The Nature of Rehabilitation Programs to Improve Musculoskeletal, Biomechanical, Functional, and Patient-Reported Outcomes in Athletes With ACL Reconstruction: A Scoping Review

CONTEXT

After anterior cruciate ligament (ACL) reconstruction (ACLR), athletes commonly undergo prolonged rehabilitation (eg, 9-12 months), but few actually return to preinjury sports activities. The nature (composition, configuration) of an ACL rehabilitation program (ACL-RP) is an important factor in determining rehabilitation outcomes; however, details about the nature of ACL-RPs are reported inconsistently in research studies. To guide future research reporting to support clinical translation and implementation of ACL-RPs, it is necessary to describe the nature, reporting, and outcomes of ACL-RPs in the current literature.

OBJECTIVE

The purpose of this scoping review was to understand the nature and reporting of various ACL-RPs that address musculoskeletal, biomechanical, functional, or patient-reported outcome measures in adult and pediatric athletes with ACLR.

DATA SOURCES

Articles were selected from searches in 5 electronic databases (PubMed, EbscoHost [MEDLINE, SportDiscus, CINAHL Plus], PROQuest, Cochrane, and Embase).

STUDY SELECTION

Studies were included if they evaluated a post-ACL-RP that implemented strength, balance, plyometric, change of direction running, and/or agility running and included self-reported physical function, quality of life, or pain outcomes.

STUDY DESIGN

Scoping review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) guidelines.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Data were extracted and synthesized to evaluate the reporting of acute program variables (APVs) and exercise descriptors (EDs); 17 studies were included in the final synthesis.

RESULTS

Studies reported between 0% and 67% of the APVs and EDs combined. Only 2 studies were considered to have adequate reporting of both APVs and EDs.

CONCLUSION

Inadequate reporting of APVs and EDs in past studies restricts the translation and implementation of existing research-based ACL-RPs to present-day clinical contexts.

Test-retest reliability of quantitative sensory testing, active joint position sense, and functional hop testing in amateur adult athletes with unilateral anterior cruciate ligament reconstruction

OBJECTIVES

The somatosensory system fulfils a critical role in functional knee joint stability (FKJS) by providing afferent feedback necessary for neuromuscular control. Individuals with anterior cruciate ligament reconstruction (ACLr) have altered somatosensory function. Somatosensory characteristics are assessed by proprioception and quantitative sensory testing. The purpose of the study was to examine intra-rater and inter-rater reliability of methods used to assess somatosensory characteristics and FKJS in amateur adult athletes with unilateral ACLr.

DESIGN

Repeated measures.

SETTING

University.

PARTICIPANTS

8 female, 4 male with unilateral autogenous ACLr.

MAIN OUTCOME MEASURES

Bilateral measurements at 5 lower extremity locations and the anterior forearm: light touch (LT), vibration sense (VS), pressure pain threshold (PPT); knee active joint position sense (AJPS); adapted crossover hop for distance (ACHD). Intraclass correlation coefficients (ICC) determined reliability, defined as: poor (<0.50), moderate (0.50-0.75), good (0.75-0.90).

RESULTS

ACLr-side intra-rater/inter-rater ICCs ranged: LT, -0.27-0.80/-0.01-0.84; VS, 0.12-0.90/0.25-0.90; PPT, 0.49-0.98/0.86-0.99; AJPS, 0.15-0.79/0.55-0.87; ACHD, 0.98/0.99. Uninjured-side intra-rater/inter-rater ICCs ranged: LT, 0.12-0.66/-0.09-0.64; VS, 0.35-0.89/0.05-0.81; PPT, 0.65-0.99/0.45-0.95; AJPS, 0.07-0.81/0.37-0.99; ACHD, 0.99/0.98.

CONCLUSIONS

Intra-rater and inter-rater reliability was poor to good for both limbs. Overall, PPT and the ACHD demonstrated the highest ICCs. Some somatosensory assessments can be employed with confidence, while others should be used with caution.

Sex differences in knee extensor torque control

There is currently equivocal evidence regarding sex-related differences in measures of muscle force and torque control. To that end, we investigated sex differences in knee extensor muscle torque control, using both magnitude- and complexity-based measures, across contraction intensities typical of activities of daily living. 50 participants (25 male, median age [and interquartile range] 23.0 [20.0-33.0]; 25 female, median age [and interquartile range] 21.0 [20.0-40.5]) performed a series of intermittent isometric knee extensor contractions at 10, 20 and 40% maximal voluntary contraction (MVC). Torque was measured in N·m and torque control was quantified according to the magnitude (standard deviation [SD], coefficient of variation [CV]) and complexity (approximate entropy [ApEn], detrended fluctuation analysis [DFA] α) of torque fluctuations. Males exhibited a significantly greater absolute magnitude (i.e., SD) of knee extensor torque fluctuations during contractions at 10% (P = 0.011), 20% (P = 0.002) and 40% MVC (P = 0.003), though no sex differences were evident when fluctuations were normalised to mean torque output (i.e., CV). Males exhibited significantly lower ApEn during contractions at 10% (P = 0.002) and 20% MVC (P = 0.024) and significantly greater DFA α during contractions at 10% (P = 0.003) and 20% MVC (P = 0.001). These data suggest sex differences in muscle torque control strategies and highlight the need to consider both the magnitude and complexity of torque fluctuations when examining sex differences in muscle force control.

The feasibility, safety, and efficacy of lower limb garment-integrated blood flow restriction training in healthy adults

OBJECTIVES

Explore the feasibility of lower-limb garment-integrated BFR-training.

DESIGN

Observational study.

SETTING

Human performance laboratory.

PARTICIPANTS

Healthy males with no experience of BFR-training.

MAIN OUTCOME MEASURES

Feasibility was determined by a priori thresholds for recruitment, adherence, and data collection. Safety was determined by measuring BFR torniquet pressure and the incidence of side effects. Efficacy was determined by measuring body anthropometry and knee isokinetic dynamometry. Feasibility and safety outcomes were reported descriptively or as a proportion with 95% confidence intervals (95% CI), with mean change, 95% CIs, and effect sizes for efficacy outcomes.

RESULTS

Twelve participants (mean age 24.8 years [6.5]) were successfully recruited; 11 completed the study. 134/136 sessions were completed (adherence = 98.5%) and 100% of data were collected. There was one event of excessive pain during exercise (0.7%, 95% CI 0.0%, 4.0%), two events of excessive pain post-exercise (1.5%, 95% CI 0.4%, 5.5%), and one event of persistent paraesthesia post-exercise (0.7%, 95% CI 0.0%, 4.0%). Mean maximal BFR torniquet pressure was <200 mmHg. We observed an increase in knee extension peak torque (mean change 12.4 Nm), but no notable changes in body anthropometry.

