The organisms isolated from this patient were strains of Streptococcus faecalis that were resistant to penicillin (or ampicillin)-gentamicin synergism but not to penicillin (or ampicillin)-tobramycin synergism. The mechanism of resistance in these strains appears to be related to a specific defect in the intracellular uptake of gentamicin (but not tobramycin) in the presence of penicillin.     

Evolution, incidence, and susceptibility of bacterial bloodstream isolates from 519 bone marrow transplant patients.

Bacteria remain an important cause of infection in bone marrow transplants. To examine shifts in the etiology and susceptibility of bacterial isolates from transplants, we reviewed the incidence and susceptibility of blood isolates during a 7-year period. The infection rate fell dramatically during this time. Gram-positive organisms were isolated more often than gram-negative organisms, but the trend is reversing. Streptococci surpassed staphylococci for 5 years as the leading pathogen. Increasing resistance to penicillin, ciprofloxacin, and imipenem was noted in Streptococcus species. With the exception of type 1 beta-lactamase-producing bacteria and Pseudomonas aeruginosa, gram-negative isolates remained overall susceptible to ceftazidime. Increased antibiotic prophylaxis coincided with the reduction in percentage of infected patients and increase in resistance to beta-lactam antibiotics. Mortality attributed to bacteremia was low except for infections caused by P. aeruginosa and the Enterobacter, Serratia, Citrobacter group. There was no mortality attributable to gram-positive organisms such as Staphylococcus aureus and viridans streptococci.     

Influence of bacterial-antibiotic interactions on subsequent antimicrobial activity of alveolar macrophages

The efficacy of an antibiotic in the treatment of bacterial infections depends upon the interactions of drug, bacteria, and phagocytes. In an examination of certain of these interactions, overnight cultures of 3H-labeled Staphylococcus aureus were briefly incubated in the presence or absence of various antibiotics prior to phagocytosis by rabbit alveolar macrophages. Preincubation of organisms with an inhibitor of bacterial protein synthesis (clindamycin, erythromycin, chloramphenicol, or rifampin) but not with a cell wall-active drug (penicillin G or cefazolin) led to an increase in phagocytosis and early intracellular killing by alveolar macrophages. Antibiotic-mediated susceptibility of S aureus to ingestion by alveolar macrophages correlated with the inhibition of bacterial protein synthesis. Clindamycin-treated staphylococci were more efficiently opsonized by heat-inactivated serum and bound larger amounts of specific antibody than did control organisms. Thus, compromise of one or more antiphagocytic surface components secondary to decreased protein synthesis is the means by which certain antibiotics influence bacterial susceptibility to the antimicrobial mechanisms of phagocytes. This effect may be an important determinant in the success of treatment with inhibitors of bacterial protein synthesis.     

Serotonin and noradrenaline concentrations and serotonin uptake in platelets from hyperphenylalaninaemic patients

Summary In three untreated patients with phenylketonuria (PKU), three PKU and six hyperphenylalaninaemic (HPA) patients in good metabolic control, the kinetic constants of plateletin vitro uptake of [¹⁴C]serotonin (5HT) did not significantly differ from those in 12 control subjects matched for age. The platelet concentrations of endogenous 5HT and noradrenaline (NA), taken as long-term indices of the amount of these amines circulating in plasma, were lower than normal in PKU and HPA patients, whether or not they were kept on a diet. However, a reduction in plasma NA concentrations at the moment of blood collection was seen only in untreated PKU patients. These data indicate that there may be a chronic inhibition of 5HT and possibly of NA synthesis even in PKU or HPA subjects in good metabolic control, with normal psychomotor development and only slightly raised plasma phenylalanine levels.     

