Biomedical subjects
Publications and source records attributed to J E Clarridge.
The gastroenterologist must be alert to diagnosing parasitic diseases when collecting intestinal fluid samples or cytologies during endoscopy. Between 1979 and 1982, we identified nematodes in 10 endoscopic specimens. None were Strongyloides stercoralis. We emphasize the importance and technical aspects of distinguishing nonpathogenic nematodes from Strongyloides.
Campylobacter jejuni has emerged as a frequent cause of diarrhea. During a 12-month period at the Houston Veterans Administration Medical Center, we isolated C jejuni from 3.4% of the 290 stool cultures from patients with diarrhea. This compared to an isolation rate of 4.1% for Salmonella and 3.1% for Shigella. During the same period, 17 additional cases of Campylobacter-associated diarrhea were identified in adults at the two other Baylor College of Medicine teaching hospitals. We correlated the clinical history, treatment, and outcome of these 27 cases of Campylobacter-associated diarrhea (22 cases of acute diarrhea and five of chronic diarrhea). In most patients with acute disease, the diarrhea was resolving by the time the results of the cultures were available. The duration of illness was the same whether treated with antibiotics to which Campylobacter was susceptible (effective therapy) or antibiotics to which it was not susceptible (ineffective therapy); the mean duration of diarrhea after submitting the culture was 5.2 days for those with ineffective therapy versus 5.6 days for those receiving effective therapy. Thus, antibiotic therapy did not appear to shorten the duration of acute diarrhea due to Campylobacter. Five patients had chronic diarrhea; all had an unrelated underlying disease, and antibiotic treatment did not change the clinical course despite bacteriologic cure. This study raises questions as to the value of antibiotic therapy for campylobacteriosis, and in this light, we discuss the value of routine culturing for Campylobacter.
A number of antimicrobial agents have been used in the treatment of human brucellosis with varying effectiveness. The purpose of this study was to test the in vitro susceptibility of isolates of four Brucella species to a variety of antimicrobial agents, and to study in vitro synergy of combinations of agents. Minimal inhibitory concentrations (MICs) were determined using conventional broth microdilution methods and commercially available systems. Conventional checkerboard synergy microdilutions were prepared for gentamicin or streptomycin plus tetracycline, and rifampicin plus tetracycline. Synergy or antagonism was determined by the fractional inhibitory concentration index. Penicillin G and ampicillin showed in vitro activity against Brucella (MIC90 4 micrograms/ml), whereas the antipseudomonal penicillins were less active (carbenicillin MIC90 12 micrograms/ml, piperacillin MIC90 32 micrograms/ml). Among the third generation cephalosporins tested, cefotaxime (MIC90 2 micrograms/ml) demonstrated greatest activity. As a class, aminoglycosides were equivalent (MIC90 1-4 micrograms/ml). All strains were sensitive to tetracycline (MIC90 0.25 microgram/ml), trimethoprim-sulfamethoxazole (MIC90 1/19 micrograms/ml), and rifampin (MIC90 1 microgram/ml). Erythromycin (MIC90 greater than 8 micrograms/ml) and vancomycin (MIC90 greater than 16 micrograms/ml) demonstrated no activity. In vitro synergy (fractional inhibitory concentration index less than 0.5) was demonstrated with tetracycline plus rafampin in six of eight isolates tested.
The recent observation that Branhamella catarrhalis may cause a variety of infections in humans has stimulated interest in human host defenses against this organism. We encountered 21 patients with B. catarrhalis infection: seven with pneumonia, 13 with a purulent exacerbation of chronic bronchitis, and one with purulent sinusitis. Normal human serum (NHS) demonstrated no bactericidal activity against 20 of the 21 isolates. In contrast, 7 of 19 acute and 18 of 20 convalescent sera demonstrated significant bactericidal effects against the corresponding B. catarrhalis isolate. Heating convalescent sera to 56 C for 30 min abolished bactericidal activity. This activity was restored by NHS but not by complement-rich guinea pig serum. Selective blockage of the classic complement pathway eliminated bactericidal activity, whereas selective blockage of the alternative pathway did not. IgG isolated from convalescent serum plus NHS was bactericidal for the corresponding B. catarrhalis isolate. These results suggest that most patients with pulmonary infections due to B. catarrhalis develop a convalescent IgG antibody response that mediates serum bactericidal activity by the classic complement pathway.