CONCLUSIONS

Lower-limb garment-integrated BFR-training is feasible, has no signal of important harm, and could be used independently.

A cross-sectional retrospective survey of injury situation and prevalence in female recreational netball players with a focus on knee injuries

OBJECTIVES

To examine situations of injury and injury prevalence in female adult recreational netball players with a focus on knee injuries.

DESIGN

Cross sectional retrospective online survey.

PARTICIPANTS

193 female adult recreational netball players.

MAIN OUTCOME MEASURES

Any injury sustained in the previous 12 months, situation of injury, any knee injuries sustained in the previous five years, the length of time unable to play netball, and knee injury management.

RESULTS

In the previous 12 months, 61% of respondents sustained injury to the lower limb, and 27% to the upper limb. Lower limb injury situations were mostly landings (46%). Upper limb injury situations were mostly collisions with an opponent (27%). 46% reported sustaining a knee injury in the previous five years. Following knee injury, players were unable to play netball for 6.8 ± 7.0 months (training); and 8.2 ± 7.4 months (matches) respectively.

CONCLUSIONS

Lower limb injury is more common than upper limb injury in recreational adult female adult netball players. Landing was the most common situation of injury for the lower limb including knee injuries. In the previous five years, nearly half of the players had sustained a knee injury resulting in more than six months out of the game.

Measuring complexity of muscle force control: Theoretical principles and clinical relevance in musculoskeletal research and practice

Musculoskeletal conditions affect bones, joints, and muscles of the locomotor system and are a leading cause of disability worldwide. This suggests that current musculoskeletal rehabilitation techniques fail to target the characteristics (e.g., physiological/physical/psychological) most influential for long-term musculoskeletal health. To identify whether a physiological characteristic is impaired, it must be measured. In neuromuscular control, traditional research approaches use magnitude-based measurements (e.g., peak force/standard deviation of force/coefficient of variation of force). However, magnitude-based measurements miss 'hidden information' regarding a physiological system's status across time. To better identify physiological characteristics that are clinically-important for long-term musculoskeletal health, other measurement approaches currently less applied in musculoskeletal research may be helpful. The purpose of this article is to present an introduction to technical and measurement principles for quantifying the 'complexity' of muscle force control as one representation of peripheral joint neuromuscular control. Complexity measurements are time-based and consider the irregular temporal structure of physiological signals. We review theoretical principles underlying measuring complexity of muscle force control and explain its clinical relevance for musculoskeletal scientists and clinicians. The principles include sensorimotor control of peripheral joints, muscle force signal construction and features, muscle force control measurement procedures, and variability and complexity variables. We propose the potential utility of measuring the complexity of muscle force control for diagnosing sensorimotor system impairment and prognosis following musculoskeletal disease or injury. This article will serve as an educational asset and a scientific resource that will inform future research directions to optimise rehabilitation for people with peripheral joint disease and injury.

Alterations in peripheral joint muscle force control in adults with musculoskeletal disease, injury, surgery, or arthroplasty: A systematic review and meta-analysis

PURPOSE

To systematically review and analyse whether musculoskeletal conditions affect peripheral joint muscle force control (i.e. magnitude and/or complexity of force fluctuations).

METHODS

A literature search was conducted using MEDLINE, CINAHL and SPORTDiscus databases (from inception-8th April 2021) for studies involving: 1) participants with musculoskeletal disease, injury, surgery, or arthroplasty in the peripheral joints of the upper/lower limb; 2) comparison with an unaffected control group or unaffected contralateral limb; and 3) measures of the magnitude and/or complexity of force fluctuations during targeted isometric contractions. The methodological quality of studies was evaluated using a modified Downs and Black Quality Index. Studies were combined using the standardized mean difference (SMD) in a random-effects model.

RESULTS

14 studies (investigating 694 participants) were included in the meta-analysis. There was a significant effect of musculoskeletal conditions on peripheral joint muscle force coefficient of variation (CV; SMD = 0.19 [95 % CI 0.06, 0.32]), whereby individuals with musculoskeletal conditions exhibited greater CV than controls. Subgroup analyses revealed that CV was only greater: 1) when comparison was made between symptomatic and asymptomatic individuals (rather than between affected and contralateral limbs; SMD = 0.22 [95 % CI 0.07, 0.38]); 2) for conditions of the knee (SMD = 0.29 [95 % CI 0.14, 0.44]); and 3) for ACL injury post-surgery (SMD = 0.56 [95 % CI 0.36, 0.75]).

CONCLUSION

Musculoskeletal conditions result in an increase in peripheral joint muscle force CV, with this effect dependent on study design, peripheral joint, and surgical status. The greater force CV is indicative of decreased force steadiness and could have implications for long-term tissue health/day-to-day function.

Specificity of isokinetic assessment in noncontact knee injury prevention screening: A novel assessment procedure with relationships between variables in amateur adult agility-sport athletes

OBJECTIVES

To present a new knee isokinetic assessment procedure linked to noncontact knee injury mechanisms and examine correlations between variables relevant to noncontact knee injury prevention screening (peak torque [PT, Nm], time-to-peak torque [TTPT, ms], angle-of-peak torque [APT, °], mean PT [MPT, Nm]).

DESIGN

Cross-sectional.

SETTING

Sports medicine laboratory.

PARTICIPANTS

Thirty-four agility-sport athletes (male/female n = 18/16, age 24.1 ± 3.5yr, height 171.8 ± 9.6 cm, mass 70.6 ± 12 kg).

MAIN OUTCOME MEASURES

Pearson's/Spearman's correlation (r/r_s), coefficient of determination (r²/r_s²).

RESULTS

Most correlations were statistically non-significant or statistically-significant with only weak-to-moderate coefficients. For both knee extension and flexion, PT and MPT were significantly and strongly correlated (r = 0.99, r² = 0.98, p = 0.001). Graphical analyses revealed two datapoint clusters for knee flexion TTPT and APT. One cluster indicated some participants could generate knee flexor PT rapidly (<150 ms) at low knee flexion angles (<45°) and the other cluster indicated that other participants could not (>200 ms, >50°).

CONCLUSIONS

In this study, most isokinetic variables represented distinct knee neuromuscular characteristics. For both knee extension and flexion, only PT or MPT need be used to represent isokinetic maximal strength. Knee flexion TTPT and APT may have utility in noncontact knee injury prevention screening with amateur adult agility-sport athletes.

Preseason weight-bearing ankle dorsiflexion in male professional football players with and without a history of severe ankle injury: A novel analysis in an English Premier League club

OBJECTIVES

Ankle injuries are common in professional football and have profound player/team/club consequences. The weight-bearing lunge-test (WBLT) assesses ankle dorsiflexion range-of-motion in football primary/secondary injury prevention and performance contexts. Data for uninjured and previously ankle-injured players in the English Premier League (EPL) is not available. This study analysed WBLT measurements (cm) within and between uninjured and previously severe ankle-injured players (injured-stiff group, injured-lax group) in one EPL club.