Heteroresistance to penicillin in Streptococcus pneumoniae

Heteroresistance to beta-lactam antibiotics has been mainly described for staphylococci, for which it complicates diagnostic procedures and therapeutic success. This study investigated whether heteroresistance to penicillin exists in Streptococcus pneumoniae. Population analysis profile (PAP) showed the presence of subpopulations with higher penicillin resistance in four of nine clinical pneumococcal strains obtained from a local surveillance program (representing the multiresistant clones ST179, ST276, and ST344) and in seven of 16 reference strains (representing the international clones Spain(23F)-1, Spain(9V)-3, Spain(14)-5, Hungary(19A)-6, South Africa(19A)-13, Taiwan(23F)-15, and Finland(6B)-12). Heteroresistant strains had penicillin minimal inhibitory concentrations (MICs) (for the majority of cells) in the intermediate- to high-level range (0.19-2.0 mug/ml). PAP curves suggested the presence of subpopulations also for the highly penicillin-resistant strains Taiwan(19F)-14, Poland(23F)-16, CSR(19A)-11, and CSR(14)-10. PAP of bacterial subpopulations with higher penicillin resistance showed a shift toward higher penicillin-resistance levels, which reverted upon multiple passages on antibiotic-free media. Convergence to a homotypic resistance phenotype did not occur. Comparison of two strains of clone ST179 showed a correlation between the heteroresistant phenotype and a higher-penicillin MIC and a greater number of altered penicillin-binding proteins (PBP1a, -2b, and -2x), respectively. Therefore, heteroresistance to penicillin occurs in international multiresistant clones of S. pneumoniae. Pneumococci may use heteroresistance to penicillin as a tool during their evolution to high penicillin resistance, because it gives the bacteria an opportunity to explore growth in the presence of antibiotics before acquisition of resistance genes.     

Viridans streptococcal endocarditis: the role of various species, including pyridoxal-dependent streptococci

The viridans streptococci are a heterogeneous group of organisms frequently associated with microbial endocarditis. Isolates from consecutive patients with endocarditis due to viridans streptococci who were seen at The New York Hospital from 1944 to 1955 and from 1970 to 1978 were speciated, and the relative frequencies and patterns of sus ceptibility to penicillin were determined. Vitamin B6-dependent streptococci, classified as Streptococcus mitior, accounted for 5%-6% of microbial endocarditis in both time periods. Since these nutritional variants require the active forms of vitamin B6 for growth in routein media, they can be responsible for culture-negative endocarditis. Media must be supplemented with either pyridoxal hydrochloride or pyridoxamine dihydrochloride (the active forms of vitamin B6) for isolation, identification, and subsequent testing of susceptibility to antimirobial agents. Pyridoxine hydrochloride does not support the growth of these organisms in vitro.     

Human melanoma cells have both nerve growth factor and nerve growth factor-specific receptors on their cell surfaces.

Human melanoma cells were examined in an indirect membrane immunofluorescence assay for surface nerve growth factor (NGF) and NGF receptors. This assay revealed that human melanoma cells have various levels of NGF and NGF receptors on the plasma membrane, whereas a variety of human sarcoma and carcinoma tumor cells and normal human fibroblasts are negative. Surface NGF could be detected on melanoma cells with a rabbit antiserum directed to NGF at titers as high as 1:64; prior adsorption of this antibody with mouse 2.5S NGF resulted in a loss of fluorescence. The melanoma cells were positive whether or not they were grown in the presence of fetal calf serum. NGF production by human melanomas is a previously unrecognized property of this differentiated cell type. Although other cells in culture have been shown to produce NGF, the association of NGF production with the presence of NGF receptors on the cell surface is rare among tumor cells, and may represent an opportunity for "autostimulation" of melanoma cells by this growth factor.     

Special issues in the management of infective endocarditis caused by gram-positive cocci

Gram-positive cocci, mainly streptococci and staphylococci, continue to cause the majority of cases of infective endocarditis. Among the streptococci causing IE, the long-standing predominance of oral or viridans-group streptococci has progressively faded, while the number of cases caused by "enteric streptococci" (Streptococcus bovis and enterococci) has increased. While most oral streptococci and S. bovis strains remain fully sensitive to penicillin, nutritionally variant streptococci--now renamed Abiotrophia--and enterococci can exhibit resistance to penicillin and/or glycopeptides that makes endocarditis more difficult to treat. Among the staphylococci causing endocarditis, the increasing proportion of coagulase-negative and methicillin-resistant strains observed in recent years has changed the approach to choice of antibiotic therapy. The purpose of this paper is to focus on some new aspects of the management of antibiotic therapy of IE due to streptococci and staphylococci, including recent developments such as once-daily aminoglycoside administration in IE, outpatient antibiotic therapy, and the evaluation of new antibiotics.     