When amikacin first became available its use was restricted to prevent the emergence of resistant strains of gram-negative bacilli to this new agent. Gentamicin was the aminoglycoside most widely used at this time, and the incidence of gentamicin-resistant bacteria was 14%, while only 2.4% were resistant to amikacin. For a period of 15 months gentamicin use was restricted, and amikacin was used almost exclusively. Amikacin use was associated with a fall in the incidence of gentamicin-resistant bacteria to 9.2% (p less than .00005), while amikacin resistance remained unchanged at 2.2% (NS). During a period of 21 months after all aminoglycoside restrictions were lifted, gentamicin use again increased, and was accompanied by a return of gentamicin resistance to the baseline level of 15.3%. During this period, amikacin resistance also increased to 4.0% (p less than .0000001) but was due primarily to an increase in resistant Pseudomonas aeruginosa. Escherichia coli was the most frequently isolated gram-negative bacillus during all three periods, and it remained sensitive to both antibiotics regardless of the drug in use. In contrast, P. aeruginosa showed a high level of resistance to gentamicin, which fell when this antibiotic was restricted, only to return to a high level with reinstitution of gentamicin. While there was also an increase in amikacin resistant strains of P. aeruginosa with unrestricted aminoglycoside use, there was no apparent shift in the pattern of aminoglycoside modifying enzymes among a small random selection of amikacin-resistant bacteria. Impaired uptake of antibiotic was the predominant mechanism responsible for P. aeruginosa resistance among strains that did not produce aminoglycoside acetyltransferase (AAC)(6').
Two hemolytic phenotypes of Vibrio damsela, isolated from the tissue of a patient with a fatal wound infection, were characterized. The patient had underlying disease, and the wound was associated with an injury inflicted during the handling of a catfish. The phenotypes were morphologically and biochemically similar except for their lecithinase, lipase, and hemolytic activities. When grown on rabbit blood agar, one phenotype (LZ) produced a large zone of hemolysis (10 mm) around the colony, whereas the other type (SZ) produced only a small zone (1 to 2 mm). On sheep blood agar, the differences in hemolytic activity were more subtle. By a modified CAMP test in which V. damsela was streaked perpendicularly to Staphylococcus aureus, it was determined that a factor elaborated by the LZ phenotype (but not the SZ phenotype) protected sheep erythrocytes from the hemolysis normally caused by S. aureus toxins. Cell-free filtrates of broth cultures of each phenotype had the same effects on erythrocytes as did the organisms themselves.
Although coagulase-negative staphylococci (C-NS) have been implicated in certain human infections, they are generally regarded as contaminants, and their clinical significance is questioned. To assess their role as pathogens, we studied 205 isolates of C-NS from wounds and body fluids (blood, urine, pleural and peritoneal fluids, etc.). Patient's charts were reviewed, and, by using strict criteria, a determination was made regarding the clinical significance of these isolates. The organisms were then identified to determine whether certain species of C-NS were associated with specific infections. S epidermidis sensu stricto accounted for 81% of the C-NS isolated. The frequencies of other species were: S. haemolyticus (6%), S. hominis (5%), S. capitis (4%), S. warneri (3%), and others (1%). Only two isolates were novobiocin resistant; neither was identified as S. saprophyticus. By using our criteria, 22% of the C-NS were considered to be clinically significant, and the majority of these (93%) was S. epidermidis. The most common source of the clinically relevant C-NS isolates was wounds. These data suggest that identification of C-NS species other than S. epidermidis may be of limited value in predicting clinical significance.
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Edwardsiella tarda is an uncommon enteric bacterium which has been found generally in animal hosts and occasionally in human feces. Three cases of extraintestinal infection caused by E. tarda which are described herein include a typhoid-like illness, peritonitis with sepsis, and cellulitis from a wound acquired while fishing. The microbiology of E. tarda and the previous reports of infection due to this organism are reviewed.
A middle-aged woman developed malabsorption and severe protein-calorie malnutrition after a near-total gastrectomy for a perforated gastric ulcer. A transbronchial lung biopsy showed pulmonary infection with Torulopsis glabrata. Improvement in the patient's nutritional status was followed by clearing of the pneumonia without the need for antifungal chemotherapy.
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