DESIGN

Cross-sectional.

SETTING

Preseason.

PARTICIPANTS

Forty-nine players (age 22.9 ± 4.6 yr; height 181.6 ± 5.2 cm; mass 77.7 ± 7.6 kg).

MAIN OUTCOME MEASURES

Prevalence (%) of previous unilateral severe ankle injury (USAI). Side-to-side (right/left, dominant/nondominant, injured/uninjured) WBLT comparisons at group-level (t-test [within-group]; Welch's ANOVA [between-group]; effect sizes [within-/between-group]) and individual-level (limb symmetry index [%]; absolute-asymmetry [%]).

RESULTS

Prevalence of USAI was 38.7%. There were no statistically-significant side-to-side differences for within-/between-group comparisons. Effect sizes: just-below-large (injured-stiff) and extremely-large (injured-lax) for within-group injured-side/uninjured-side comparisons; just-below-medium (injured-lax) to just-above-medium (injured-stiff) for injured-side comparisons to uninjured players. Absolute-asymmetries: uninjured players, 15.4±13.2%; injured-stiff, 21.8±33.6%; injured-lax 20.4±13.6%.

CONCLUSIONS

Over one-third of players had previous USAI. Effect sizes indicate substantial within-group side-to-side differences and less substantial between-group differences. Across groups, some players had absolute-asymmetries that may elicit concern in ankle primary/secondary injury prevention and performance contexts.

Noncontact Knee Ligament Injury Prevention Screening in Netball: A Clinical Commentary with Clinical Practice Suggestions for Community-Level Players

Netball is a predominantly female team court-sport which is played worldwide. Netball is becoming more popular in the United States following its countrywide introduction to schools and community centers. A unique characteristic of netball is the footwork rule which restricts players to a one-step landing after catching the ball. Most netball landings are single-leg landings resulting in high vertical ground reaction forces and high skeletal tissue forces. Thus, high-risk landing events that have the biomechanical potential for injury occur frequently. Noncontact knee ligament injuries are common following a knee abduction collapse when landing. Because the consequences of noncontact knee ligament injury are profound, strategies are needed to mitigate the burden of such injury for players, teams, and society. The purpose of this clinical commentary is to demonstrate how theoretical principles, different types of research, and different levels of evidence underpin a rational clinical reasoning process for developing noncontact knee ligament injury prevention screening procedures in netball. The theoretical principles that are discussed in this commentary include injury control, the sequence of prevention, principles of screening in injury prevention, the multifactorial model of injury etiology, complex systems theory, and systems science. The different types of research that are reviewed include descriptive and analytic-observational studies. The different levels of evidence that are discussed include prospective studies, cross-sectional studies, and clinicians' own kinesiological modelling. Subsequently, an integrated approach to the evidence-informed development of noncontact knee ligament injury prevention screening procedures is presented. Clinical practice suggestions include a selection of evidence-informed screening tests that are quickly and easily implemented with netball players in local communities. The need for repeated screening at strategic timepoints across a season/year is explained. Sports physical therapists will find this commentary useful as an example for how to undertake clinical reasoning processes that justify the content of screening procedures contributing to noncontact knee ligament injury prevention in community-level netball.

LEVEL OF EVIDENCE

5.

Situations and mechanisms of non-contact knee injury in adult netball: A systematic review

OBJECTIVES

Noncontact knee injuries in netball are a concern due to a range of negative consequences. To reduce the number of injuries, identifying the situation and mechanism of injury is important. This systematic review examined the literature reporting the situation and mechanism of noncontact knee injury in netball.

DESIGN

Systematic Review.

METHODS

PRISMA guidelines were followed and specific key-term combinations used to search databases. Descriptive and analytic-observational studies reporting the situation or mechanism of noncontact knee injury in females playing netball were included (evaluated using frequency counts).

RESULTS

Six articles were included (combined sample 11,401). Players self-reported the situation of injury in five studies, only one study reported both the situation and mechanism of injury. Landing was the most reported situation of knee injury, representing 46.6% of all knee injuries whilst knee abduction (valgus) collapse was the most observed mechanism. Situation and mechanism of noncontact knee injury in netball were not adequately reported.

CONCLUSIONS

Despite the variations in reporting methods, landing is the most common situation of injury. As only one study reported mechanism of injury, it is difficult to draw conclusions but the mechanism of noncontact knee injury in netball appears similar to those identified in other female athletes.

Reporting of acute programme variables and exercise descriptors in rehabilitation strength training for tibiofemoral joint soft tissue injury: A systematic review

OBJECTIVE

Strength training acute programme variables (APVs) can impact tibiofemoral joint injury outcomes. Exercise descriptors (EDs; e.g. patient-position) specify configurations within which APVs are applied. Evidence-based practice depends on adequate reporting of APVs and EDs to replicate strength training interventions in clinical practice. This systematic review assessed APV and ED reporting for adults with tibiofemoral joint injury (anterior cruciate ligament (ACL)/posterior cruciate ligament (PCL)/medial collateral ligament (MCL)/lateral collateral ligament (LCL)/meniscus/hyaline cartilage (HC)).

METHODS

PRISMA guidelines were followed. Specific key-term combinations were employed and database searches performed. Descriptive/observational/experimental studies were included (2006-2018). Studies needed to report pre-defined APVs or EDs for ≥51% of all exercises to be included. Frequency counts were made of studies adequately reporting APVs and EDs.

RESULTS

Sixteen articles were included (ACL = 13; meniscus = 3). No PCL/MCL/LCL/HC articles were identified. Of nine APVs, five and four were consistently reported by the majority of ACL (≥7) and meniscal (≥2) studies, respectively. Of eight EDs, four were consistently reported by the majority of both ACL (≥8) and meniscal (≥2) studies.

CONCLUSION

Many APVs and EDs were not adequately reported. Future studies should better document APVs and EDs for higher standards of intervention reporting and enhanced translation of research to clinical practice.

Residual Impact of Previous Injury on Musculoskeletal Characteristics in Special Forces Operators

Background

Musculoskeletal injuries are a significant burden to United States Army Special Operations Forces. The advanced tactical skill level and physical training required of Army Special Operators highlights the need to optimize musculoskeletal characteristics to reduce the likelihood of suffering a recurrent injury.

Purpose

To identify the residual impact of previous injury on musculoskeletal characteristics.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Isokinetic strength of the knee, shoulder, and back and flexibility of the shoulder and hamstrings were assessed as part of a comprehensive human performance protocol, and self-reported musculoskeletal injury history was obtained. Subjects were stratified based on previous history of low back, knee, or shoulder injury, and within-group and between-group comparisons were made for musculoskeletal variables.