The regulation of growth in glycogen storage disease type 1

OBJECTIVE: To study endocrine and metabolic variables that affect growth in patients with glycogen storage disease type 1 (GSD-1) receiving standard dietary therapy. DESIGN: Observational study. PATIENTS AND MEASUREMENTS: Thirty-eight patients with GSD-1, age range 0.6-32.9 years, were investigated on their usual dietary regimens. Data on height, height velocity in prepubertal children, endocrine and metabolic responses to oral glucose load, 24-h serum cortisol and GH concentration profiles and serum IGF-1 concentrations were collected. RESULTS: The population studied was shorter than average, with a median height standard deviation score (SDS) of -1.60, but significantly taller than a historical population studied at the same institution that had not received dietary therapy at the time of study. A wide range of height SDS was encountered (-5.28 to 1.21) and a subset still exhibit marked growth failure. Median body mass index (BMI) SDS was 0.72 (range -1.34 to 3.96). Those patients with the greatest BMI SDS had the lowest serum GH concentrations but serum IGF-1 concentrations were within the normal range. Patients with the poorest growth exhibit low serum insulin concentration responses to glucose load, GH insensitivity and higher mean 24-h plasma cortisol levels when compared to those patients who were better grown. CONCLUSION: This study shows that overall the growth of this group of patients with glycogen storage disease type 1 has improved compared to that of a historical control group. There remains a subset of this population with poor growth despite therapy. The measured endocrine responses in this subset are similar to those reported for untreated patients. To improve the growth further in these individuals it will be necessary to understand whether this is failure of prescribed therapy or failure to comply with therapy.     

Low density lipoproteins in human plasma make vascular smooth muscle cells resistant to growth inhibition by heparin

OBJECTIVE: Vascular smooth muscle cell hyperplasia plays a role in atherosclerosis and restenosis. While heparin has shown promise as an inhibitor of smooth muscle cell proliferation in vitro and in some animal models, it has failed to reduce restenosis in clinical trials. We have previously shown that human smooth muscle cells grown in the presence of human serum are heparin resistant, whereas in the presence of bovine serum they are heparin sensitive. In this report, we demonstrate that the heparin resistance factor is present in human plasma as well as serum, and characterise it further. METHODS: Human vascular smooth muscle cells were cultured as explants from the media of redundant adult internal mammary or umbilical cord arteries. They were tested for sensitivity to heparin at 100 microg/ml in the growth medium, in the presence of foetal bovine serum, human-plasma-derived serum, human whole blood serum, or fractions derived from these. RESULTS: In the presence of foetal bovine serum, heparin inhibited cell proliferation, while human-plasma-derived or whole blood sera conveyed heparin resistance. This activity was contained within the fraction of plasma/serum which bound to heparin Sepharose, and the sub-fraction which was retained by a membrane filter of molecular weight cut off of 100000. All the heparin resistance in this latter fraction was supplied by lipoproteins. LDL prepared directly from human plasma conveyed similar heparin resistance to the lipoproteins from the above sub-fraction. CONCLUSION: LDL in human plasma/serum conveys resistance to the anti-proliferative effects of heparin upon vascular smooth muscle cells. This activity may interfere with potential therapeutic effects of heparin as an anti-restenosis agent.     

The Eagle effect revisited: efficacy of clindamycin, erythromycin, and penicillin in the treatment of streptococcal myositis

We investigated the relative efficacies of penicillin, clindamycin, and erythromycin in a mouse model of myositis due to Streptococcus pyogenes. Penicillin was ineffective unless given at the time of bacterial injection, and treatment delays of 2 h reduced its efficacy such that survival was no better than that of untreated control animals (P less than .05). Survival of erythromycin-treated mice was greater than that of both penicillin-treated mice and untreated controls, but only if treatment was begun within 2 h. Mice receiving clindamycin, however, had survival rates of 100%, 100%, 80%, and 70% even if treatment was delayed 0, 2, 6, and 16.5 h, respectively. Thus, clindamycin demonstrated superior efficacy to penicillin among all the various treatment groups (P less than .05). Our results corroborate the failure of penicillin in this model of streptococcal infection and suggest that, unlike penicillin, the efficacy of clindamycin is not adversely altered by the "Eagle effect."     

