Current trends in bacterial respiratory pathogens.

The relationship of virulence and antimicrobial susceptibility with morbidity due to bacterial respiratory pathogens is complex and evolving. Ultimately, decreasing the incidence of pneumonia due to bacterial pathogens will be dependent on successful preparation and distribution of effective vaccines. Until effective vaccines are widely available, control of a majority of respiratory infections will depend on promotion of rational therapeutic strategies. Though limited to a few specific serotypes and strains, changes in virulence of bacterial respiratory pathogens have been noted. Co-infections due to multiple respiratory pathogens may increase morbidity; however, the epidemiology of co-infections is not clear. Relationships between respiratory viruses and bacteria may exist that increase virulence of both agents, but information regarding these relationships awaits further investigation. Resistance of respiratory pathogens to the more commonly used antimicrobials, such as penicillin, erythromycin, chloramphenicol, and cotrimoxazole, is being documented globally with increasing frequency. The evolution of antimicrobic resistance, especially among strains of Streptococcus pneumoniae, the most common and deadly agent of lower respiratory tract infections, provides impetus to develop and promote effective pneumococcal vaccines and to search for new and effective antimicrobials.

Streptococcal perianal disease in children.

From October 1985 through June 1986, 31 children in a single pediatric practice were treated for perianal signs and symptoms associated with growth of group A beta-hemolytic streptococci from perianal cultures. Signs and symptoms included perianal dermatitis (90%), perianal itching (78%), rectal pain (52%), and blood-streaked stools (35%). Ages ranged from 7 months to 8 years mean 4.25 +/- 1.8 years). There were 24 boys (77%) and seven girls (23%). The 31 cases occurred in 19 families. Intrafamily spread was only to siblings and occurred in 50% of the possible situations. Direct perianal antigen studies had a sensitivity of 89% for predicting positive cultures. Four different T types of group A streptococci were isolated from these cases, but the T type within each family outbreak was identical except in one case. When group A streptococci were found in the pharynx (64% of patients), the T type of the pharyngeal and perianal isolates were identical. Treatment was usually with oral penicillin. Relapses occurred in 39%. Signs of cellulitis were absent in all 31 cases and, therefore, we suggest that the nomenclature for this entity be changed from streptococcal perianal cellulitis to streptococcal perianal disease.

Rapid group A streptococcal antigen detection kit: effect on antimicrobial therapy for acute pharyngitis.

Newly introduced rapid diagnostic tests for group A streptococcal pharyngitis should facilitate appropriate antimicrobial use in patients with group A streptococcal pharyngitis. Because of high rates of acute pharyngitis in Tuba City, AZ, at the Navajo Indian reservation, the use of rapid diagnostic test was prospectively evaluated. The sensitivity and specificity of the test was measured and changes in physician prescribing patterns attributable to use of the test were correlated. Of 320 patients with pharyngitis enrolled during the present 3-week study, 86 met the study's definition of a patient with streptococcal pharyngitis and 163 met the study's definition of a patient with nonstreptococcal pharyngitis. The rapid test was 62.8% sensitive and 96.9% specific in identifying patients from whom group A streptococci were isolated. Although treatment of patients with streptococcal pharyngitis at the time of the first visit increased from 36.5% in a retrospective sample to 72.5% during the study, treatment of patients in whom cultures were negative remained the same. Further analyses showed that physicians tended to treat patients with signs characteristic of streptococcal pharyngitis and, as the study progressed, to rely less on negative rapid test results as a reason to withhold antimicrobial agents. It was concluded that rapid tests with good specificity but limited sensitivity may improve treatment of patients with streptococcal pharyngitis by allowing earlier specific therapy. A more sensitive test with a higher negative predictive value would be necessary to prevent treatment of persons with nonstreptococcal pharyngitis.

Nosocomial transmission of group B streptococci.

Group B streptococci are an important cause of infant septicemia and meningitis. A prospective study of group B streptococcal colonization in a 300-bed community hospital disclosed rates of 29% of 297 third-trimester women, 37% of 242 newborn infants, and 45% of 22 hospital personnel. Colonized parturients were more frequently black and anemic on admission for delivery. Infant colonization was statistically associated with a positive maternal genital culture, low birthweight, and prematurity. Nosocomial transmission of group B streptococci was strongly suggested by observations that 41% of colonized infants were born to culture-negative women and such infants became colonized later in their hospital stay than did colonized infants born to colonized women. Furthermore, hospital personnel working in the labor-delivery and nursery areas had a significantly higher prevalence of the organism than did personnel from other areas. Clearly, more information is needed about the epidemiology of group B streptococcal disease before appropriate and rational control measures can be recommended.

Outbreaks of group A streptococcal abscesses following diphtheria-tetanus toxoid-pertussis vaccination.