Results

Knee injury analysis showed no significant strength or flexibility differences. Shoulder injury analysis found internal rotation strength of the healthy subjects (H) was significantly higher compared with injured (I) and uninjured (U) limbs of the injured group (H, 60.8 ± 11.5 percent body weight [%BW]; I, 54.5 ± 10.5 %BW; U, 55.5 ± 11.3 %BW) (P = .014 [H vs I] and P = .05 [H vs U]). The external rotation/internal rotation strength ratio was significantly lower in the healthy subjects compared with injured and uninjured limbs of the injured group (H, 0.653 ± 0.122; I, 0.724 ± 0.121; U, 0.724 ± 0.124) (P = .026 [H vs I] and P = .018 [H vs U]). Posterior shoulder tightness was significantly different between the injured and uninjured limb of the injured group (I, 111.6° ± 9.4°; U, 114.4° ± 9.3°; P = .008). The back injury analysis found no significant strength differences between the healthy and injured groups.

Conclusion

Few physical differences existed between operators with prior knee or back injury. However, operators with a previous history of shoulder injury demonstrated significantly less shoulder strength than uninjured operators as well as decreased shoulder flexibility on the injured side. All operators, regardless of prior injury, must perform the same tasks; therefore, a targeted injury rehabilitation/human performance training specifically focused on internal rotation strength and tightness of the posterior capsule may help reduce the risk for recurrence of injury. Operators presenting with musculoskeletal asymmetries and/or insufficient strength ratios may be predisposed to musculoskeletal injury.

Clinical Relevance

Specific fitness programs to compensate for deficiencies in strength and flexibility need to be designed that may reduce the risk of injuries in Special Forces Operators.

Reliability and measurement precision of concentric-to-isometric and eccentric-to-isometric knee active joint position sense tests in uninjured physically active adults

OBJECTIVES

Proprioception is important because it is used by the central nervous system to mediate muscle control of joint stability, posture, and movement. Knee active joint position sense (AJPS) is one representation of knee proprioception. The purpose of this study was to establish the intra-tester, inter-session, test-retest reliability of concentric-to-isometric (seated knee extension; prone knee flexion) and eccentric-to-isometric (seated knee flexion; prone knee extension) knee AJPS tests in uninjured adults.

DESIGN

Descriptive.

SETTING

University laboratory.

PARTICIPANTS

Six males, six females (age 26.2 ± 5.7 years; height 171.1 ± 9.6 cm; mass 71.1 ± 16.6 kg).

MAIN OUTCOME MEASURES

Mean absolute error (AE; °); intraclass correlation coefficient (ICC) (2,1); standard error of measurement (SEM; °).

RESULTS

Mean AE ranged from 3.18° to 5.97° across tests. The ICCs and SEMs were: seated knee extension 0.13, 1.3°; prone knee flexion 0.51, 1.2°; seated knee flexion 0.31, 1.7°; prone knee extension 0.87, 1.4°.

CONCLUSIONS

The prone knee flexion and prone knee extension tests demonstrated moderate to good reliability. Prone knee flexion and prone knee extension AJPS tests may be useful in cross-sectional studies estimating how proprioception contributes to knee functional joint stability or prospective studies estimating the role of proprioception in the onset of knee injury.

The Effect of Target Position on the Accuracy of Cervical-Spine-Rotation Active Joint-Position Sense

CONTEXT

The cervical spine can be divided into upper and lower units, each making a different contribution to the magnitude of rotation and proprioception. However, few studies have examined the effect of the cervical-rotation positions on proprioception.

OBJECTIVE

To compare cervical-spine rotation active joint-position sense (AJPS) near midrange of motion (mid-ROM; 30°) and near end-ROM (60°).

DESIGN

Cross-sectional study.

SETTING

Human performance research laboratory.

PARTICIPANTS

53 military helicopter pilots (age 28.4 ± 6.2 y, height 175.3 ± 9.3 cm, weight 80.1 ± 11.8 kg).

MAIN OUTCOME MEASURES

A motion-analysis system was used to record cervical-rotation kinematics. Subjects sat in a chair wearing a headband and blindfold. First, they actively rotated the head right or left to a target position (30°/60°), with real-time verbal cues provided by the tester. Subjects held the target position for 5 s and then returned to the start position. After this, they replicated the target position as closely as possible. Five trials were performed in both directions to both target positions (R30/R60/L30/L60). Order of direction/position was randomized. The difference between target and replicated positions was calculated and defined as absolute error (AE), and the mean of 5 trials was used for analyses. Wilcoxon signed-ranks tests were used to compare AJPS at the different target positions (P < .0125 with Bonferroni adjustments).

RESULTS

End-ROM AEs were significantly more accurate than mid-ROM AEs (P = .001).

CONCLUSION

Cervical-spine-rotation AJPS is more accurate near end-ROM than mid-ROM. Both target positions should be used to examine cervical-spine-rotation AJPS of both the upper and lower units.

Neck proprioception, strength, flexibility, and posture in pilots with and without neck pain history

INTRODUCTION

Neck pain (NP) is common among military helicopter pilots. Older age and more flight-hours have been associated with pilots with a history of NP. However, modifiable neuromuscular and musculoskeletal characteristics such as neck proprioception, strength, flexibility, and posture have rarely been investigated in military helicopter pilots with a history of NP. The purpose of the study was to compare demographics, flight characteristics, physical fitness information, neck proprioception, strength, flexibility, and posture between helicopter pilots with and without a history of NP.

METHODS

A total of 27 Army helicopter pilots with NP in the past 12 mo (pain group) were matched based on age with pilots without a history of NP (nonpain group). All pilots had flown at least 100 h in the past 12 mo and were cleared for flight and physical training. All pilots completed a battery of laboratory testing: neck proprioception, neck and scapular muscular strength, neck active range-of-motion (ROM), forward head and shoulder posture, and pectoralis minor length. Paired t-tests or Wilcoxon tests were used to compare differences between groups.

RESULTS

The pain group had significantly less cervical extension (63.7 +/- 8.5 degrees) and rotation ROM (R rotation: 67.7 +/- 8.8 degrees; L rotation: 67.4 +/- 9.0 degrees) when compared to the nonpain group (extension: 68.3 +/- 7.4 degrees; R rotation: 73.4 +/- 7.4 degrees; L rotation: 72.9 +/- 6.8 degrees). No significant differences were found for other variables.

CONCLUSION

The results demonstrate less neck active ROM in pilots with a history of NP. Operating a helicopter with limited neck ROM or NP may negatively impact flight safety and force readiness. Continued research is warranted.