A multi-centre prospective study of febrile neutropenia in Norway: microbiological findings and antimicrobial susceptibility

The urgent need to treat presumptive bacterial or fungal infections in neutropenic patients has meant that initial therapy is empiric and based on the pathogens most likely to be responsible, and drug resistance. The traditional empirical treatment in Norway has been penicillin G and an aminoglycoside, and this combination has been criticized over recent y. We wished to analyse the microbiological spectrum and susceptibility patterns of pathogens causing bacteraemia in febrile neutropenic patients. This was a prospective multicentre study. During the study period of 2 y, a total of 282 episodes of fever involving 243 neutropenic patients was observed. In 34% of episodes bacteraemia was documented. Overall, 40% of the episodes were caused by Gram-positive organisms, 41% by Gram-negative organisms and 19% were polymicrobial. The most frequently isolated bacteria were Escherichia coli (25.6%), a- and non-haemolytic streptococci (15.6%), coagulase-negative staphylococci (12.4%) and Klebsiella spp. (7.4%). None of the Gram-negative isolates was resistant to gentamicin, meropenem, ceftazidime or ciprofloxacin. Only 5 coagulase-negative staphylococci isolates were resistant to both penicillin G and aminoglycoside. The overall mortality rate was 7%, and 1.2% due to confirmed bacteraemic infection.     

Hospital-acquired infections: diseases with increasingly limited therapies.

About 5% of patients admitted to acute-care hospitals acquire nosocomial infections. A variety of factors contribute: increasing age of patients; availability, for treatment of formerly untreatable diseases, of extensive surgical and intensive medical therapies; and frequent use of antimicrobial drugs capable of selecting a resistant microbial flora. Nosocomial infections due to resistant organisms have been a problem ever since infections due to penicillinase-producing Staphylococcus aureus were noted within a few years of the introduction of penicillin. By the 1960s aerobic Gram-negative bacilli had assumed increasing importance as nosocomial pathogens, and many strains were resistant to available antimicrobials. During the 1980s the principal organisms causing nosocomial bloodstream infections were coagulase-negative staphylococci, aerobic Gram-negative bacilli, S. aureus, Candida spp., and Enterococcus spp. Coagulase-negative staphylococci and S. aureus are often methicillin-resistant, requiring parenteral use of vancomycin. Prevalence of vancomycin resistance among enterococcal isolates from patients in intensive care units has increased, likely due to increased use of this drug. Plasmid-mediated gentamicin resistance in up to 50% of enterococcal isolates, along with enhanced penicillin resistance in some strains, leaves few therapeutic options. The emergence of Enterobacteriaceae with chromosomal or plasmid-encoded extended spectrum beta-lactamases presents a world-wide problem of resistance to third generation cephalosporins. Control of these infections rests on (i) monitoring infections with such resistant organisms in an ongoing fashion, (ii) prompt institution of barrier precautions when infected or colonized patients are identified, and (iii) appropriate use of antimicrobials through implementation of antibiotic control programs.     

Septic arthritis in young infants: clinical and microbiologic correlations and therapeutic implications

In order to assess and correlate the bacteriology of neonatal septic arthritis with its clinical presentation, the records of nine infants with this disease that were diagnosed at Edmonton hospitals between 1964 and 1981 were reviewed and 92 other cases reported in the English-language literature since 1960 were evaluated. All Edmonton cases developed outside of the hospital in previously healthy infants. A Streptococcus species was isolated in four of six patients from whom joint fluid was obtained before antibiotic therapy. Analysis of cases from the literature revealed a more variable bacteriology that seemed dependent on whether the case was hospital or community acquired. In 52 hospital-acquired cases, staphylococci were the predominant isolates (62%); next in frequency were Candida species (17%) and gram-negative enteric bacilli (15%). Community-acquired neonatal septic arthritis was most often caused by streptococci (52% of cases), staphylococci (26%), and gonococci (17%). Since 1970 the relative imbalance between staphylococcal (5%) and streptococcal (75%) isolates in community-acquired neonatal septic arthritis is even more pronounced. This pattern emphasizes the importance of ensuring optimal coverage against penicillin-sensitive organisms in community-acquired neonatal septic arthritis; this is in contrast to the situation with hospital-acquired arthritis, where wider-spectrum coverage against staphylococci and gram-negative enteric bacilli remains mandatory.     