Two outbreaks of group A streptococcal abscesses following receipt of diphtheria-tetanus toxoid-pertussis (DTP) vaccine from different manufacturers were reported to the Centers for Disease Control (CDC) in 1982. The clustering of the immunization times of cases, the isolation of the same serotype of Streptococcus from all cases in each outbreak, and the absence of reported abscesses associated with receipt of the same lots of vaccine in other regions of the country, suggest that each outbreak was probably caused by contamination of a single 15-dose vial of vaccine. The preservative thimerosal was present within acceptable limits in unopened vials from the same lot of DTP vaccine in each outbreak. Challenge studies indicate that a strain of Streptococcus from one of the patients can survive up to 15 days in DTP vaccine at 4 degrees C. Contamination of vials during manufacturing would have required survival of streptococci for a minimum of 8 months. Preservatives in multidose vaccine vials do not prevent short-term bacterial contamination. Options to prevent further clusters of streptococcal abscesses are discussed. The only feasible and cost-effective preventive measure now available is careful attention to sterile technique when administering vaccine from multidose vials.

The gram positive cocci.

Recent changes in taxonomy of the gram positive cocci are discussed. Views on these changes and practical methods of differentiating the staphylococci, micrococci, streptococci, and aerococci are presented. Simplified schemes, using acceptable clinical laboratory techniques, are presented that either differentiate or categorize the pathologically important gram positive coccal species.

Neonatal enterococcal sepsis: case-control study and description of an outbreak.

An increased incidence of neonatal sepsis caused by Group D streptococci, specifically enterococci (GDE), during a recent 6-month period prompted a 5-year review of enterococcal sepsis in our neonatal intensive care unit. Sixteen episodes occurred in 14 babies. GDE accounted for 8 of 19 (42%) episodes of neonatal bacteremia during the epidemic period vs. only 8 of 159 (5%) episodes during the remaining 4.5 years (endemic period) (P less than 0.001). Blood isolates were all identified as Streptococcus faecalis. A combination of three strain-typing methods successfully distinguished the epidemic organisms from endemic nursery strains of GDE and from "background" GDE flora in the hospital. Nursery isolates were all susceptible to ampicillin, intermediate or resistant to the aminoglycosides and variably resistant to the newer cephalosporins. There were no differences in antibiotic susceptibilities of the GDE or in characteristics of the patients that were unique to the epidemic. Neonates with GDE sepsis had a mean birth weight of 913 g, a mean gestational age of 27 weeks and a mean age of onset of sepsis of 8.5 weeks. Twenty-five controls, matched for birth weight and admission date, were identified. Significant differences (P less than 0.05) between cases and controls included: use of a nonumbilical central line (71 vs. 32%); days central line in place (26.5 vs. 6.5 days); and bowel resection (29 vs. 4%). This is the first reported outbreak of S. faecalis sepsis in neonates. GDE are important nosocomial pathogens that must be considered in late onset neonatal sepsis.

Risk factors for nasopharyngeal carriage of resistant Streptococcus pneumoniae and detection of a multiply resistant clone among children living in the Yukon-Kuskokwim Delta region of Alaska.

BACKGROUND: Children < 2 years old living in the Yukon-Kuskokwim Delta (YKD) region of Alaska have one of the highest pneumococcal bacteremia rates of in the world. METHODS: To determine the prevalence of and risk factors for infection with intermediate or resistant Streptococcus pneumoniae in the YKD, we cultured nasopharyngeal secretions of healthy children < or = 5 years old, reviewed their hospital records and administered questionnaires to accompanying parents. RESULTS: Of 185 children evaluated we obtained 95 pneumococcal isolates; drug susceptibility patterns and serotyping results were available for 92. Of these, 33 (36%) were intermediate or resistant to at least one drug class tested; 27 isolates were intermediate (minimum inhibitory concentration 0.1 to 1.0 mg/l) and none were resistant to penicillin. Compared with other isolates, capsular serotype 6B isolates were more likely to be intermediate or resistant to at least one drug (relative risk, 5.3; P < 0.001) and to more than one drug (relative risk, 17.0; P < 0.001). The majority of 6B isolates had identical pneumococcal surface protein A patterns. Carriage of intermediate or resistant pneumococcus was associated with age < 2 years (relative risk, 3.0; P < 0.001) but not with antibiotic use or other evaluated risk factors. CONCLUSIONS: Young age but not antibiotic use was associated with carriage of intermediate or resistant S. pneumoniae in the YKD region of Alaska. Much of the intermediate or resistant pneumococcus in the YKD may have resulted from the proliferation of a single capsular serotype 6B clone.

Pneumococcal vaccination. Controversies and opportunities.

The morbidity and mortality associated with pneumococcal infections are preventable in many high-risk individuals by immunization with 23-valent pneumococcal vaccine. While the clinical effectiveness of the current vaccine is less than ideal, use of the vaccine is cost effective. In spite of recommendations for pneumococcal vaccination of elderly and other high-risk persons, and federal reimbursement for vaccination Medicare enrollees, it was estimated in 1985 that only 10% to 15% of this target population was immunized. Strategies for immunizing high-risk individuals with pneumococcal vaccine need to involve physicians, public health professionals, health advocacy groups, and persons in the targeted populations.

Epidemiologic studies among Amerindian populations of Amazônia. I. Pyoderma: prevalence and associated pathogens.