Single-Leg Balance Impairments Persist in Fully Operational Military Special Forces Operators With a Previous History of Low Back Pain

Background:

Single-leg balance (SLB) can be chronically impaired after low back pain (LBP). Impaired SLB is a risk factor for recurrent LBP and lower extremity injury. In the United States military, the special forces operator (SFO) deploys on high-risk missions under extreme conditions, and impaired SLB can potentially threaten SFO safety and mission success.

Purpose:

To compare SLB in fully operational SFOs with and without a history of LBP. The hypothesis was that SLB deficits would be present in SFOs with a history of LBP.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 226 SFOs were included in this analysis. Comparisons were made between SFOs with and without medical chart documented history of LBP (LBP group [n = 43]: mean age = 31.2 ± 10.3 years, mean height = 177.3 ± 7.2 cm, mean mass = 87.3 ± 11.8 kg; healthy group [n = 183]: mean age = 28.0 ± 6.0 years, mean height = 177.9 ± 6.0 cm, mean mass = 84.9 ± 8.8 kg). Bilateral SLB was tested (eyes open and eyes closed) in both groups using a force plate. The variability in the ground-reaction forces was averaged across 3 trials for each leg for both conditions. Comparisons were made between legs in the LBP and between the LBP and healthy group (α = .05).

Results:

There were significant between-group differences for each leg for both conditions, with the healthy group demonstrating better SLB compared with the LBP group. P values ranged from .01 to .03.

Conclusion:

Impaired SLB persists in SFOs with previously reported LBP. Balance assessments of individuals who report LBP may assist with designing targeted interventions to address potential deficits that may increase the risk of future injury.

Clinical Relevance:

SFOs with a known history of LBP would benefit from examination of SLB and may benefit from balance training to resolve any deficits that may be present to lower the potential risk for future injury.

Enhanced Vascular Responses to Adrenomedullin in Mice Overexpressing Receptor-Activity–Modifying Protein 2

Adrenomedullin (AM) levels are elevated in cardiovascular disease, but little is known of the role of specific receptor components. AM acts via the calcitonin receptor-like receptor (CLR) interacting with a receptor-activity–modifying protein (RAMP). The AM 1 receptor is composed of CLR and RAMP2, and the calcitonin gene–related peptide (CGRP) receptor of CLR and RAMP1, as determined by molecular and cell-based analysis. This study examines the relevance of RAMP2 in vivo. Transgenic (TG) mice that overexpress RAMP2 in smooth muscle were generated. The role of RAMP2 in the regulation of blood pressure and in vascular function was investigated. Basal blood pressure, acute angiotensin II–raised blood pressure, and cardiovascular properties were similar in wild-type (WT) and TG mice. However, the hypotensive effect of IV AM, unlike CGRP, was enhanced in TG mice ( P <0.05), whereas a negative inotropic action was excluded by left-ventricular pressure–volume analysis. In aorta relaxation studies, TG vessels responded in a more sensitive manner to AM (EC 50 , 8.0±1.5 nmol/L) than WT (EC 50 , 17.9±3.6 nmol/L). These responses were attenuated by the AM receptor antagonist, AM 22-52 , such that residual responses were identical in all mice. Remaining relaxations were further inhibited by CGRP receptor antagonists, although neither affected AM responses when given alone. Mesenteric and cutaneous resistance vessels were also more sensitive to AM in TG than WT mice. Thus RAMP2 plays a key role in the sensitivity and potency of AM-induced hypotensive responses via the AM 1 receptor, providing evidence that this receptor is a selective target for novel therapeutic approaches.

Neurological phenotype and synaptic function in mice lacking the CaV1.3 alpha subunit of neuronal L-type voltage-dependent Ca2+ channels

Neuronal L-type calcium channels have been implicated in pain perception and neuronal synaptic plasticity. To investigate this we have examined the effect of disrupting the gene encoding the CaV1.3 (alpha 1D) alpha subunit of L-type Ca2+ channels on neurological function, acute nociceptive behavior, and hippocampal synaptic function in mice. CaV1.3 alpha 1 subunit knockout (CaV1.3 alpha 1(-/-)) mice had relatively normal neurological function with the exception of reduced auditory evoked behavioral responses and lower body weight. Baseline thermal and mechanical thresholds were unaltered in these animals. CaV1.3 alpha 1(-/-) mice were also examined for differences in N-methyl-D-aspartate (NMDA) receptor-dependent (100 Hz tetanization for 1 s) and NMDA receptor-independent (200 Hz in 100 microM DL-2-amino-5-phosphopentanoic acid) long-term potentiation within the CA1 region of the hippocampus. Both NMDA receptor-dependent and NMDA receptor-independent forms of long-term potentiation were expressed normally. Radioligand binding studies revealed that the density of (+)[3H]isradipine binding sites in brain homogenates was reduced by 20-25% in CaV1.3 alpha 1(-/-) mice, without any detectable change in CaV1.2 (alpha 1C) protein levels as detected using Western blot analysis. Taken together these data indicate that following loss of CaV1.3 alpha 1 subunit expression there is sufficient residual activity of other Ca2+ channel subtypes to support NMDA receptor-independent long-term potentiation and some forms of sensory behavior/function.

Gait analysis 6 and 12 months after anterior cruciate ligament reconstruction surgery

Little is known about knee function after anterior cruciate ligament reconstruction in the vital activities of walking and stair use. Gait analysis was done on patients 6 months (n = 8) and 12 months (n = 9) after reconstruction of the anterior cruciate ligament. Paired t tests were used to compare the injured and uninjured knees. During level walking, the patients placed external flexion torques on their injured knees throughout midstance, indicating the absence of quadriceps avoidance gait. The peak external flexion torque (resisted by the knee extensor muscles) placed on the injured knee was significantly less than that of the uninjured knee when ascending stairs (at 12 months, 68.4 and 85.3 N-m in the injured and uninjured knees, respectively) and also when descending stairs (at 12 months, 70.8 and 81.7 N-m in the injured and uninjured knees, respectively). The injured knee produced significantly less power than the uninjured knee when ascending stairs, but this difference was not significant when descending stairs. These findings indicate that asymmetric gait patterns persisted up to 1 year after surgical reconstruction and were more pronounced during stair ascent and descent than in level walking. These results indicate that clinicians should include specific interventions targeted at improving knee function during stair use to restore normal function after anterior cruciate ligament reconstruction.

Tracheostomy: a risk factor for mediastinitis after cardiac operation

BACKGROUND

We studied whether tracheostomy after coronary artery bypass grafting (CABG) is associated with higher incidence of mediastinitis and mortality, and whether shorter intervals between median sternotomy and tracheotomy are associated with higher incidence of mediastinitis.