Long-term cultivation and differentiation of human erythroleukemia cells in a protein-free chemically defined medium.

To examine whether a human erythroleukemia cell line, K-562, can proliferate and differentiate without protein supplements, long-term cultivation of the cells was carried out in a protein-free chemically defined medium. By the use of stepwise decreases in the fetal bovine serum concentration, continuous growth of K-562 cells was established in a protein-free F-10 medium. The cells have been propagated in this medium for 3 years. The population-doubling time of the cells is about 30 hr. Growth was not stimulated by the addition of insulin, epidermal growth factor, fibroblast growth factor, multiplication-stimulating activity, transferrin, platelet-derived growth factor, or dexamethasone. Addition of serum stimulated the cell growth slightly and increased the saturation density. The saturation density of the cells could be increased to that seen with serum-supplemented cultures by changing the serum-free medium daily. The cells synthesized significant amounts of hemoglobin in the presence of hemin without serum supplementation. The results suggest that the human erythroleukemia cells grown in a protein-free medium do not require serum components for their growth or hemin-induced hemoglobin synthesis and provide an excellent model for better understanding of the growth and differentiation of human leukemia cells.     

Chronic renal failure and atherogenesis--Serum factors stimulate the proliferation of human arterial smooth muscle cells

To assess the role of serum factors in the genesis of accelerated vascular disease in chronic renal failure, human arterial smooth muscle cells (SMC) and dermal fibroblasts were grown in culture and the effects of serum from chronic dialysis patients on cell proliferation was studied. Exposure to serum from these renal failure patients was associated with significantly greater growth of both SMC and fibroblasts than that observed with control serum. A portion of this mitogenic effect appears to be related to the presence of a factor(s) which is heat stable, dialysable, and is contained in the lipoprotein deficient fraction of plasma of density greater than 1.25 g/dl. These findings suggest that circulating substances which stimulate the proliferation of SMC may contribute to accelerated cardiovascular disease in patients undergoing chronic dialysis treatment.     

Serious infections due to penicillin-resistant strains of viridans streptococci with altered penicillin-binding proteins

We investigated the mechanism of resistance to penicillin in two penicillin-resistant clinical isolates of viridans streptococci that caused life-threatening infections in two patients not receiving chronic penicillin therapy. The first was a strain of Streptococcus intermedius that was isolated from the cerebrospinal fluid of a patient with post-neurosurgical meningitis. The second was a strain of Streptococcus mitis recovered from the bloodstream of a leukemic patient with neutropenia. Both patients failed to respond to penicillin. The mechanism of resistance in these strains was associated with diminished affinity for penicillin of their penicillin-binding proteins, as compared with those of penicillin-susceptible control strains. We conclude that penicillin-resistant viridans streptococci may cause serious infections even in patients not receiving chronic penicillin therapy, that this resistance is clinically significant and may result in failure of penicillin therapy, and that the mechanism of resistance in these strains is associated with diminished affinity of the penicillin-binding proteins for penicillin.     

Increase in native valve endocarditis caused by coagulase negative staphylococci: an Anglo-French clinical and microbiological study.

Native valve endocarditis caused by coagulase negative staphylococci has become more common. A study of 35 cases showed that the infections were usually acquired in the community and occurred in men (mean age 51 years). A pre-existing cardiac abnormality (mitral leaflet prolapse in a third of patients) was detected in 26 (74%). The source of the organisms in the community acquired infections was assumed to be the skin, though lesions were seldom demonstrated; most hospital acquired infections resulted from intravenous devices. Community acquired organisms were usually sensitive to penicillin, whereas those acquired in hospital were often multiresistant. Most infections were caused by Staphylococcus epidermidis. The frequency of acute presentation (26%) and of major neurological abnormality (23%), together with the need for valve replacement (often emergency) (51%) and the mortality (36%) suggest that coagulase negative staphylococci can be virulent aggressive pathogens, mimicking Staphylococcus aureus.