Pyoderma was studied among a representative sample of the residents of four remote Amerindian villages, Amazonas State, Brazil, during July-August 1976. The overall prevalence among the 775 inhabitants examined was 11%, with little intervillage variation. When the attack rates for the entire sample population were calculated by 5-year age intervals, the 0- to 4-year-olds had the highest rate, 31%. The highest prevalence, 38%, was found among 3-year-olds. Attack rates were not apparently related to sex. Cultures which were taken from representative pyoderma lesions from people in the four survey villages and from three additional villages were studied by a modified delayed culture technique for recovery of gram-positive pathogens from silica-gel desiccated swabs. Group A and group G B-hemolytic streptococci, coagulase positive Staphylococcus aureus, and Corynebacterium diphtheriae were isolated. Group A S. pyogenes was most commonly found, occasionally as the sole pathogenic species. No nephritogenic M-types were found, although most isolates were not M-typable. The T-types found corresponded to those previously reported as being pyoderma-associated. Most pyoderma-associated C. diphtheriae isolates were non-toxigenic. Biotypes gravis and mitis were equally represented.

Susceptibility of relatively penicillin-resistant Streptococcus pneumoniae to newer cephalosporin antibiotics.

Antimicrobial susceptibilities were performed at the Centers for Disease Control on 3400 Streptococcus pneumoniae isolates that were collected during a national survey of serotype-distribution of pneumococci found in normally sterile body fluids. The results showed 126 isolates (3.7%) to be relatively resistant to penicillin (RPR). The RPR strains were tested for susceptibility to cefuroxime, ceftriaxone, cefotaxime, cefamandole, cefaclor, ceftazidime, and moxalactam. These newer generation cephalosporin drugs were tested either because of their ability to penetrate into the cerebrospinal fluid (CSF) or for their activity against pneumococci. Three hundred ninety-one pneumococci were tested with 179 resistant to at least one antimicrobial. The RPR strains were not categorically resistant to the cephalosporins but were fourfold more resistant to them than were the penicillin-susceptible strains. The three most effective antimicrobials in the study for RPR were cefuroxime, cefotaxime, and ceftriaxone [corrected]. Each gave MICs that were attainable in CSF for RPR. Fifty percent of the RPR were inhibited by 0.06 mg/ml and 90% by 0.25 micrograms/ml of these antimicrobials. The least effective were cefaclor, moxalactam, and ceftazidime.

Enterococcus raffinosus sp. nov., Enterococcus solitarius sp. nov. and Enterococcus pseudoavium sp. nov.

Deoxyribonucleic acid base composition, deoxyribonucleic acid-deoxyribonucleic acid hybridization, and biochemical studies were performed on some enterococci from clinical sources of uncertain taxonomic position. Our results indicate that 6 human strains, a single clinical isolate and a strain from bovine mastitis are genetically distinct from each other and all other previously described Enterococcus species and constitute three new species, for which the names Enterococcus raffinosus, Enterococcus solitarius and Enterococcus pseudoavium are proposed.

Streptococcal emm types associated with T-agglutination types and the use of conserved emm gene restriction fragment patterns for subtyping group A streptococci.

The T-agglutination types were determined for a diverse collection of 1531 group A streptococci for which the 5' M protein gene (emm) sequences had been analysed. The majority of the T-agglutination types correlated with previously seen M/emm/T-type associations; however, several new associations were found. Analysis of a subset of this collection -- which included 1157 clinical isolates with multiply encountered emm types -- found that emm amplicon restriction profiles of isolates sharing identical T types and opacity factor phenotypes are useful for detecting groups of isolates with identical emm genes. Many emm genes of known 5' sequence display a highly conserved restriction pattern amongst clinical isolates widely separated both geographically and temporally.

Discrimination of Streptococcus pneumoniae from other upper respiratory tract streptococci by arbitrarily primed PCR.

OBJECTIVES: In the clinical laboratory, identification of Streptococcus pneumoniae can be confused with other streptococci. Conventional biochemical tests such as optochin sensitivity and bile solubility can give inconsistent results. This report presents a method to distinguish true S. pneumoniae from other upper respiratory tract streptococci when conventional tests fail. DESIGN AND METHODS: We used arbitrarily primed polymerase chain reaction with the single primer M13 universal as a method to distinguish S. pneumoniae from other upper respiratory tract streptococci. RESULTS: The fingerprint pattern of S. pneumoniae was established by amplifying DNA of S. pneumoniae type strains 1-48 and of other common upper respiratory tract streptococci at three different DNA concentrations with the single primer M13 universal. From these type strains, a common arbitrarily primed-polymerase chain reaction pattern was identified characterized by two predominant bands of equal intensity at 800 base pairs and at 1100 base pairs. Fingerprint patterns of viridans streptococci were easily distinguishable from those of S. pneumoniae. Many of the clinical isolates used in this study were equivocal by conventional tests but were distinguishable by their fingerprint patterns. CONCLUSIONS: Our results indicated that the fingerprint pattern of S. pneumoniae is species specific and distinguishes true S. pneumoniae of clinical isolates from other streptococci when conventional biochemical tests are unclear.