METHODS

Patients (n = 6,057) undergoing CABG since March 1977 were reviewed. Patients requiring tracheostomy and those developing mediastinitis were identified. Mediastinitis diagnosis required positive culture of mediastinal tissue or fluid.

RESULTS

After CABG, 88 patients had tracheostomy performed (1.45%). Seven patients receiving tracheostomy after developing mediastinitis were excluded. Of the remaining 81 patients, 7 developed mediastinitis (8.6%) compared with 44 of 5,969 (0.7%) who did not require tracheostomy (p < 0.001). Mortality in tracheostomy patients was 24.7% (20 of 81) compared with 5.2% in patients not requiring tracheostomy (316 of 5,969; p < 0.001). Patients not developing mediastinitis had tracheostomy placement an average of 25 days after CABG compared with 18.7 days for those developing mediastinitis (p = 0.141).

CONCLUSIONS

Tracheostomy after CABG is associated with increased incidence of mediastinitis and mortality. In this review, the time interval between CABG and tracheostomy was not predictive of mediastinitis. A larger sample size would be required to be confident that there is no correlation.

A cluster of VanD vancomycin-resistant Enterococcus faecium: molecular characterization and clinical epidemiology

VanD-mediated glycopeptide resistance has been reported for an isolate of Enterococcus faecium, BM4339. Three clinical isolates of vancomycin-resistant E. faecium collected from 3 patients during a 6-week period in 1993 had agar dilution MICs of vancomycin and teicoplanin of 128 and 4 microg/mL, respectively. Polymerase chain reaction (PCR) using degenerate primers complementary to genes encoding d-Ala-d-X ligases yielded a 630-bp product that was similar to the published partial sequence of vanD. By use of inverse PCR, vanD, vanHD, and two partial flanking open-reading frames were sequenced. The deduced amino acid sequence of VanD showed 67% identity with VanA and VanB. vanD appeared to be located on the chromosome and was not transferable to other enterococci. The 3 isolates were indistinguishable by pulsed-field gel electrophoresis and differed from BM4339. No other isolates carrying vanD were found in a subset of 875 recent US isolates of vancomycin-resistant enterococci.

Detection of a streptomycin/spectinomycin adenylyltransferase gene (aadA) in Enterococcus faecalis

Genes encoding streptomycin/spectinomycin adenylyltransferases [ANT(3")(9)] have been reported to exist in gram-negative organisms and Staphylococcus aureus. During a study of high-level aminoglycoside resistance in enterococci, we encountered an isolate of Enterococcus faecalis that was streptomycin resistant but did not appear to contain the 6'-adenylyltransferase gene (aadE) when examined by PCR with specific primers. Phosphocellulose paper binding assays indicated the presence of an ANT(3")(9) enzyme. Streptomycin and spectinomycin MICs of 4,000 and 8,000 microg/ml, respectively, were observed for the isolate. PCR primers corresponding to a highly conserved region of the aadA gene were used to amplify a specific 284-bp product. The product hybridized with a digoxigenin-labeled PCR product from E. coli C600(pHP45Omega) known to contain the aadA gene. The aadA gene was transferred via filter matings from the E. faecalis donor to E. faecalis JH2-2. PCR primers designed for analysis of integrons were used to amplify a 1-kb product containing the aadA gene, which was cloned into the vector pCRII and transformed into Escherichia coli DH5-alpha competent cells. D-Rhodamine dye terminator cycle sequencing was used to determine the gene sequence, which was compared to previously reported sequences of aadA genes. We found the aadA gene in E. faecalis to be identical to the aadA genes reported by Sundstr om et al. for E. coli plasmid R6-5 (L. Sundström, P. Râdström, G. Swedberg, and O. Sköld, Mol. Gen. Genet. 213:191-201, 1988), by Fling et al. for the aadA within transposon Tn7 (M. E. Fling, J. Kopf, and C. Richards, Nucleic Acids Res. 13:7095-7106, 1985), and by Hollingshead and Vapnek for E. coli R538-1 (S. Hollingshead and D. Vapnek, Plasmid 13:17-30, 1985). Previous reports of the presence of the aadA gene in enterococci appear to be erroneous and probably describe an aadE gene, since the isolates were reported to be susceptible to spectinomycin.

Detection and differentiation of vanC-1, vanC-2, and vanC-3 glycopeptide resistance genes in enterococci

The VanC phenotype, as found in Enterococcus gallinarum, E. casseliflavus, and E. flavescens, is characterized by intrinsic low-level resistance to vancomycin. The nucleotide sequences of the vanC-1 gene in E. gallinarum, the vanC-2 gene in E. casseliflavus, and the vanC-3 gene in E. flavescens have been reported, although there is some disagreement as to whether E. flavescens is a legitimate enterococcal species. Previous attempts to differentiate the vanC-2 and vanC-3 genes by PCR analysis have been unsuccessful. The purpose of the present study was to detect and differentiate the three vanC determinants and examine the distribution of these genes in a collection of both typical and atypical enterococci. The 796-bp vanC-1 PCR product was amplified only from E. gallinarum isolates. As expected, due to the extensive homology in the vanC-2 and vanC-3 gene sequences, all of the E. casseliflavus and E. casseliflavus/flavescens isolates produced the 484-bp vanC-2 PCR product, although the E. gallinarum isolates were negative. Only the E. casseliflavus/flavescens isolates produced the 224-bp vanC-3 product. Using the three sets of primers, we were able to detect and distinguish the vanC-1, vanC-2, and vanC-3 genes from both typical and atypical enterococci strains. Antimicrobial susceptibility tests and analysis of genomic DNA by pulsed-field gel electrophoresis were also performed, but the results indicated that they were not able to distinguish among strains possessing the three vanC genotypes.

Characterization of staphylococci with reduced susceptibilities to vancomycin and other glycopeptides

During the last several years a series of staphylococcal isolates that demonstrated reduced susceptibility to vancomycin or other glycopeptides have been reported. We selected 12 isolates of staphylococci for which the vancomycin MICs were > or =4 microg/ml or for which the teicoplanin MICs were > or =8 microg/ml and 24 control strains for which the vancomycin MICs were < or =2 microg/ml or for which the teicoplanin MICs were < or =4 microg/ml to determine the ability of commercial susceptibility testing procedures and vancomycin agar screening methods to detect isolates with reduced glycopeptide susceptibility. By PCR analysis, none of the isolates with decreased glycopeptide susceptibility contained known vancomycin resistance genes. Broth microdilution tests held a full 24 h were best at detecting strains with reduced glycopeptide susceptibility. Disk diffusion did not differentiate the strains inhibited by 8 microg of vancomycin per ml from more susceptible isolates. Most of the isolates with reduced glycopeptide susceptibility were recognized by MicroScan conventional panels and Etest vancomycin strips. Sensititre panels read visually were more variable, although with some of the panels MICs of 8 microg/ml were noted for these isolates. Vitek results were 4 microg/ml for all strains for which the vancomycin MICs were > or =4 microg/ml. Vancomycin MICs on Rapid MicroScan panels were not predictive, giving MICs of either < or =2 or > or =16 microg/ml for these isolates. Commercial brain heart infusion vancomycin agar screening plates containing 6 microg of vancomycin per ml consistently differentiated those strains inhibited by 8 microg/ml from more susceptible strains. Vancomycin-containing media prepared in-house showed occasional growth of susceptible strains, Staphylococcus aureus ATCC 29213, and on occasion, Enterococcus faecalis ATCC 29212. Thus, strains of staphylococci with reduced susceptibility to glycopeptides, such as vancomycin, are best detected in the laboratory by nonautomated quantitative tests incubated for a full 24 h. Furthermore, it appears that commercial vancomycin agar screening plates can be used to detect these isolates.

Molecular characterization and multilaboratory evaluation of Enterococcus faecalis ATCC 51299 for quality control of screening tests for vancomycin and high-level aminoglycoside resistance in enterococci

Studies were conducted to validate the use of Enterococcus faecalis ATCC 51299 (which is vancomycin resistant and resistant to high levels of gentamicin and streptomycin) and E. faecalis ATCC 29212 (which is susceptible to vancomycin and against which gentamicin or streptomycin and cell wall-active agents have synergistic kill activity) as controls in an agar screening test for vancomycin resistance and high-level streptomycin and gentamicin resistance and a broth microdilution screening test for high-level streptomycin and gentamicin resistance. Both organisms performed as expected in these tests and will serve as appropriate controls. However, E. faecalis ATCC 29212 was occasionally noted to produce light growth on the vancomycin screening plate with certain lots of agar. Quality control ranges for disk diffusion tests with disks with large amounts of streptomycin (300 micrograms) and gentamicin (120 micrograms) were established for E. faecalis ATCC 29212; zone limits are 16 to 22 mm for gentamicin and 14 to 19 mm for streptomycin. No zones for inhibition were seen when E. faecalis ATCC 51299 was tested with these high-content disks.

Multilaboratory evaluation of screening methods for detection of high-level aminoglycoside resistance in enterococci. National Committee for Clinical Laboratory Standards Study Group on Enterococci

Since the early 1970s, the synergistic activity of an aminoglycoside with a cell wall-active agent has been predicted by determining the ability of an enterococcus to grow in the presence of high levels of the aminoglycoside (usually > or = 2,000 micrograms/ml). However, a variety of media and concentrations of aminoglycosides has been used for this screening procedure. In the present study, we sought to optimize the agar dilution, broth microdilution, and disk diffusion tests used to detect high-level gentamicin and streptomycin resistance in enterococci. For dilution tests, brain heart infusion agar or broth gave the best growth and performance. For agar dilution, 500 micrograms of gentamicin per ml, 2,000 micrograms of streptomycin per ml, and an inoculum of 1 x 10(6) CFU/ml were optimal, while for broth microdilution, 500 micrograms of gentamicin per ml, 1,000 micrograms of streptomycin per ml, and an inoculum of 5 x 10(5) CFU/ml were best. Growth of more than one colony in the agar dilution test was determined to be the best indicator of high-level resistance. For disk diffusion, Mueller-Hinton agar, 120-micrograms gentamicin disks, and 300-micrograms streptomycin disks with breakpoints of no zone for resistance and > or = 10 mm for susceptibility gave the best sensitivity and specificity if results for strains with zones of 7 to 9 mm are considered inconclusive, indicating that a broth or agar test should be performed to determine susceptibility or resistance.

Possible nosocomial transmission of Pseudomonas cepacia in patients with cystic fibrosis

OBJECTIVE

To determine whether nosocomial transmission of Pseudomonas cepacia occurred at a hospital with endemic P cepacia infection of patients with cystic fibrosis.

DESIGN

Two retrospective case-control studies.

SETTING

A large pediatric cystic fibrosis center.

PARTICIPANTS

To assess risk factors for acquisition of P cepacia, 18 cases, defined as any patient with cystic fibrosis with first documented isolation of P cepacia in 1988 or 1989, were compared with 18 matched P cepacia-negative controls with cystic fibrosis. To assess potential modes of nosocomial P cepacia transmission, 14 cases with a hospitalization(s) between their last P cepacia-negative culture and first P cepacia-positive culture were compared with 14 hospitalized P cepacia-negative controls with cystic fibrosis.

METHODS

Handwiping cultures (N = 68) and selective environmental cultures were performed.

MAIN RESULTS

Cases tended to be more likely than controls to have been hospitalized at the cystic fibrosis center in the 3 months before their first P cepacia-positive culture (P = .08). In addition, cases tended to be more likely than hospitalized controls with cystic fibrosis to have had a P cepacia-positive roommate (P = .06) before becoming colonized with P cepacia organisms. Pseudomonas cepacia was cultured from the hands of two individuals: a P cepacia-colonized patient who had just undergone chest physiotherapy and consequent coughing and the investigator who shook the P cepacia-positive patient's hand after the patient's procedure.

CONCLUSIONS

These results suggest that in this cystic fibrosis center, hospitalization is a risk factor for P cepacia acquisition and that person-to-person transmission of P cepacia may occur in the hospital via hand contact.

Development of a standardized screening method for detection of vancomycin-resistant enterococci

The incidence of vancomycin resistance among enterococci is increasing in the United States and elsewhere in the world, but automated susceptibility testing methods have difficulty detecting resistance expressed by certain strains. The agar screening method described by Willey et al. (B. M. Willey, B. N. Kreiswirth, A. E. Simor, G. Williams, S. R. Scriver, A. Phillips, and D. E. Low, J. Clin. Microbiol. 30:1621-1624, 1992) has been proposed as a reliable method for confirming vancomycin resistance. In this study, we investigated various parameters associated with the agar screening method and, on the basis of the findings, established optimum testing conditions for the method. First, to evaluate media and vancomycin concentrations, one laboratory used Mueller-Hinton and brain heart infusion agars supplemented with 4, 6, and 8 micrograms of vancomycin per ml to test 100 genetically characterized enterococcal strains. On the basis of the results obtained, brain heart infusion agar supplemented with 6 micrograms of vancomycin per ml was selected for further study. Subsequently, eight laboratories used the medium to test both reference and clinical isolates. There was very good performance with the reference strains and, among 158 clinical isolates tested, the method demonstrated sensitivity and specificity of 100% and from 96 to 99%, respectively.

Characterization of glycopeptide-resistant enterococci from U.S. hospitals

We examined 105 clinical isolates of glycopeptide-resistant enterococci collected from 31 U.S. hospitals in 14 states during May 1988 to July 1992. The isolates included 82 Enterococcus faecium, 8 E. faecalis, 6 Enterococcus spp., 5 E. gallinarum, 3 E. casseliflavus, and 1 E. raffinosus. The isolates were categorized into the following four phenotypes of glycopeptide resistance on the basis of their MIC patterns: (i) 70 VanA (vancomycin [Vm] MIC, > or = 64 micrograms/ml; teicoplanin [Tei] MIC, 16 to > or = 128 micrograms/ml), (ii) 26 VanB (Vm MIC, 16 to 1,024 micrograms/ml; Tei MIC, < or = 2 micrograms/ml), (iii) 5 VanC (Vm MIC, 4 to 16 micrograms/ml; Tei MIC, < or = 2 micrograms/ml) in E. gallinarum, and (iv) 3 E. casseliflavus and 1 E. raffinosus isolates for which Vm MICs were 4 to 16 micrograms/ml and Tei MICs were < or = 1 micrograms/ml were called unclassified. Of the 101 isolates with the VanA, VanB, and VanC phenotypes, 99 were confirmed by production of a specific 1,030-, 433-, or 796-bp polymerase chain reaction product, respectively, and hybridization with the respective gene probe. The vanA gene was also detected in the E. raffinosus isolate for which the Vm MIC was 16 micrograms/ml and the Tei MIC was 1 microgram/ml. The vanA gene was located on either a 34- or a 60-kb plasmid in all of the U.S. isolates examined. Pulsed-field gel electrophoresis demonstrated both intrahospital and interhospital diversity among Vmr enterococci in the United States and was more useful than plasmid analysis for epidemiologic studies.

Infections and pseudoinfections due to povidone-iodine solution contaminated with Pseudomonas cepacia

In 1989 we investigated the first instance of Pseudomonas cepacia infections due to intrinsic contamination of a povidone-iodine product. Six patients in a Texas pediatric facility had P. cepacia infection or pseudoinfection (three, peritonitis; one, pseudoperitonitis; and two, pseudobacteremia). Epidemiological studies showed one risk factor for infection of peritoneal fluid with P. cepacia: performance of peritoneal dialysis in the dialysis unit with use of one lot of povidone-iodine later found to be intrinsically contaminated (4/5 vs. 0/16, P = .001). Blood cultures yielded P. cepacia after nurses wiped the tops of blood culture bottles with the povidone-iodine solution before inoculation. P. cepacia was cultured from three povidone-iodine containers used at the hospital and from four containers of the same lot obtained from other health-care facilities in Texas and California. Isolates from patients and the povidone-iodine had similar antibiograms, identical plasmid profiles, and identical DNA banding patterns on the basis of results of ribonucleotide typing. This investigation demonstrates that intrinsic contamination of povidone-iodine solution with P. cepacia can result in infections in addition to colonization and/or pseudoinfection.

Epidemiologic typing of Enterobacter sakazakii in two neonatal nosocomial outbreaks

Two unrelated hospital outbreaks of Enterobacter sakazakii, involving meningitis, bacteremia, and colonization of neonates, were investigated. In each of these outbreaks, E. sakazakii was isolated from both patients and dried infant formula. In previous outbreaks, the source and mode of transmission of E. sakazakii in neonatal infections was not determined. In this study, we used a combination of typing methods (plasmid analysis, antibiograms, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis) to evaluate the isolates from each outbreak as to their relatedness. The typing results differed among outbreaks, but in each one, patient and formula isolates shared the same typing pattern. The only exceptions were disk antibiograms, which often varied among colonies selected from each of the isolates. Plasmid analysis, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis all were effective as epidemiological typing methods for E. sakazakii, especially when used in combination. By using this typing scheme, we have confirmed that E. sakazakii from intrinsically contaminated dried infant formula was the source of neonatal infection.

Three cases of neonatal meningitis caused by Enterobacter sakazakii in powdered milk

Three cases of neonatal infection caused by Enterobacter sakazakii are reported from the Department of Neonatal Intensive Care, the National University Hospital, Reykjavík, Iceland. These infections occurred during a 9-month period in 1986 and 1987. Two of the neonates, who were normal at birth, survived but were left with brain damage. The third, who had Down's syndrome and severe cardiac malformations, died. The same organism was also grown from groin and anal swabs from a healthy neonate. E. sakazakii was not isolated from any environmental sources in the neonatal wards or in the milk kitchen, but it was grown from several lots of the powdered-milk formula used in the hospital. The four E. sakazakii strains isolated from the neonates were indistinguishable from 22 strains grown from the formula. Their biotypes, plasmid DNA profiles, and antibiograms were identical.

DNA hybridization studies of a nucleotide sequence homologous to transposon Tn1545 in the "Minnesota" strain of multiresistant Streptococcus pneumoniae isolated in 1977

Nucleotide sequences homologous to the transposon-specific region and the tetM determinant mediating tetracycline resistance of the multiresistance transposon Tn1545, originating in Streptococcus pneumoniae, were detected by hybridization in the first multiresistant pneumococcus reported in the United States. The sequences were localized to a common 25-kb EcoRI restriction fragment of the chromosome.

Biotyping coagulase-negative staphylococci

The biochemical profiles obtained with Staph-Ident (Analytab Products, Plainview, N.Y.) panels were combined with the results of adherence and synergistic hemolysis tests to define biotypes among 1,064 clinical isolates representing eight species of coagulase-negative staphylococci. The 672 isolates of Staphylococcus epidermidis were aligned in 69 of 144 potential biotypes in our scheme because of 18 different biochemical profiles and the eight physiologic subtypes. Isolates of most other species were in fewer biotypes because of more uniform adherence and synergistic hemolysis data, as well as fewer biochemical profiles. Since adherence and synergistic hemolysis may prove to be related to virulence and pathogenicity, biotyping with these test results would help evaluate the reliability of adherence and synergistic hemolysis as possible indices of the clinical significance of some of these organisms. When the antimicrobial susceptibility and plasmid profiles obtained on two clusters of S. epidermidis isolates were compared with the biotyping results, one cluster was not further differentiated by plasmid profiles, but was by antimicrobial profiles; the other cluster with only two biotypes was further divided into five distinct types by plasmid profiles but was not separated at all by antimicrobial profiles.

A gene probe for TEM type beta-lactamases

A restriction fragment of plasmid pBR322 bearing the TEM-1 beta-lactamase structural gene was electroeluted from agarose gels after digestion with EcoRI and HinfI. The 1-kilobase fragment was 32P-labeled and used to examine genetic relationships with nucleic acids encoding seven other beta-lactamase classes. The probe hybridized only with TEM-2 and OXA-2 class plasmids.